ارزیابی عملکرد و بهینه سازی سیستم پمپ حرارتی با منبع زمین گرمایی

This paper presents a novel solar-ground source heat pump system (SGSHPS) designed for an office building in Beijing for heating, cooling, and producing domestic hot water. An operation strategy of the system in transition seasons is proposed to keep the heat pump off and connect ground heat exchanger (GHE) directly to the heat exchangers of fan coils, as indoor conditioning terminal equipment. With the simulation tool TRNSYS, the important parameters of the system were optimized and the operation strategy was shown to be feasible. Two mainstream operation plural strategies in winter were analyzed and compared, and the system with GHE and solar collectors installed in series (SGSHPS(s)) showed better performance than SGSHPS(r) in cold regions.

The use of renewable energy is an important substitution of fossil-non-renewable energy sources. The energy efficiency contributes to energy conservation in buildings. The ground source heat pump (GSHP) uses the underground shallow soil as cool and heat source, which is different from the traditional air-source heat pump. Because the temperature of underground soil stays relatively stable, even in the winter of cold regions soil can maintain higher temperature than the atmospheric environment. So the ground source heat pump has higher energy efficiency than an air source heat pump. But because of the imbalance between annual heating and cooling loads of buildings, after long-term operation, ground source heat pump system will inevitably cause variations of soil temperature, and this will influence energy efficiency and stability of the system. Furthermore, in the winter in cold regions, long-term operation will cause the heat pump to work at a too low evaporation temperature, even to shut down. On the other hand, because solar energy is a kind of inexhaustible, safe, clean, and non-polluting renewable energy, the use of solar energy is an important way to ease the energy and environmental crisis. However, because terrestrial locally available solar energy is influenced by seasons and weather, there are limitations in various types of solar energy heat utilization technologies.

In this paper, the authors designed SGSHPS for an office building in Beijing according to the load demand. A novel operation strategy of the system in transition seasons was proposed. Two mainstream operation strategies in winter were analyzed and compared. The important parameters of the system were optimized. (1) According to the simulation result of systems operating in heating mode for 3 months in winter heating season, operation performance of SGSHPS(s) was better than SGSHPS(r) in Beijing. After 10 years the soil temperature decreased by 0.8 °C; in the case of SGSHPS (r), the result was 1.6 °C; in case of GSHPS, the result was 3.1 °C. The capacity of SGSHPS(s) to maintain and restore soil temperature was better than that of SGSHPS(r) in climatic conditions of a cold region such as Beijing.