Comprehensive performance of a novel radiative cooling phase change roof: An experimental study

Incorporating phase change materials (PCMs) into the roof is considered an effective measure to reduce the amount of heat gain from the roof in hot climates. However, there are two challenges: short PCM melting time during the daytime and incomplete PCM solidification during the nighttime. Hence, in this paper, a new roof coupling radiative cooling coating with composite phase change material (RC-PCR) was purposed. The thermal performance and thermal comfort of ordinary roof (OR), phase change roof (PCR), and RC-PCR were experimentally investigated. The results show that RC-PCR outperformed the other 2 types of roofs in reducing peak interior surface temperature of the roof, average interior surface temperature of the roof, peak indoor air temperature, and average indoor air temperature. Furthermore, the PCM in RC-PCR was not completely melted throughout the day, whereas the PCM in the PCR was completely melted after only 3.0-5.1 h. Besides, RC-PCR was better than both PCR and OR in controlling internal surface temperature fluctuation and indoor air temperature fluctuation. More importantly, after analyzing cooling energy consumption reduction, operative temperature, and discomfort hours reduction, it was found that chamber C with RC-PCR had lower cooling energy consumption and a more comfortable indoor thermal environment in summer than chamber A with OR and chamber B with PCR. In winter, RC-PCR had a slightly negative effect. In conclusion, the reduction in cooling load achieved by RC-PCR in summer is significantly greater than the increase in heat load experienced in winter. RC-PCR is particularly well-suited for hot climates where cooling energy consumption is dominant.