Experimental study of a domestic solar assisted ground source heat pump with seasonal underground thermal storage through shallow boreholes

Abstract

With the current need to reduce carbon emissions, new technologies have been developed in recent years to satisfy building thermal demands. Among others, ground-source heat pumps (GSHP) have been implemented, in both commercial and residential applications, to meet heating and cooling needs in a cleaner and more energy efficient way. Likewise, solar thermal systems have been integrated into conventional GSHP systems to reduce the size of the ground heat exchanger and provide seasonal heat storage. So far, this technology has been used in large commercial or residential buildings, mainly due to its high installation costs. This paper describes a study of an experimental Solar Assisted Ground Source Heat Pump (SAGSHP) system for domestic heating applications. The system uses an array of shallow (1.5-metre deep) vertical boreholes to store heat seasonally in an underground ‘earth energy bank’. The results show that after 19 months of operation the system was able to show a good performance in order to cover the space heating requirements of the building in winter. Likewise, it was evidenced that the solar energy injected in the ground is useful not only to recover the soil from the thermal imbalance but also to store heat. Results also highlighted the need to improve the control strategy, mainly to avoid excessive inlet fluid temperatures at the evaporator.