Abstract: A process for the energy-saving recovery of useful heat from the environment or from waste heat with the use of a reversible chemical reaction comprising, charging and discharging alternatingly and successively by pressure variation with hydrogen two vessels which are interconnected by lines and filled with a metal hydride and the hydride-forming metal and removing as useful heat the heat of compression and of hydride formation thereby liberated by heat exchange and replacing consumed heat of expansion and hydrogen evolution of the hydride by heat exchange with the environment or by waste heat.

Abstract: The heat collector system comprises a heat collector connected to a heat p. The heat collector has an inlet conduit and contains a heat transmitting fluid and is effective to take radiation heat from the environment. The heat collector has a structural configuration effective to additionally absorb convection heat as a convector which causes a good heat transmission between the ambient air and the heat transmitting fluid. A rated and controlled cooling device is connected to the heat conduit of the heat collector. The cooling device is effective to supply fluid to the heat collector at a temperature below the temperature of the ambient air. Further features of the invention include a regulating device effective to regulate the difference in temperature between the temperature of the ambient air and the cooling temperature.