Abstract: A solar hot water heating system has a primary tank heated by solar energy utilizing a heat transfer medium circulated between a solar collector and a heat exchanger located in the primary tank. Usually a back-up tank is provided to supplement the solar system. The primary tank receives cold water from a pressurized source. Its hot water outlet is connected to a heating and storage back-up tank the outlet of which supplies hot water to a domestic water supply, or the like. A pressure-actuated valve responds to a condition of the medium. When a predetermined temperature is reached the valve opens to release water from the system thereby permitting surplus hot water from the primary tank to replace the released water and thus reduce back-up energy requirement.

Abstract: A phase-change heat transfer system which is self-controlled, self-pumping, and uses no moving parts. A heat collector device is connected in series with a condenser and an accumulator. The accumulator includes apparatus for regulating the pressure therein. A fluid capable of phase change within the system travels among the collector, condenser, and accumulator.

Abstract: Solar water heater using the phase-change principle including a collector, a condenser, and an accumulator joined to form a natural circulation system, including a pressure accumulator and a vapor-release drum.

Abstract: Thermal system which simultaneously collects heat from waste water and from the dehumidification of a living space and utilizes the heat thus collected to heat water; the transfer of heat is accomplished by a heat exchange medium circulating in a closed loop system.

Abstract: Solar water heater using the phase-change principle including a collector, a condenser, and .[.an accumulator.]. .Iadd.a vapor release drum .Iaddend.joined to form a natural circulation system .[., including a pressure accumulator and a vapor release drum.]..Iadd.. .Iaddend.