Volume 64

Energy flexibility of PCM-configured envelopes under Hong Kong time-of-use tariffs: a parametric simulation Haoxiang Zhan, Guanjing Lin

Abstract

Buildings in warm-humid climates exhibit pronounced midday cooling peaks, which makes demand-side flexibility under time-of-use tariffs especially valuable. Phase change materials configured in the envelope of walls and roofs can provide latent storage, yet performance under realistic tariffs with explicit hysteresis remains under-quantified. This study develops a reproducible, tariff-linked workflow that couples EnergyPlus with a hysteresis-consistent PCM model and automates a jEPlus parametric sweep. A medium-office archetype in Hong Kong is simulated under a representative four-block tariff, testing overnight pre-cooling to 22 to 24°C and midday set-point relaxation to 24.5 to 25 °C, with the PCM melting range aligned to the cooling band. Performance is evaluated using the flexibility factor, on-peak and off-peak energy shifting, peak load moderation and tariff-based cost. The combined strategy delivered a 48.7% daily cooling-cost saving relative to the non-PCM baseline, with on-peak cooling energy reduced by 34.3%, off-peak use increased by 131.1%, and on-peak peak cooling load and peak electric demand reduced by 21.3% and 19.7%, respectively. Single-lever strategies yielded smaller gains, and neglecting hysteresis distorted the timing and magnitude of peaks. The results show that material properties and control could be co-designed, and they provide a transferable workflow with decision-ready indicators for PCM-enabled, tariff-responsive design in warm-humid offices.

Keywords phase change material (PCM) envelope; building energy flexibility; peak demand reduction and load shifting; parametric optimisation