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

• Published in: Applied thermal engineering 2019-11, Vol.162, p.114218, Article 114218
• Main Authors: Naranjo-Mendoza, Carlos, Oyinlola, Muyiwa A., Wright, Andrew J., Greenough, Richard M.
• Format: Article
• Language: English
• Subjects: Boreholes; Building; Commercial buildings; Efficiency; Energy storage; Evaporators; GSHP; Heat exchangers; Heat pumps; Heat storage; Heat transfer; Installation costs; New technology; Photovoltaic-thermal collectors; Pumps; Residential buildings; Residential energy; Seasonal storage; Shallow boreholes; Solar assisted ground source heat pump; Solar energy; Solar heating; Space heating; Thermal energy; Underground storage
• ISSN: 1359-4311; 1873-5606
• DOI: 10.1016/j.applthermaleng.2019.114218

•A shallow solar assisted ground source heat pump was experimentally studied.•The ground heat exchanger consists of 16 shallow boreholes of 1.5-m deep.•Heat is seasonally stored in a volume of soil insulated on the top and sides.•The usable heat from the PVTs is limited by the size of the ground heat exchanger.•The heat stored helped to cover heating loads and to prevent soil thermal imbalance. 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-m 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.