Solar collectors

Solar thermal collectors unlike solar PV-panels do not produce electricity. They heat up water or antifreeze. Modern models are able to heat up water to boiling point even in at low temperatures.

The attempts to use solar energy for heating and hot water have been known since ancient times. The flat solar collector constructed in the late XVIII century by Swiss Horace-Bénédict de Saussure has remained until today. Even then, with its help you were able to prepare food.

Practically, device for storing solar energy can be made by everyone from available materials. For example, even a bucket of water left in the sun is also a solar collector. But to have a practical application and high efficiency are required much more ideal structures.

The modern solar collector is complex absorber of solar energy built-in pipelines for coolant into it. The absorber is placed in an airtight container and it is exposed to solar radiation from one side only. The back side is covered with mineral wool or other insulation. Presented in this way the solar collector is a high-tech miniature greenhouse.

The more solar energy is transmitted from the coolant to the collector, the greater its effectiveness. This requires the use of special materials. One of them is the copper — it has a very high thermal conductivity. To increase the absorption of solar energy it is using special optical coatings, which do not emit heat in the infrared spectrum. This multilayer selective coating has a unique sapphire color and it captures the solar radiation in a very wide range — much wider than it is visible for a human eye.

Nowadays the most common are two types of collectors — flat and tube (vacuum). The tube (vacuum) one has gathered all the advantages of flat collectors, because it is much more convenient for installation and operation, because in a failure of one of the tubes it is enough just to replace it with another one. As the vacuum is ideal heat insulator, pipe collector is virtually independent of environment and significantly more sensitive to minimal solar radiation. Thanks to this technology, the vacuum collectors have found wide application as part of the additional energy systems for year-round heating and heating up water.

For example, they are effective in cloudy weather and at low temperatures, engulfing not only the direct but also scattered (diffuse) and even reflected from the surface of earth radiation. In the production a special high-strength borosilicate glass is used, which has a small expansion and does not break when temperature changes. The cylindrical shape of the pipes helps to the steady absorption of sunlight during the day — as a flat collector it would rotate watching the Sun, does not hold dirt, it is well washed by the rain and it is more resistant to the hits from a large hall.