Solar PVT-assisted regeneration of boreholes with thermal imbalance in GSHP systems: a techno-economic analysis
Unbalanced ground source heat pump (GSHP) systems in cold climates can experience ground cooling and reduced performance over the long-term. This study evaluates whether unglazed PV/thermal hybrid collectors (PVT) can restore performance when added after ten years of GSHP operation. A single-family house is simulated for 20 years, with four PVT designs introduced from year eleven onward to assess effects on seasonal performance factor (SPF), auxiliary-heater use, borehole temperature, thermal balance, and life-cycle cost. All PVT configurations produce an immediate SPF4+ increase of 0.6 % to 0.9 % and stabilize 1.3–1.6 % above the GSHP-only case by year 20. Borehole temperatures, which decline from 7.0 °C to 5.6 °C during the first decade, recover to 6.4–6.6 °C, and 40 % of extracted heat is reinjected over the PVT period. However, total life-cycle costs rise by 31–54 % due to high capital costs. PVT therefore offers limited technical benefits and remains economically challenging under current cost conditions for a fully sized borehole field. Future work should examine older systems and heat-pump replacement scenarios.