Abstract: In a thermal power station installation the waste heat of the last stage is utilized by storing the cooling water which receives this waste heat, and heating it further during the periods during which the installation is not on full load, whereafter it is supplied to the grid of a remote area heating system.

Abstract: In a heat storage device for low-temperature applications, e.g. for heating greenhouses and warehouses, the drop in temperature in an intermediate heat carrier circuit, which had previously been necessary in such applications, is avoided and a said device of simpler construction than devices previously used for such applications is provided in the form of a plurality of heat storage members, each charged with a meltable heat storage mass and each having ribs, the members being stacked to define a battery thereof and being so arranged that they form between them ducts for the passage therethrough of a current of air, and ribs on said members defining ribs of a heat exchanger. The device may be used in combination with a heat pump. The invention also includes a method of space heating a building by solar energy, a method of cooling an enclosed space and a method of maintaining the ambient air temperature of an enclosed space constant, all by means of a said device.