21 is in heat exchange with the low temperature refrigeration circuit 20 by means of coupling loop 19 providing heat exchange between high temperature condenser low temperature generator 17 and high temperature absorber 13 the high temperature circuit operates in the same fashion as a conventional single effect absorption chiller except that the condenser and the absorber of this high temperature circuit are operated at a much higher temperature than in a conventional single effect chiller the high temperature refrigeration circuit 21 is preferably operated within a temperature range of from about 0 u00b0 c to about 280 u00b0 c while the lower temperature refrigeration circuit 20 is operated within a temperature range of from about 0 u00b0 c to about 130 u00b0 c the high temperature refrigeration circuit 21 is operated in a manner such that both the high temperature circuit condenser 17 and the high temperature circuit absorber 13 are at a higher temperature than the generator of the low temperature circuit 20 as a result all of the heat rejected by both the high temperature circuit condenser 17 and the high temperature circuit absorber 13 is effectively utilized to heat the low temperature circuit generator thereby producing substantially more refrigerant vapor in the lower temperature circuit 20 than is generated in the high temperature circuit 21 with the input of external thermal energy at the same time the high temperature.