Ground-Source Heat Pump Performance Enhanced with Earth Charging by Means of Solar-Air Thermal Collectors

This paper summarises the performance monitoring of Solar-Air thermal panels acting as a supplementary source to a Ground Source Heat Pump (GSHP). In the UK, experimental and theoretical data using this type of configuration has not been reported to the best of the authors’ knowledge. Given a possibility to use shorter boreholes and higher heat extraction from the ground, solar-air thermal panels could economically be combined with the GSHP; an experimental system has been installed on a full size occupied detached two-storey house in the city of Nottingham, UK. The south-facing solar-air panels collect solar heat on sunny days, bright-sky, and air warmth even during summer nights to warm the glycol/water. The heated glycol/water is sent directly to the borehole then to the GSHP for immediate needs (real-time), and surplus heat is retained the same day (diurnally) during winter and equinox. The solar-air panels continue to work through the summer and are large enough to capture long term warmth to prepare for the following winter season (inter-seasonal). Data were collected in real time. In the initial testing, the real time and diurnal benefits have been immediately realised. The results show that there are advantages with recharging the ground (soil battery); firstly this may increase seasonal performance of the heat pump if the lower soil temperature is maintained at 12°C; this also enables the heat pump to work closer to an expected coefficient of performance (COP) of 4.0, instead of the annual average of 2.65 predicted by the manufacture.