History of energy in medieval times

Summary: Energy sources in the medieval world were highly localized, with great variability in the type and amount of fuel consumed.

In the medieval world, energy was generally consumed in the same community where it was found because transporting fuels was both difficult and expensive. Roads were not well maintained, and it was expensive to transport large quantities of wood in horse-drawn carts. Some wood, peat, or coal was shipped on rivers, but most major projects to improve European rivers or connect the inland areas with canals had not yet occurred. These transportation difficulties meant that fuel was restricted whatever material was locally available and varied significantly between communities. The restriction of fuel to mainly local sources also made it difficult to supply energy to cities of more than 100,000. Coal was not present everywhere, so the majority of the energy consumed consisted of plant matter, as both food and fuel. The local nature of energy sources also meant that the amount available was related to changing levels of local population.

Although exact figures are unavailable, it has been estimated that the total population of Europe roughly tripled between the years 1000 and 1300, before stabilizing in the early 14th century and then declining by more than one-third between 1350 and 1450 (in large part because of epidemics of bubonic plague). Similar trends occurred elsewhere, and as populations increased, more families competed for local energy supplies and woodlands were frequently cleared for the farmlands and the pasture needed to feed animals. The rise and then fall of the population meant that less food and other energy sources were available to most people in 1340 than had been available to their ancestors in 1100 or would be available to their descendants in 1450.

Sources of Energy

Any discussion of medieval energy must acknowledge the role of food and human muscular power. Food calories constituted a significant source of energy, because human muscle was needed power for many tasks that have since been mechanized, such as spinning wool, propelling boats, harvesting grain, and constructing buildings. Animal power was also an important energy source in most parts of Europe and Asia but was not widely exploited in Australia or the Americas. Oxen, horses, donkeys, yaks, water buffalo, and other animals were used to pull carts, plow fields, and turn some wheels used in the grinding of grain or fulling of wool.

Plows underwent a number of improvements in medieval Europe. New forms of harnesses were developed and some modifications were made in their shape, so that they could be pulled by horses as well as oxen. These innovations were major improvements, because horses are generally more efficient draft animals, even if they do not produce much milk and are less suitable to human diets. By the 11th century, iron-tipped plows had also been developed; these tools were not only larger but better able to break up the thick clay soils of northern Europe. Drawn by communal horse teams, these plows were able to bring the cultivation of grain to some new areas and contributed to increased agricultural production. New plowing technology represented a more efficient use of energy in agriculture that at the same time expanded the scale of agriculture.

Wind was another energy source exploited by medieval people. Windmills were developed during this period and sometimes used to grind grain, process wool, or occasionally pump water out of wetlands. However, wind did not make a substantial contribution to the energy use except in the propulsion of boats. Around 1000, boats were generally powered by oars, and the distance they could travel from shore was limited. With the exceptions of the Vikings in the far northern reaches of the Atlantic Ocean, people were not traveling far into the oceans at this time. In the second half of the 14th century, however, Mediterranean sailors were increasingly using sails to propel their boats and began to travel to islands in the Atlantic Ocean. This later led to the European colonization of Madeira, the Canary Islands, and Azores. Boat technology and knowledge of winds continued to improve, and by the end of the 15th century ships were regularly traveling between Europe and the Americas. Chinese ships were making similar advances and were crossing the Indian Ocean by sail in the early 15th century. This exploitation of wind energy allowed for a growing global trade in luxury goods and the transfer of species between continents. Water was also an important energy source in the medieval world, used to power mills and transport goods downstream.

Wood is the source that most often comes to mind when thinking about energy in the medieval world. Although it was not the predominant fuel everywhere, wood was burned in many places. The amount and type of wood available varied greatly. Generally, northern areas had more and denser tree cover. In the Mediterranean, wood sources could be more brushlike, and wood pastures in which individual trees would stand amid grasses were fairly common. In southern Europe, mountainous regions would often have thicker forests than the lowlands, resembling parts of Northern Europe. Britain is the exception: It had less wood cover, and even the hilly regions in the north tended to have few trees and waterlogged, grass-covered soils. Meanwhile, the Netherlands and some other regions along the North Sea consisting of low-lying swamps with relatively little tree cover, turned to other fuels. In areas with significant tree cover, dead branches and other parts of trees would be collected to be burned. Especially by the 14th century, these were most likely to be in places where the soil and climate were not that well suited to agriculture. Trees would also often grow in open pastures or be used as hedges to demarcate field boundaries, both of which also provided some fuel.

