How to build a Solar Icemaker

Everywhere in our world, refrigeration is a major energy user. In poor areas, “offgrid” refrigeration is a critically important need. Both of these considerations point the way toward refrigeration using renewable energy, as part of a sustainable way of life. Solar-powered refrigeration is a real and exciting possibility.

Working with the S.T.E.V.E.N. Foundation (Solar Technology and Energy for Vital Economic Needs), we developed a simple ice making system using ammonia as a refrigerant. A prototype of this system is currently operating at SIFAT (Servants in Faith and Technology), a leadership and technology training center in Lineville, Alabama. An icemaker like this could be used to refrigerate vaccines, meat, dairy products, or vegetables. We hope this refrigeration system will be a cost-effective way to address the worldwide need for refrigeration. This icemaker uses free solar energy, few moving parts, and no batteries!

Types of Refrigeration Refrigeration may seem complicated, but it can be reduced to a simple strategy: By some means, coax a refrigerant, a material that evaporates and boils at a low
temperature, into a pure liquid state. Then, let’s say you need some cold (thermodynamics would say you need to absorb some heat). Letting the refrigerant evaporate absorbs heat, just as your evaporating sweat absorbs body heat on a hot summer day. Since refrigerants boil at a low temperature, they continue to evaporate profusely — thus refrigerating — even when the milk or vaccines or whatever is already cool. That’s all there is to it. The rest is details.

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