“I am just listening to Frédéric Chopins “Funeral March”, played by Arturo Benedetti Michelangeli. Chopin had the unique talent to combine the most melancholic melodies with some of the most beautiful sounds. His “marche funèbre” is a very good example for this.” says Alexander Binder in Revel In New York interview

For being such a seemingly ordinary vehicle, the wheelbarrow has a surprisingly exciting history. This is especially true in the East, where it became a universal means of transportation for both passengers and goods, even over long distances. 

The Chinese wheelbarrow - which was driven by human labour, beasts of burden and wind power - was of a different design than its European counterpart. By placing a large wheel in the middle of the vehicle instead of a smaller wheel in front, one could easily carry three to six times as much weight than if using a European wheelbarrow.

The one-wheeled vehicle appeared around the time the extensive Ancient Chinese road infrastructure began to disintegrate. Instead of holding on to carts, wagons and wide paved roads, the Chinese turned their focus to a much more easily maintainable network of narrow paths designed for wheelbarrows. The Europeans, faced with similar problems at the time, did not adapt and subsequently lost the option of smooth land transportation for almost one thousand years.

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Transport options over land

Before the arrival of the steam engine, people have always preferred to move cargo over water instead of over land, because it takes much less effort to do so. But whenever this was not possible, there remained essentially three options for transporting goods: carrying them (using aids like a yoke, or none at all), tying them to pack animals (donkeys, mules, horses, camels, goats), or loading them onto a wheeled cart or wagon (which could be pulled by humans or animals).

Carrying stuff was the easiest way to go; there was no need to build roads or vehicles, nor to feed animals. But humans can carry no more than 25 to 40 kg over long distances, which made this a labour-intensive method if many goods had to be transported. Pack animals can take about 50 to 150 kg, but they have to be fed, are slightly more demanding than people in terms of terrain, and they can be stubborn. Pack animals also require one or more people to guide them.

When carrying goods - whether by person or by pack animals - the load is not only moved in the desired direction but it also undergoes an up and down movement with every step. This is a significant waste of energy, especially when transporting heavy goods over long distances. Dragging stuff does not have this drawback, but in that case you have friction to fight. Pulling a wheeled vehicle is therefore the most energy-efficient choice, because the cargo only undergoes a horizontal motion and friction is largely overcome by the wheels. Wheeled carts and wagons, whether powered by animals or people, can take more weight for the same energy input, but this advantage comes at a price; you need to build fairly smooth and level roads, and you need to build a vehicle. If the vehicle is drawn by an animal, the animal needs to be fed.

When all these factors are taken into consideration, the wheelbarrow could be considered the most efficient transport option over land, prior to the Industrial Revolution. It could take a load similar to that of a pack animal, yet it was powered by human labour and not prone to disobedience.

Compared to a two-wheeled cart or a four-wheeled wagon, a wheelbarrow was much cheaper to build because wheel construction was a labour-intensive job. Although the wheelbarrow required a road, a very narrow path (about as wide as the wheel) sufficed, and it could be bumpy. The two handles gave an intimacy of control that made the wheelbarrow very manoeuvrable.

East and West: a very different story

The wheelbarrow tells a very distinct history in both the Western and the Eastern world. Although to this date its origins remain obscure, it is clear that the vehicle played a much larger role in the East than in the West. While in recent years there has surfaced some evidence that the wheelbarrow might have been used on construction sites by the Ancient Greeks at the end of the fifth century BC, there is no mention at all of wheelbarrows in Ancient Rome (although that does not exclude the possibility that they in fact did use them).

The first sound evidence of the wheelbarrow in the Western world only emerged in the early thirteenth century AD. In China, their use is documented extensively from the second century AD onwards - more than a thousand years earlier. It is interesting to note that the wheelbarrow appeared at least 2,000 years later than two-wheeled carts and four-wheeled wagons. 

Handbarrow

When the wheelbarrow finally caught on in Europe, it was used for short distance cargo transport only, notably in construction, mining and agriculture. It was not a road vehicle. In the East, however, the wheelbarrow was also applied to medium and long distance travel, carrying both cargo and passengers. This use - which had no Western counterpart - was only possible because of a difference in the design of the Chinese vehicle. The Western wheelbarrow was very ill-adapted to carry heavy weights over longer distances, whereas the Chinese design excelled at it.

On the European wheelbarrow the wheel was (and is) invariably placed at the furthest forward end of the barrow, so that the weight of the burden is equally distributed between the wheel and the man pushing it. In fact, the wheel substitutes for the front man of the handbarrow or stretcher, the carrying tool that was replaced by the wheelbarrow (illustration on the right).

Superior Chinese design

In the characteristic Chinese design a much larger wheel was (and is) placed in the middle of the wheelbarrow, so that it takes the full weight of the burden with the human operator only guiding the vehicle. In fact, in this design the wheel substitutes for a pack animal. In other words, when the load is 100 kg, the operator of a European wheelbarrow carries a load of 50 kg while the operator of a Chinese wheelbarrow carries nothing. He (or she) only has to push or pull, and steer.

The result was an extremely powerful and agile vehicle. In 1176 AD, the Chinese writer Tsêng Min-Hsing noted enthusiastically:

"The device is so efficient that it can take the place of three men; moreover, it is safe and steady when passing along dangerous places (cliff paths, etcetera). Ways which are as winding as the bowels of a sheep will not defeat it."

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The large central wheel of a Chinese wheelbarrow takes the full weight of the burden with the human operator only guiding the vehicle

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The Chinese wheelbarrow - which was also widely in use in present-day Cambodia, Vietnam and Laos - originally appeared in two basic variants. One was originally termed the "wooden ox" ("mu niu"), which had the shafts projecting in front (so that it was pulled), while the other was termed the "gliding horse" ("liu ma"), which has the shafts projecting behind (so that it was pushed). A combination of both types was also used, being pulled and pushed by two men. From these two basic types, many variations evolved. Later, the Chinese also used western-style wheelbarrows alongside their own design.

Western praise

The characteristic vehicle stupefied Western foreigners who visited China during the early modern period. In "Science and civilization in China", Joseph Needham quotes the Dutch-American merchant Andreas Everardus van Braam Houckgeest, who visited the country in 1797 and gives an excellent description of the contraption:

"Among the carriages employed in this country is a wheelbarrow, singularly constructed, and employed alike for the conveyance of persons and goods. According as it is more or less heavy loaded, it is directed by one or two persons, the one dragging it after him, while the other pushes it forward by the shafts. The wheel, which is very large in proportion to the barrow, is placed in the centre of the part on which the load is laid, so that the whole weight bears upon the axle, and the barrow men support no part of it, but serve merely to move it forward, and keep it in equilibrum."

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A Chinese traveller sits on one side, and thus serves to counter-balance his baggage, which is placed on the other

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"The wheel is as it were cased up in a frame made of laths, and covered over with a thin plank, four or five inches wide. On each side of the barrow is a projection, on which the goods are put, or which serves as a seat for the passengers. A Chinese traveller sits on one side, and thus serves to counter-balance his baggage, which is placed on the other. If his bagage is heavier than himself, it is balanced equally on the two sides, and he seats himself on the board over the wheel, the barrow being purposely contrived to suit such occasions."

Wheelbarrow trains

"The sight of this wheelbarrow thus loaded, was entirely new to me. I could not help remarking its singularity, at the same time that I admired the simplicity of the invention. I even think, that in many cases such a barrow would be found much superior to ours."

The American soil scientist F.H. King shows himself equally impressed in his 1911 publication "Farmers of Forty Centuries":

"We had observed long processions of wheelbarrow men moving from the canals through the streets carrying large loads of [crops] in bundles a foot long and five inches in diameter. These had come from the country on boats each carrying tons of the succulent leaves and stems. We had counted as many as fifty wheelbarrow men passing a given point on the street in quick succession, each carrying 300 to 500 pounds of [crops] and moving so rapidly that it was not easy to keep pace with them, as we learned in following one of the trains during twenty minutes to its destination. During this time not a man in the train haltened or slackened his pace. This same type of vehicle, too, is one of the common means of transporting people, especially Chinese women, and four, six and even eight may be seen riding together, propelled by a single wheelbarrow man."

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This description would not be complete without mentioning the squeaking of the unoiled axle, a nightmare to foreigners, which does not bother the Chinese in the least

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Rudolf Hommel, in his 1937 book "China at work" (based on a 1921 travel through the country), seems to be most intrigued by the ingenuity of the low-tech design, going into technical details:

"While there are many kinds of wheelbarrows, the one shown [here] is typical of them all; the principle always being the same, i.e. one large wheel surrounded by a framework, guarding the upper part of the wheel from contact with merchandise or persons transported. The two long shafts, held at a proper distance from each other by two crosspieces, terminate in the handlebars, and form the basis of the whole vehicle. Into them is mortised the lattice work which surrounds the wheel. On each side a carrying frame is formed by curved bars attached to the main shafts by crosspieces."

Low-tech masterpieces

"The wheel, about 3 feet in diameter, is made entirely of wood and has two iron bands around the hub, and an iron tire. The axle is made of some very strong wood. From the frame of the wheelbarrow two pieces extend downward with the bearing holes for the axle. This looks rather precarious, and yet these pieces stand up splendidly under the heavy strain of immense loads and the considerable bumping over the miserable roads. These wheelbarrows are masterpieces of joinery and special care is bestowed on the selection of the best grades of hard wood for all parts. This description would not be complete without mentioning the squeaking of the unoiled axle, a nightmare to foreigners, which does not bother the Chinese in the least."

Just as other Western observers, Hommel watched the vehicles pass by in admiration:

"Besides transporting goods with these wheelbarrows, the Chinese use them also for passengers. I have seen as many as six people on them, three sitting on each side with their feet dangling down. If only one person is conveyed the driver balances the wheelbarrow skilfully with the wheel tilted at a considerable angle from the vertical. If a peasant wants to take a pig to the market, he saves himself all the trouble of guiding the recalcitrant beast, by tying it upon the wheelbarrow and wheeling it to the market."

Mobile forts

As so many other innovative technologies, the Chinese wheelbarrow was orginally developed for military purposes. The first records mention its use for supplying food to the army. The wheelbarrow gave the Chinese armies such an advantage in moving goods that it was kept secret - early Chinese writings talk about wheelbarrows in code. True to its origin, the wheelbarrow remained in use for military operations, though not only to supply food to soldiers. In 1176, Tsêng Min-Hsing alluded to the military use of the wheelbarrow in forming protective layers.

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The Ancient Chinese used their wheelbarrows as a defence against the onslaught of cavalry, a tactical system that remained in use during later times using two-wheeled carts

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His words are quoted by Joseph Needham:

"Not only is it useful for transporting army rations, but at need it can be employed as a defensive obstruction against cavalry. Since the digging of trenches and moats, and the building of forts, take time, the wheelbarrows can be deployed round the perimeter so that the enemy's horses cannot easily pass over. This kind of vehicle can readily go forward and withdraw, and can be used for any purpose. It might well be called a 'mobile fort'."

Watching the Vietnamese wheelbarrow pictured above, the defensive use of the vehicle is easy to imagine. According to Needham, it was the Chinese with their wheelbarrows who pioneered the use of 'laagers' or 'mobile forts' as a defence against the onslaught of cavalry, a tactical system that remained in use during later times using two-wheeled carts.

Animal traction

A remarkable feature of the Chinese wheelbarrow was the combined use of human and animal traction, which became common from an early date on. This practice can be seen in a 1126 painting by Chang Tsê-Tuan, which is described by Joseph Needham:

"The painting depicts the popular life of the capital Khaifêng at the time of the spring festival. Many wheelbarrows are moving or stationary in the streets of the city. All but one have the large central wheel and some are very heavily laden. During the loading and unloading the wheelbarrows rest on the side-legs. One is being pushed by a single man, and in all cases the porter steadies the vehicle by the shafts behind, while traction is effected either by one man in shafts and one mule or donkey with collar-harness and traces, or by two animals side by side similarly attached."

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The use of auxiliary power from animals and wind (the two were sometimes combined) made it possible to design larger wheelbarrows that could take more cargo

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The latter configuration is shown again in a picture in the Thien Kung Khai Wu (1637), where in the text we read:

"The northern one-wheeled barrow (tu yuan chhê) is pushed by one man from behind, with (one or more) donkeys pulling it from the front; it is hired by those who dislike riding (on horseback). The travellers sit on opposite sides to balance it, and a mat roof shields them from sun and wind. This kind of conveyance goes as far north as Chhang-an and Chi-ning, and also comes to the capital. When not carrying passengers these barrows will take as much as 4 or 5 tan of goods [about 6 cwt or 300 kg]. The one-wheeled barrow (tu lun thui chhe) of the south is also pushed by one man (but without animal aid), and carries only 2 tan. When it meets pot-holes (in the road) it has to stop; in any case it seldom goes more than 100 li [50 km]." 

Wind powered wheelbarrows

An even more surprising method to augment human power in moving the wheelbarrow was the use of sails. The date of the introduction of the sailing wheelbarrow is unknown, but Joseph Needham notes that this contraption (the chia fan chhê) was still widely used in China at the time of writing (1965), notably in Honan and in the coastal provinces such as Shantung. Rudolf Hommel and F.H. King also spotted and described the vehicles. While some sails were very simple pieces of cloth, others were perfect miniatures of the ones used on a junk (a Chinese sailboat), easily adjustable by the driver.

The use of auxiliary power from animals and wind (the two were sometimes combined) made it possible to design larger wheelbarrows that could take more cargo. Again, it is worthy to quote Andreas Everardus van Braam Houckgeest, writing in 1797:

"Near the southern border of Shantung one finds a kind of wheelbarrow much larger than that which I have been describing, and drawn by a horse or a mule. But judge of my surprise when today I saw a whole fleet of wheelbarrows of the same size. I say, with deliberation, a fleet, for each of them had a sail, mounted on a small mast exactly fixed in a socket arranged at the forward end of the barrow."

"The sail, made of matting, or more often of cloth, is five or six feet [1.5 to 2 m] high, and three or four feet broad,, with stays, sheets, and halyards, just as on a Chinese ship. The sheets join the shafts of the wheelbarrow and can thus be manipulated by the man in charge."

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While some sails were very simple pieces of cloth, others were perfect miniatures of the ones used on a junk (a Chinese sailboat), easily adjustable by the driver

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"One had to grant the apparatus was not a freak, but an arrangement by which, with a favourable wind, the wheelbarrow porters could be greatly assisted. Otherwise such a complicated thing would have been only a bizarre curiosity. I could not help admiring the combination, and was filled with sincere pleasure in seeing twenty or so of these sailing-wheelbarrows setting their course one behind the other."

Wheelbarrows on rails

The Chinese wheelbarrow kept evolving even after the arrival of the Industrial evolution, adapting modern materials and wheels. Another noteworthy example of this is the so-called 'piepkar', which showed up on the island of Billiton at the coast of Sumatra at the turn of the twentieth century. There, a Dutch tin mining company was faced with very bad roads. The solution? A great example of combining Eastern and Western knowledge; wheelbarrows equipped with very narrow wheels, guided by iron rails. The technology - which was in use from the 1880s to around 1920 - reminds of the horse-drawn rail cars that became popular in Western cities at the time.

The decay of the Chinese road infrastructure

The importance of the Chinese wheelbarrow can only be understood in the context of the Chinese transportation network. Prior to the third century AD, China had an extensive and well-maintained road network suited for animal powered carts and wagons. It was only surpassed in length by the Ancient Roman road network. The Chinese road infrastructure attained a total length of about 25,000 miles (40,000 km), compared to almost 50,000 miles (80,000 km) for the Roman system.

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The importance of the Chinese wheelbarrow can only be understood in the context of the Chinese transportation network

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The Chinese and Roman road systems were built (independently) over the course of five centuries during the same period in history. Curiously, due to (unrelated) political reasons, both systems also started to disintegrate side by side from the third century AD onwards, and herein lies the explanation for the success of the Chinese wheelbarrow. As we have seen, the one-wheeled vehicle appeared during this period, and this is no coincidence. Increasingly, it was the only vehicle that could be operated on the deteriorating road network. As F.H. King observed:  "For adaptability to the worst road conditions no vehicle equals the wheelbarrow, progressing by one wheel and two feet".

In 1937, Rudolf Hommel goes on complaining about the Chinese roads:

"In olden times, excellent wide roads were in existence in China, suitable for chariots, coaches, and wagons of many descriptions. Present-day conditions show a different picture, especially in Southern and Central China where the two-wheeled cart is not known. The splendid roads are gone, and in their place, we find only narrow paths, scarcely wide enough for foot passengers and wheelbarrows. The two-wheeled cart survived only in North China under the sway of the court of Peking, where the important business of victualizing the capital was sufficient urge to keep up the roads."

"The Chinese peasant, ever intent to gain more ground for the cultivation of his crops, has gradually reduced the width of former highways, unhampered by a watchful government. In fact, the greedy officials winked at such encroachments, as long as they have been thereby enabled to exact increased contributions in taxes from the hardworking peasants. It is only within the last five years that an extensive program of road building has been carried out."

Pathways designed for wheelbarrows

However, it seems that Rudolf Hommel got it wrong, and was looking at the Chinese roads with a Western bias. Joseph Needham tells a more positive story, noting that the network of wide roads was gradually replaced by an informal, low-tech infrastructure that was not less ingenious than the wheelbarrows that operated on it (see his pictures on the right and below). The Chinese answer to a decaying road infrastructure went much further than the adaptation of their vehicles:

"In many periods the government was interested primarily, and sometimes exclusively, in those roads and water-ways which were significant for tax-grain transportation and the conveyance of official messages. The upkeep of a multitude of local roads and paved pathways devolved, therefore, upon the people themselves, acting in their co-operative capacity under village elders and small-town worthies. In this context, religious associations, such as the Taoists Yellow Turbans about 180 AD, later so politically important, or the Buddhist fraternities afterwards, played a significant part. Making good roads was nothing less than a pious duty."

