A Solar Ammonia Absorption Icemaker

Jaroslav Vanek, Mark “Moth” Green Steven Vanek
©1996 Jaroslav Vanek, Mark “Moth” Green, Steven Vanek

Above: Steven Vanek with his machine which uses solar thermal energy to make ice.

verywhere 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 usingrenewable 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 andtechnology 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 canbe 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 lowtemperature, 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. One of these details is how the liquid refrigerant is produced. Mechanically driven refrigerators, such as typical electric kitchen fridges, use a compressor to force the refrigerant freon into a liquid state. Heat-drivenrefrigerators, like propane-fueled units and our icemaker, boil the refrigerant out of an absorbent material and condense the gaseous refrigerant to a liquid. This is called generation, and it’s very similar to

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Home Power #53 • June / July 1996

Refrigeration

Layout of the Solar Thermal Icemaker

Condenser Coil: in water bath

Parabolic Trough Collectors: 7 X 20 feet totalcollecting area

Generator Pipe: filled with calcium-chloride-ammonia mixture Evaporator / Collecting Tank: in insulated ice-making Box
t– Wes East

the way grain alcohol is purified through distillation. After the generation process, the liquefied refrigerant evaporates as it is re-absorbed by an absorbent material. Absorbent materials are materials which have a strong chemical attraction forthe refrigerant.

This process can be clarified using an analogy: it is like The plumbing of the icemaker can be divided into three squeezing out a sponge (the absorbent material) parts: a generator for heating the salt-ammonia mixture, soaked with the refrigerant. Instead of actually a condenser coil, and an evaporator, where distilled squeezing the sponge, heat is used. Then, when the ammoniacollects during generation. Ammonia flows sponge cools and becomes “thirsty” again, it reabsorbs back and forth between the generator and evaporator. the refrigerant in gas form. As it is absorbed, the refrigerant evaporates and absorbs heat: refrigeration! Plumbing Detail All plumbing is ungalvanized steel (black iron) unless indicated In an ammonia absorption refrigerator, ammonia is therefrigerant. Continuously cycling ammonia refrigerators, such as commercial propane-fueled systems, generally use water as the absorbent, and provide continuous cooling action. The S.T.E.V.E.N. Solar Icemaker We call our current design an icemaker. It’s not a true refrigerator because the refrigeration happens in intermittent cycles, which fit the cycle of available solar energy from day to night....