Sensitivity Analysis of Geothermal Heat Pump Performance Coupled with Climate-Geological-Borehole Heat Exchanger

Geothermal heat pumps are an efficient and low-carbon heating and cooling system. The operating performance of geothermal heat pump systems is closely related to the building climate, geology, and characteristics of the borehole heat exchanger (BHE). However, there are few studies on the comprehensive influence of multiple factors on the long-term operating performance of geothermal heat pump systems. In this study, three typical climate zones in China, namely severe cold region, cold region, hot summer and cold winter region, are selected, and a ground-source heat pump system model (GSHP) was established by TRNSYS. Using orthogonal experimental method, we studied the influence of factors such as storage thermal conductivity (ST), storage heat capacity (SH), fill thermal conductivity (FT), pipe thermal conductivity (PT), initial thermal gradient of storage (IS), temperature on top of storage (TO), initial surface temperature of storage (IS), borehole spacing (BS), and borehole depth (BD) on the coefficient of performance (COP) of the GSHP system over a 20 -year life cycle. The results of the sensitivity analysis showed that IS, BD, BS, FT and SH had a high degree of significance, while PT, ST and IT had a general degree of significance. The TO did not have significant influence. The ranking of significance effects from largest to smallest was IS <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$&gt;$</tex> BD <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$&gt;$</tex> BS <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$&gt;$</tex> FT <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$&gt;$</tex> SH <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$&gt;$</tex> PT <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$&gt;$</tex> ST <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$&gt;$</tex> IT <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$&gt;$</tex> TO, and the maximum COP of 5.16 could be obtained at the optimal factor level. The results of this study can provide scientific basis for GSHP performance optimization and COP long-term prediction analysis.