Abstract: Disclosed are suitably structured storage tanks which substantially eliminate blending problems in thermal storage systems. More particularly is disclosed floatable baffle and flexible diaphragm means for preventing blending of different temperatures of water in a storage tank. Also disclosed is a thermal storage system wherein the tanks are at the base of a building and which includes the use of energy conserving turbines to further enhance the benefits of thermal storage. Direct pumping entry of the storage water at a low pressure is permitted into the load circuit which is at a substantially higher pressure and the turbine conserves energy required in the pumping.