Abstract: A thermal storage apparatus comprises a series of stacked heat exchange modules. Each module extends horizontally and comprises channels separated by corrugations. Each channel has underneath it a heat exchange fluid pipe through which a primary or secondary coolant circulates. An inlet pipe delivers the phase change medium, for example water, to the lower most module from which it circulates to the top of the apparatus. The modules are stacked by the wall of a module engaging a groove of the next module above it.

Abstract: This invention relates to an improved method of manufacturing a heat exchanger element. In a second aspect the invention concerns a heat exchanger element itself. In the third aspect the invention concerns a reservoir suitable for housing the heat exchanger element to form a heat exchanger. The element is manufactured by extruding polyethylene tubes and winding them into spiral coils. Each coil is located along the length of a rigid horizontal spacer bar in order to maintain even spacing of the coil. The element comprises a stack of coils which are not restrained against vertical movement. The element also comprises a cylindrical void through the center.