Solar energy

Already in old times people began to think over the abilities of solar energy application. As legend has it, the great Greece scientist Archimedes burnt enemy fleet which laid siege to his native town Syracuse with the help of kindling mirrors chain. It is known for certain that about 3000 years ago Sultans palace in Turkey was being heated by water warmed up by solar energy. Ancient inhabitants of Africa, Asia and Mediterranean world got salt by boiling off sea water. However people’s interest was particularly drawn to the experiments with mirrors and multiplying glasses.

A real “solar bum” began in the XVIII century when science free from manacles of religious superstitions started advancing in quantum leaps.

The first solar heaters appeared in France. G. Buffon - a scientist created a large concave mirror which focused reflected sun lights in one point. This mirror was able to inflame a dry wood 68 meters far from if day was sunny. Soon after that Sweden scientist N. Sossure constructed the first heating boiler. That was just a wooden box with a glass cover but water filled in a simple device was warmed by the sun up to 88°С. In 1774 year the great French scientist A. Lavoisie first applied glasses for solar heat energy concentration. Soon in England apperared a big double convex glass melting cast iron for 3 seconds and double crouan (granite) for 1 minute.

First solar batteries transforming solar energy into mechanical one were constructed also in France.

O. Musho - an inventor demonstrated an insolator - a device which by the help of a mirror focused rays on a boiler in the end of XIX century at the Word Exhibition held in Paris. The boiler activated a printing machine which could produce 500 copies of newspaper per hour. In a few years a similar device with 15 horsepower was constructed in the USA. Years passed, insolators were improved but the main operator principle was the same: sun-water=steam. And in 1953 year scientists from National Aerospace Agency of the USA created an original solar battery – a device directly transforming solar energy into electricity. As early as 19 century, the 70s, so called photo-electric effect – an effect of release of electrons of a solar body or liquid under electromagnetic emission influence was invented.

In 30-s years the head of Russian physicians A.F. Yoffe suggested to use semiconductor photo cells in solar energy. It is true that the record degree of efficiency of those days’ materials didn’t exceed 1%, so only one hundredth part of solar energy was transformed into electricity. As a result of longstanding experiments solar cells with degree of efficiency up to 10-15% were developed. In 1959 year they were installed on one of the first artificial Earth satellites and science then all spacecrafts were equipped by panels with solar batteries many meters height. Low degree of efficiency could be compensated by bigger area for example by covering the whole Sahara Desert by photo cells – and all-powerful solar electric generating station is constructed. However silicone semiconductors on the base of which solar batteries are produced are very expensive. The higher is the degree of efficiency the more expensive are the materials. Consequently the part of solar energy in today’s energy is not big. However according to limited fossil fuels the part of the energy produced by solar batteries will be inevitably growing. Developments aimed at the degree of efficiency growing and at cost reducing conduces the growth of solar batteries application. One of the main advantages of solar energy is the ecological cleanness. It is true that silicon connections can damage environment slightly, but in comparison with burning fossil fuels consequences this damage is really a drop in a bucket. Durability is a very important advantage of semiconductor solar batteries. And besides that the staff doesn’t need any special knowledge for the handling. As a result, solar batteries become more and more popular in industry and in everyday life.

A few square meters of solar batteries can easily solve all energy problems of a small village. In countries where there are lots of sunny days – the South of the USA, Spain, India, Saudi Arabia and etc. – solar electric generating stations have already been working for a long time. Some of them are highly powerful. Today building projects of solar electric generating stations above the air (where solar rays don’t lose their energy) are being developed. The emission detected on the earth orbit is expected to be transformed in another type of energy – microwaves and sent to the Earth. This sounds fantastically but high technology can provide to implement the project in the nearest future. The majority of solar heating system consists of solar collectors constructed in various ways where liquids – water or oil are applied for receiving (income) and transmission. Usually these systems consist of a tubular radiator filled with water. The radiator is made of dark color material and is located under dark plate. The whole system is covered by glass. The solar radiance penetrating through the glass, heats the liquid which goes forward to a special heat-insulating container.

From the other side cool water is pumped down in a radiator in order to be heated and repeat the same way. Certainly this system will not provide high temperatures but even if a part of free energy is detected it is also an economy. Vacuum manifold is much more effective – it can heat the liquid up to 300°С due to working in vacuum, in other words in an air-free space. If there is no air, nothing steals heat from the radiator. There lots of various types of radiators working on the base of principle of solar rays focusing in a not large space. There the highest temperatures can be obtained. Systems of mirrors or multiplying glasses concentrate solar radiation on the tubular radiator common to us filled with liquid. The liquid is heated very quickly and enters the whole heating system of the accommodation. Central energy stations working on the base of solar energy usually have a few thousands mirror-reflectors to detect solar energy on a large space. All the reflectors focus the solar rays on the top of the central tower where cool water comes in through piping system continually. Under the influence of radiation water boils and transforms into steam which turns turbine fins very quickly.

This type of electrical generating stations works successfully in the USA, Japan and some other European countries. A large quantity of scientific experiments and high technologies sometimes demand to create great temperatures. The solar energy which is able to create gigantic temperatures on a small space is the best way. The most popular “solar stove” operates in French town Odilo. Its flexible mirrors concentrate solar energy from a large space at an area less than 1 square meter. This area is situated on a small town in front of system of the mirrors. On sunny days the temperature can be touched upon 3300°С. Due to this materials with special properties that cannot be produced in traditional metallurgy are developed.

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