Thermal Performance of Greenhouse Heating with Loop Heat Pipe Solar Collector and Ground Source Heat Pump

The hybrid heating system consisting of loop heat pipe solar collector (LHPSC) and ground source heat pump (GSHP) was proposed to maintain greenhouse temperature in Harbin (the coldest provincial capital of China) in this paper. The thermal model was developed to predict transient greenhouse and water storage tank temperatures corresponding to the supplied energy of GSHP. The thermal performance including transient heat loss and thermal efficiency as affected by ambient temperature were analyzed. The results show that the greenhouse and water storage tank temperatures fluctuated in the range of 17-24 oC and 51.2-52.3 oC in terms of intermittently supplied energy (200 kW) of GSHP, when ambient temperature changed from -24 oC to -13 oC, respectively. Heat losses of maintenance structure, ground, ventilation and water storage tank varied in the range of 51.9-73.2 kW, 2.45-3.45 kW, 11.1-15.5 kW and 5.87-6.91 kW, respectively. The maximum and mean thermal efficiency of LHPSC were 76.38% and 69.68%, respectively. The results presented in this study will provide further valuable guidelines for designing greenhouse heating system in severely cold regions