Hybrid thermochemical sorption seasonal storage for ultra-low temperature solar energy utilization

Abstract The effective upgrading and utilization of low or ultra-low temperature heat (below 50 °C) could meet a significant fraction of space and water heating loads. To fulfill this goal, hybrid sorption thermal energy storage (TES) to recover ultra-low grade solar heat below 50 °C is investigated, aiming to address the issue of winter heating in severe cold regions. A water-based solar photovoltaic-thermal (PVT) system is integrated to provide heat and electricity for a sorption TES system. Composite ammonium chloride is used for thermodynamic prediction in terms of weather conditions in different places. It is demonstrated that when water temperatures increase from 31.4 °C to 51.2 °C, energy efficiencies of hybrid sorption TES system under theoretical and selected working conditions in Hangzhou increase from 0.52 to 0.57 and from 0.33 to 0.38, respectively. The overall exergy efficiencies of hybrid TES with the PVT system under theoretical and selected working conditions increase from 0.059 to 0.062 and from 0.046 to 0.057, respectively. The overall exergy efficiency of the hybrid system in Helsinki is 0.55, which is 4.3% higher than those in Hangzhou. One remarkable fact is that hybrid sorption TES integrated with the PVT system is quite promising especially for severe cold regions.