In the middle ages, windmills became a very popular form of using the natural power of wind in order to drive a large diversity of machines. When they were developed in the 12. century, human muscle power was, for the first time, substituted by the power of the wind. That was a revolution, since people or animals driving the mills became exhausted after a while, and the wind power was so gigantic that it could even drive bigger and more powerful machinery. The picture shows the traditional type of a windmill from the Netherlands, as human kind was using it for centuries.

Image via Wikipedia

A fact widely unknown is that the first windmills actually were mounted on top of a single pivoting base, so that the entire building was moving around in order to ensure that the windmill blades were properly aligned with the wind. Windmills, where only the top section was used to turn the blades in the direction of the wind, were only invented in Europe in the 15. century. There were different types of windmills in use. The first models went back to the Persian idea (which probably built the oldest windmills at all, but no proof of how the complete design looked are left today) are of using a vertical shaft with blades or sails attached. Although this type of mill was easy to construct, it had one major disadvantage. With vertical windmills, a big part of it has to be shielded, so that the wind can catch properly (aerodynamic drag force). That means on the other hand, that a large part of the available power is actually lost.

Image via Wikipedia

The design of windmills using the horizontal axis was geared up to the water mill or water wheel design. The power of the rotating blades was transferred from the horizontal to the vertical axis by using cog wheels from wood or stone, and the power of vertical rotation was directly used to move grind stones, which were milling the grains. Apart from grain mills, the second most important application was water transport driven by wind energy. Today, you can still find some of these small-scale wind mills used for pumping water into garden and field irrigation systems on the island of Crete in the Mediterranean Sea.

Starting in 1390, the Dutch set out to enhance the windmill design by using a tower as the main building, to which a horizontal axis windmill with four blades was attached to the top section. They also incorporated floors in the building, so that different sections were created for grinding, for storing raw and ground grain, and in order to accommodate the people who worked there; in most cases this was the miller and his family.

Image via Wikipedia – image credit

These windmills were improved over a period of about 500 years. Aerodynamic lift was added and the shapes of the rotor blades were improved in order to get the most out of wind power and to ensure a stable running. Improvements to the leading edge and to the gravitational centre were also made and finally lead to ever increasing efficiency. 

These mills were the driving force of economic development before the industrial revolution. The range of applications became as versatile as it gets. In the saw mill, for instance the entire sawing process was driven by the mill. Other examples were complete processing lines for tobacco and spices.

There was only one important application missing until the 20th century. This was the century in which wind was put to the generation of electric power.

Image by SarahDeer via Flickr

With the declining reserves of fossil fuels worldwide came the challenge of finding alternative sources of energy and of putting them to use in economically reasonable ways. The conversion of solar energy was one of the easiest options, since solar cells were already widely developed in the eighties and nineties, and only had to be optimised and incorporated into bigger but manageable systems. With other forms of energy, like with wind energy, there were issues in terms of efficiency right from the beginning, and a single wind mill for energy generation put out there in the landscape would at most have caused a smile on most peoples faces.

 But the wind generator principle was known and an intensive process of optimisation and trials followed. The materials for the blades were refined and the size of components was reduced, until the wind mill as we know it today was finally ready for the market. The idea of wind farms hugely improved efficiency of wind generating systems, since costs were reduced. A multitude of wind mills lined up in certain patterns can optimise the impact of wind, and thus the energy produced from it, where strong and mostly steady wind is present, the building and development costs for the site per generator were minimised, and the cable routing became more a task that could be handled like any other cable routing project – systematically.

Wakamatsu wind farm in Kitakyushu, Japan – image credit

 Despite all euphoria, a few problems remain: In some areas people strongly oppose the erection of wind farms because they seem to dwarf famous buildings or ruin the views in otherwise beautiful landscapes. There is also the issue of noise generated from the blades turning in the wind, which is why they need to be placed in some distance to urban areas. Because of their height, they are also not suited near airports and low altitude flight paths. But all in all, wind farms become more and more wide spread and will help human society to progress in the process of substituting fossil with renewable energy sources.