1.7.3 Solar Cooling
Use solar heat as an energy source to power a cooling appliance.
Heat from solar hot water or photovoltaic systems is used to power the cooling system.
There are several types of solar cooling technologies:
• Absorption cooling uses heat, instead of electricity, to drive the cooling system. Solar thermal energy vaporizes the refrigerant. This is accomplished either by a single-stage system which is driven by any warm fluid (not necessarily water) heated to between 180 and 250 degrees Fahrenheit, or a two-stage system, which works around 140 degrees Fahrenheit. The two stage system uses low temperature solar energy to “pre-heat” the air and a high-temperature energy source (e.g. natural gas or oil) is used in the second cooling stage.
• Desiccant coolers remove moisture from the air. Although this does not actually cool the air, the result is a lower relative
humidity in which people often feel more comfortable. The air that is dried by desiccants is often combined with
• 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 removes heat out of the air and the cooled air is blown in by a fan.
• Solar photovoltaic systems can be used to power heat pumps and air conditioners.
Solar cooling saves electricity and has no storage needs (like that of solar heating) since the need for cool air for machines rises and falls in-sync with available solar energy. However, the current high investment costs present a significant barrier to broad implementation. Compared to conventional cooling systems, the upfront costs are around 2 to 2.5 times higher.
In many countries, air conditioning is one of the highest energy consuming services in buildings. Solar cooling helps to reduce the amount of electricity supplied energy, thus reducing energy bills, and also reduces the pressure on electricity grids.
Depending on the project’s location and climate, determine which solar cooling technology is appropriate. In general, hot-arid and hot-humid climates are ideal for solar cooling.
1.4.8 Solar Hot Water Collectors
1.7.9 Active Solar Heating