Abstract: A system for extracting heat from low temperature water includes a source of water at a temperature between approximately 0.degree. C. and 10.degree. C. and a heat pump removing heat from the water and transporting it for transfer to an external heating circuit. The heat pump has a closed circuit containing a heat transport fluid, a condenser, and an evaporator. The water, acting as a heat source, is fed into a vacuum vessel and subjected to triple-point conditions thereby concomitantly forming water vapor and a water/ice crystal suspension. The evaporator is disposed in the vacuum vessel out of direct contact with the water/ice crystal suspension for absorbing heat from the evaporated water vapor.

Abstract: System for waste heat recovery, comprising a combustion machine (2,3) with a compressor (4) for the combustion air (30) and means (7) like a heat exchanger (13) and/or a recirculation duct (14), to transfer heat, contained in the combustion gases (37,38,39) after their expansion in the machine (3), to the combustion air flow (33) before its entry into the compressor (4). Water (8,8') is introduced into the (to be) heated combustion air flow (30,33) cooling it by its evaporation, and the vapor is partially condensed again in a cooler (6) fitted in the compressed flow (34) after leaving the compressor (4). The condensation can take place at higher temperature, thus the system acts as heat pump for the waste heat. The compressed air flow (35) enters extra cooled into the combustion chamber (2) which provides an additional advantage. For the compressor (4), combustion chamber (2) and turbine (3) a normal gas turbine may be used.