Abstract: A process for preventing freezing of solar collectors by automatic drainage of the water or liquid working fluid contained within the collectors the working fluid is drained from the collector, but remains within the closed solar collector circuit. Apparatus responsive to the pressure exerted on the collector circuit fluid by an external source of pressurized fluid acts to drain and refill the collectors. The pressure is transmitted through a moving transmissio means, which may be a deformable or movable wall, and which prevents transfer of the collector circuit fluid into the external source of pressurized fluid. The apparatus provides two storage tanks, one of which is provided with an auxiliary heater, the thermal yield being substantially improved by arranging one of the two tanks inside the other.

Abstract: In a solar energy collector with on site storage, the storage unit is contuted of two insulating panels and, between them, a structure formed of two corrugated walls which are joined on one part of their surface, the whole assembly defining three separate volumes. One of the volumes is connected with the free space between the storage unit and a forward partition and constitutes with it the primary circuit. Another volume is connected with the user and constitutes with it the secondary circuit.