Demonstration study on ground source heat pump heating system with solar thermal energy storage for greenhouse heating

In this study, a demonstration project of a ground source heat pump (GSHP) heating system with seasonal solar thermal energy storage (SSTES) and diurnal solar thermal energy storage (DSTES) is constructed for greenhouse heating. In the non-heating season, the SSTES overcomes the thermal imbalance of GSHP heating for agricultural greenhouses. While in the heating season, the DSTES undertakes part of the heating load of greenhouses, reduces GSHP heating electric energy consumption and improves the annual coefficient of performance of heating system COPsys,y. The experimental data illustrate that the soil temperature of ground heat exchanger (GHE) area is about 0.3 K higher than the initial soil temperature at the end of SSTES, and the COPsys,y of the proposed heating system is 14.3 % higher than that of bank control experiment. The above results demonstrate that the proposed heating system is favorable for greenhouses in cold regions. Further, coupling DSTES can reduce the rated capacity of GSHP and the total length of GHE tube for the newly designed heating system. In addition, the recommended values of two key operating parameters are given based on the experimental data. This study can shed a light on clean and efficient heating for greenhouses in cold regions and provide data support for related research.