As paradoxical as it may seem, cooling using solar energy is feasible using  solar thermal energy. Solar chillers use thermal energy provided by the sun or other backup sources to produce cold and/or dehumidification.

There are  two main solar cooling  processes :

• Closed cycles, where thermally driven sorption chillers produce chilled water for use in space conditioning equipment

• Open cycles, also referred to as desiccant evaporative cooling systems (DEC), which typically use water as the refrigerant and a desiccant as the sorbent for direct treatment of air in a ventilation system.

Solar cooling has a number of advantages over alternative solutions, e.g.:

• It can help reduce the electricity peak demand associated with conventional cooling, as maximum solar radiation usually occurs when cooling is needed. Solar thermal cooling can also operate in the evening by using thermal storage.

• When summer is over, solar cooling systems can be used for heating purposes such as domestic hot water preparation or space heating.

In recent years, the trend in architecture for greater glazed surfaces, combined with greater comfort expectations have meant a dramatical increase in energy consumption for air-conditioning. In some country, this has already led to an electrical grid overload and break down. This risk and the need to reduce green house gases for electricity production make the introduction of cooling with renewable energy sources indispensable.

At the end of last century it was still common view that solar cooling would only be profitable through photovoltaic driven compression cooling machines. However, optimized collectors, improved components and an enhanced system design have contributed to make solar thermal cooling a real technical alternative. It is now even able to compete financially with systems operating with conventional electricity sources.