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

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• Improving solar heating systems performance by integrating with a hybrid heat pump. • Solar heat upgrading through a hybrid heat pump for process steam generation. • Extending solar heating system operation time for process steam in non-heating season. • Transform system operation modes according to seasons for hot water and steam output. 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 m 2 , 11.17 m 3 and 18.35 kW, respectively. This work provides a new way to utilize solar energy more efficiently and economically.