What does solar energy mean?

Solar energy is a natural, regenerating source of energy. It is coming from our sun. This kind of radiating energy gets free, when hydrogen atoms unite to helium. While one kg of helium is developed 180 KWh-s of energy gets free. From the sun to the atmosphere gets approximately 1,37KW/ square meters energy while to the ground it arrives only 0,34KW/square meters. To the ground it gets 12000 times as much energy as the worlds whole energy consumption is.

The solar energy was already used in ancient Greece mainly in architecture. The ancient Greeks used solar energy to heat their houses, because they had cut out all the trees in the Greek areas, and the import of the trees was very expensive. So they had to find out a new source of energy. They started solar architecture, which means that they built their houses, so that the houses could intercept the sunshine. The buildings were open on the south side. This way the sun could easily warm up the rooms in the building. The north side of the house was well built , it had large walls so the house was well protected against the north wind and cold. The ancient Greeks used solar energy this way.

In the Roman Empire the solar energy was used for the same purpose and a similar way, but they developed on the Greeks technique. So they built different houses for areas with a different climate. Besides they used glass for windows. So their houses were more protected against wind and cold. The glass also made the glass house effect, because sunshine got through the glass easily but the wind and cold couldn’t.

Usage of the solar energy in the middle age and in the Renaissance
In these times the solar architecture was forgotten and people tried to use solar energy for tactical purposes. So they wanted to set  enemies, ships , and houses on fire with the help of concave mirrors. Some famous natural-scientists also were interested in these plans. For example Leonardo Da Vinci ,and Roger Bacon. In the 1200s Bacon suggested the catholic church should set the Arabic army with concave mirrors on fire which attacks the crusade. From year 1600 bigger and bigger parabolic and ground mirrors were built. These mirrors were 2-3metres in diameter. These had disadvantages too. For example if they were made from one piece they were very heavy. For these problems Peter Hoesen who found the solution in the 1700s built his mirror from segments. He also put wheels on his mirror ,so it could be transported easily. To boot the angle could be changed too.

The spread of the glass houses: From the XVI. century spread fast in Europe. These were founded on the glass house effect. The sunshine gets easily trough the windows than it warms up the inner place, because the windows don’t let the sunshine out. The glass houses spread because of the big discoveries, because the plants brought from the new explored areas needed warm and suitable circumstances to be grown. There was often glass house built near flats, which had a window so the glass house could warm up the flat. However after the First World War the popularity of the glass houses started to get lower.

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