Parametric analysis and multi-objective optimization of building-integrated latent heat thermal energy storage units

The integration of phase change materials (PCMs) into building envelopes can enhance thermal storage performance. However, the performance of latent heat thermal energy storage (LHTES) units is governed by the coupled effects of external conditions and intrinsic PCM properties. Existing studies have often examined these factors separately and have mainly focused on single-objective optimization. To address this limitation, this study employed an integrated evaluation and optimization approach based on the taguchi method and grey relational analysis (GRA) to examine the combined effects of key external and internal parameters on the thermal performance of building-integrated LHTES units. Five key parameters were investigated using an L16 orthogonal array and numerical simulations, with melting time, total energy stored, and energy stored rate selected as the performance indicators. The entropy weight method (EWM) was used to determine data-driven indicator weights, while an equal-weighting scheme was introduced as a neutral benchmark. GRA was then employed to obtain a comprehensive performance index for multi-objective evaluation and to assess the robustness of the ranking under different weighting strategies. The results show that the overall importance ranking of the investigated factors remained unchanged under both weighting schemes, following the order of solar radiation intensity > melting temperature > latent heat > dynamic viscosity > copper foam porosity. Scheme 15 (solar radiation: 1000 W/m2, melting temperature: 308 K, latent heat: 250 kJ/kg, dynamic viscosity: 0.003 Pa·s, copper foam porosity: 0.95) was identified as the optimal configuration under both weighting schemes. These findings provide design-oriented guidance for the multi-objective optimization of building-integrated LHTES units by clarifying the relative importance of key parameters and identifying optimal parameter combinations.