Solar-assisted borehole thermal energy storage coupled with heat pump for livestock buildings: results from a full-scale installation

Livestock farming is an energy-intensive sector of agriculture and a significant contributor to greenhouse gas emissions. This study presents the first-year pperational results of an integrated renewable energy system combining photovoltaic–thermal (PVT) collectors, borehole thermal energy storage (BTES), and a dual-source heat pump (DSHP) for space heating in a commercial swine nursery building. The BTES is based on a novel “double-circuit” configuration, allowing the exploitation of solar energy during mid-season and summer periods, while ensuring reliable heat supply during winter peak loads. A monitoring system, including dedicated piezometers aligned with groundwater flow, was implemented to continuously record environmental conditions inside the building, system operating parameters, energy flows, and subsurface temperature variations. During the first year, the system met the heating demand of the nursery barn, achieving an overall Seasonal Performance Factor (SPF) of 3.78. Approximately 54% of the heat pump operation occurred in hybrid ground–air mode, 38% in ground-only mode, and only 7% in air-only mode, demonstrating the effectiveness of the strategy in balancing performance and resource preservation. The installed system employed only 240 m of borehole heat exchangers, compared to an estimated 640 m required for conventional systems delivering comparable thermal performance. Subsurface monitoring confirmed that the thermal impact on the aquifer was limited and remained well below regulatory thresholds. The results demonstrate that solar-assisted BTES coupled with a DSHP represents a technically effective, energy-efficient, and environmentally compatible solution for decarbonising heating in livestock buildings, particularly in rural areas with available land and suitable hydrogeological conditions.