Study on a novel phase-change wood roof integrated with diurnal photovoltaic conversion and nocturnal sky radiative cooling

Wooden buildings offer significant carbon reduction benefits due to their renewable nature. This study develops a phase change wood roof photovoltaic coupling system that lowers panel temperature during the day to maintain efficiency and releases stored heat at night. Using vacuum impregnation, white poplar wood achieved a paraffin loading of 41.6%, with latent heat capacities of 55.9 J/g for phase change material-38 and 54.5 J/g for phase change materia-23. Epoxy encapsulation reduced mass loss from 1.38% to 0.29%. We constructed indoor and outdoor experimental platforms to test phase change materials, showing that phase change materia-23 reduced indoor temperature fluctuations by 2.91 °C, while photovoltaic coupling further alleviated heat retention. In outdoor tests, phase change materia-23 notably lowered the noon peak indoor temperature by 2–3 °C compared to normal wood. At night, the interior wall temperature of photovoltaic phase change wood is 1–2 °C lower than that of photovoltaic normal wood structure buildings. Phase change materia-23 also achieved 13.93% photovoltaic efficiency, 4.81% higher than the reference module. A numerical model predicted that phase change materia-23 reduces annual temperature fluctuations by 4.73 °C in tropical humid climates and phase change materia-38 by 8.07 °C in arid regions.