The aforementioned methods would provide sufficient fuelwood only in areas with either a small population or significant wood cover. In other areas, a system of more efficient woodland management known as coppicing developed. Most deciduous trees, especially oak, ash, and elm, do not die when cut and will continue to grow out of the same roots with numerous new shoots coming out of the old stump. The amount of wood that grows per year is highest in the early years after cutting, because of increased exposure to sunlight and multiple stems. These new shoots can then be cut after a period of time, most commonly between 12 and 14 years, and the process can continue indefinitely. Coppices required fences and banks to keep out the cattle, sheep, and deer that eat young shoots but produced large amounts of wood that was well suited for making charcoal or drying and burning as is. Another variation of coppicing was pollarding, whereby the initial cut was made at a height where animals could not graze it, usually a little higher than the height of a man. The shoots would then grow out of the pollard so that fuelwood could be sustainably produced from trees in fields that were otherwise used for pasture.

Coppicing is most associated with England, and the practice developed there because it has long been the least wooded country in Europe. Coppicing spread with population pressures and was used in the less wooded regions of eastern England by the 11th century. By the 14th century, it was the most common system of woodland management across England and was practiced in numerous parts of Germany, France, Belgium, and other places in Europe. The same population pressures led to woodland being cleared for agriculture, and in 1345 Europe had less tree cover than at any other point.

Wood could be burned in numerous forms. When it was collected as dead branches and stems, it would generally be broken up and placed in a fire. From coppices, the cut shoots were usually bound into bundles, called faggots in England, or treated similarly to collected deadwood. One other way in which wood could be consumed was as charcoal. Charcoal is the product of wood that has been burnt with insufficient oxygen. It is created by placing a substantial amount of wood in a pit, which is then covered with dirt to prevent it from burning completely. When it is set on fire, the result is that the water and other impurities burn off first, leaving chunks of nearly pure carbon that is fairly similar to mineral coal. The advantage of charcoal is that it can burn hotter than normal wood and has more energy in relation to its mass, so it is cheaper to transport. The disadvantages of charcoal are that some of the energy is lost from the wood in the process of turning it into charcoal, and it requires more labor to produce. As a result, it was used mainly in urban households or in industrial processes, such as smelting iron and melting glass, that required high heat. It was more common than wood as a fuel in cities because its lower mass made it easier to transport, but households in heavily wooded areas preferred wood to charcoal because it was easier to produce.

Many places did not have many trees, so various other forms of plant matter were burned for fuel. In Europe, peat was the most important of these. Peat forms in wetlands or waterlogged hills, where organic matter cannot completely decay. When cut and dried, it can be burned, although it is an efficient fuel. It was commonly used in Ireland, Finland, Russia, Scotland, the hilly regions of northern England, the Netherlands, other wetland areas around northern Europe. In areas where both peat and wood were available, people generally preferred to burn peat, as it required less labor to collect than wood. Turf, while sometimes used as a synonym for peat, was a fuel source consisting of the top layer of soil and the grasses growing upon it. It produces less energy than peat and was generally used in areas where the soils were partially peaty. Furze, or gorse, was another important fuel source in parts of medieval Europe. These are smaller, shrublike plants, which grow on open hills and expanses of pasture. These plants require much labor to collect, as the needles need to be burned off and the branches grow in irregular directions. It was, however, used for domestic purposes in places without access to other fuels or by poorer members of some communities.

Another type of fuel that was used by some people was cow, horse, or sheep dung. Dung could be collected from fields and roads, dried, and used for cooking in places with little access to other fuels. This practice is often associated with India and northern Africa, but dung was also burned by some people in England and Europe.