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The network of wide roads was gradually replaced by an informal, low-tech infrastructure that was not less ingenious than the wheelbarrows that operated on it

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"Thus in the course of time, quite apart from the Ancient and medieval imperial highways, China's landscape became shot through with millions of miles of well-paved paths, suitable chiefly for pedestrians, porters with carrying poles, pushers of wheelbarrows, and men carrying litters. Rough unpaved cart-tracks predominated only in the Eastern plains. Those who, like the author, have followed these paved ways past woods and rice-fields for many a mile cannot think of them without intense nostalgia. There was a long tradition of such privately initiated roads going back to the Han or even earlier, and their total mileage far outstripped that of the government main roads as the ages passed."

Interestingly, the modern, twentieth-century road network that appeared in China, and that Hommel was alluding to in 1937, did not immediately gave way to the automobile, but to another low-tech vehicle that is a worthy competitor for the wheelbarrow: the bicycle, a product of the Industrial Revolution that is even more efficient. It will probably take us (and the 21st-century Chinese) another few decades before we realise how smart the Chinese transport infrastructure was.

The decay of the Western road infrastructure

The use of wheelbarrows in combination with specially designed narrow pathways made land transportation in China considerably more efficient than in Europe for a period of almost 1,500 years. Today, critcism on the omnipresent automobile is often ridiculed by saying that we cannot go back to horses and carts, without realizing that the combination of horses and carts is far from evident and not as low-tech as it seems. History clearly shows that an extensive road infrastructure is a very vulnerable thing.

Europe was also left with a deteriorating road network after the demise of the Roman Empire, though the Europeans could buy some time. Because it was sturdier (using piles of stone and concrete rather than the early form of asphalt applied by the Chinese), the Roman road infrastructure remained relatively useful until about the 11th century AD, after which it was largely abandoned. But even before that time, the destruction of bridges and road facilities by the barbarians - or by the locals in order to defend themselves against the barbarians - gradually dimished its usefulness. Lack of maintenance and the plundering of paving stone did the rest. Moreover, the appearance of new towns and capitals (such as Paris) required new routes that did not always coincide with the existing Roman roads.

Contrary to the Chinese, the Europeans did not develop a new vehicle and appropriate infrastructure of paths to make up for the loss of the Ancient highways. New roads appeared during the economic revival of the late Middle Ages, but these were not paved or hardened in any other way. This made them at best inefficient in good weather and nearly impassable when (and after) it rained. Furthermore, because of the absence of foundations, soil erosion caused by heavy rains could wash entire roads away. As a result, the use of carts and wagons all but disappeared in medieval Europe, while nothing else came in place. For people, the options of land transportation again became limited to walking or - only for the rich - horseback riding.

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In most European countries, smooth wheeled traffic only made a comeback during the nineteenth century

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Cargo was most often transported by pack animals (mostly donkeys and mules, sometimes horses), or simply by carrying it. With the exception of England, where wheeled traffic resurged from as early as the 14th century in some places, and France, where some sturdier roads (unpaved but with foundations) appeared in some regions during the late 16th century, smooth operating wheeled traffic only made a comeback in Europe during the nineteenth century - at the same time as the first railroads appeared.

Ox drawn carts

Carts and wagons drawn by oxen remained in use throughout the centuries in Europe, for heavy or large-sized loads that could not be transported by rivers or by sea. However, road conditions often required large spans of oxen, which made wheeled transportation of heavy loads ridiculously expensive and limited to very short distances. Because of friction, the nature of a road surface greatly determines how efficient wheeled transport will be. In "Energy in world history", Vaclac Smil writes: "On a smooth, hard, dry road, a force of only about 30 kg is needed to wheel a 1 tonne load. A loose, gravelly surface may easily call for five times as much draft. On sandy or muddy roads the multiple can be seven to ten times higher."

This had important consequences, as we have seen in the article about the pre-industrial use of fossil fuels. Many countries could not capitalize on most of their energy resources, be it wood or peat or coal, because transporting them over land took more time and energy (in terms of animal feed) than they could afford. If they would have been aware of the Chinese wheelbarrow, the Europeans could have followed a similar strategy as the Chinese, using their limited resources to construct and maintain smooth but narrow pathways (and bridges) while downsizing their vehicles. As was noted in several of the historical sources mentioned above, the Chinese wheelbarrow, aided by a second man, an animal, or wind power, could transport up to 300 kg of cargo. This was almost as much as the maximum allowed cargo for horse and ox drawn carts in Ancient Rome (326 kg and 490 kg respectively).

Lessons for the future

Of course, it was not only the wheelbarrow that kept Chinese communication running after the second century AD. At least as important was the impressive network of artificial canals that complemented it. This infrastructure became ever more important after the detoriation of the road network. For example, the Grand Canal, which ran from Hangzhou to Bejing over a distance of 1800 km, was completed in 1327 after 700 years of digging.

In Europe, the first (relatively modest) canals were only built during the 16th century, and most of them only appeared in the eighteenth and nineteenth centuries. The Chinese wheelbarrow alone could not have given Europe an equally effective transport infrastructure as the Chinese, but there is no doubt that it could have made life in medieval Europe a great deal easier.

The story of the Chinese wheelbarrow also teaches us an obvious lesson for the future. While many of us today are not even prepared to change their limousine for a small car, let alone their automobile for a bicycle, we forget that neither one of these vehicles can function without suited roads. Building and maintaining roads is very hard work, and history shows that it is far from evident to keep up with it.

In this regard, it is important to keep in mind that we won't be as lucky as the medieval Europeans who inherited one of the best and most durable road networks in the world. Our road infrastructure - mostly based on asphalt - is more similar to that of the Ancient Chinese and will disintegrate at a much faster rate if we lose our ability to maintain it. The Chinese wheelbarrow - and with it many other forgotten low-tech transportation options - might one day come in very handy again.

Kris De Decker (edited by Shameez Joubert)

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Sources:

• "Science and Civilisation in China, Volume 4: Physics and Physical Technology, Part 2, Mechanical Engineering", Joseph Needham, 1965 (the wheelbarrow)
• "Science and Civilisation in China, Volume 4: Physics and Physical Technology, Part 3: Civil engineering and nautics", Joseph Needham, 1971 (the road network)
• "Hommel: China at Work", Rudolf P. Hommel, 1937
• "Farmers of Forty Centuries, or, permanent agriculture in China, Korea and Japan", F.H. King, 1911
• "The medieval wheelbarrow", Andrea L. Matthies, in "Technology and Culture", Vol. 32, No.2, April 1991
• "The origins of the wheelbarrow", M.J.T. Lewis, in "Technology and Culture", Vol.35, No.3, July 1994
• "Roads and pavements in France", Alfred Perkens Rockwell, 1895
• "Voyager au Moyen Age", Jean Verdon, 2007 (original edition 1998)
• "Histoire générale des techniques" (Tome I / Tome II), Maurice Dumas, 1962
• "Horse hauling: a revolution in vehicle transport in 12th and 13th century England", John Langdon, 1984
• "A social and economic history of medieval Europe", Gerald Hodgett, 1972
• "Science and Technology in Medieval European Life", Jeffrey R. Wigelsworth, 2006
• "Medieval sourcebook: Richer of Rheims: Journey to Chartres, 10th century", Michael Markowski (webpage)
• "Inland transportation in England during the fourteenth century", J.F. Williard, 1926
• "The use of carts in the fourteenth century", J.F. Williard, 1932
• "Energy In World History", Vaclac Smil, 1994
• "The Subterranean Forest", Rolf Pieter Sieferle, 2010
• Coming home with riches: the wheelbarrow as an auspicious motif in popular Chinese prints, Antje Richter, 2004
• The wheelbarrow, Engines of our ingenuity, John Lienhard
• Institut d'Asie Orientale: pictures (overview).
• Lantern slide collection, Art, Architecture and Engineering Library.

More low-tech transportation:

• Aerial ropeways: automatic cargo transport for a bargain
• Wind powered vehicles
• Trolley canal boats
• Wood gas cars: firewood in the fuel tank
• Gas bag vehicles
• The velomobile: high-tech bike or low-tech car?
• Piston-powered aircraft
• The status quo of electric cars: better batteries, same range
• Cars, out of the way
• Water powered cable trains
• Get wired (again): trolleybuses and trolleytrucks
• Electric road trains in Germany
• Cargo ships, then and now
• The age of speed: how to reduce global fuel consumption by 75 percent
• Life without airplanes: from London to New York in 3 days and 12 hours
• A world without trucks: underground freight networks
• Low-tech cars

More articles related to Chinese technology:

• Recycling animal and human dung is the key to sustainable farming
• Lost knowledge: ropes and knots
• Boat mills: water powered, floating factories
• Medieval smokestacks: fossil fuels in pre-industrial times

Main page.

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Followed shortly by Roboticist Robert Finkelstein saying he thinks “the probability is virtually one, a certainty, that machines will be as intelligent as people, that we will have intelligent robots, that robots will be ubiquitous”. And that this Artificial Intelligence (AI) will happen in our lifetimes.

Experts often underestimate the difficulty of certain feats, and AI certainly has been one in the past, but more and more it seems what computer programs achieve are indeed the initial steps to real AI. Primitive cognitive processes that allow for stable walking, achieving goals… evolving. And with technological evolution so much faster than biological evolution the predictions of 2030-2050 seem rational. In other words, a good idea or not, humanity is entering the Science Fiction realm of machines that are smart.

Wood gas cars were not the only answer to the limited supply of gasoline in World War One and Two. An even more cumbersome alternative came in the form of the gas bag vehicle.

The old-timers on these pictures are not moving furniture or an oversized load. What can be seen on the roof is the fuel tank of the vehicle - a balloon filled with uncompressed gas.

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Gas bag vehicles were built during World War One and (especially) World War Two in France, the Netherlands, Germany and England as an improvised solution to the shortage of gasoline. Apart from automobiles, buses and trucks were also equipped with the technology. The vehicles consumed 'town gas' or 'street gas', a by-product of the process of turning coal into cokes (which are used to make iron).

Today, vehicles powered by compressed natural gas (CNG) or liquified petroleum gas (LPG) are quite practical. The fuel tank needs to be roughly twice as big as a gasoline fuel tank in order to get the same range. But the fuel used for gas bag vehicles during the World Wars was generally not compressed and had a much lower energy density than LPG or CNG. To replace one litre of gasoline, two to three cubic metres of gas was needed.

The only way to get a somewhat practical range, was to use an extremely large 'fuel tank'. Buses were better suited for this than automobiles - they had a full-length gas storage bag on a roof rack. It could be enclosed in a streamlined fairing but most often it was not.

Private automobiles were equipped with a wooden framework which was fastened to the roof and the reinforced bumpers of the vehicle. It was hard to overlook a gas bag vehicle passing along.

The Dutch old-timer on the pictures above carried a gas storage bag of 13 cubic metres, an installation that gave it a range of approximately 50 km (30 miles) at an energy consumption of 13 litres per km (22 mpg). The aerodynamics of gas bag automobiles were disastrous, so fuel economy was far from optimal.

Easy repair

Witnesses to the vehicle passing by could easily see how much fuel was left: the gas bag was fully inflated at the start of a trip, and it deflated with every mile that was driven.

The gas storage bags were made of silk or other fabrics, soaked in rubber (Zodiac was one of the manufacturers). These bags were (and are) much cheaper and easier to build than metal tanks. They could also be repaired in a similar way to bicycle tyres. The bag was anchored to the roof using rings and straps. Some gas bag vehicles could operate alternatively on gas or gasoline. Switching between the two options could be controlled from inside the vehicle.

Compressed gas

Although it was technically possible to compress town gas or street gas, this did not happen because of two reasons. Carbon monoxide, one of the components of town gas and street gas, disintegrates quickly when compressed, while hydrogen gas, another component, leaks away through steel tanks when it is compressed. 

The only exception was the use of  gas cylinders in France during World War Two (picture above), allowing for a smaller fuel tank or a better range. Natural gas was used in this case, which could be compressed without the drawbacks of compressing town gas. However, this configuration turned out to be more expensive and more dangerous.

No smoking

It will not surprise anyone that gas bag vehicles had their risks. One obvious risk was fire, which could cause a gas explosion. As a result, people waiting for the bus were urged not to smoke (See pictures: "Autobus-Haltestelle" = "bus stop" & "Rauchen verboten" = "smoking prohibited").

Bridges

Another risk were bridges and other overhead obstacles. The driver needed to know the exact height of his vehicle and of the bridges that he planned to drive underneath.

Excessive speeds were not a good idea either. It was advised not to surpass a speed of 50 km/h (30 mph), not only to maintain a decent range but also to make sure that the fuel tank would not fly off the vehicle. Strong side winds could present hazardous situations, too. Gas bag vehicles also suffered from carburator fires, loud bangs and engine damage.

Gas bag buses could still be seen in China in the 1990s, notably in the municipality of Chongqing where they were developed in peace time as a cheap public transportation option.

Edited by Deva Lee. Thanks to Dutch John.

Sources:

• http://www.amt.nl/web/Archief/tonen-archief/1941-Rijden-op-gas-uit-een-ballon-1941-2.htm
• http://www.fortunecity.com/uproar/picture/717/BUESSING/1933/gas.htm
• http://news.webshots.com/album/558005684iBwMrL?start=0
• http://www.historycooperative.org/cgi-bin/justtop.cgi?act=justtop&url=http://www.historycooperative.org/journals/eh/11.4/pearson.html
• http://www.edinphoto.org.uk/0_street_w/0_street_views_-_waverley_bridge_gas_bag_bus_ed_s_1900_049.htm
• http://www.traction-avant.com/forumsn/viewtopic.php?id=5528
• http://factoidz.com/the-gas-bag-bus-weird-invention-1-of-many-strange-technologies/
• http://blog.modernmechanix.com/2007/10/13/gas-bag-on-roof-holds-bus-fuel/
• http://www.parisenimages.fr/fr/popup-photo.html?photo=532-1
• http://www.britishpathe.com/record.php?id=74804 (video)
• http://www.youtube.com/watch?v=6iL_SUpIMsQ (video)

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The history of energy use in human civilisation is generally summarised as follows: from Antiquity until the start of the Industrial Revolution, people made use of the manual labour of both animals and humans, as well as biomass, sun, water and wind.

Next, all these renewable energy sources were replaced by fossil fuels: first coal, and later oil and gas. Uranium completed the picture in the second half of the twentieth century.

While this historical summary is basically correct, there were some - rather important - exceptions. Almost all of the leading economies in Western Europe during the last millenium relied on a large-scale use of fossil fuels such as peat and coal.

Illustration: peat fuelled glass manufacturing in the Netherlands, 1700s.

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Our romantic image of the Middle Ages and Renaissance as a paradise of renewable technologies results largely because of our failure to distinguish between thermal and kinetic energy.

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Before we delve into the pre-industrial history of fossil fuels, it is important to note the difference between thermal energy (heat) and kinetic energy (motion). For the greater part of history, wind, water and muscle power could provide only kinetic energy. This was the kind of energy required to grind grain, saw wood, or set sailboats in motion. For centuries, wood (and charcoal made of wood) was the only source of thermal energy in Europe, apart from the use of direct solar energy for low-temperature processes like the drying of mud bricks and food crops. Wood or charcoal were required for activities such as heating buildings, cooking food, producing building materials (such as bricks, tile, cement, lime and plaster), manufacturing glass and paper, forging iron or producing dyes and soaps. At the same time, wood was the main construction material for buildings, ships, bridges, mills, piers, wharves, cranes, winches, mine shafts, vehicles, barrels, furniture and tools.

The invention of the steam engine in the 18th century meant that thermal energy could be converted into kinetic energy: the heat generated by the burning of coal was used to power machines and vehicles. Likewise, the arrival of electricity in the 19th century allowed kinetic energy to be converted into thermal energy: a windmill, for instance, could be used to drive a generator that delivers energy to an electric oven, or heater. (Kinetic energy could produce heat by friction, for example in windmill gears, but this was mostly wasted).

These days, it is self-evident that both types of energy can be converted to one another (with considerable efficiency losses), but for most of human history kinetic energy and heat energy were entirely different and were treated separately. Then, just as now, thermal energy was much more important than kinetic energy.

Urban revival

The Romans - who fuelled practically all their mechanical activities with slave labour - deforested large parts of Europe in their hunger for thermal energy and construction materials. When their empire collapsed, forests recovered during the half millenium that is termed the Dark Ages. But at the beginning of the second millenium AD, Europe became the setting of an urban revival. Between 500 and 1000 AD, some important agricultural innovations occured, including improved ploughs, the triennal rotation of crops, the horse collar, and the horse shoe.

These technologies enabled a larger population and higher food surplus: more food could be supplied with less labour, which further aided the growth of cities in which people could do things other than working the land. The invention of the printing press, for example, further increased the demand for wood. Similarly, building gothic cathedrals required tonnes of materials, raising thermal energy use.

Urbanisation thus went hand in hand with increased industrial acitivity. Also, medieval industrial processes were less efficient than similar processes today. For example: up to 20 kg of charcoal (with an energy content of 600 MJ) was used to produce 1 kg of iron (compared to 20-25 MJ/kg today). Urbanisation and industrialisation increased rapidly between 1100 and 1300, which again resulted in widespread deforestation. 

Windmills are only half of the story

Our romantic image of the Middle Ages and Renaissance as a paradise of renewable technologies results largely because of our failure to distinguish between thermal and kinetic energy. The Dutch and the Flemish, who dominated the Western European economy from about 1100 to 1700, are famous for their impressive use of wind technology, which took off in the 1100s.

The most spectacular use of windmills appeared in Holland from the late 1500s (16th century) onwards. There, the Dutch applied wind power to a wide range of industrial processes, including paper production, wood sawing, glass polishing and cement production. (See the article: "Wind powered factories: the history and future of the industrial windmill").

The industrial windmill was a marvel of pre-industrial technology, but it explains only partly why Holland became the most important economic power in the world during the 17th century. While sustainable providers of power, windmills could only deliver kinetic energy. To give just one example: you can use wind power to polish glass, but you can't make glass using a windmill. For that, you need thermal energy. And in pre-industrial times, as the history books tell us, the only way to reach high temperatures was to burn wood.

