Performance analysis of solar-air source heat pump heating system coupled with sand-based thermal storage floor in rural inner Mongolia, China

The solar-air source heat pump (SASHP) heating system has gained significant attention in rural clean heating renovations. Nonetheless, the lack of low-cost thermal storage terminals in rural areas results in low energy utilization and high electricity consumption. This study proposes a SASHP system coupled with sand-based thermal storage floor and experimentally evaluates its thermal performance in a rural residence in Inner Mongolia, China. The system performance during the entire heating season was discussed under different operating periods of air source heat pump using TRNSYS models. Results demonstrated the SASHP heating system coupled with sand-based thermal storage floor maintained an average indoor temperature of 18.8 °C, even when the outdoor temperatures ranged from −18.4 °C to 12.3 °C. The average coefficient of performance (COP) and solar fraction of the system are 2.6 and 50.9 %, respectively. Operating the air source heat pump in the daytime (Mode 4) reduced the energy consumption and carbon dioxide emission by 28 % compared to the nighttime operation (Mode 3), with improved the COP and solar fraction. However, operating costs vary significantly with local electricity pricing policies. Without peak-valley pricing, the operating costs in Mode 4 are 28 % lower than that in Mode 3, while the operating costs in Mode 4 are only 2.6 % higher than in Mode 3 with peak-valley pricing. These findings provide a valuable reference for the design and operation optimization of SASHP system, which aims to promote the popularization and application of this system in the field of severe cold rural heating.