Solar Air-Conditioning Using Vapor Absorption Refrigeration Cycle

The absorption cycle is a process by which refrigeration effect is produced through the use of two fluids and some quantity of heat input, rather than electrical input as in the more familiar vapor compression cycle. Both vapor compression and absorption refrigeration cycles accomplish the removal of heat through the evaporation of a refrigerant at a low pressure and the rejection of heat through the condensation of the refrigerant at a higher pressure. The method of creating the pressure difference and circulating the refrigerant is the primary difference between the two cycles. The vapor compression cycle employs a mechanical compressor to create the pressure differences necessary to
circulate the refrigerant. In the absorption system, a secondary fluid or absorbent is used to circulate the rfrigerant. Because the temperature requirements for the
cyclfall into the low-to-moderate temperature range, and 
here is significant potential for electrical energy savings,
absorption would seem to be a good prospect for geother-
mal application.
Absorption machines are commercially available today
in two basic configurations. For applications above 32oF
(primarily air conditioning), the cycle uses lithium bromide
as the absorbent and water as the refrigerant. For applica-
tions below 32oF, an ammonia/water cycle is employed with
ammonia as the refrigerant and water as the absorbent.