Optimization of ground source heat pump systems in dense urban environments with limited plot sizes

Abstract

In ground source heat pump (GSHP) projects, space limitations for placing boreholes can lead to ground thermal imbalance and suboptimal performance, making the systems unattractive for buildings with limited plot space. This issue is particularly severe in dense urban areas within Nordic climates, where small building plots cannot accommodate adequately sized bore fields to meet high heating demands. This paper addresses the problems caused by spatial limitations by utilizing an ambient air-assisted ground source heat pump (AAA-GSHP) system. This system maintains the thermal balance of boreholes through heat regeneration, allowing highly flexible design and placement of boreholes on building plots. Novel results are presented by optimizing system configurations — including the number, spacing, and depth of boreholes, as well as heat collector unit sizing — based on the available land area across various plot sizes. Optimization is implemented for both AAA-GSHP and conventional GSHP systems using detailed numerical simulations over a 50-year period. The results demonstrate that an optimized AAA-GSHP system achieves substantially higher performance and profitability on constrained plots compared to conventional systems. Depending on plot area, the ambient air-assisted system achieved a 3–26% lower levelized cost of energy, 0–42% lower life cycle emissions, and 0–80% higher heat pump energy production compared to traditional systems. The AAA-GSHP system met targeted energy production and emission goals with significantly lower investment costs. This study enhances the applicability of GSHP-based systems in areas where the conventional solution would often prove suboptimal.