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2. WIND ENERGY HISTORY
2. WIND ENERGY HISTORY
the energy from the wind
the energy from the wind
Only 2% of the solar energy that reaches Earth is converted to wind energy and for various reasons, only a small part of this energy is usable.
Despite this, the energy potential of this energy source has been calculated to be around 20 times the current world energy consumption, which makes wind energy one of the first-magnitude renewable energy sources.
Wind energy is kinetic (due to its movement); This means that the power obtainable from it depends strongly on its speed, as well as on the surface area of ​​the collector. Thus, all the machines man has built to obtain the best possible performance from the energy of the wind are based on restraining the wind by means of some device placed in its path, as is evident when making a brief historical review of the use of the wind power.
Wind energy found its massive application most evident with the use of sailing on marine vessels, as early as the ancient Egyptians in the fifth millennium B.C. and still in use today.
The first wind machine known to history appears in the year 1700 B.C. in Babylon, being used to pump water, although it seems that in ancient Persia (7th century BC) vertical axis mills were already used to grind grain and pump irrigation water. However they had a problem, and that is that by using masonry walls to increase the torque on the blades that advance to leeward, the ability to orient themselves according to the direction of the wind was nullified. The control of the power was carried out by means of gates or shutters in the shovels or the masonry.
Previous to these, and possibly as precursors, the Chinese already used a water pumping system called "panemone".
Until the 10th century, it is not possible to find documents that mention windmills as a general practice, but from the 11th century, windmills with sail rotors appear in the Mediterranean area, which derive from the typical Manchego and Majorcan windmills, probably due to imported influences from Europe, whose characteristic was the four-bladed rotor made of wood, covered with fabric clothes.
The western mill, by contrast, is horizontal in axis and is believed to have been an evolution of the Persian mill, eventually brought to Europe by the Crusaders and entering the continent through Spain, Italy, and Greece.
Being horizontal axis, it requires an orientation system to face the rotor in the wind, which complicates its construction, although the power obtained is much bigger.
Although the evolution in the history of windmills proceeds continuously, in the late Middle Age, innovation and applications of wind machines occurred rapidly. Between the second half of the 18th century and the second half of the 19th, European windmills reached their highest level of improvement, within the limitations of artisan technology. The orientation and regulation systems are completed by internal mechanisms, turning windmills into mechanized factories with a high degree of automation, including even orientation systems. In these modern mills, only the upper part of the mill, which includes the rotor, rotates, the base being a brick, stone or wood tower, which gives them greater strength and durability.
The uses to which they are subjected are not only to grind cereal, but also to pump water, move sawmills, extract minerals... the power could be estimated at around 7,000 to 15,000 W and constituted the beginnings of the industrial revolution, concentrating artisans around concentrated production centers and favorable areas.
The development of the steam engine and thermal combustion engines almost completely displaced the wind machine in the industrial revolution of the 19th century, leaving its use limited to rural populations, especially the poorest and most remote, continuing to be used for the pumping water and grinding.
In the second half of the 19th century a new generation of wind machines appeared, with a different design concept: the "American multi-blade" opened the way to improvements in the performance of these machines, which did not really take place until the beginning of the 20th century, when aerodynamic theories for aeronautical uses were applied to the design of rotors.
The operation of this machine was very simple, with a multi-blade rotor coupled to a connecting rod-crank system that drives a piston pump. This has been the most widespread wind machine, having manufactured some 6 million units, of which more than 150,000 are in service today. In Spain they are found in a huge number on the island of Fuerteventura.
On this basis, different families of wind turbines were developed: wind pumps (5 to 15rpm) wind turbines with initial powers of about 5000W for battery charging and the most modern wind turbines to supply other generators such as diesel in remote sites or to start being part of from the electricity grid itself.
One of the founders of the American electrical industry was C. Brush, dynamo inventor, electric batteries, and the first commercial arc light bulb. Founder of the General Electric Company, in 1887 he built the first self-powered wind turbine, a giant 56 feet diameter rotor, 60 feet high and 144 wooden blades that powered 350 light bulbs and three electric motors, with a total power of 12,000 W. It worked for 20 years.
