Muscles, wood, water and wind: energy before fossil fuels: Animals, water and wind: the first prime movers beyond the body

3.1 Draught animals gave several times human power, if harnessed well and fed

Oxen were the first great draught animals: slow, patient and strong, delivering about 250 to 400 W. Water buffalo suited the flooded rice paddies of Asia. Horses are faster and stronger, typically 500 to 800 W. James Watt later set his horsepower at 33,000 foot-pounds per minute, about 745.7 W, close to what a good working horse could sustain.

Getting that power into a plough or a cart depended on equipment. The ancient throat-and-girth harness pressed on a horse's windpipe, so the harder it pulled the more it choked. The breast-strap harness and then the padded collar, both first used in China and adopted in Europe around the turn of the first millennium, rest on the shoulders and let the horse pull with its full strength. Iron horseshoes protected hooves on wet northern soils and hard roads. In England, horses were only about 5% of the draught animals on manorial estates at the Domesday survey of 1086; over the following centuries, with collars and shoes, they came to dominate.

Animals carry a land cost. A working horse needs not only hay but grain to work hard, and the feed from one to two hectares a year. Every extra horse took land from food for people. Oxen ate coarser feed and were cheaper to keep but did less work.

The peak of animate power came late, in the grain lands of 19th-century North America and Australia. Smil cites a team of 40 horses pulling a California combine harvester in 1885, which delivered about 28 kW, roughly the output of a small modern car engine. That was close to the practical ceiling: beyond a few dozen animals, the driver could not control the team.

• Smil, Energy and Civilization: A History (2017) · via Smil Mastery Course, M4 'Prime movers: muscles and animals'
• Smil, Energy in World History (1994) · via Smil Mastery Course, M4 'Prime movers: muscles and animals'
• Smil, Energy in Nature and Society: General Energetics of Complex Systems (2008) · via Smil Mastery Course, M4 'Prime movers: muscles and animals'

3.2 Waterwheels were the first inanimate prime movers and ran Europe's early industry

Waterwheels turned the potential energy of flowing or falling water into rotation. There were three basic designs. The horizontal or Norse wheel, with its paddles in a fast stream, drove a millstone directly above it without gears. The undershot wheel was pushed by the current against paddles at its bottom and captured only a small share of the water's energy. The overshot wheel received water at the top into buckets and turned under its weight. It needed a dam and channel to give a head of water, but good designs reached 60 to 70% efficiency.

Water mills spread widely. The Domesday Book of 1086 recorded 5,624 mills in southern and eastern England, about one for every 350 people. Most medieval wheels delivered only 1 to 5 kW, but that was the work of dozens of people, available day and night.

To get more power, builders lined up wheels. The Roman complex at Barbegal near Arles had 16 overshot wheels in two rows down a hillside, each of about 2 kW, together just over 30 kW. No other site from antiquity is known to have gathered so much mechanical power in one place. Large schemes could also disappoint. Louis XIV's Machine de Marly, built in the 1680s with 14 wheels 12 m across, lifted water from the Seine towards Versailles. The site had a potential of about 750 kW but delivered only around 60 kW of useful power.

Uses spread far beyond grinding grain: fulling cloth, sawing timber, crushing ore, pumping water from mines, making paper and, crucially, driving the bellows and hammers of ironworks. Early textile mills of the industrial revolution in England and New England ran on water. In 1832 Benoit Fourneyron built the first practical water turbine; the later Francis and Pelton turbines became the heart of hydroelectric stations.

• Smil, Energy and Civilization: A History (2017) · via Smil Mastery Course, M4 'Water wheels'
• Smil, Energy in World History (1994) · via Smil Mastery Course, M4 'Water wheels'
• Smil, Growth: From Microorganisms to Megacities (2019) · via Smil Mastery Course, M4 'Water wheels'

3.3 Windmills turned an unreliable flow into work where water was scarce or flat

Windmills spread in Europe from the 12th century. The earliest were post mills, in which the whole wooden body, sails and machinery were turned on a central post to face the wind. Tower mills followed, with a fixed stone or brick tower and a rotating cap carrying the sails; the Dutch smock mill used a lighter timber tower. Asia had its own designs, including Persian vertical-axis mills.

