Location combination optimization of thermal insulation material and phase-change material in multi-layer walls under air-conditioning continuous and intermittent operation

Abstract The multi-layer wall often employs the Thermal Insulation Material (TIM) or Phase-Change Material (PCM) layer to improve its thermal performance. To gain the location groups of the TIM and PCM layers, four wall models are built with air-conditioning continuous and intermittent operation, while temperature and heat flow in inner surfaces are used to evaluate the wall thermal performance by employing the numerical model with phase-change thermal transfer process. The result shows the air-conditioning operation mode has the large influence on optimizing the relative location of the TIM and PCM layers. Locating the PCM layer in the wall inside is the better choice with the higher applicability on outdoor thermal environment under air-conditioning continuous operation, while locating the TIM layer in the wall inside is the better one with the higher energy-saving contribution under air-conditioning intermittent operation. Air-conditioning intermittent operation can save 46.69–64.73% of the energy consumption but increase the peak load of urban electricity system, compared to air-conditioning continuous operation. However, for the multi-layer wall with the TIM layer in the wall inside, this negative effect is too small to be valued, compared to the higher energy-saving contribution.