A closed loop system for generating mechanical energy at high efficiencies. The system can have a heating source, a superheater, an expander, a receiver, an absorber, a desorber, and regenerator with pumps and controls. The superheater heats a working fluid (a refrigerant or steam). A positive liquid/vapor expander expands a low temperature refrigerant, or steam vapor to the saturated state (having both liquid and vapor parts) utilizing a low-pressure sub-atmospheric exhaust sink. An absorber, generates a low-pressure sub-atmospheric sink using chemosorption which involves the exothermic reaction/absorption of ammonia refrigerant in water. The desorber is used to reconstitute inlet vapor (for reuse) and the regenerator recovers heat generated by chemosorption. The system can meet electrical power needs for residences, businesses or office buildings. The system can supply electrical energy to power grids, and can be an alternative power generation plants.