Optimization of an integrated system including a photovoltaic/thermal system and a ground source heat pump system for building energy supply in cold areas

The photovoltaic (PV) collectors tend to overheat in summer, which reduces the efficiency of power generation. The unbalanced heating and cooling loads cause the ground source heat pump (GSHP) system to operate unstably in severe cold areas. To solve the above two problems simultaneously, an integrated system including a photovoltaic/thermal system and a ground source heat pump system (PVT-GSHP) was proposed, which had an extremely high energy utilization efficiency. However, the complex variation of cooling and heating loads was influenced by meteorological conditions over time. The demand of efficient operation and good economy of the system challenged the optimal configuration and control strategy among multiple energy sources, which was investigated in this study. A dynamic model of the PVT-GSHP system based on TRNSYS was developed and the corresponding control strategy was formulated. The genetic algorithm was used to optimize the matching of buried pipe lengths and PVT collector areas. The effects of different matching on the system parts and the whole performance were analyzed. The results show that increasing the PVT collector area can increase the ground temperature and shorten the buried pipe length, but it is not good for summer cooling, thus there is an optimal match. Compared with two independent systems of the traditional GSHP system and PV generation system, the PVT-GSHP system has excellent advantages and application prospects because it has 48.3% reduction in the total buried pipe length, 68.89% reduction in the footprint area of ground heat exchangers, 10% increase in the heating coefficient of performance (COP) and 72.3% reduction in life circle cost. This study provides theoretical support for the optimal design of the PVT-GSHP systems and similar complementary multi-energy systems.