Their useful power was modest. In 1866 the engineer William Rankine estimated post mills at 1.5 to 6 kW and tower mills at 4.5 to 10.5 kW. The wind's power rises with the cube of its speed, so a large 18th-century tower mill with sails 20 m across, in a 10 m/s wind, had about 190 kW of wind passing through its sweep. Even at the 20 to 30% that good traditional sails achieved, that is only some 40 to 55 kW at the sails (calculated), and after the losses of wooden gearing far less reached the millstones, which is why Rankine's figures are so much lower.

Physics sets a ceiling. The Betz limit shows that no rotor can capture more than 16/27, about 59%, of the wind's kinetic energy, because the air must keep moving to leave the rotor. Traditional mills managed perhaps 20 to 30%; modern turbines reach 45 to 50%.

The Dutch made the most of wind. Thousands of mills pumped water out of polders, reclaiming land from the sea and lakes, and powered sawmills that supplied the shipyards of the 17th-century Dutch Republic. On the American Great Plains after 1850, millions of small multi-bladed farm windmills, each giving only 30 W to 1 kW, pumped groundwater for cattle and homesteads and made settlement of dry land possible. These are the ancestors of the Small, airborne and traditional wind tile.

• Smil, Energy and Civilization: A History (2017) · via Smil Mastery Course, M4 'Wind: mills and sails'
• Smil, Energy in World History (1994) · via Smil Mastery Course, M4 'Wind: mills and sails'
• Smil, Energy in Nature and Society: General Energetics of Complex Systems (2008) · via Smil Mastery Course, M4 'Wind: mills and sails'

3.4 Sails and waterways carried the bulk of preindustrial trade

The most powerful machines of the preindustrial world were not on land. A large sailing ship captured, through hundreds or thousands of square metres of canvas, far more power than any windmill or waterwheel. The fastest 19th-century clippers could exceed 15 knots.

Ships evolved over millennia. Oared galleys in the Mediterranean concentrated human muscle: dozens to a couple of hundred rowers, each delivering under 100 W, could move a warship quickly for short bursts but needed huge supplies of food and water. Sails freed crews from rowing. Better hulls, sternpost rudders, combinations of square and triangular sails, and the compass allowed long ocean voyages. After 1500, sailing ships carried the first truly global trade in spices, silver, textiles, sugar and, tragically, enslaved people.

On land, transport was slow and expensive. Pack animals and carts moved at walking pace, and the animals and drivers had to be fed on the way. Carrying grain more than a few hundred kilometres overland could cost more than the grain was worth. Rome built about 80,000 km of paved roads, but they mainly served armies, officials and messengers; bulk food for the city came by sea from Egypt and North Africa.

Water was always cheaper. Rivers, canals and coastal shipping moved bulk goods at a small fraction of the overland cost. That is why nearly all great preindustrial cities grew on navigable water, and why China built the Grand Canal to carry southern rice to northern capitals. The pattern persists: the Ship propulsion tile describes how ships still move most of the world's goods by tonne-kilometre at the lowest energy cost per tonne.

• Smil, Energy and Civilization: A History (2017) · via Smil Mastery Course, M4 'Moving and building before engines'
• Smil, Energy and Civilization: A History (2017) · via Smil Mastery Course, M4 'Wind: mills and sails'
• Smil, Energy in World History (1994) · via Smil Mastery Course, M4 'Moving and building before engines'
• Smil, Two Prime Movers of Globalization: The History and Impact of Diesel Engines and Gas Turbines (2010) · via Smil Mastery Course, M4 'Moving and building before engines'

See it in the table

Check your understanding

Which harness innovation let horses pull with their full strength?

Which traditional waterwheel design was the most efficient?

If the wind speed at a mill doubles, roughly how does the wind power passing through its sails change?