It's a bit of a strange idea to think of using the sun to cool your home or business, but in fact, absorption cooling was the first type of air conditioning. Absorption cooling is still practical for remote homes in places where there is an excess of heat energy available. A home in the desert would be an ideal place to use absorption cooling via solar energy.
In absorption cooling, heat drives the system, instead of electricity. Two basic types of systems are:
- single-stage systems, which are driven by any warm fluid (not necessarily water) heated to between 180 and 250 degrees Fahrenheit.
- two-stage systems work at around 140 degrees Fahrenheit. These can use low temperature solar energy to "pre-heat" the air. A high-temperature energy source (e.g. natural gas or oil) is used in the second cooling stage.
Desiccant coolers are the other very popular style of solar cooling. Desiccant coolers remove moisture from air. This does not actually cool the air but reduces the humidity, making it seem cooler. These are often used in combination with other types of solar coolers such as vapor compression or evaporative, which really do lower temperature.
- vapor compression cooling uses solar thermal energy to operate a Rankin cycle heat engine.
- evaporative cooling uses a mechanical device that takes the heat from the outside air and uses this to evaporate water held in pads inside the cooling unit. This 'sucks' heat out of the air and the cooled air is blown into the home by a fan.
Solar Powered Air Conditioners
Using a photovoltaic panel to power your air conditioning is common sense incarnate: the more sun you have, the more air conditioning you have. This invention, patented in 2000, is especially ideal for RVs and campers, eliminating noisy, polluting generators.
The use of conventional air conditioning is really the opposite of most processes of solar cooling outlined above. Conventional air conditioning uses Freon and an air compressor, releasing excess heat back into the air. Solar cooling uses all heat available to cool the air in a process with results that are not as immediate, but far better for the environment.