Capacity matching and optimization of solar-ground source heat pump coupling systems

Ground source heat pump systems demonstrate significant potential for northern rural heating applications; however, the effectiveness of these systems is often limited by challenging geological conditions. For instance, in certain regions, the installation of buried pipes for heat exchangers may be complicated, and these pipes may not always serve as efficient low-temperature heat sources for the heat pumps of the system. To address this issue, the current study explored the use of solar-energy-collecting equipment to supplement buried pipes. In this design, both solar energy and geothermal energy provide low-temperature heat to the heat pump. First, a simulation model of a solar-ground source heat pump coupling system was established using TRNSYS. The accuracy of this model was validated through experiments and simulations on various system configurations, including varying numbers of buried pipes, different areas of solar collectors, and varying volumes of water tanks. The simulations examined the coupling characteristics of these components and their influence on system performance. The results revealed that the operating parameters of the system remained consistent across the following configurations: three buried pipes, burial depth of 20 m, collector area of 6 m2, and water tank volume of 0.5 m3; four buried pipes, burial depth of 20 m, collector area of 3 m2, and water tank volume of 0.5 m3; and five buried pipes with a burial depth of 20 m. Furthermore, the heat collection capacity of the solar collectors spanning an area of 3 m2 was found to be equivalent to that of one buried pipe. Moreover, the findings revealed that the solar-ground source heat pump coupling system demonstrated a lower annual cumulative energy consumption compared to the ground source heat pump system, presenting a reduction of 5.31% compared to the energy consumption of the latter.