New method to evaluate the heat storage density in latent heat storage for arbitrary temperature ranges

Phase change materials (PCM) are used to store heat or cold in narrow temperature intervals with high storage density. In applications with an exact temperature range, the heat storage density can be calculated straight forward and different PCM can be compared. However, in many applications no exact temperature range is known or the temperature range is not fixed. In such cases, the evaluation of the storage density and the comparison of different PCM are quite difficult and the standard approaches do not give accurate and easy to read results. In this paper we present a new method that is simple, accurate, and allows a visual evaluation of the heat storage density for arbitrary temperature ranges. This is possible by plotting the enthalpy difference in a 2-dimensional contour plot with the upper and lower storage temperatures as the two dimensions. In a second step, the temperature differences used for heat transfer, for example at a heat exchanger, can be included. This way, the new method can be used as an aid in the design of a storage and for its technical and economical optimization.