At the same time, in Europe, where the use of wind pumps had historically not been important, but the wind was known and considered as an important source of energy, wind turbines also began to be developed. Within a Danish government program, in 1892, Professor La Cour designed the first prototype of an electric wind turbine, and his steps were the first in the development of modern wind turbines, since, despite his training as a meteorologist, he pioneered aerodynamic experimentation, building his own wind tunnel for his experiments.
His wind turbine, despite the low performance of the classic rotor that he used, came to produce between 20 and 35 kW, being built on a 24 meter high metal truss tower and using a four-bladed model from which almost 200 units were installed until the 1st World War.
The aerodynamic theory developed during the first decades of the 20th century made it possible to understand the nature and behavior of the force acting on the blades and scientists who worked in the aeronautical field established the criteria that the new wind turbines had to meet. Likewise, as the turning speed increased, the number of blades no longer affected performance, so the use of two and three bladed wind turbines began.
In 1924, Savonius developed a very simple and cheap vertical axis turbine to build, which starts in very low winds but with little performance. In 1927 Darrieus developed another vertical axis turbine, which today is one of the options of interest within the field of wind turbines, since its performance and turning speeds are quite high.
Darrieus Turbine
Throughout the 20th century, applications based on the use of wind declined, as the use of oil became more popular. Even so, in countries such as the United States or Denmark, the study of this energy continued, and thus, in 1957, a student from the La Cour school installed a 24 meter diameter rotor wind turbine with 200kW power in Gedser, Denmark, that ran for 11 years continuously without maintenance.
The energy crisis of the 70's started a new period in the field of wind exploitation, preparing innumerable study programs that focused their interest on two main aspects:
Preparation of wind maps and location of sites.
Calculation, design and construction of high power plants.
As part of a new wind advance by the Danish government, the wind map of this country began in 1952. This allowed the cost of the installed kW to drop more than 50%, from that point on, government support for the installation of wind turbines began, and the strict safety regulations made wind turbines increasingly efficient, reliable and safe.
Subsequently, also in Denmark, the TVIND wind turbine started operating in 1977, with a nominal power of 2 MW and a rotor of 54 m in diameter, and was another historical and technological milestone, as it was convincing proof that wind energy It could be used on a large scale, thanks to new generators and used power electronics.
The Danish concept is a design principle of a technology that is described as follows: an horizontal axis turbine with three blades operating upwind (facing the wind), whose blades are rigidly fixed to the hub or rotor center. This concept, which had already been used in the Gedser turbine, is characterized by being a relatively simple, reliable and robust design. The first generation of commercially successful wind turbines was based on this principle.
Based on the Danish concept, the first standard turbines appeared in the early 1980's. One of the most famous turbines was that of the firm Vestas of 15 m in diameter and a nominal power of 55 kW (known as Vestas V15-55), which became the typical representative of this standard class in those years, which facilitated series production.
Although there have been ups and downs, in Europe it continued to develop in an unstoppable trend, especially in countries like Denmark, Germany or Spain, and more and more powerful and advanced wind turbines were being built each time. Right now, wind energy is implanted in the five continents and its development continues. The new giants, such as the Vestas V174 or the General Electric Haliade-X are the benchmarks of a new era, focused on off-shore energy.
Wind energy does not pollute, is endless and slows the depletion of fossil fuels, helping to prevent climate change. It is a fully mature and fine-tuned harvesting technology.
Due to this, governments have supported the implementation of this energy source, which is becoming more important every day. For example, in Spain wind power has been consolidated for years as the third technology in the Spanish electricity system, second only to combined cycle gas thermal power plants, and nuclear power plants. And the same trend we see in Denmark, Germany, USA or other countries.
Its development, together with other renewable energies such as solar, as well as the serious consequences of climate change, have condemned obsolete and polluting sources, such as fuel oil or coal, to disappearance, for the sake of a more clean future.
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