PCM in a fridge / freezer combination: a challenging PCM application.

In Germany, there are 40 million household refrigerators consuming roughly 24 GWh per year. The project DiTES4Grid (Distributed intelligent Thermal Energy Storage for Grid) aims at integrating thermal energy storage based on a phase change material (PCM) in refrigerators for demand side management. A technical and economic feasibility study showed that in contrast to electrical energy storage a small cost benefit can be achieved if moderately variable electricity prices are assumed. Measurements on commercial PCM consisting of salt solutions showed satisfying properties regarding melting temperature and enthalpy of fusion, the use of these PCM turns out to be highly challenging in a thermal storage device. While corrosion was no problem, every PCM separated on cycling, so that different thickening agents were used resulting in considerable bubble formation. Therefore, various experimental setups were built to get better optical insights in the processes taking place on repeated freeze/thaw cycles.