Thermal energy storage using saturated salt solutions

Abstract

In order to reduce the volume required to store low grade thermal energy in water, various systems using phase change materials (PCMs) have been proposed. However, in order to overcome the poor heat transfer characteristics associated with the solidification of the PCM on heat transfer surfaces, large surface areas need to be provided. This is often achieved by encapsulation in either large or small containers, which has the effect of increasing the cost and reducing the effective energy density. Furthermore PCMs can only accept and release heat at one particular temperature. In an attempt to overcome these limitations thermal energy storage using saturated salt solutions has been examined. The energy density for a number of promising salts has been calculated and confirmed by experiment. Energy density increases of up to 4 times that of water are possible, depending on the salt used and the temperature swing permitted. The deposition of crystals from the solution on heat exchanger surfaces has been overcome by the use of a novel self-cleaning technique.