Multi-objective optimization of phase change material radiant floor coupled ground source heat pump under future climate scenarios

Coupling phase change envelopes with renewable energy sources is a promising strategy for achieving building decarbonization. However, the absence of climate-adaptive optimization frameworks constrains the performance potential of such integrated systems. This study develops a multi-objective framework for a phase change material radiant floor coupled with a horizontal ground source heat pump (PCM floor-HGSHP) system, evaluated under shared socioeconomic pathway climate scenarios. A TRNSYS-NSGA-II integrated model was established to assess energy, economic, and environmental optimization potentials across three building performance levels (energy efficient building (EEB), ultra-low energy building (ULEB), and nearly zero energy building (NZEB)). Results reveal distinct optimization priorities across building types. EEB benefits from cost-effective solutions with higher PCM melting points and larger system capacities to compensate for its weaker envelope. ULEB achieves a balanced trade-off among energy savings, carbon reduction, and economic cost through moderate system sizing and enhanced PCM characteristics. NZEB, due to its minimal heating demand, achieves the lowest emissions but exhibits diminishing returns in cost-effectiveness and efficiency due to part-load operation constraints. By 2080, cumulative heating load reductions reach up to 84.7 %. After optimization, the coefficients of performance of the heat pump and the overall system increase by 8.0 % and 14.3 % on average, respectively. The findings suggest that EEB should enhance envelope adaptability to reduce dependence on active controls, while NZEB requires improved part-load efficiency via dynamic system regulation. This study provides actionable insights into climate-resilient, low-carbon building design.