One problem, though: virtually all forests in the region had long vanished by the 1600s. Yet, during the Golden Age of the Netherlands, the Dutch not only made glass, they also produced bricks, tiles, ceramics and clay pipes, they refined salt and sugar, bleached linen, boiled soap, brewed beer, distilled spirits and baked bread. All these processes were based on a massive input of thermal energy.

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While peat is classified by the IPCC as a renewable fuel, this is highly debatable. It takes at least 3000 years for a peat layer of 3 m to return to its original size.

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Moreover, the Dutch produced much more than needed for domestic consumption. They became the largest European exporters of many of the above-mentioned industrially manufactured products. On a more modest scale, a similar production boom had happened in Flanders a few centuries earlier, in which an energy-intensive industry appeared in the near total absence of wood reserves. So how did the Dutch and the Flemish achieve this? By mining peat on a truly massive scale.

What is peat?

An intermediate step in the formation of coal, peat forms when plant material, usually in marshy areas, does not decay fully because of a lack of oxygen. This semicarbonised fuel can be found near the earth's surface in layers of up to 5 metres thick.

The energy density of dried and pressed peat - known as "turf" - is about 15 to 17 MJ per kg, which is similar to the energy density of dried wood (15 to 18 MJ/kg) but lower than that of coal (24 MJ/kg) or charcoal (up to 29 MJ/kg). However, it is a bulkier fuel than wood: 1m3 of coal provides 6 times as much heat as 1m3 of turf, for instance.

Turf is still used today in some countries, notably in Ireland, Finland and Russia, where it is burned in power plants and used for domestic heating. While peat is classified by the IPCC as a renewable fuel, this is highly debatable. Peat is renewed at a rate of about 1 mm per year at most, and so it takes at least 3000 years for a peat layer of 3 m to return to its original size - and only if the land is not disturbed in that time. In addition, the mining of peat has a very large impact on the landscape, as we shall see, while the burning of turf produces slightly more CO2-emissions than coal for the same energy content. The only advantage it has over coal is that it produces less smoke and has a lower sulfur content, and thus produces less air pollution than coal.  

How to dig peat

In pre-industrial times, peat was dug out using very simple tools. Before being cut, the peat was often partially dehydrated by digging drainage trenches on its surface. Next, the land was stripped of its vegetation and the peat sods were cut up vertically to the required size.

The following step was to cut out the peat sods horizontally, after which they were loaded onto wheelbarrows and transported to a nearby field. There, they were laid out or stacked up vertically in a formation for drying. It took six to eight weeks for the peat sods to become dry enough to be used as fuel, after which they were beaten or trodden to make them more compact. During the drying process in the field, the peat sods were turned regularly. Finally, the peat (now called turf) was loaded in baskets and carried to the farm or the market.

Mining peat was a seasonal activity that took about 3 months per year, from late spring to early summer. Starting production earlier than April was risky because frost could damage the drying peat. Digging peat in summer was equally risky because there was a chance that it would not be dry enough following a cold and wet season. Likewise, a very hot summer could make the peat useless if it was not taken away from the drying field quickly enough - it would then be dispersed by the wind.

You could thus argue that peat has the disadvantages of both a fossil fuel and a renewable fuel, without any of the benefits. Like other better known fossil fuels, it is a non-renewable energy source that produces large amounts of CO2, yet it has an energy density that is much lower than other fossil fuels. On the other hand, peat digging is a seasonal activity with a "harvest" that may fail because of the weather. And yet, because they had no other choice, the Dutch and the Flemish built their entire economy around it.

The evolution of peat production 

The evolution of peat production was eerily similar to the mining of fossil fuels today. When the easiest accessible reserves were exhausted, the peat diggers developed new technologies and methods to mine harder-to-reach resources at an ever increasing financial and environmental cost. We do not have much detailed knowledge about peat production in Flanders and Brabant, because few written records from the late Middle Ages remain. However, the history of peat production in the present-day Netherlands is relatively well documented.

Bruges, Antwerp, Amsterdam

The urban revival of the late Middle Ages started in Northern Italy, where the dominating merchant cities were Venice, Milan, Genoa and Florence. However, around 1100 a second urban core developed east of the North Sea, a region that would become known as the "Low Countries" from the 15th century onwards. This region would soon rival the economic power of the Italian cities, and become the leading economic and industrial centre in Europe from about 1500 to 1700.

The cities of Bruges, Ghent and Ypres in the province of Flanders (today a portion of Belgium) were the first to develop. Bruges, in particular, became an economic powerhouse due to its position in international trade, finance and cloth production. In 1350, Bruges and Ghent boasted a population of 90,000 and 57,000 inhabitants respectively (compared to 1,000 in Amsterdam, for instance). The picture shows the Bruges town hall, built in 1376. (Picture by Pantchoa).

Around 1500, economic power shifted to the cities of Antwerp, Brussels and Leuven (today all in Belgium) in the province of Brabant. Antwerp became the economic centre of the Western world, a position it would maintain until the end of the 1500s (16th century). By 1550, Antwerp had 90,000 inhabitants, up from 40,000 in 1500, which made it the second largest city in Europe, North of the Alps, after Paris.

In 1580, the Low Countries, then under Spanish rule, were divided into two. The seven provinces in the South North revolted against the Spanish and formed a new state, the Dutch Republic (the present-day Netherlands). As a result of the subsequent chaos in the Southern provinces (present-day Belgium), the city of Antwerp lost its leading role and power shifted rapidly to the Dutch province of Holland, where the capital of Amsterdam now became the European centre of economic and industrial activity. It would remain so until the end of the 17th century.

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When the easiest accessible reserves were exhausted, the peat diggers developed new technologies and methods to mine harder-to-reach resources at an ever increasing financial and environmental cost.

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Peat mining from 1100 to 1500

Large-scale peat digging started in the coastal area of Flanders and northeast of Antwerp in the 1100s and 1200s respectively. The activity was largely aimed at supplying the fuel for the fast-growing cities of Bruges, Ghent and Ypres. The reserves in the coastal peat bogs of Flanders were exhausted by the end of the 1300s or 1400s, while peat production in Brabant diminished sharply during the course of the fifteenth century.

By the time Antwerp came to dominate the world economy, its peat reserves had already been dug out to satisfy the energy needs of Flanders in the course of the preceding two centuries. As a result, peat digging shifted to the neighbouring province of Holland, from where the turf was exported to Antwerp. At the time, Holland was still largely an agrarian region with relatively few energy needs. During this period, it is estimated that between 220 and 440 hectares of peat bogs were mined every year in Holland and Utrecht. Around 1530, the then accessible reserves in both provinces became exhausted, while demand continued to grow. As a result, peat prices skyrocketed.

Peat mining intensifies: peat mining below the water table

In response to this, peat diggers developed a new tool, the "baggerbeugel" (a dredging net on a long pole, there seems to be no English translation for the term). Standing on a small boat or at the waterside, this tool allowed them to cut peat below water level and haul it up. This technique, called "slagturven" (again, no English translation available), greatly enlarged mineable peat reserves.

The peat bogs in Holland and Utrecht were up to 4.5 metres thick, but because of the high water table in the region (why we call these the "Low Countries"), only the top layer could be stripped away using conventional techniques. Digging deeper would have flooded the land and made the fuel inaccessible.

However, now that it was possible to cut peat far below the water level, the complete peat bogs could be mined. There is evidence that the "baggerbeugel" was already in use in Flanders two centuries earlier, and that the knowledge of the technique was transferred to the North.

The intensification of peat production came at a cost, though. To start, mining peat from below the water table introduced extra steps in the processing of the fuel. Due to its increased water content, the muddy peat had to be spread out on narrow and elongated strips of land which were not stripped of their peat. There, the water was pressed out by people trodding on it with boards tied beneath their clogs. Only when this was done, could the peat be cut up in blocks and stacked to dry.

Environmental costs: land turned into water

Worse, however, was the destruction of the landscape and the loss of agricultural land. Wherever the peat was mined below the water table, land disappeared into the waves. This was a rather ironic consequence for a country that spent so much effort reclaiming land on the sea elsewhere on its territory through the use of windmills. Every year, about 115 to 230 hectares of land was lost as a result of peat production below the water table. The exhausted peat bogs formed lakes that expanded to cover vast areas throughout Holland and Utrecht.

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In total, peat digging would turn more than 60,000 hectares (600 km2) of land into water in Holland and Utrecht - almost 10 percent of their total surface area.

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Only the elongated strips of land used to dehydrate the muddy peat remained. Historian Jan de Vries (see references) notes that the area between Amsterdam, Rotterdam and Utrecht "took on the appearance of a veritable Swiss cheese, with dozens of water-filled, exhausted peat bogs often separated from each other by nothing more than narrow vulnerable strips of land on which were scattered the structures of what once had been farms".

Some of these typical lakes still remain. The picture shows the "Nieuwkoopse Plassen" in Holland, today a nature reserve of 1,400 hectares. Other remaining examples are the "Loosdrechtse plassen" and "Vinkeveense plassen" in the province of Utrecht. Often, even the narrow ridges of land used for drying the peat were eventually mined or simply washed away by the waves during storms.

Things got out of hand when entire villages disappeared. Historian J.W. De Zeeuw (see references): "Around 1600, these lakes occupied most of the area between the rivers Oude Rijn, Gouwe and Hollandse Ijssel and threatened the villages of Zevenhuizen, Moerkapelle and Waddinxveen. In 1630, the church of Jacobswoude, North of the Oude Rijn, was pulled down because by then the rest of the village had been swallowed by the waves of encircling man-made lakes."

In the course of the centuries, peat digging caused the fusion of two large lakes (the Haarlemmermeer and the Leidsemeer) and several smaller ones in Holland, forming an inland sea of 17,000 hectares which destroyed several villages (Nieuwerkerk, Rijk, Vijfhuizen, and a part of Aalsmeer - see the map on the right). The water body - popularly known as the "water wolf" - threatened the surrounding cities of Haarlem, Leiden and Amsterdam in the 1800s, after which it was (largely) impoldered.

The authorities, horrified by the loss of agricultural land - and the associated tax income -  tried to stop the peat diggers during the sixteenth century by placing export prohibitions and restrictions on peat mining below the water table, but they failed. Digging out peat was more lucrative than cultivating crops. In total, peat digging would turn more than 60,000 hectares (600 km2) of land into water in Holland and Utrecht - almost 10 percent of their total surface area.

Peat production moves to the North: canal digging

Again, energy demand rose significantly from the late 16th century onwards, when economic power shifted from Flanders and Brabant to Holland. In spite of the environmental damage, peat production in the low peat bogs of Holland and Utrecht continued on a casual basis during the 1600s, with an average production of 200 hectares per year. However, this was not enough to satisfy the growing demand for the fuel, and turf prices started rising again.

In response, from the 1580s onwards, attention shifted to the somewhat higher lying peat bogs in the northern provinces of Friesland, Groningen and Drenthe - 200 to 250 kilometres away (see the map on the left). There, total production during the seventeenth century would rise to an average of almost 400 hectares per year. Most of the turf was exported to Holland.

However, mining these reserves was a totally different matter because there were few waterways. Transporting the turf all the way to the Zuiderzee, from where it could be shipped to Holland and Utrecht, would have been inordinately expensive given the transport options of the day. In order to exploit the high peat bogs in the Northern provinces, ditches and canals had to be dug, which required a large capital investment.

Historian Jan de Vries: "The result was that, instead of the numerous individual peat diggers each working small parcels of 'laagveen' [low bogs], the peat in the 'hoogveen' [high bogs] was mined by consortia of investors (urban capitalists from the western cities) who judged market conditions sufficiently attractive to buy up vast tracts of uninhabited bog, dig lengthy canals into the bogs, and hire armies of laborers to dig the peat".

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The peat was mined by urban capitalists from the western cities who judged market conditions sufficiently attractive to buy up vast tracts of uninhabited bog, dig lengthy canals into the bogs, and hire armies of labourers to dig the peat

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The maps shown here illustrate the extensive canal infrastructure that was built in the Northern provinces of the present-day Netherlands from the 1580s onwards. In the high peat regions of Groningen and Eastern Drenthe, canal building continued uninterrupted from 1580 to 1650, which opened up the main body of the peat deposit. This made some 30,000 hectares of peat available for shipping. In the high peat region of Western Drenthe, Friesland and Overijssel, canals were dug between 1600 and 1670 to reach some 30,000 hectares of peat. In total, it is estimated that some 700 km of canals were built in the northern provinces, specifically aimed at turf transport. A substantial amount of them remain, with sometimes surprising results, such as towns without roads.

Canal building had happened before in Flanders and Brabant, where the monasteries seem to have been the driving force behind large-scale, organized peat production, buying up land and hiring peat diggers. In the peat bogs in Brabant, Northeast of Antwerp, from about 1300 onwards some 20 turf canals were dug up to 16 m above sea level, each reaching lengths of 10 to 20 km. The main canals, which connected the export harbours with the peat areas, attained a total length of more than 320 km. Aqueducts were built to help the canals cross the brooks. In the Northern provinces of the Netherlands, the total length of the canals reached at least 700 km.

Peat production versus agriculture

The exploitation of the high peat bogs in the North did not always result in the loss of agricultural land, as it did in the South. Firstly, because the peat mining companies converted some peat bogs into permanently agricultural land after the peat had been dug out.

J.W. De Vries: "Once the peat was stripped away, these enterprises had a further interest in making use of the newly exposed underlying soils. Since this soil lay above the water table, the cost of converting it into productive agricultural land consisted primarily of taking the trouble to conserve the surface soil (which was [in the case of high peat bogs] in any event poor quality peat) so that it could be re-spread over the land, and heavily manuring the new soil. This occurred most systematically in Groningen, where the capital city encouraged agricultural development of the hoogveen by subsidizing the distribution of night soil."

The new canal network created to move the turf to Holland's industry in the South also provided low-cost transport for agriculture which, by itself, could never have afforded such an investment. However, the efforts to reclaim agricultural land in some parts of the country did not make up for the much larger losses elsewhere on the territory.

Few peat bogs in Groningen were brought under cultivation during the Golden Age - it was only with the arrival of artificial fertilizers at the end of the nineteenth century that large-scale recultivation could begin. In the province of Friesland, the underlying soil was not suited for agriculture and peat digging resulted in large lakes which still exist today. And as we have seen, vast tracts of (potential) agricultural land disappeared in the waves in the Southern part of the country. The result is that the Dutch became, unlike other European countries at that time, highly dependent on food imports. They produced vegetables, meat and dairy products, but they had to import about half of their grain (the staple food) from the Baltic regions - a very costly affair.

Energy consumption per capita

Until the twentieth century, the Dutch stripped an estimated 283,500 hectares (2,835 square km) of peat, close to 10 percent of the total surface of the Netherlands. However, only two thirds of this was mined in pre-industrial times. Peat digging in the Netherlands continued until 1950 using mechanical peat diggers powered by coal, as it happened in many other countries from the end of the nineteenth century.

If we take 1850 as the start of the "modern" peat mining era (the Netherlands were very late to enter the Industrial Revolution), the pre-industrial use of peat in the country amounts to just over 190,000 hectares from about 1300 to 1850. Of this, some 70,000 hectares were mined from 1600 to 1700, which roughly corresponds with the "Golden Age" of the Netherlands. All these figures are deduced from a 1978 paper by J.W. de Zeeuw, "Peat and the Dutch Golden Age" (see references). Other authors (like Jan de Vries) give higher estimates in more recent studies, with about 275,000 hectares of peat stripped after 1600. Either way, almost all peat that existed in the Netherlands has been mined.

De Zeeuw also calculated the heat content of the extracted peat, taking into account the average thickness of the mined peat layers after dehydration. He concluded that in an average year in the seventeenth century, the Dutch consumed 25,120,800 GJ of turf. With an average population of 1.5 million this amounts to 16.75 GJ per capita per year.

Other authors have come to similar figures, ranging from 13.4 to 19.3 GJ per capita per year. This is similar to dozens of poor countries today, some of which do not even reach 10 GJ per capita. Average energy consumption per capita worldwide was 76.6 GJ in 2008, only 4.5 times higher than in the seventeenth century Netherlands (though the Dutch themselves now consume much more, with 210 GJ/capita in 2003). It should be noted that the figure of 16.75 GJ/capita only includes turf consumption, not other energy sources like wind, animal labour, firewood, charcoal and coal (see further).

Urbanization and industrialisation in 17th century Holland

The high energy consumption of the Dutch was an anomaly in seventeenth century Europe. The same goes for their prosperity, and for the level of urbanization and industrialisation in the country.

More than 60 percent of Dutch people lived in cities, compared to about 10 percent in most other European countries at the end of the 17th century. The level of urbanisation in seventeenth century Netherlands was only attained in other European countries at the turn of the twentieth century. A similar development happened in Flanders and Brabant in the 1500s, where over 30 percent of the population lived in cities with more than 10,000 inhabitants. From about 1600 to 1720, the Dutch had the highest per capita income in the world - at least double that of neighbouring countries at the time and about five times higher than that of the poorest countries today.

The opening of the peat bogs in the northern provinces from the 1580s onwards meant that the Dutch had a cheap energy source that was widely available, while most other countries in Europe were entirely dependent on wood - which had become ever more expensive as deforestation advanced. The Netherlands' ample fuel reserves stimulated the development of various fuel-instensive and export-oriented industries.

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More than 60 percent of Dutch people lived in cities, compared to about 10 percent in most other European countries at the end of the 17th century.

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In several cases, the presence of these industries was solely based on the abundant and cheap supply of thermal energy. This was the case for sugar refinement, for example, which is a purely thermal process. Sugar became the world's most important commodity in the seventeenth century, and Amsterdam was Europe's largest sugar refiner by 1650. In 1662, more than half of Europe's one hundred sugar refineries were located in the Netherlands, all of which processed imported sugar from South America and the Carribean.

