Design and experimental investigation of a phase change energy storage air-type solar heat pump heating system

Abstract

To improve solar energy utilization and the stability of solar heating systems, an energy storage air-type solar collector was designed and developed. Phase change material was placed in the middle of the solar vacuum tube to reduce the impact of solar radiation fluctuations on indoor heating. Based on this, a new type of solar heat pump heating system was established, with three heating modes: solar heating, solar-assisted heat pump heating, and heat pump heating. The control system was designed to automatically switch the operational mode when environmental conditions change. The heating performance, exergy efficiency, and economic benefit of the system in engineering application were studied and analyzed for different weather conditions. The results of the investigation show that at an average solar radiation intensity of 613.4 W·m−2 and average ambient temperature of 12.5 °C, the system can provide continuous indoor heating for 9.5 h in the solar heating mode, with the solar collector operating at an average thermal efficiency of 44.8%. The energy stored in the phase change material energy storage core is still capable of running the heat pump efficiently for 3 h after solar heating ends. The exergy efficiency of the heat pump is significantly improved by an average value of 12.1%. Economic analysis shows that the system can adequately meet building heating demands, with an average coefficient of performance of 3.6. Compared with the electric boiler heating system, the proposed system can reduce annual operating costs by 72.8%, with a payback period of approximately five years in Northern China.