Space Cooling with Solar Thermal Chillers

On a residential scale, solar thermal energy is best known and widely used for heating domestic water supply. Yet solar thermal technology has a much more unorthodox, seemingly paradoxical use: space cooling. Heat harnessed from solar thermal collectors can be used to drive a thermal chiller (absorption chiller) and cool a home or office building.

The process begins with the solar collectors. For thermal chillers, the collectors must be able to reach temperatures a bit higher than the average, inexpensive flat plate collector. However, evacuated tube collectors and beefed-up flat-plate collectors (double or triple glazing and increased backside insulation) can be used effectively. These collectors absorb solar radiation to heat water running through them. That water is then sent to the thermal chiller.

Inside the thermal cooling system, the hot water is used to separate a refrigerant from an absorbent fluid. That's usually lithium bromide, a nontoxic, eco-friendly solution. The refrigerant, typically water vapor, is then condensed in a chiller to produce cold water. The now-cool water is pumped into a heat exchanger (e.g. copper tubing), over which ambient air is blown and efficiently cooled.

This applies to a single-cycle thermal chiller. The chillers may also be double or triple cycle, meaning that the heat is reused two or three times. The more times the heat is recycled, the more efficient the system. The extra hot water from the solar thermal chiller can also be used to heat the home's water supply.

Solar Absorption Cooling / Active Thermal Cooling / Thermal Chiller