Salt refinement too was based solely on a massive input of thermal energy. Salt was indispensable as a preserver of meat, fish and dairy products before electrical refrigeration was available. The Netherlands had 293 salt refineries in 1674, most of them concentrated in Holland and each consuming about 800 tonnes of turf per year. About sixty of these refineries were used for packing herring barrels, another important export. In addition, the city of Haarlem became the bleacher of German linen, another industrial process that was purely built on thermal energy. For all these industries, the iconic Dutch windmills did not offer any direct advantage. 

The succes of other industries, however, was based on the combination of turf and wind power. The best example of this lies in the shipping industry. Holland became the leading builder of ships in Europe in the course of the seventeenth century. From 1625 to 1700, the Dutch shipyards produced as many as 500 seafaring vessels per year, many of them commissioned by foreign powers. The wood used to build the ships was sawn using sophisticated wind powered saw mills invented in 1596, while peat provided thermal energy for many shipbuilding processes, such as bending planks, melting tar and forging iron fittings.

Apart from that, peat offered an important indirect advantage. While a large-scale use of peat did not prevent the Dutch from importing large amounts of wood, peat catered to their thermal energy needs, and so all imported wood was almost exclusively used as a construction material. This generated a much higher return on investment than its use as firewood, and made the Dutch less vulnerable to high wood prices. Turf was also the fuel of choice for heating homes and public buildings, and for cooking. Only the very rich used firewood, which was much more expensive but produced less pollution.

Why was peat only used in the Low Countries?

The Low Countries were not the only region that suffered from a severe shortage of wood reserves between 1100 and 1700. In addition, peat was found over large parts of Europe, most notably north of the Alps. Why, then, did other countries not resolve their energy shortages by mining peat?

For these pre-industrial countries, the value of energy deposits depended on the cost of transportation rather than the cost of gathering the fuel itself. There exists no period in history when a global, continental or even national shortage of wood occured. The problem was always local, caused by deforestation around urban (and industrial) centers.

Land-based transport - which amounted to carts on bad roads - was extremely slow, labour-intensive and expensive, limiting the practical distance between energy deposits and consumption centres to 20 to 25 km at most. The only exception to this was transport on water, which, in pre-industrial times, was powered by wind or by animal or human labour on towpaths (this was much more efficient than land-based transportation because of low friction-resistance).

One look at the map of the Low Countries immediately reveals why the region could afford to transport turf over large distances: it is criss-crossed by lakes and rivers. From Groningen and Friesland in the outermost northern part of the present-day Netherlands, one can sail (almost literally) straight to Amsterdam, Utrecht, Rotterdam, and then Antwerp, Brussels, Ghent and Bruges in present-day Belgium. No other region in Europe has such a dense water transport network.

To boot, the region is windy and flat, offering great conditions for sailing - and deforestation only improved these conditions. Importantly, the Low Countries are located near the water table - as were their peat reserves. The digging of navigable canals in the peat areas, and the linking of these canals to the already existing, extensive network of natural waterways was relatively easy. Because these natural waterways gave access to all major cities, the turf could be transported by ship directly from the peat fields to the doorstep of the consumer. Hardly any land-based transportation was involved, and this kept costs low.

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Land-based transport was extremely slow, labour-intensive and expensive, limiting the practical distance between energy deposits and consumption centres to 20 to 25 km at most.

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In most other countries, peat reserves were located too far above the water table, making the construction of canals much more expensive. Often, cities were too far from potential peat reserves or did not have access to navigable rivers. This explains why large-scale peat digging in other European countries and the US only started at the end of the nineteenth century, when peat could be hauled by steam trains or locally converted to electricity (which is easier to transport). 

Coal and the end of the Dutch Golden Age

Peat was not the only fossil fuel used during the second millenium AD in Europe. Coal mining started in the thirteenth century in England, Wales and what is now the French speaking part of Belgium. All over Europe, coal quickly became a wanted fuel for specific industrial processes, particularly for blacksmithing and lime manufacturing.

Large-scale coal mining started in the 1400s. In 1430, between 1,600 and 2,000 people worked in the coal industry in Liège (present-day Belgium). From the 1500s onwards, coal was used on an ever increasing scale in London, which was then one of the most populated cities in Europe. There, coal was used industrially, but more often in households for heating and cooking.
 
At the beginning of the 1600s, when the Dutch Golden Age began, coal accounted for three quarters of fuel consumption in London, which caused extensive air pollution. Coal burns much dirtier than wood, which is the reason why it was previously forbidden in England. However, the acute shortage of firewood from the 1500s onwards left the English little other choice than to switch to the abundant fuel. Peat was not an option for the English for many of the reasons mentioned above. 

The crucial role of iron production

Initially, coal offered significant drawbacks compared to peat, which meant that England's early use of fossil fuels did not provide a commercial advantage during the seventeenth century. In most production processes, coal could not be used because it came into direct contact with the product, which was then ruined by coal's impurities - notably sulfur. Only in processes where the product could be separated from the fuel did the substitution of coal for wood cause no problems.

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At the beginning of the 1600s, coal accounted for three quarters of fuel consumption in London, which caused extensive air pollution.

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Because of its lower sulfur content, peat did not have these limitations. The Dutch could use it for almost all thermal processes in their industries. Over time, however, the English managed to adapt their industrial processes for the use of coal instead of wood and charcoal. With every step they took, the English slowly caught up to the Dutch. A turning point came at the dawn of the eighteenth century when the last - and most important - industrial process was converted to coal: the production of iron. 

This last step, made possible by the introduction of 'cokes' or purified coal, marked the start of the Industrial Revolution in the Western world. (It should be noted that the Chinese already developed this process in the 11th century). From then on, the use of iron as a construction material was no longer limited by the supply of wood.

Turf, on the other hand, could not deliver the intense heat produced by coal, and hence was not used in iron production, nor to power steam engines. (The Dutch never produced iron, they imported it). Moreover, the caloric value of coal is four times higher than that of turf for a given volume, making it much easier to transport and store than peat. The combination of steam power and iron brought the English the rail system, solving the problem of transporting their fuel supply. The railway also proved faster and more flexible than the canal system.

Exhaustion of the accessible peat reserves

Around the same time, the most accessible Dutch peat reserves became exhausted. In addition, there was a growing problem with the silting of the shallow harbours and waterways, increasing the costs of turf transport.  More and more sandbanks appeared, over which vessels had to be dragged. A similar thing happened in Bruges a few centuries earlier. The unique geographical conditions of the Low Countries, which made the early large-scale use of fossil fuels possible, eventually became a disadvantage. The depletion of the peat reserves and the difficulties in turf transport led to rising turf prices, until the point at which imported coal became cheaper.

To combat this, Dutch industries switched from peat to coal, whenever they could adapt their production to use the cheaper fuel. English export of coal to Holland rose from 35,200 tonnes in 1700 to 117,900 tonnes in around 1750. The import of coal put Dutch industries at a disadvantage, because the English added tax duties. From the 1700s on, Dutch prosperity began to decline. The import of grain became too expensive, and de-urbanisation set in as more people returned to farming. By 1815, the level of urbanization had fallen back from 60 to 38 percent.

Can we power a prosperous society on renewable energy?

Pre-industrial use of coal and peat occured succesively in those parts of Europe that dominated industrial production from the 1100s to the start of the Industrial Revolution. The Flemish, the Dutch and the English, consecutively, became the most prosperous regions in Europe at the very moments when they used the largest amounts of fossil fuels. In other words, all economic success stories of the past millenium are based on an ample supply of fossil fuels - accompanied by serious ecological damage. Moreover, these regions produced many exports, so that countries that did not use fossil fuels also benefitted from their application.

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All economic success stories of the past millenium are based on an ample supply of fossil fuels - accompanied by serious ecological damage.

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All this does not mean that a prosperous society cannot be built on 100 percent renewables. We can now transport biomass over larger distances, due to good roads and cost-effective transport options. And I am not referring to motorways and diesel trucks, but to trains, strip roads, trolleytrucks, cargo bicycles and light electric vehicles in flat areas, and aerial ropeways and cable trains in mountainous regions.

Furthermore, we now have an additional renewable energy source that could deliver vast amounts of thermal energy: solar thermal power (see article "The bright future of solar powered factories"). The merits of solar thermal heat and concentrated solar power have been known for centuries, but the materials and industrial processes for large-scale deployment only became available at the end of the nineteenth century. The same applies to geothermal power, the potential use of which was previously limited because of a lack of materials and technology.

It is obvious that a prosperous future for seven billion people cannot be based on pre-industrial technology. The key to our success, however, lies in choosing the best of industrial technology and discarding the rest.

Kris De Decker (edited by Deva Lee & Shameez Joubert)

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Sources:

• "Energiemarkten en energiehandel in Holland in de late middeleeuwen", Charles Cornelisse, 2008.
• "Peat and the Dutch golden age" (.pdf), J.W. de Zeeuw, 1978.
• "The First Modern Economy: Success, Failure, and Perseverance of the Dutch Economy, 1500-1815", Jan de Vries, 1997.
• "The Economy of Europe in an Age of Crisis, 1600-1750", Jan De Vries, 1976
• "Verdwenen venen. Een onderzoek naar de ligging en exploitatie van thans verdwenen venen in het gebied tussen Antwerpen, Turnhout, Geertruidenberg en Willemstad. 1250-1750", K.A.H.W. Leenders, 1989 (English summary).
• "Peat and Canals" (.pdf), Michiel A.W. Gerding
• "Meeten, boren en besien: turfwinning in de buitenrijnse ambachten van het Hoogheemraadschap van Rijnland 1680-1800", A.J.J. van't Riet, 2005
• "Delfstoffen, machine- en scheepsbouw", in "Geschiedenis van de techniek in Nederland", H.W. Lintsen, 1993.
• "Het verloren technisch paradijs", in "Geschiedenis van de techniek in Nederland". H.W. Lintsen, 1993.
• "Vervening", "Turfsteken", "Veen", "Slagturven", "Baggerbeugel", Dutch Wikipedia.
• "Canals and energy. The relationship between canals and the extraction of peat in the Netherlands 1500-1950" (.pdf), Michiel A.W. Gerding, in "Peatlands", February 2010.
• "The Rise of Commercial Empires: England and the Netherlands in the Age of Mercantilism, 1650-1770 ", David Ormrod, 2003
• "A Forest Journey: The Story of Wood and Civilization", second edition, John Perlin, 2005
• "The Making of Urban Europe, 1000-1994", Paul M. Hohenberg & Lynn Hollen Lees, 1985
• "Urban World History: an Economic and Geographical Perspective.: An article from: Canadian Journal of Regional Science", Luc-Normand Tellier, 2009
• "Peatlands and climate change" (pdf), International Peat Society, 2008
• "The Dutch Republic in the Seventeenth Century: The Golden Age", Maarten Roy Prak, Diane Webb, 2005.
• "The Rise of the Amsterdam Market And Information Exchange: Merchants, Commercial Expansion And Change in the Spatial Economy of the Low Countries, C.1550-1630", Clé Lesger, 2006.
• "Turf fires -burning peat". Old and Interesting.
• "The Mother of All Trades: The Baltic Grain Trade in Amsterdam from the Late 16th to the Early 19th Century", Milja van Tielhof, 2002.
• "Energy transitions: history, requirements, prospects", Vaclac Smil, 2010.

Related articles:

• Wind powered factories: the history (and future) of industrial windmills
• The bright future of solar powered factories
• Rings of fire: Hoffmann kilns
• Boat mills: water powered, floating factories
• Trolley canal boats
• Recycling animal and human dung is the key to sustainable farming
• The sky is the limit: human powered cranes and lifting devices
• Aerial ropeways: automatic cargo transport for a bargain
• Wood gas vehicles: firewood in the fuel tank

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Most of the talk about renewable energy is aimed at electricity production. However, most of the energy we need is heat, which solar panels and wind turbines cannot produce efficiently. To power industrial processes like the making of chemicals, the smelting of metals or the production of microchips, we need a renewable source of thermal energy. Direct use of solar energy can be the solution, and it creates the possibility to produce renewable energy plants using only renewable energy plants, paving the way for a truly sustainable industrial civilization.

Picture: ARUN.

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The missing element in our sustainable energy strategy is a renewable source of heat energy

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A large share of energy consumed worldwide is by heat. Cooking, space heating and water heating dominate domestic energy consumption. In the UK, these activities account for 85 percent of domestic energy use, in Europe for 89 percent and in the USA for 61 percent (excluding cooking).

Heat also dominates industrial energy consumption. In the UK, 76 percent of industrial energy consumption is heat. In Europe, this is 67 percent. I could not find figures for the US and for the world as a whole, but these percentages must be similar (and probably even higher on a worldwide scale because many energy-intensive industries have been outsourced to developing countries). Few things can be manufactured without heat.

Solar panels and wind turbines are no producers of heat energy

The importance of heat in total energy consumption sharply contrasts with our efforts to green the energy infrastructure. These are largely aimed at renewable electricity production using wind turbines and solar panels. Although it is perfectly possible to convert electricity into heat, as in electric heaters or electric cookers, it is very inefficient to do so.

It is often assumed that our energy problems are solved when renewables reach 'grid parity' - the point at which they can generate electricity for the same price as fossil fuels. But to truly compete with fossil fuels, renewables must also reach 'thermal parity'.

Though today in some locations it may be as cheap to produce electricity with wind or solar energy as with gas or coal, it still remains significantly cheaper to produce heat with oil, gas or coal than with a wind turbine or a solar panel. This is because it takes 2 to 3 kWh of fossil fuel thermal energy to create 1 kWh of electricity, so it is at least 2 to 3 times cheaper to make heat by simply burning the fossil fuels directly than to use an electric renewable technology at grid parity.

Manufacturing wind turbines and solar panels requires heat

This means that solar panels and wind turbines will have to become two to three times cheaper than they are today in order to reach thermal parity with fossil fuels. This might sound reasonably possible, especially if you expect fossil fuel prices to rise. But consider this: even though they are intended to replace fossil fuels, renewable energy sources like wind turbines and solar panels are in fact dependent on a continuous supply of fossil fuels. 

Solar panels and wind turbines do not need fossil fuels to operate, but they do need fossil fuels for their production. You won't find any factory manufacturing PV solar panels or wind turbines using energy from their own PV solar panels or wind turbines. Why not? Because it would be 2 to 3 times more expensive to generate heat with solar panels or wind turbines than with fossil fuels. Yet to make solar panels and wind turbines, to produce steel and silicon for instance, heat is what is most needed. This means that the production costs of solar panels and wind turbines will be affected negatively by rising fossil fuel prices.

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You won't find any factory manufacturing PV solar panels using energy from their own PV solar panels, because it would be 2 to 3 times more expensive to generate the heat required for producing steel and silicon

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The same goes for batteries, which are an essential element of electric cars and renewable electricity storage, and for many other modern green technologies, like LEDs and heat pumps. They require heat for their production, and this heat can be delivered at least 2 to 3 times cheaper by burning fossil fuels than by using wind turbines or solar panels (cheap electricity from hydropower plants is also an option, but has limited potential). This is a fundamental problem, because we will have to produce new wind turbines and solar panels every 20 to 30 years, and new batteries every 5 to 10 years.

Renewable source of heat energy

The missing element in our sustainable energy strategy is a renewable source of thermal energy. Geothermal energy produces heat, but its potential is limited to regions that have volcanoes. Biomass is another option, but it faces many problems. If we were to try to provide an important share of heat demand by burning biomass, we would quickly come up against the limits of what the planet can produce. There is only one source of heat energy left, and it is a powerful and inexhaustible one: solar energy.

We tend to see solar energy as yet another way to generate electricity, using photovoltaic panels or solar thermal power plants. But solar energy can also be applied directly, without the intermediate step of generating electricity. Basically, harvesting direct solar energy can happen in two ways: by means of water-based flat plate collectors or evacuated tube collectors, which collect solar radiation from all directions and can reach temperatures of 120 °C (248 °F), and by means of solar concentrator collectors, which track the sun, concentrate its radiation, and can generate much higher temperatures. These can be parabolic trough systems, linear concentrating Fresnel collectors, parabolic dish systems or solar power towers. Almost all of these technologies were developed at the turn of the 20th century.

Solar thermal power versus solar thermal heat

The problem is that we mostly use this technology for the wrong purpose. In today's solar thermal plants, solar energy is converted into steam (via a steam boiler), which is then converted into electricity (via a steam turbine that drives an electric generator).

This process is just as inefficient as converting electricity into heat: two-thirds of energy gets lost when converted from steam to electricity. This is one of the main reasons why the use of solar thermal energy to produce electricity is only cost-effective in deserts.

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If were to use concentrated solar power to generate heat instead of converting this heat into electricity - a process in which two thirds of energy gets lost - the technology would be cost-effective anywhere on Earth

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If we were to use solar thermal plants to generate heat instead of converting this heat into electricity, the technology could deliver energy 3 times cheaper than it does today and become cost-effective also in less sunny regions. The crucial difference between solar thermal electricity and other renewables producing electricity is that solar thermal actually starts with heat energy. Thus, contrary to other renewables, the cost of heat energy using the technology is far lower than the cost of electricity, and so it can compete with burning fossil fuels at the thermal level.

Low temperature solar heat

This can be demonstrated by flat plate collectors and evacuated tube collectors, which are used for domestic hot water preparation and (to a lesser extent) interior space heating. This technology is used without any conversion losses and is cost-competitive with fossil fuels almost anywhere on Earth. According to the 2011 update of the International Energy Agency's Solar Heating and Cooling Programme (IEA-SHC), solar thermal heat is now the second most important renewable energy source following wind, and a much more important energy source than photovoltaics and solar thermal power plants. Almost 60 percent of solar thermal heat capacity can be found in China and another 20 percent is in Europe. The US and Canada (where the main application is to heat swimming pools) account for less than 9 percent.

Sweden, Denmark, Spain, Germany and Austria have the most sophisticated markets for different solar thermal applications, including large-scale plants for district heating and a small but growing number of systems for air conditioning and cooling (using an absorption chiller). By the end of 2009, 115 solar supported district heating networks and 11 solar supported cooling systems were installed in Europe. Canada, Saudi Arabia and Singapore have also built a few large-scale solar heat systems for producing hot water, space heating and cooling. 

