Potential evaluation of energy flexibility and energy-saving of PCM-integrated office building walls

Building energy flexibility is important for reducing peak-to-valley differences in air-conditioner loads. Integrating phase change material into office building envelopes and precooling can effectively reduce peak load, but precooling may increase total energy consumption. Therefore, it is imperative to investigate its energy flexibility and energy consumption features. In present work, a heat transfer model of phase change material (PCM)-integrated office building walls was established firstly and verified by experiments. Then, the energy flexibility and energy-saving potential of the PCM-integrated wall under different precooling strategies were studied, and the effects of various PCM parameters on energy flexibility and energy-saving potential were evaluated. Finally, the influence of different peak-to-valley electricity tariff differences on electricity costs was analyzed. The results show that the optimized precooling strategy and peak-tovalley electricity tariff difference make the energy flexibility index of the PCM-integrated wall up to 69.7% at a total load reduction of 1.3% and save the electricity cost by 51%. The PCM location and melting point have the most significant effect on the energy flexibility and energy-saving potential of the PCM-integrated wall under precooling operating conditions. This study guides the selection of energy flexibility and energy-saving precooling strategy and PCM parameters for PCM-integrated office building walls and the formulation of time-of-use tariff policies.