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Air Conditioning

Conventional air-conditioners and refrigerators work with electrically powered compressors, which, when having a higher energy need, will also give off more heat to the incoming air. The basic concept of solar cooling is to use the “excess” solar energy to cool buildings or machines when it happens to be most hot during the day. Solar cooling saves electricity and has, as opposed to solar heating, absolutely no storage needs: The need for cool air for machines rises and falls almost exactly in-sync with available solar energy.

Depending on the use, different techniques are used for solar cooling. Refrigerators can be operated by the principle of the heat pump or by thermoelectric systems. Buildings and rooms are cooled by allowing warm air to dehumidify while being absorbed into a suitable material (evaporative cooling). In order that the material can once again absorb moisture, it is dried by heat delivered by a solar collector. So the same collector can be used for cooling in the summer and for heating during winter.

While solar heat gain remains the most talked-about topic, the possibilities of solar cooling are underrated in the general discussion and are rarely found in popular literature in Germany. At least solar air-conditioning has a promising future in tropical and subtropical regions.

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