A system for transferring thermal energy from a solar energy collector to a storage tank by pumping water from the tank through the heat exchanger and back into the tank. Two temperature-sensitive thermistors sense respectively the temperature of the water as leaving the heat exchanger or as being held therein, and the temperature of the water in the tank or as leaving the tank; these thermistors are included in bridge circuits which provide control signals representing the collector and tank temperatures and the differences of these temperatures for controlling water circulation, collector heating and/or dumping of the water, for collecting thermal energy and for preventing the circulation from freezing or boiling.

A unique and extremely practical solar heater has been described which is particularly suited to the heating of swimming pools. The novelty of the system lies in the use of an extremely light-weight flexible unit of essentially all plastics construction which floats upon the surface of the pool and is easily removed therefrom, and which functions dually as a flat plate collector by virtue of water circulating through it during sunlight hours, and as an efficient insulator and vapor barrier for the pool surface. A number of such units are generally employed to cover most of the surface of a swimming pool, and are covered by a relatively thin plastic over-cover, preferably transparent and tinted an attractive color.

In a solar radiation collector composed of a mat formed of a black foil member and a radiation pervious foil member, the two members being joined together along the outer edges of the mat and at interior locations of the mat to form an extended flow path and an inlet and outlet for a fluid heat carrier medium, the collector further including a cover connected to the mat along opposed edges thereof and arranged to be disposed in the path of solar radiation toward the mat with an air space being defined between the mat and the cover, with the cover being formed to define a flexible support for holding at least one radiation pervious pane and at least one reflecting panel in relative positions such that the pane, the panel and the mat constitute the legs of a triangle enclosing the air space.

A flat plate hydronic solar collector combining features of both the trickle and pressurized type of collector and also of metal and plastic collectors, the invention consisting of a plastic film tube divided into pockets into which heat transfer liquid flows by gravity, moving through a multiple number of pockets as the liquid progresses through the tube, removing heat from the side of the tube facing the sun, the pressure in each pocket being limited by the depth of the pocket. An important embodiment of the invention has a metal solar energy absorber plate secured over the film tube and its mounting surface so that the swelling of the film tube causes it to make extensive contact with the metal absorber.

A solar energy collector housing having a transparent cover, and a solar energy absorbing panel in the housing beneath the cover, and including a transparent member having closed tubular air pockets positioned between the panel and the cover to inhibit convection currents therebetween.