The potential of solar heat for industrial processes

Without a doubt, solar heat for domestic purposes should continue to be encouraged and a lot of potential remains. But it does not stop there. According to a 2008 report (pdf), which analyses the situation in Europe, the potential for solar heat in industrial processes is even larger than in the domestic market. About 30 percent of industrial heat demand in Europe is below 100 °C (212 °F), which could be delivered by commercially available flat plate collectors (< 80 °C) and evacuated tube collectors (< 120 °C) currently used for domestic purposes.

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Almost 60 percent of heat demand in Euopean industry could be covered by already available and cost-effective technology using an inexhaustible renewable energy source that has no ecological disadvantages whatsoever.

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Another 27 percent of industrial heat demand requires medium temperatures (100 to 400 °C or 212 to 752 °F), which could be reached by improved versions of these collectors (up to 160 °C, see this document) and by commercially available solar concentrator technologies now mostly used for electricity production: parabolic troughs, parabolic dishes and linear concentrating Fresnel collectors.

This means that at least 57 percent of heat demand in European industry (or almost 40 percent of total industrial energy demand) could be covered by available and cost-effective technology using an inexhaustible renewable energy source that has no ecological disadvantages whatsoever. The capital costs (and embodied energy) of this would be much less than replacing a similar amount of fossil fuel energy use with solar panels or wind turbines. And of course, it could be done anywhere, not just in Europe.

 Solar heat in industry: existing applications

At low and medium temperatures, solar heat can be used for industrial processes in several ways. It can provide warm water for processes like bottle washing or chemical processes. Secondly, it can provide hot air for drying and baking processes, for instance in the food and paper industries. Thirdly, it can generate steam that can be fed into steam heat distribution networks, which are widely used in many industries. The interesting thing is that in all these applications, the existing industrial machinery and distribution infrastructure remains in place. Only the energy source is replaced.

Some manufacturers have started marketing their solar concentrator technologies for the use of heat generation in industry, in addition to their application as electricity generators. Examples are Sopogy (a Hawaian company that sells modular parabolic trough systems - picture above), the Solar Power Group (a German company that sells linear concentrating Fresnel collectors) and  HelioDynamics (an American seller offering similar technology - picture below).

Installations for the use of solar industrial process heat are still rare, but they exist. German heating systems manufacturer Viessmann installed 260 m² of its own flat plate collectors on its factory in France to provide hot water for a chemical process, taking a first step towards producing renewable energy using renewable energy. A solar thermal plant based on 1,900 m² of parabolic troughs provides steam for a pharmaceutical plant in Egypt. A similar solar thermal plant was built for a dairy plant in Greece. A food processing facility in California has 5,000 m² of parabolic troughs to produce steam used in the manufacturing process. Several industrial applications of solar heat have been built in India, using both flat plate collectors and concentrator technologies.

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At low and medium temperatures, solar heat can be applied to industrial processes using already existing machinery and heat distribution pipelines

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A solar concentrator system called ARUN - a Fresnel parabolic reflector with point focus that delivers temperatures from 80 to 400 °C - has been installed in six industries, ranging from a dairy plant to an automobile manufacturer (picture on the left). India also has several large solar cooking facilities for community kitchens (schools, hospitals, factories, religious centres). The largest one consists of 84 parabolic dish systems reaching temperatures of up to 650 °C and producing up to 38,500 meals per day. The largest solar process heat application to date was recently installed in Hangzhou, China, where 13,000 m² of solar collectors on the roof of a textile factory provide hot water for a dyeing process. The Global Solar Thermal Energy Council is continually updating its list of new industrial applications of solar heat.

Renewables building renewables

The remaining 43 percent of industrial heat demand in Europe is above 400 °C (752 °F). These include many of the industrial processes that we need to manufacture renewable energy sources (wind turbines, solar panels, flat plate collectors and solar concentrators) as well as other green technologies (like LEDs, batteries and bicycles). Examples include the production of glass (requiring temperatures up to 1,575 °C) and cement (1,450 °C), the recycling of aluminum (660 °C) and steel (1,520 °C), the production of steel (1,800 °C) and aluminum (2,000 °C) from mined ores, the firing of ceramics (1,000 to 1,400 °C) and the manufacturing of silicon microchips and solar cells (1,900°C ).

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Solar furnaces can reach temperatures up to 3,500 °C (6,332 °F), enough to produce microchips, solar cells, carbon nanotubes, hydrogen and all metals

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These temperatures can be achieved by solar concentrator technology. Linear reflectors (parabolic trough systems and linear concentrating Fresnel collectors) are limited to temperatures of about 400 °C, but point concentrators can reach higher temperatures. These include parabolic dish systems, solar power towers, and solar furnaces - which are basically a combination of power towers and parabolic dish systems. 

Solar furnaces can produce temperatures up to 3,500 °C (6,332 °F), enough to manufacture microchips, solar cells, carbon nanotubes, hydrogen and all metals (including tungsten which has a melting point of 3,400 °C). These temperatures can be achieved in just a few seconds - see this short video of a solar furnace melting steel. The most powerful solar furnace is the one at Odeillo in France, built in 1970, which concentrates the light of the sun 10,000 times and has a power output of 1 MW.

More than 60 heliostats (only one is seen on the picture above, in the lower righthand corner) direct the rays of the sun onto a parabolic mirror of more than 1,800 square metres, from which they are concentrated on a focal point with a diameter of only 40 centimetres in the tower in front of it. A similar solar furnace stands in Uzbekistan, built in 1976, but it is slightly less powerful due to lower solar insolation in the region. The picture on the right shows it in action, melting metal.

You don't need such an enormous structure to achieve high temperatures. Several smaller solar furnaces have been built, often using only one heliostat. They reach similar or only slightly lower temperatures (usually between 1,500 and 3,000 °C) than the giants pictured above, though at significantly lower power outputs (between 15 and 60 kW). They can perform most of the same processes as the large solar furnaces, but processing smaller amounts of materials or chemicals.

Examples of smaller solar furnaces can be found at the Paul Scherrer Institute in Switzerland (pictured above), the National Renewable Energies Laboratory in the USA, the Plataforma Solar de Almería in Spain, the German Aerospace Center in Germany, and the Weizmann Institute of Science in Israel (a solar power tower). They have concentration ratios between 4,000 and 10,000. In solar concentration, the temperature is proportional to the degree of concentration, whereas power will be proportional to size and efficiency (which is mostly determined by temperature). 

Solar energy improves product quality

Solar furnaces not only have the potential to replace fossil fuels for the energy-intensive production of construction materials, chemicals, and high-tech products like microchips and solar cells, but they also offer additional benefits because of their pure combustion and selective heating capacities. A 1999 research paper describes the manufacturing of silicon solar cells using a solar furnace, concluding that "solar furnace processing of silicon solar cells has the potential to improve cell efficiency, reduce cell fabrication costs, and also be an environmentally friendly manufacturing method. We have also demonstrated that a solar furnace can be used to achieve solid-phase crystallization of amorphous silicon at very high speed."

As opposed to low and medium temperature processes in industry, where only the energy source is replaced and the machinery and distribution infrastructure can remain in place, most high temperature solar heat applications require new machinery. Furnaces and kilns have to be rebuilt. Some efforts have been made. The Paul Sherrer Institute in Switzerland designed several solar powered lime and cement kilns (pdf), and research concluded that they could become cost-competitive with a fossil fuel powered kiln (pdf) following some further technological improvements. Again, the quality of the product turned out to be better using solar energy, eliminating combustion by-products.

Low-tech, open source solar concentrators

Though existing solar funaces prove that anything could be produced using direct solar heat instead of fossil fuels, this is not yet possible in a cost-effective way (it is cheaper to use fossil fuels). However, since solar furnaces could produce all materials needed to build more solar furnaces, they might become cost-effective even without technical improvements if fossil fuels become more expensive.

Moreover, the capital costs of solar concentrators are decreasing quickly following some recent innovations aimed at simplifying the technology. These might not only lead to cheaper high temperature solar heat concentrators in the future, but they also make the use of solar heat for medium temperatures more affordable and competitive today.

The most spectacular example is the Solar Fire P32 (picture above and pictures below), a solar concentrator developed in 2010 by the French NGO the Solar Fire Project. It is an open source design (joining forces with the Open Source Ecology project), but the machine can also be bought for 7,500 euro dollar - less than the price of an urban wind turbine.

The Solar Fire P32 is built using simple, abundant and non-toxic materials. Contrary to most other modern green technologies, there is no need for rare earth metals or advanced tools that are not found in an average metal workshop. Essentially, this is a renewable source of heat energy analogous to home made windmills used to produce mechanical energy.

The machine can deliver up to 15 kW and can reach a focal temperature of 700 °C (1,292 °F), enough to melt (and thus recycle) aluminum, the material that is used to make its reflectors. This means that you could use a Solar Fire P32 to make another Solar Fire P32. Or almost. The receiver and the supporting structure are made of steel, which requires a higher melting temperature to recycle. However, the structure could as well be made of wood, bamboo, organic fibre or aluminum, and the steel receiver could easily be scavenged material. The use of glass improves the workings of the device, but is not strictly necessary.

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The Solar Fire P32 costs 7,500 dollar and can be used to make another Solar Fire P32

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The Solar Fire P32 is composed of 360 small mirrors with a total surface of 32 square metres, focusing sunlight on a steam boiler above them. The steam can be used directly to purify large quantities of water, boil milk, produce edible oils, make charcoal, bake bricks, make paper, and so on.

Increasing energy autonomy

The steam can also drive a steam engine to directly power a water pump, oil and grain mills, cotton spinning, or any other stationary application requiring mechanical power. Connected to a steam generator, the machine can also generate electricity (up to 3 kW). These two last applications involve conversion losses, but they are interesting additions for those who want to achieve energy independence, especially in regions where there is lots of sun but no wind. The machine can produce heat, electricity and direct mechanical energy. 

The Solar Fire P32 is - in the first place - aimed at developing countries and designed to be cost-effective compared to burning coal and wood, reducing deforestation and pollution, increasing energy autonomy, and providing an energy source at the scale of traditional practices and small industries. It has been built in Mexico, Cuba, Burkina-Faso, Mali, India and Kenya, but also in Texas, France and Canada. Obviously, the design could also be useful in the developed world, where the supply of fossil fuels might not remain as easily accessible as it is today. 

Simplifying technology

Apart from the additional equipment that is required to generate electricity, conventional solar concentrator technologies demand heavy capital investments for several reasons. Parabolic trough systems and parabolic dish systems require curved mirrors that are expensive to produce. Moreover, these mirrors cannot be manufactured locally and often have to be transported over long distances, increasing costs further. In both systems the curved mirrors are large and heavy, requiring rigid frames, strong foundations, powerful hydraulics and sophisticated tracking systems to follow the sun. In parabolic dish systems, the heat engine or steam boiler is part of the moving structure, increasing weight and thus making things even worse.

Solar power towers - which were invented in 1878 - solve some of these issues: they use nearly flat mirrors and all mirrors share one stationary receiver. But, they require the construction of a large tower building. Last but not least, all of these systems have very high land requirements because of overshadowing issues. Linear Fresnel concentrators use (mostly) flat mirrors, have simpler tracking systems and are more compact, but they can only reach temperatures of 250 °C (using relatively low-tech materials) or 450 °C (using sophisticated technology).

The Solar Fire is a Fresnel parabolic reflector with point focus, just like ARUN - but unlike that machine it is placed horizontally and the receiver does not have to be turned together with the mirrors, resulting in light weight and high wind resistance. The machine uses slightly curved mirrors, achieved by mechanical bending which can be done on the spot. Sun tracking of the mirrors is done by hand, eliminating the need for electronics and electric motors altogether (multiple mirrors can be turned at once using hand operated wheels). This might sound crude, but for industrial applications the machine has to be supervised anyway.

And because it is open source, it can be further improved by anyone. Eerik Wissenz, the designer of the machine, thinks this is the only way: "Companies pursuing patents for solar collectors have fallen into a complexity trap. Since solar energy is free it is far simpler to add 5 percent more surface area instead of creating complex machines too expensive to be commercially viable. Solar fire concentration is so simple it cannot be patented."

Low-tech solar furnaces

High temperature solar furnaces can be low-tech autonomous systems, too. One example is the large magnifying glass used by Sundrop Jewelry, which reaches high enough temperatures to melt coloured bottle glass into handcrafted jewelry. Of course the power output is low, making this installation useless if you want to produce industrial quantities of glass. But it shows that solar heat can be used on any scale.

Another example is the Solar Sinter Project by Markus Kayser, in which glass is produced using only sunlight and desert sand. I would like to quote the artist here: "Whilst not providing definitive answers, this experiment aims to provide a point of departure for fresh thinking".

Storage

How can you power factories using an energy source that is not always available? Solar insolation varies throughout the day and the seasons, and there is no sun at night. Moreover, solar concentrator technologies only work with unscattered sunlight, which means that a passing cloud stops energy production. This raises two questions. Some industrial processes work fine with intermittent energy supply, but how do you guarantee an uninterrupted supply of energy to a process that requires it? And what do you do when there is no sun at all for a week?

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Storing heat is much cheaper and more efficient than storing electricity in a battery

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There are three ways to deal with the intermittency of solar power. The first solution is to design hybrid systems: make solar and already existing energy sources work together. This is how most of today's solar thermal power plants work. In this scenario, which offers a solution for both short and long term storage, industrial processes are powered by solar heat whenever it is available. When it is not, solar energy is instantly replaced by fossil fuels or electricity. It is not an ideal solution, but it could save large amounts of energy. And we don't need new technology to make it work.

The second strategy is to store solar energy so that it can be used to smooth out industrial processes (analogous to a flywheel for smoothing out mechanical processes) and to guarantee energy supply on cloudy days or at night. Storage of heat is much cheaper and more efficient than storage of electricity. The most low-tech way is to store heat in well-insulated water reservoirs - another technology that is more than 100 years old. The disadvantages are that you need quite a lot of space, and that water storage only works up to a temperature of 100 °C (212 °F). There are more compact ways to store heat at higher temperatures, for example by using ceramics or phase-changing materials (certain salts). These storage media are already used in one solar thermal power plant, but they would be even more efficient if used in a thermal only system. Innovative technology could further improve heat storage.

Storing work instead of energy

The third way to deal with the intermittency of solar heat is to store work instead of energy. We let our factories work when the sun shines, and only when the sun shines. Just like we wait for a sunny day to do the laundry, we could wait for a sunny day to bake bricks, recycle metal or produce smartphones. Industrial production would be concentrated in summer months. Of course, there is a price to pay. Industrial production would be lower. But considering the fact that our energy and environmental problems are largely caused by overproduction and overconsumption of goods, this is not as far-fetched as it might seem.

Combining all three strategies could be a solution. In that scenario we would run part of our factories only when the sun shines (and when the wind blows), using heat storage, fossil fuels, biomass or electricity to smooth out industrial processes if necessary. Critical goods could be produced continuously combining solar heat and heat storage, fossil fuels, or biomass. Of course, not all climates are blessed with enough sun to make solar heat a viable option to power the whole industry. But since many people are now talking about outsourcing electricity production to desert regions, we could just as well move our factories to regions where there is plenty of sun. It is much more efficient to transport manufactured goods over large distances than to transport electricity.

Solar powered enhanced oil recovery

As always, a sustainable technology can be used for unsustainable purposes. Solar heat is a great way to get more oil out of fields that are now considered exhausted. Getting that remaining oil out using gas would cost more money and energy than the oil could return, but using a free source of energy changes everything.

At least one company specializes in this application. Glasspoint, a US firm originally founded to use solar heat for drying gypsum wall board, has seen remarkable growth promoting "Solar Enhanced Oil Recovery".

This has been tried before, but they use an innovative technology: parabolic trough mirrors suspended from the ceiling of enormous glasshouse structures that are equipped with robotic cleaning systems. Because they are protected from wind, sand and dust by the greenhouse, the mirrors can be made extremely light and without protective glass layers - lowering their costs and increasing their efficiency. The steam that is generated by the solar heat is pumped into the oil reservoir. The more sun there is, the more oil will come to the surface. Only 20 to 40 percent of an oil field can be recovered using standard techniques, but as much as 60 to 80 percent can be recovered using solar heat. In the end, solar heat could thus increase fossil fuel production and CO2-emissions.

Kris De Decker (edited by Rachel Meyer)

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Sources, inspiration & more information:

• The thermal problem and the solar (thermal) solution, Eerik Wissenz, 2011.
• Concentrating Solar Concentrators at the Build it Solar Site. Lots of links to DIY-projects. Thanks to Paul Nash.
• High temperature solar collectors, Robert Pitz-Paal, in 'Solar Energy Conversion and Photoenergy Systems'.
• Direct Use of the Sun's Energy, Farrington Daniels, 1964. 
• Task 33 - Solar heat for industrial processes, Solar Heating and Cooling Programme, International Energy Agency.
• Potential for Solar Heat in Industrial Processes (pdf), Claudia Vannoni, Riccardo Battisti and Serena Drigo, Task 33
• Process Heat Collectors - state of the art within task 33/IV (pdf), Werner Weiss and Matthias Rommel
• Solar thermochemical process technology, Aldo Steinfeld & Robert Palumbo, 2001
• Solar Heat Worldwide 2011 (pdf), SHC, Werner Weiss & franz Mauthner, may 2011
• The Value of Concentrating Solar Power and Thermal Energy Storage, National Renewable Laboratory, 2010
• Understanding solar collectors, George Kaplan, 1985
• Global Solar Thermal Energy Council.
• So-Pro: European project on solar process heat
• European Solar Thermal Industry Association
• The European Alliance SolLab
• SolarPACES
• CSP- how it works

Related articles:

• Medieval smokestacks: thermal energy in pre-industrial times
• The ugly side of solar panels: how much energy does it take to produce solar panels?
• The monster footprint of digital technology: how much energy does it take to produce microchips?
• Wind powered factories: the history (and future) of industrial windmills.
• Pedal powered farms and factories: the forgotten future of the stationary bicycle machine.
• Bike powered electricity generators are not sustainable: you are merely pedalling to generate the energy required to manufacture the battery.
• How (not) to resolve the energy crisis: piling up energy sources.
• Heat your house with a swimming pool.
• Updates for this article: see the solar category at No Tech Magazine.

