Solar refrigerator

In order to understand the operation of the cycle and the ideas put foi"ward later it is useful to look at the essential properties of adsorbent-adsorbate pairs and the way that they are used in the solar refrigerator. 

Now it is possible to understand the simple solar refrigerator illustrated in Fig. 3 below ... 

This formulation applies both to the use of a semi-continuous cycle with an expansion valve and to a discontinuous cycle (such as that in the solar refrigerator) using a flooded evaporator in which the warm condensate must first cool itself before it can cool the load. 

The best sub-atmospheric refrigerant is water. Unfortunately it is not strongly adsorbed by carbons, but refrigerators and heat pumps based on water - zeolite pairs have been built and tested in research laboratories. Methanol is adsorbed well by carbons and a solar refrigerator based on a carbon - methanol pair was marketed by Brissoneau et Lotz Marine in France. Methanol is environmentally friendly, but deeomposes at temperatures around 150°C and so camiot be used for very high temperature cycles. 

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