Solar Ejector Cooling

Solar ejector cooling uses the ejector principle which has been known for around a hundred years. Also known as jet pumps, early ejectors were used to evacuate the condensers in steam power plants.

Drawing by Paul Michael

Ejector cooling works like an airbrush, where compressed air expands out of a jet, sucking paint and air into the airbrush body and then expelling it on to the surface you want painted. With ejector cooling the “paint” is replaced with a refrigerant.

When the refrigerant evaporates as it gets sucked up the line, it draws in a lot of heat, which is the cooling effect. When it comes out of the jet it needs to be recirculated and re-compressed to work again.


To get the refrigerant to move it is heated by solar collectors so that the fluid enters the ejector at supersonic speed. In doing so, its temperature and pressure drop greatly, creating a low pressure region in the evaporator.

Solar Ejector Cooling Circuit

Ejector Cooling Circuit

Refrigerant flowing in a second circuit evaporates in the evaporator, and provides the cooling effect.

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