Investigation of heat of fusion storage for solar low energy buildings

This paper describes a theoretical investigation by means of TRNSYS simulations of a partly heat loss free phase change material (PCM) storage solution for solar heating systems. The partly heat loss free storage is obtained by controlled used of super cooling in a mixture of sodium acetate and xanthane rubber. The storage can cool down to surrounding temperature preserving the latent heat in form of the heat of fusion energy. The basis for the calculations is a super low energy house with a space heating demand of 2010 kWh/year and a domestic hot water demand of 2530 kWh/year. For storage volumes in the range of 500 – 3000 litres the heat loss free state is seldom reached and the effect of super cooling is limited. For larger volumes the heat loss free state may be reached. The benefit of using a PCM storage compared to a traditional water storage is limited with respect to energy savings for storage sizes up to 1 m3, but if the same amount of net utilised solar energy should be reached it would require a water storage that is 2 – 3 times larger.