1We are surrounded by heat; humans generate heat through engines, air conditioners, and other modern conveniences. This heat can be beneficial as wherever there is waste heat, it can be used to heat water or accomplish solar cooling.
2Free heat from the sun or via waste heat can accomplish cooling more economically than using other fuels. Solar cooling, which is a very old technology, is actually how ice was manufactured in the late 18th century, prior to the modern day refrigeration process.
3Solar cooling or "absorption" cooling is accomplished by using two chemicals with a high affinity for each other. Heat is used to "distill-out" or break apart this bond; once the bond is broken, the heat is removed so they can re-join. When the high affinity chemicals recombine, pressure drops-as does the temperature.