Main page.

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If we boost the research on pedal powered technology - trying to make up for seven decades of lost opportunities - and steer it in the right direction, pedals and cranks could make an important contribution to running a post-carbon society that maintains many of the comforts of a modern life. The possibilities of pedal power largely exceed the use of the bicycle.

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One way to solve the large energy losses of pedal power generators is not to produce electricity at all but power devices mechanically, whenever possible. Another way - the only way for devices that cannot be powered via a direct mechanical connection because they do not rely on rotary motion - is to make the generation of electricity more efficient. This can be done by building a pedal powered generator from scratch instead of using a road bicycle, or by ditching one or several electronic components in the power transmission chain. All approaches can be combined, resulting in a pedal power unit that can power a multitude of mechanical devices and generate electricity comparatively efficiently.

Direct Mechanical Power Transmission

Many machines could be powered by a direct mechanical connection, though it generally means adapting the device so that it can work independently of electricity. However, stationary pedal machines with direct mechanical power transmission - although they were common in the old days - are not available commercially in the western world.

The only exception seems to be the Fender Blender, a pedal powered machine used to make smoothies (picture on the right). However, old school bicycle machines are now being designed both by amateurs in the western world and non-profit organisations in the developing world.

In Guatemala, Mayapedal has been building some 2,000 pedal powered machines from old bicycle parts since 2001. To date, the NGO has built pedal powered water pumps, grinders, threshers, tile makers, nut shellers, washing machines and blenders. These cost only $40 to $250 to make. Their contraptions have become more sophisticated and even cheaper to build over time, evolving from adapted bicycles to pedal powered machines built from scratch which incorporate a flywheel, and are capable of driving different types of appliances.

Another example is the VitaGoat Cycle Grinder developed by the Canadian NGO Malnutrition Matters. The pedal powered grinder forms part of a complete food processing system which is delivered to developing countries in Asia and Africa. Chocosol teaches local people in Mexico to build their own pedal powered cacao bean grinders and the Canadian promoters also use the technology in their shop in Toronto. The Full Belly Project designs human powered nut shellers for farmers in Africa.

Then there are the many contraptions built by individuals too: the pedal powered washing machines by Alex Gadsden and Homeless Dave, the pedal powered soap blender by Frederick Breeden, or the pedal powered apple grinder by Ben Polito. Similar machines have also been built outside the US. Some have concentrated on restoring and putting to use antique machines, like Blue Ox Millworks.

One obvious disadvantage of designing a pedal powered machine for every application in the household, farm or workshop is that you need a lot of space. Furthermore, designing a pedal power unit for every tool might become labour-intensive, costly and energy-intensive.

This is not as much of a problem in cases of small-scale industrial use, where few machines are required in order to manufacture a product. A good example of this is the pedal powered soap blender mentioned above. For this reason, a pedal powered blender could be a realistic option for small businesses, such as a smoothie bar. However, when more tools are needed and space is restricted, as is often the case, we need to find ways to get around this problem. One solution is to use pedal power to generate electricity which can then be used to power different devices. However, this approach is highly inefficient with energy losses of up to more than 70 percent and should be avoided whenever a device can be powered in a mechanical way.

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The design of universal pedal powered units with direct mechanical transmission was extensively researched in the 1970s

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Another solution is to design a universal pedal power unit with direct mechanical transmission that can be used to operate a large variety of different tools and devices (including a generator). This method, which solves both the space and inefficiency problem, was extensively researched in the 1970s.

Multi-purpose Pedal Powered Machines

Universal pedal powered machines did not exist at the turn of the twentieth century, although some combined a few functions (both sawing and drilling, for instance). At least five interesting inventions were designed and built in the 1970s: the Energy Cycle (by Dirk Ott), the Dynapod (by Alex Weir), the Human Powered Flywheel Motor (by JP Modak), the Pedal Power Unit (by David Weightman) and the Dual-Purpose Bicycle (by Job Ebenezer). All these concepts are also of interest for the construction of single-purpose pedal power units.

The Dynapod

After experimenting with single-purpose pedal powered machines in several countries in Africa, British engineer Alex Weir (who is also the promoter of this online low-tech database) built a multi-purpose 'Dynapod' (the name stemming from the Greek words for 'power' and 'foot') in Tanzania in the early 1970s. The power module, based on a 1968 concept by Stuart Wilson of Oxford University, came in a one-man and two-man version. The tandem unit doubled the power output, and at the same time evened out the power flow, with both sets of pedals placed out of phase.

The Dynapod was made using a custom-built frame. Apart from pedals, cranks and chain drives, the machine shared nothing with a bicycle. The first designs used wooden frames, while later versions were based on a steel frame. For a flywheel, Weir used an old bicycle wheel filled with cement. The cost of the wooden frame unit (in 1980) was $40 to $100, materials and labour included.

The Dynapod could drive pumps, corn grinders, winnowing machines, forge blowers, grinding machines, drilling machines, potter's wheels, paint sprayers, crop dusting equipment, cassave graters, coffee pulpers, grain hullers, fibre decorticators, threshers, balers, band saws, tire pumps and sewing machines. It could also be used to generate electricity.

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Apart from pedals, cranks and chain drives, these human powered machines share nothing with a bicycle

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To allow the operation of such a wide diversity of appliances, the Dynapod was equipped with multiple drives. It could be operated with a direct drive having a ratio of 1:1 (when a lot of torque was needed at a slow speed), a chain drive with a ratio of up to 3:1 (a compromise between torque and speed for operating grinders, threshers, etc.) or a belt drive with a ratio of up to 10:1 (for electrical generation, a winnowing fan, and other uses where high speeds were required). The machine was easily adapted from one drive to another. Multiple drives on pedal powered machines were not a novelty - some earlier pedal powered machines had them too.

The Energy Cycle

Rodale Press, the publisher of the 1977 book 'Pedal Power in Work, Leisure and Transportation' also had a research team - Rodale's Research and Development Department. Together with inventor Dick Ott they conceived their version of a universal pedal power unit, the 'Energy Cycle'.

 Just like the Dynapod, it was built from scratch and could accommodate a large number of detachable tools. These included kitchen aids (such as an egg beater, can opener, nut chopper, food grinder, fish skinner, meat and cheese slicer and a cherry pitter), farm machinery (including an irrigation water pump, feather plucker, potato digger, corn sheller, grain cleaner, rice polisher and oatmeal roller) and more general tools (like a wheel grinder, stone polisher, drill, wood carver and battery charger).

Several improved prototypes were built, first of iron, and then of steel. For the first upgrade of the design, a large work table was added to the unit which enabled the operator to perform numerous tasks without leaving his seat. Later versions were equipped with a flywheel. Experiments showed that the unit offered considerable benefits in comparison with hand powered machines or small horse power motors and engines. The main challenge remains in finding a universal means of attaching each implement to the Energy Cycle - which should be easily overcome if serious industrial research is dedicated to it.

Pedal Powered Winch: Substituting a Farm Horse or Tractor

Both the Dynapod and the Energy Cycle could also double up as a pedal powered winch, offering a whole new array of possibilities. A winch is useful for pulling, excavating, load lifting, or snow plowing. In agriculture, a winch can be utilized for cable-cultivation, a principle in which the motive power for plowing (or harrowing, cultivating, seeding and hay raking) is stationary and only the tool (attached to a multifunctional mobile tool carrier) moves across the field along a cable.

This agricultural method is based on steam cable plowing, which was the only mechanized method of agriculture for almost one hundred years. Cable-cultivation brings considerable savings in energy, because the motive power - be it human, animal or mechanical - does not have to waste power in moving itself over the soil. Additional advantages are the avoidance of soil compaction, a notable drawback of using a tractor, and the possibility to work on waterlogged ground and steep slopes.

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Cable-cultivation is a principle in which the motive power for plowing (or harrowing, cultivating, seeding and hay raking) is stationary and only the tool moves across the field along a cable.

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In a field left fallow for a year, the Energy Cycle pulled a plough through the grass and weed covered soil, successfully substituting the work of a farm horse or tractor. One person pedalled the winch that drew the plough through the soil while another guided it. It took the two presons about an hour to plow 1,500 square feet. The only difficulty was that the winch had the tendency to break or bend ordinary hand tools. Because of this problem, and because the Energy Cycle held so much promise as a garden and farm tool, the research team built a specialized pedal powered winch and special tools to be used with it.

This more compact unit - basically two pedals separated by a spool mounted on bearings, built into a frame which also supports the seat - was capable of pulling over 1000 lbs (453 kg) with average pedalling effort, amplifying human power by almost ten times. Together with a specially designed frame that could hold different attachments, it was successfully used for pulling, snow plowing, dislodging small stumps and pulling seeders, harrows and hay rakes.

Low gears were used for jobs requiring a slow, powerful pull, such as plowing through heavy soil. Second or high gears were used for easier jobs such as harrowing or cultivating. In order to be moved sideways so as to easily cultivate one row after the other, a pedal powered winch can be mounted on skids. The weight of the operator provides sufficient anchorage while in use.

Human Powered Flywheel Motor

An interesting variation on the multi-purpose pedal powered machine is the Human Powered Flywheel Motor (pdf) designed by J.P. Modak, an emeritus engineering professor from India. The remarkable feature of Modak's machine - which has been developed since 1979 - is that it can deliver much more power than the human who operates it.

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The human powered flywheel motor can deliver much more power than the person who operates it

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The machine system uses human energy and stores it in a flywheel at an energy-input rate convenient to the pedaller. After storing the maximum possible energy in the flywheel (pedalling time is 1 to 2 minutes), it is made available for the actuation of the process unit by the rapid release of the stored kinetic energy in the flywheel via a suitable clutch. The concept only works when the process can be of intermittent nature without affecting the end product.

The human powered flywheel motor was initially developed for the making of bricks for a housing authority in Mumbai, India. Since then, it has been successfully used for several rural-based production activities such as water lifting, algae formation processing, wood turning, winnowing, wood strip cutting, electricity generation and the operation of a smiths hammer. Processes needing up to 6 HP could be energised by the machine concept (although only one third of this has been achieved to date). This would be about 20 to 60 times more than what an average human can sustain either momentarily (300 watts) or for long periods (100 watts).

The energy unit consists of an existing bicycle frame which provides a seat and handle, a pair of speed-increasing gears, and a flywheel of about one metre in diameter. The transmission consists of a spiral clutch and a torque-amplification gear pair. For brick manufacturing in particular, the process unit consists of an auger, cone and die, conventionally used for motorized brick-extruders for the manufacture of clay bricks.

Combining Stationary and Mobile Pedal Power

A very different approach to multi-purpose pedal powered machines was followed by David Weightman. His concept (and prototype) was inspired by the Dynapod, but Weightman added one feature: the machine should still be usable for transportation. His Pedal Power Unit (PPU) was comprised of a bicycle wheel in forks fitted to a frame with a saddle. The unit could then be used independently to drive machinery via a power takeoff but could also be connected to a two-wheel chassis to form a load-carrying tricycle. Furthermore, the unit could be connected in series with other units for machine applications requiring more power. Weightman justified his concept by emphasising the close link between transport and machine use in agricultural and industrial production:

"In a typical agricultural growing cycle, seed and fertilizer are transported to the field, crops are grown and then processed by machinery, and then produce is transported to the market. Similar patterns can be seen in construction and small scale industrial production. The use of a pedal power unit in this dual purpose role is exactly analagous to the use of tractors in European agriculture as power sources and transport devices. The PPU is equally suitable as the Dynapod when operating a number of machines but is more economically feasible for an individual farmer due to its capability as a transport device."

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The Dual-Purpose Bicycle looks very similar to the electricity generators which are sold today, though it is aimed at mechanically driving multiple machines and producing electricity

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Job Ebenezer from the MGO 'Technology for the Poor' further developed this design, simplifying it greatly by substituting the tricycle for a bicycle. At first sight, his 'Dual-Purpose Bicycle' looks very similar to the electricity generating units which are sold today, though it is aimed at mechanically driving multiple machines and producing electricity.

The ingenious design, primarily for agricultural use, consists of a very small flywheel attached to a standard bicycle, which permits its use as a pedal-powered machine that can be utilized to power numerous small-scale mechanical devices such as grain threshers, grinders, winnowers, peanut shellers, corn shellers, circular saws, wood working lathes, water pumps, electrical generators, and a variety of small tools.

The contraption can be converted from the transportation mode to pedal power mode in a matter of minutes. The broad stand, which provides stability during power production, can be flipped upward during the transport mode and doubles up as a freight carrier. The power-generating device remains attached to the bicycle in transportation mode, so that it can be easily transported and used immediately. Of course, this pedal power unit is a compromise, but it is an interesting one.

Contrary to modern concepts, it has a small flywheel and it does not use a friction drive because of its low efficiency. During the prime-mover mode, the bike's regular chain is slipped off of the chain-wheel, and a custom chain to the power take-off mechanism is slipped on. Changing gear ratios is as simple as it is on a road bike. For driving more powerful devices, a larger flywheel can be placed between the power module and the process unit.  

Treadles

The many advantages of pedal powered machines don't make hand cranks or treadles obsolete. Not all devices need the extra torque of pedal power. Hand cranks and treadles can be a better option if power requirements are low or if power is only needed over a short period. A hand cranked device is much more compact than a pedal powered device. If hand control is required while operating low power equipment, treadles remain the best choice because they offer the operator more freedom of movement than pedals.

Of course, both mechanisms can also benefit from advantages in modern design and materials - including speed or torque increasing gears. A good example is the R2B2 kitchen unit by German designer Christoph Thetard (which is not for sale, unfortunately). It combines three kitchen appliances with a central driving unit. The heart of the unit is a treadle powered flywheel which works as an short-term energy storage (as in the Human Powered Flywheel Motor), capable of delivering up to 350 watts (of mechanical power) to the appliances. Similar to late 19th century machines, and contrary to today's kitchen devices, it is built to last.

Lowering the Costs and Energy Losses of Pedal Powered Electricity

Many modern machines and devices cannot be powered directly by mechanical energy. This is especially true for electronic equipment (such as computers, cell phones, televisions, routers, etc.) but it is also true for refrigerators and light bulbs. If we want to keep these modern comforts, we have to find a way to make pedal powered electricity more efficient. There are several ways to do this.

 1. Build a Generator from Scratch

Because it has few disadvantages, the best way to start is to build a pedal generator from scratch instead of using a bicycle on a training stand. This allows you to replace the friction drive by a more efficient drive, like a chain drive, and to add a flywheel.

Steel flywheels can be found on the most expensive exercise bicycles. However, a flywheel can also be cheap, low-tech and just as efficient when you are using a bicycle wheel filled with concrete or a wooden tabletop. The latter is used by the 'Pedal Powered Prime Mover' (PPPM) made by David Butcher, which is one of the few good examples of a pedal powered electricity generator built from scratch (the plans sell for $50 and the cost for the DIY version is estimated at $230). It consists of a steel frame made of steel shelving supports.

 Although the PPPM uses a friction drive, it is a rather efficient one because it is basically powered by a wooden tyre - the flywheel. Since higher tyre pressure increases the efficiency of a friction drive, a wooden wheel can be considered a bicycle wheel with optimal tyre pressure. Furthermore, the flywheel is powered directly by the pedals, eliminating the energy loss in chains and sprockets altogether (it is a 'direct drive' in other words). The only drawback of this method is that you can't change the gear ratio.

Butcher (who built his first machine in the seventies) claims an improved efficiency of 25 to 50% compared to a standard bicycle on a training stand. Interestingly, it can also power some devices via a direct mechanical connection: a water pump, a hammer, a masonry chisel, an air compressor and a hack saw. Building a pedal powered machine from scratch can thus offer you the best of both worlds.

2. Ditch the Electronics

 You can go much further in order to improve the efficiency of a pedal powered generator. In the most extreme case, you could skip the voltage regulator, the converter and the battery, which leaves you only with the energy loss of the generator. Or you can leave out either one of these devices.

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In the most extreme case, you could skip the voltage regulator, the converter and the battery, which leaves you only with the energy loss of the generator

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However, all these actions come with a price. If you do away with the converter, you need to replace the electrical devices you use. What you need, then, are DC-appliances like the ones you can plug in the interior of your car. While this can be an interesting option because of the high efficiency loss of a converter (25%), not all appliances come in a DC-variant (there are no DC-laptops, for instance*).

If you do away with the voltage regulator - and several of the pedal powered generators come without them - you have to carefully watch a multimeter while pedalling to make sure that the voltage does not exceed the capacity of the battery (or the device you are powering if you do away with the battery too). If not, you could destroy the battery (or the device, if you don't use a battery). A flywheel can be of great help here, because it smooths out not only the energy input (the alternating high and low force of a natural pedalling rhythm) but also the energy output, keeping the voltage relatively constant. 

3. Get rid of the Battery

 Doing away with the battery, or replacing it with a much more efficient and robust ultracapacitator, is probably the most rewarding thing you can do, not just in terms of efficiency, but also in terms of costs, reliability and - especially - sustainability. (Capacitators have a much longer service life than batteries, but a much lower energy density). However, you lose the advantage of generating energy and storing it for later use. In this case, you would have to pedal while using the device at the same time, as is the case with direct mechanical power transmission.

Whether or not this is convenient is dependent on what you want to use your generator for. If you mainly want to charge your laptop or cell phone, not having a battery to store the electricity isn't a problem since the devices themselves have a battery. However, if you want to light the staircase room or power a television, desktop computer, electric guitar or small fridge, this becomes rather awkward. If you want to play recorded music and dance, not using a battery would also be difficult.

 4. Build large-scale Pedal Power Plants

Improving the efficiency of pedal powered electricity generation becomes easier as you organise it on a larger scale. In most of the arts and education projects described earlier, like the BBC program or pedal powered concerts, no batteries are used. The key here is that it is not one person both generating and consuming power, but a large group of people, of whom some are producing electricity whilst others are consuming it.

