Abstract: A thermal energy storage and transfer system comprises a water-filled network that includes an interconnected storage vessel, heat absorber and radiator means. In accordance with the invention, a hermetically sealed container that has been charged with a thermal energy storage salt is stationarily submerged in the water storage vessel. An adjustable louver device is disposed between the heat absorber and incident solar radiations, and the louvers or vanes are selectively and automatically opened and closed in response to the thermal levels in the water storage tank and in response to the presence or absence of sunlight.