Phase change materials for solar thermal energy storage in residential buildings in cold climate

Heating accounts for a large proportion of energy consumption in residential buildings located in cold climate. Solar energy plays an important role in responding to the growing demand of energy as well as dealing with pressing climate change and air pollution issues. Solar energy is featured with low-density and intermittency, therefore an appropriate storage method is required. This paper reports a critical review of existing studies on thermal storage systems that employ various methods. Latent heat storage using phase change materials (PCMs) is one of the most effective methods to store thermal energy, and it can significantly reduce area for solar collector. During the application of PCM, the solid-liquid phase change can be used to store a large quantity of energy where the selection of the PCM is most critical. A numerical study is presented in this study to explore the effectiveness of NH4Al(SO4)2·12H2O as a new inorganic phase change material (PCM). Its characteristics and heat transfer patterns were studied by means of both experiment and simulation. The results show that heat absorption and storage are more efficient when temperature of heat source is 26.5 °C greater than the phase transition temperature. According to heat transfer characteristics at both radial and axial directions, it is suggested to set up some small exchangers so that solar energy can be stored unit by unit in practice. Such system is more effective in low density residential buildings.