In a similar fashion, electricity could be generated in large pedal powered electricity plants, and then distributed to houses, shops, public spaces and factories. This is more efficient than doing it in each house separately because you can do away with the batteries and still offer electricity 24 hours a day. Power plants would simply add more pedallers when demand is high (such as during peaks hours) and send them home when demand is low (at night, for instance).

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Pedal powered electricity plants could be a valuable backup solution to intermittent renewable energy sources

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Human powered electricity plants should avoid the transmission losses of today's extremely centralized power network. They should preferably be located in every neighbourhood or city district. In this scenario, it also becomes possible to do away with converters and switch the electricity distribution system from AC to DC, since the former was only chosen because it is more efficient to transport electricity over large distances. Of course, this is less plausible, since it means rewiring cities and replacing all devices.

The future of Pedal Powered Machines

If we boost the research on pedal powered technology - trying to make up for seven decades of lost opportunities - and steer it in the right direction, pedals and cranks could make an important contribution to running a post-carbon society that maintains many of the comforts of a modern life. The possibilities of pedal power therefore largely exceed the use of the bicycle.

Pedallers could power agriculture, factories, construction, mining and even other means of  transportation than bicycles: aerial ropeways, cable trains and trolleyboats. Pedal powered electricity plants could be a valuable backup solution to intermittent renewable energy sources, replacing coal, gas and nuclear as a base load power for when the sun and wind let us down. Human power is available 24 hours per day, is not affected by changes in the weather, is portable and can easily be stored for later use. Contrary to wind and biomass, it is an energy source that will never be depleted, since its potential keeps pace with population growth. Pedal power would also aid unemployment, leave us with a fit and healthy workforce, and produce a great deal of nice-looking bottoms.

The Limits of Pedal Power

Of course, pedal power can only make a difference if we drastically reduce energy consumption. While athletes can produce a power output of over 2,000 watts on a bicycle, they can only sustain this over a period of a few seconds. The power that can be delivered by the average person over a sustained period of time is much less impressive than that: 75 watts or 1 "hup". This unit of measurement (short for human power) was proposed in 1984, and tells us that an average person can sustain one hup for all day, 2 hups (150 watts) for roughly two hours, 3 hups (225 watts) for about 30 minutes and 4 hups (300 watts) only momentarily.

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The absence of self-produced cooling winds results in possible overheating of the body

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 Another reason not to be overly-optimistic about the energy output of stationary pedalling is the fact that a stationary pedaller does not need to overcome air resistance. This sounds like a good thing, because at higher speeds a cyclist spends most of his energy compensating for air resistance. However, air resistance also keeps the active human body from overheating.

It was found that the power output measured by ergometers (stationary bikes used to measure the power output of cyclists) is substantially lower than that produced by the same persons on the road because the absence of self-produced cooling winds, which results in possible overheating of the body (this is also a problem with velomobiles). A (self-propelled) fan could keep the stationary pedaller cool, but it is only a partial solution. As David Wilson notes in 'Bicycling Science': 

"The relative air flow generated by cycling is of such magnitude that it bears little resemblance to the drafts produced by the small electric fans often used for cooling people pedalling ergometers. At a speed of about 9m/s about 150 watts are dissipated into the air. Even if cooling fans of this power level were used [negating the power production by the pedaller, kdd], the cooling effect would be much less than that for the moving cyclist, because most of the fan power is dissipated as air friction in areas other than around the subject's body."

While body heat production might provide interesting side-effects in winter - you and even other people in a small room would not need heating - it would definitely limit the energy that can be delivered by pedal power. Pedalling outside when it's windy may help, but this is not always possible.

Wanted: 1.2 billion Pedallers for the UK

The main problem, however, lies in the demand for pedallers. To give you an idea, let's see how many people would be needed in order to use pedal power at a base load power plant. An average UK family consumes about 13 kWh of electricity per day (an American family would consume at least twice as much). If we consider a relatively small energy loss of 25% when converting human power to electricity, it would take 173 hours of pedalling at 100 watts (thus over one 'hup') in order to produce 75 Wh per hour. If we presume an electricity consumption that is evenly distributed over the course of 16 hours and no electricity consumption at night, this would take two shifts of ten people each pedalling non-stop for eight hours. And this concerns only residential electricity use.

If we consider total electricity consumption in the UK, each person needs 15.7 kWh per day, or two teams of ten people each pedalling non-stop for 8 hours. The UK would have to import a workforce of 1.2 billion people (a number equal to all the inhabitants of India) to pedal its way into energy independence, and prohibit all these people from using electricity themselves.

Here we are not even considering peaks in demand, but average consumption. And we are talking only about electricity consumption, not heating and transportation fuels. Of course wind and solar could help to diminish the need for base load pedal power. But when there is no sun or no wind, the power would have to be supplemented.

On the Other Hand/Foot

In other parts of the world, things are slightly different. If all Nepalese people could pedal two hours per day, the country would be entirely pedal powered, even without the support of other renewables. Interestingly, the NGO Ecosystems Nepal distributes pedal powered generators to Nepalese villages where they are used in a scenario somewhat similar to the one envisioned above. A village is equipped with one pedal power generator, which is pedalled for eight hours per day, charging large batteries.

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The main problem with our approach to pedal powered machines is that we compare them to fossil fuel powered machines and not to the inefficient human powered tools and machines that went before them.

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This village 'power plant' is then visited by the people living in the countryside in the surroundings of the village, who pass by once a month or so to charge their small motorcycle batteries. Even taking into account the considerable energy losses (in using batteries to charge batteries) one pedal generator provides enough electricity for 200 homes. This is possible because small batteries only need to power 0.2 watt led-lamps, enough to read a book. I am afraid that even my Kindle uses more than that, and it has no reading light.

Cranks and pedals are not a solution at all if we decide to cling to an energy-intensive lifestyle - but then, neither is any other renewable (or even non-renewable) energy source. The main problem with our approach to pedal powered machines is that we compare them to fossil fuel powered machines and not to the inefficient human powered tools and machines that went before them. This explains why pedal power is often laughed at in the western world but enthusiastically welcomed in the developing world, where, for instance, methods of agriculture still rely heavily on the use of human power using primitive tools which are usually inefficient. This is a scenario in which light is produced by dirty and inefficient kerosine lamps, or where there is no light at all.

Ironically, communities in the poorest countries in the world are developing into sustainable societies independent of fossil fuels, enjoying basic but modern comforts, while we continue to be ever more dependent on increasingly dirty, dangerous and diminishing energy sources.

Kris De Decker (edited by Deva Lee)

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MORE: THE SHORT HISTORY OF EARLY PEDAL POWERED MACHINES

The historical importance of pedal powered machines can be easily overlooked by people who grew accustomed to fossil fuels and ubiquitous electricity. It cannot be stressed enough how much of an improvement pedal power was in the light of thousands of years of human drudgery. Pedals and cranks make use of human power in a near-optimum way. Historically, the motions used to harvest human muscle power used inappropriate muscles moving against resistances which were too large at speeds which were too low. Read more.

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MORE: BIKE POWERED ELECTRICITY GENERATORS ARE NOT SUSTAINABLE

Pedalling a modern stationary bicycle to produce electricity might be a great work-out, but in many cases, it is not sustainable. While humans are rather inefficient engines converting food into work, this is not the problem we want to address here. People have to move in order to stay healthy, so we might as well use that energy to operate machinery. The trouble is that the present approach to pedal power results in highly inefficient machines. Read more.

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MORE: FULL PLANS FOR A PEDAL POWERED JUICE EXTRACTOR

What happens when two industrial design students from Sweden end up in Kenya creating a pedal powered machine for small-scale farmers who are often illiterate and speak more than 60 languages? You get a do-it-yourself design that seems to have come out of the IKEA factories - pictoral manuals included.

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Sources (in order of importance)

• "Pedal Power in Work, Leisure and Transportation", edited by James McCullagh, Rodale Press, 1977. Still the best resource on pedal powered machines.
• "The Human-Powered Home: Choosing Muscles Over Motors", Tamara Dean, New Society Publishers, 2008. Very good book on human powered machines, both hand and foot powered. Includes half a dozen plans to convert bicycles into stationary pedal powered machines.
• "Bicycling Science", Third Edition, David Gordon Wilson, 2004
• "The Dynapod: a pedal power unit" (pdf), Alex Weir, 1980. More here.
• "The use of pedal power for agriculture and transport in developing countries" (pdf), David Weightman, Lanchester Polytechnic, 1976
• "Design of a human-powered utility vehicle for developing communities", Timothy J. Cyders, 2008
• "Supplement, Energy for rural development", National Research Council, 1981
• "Tales from the Blue Ox ", Dan Brett, 2003
• "Bicycles and tricycles", Archibald Sharp, 1896
• "In search of the massless flywheel" (pdf), John S. Allen, Human Power (Fall/Winter 1991-1992)
• "Design and development of a human-powered machine for the manufacture of lime-flyash-sand bricks", J.P.Modak & S.D.Moghe, Human Power (Spring 1998)
• "Human Powered Flywheel Motor: concept, design, dynamics and applications", J.P.Modak, 2007
• "Modern mechanism: exhibiting the latest progress in machines, motors, and the transmission of power", Benjamin Park, 1892
• "Make electricity while you exercise", Mother Earth News, 2008
• "Luther's tool grinders" (pdf, 5.8 MB), hand and foot powered grinders catalog. Hosted at Toolemera Blog.
• "Woodworkers' tools and machines" (pdf, 29 MB), product catalogue no.25, 1884, Richard Melhuish Ltd., Tool and Machine Merchants, London. Hosted at Toolemera Blog.
• "Science & civilisation in China, Vol.5, Part 9", Joseph Needham, 1988

Related articles:

• Hand powered drilling tools and machines
• Human powered cranes and lifting devices: the sky is the limit
• Wind powered factories: the history and future of industrial windmills
• The bright future of solar powered factories: we need a renewable source of heat energy
• The velomobile: high-tech bike or low-tech car?
• Cars, out of the way: what you mean, bike lanes?
• The industrialization of traffic: why bicycles are faster than cars
• Computing without electricity: mechanical calculators
• The museum of old techniques
• Wind up your laptop
• Automata: engineering for a post-oil world?
• Life before television
• Build your own pedal powered machines: overview
• Short posts on pedal power can be found at No Tech Magazine

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Pedalling a modern stationary bicycle to produce electricity might be a great work-out, but in many cases, it is not sustainable. While humans are rather inefficient engines converting food into work, this is not the problem we want to address here; people have to move in order to stay healthy, so we might as well use that energy to operate machinery. The trouble is that the present approach to pedal power results in highly inefficient machines.

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When operating a bicycle generator you are basically pedalling to produce the energy required to manufacture the battery.

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There are two ways to power a device by pedalling. You can power it directly through a mechanical connection - as was the case with all pedal powered machines for sale at the turn of the 20th century. Or, you can pedal to generate electricity, which is then used to power the device. In the 1970s, most research was aimed at direct mechanical power transmission. Today, the interest in pedal powered machines is almost exclusively aimed at generating electricity, for instance for charging cell phones and laptops - products that did not even exist in the 1970s.

With one exception (the 'Fender Blender', a pedalled powered machine to make smoothies), the only pedal powered machinery that is now commercially available in the western world (offered by Windstream, Convergence Tech and Magnificent Revolution) are stands to fit your bike to, connected to an electric motor/generator and a battery - a combination that can quickly convert your regular road bicycle into an electricity generator. These are also the pedal powered machines which are used for educational and arts projects, like powering a music concert, a cinema projection or a supercomputer, or teaching kids the difference in energy use between, for instance, an incandescent light bulb and an energy saving lamp.

In an effort to raise awareness about energy use and global warming, the BBC even made a TV-programme in which an entire household was powered via these generators, with 80 cyclists generating up to 14 kW. These multi-person pedal power generators were pioneered in the 1970s by the Campus Center for Appropriate Technology (CCAT).

Generating electricity is very inefficient

There are several problems with the present-day approach to pedal power. First of all, it is important to know that generating electricity is far from the most efficient way to apply pedal power, due to the internal energy losses in the battery, the battery management system, other electronic parts, and the motor/generator.

These energy losses add up quickly: 10 to 35 percent in the battery, 10 to 20 percent in the motor/generator and 5 to 15 percent in the converter (which converts direct current to alternate current). (Sources: 1/2/3). The energy loss in the voltage regulator (or DC to DC converter, which prevents you from blowing up the battery) is about 25 percent (sources: 1/2).

This means that the total energy loss in a pedal powered generator will be 42 to 67.5 percent (calculation example for highest loss: 100 watt input = 80 watt after 20% loss in motor/generator = 57.5 watts after 25% energy loss in voltage regulator = 37.5 watts after 35% loss in battery = 32.5 watts after 15% loss in converter = 32.5 watts output = efficiency of 32.5% or energy loss of 67.5%).

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You have to pedal 2 to 3 times as hard or as long if you choose to power a device via electricity compared to powering the same device mechanically

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Furthermore, there will be an additional slight loss as the battery stands idle, and the charge efficiency (also known as "charge acceptance" or "coulombic efficiency") of the battery will deteriorate over time. And to make the calculation complete, you should actually also include the energy loss in the electrical device that you are powering (we won't do that here).

An energy loss of 42 to 67.5 percent of naturally means that it takes 42 to 67.5 percent more effort or time to power a device (say, a blender) via electricity compared to powering the same device mechanically. This can be considered an acceptable loss if you are using solar panels or a wind turbine connected to a battery as an energy source, but it becomes rather problematic when you have to deliver the energy yourself.

If you produce 100 watts of power and 42 to 67.5 percent is lost in the conversion, there is only 32.5 to 58 watts left to power the device. If you power the same device mechanically, you deliver 100 watts straight to it. You thus have to pedal 2 to 3 times as hard or as long if you choose to take the intermediate step of generating electricity and storing it in a battery.

Traditional bicycles were not made to generate stationary power

It does not stop here. The second problem with the present approach to pedal power is that it uses a traditional bicycle on a training stand instead of a pedal powered machine built from scratch - as was the case at the end of the 19th century. Of course, using a traditional bicycle has its advantages, but again it should be realized that this approach is considerably less efficient.

One reason is the use of a so-called friction drive - the rear bicycle wheel acts upon the small roller of the motor/generator. While chain and belt drives (used in late 19th century pedal powered machines) have an efficiency of up to 98 percent, a friction drive is only 80 to 90 percent efficient (and wears much faster). This energy loss should be added to the 42 to 67.5 percent efficiency loss calculated above, which rises to 48 to 73.5 percent. Low tyre pressure will further decrease efficiency.

It should be noted that there is also energy loss in the bicycle itself: your pedals are not attached to the rear wheel itself. You turn a sprocket, which turns a chain, which turns a sprocket, which turns the rear wheel. So, on top of the efficiency loss of the friction drive should be added the efficiency loss of a chain drive (plus the energy loss in the derailleur, if your bike has one).

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Additional energy losses occur when using a racing bike or a mountain bike

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Connecting a bike chain directly to the generator would prevent the energy loss of the friction drive, but it implies that you have to adapt the bicycle - destroying the whole concept of today's commercially available pedal generators.

Racing bicycles

Additional energy losses can occur when using a road bicycle to generate electricity. For example, the picture accompanying the Windstream generator shows a racing bicycle. This is a very bad choice, because the position of a rider on a racing bike is aimed to reduce wind resistance. Tests on ergometers (stationary bikes used to measure the power output of cyclists) have shown that pedalling in such a position is only about 80 percent as effective compared to a normal upright position, again resulting in considerable energy loss.

On the road the rider position on a racing bicycle is beneficial because of the large importance of air resistance. However, on a stationary pedalling machine this position has no advantage whatsoever. The popular mountain bike is equally disadvantageous because of the corrugated tyres, which of course lower the efficiency of the friction drive. In short, while using a road bicycle to generate electricity has the advantage that you can use your own bike, this does not mean you can use just any bike.

Flywheel

Another important drawback of using a common road bicycle is the absence of a flywheel - a heavy disc made of concrete, wood or steel that continues to generate power after it has been put in motion. In a pedal powered machine built from scratch, like the ones used at the turn of the 20th century, the flywheel applies the function of the rear bicycle wheel in the training stand (although the flywheel is mostly placed at the front of the machine). The pedaller powers the flywheel, and the flywheel powers the machine (which can be a mechanical device or a motor/generator to produce electricity). 

Why is a flywheel advantageous? Because there is an important difference between riding a bicycle on the road and pedalling a stationary machine. If we are pedalling, the power exerted by our feet on the pedals is inconsistent. It peaks every 180 degrees of crank rotation, and because the two cranks are placed 180 degrees out of phase this results in two power peaks per turn of the crank. Similarly, there are dead spots in between at the top and bottom position of the pedals (to be correct this minimum torque is not zero but about one third of the maximum).

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On a stationary bicycle without a flywheel, the natural pedalling rhythm results in jerky motion, limiting the energy output of the rider

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On a bicycle, this uneven exertion has little effect because of the inertia of both bike and rider. But on a stationary pedal powered machine, this natural pedalling rhythm results in jerky motion and additional stress on parts.

Because of its large mass and rotational speed, the flywheel evens out the difference between power peaks and dead spots. Evening out the power input means that the rider tires less quickly and can thus generate more power. The obvious disadvantage of a flywheel is that it is heavy - from 10 to 80 kg for stationary pedal powered machines - and thus not exactly mobile.

Generating electricity is not eco-friendly

Generating electricity is not only ineffiicient, it also makes pedal power less sustainable, less robust and more costly. To begin with, batteries have to be manufactured, and they have to be replaced regularly. This requires energy, which can completely negate the ecological advantage of pedal power.

According to this research paper (pdf), the embodied energy of a 150Wh lead-acid battery (like the one offered with the Windstream pedal power generator) is at least 37,500 Wh, which equals 250 full charges of the battery (more sources: 1/2). In other words: if you can deliver 75 watts of power to the battery, you have to pedal for 500 hours in order to generate the energy that was needed to manufacture the battery. Because the life expectancy of a lead-acid battery can be as low as 300 discharge/charge cycles (sources: 1/2), you are basically pedalling to produce the energy required to manufacture the battery. If you also factor in the embodied energy of other electronics and parts, the ecological advantage of a pedal powered generator connected to a battery becomes rather doubtful. It might costs more energy than it delivers.

