Proposal and assessment of a new solar space heating system by integrating an absorption-compression heat pump

In cold regions, solar space heating is a clean and promising method that can be used to reduce the consumption of fossil fuels and electricity; however, the heat supply cost is extremely high because of the high investment, low energy efficiency, and short operating time. In this paper, a new system is proposed to improve the thermodynamic and economic performance of solar space heating in this paper. An absorption-compression heat pump is integrated with a conventional solar heating system in which the temperature of the collected heat is decreased by 20 °C to 30 °C, to increase the solar collection efficiency. The low-temperature heat collected by the solar collector is upgraded through the absorption-compression heat pump to generate high-temperature heat for space heating in winter and low-pressure process steam for industrial applications in other seasons. The thermodynamic performance of the proposed system is investigated through a numerical simulation. The results show that the efficiency of the solar collector increased by 39.50%, its annual effective operating time reached 2682 h, which is approximately four times that of a conventional solar heating system, and the annual solar energy utilization ratio increased from 4.82% to 43.74%. The payback period of the proposed system decreases to 5.69 years when the natural gas price equals 7.25 cents/kWh, which is 9.35 years shorter than that of the reference system. Furthermore, parameter optimization is performed on the solar collector area, storage tank volume and heat pump capacity. A minimum payback period of 5.44 years is obtained when the solar collector area, storage tank volume and heat pump capacity equal 170 m2, 11.17 m3 and 18.35 kW, respectively. This work provides a new way to utilize solar energy more efficiently and economically.