Heat Storage and Release Performance of Cascade Phase Change Units for Solar Heating in a Severe Cold Region of China

The heat storage and release performance of cascade phase change units are investigated numerically for users in Inner Mongolia’s severe cold region. Three schemes of phase change material combinations are thoroughly tested. We obtained a better material combination scheme S3 (palmitic acid + polyethylene glycol), which has higher heat storage capacity per unit mass, higher average heat flux, and better unit synchronisation performance, so that it is more suitable for solar heating and cascade heat storage units in cold regions of Inner Mongolia. This study takes into account the irradiation variation of typical days during the winter heating season. The results show that the palmitic acid and polyethylene glycol combination scheme has the highest total heat storage per unit mass. This scheme also performs well in the synchronisation of two-stage storage units. When compared to the other two schemes, the average heat flux is increased by 25.5% for the first stage unit and 16.8% for the second stage unit