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A pedal powered generator might cost more energy than it delivers

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Of course, it also takes energy to manufacture a pedal powered machine that does not take the intermediate step of generating electricity. This concern lies mainly with the production of steel, and quite a lot of it. The commercially available Fender Blender mentioned earlier weighs 25kg (55 pounds).

If made from recycled steel, and using these figures to calculate the embodied energy of steel, this comes down to an energy cost of at least 41,625 Wh, slightly more than the battery needed for the electricity generator. If freshly made steel is used, the embodied energy is at least 138,750 Wh (3.7 times the embodied energy of a single battery). However, these machines can last at least 100 years (pedal powered machines surviving from the late 19th century are still in use), while the battery of the electricity generator has to be replaced every few years.

If we ignore the embodied energy of other parts than the battery (both training stand and electronics), and take a life expectancy of 4 years for the battery (rather optimistic), a pedalled powered generator would require an embodied energy of 937,500 Wh over the course of 100 years - 6.7 to 22.5 more than a mechanical unit. Moreover, it is easy to make the frame for a mechanical pedal powered machine from scavenged materials, bringing the embodied energy down to almost zero, while this is an impossibility for the batteries. Never mind that in addition, the toxicity of the materials is another thing to consider.

Generating electricity is less robust and more expensive

While a pedal powered machine is the most robust and resilient energy source around if you power devices mechanically, this advantage is lost when you start generating electricity. Few people can manufacture batteries themselves, so you remain dependent on a regular supply of replacement batteries.

Furthermore, the electronic parts of the machine (voltage regulator, motor/generator, converter) can break down and are not easy to make or repair yourself either - contrary to old-fashioned pedal powered machines, which can be fixed yourself with readily available materials. Mechanical pedal powered machines are generally even easier to repair and maintain than bicycles.

The extra components also make pedal generators more expensive. The commercially available models sell for $700 to more than $1000, not including the necessary replacements of the battery over time. Even if you make your own pedal power generator, the costs add up. The 2008 book 'The Human-Powered Home: Choosing Muscles Over Motors', which has plans for several kinds of pedal powered machines, estimates the costs of a DIY generator at about $50 (using scavenged parts) to $350 (using new parts), not including a bicycle stand and replacement batteries. Another source estimates the cost at $600.

The mechanical pedal powered machines in the book can be built for $10 to $50 (the washing machine being more expensive at $100), everything included. While the only commercially available mechanical pedal powered machine today is very expensive too (the Fender Blender sells for $1,700), the high cost is almost entirely due to the steel frame - which, as mentioned, could easily be replaced by the frame of an old exercise bike, or built oneself from scavenged materials. Moreover, there are no additional costs for replacement batteries and the machine is built to last for a very long time.

Continue reading: How to make pedal power efficient and sustainable?

One way to solve the large energy losses of pedal power generators is not to produce electricity at all and power devices mechanically, whenever possible. Another way - the only way for devices that cannot be powered via a direct mechanical connection because they do not rely on rotary motion - is to make the generation of electricity more efficient.

This can be done by building a pedal powered generator from scratch instead of using a road bicycle, and/or by ditching one or several electronic components in the power transmission chain. All approaches can be combined, resulting in a pedal power unit that can power a multitude of mechanical devices and generate electricity comparatively efficiently. Read more.

Kris De Decker (edited by Shameez Joubert)

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Sources (in order of importance)

• "Pedal Power in Work, Leisure and Transportation", edited by James McCullagh, Rodale Press, 1977. Still the best resource on pedal powered machines.
• "The Human-Powered Home: Choosing Muscles Over Motors", Tamara Dean, New Society Publishers, 2008. Very good book on human powered machines, both hand and foot powered. Includes half a dozen plans to convert bicycles into stationary pedal powered machines.
• "Bicycling Science", Third Edition, David Gordon Wilson, 2004
• "The Dynapod: a pedal power unit" (pdf), Alex Weir, 1980. More here.
• "The use of pedal power for agriculture and transport in developing countries" (pdf), David Weightman, Lanchester Polytechnic, 1976
• "Design of a human-powered utility vehicle for developing communities", Timothy J. Cyders, 2008
• "Supplement, Energy for rural development", National Research Council, 1981
• "Tales from the Blue Ox ", Dan Brett, 2003
• "Bicycles and tricycles", Archibald Sharp, 1896
• "In search of the massless flywheel" (pdf), John S. Allen, Human Power (Fall/Winter 1991-1992)
• "Design and development of a human-powered machine for the manufacture of lime-flyash-sand bricks", J.P.Modak & S.D.Moghe, Human Power (Spring 1998)
• "Human Powered Flywheel Motor: concept, design, dynamics and applications", J.P.Modak, 2007
• "Modern mechanism: exhibiting the latest progress in machines, motors, and the transmission of power", Benjamin Park, 1892
• "Make electricity while you exercise", Mother Earth News, 2008
• "Luther's tool grinders" (pdf, 5.8 MB), hand and foot powered grinders catalog. Hosted at Toolemera Blog.
• "Woodworkers' tools and machines" (pdf, 29 MB), product catalogue no.25, 1884, Richard Melhuish Ltd., Tool and Machine Merchants, London. Hosted at Toolemera Blog.
• "Science & civilisation in China, Vol.5, Part 9", Joseph Needham, 1988

Related articles:

• Hand powered drilling tools and machines
• Human powered cranes and lifting devices: the sky is the limit
• Wind powered factories: the history and future of industrial windmills
• The bright future of solar powered factories: we need a renewable source of heat energy
• The velomobile: high-tech bike or low-tech car?
• Cars, out of the way: what you mean, bike lanes?
• The industrialization of traffic: why bicycles are faster than cars
• Computing without electricity: mechanical calculators
• The museum of old techniques
• Wind up your laptop
• Automata: engineering for a post-oil world?
• Life before television
• Short posts on pedal power can be found at No Tech Magazine
• Full plans for a pedal powered juice extractor

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Ever since the arrival of fossil fuels and electricity, human powered tools and machines have been viewed as an obsolete technology. This makes it easy to forget that there has been a great deal of progress in their design, largely improving their productivity.

The most efficient mechanism to harvest human energy appeared in the late 19th century: pedalling. Stationary pedal powered machines went through a boom at the turn of the 20th century, but the arrival of cheap electricity and fossil fuels abruptly stopped all further development.

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The historical importance of pedal powered machines can be easily overlooked by people who grew accustomed to fossil fuels and ubiquitous electricity

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Hand cranks, capstans & treadwheels

Rotary motion has been the fundamental mechanism of most machines throughout human history. There have been several important innovations in applying human power to rotary motion, many of which already appeared in Antiquity: the bow (see the article on human powered drilling tools), the hand crank, the capstan and the treadwheel (these are described in more detail in the article on human powered cranes). Successively, each of these brought an improved mechanical advantage, being the factor by which the mechanism multiplied the human (or sometimes animal) input force into an higher output force.

A hand crank had a mechanical advantage of about 2 to 1, meaning that the mechanism doubled the effort of the user. With a capstan, the mechanical advantage went up to about 6 to 1. A typical treadwheel, which had a diameter of at least 4 metres, had a mechanical advantage of about 14 to 1. This meant that a person walking a treadwheel could exert 7 times more 'torque' (the force to rotate an object about an axis) than a person operating a hand crank. Or, that a person could generate the same amount of torque with 7 times less effort.

The treadwheel had another advantage over the hand crank: it replaced the use of the arm muscles by the use of the much stronger leg muscles, and it allowed the use of two limbs instead of one. The same effort could thus be sustained over a longer time - or a higher force could be exerted over the same time. To a lesser extent, the same advantage was valid for the capstan, where the legs did a large part of the work.

Treadles

Another novelty appeared in the Middle Ages: the treadle. From the 10th century onwards, the Chinese used wooden treadles to obtain continuous motion for water pumps, textile machinery and wood saws. In the western world, treadles were mainly applied to spinning wheels and lathes (machine tools used for working metal and wood).

Treadles were inefficient compared to capstans and treadwheels (feet and legs must be accelerated and subsequently decelerated by the muscles) but they were more compact and a viable alternative when power requirements were low. Their main advantage over the hand crank was that they left both hands free to control the machine.

 A boom of pedal powered machines

 The cleverest innovation in applying human power to rotary motion only appeared in the 1870s. Some of us still use it as a means of transportation, but it is rarely applied to stationary machines anymore: pedal power. Initially, pedals and cranks were connected directly to the front (or sometimes rear) wheel. With the arrival of the 'safety bicycle' shortly afterwards, this direct power transmission was replaced by a chain drive and sprockets - still the basics of most present-day bicycles. Pedal power did not come out of the blue: some of the first bicycles were equipped with treadles, which could be considered the predecessor of the pedal.

On their own, pedals and cranks did not offer a better mechanical advantage than the hand crank, let alone the capstan or the treadwheel. What made pedal power so revolutionary was that it offered the possibility to use the stronger leg muscles in a continuous motion while at the same time offering a much more compact mechanism than the capstan or the treadwheel. 

Moreover, using the appropriate gear ratio (using chains and sprockets of different sizes) a mechanical advantage similar to that of a capstan or a treadwheel could be achieved (multiplying torque at the expense of speed or vice versa). This made pedal power suitable for a much larger variety of applications.

From 1876 onwards, pedals and cranks were attached to tools like lathes, saws, grinders, shapers, tool sharpeners and to boring, drilling and cutting machines. These machines - which became very popular - were intended for small workshops and households without electricity or steam power. They were made with heavy cast-iron bodies that could be collapsed for shipping.

Pedals and cranks did not make treadles and hand cranks obsolete. On the contrary, these tools became more sophisticated (made of steel instead of wood, for example, or using gears inspired by bicycles) and became increasingly popular for low or brief  power applications.

Steel treadles were applied to industrial machines like hat, broom, cigar and hook making machines, printing presses, punch machines and riveting machines. The farm saw the appearance of foot powered harvesters, treshers, milking machines and vegetable bundlers. The late 19th century dentist used a treadle powered drill.

Ending human drudgery

The historical importance of pedal powered machines can be easily overlooked by people who grew accustomed to fossil fuels and ubiquitous electricity. Therefore, it cannot be stressed enough how much of an improvement pedal power was in the light of thousands of years of human drudgery. Pedals and cranks make use of human power in a near-optimum way.

The circular pedalling motion mainly activates the thigh muscles or quadriceps which are the largest and most powerful muscles in the human body. Furthermore, using the appropriate gearing, pedals and cranks make use of these muscles at an optimal speed: about 60 to 90 revolutions per minute. Research in the twentieth century has shown that muscles develop maximum power when they are contracting quickly against a small resistance.

Historically, the motions used to harvest human muscle power used inappropriate muscles moving against resistances which were too large at speeds which were too low. While human powered capstans and treadwheels were much more efficient, their use was limited because of their sheer size (and especially in the case of treadwheels, their high costs).

In the 1977 book Pedal Power in Work, Leisure and Transportation', David Wilson explains three ways in which the application of human muscle power could fall short of the optimum:

"First, the wrong muscles could be involved. We find time and time again that people were called upon to produce maximum power output, for instance in pumping or lifting water from a well or ditch, using only their arm and back muscles. Second, the speed of the muscle motion was usually far too low. People were required to heave and shove with all their might, gaining an occasional inch or two. A modern parallel would be to force bicyclists to pedal up the steepest hills in the highest gears, or to require oarsmen to row boats with very long oars having very short inboard handles. Third, the type of motion itself, even if carried out at the best speed using the leg muscles, could be nonoptimum in a rather abstruse way."

Good examples of the misuse of human muscle power throughout history were large human powered rowing boats, as well as most farm work. In the third edition of 'Bicycling Science', the same David Wilson writes:

"The muscle actions used by these unfortunate oarsmen were typical of those considered appropriate in the ancient world. The hand, arm and back muscles were used the most, while the largest muscles in the body - those in the legs - were used merely to provide props or reaction forces. (They didn't have the sliding seat of today's competitive rowers). The motion was generally one of straining mightily against a slowly yielding resistance. With five men on the inboard end of a sweep, the one at the extreme end would have a more rapid motion than the one nearest to the pivot, but even the end man would probably be working at well below his optimum speed. Most farm work and forestry fell into the same general category. Hoeing, digging, sawing, chopping, pitchforking, and shoveling all used predominantly the arm and back muscles with little useful output from the leg muscles. In many cases, the muscles had to strain against stiff resistances."

Pedal power is a product of the industrial revolution

All these actions - and many more - could have been made much more efficient using pedals and cranks, making the life of people in Antiquity and medieval times much easier. However, no matter how simple it seems to us today, pedal power could not have appeared earlier in history. Pedals and cranks are products of the industrial revolution, made possible by the combination of cheap steel (itself a product of fossil fuels) and mass production techniques, resulting in strong yet compact sprockets, chains, ball bearings and other metal parts.

Prior to that time, the available materials were not strong enough to take the large force that was acted upon them. This is even truer for stationary pedal power than for road bicycles, because the strain on parts is considerably larger. Experiments in the 1970s designing pedals, cranks and bearings for stationary pedal power units using pre-industrial materials like wood failed. And while the frame of a pedal powered machine can be made of wood or bamboo, steel is a better option - contrary to road bicycles, a lightweight frame is not an advantage for a stationary machine.

It is important to realise that pedal powered machines (and bicycles) require fossil fuels. If we burn up all fossil fuels driving cars, we won't be able to revert to bicycles, we will have to walk. If we burn up all fossil fuels making electricity to drive our appliances, we won't be able to revert to pedal powered machines, but to the drudgery that went before them.

And yet, this is what we are heading to. In spite of the many advantages of pedals and cranks, the heydays of pedal power were over fast - shortly after the arrival of the combustion engine and the electric motor. Even though pedal powered machines were designed to operate for 100 years or more, most were scrapped for metal during World War One & Two. The Barnes Company, one of the most famous manufacturers, began turning away from foot powered tools in the 1920s and stopped producing them altogether in 1937.

The revival of pedal powered machines

Pedal powered machines resurged in the 1970s, together with the bicycle, following the first oil crisis (the pedal powered gas pump being an iconic example). Because the further development of stationary pedal powered machines had been halted for more than 5 decades, there was a lot of work ahead in order to modernize the technology.

 Several individuals and organisations experimented with a new generation of pedal powered machines. Although their efforts did not result in commercially available machines, a great deal of progress was made. The applications of pedal power were extended to include almost every possible machine. Moreover, several inventors designed and build universal pedal power units, which could be used to drive a wide range of tools and machines (see part 3: "Pedal powered farms and factories: the forgotten future of the stationary bicycle").

Unfortunately, the interest in pedal powered machines waned again after the oil crisis, largely halting research for another two decades. The second revival of pedal powered machines began halfway the 1990s when concerns over global warming and peak oil came to the fore, and continues today.

However, the present interest in stationary pedal power differs considerably from all earlier efforts: it is largely aimed at generating electricity, which is not an efficient way to harness pedal power. Furthermore, the lessons learned during the late 1800s and during the 1970s seem to have been forgotten, resulting in far from optimal machines that do not harvest the full potential of pedal power and - worse - have a doubtful ecological advantage (see part 2: "Bike powered electricity generators are not sustainable").

Kris De Decker (edited by Shameez Joubert)

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Sources (in order of importance)

• "Pedal Power in Work, Leisure and Transportation", edited by James McCullagh, Rodale Press, 1977. Still the best resource on pedal powered machines.
• "The Human-Powered Home: Choosing Muscles Over Motors", Tamara Dean, New Society Publishers, 2008. Very good book on human powered machines, both hand and foot powered. Includes half a dozen plans to convert bicycles into stationary pedal powered machines.
• "Bicycling Science", Third Edition, David Gordon Wilson, 2004
• "The Dynapod: a pedal power unit" (pdf), Alex Weir, 1980. More here.
• "The use of pedal power for agriculture and transport in developing countries" (pdf), David Weightman, Lanchester Polytechnic, 1976
• "Design of a human-powered utility vehicle for developing communities", Timothy J. Cyders, 2008
• "Supplement, Energy for rural development", National Research Council, 1981
• "Tales from the Blue Ox ", Dan Brett, 2003
• "Bicycles and tricycles", Archibald Sharp, 1896
• "In search of the massless flywheel" (pdf), John S. Allen, Human Power (Fall/Winter 1991-1992)
• "Design and development of a human-powered machine for the manufacture of lime-flyash-sand bricks", J.P.Modak & S.D.Moghe, Human Power (Spring 1998)
• "Human Powered Flywheel Motor: concept, design, dynamics and applications", J.P.Modak, 2007
• "Modern mechanism: exhibiting the latest progress in machines, motors, and the transmission of power", Benjamin Park, 1892
• "Make electricity while you exercise", Mother Earth News, 2008
• "Luther's tool grinders" (pdf, 5.8 MB), hand and foot powered grinders catalog. Hosted at Toolemera Blog.
• "Woodworkers' tools and machines" (pdf, 29 MB), product catalogue no.25, 1884, Richard Melhuish Ltd., Tool and Machine Merchants, London. Hosted at Toolemera Blog.
• "Science & civilisation in China, Vol.5, Part 9", Joseph Needham, 1988

Related articles:

• Hand powered drilling tools and machines
• Human powered cranes and lifting devices: the sky is the limit
• Wind powered factories: the history and future of industrial windmills
• The bright future of solar powered factories: we need a renewable source of heat energy
• The velomobile: high-tech bike or low-tech car?
• Cars, out of the way: what you mean, bike lanes?
• The industrialization of traffic: why bicycles are faster than cars
• Computing without electricity: mechanical calculators
• The museum of old techniques
• Wind up your laptop
• Automata: engineering for a post-oil world?
• Life before television
• Short posts on pedal power can be found at No Tech Magazine
• When low-tech goes IKEA: full plans for a pedal powered juice extractor

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