A high efficiency absorption heat pump cycle is disclosed using a high pressure stage, a supercritical cooling stage, and a mechanical energy extraction stage to provide a non-toxic combined heat, cooling, and energy system. Using the preferred carbon dioxide gas with partially miscible absorber fluids, including the preferred ionic liquids as the working fluid in the system, the present invention desorbs the CO.sub.2 from an absorbent and cools the gas in the supercritical state to deliver heat. The cooled CO.sub.2 gas is then expanded, preferably through an expansion device transforming the expansion energy into mechanical energy thereby providing cooling, heating temperature lift and electrical energy, and is returned to an absorber for further cycling. Strategic use of heat exchangers, preferably microchannel heat exchangers comprised of nanoscale powders and thermal-hydraulic compressor/pump can further increase the efficiency and performance of the system.