Coal is another fuel that was used locally by medieval peoples in places where it was easily accessible from the surface. Mines were shallower and the technology less advanced than it would become, but coal seams near the surface were mined for local consumption by at least the 12th century in parts of China and by the 13th century in parts of northern England. Prior to major canal and river improvements, coal was much more difficult to ship, and it was generally burned only in areas close to the coal pits. A major exception to this pattern is the sea-coal trade, which developed between Newcastle and London in the late 13th century. As London’s population grew to around 100,000 in the 13th century, it became increasingly difficult to supply it with charcoal or other wood fuels. The Thames River was navigable to London, while in northeastern England, there were numerous coal seams that came down to the Tyne River, near Newcastle. The coal was shipped down the east coast of England, and on arrival in London it was known as sea-coal for having arrived by boat. This sea-coal became the main fuel source for London in the last decades of the 13th century, but those early coal seams contained significant amounts of sulfur, which resulted in an unpleasant smelling smoke. This so annoyed Londoners that wood again became the main fuel in the city when its population declined after 1350. Coal was the only fuel source to be transported large distances in medieval times, but this transport was much more limited than it would later become.

Mills and Manufacturing

Aside from sailing ships and improved plows, the most important technological innovations for exploiting energy in this period involved mills. While these were sometimes wind-powered, the most common types of mills involved using the run of water (or run of the river) to turn wheels and power an industrial process. The most common type of mill, therefore, involved placing a building over a stream or diverting some of its water to run through the mill wheel. Tidal mills were less common but were a major innovation of this period. They function by creating ponds with a movable opening, so that water flowed into them at high tide, before a barrier was placed over the opening. In order to leave the pond, the water would then pass over a wheel in a process similar to that of mills placed over streams. Tidal mills were erected in flat areas along the coast that were not suited to other types of mills.

Mills were used mostly for grinding grain, but some were used in the production of wool textiles and in parts of the metalworking process. The total number of mills used to grind grain declined somewhat as population decreased in the late 14th and early 15th centuries, so that an increasing proportion were used for other purposes by 1500. Water mills and windmills were much better suited to grinding grain than human or animal muscle and allowed the exploitation of energy sources that would not otherwise have been used. However, the majority of the energy in almost all manufacturing processes continued to come from other sources. Different fuels were burned for processes that required heat, such as salt making, glassmaking, and smelting metals. Meanwhile, human muscular power was the main source of energy when movement was needed in manufacturing.

Cooking

During the Middle Ages, the largest use of energy was in cooking food and heating homes. The energy requirements for these varied with climate, as it takes slightly more energy to cook when it is colder and heating is not often necessary in warmer climates. In northern Europe, when there was sufficient fuel, cooking was commonly done by placing food in a large pot, called a cauldron, that stood over an open fire in the center of the home. In it would stew various mixtures of liquid, grains, vegetables, and sometimes a little meat, while the fire also served to heat the home. In periods when people had access to less fuel, the fires would be smaller and stoked less often during the winter months. Meanwhile, towns and some rural parts of southern Europe often had communal bread ovens or small commercial bakers and cookshops. By cooking for multiple people, such establishments reduced the fuel needed to prepare food but did not heat homes. This was not a problem in warmer climates but was problematic when they became more common in the cities of northern Europe. Communal ovens, cookshops, and bakers often came into being as an adaptation in places with less fuel and were more prevalent in the first half of the 14th century than at other times.

Sustainability

The question of whether medieval energy systems were sustainable is complicated. Plant fuels, animal power, and wind for sailing are all renewable sources of energy. Coppicing techniques produce more wood per year than unmanaged growth and can be continued indefinitely. Peat renews itself slowly, but many people believed that the draining involved in its extraction helped to improve the quality of land for pasture. Coal is a nonrenewable fossil fuel (actually the result of peat and other organic matter being compacted under great pressure over thousands of years), but the small amounts consumed compared to those of the industrial age suggest that it could have been mined at medieval levels for millennia. However, with the exception of coal and wind, all these energy sources require significant amounts of land or water and generally had limited use. Mills on rivers impede transportation and are not good for fish. Woodlands cannot be used to grow grain and can graze fewer animals per acre than open pasture. As a result of their reliance upon local lands to produce almost all of their needs, medieval societies did not have the ability to expand indefinitely. Historians debate whether the 14th century population of Europe was unsustainable given their technology or if it was just chance that a very deadly disease, bubonic plague, killed one-third of the population between 1347 and 1351. Either way, it is clear that the European population could not expand beyond the population of approximately 100 million in 1300 without major technological improvements. Energy was at the core of this need, as is evident in the increasing clearance of woodland, growing pressures on common resources, the growth of cookshops, and other effects of a growing population.

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