Hydrophilic candle wastes microcapsules as a thermal energy storage material for all-day steam and electricity cogeneration

Abstract

On-site reclamation of freshwater from seawater is urgently desired to combat freshwater scarcity, in which solar-driven interfacial evaporation has been realized as a promising strategy. However, solar desalination has been facing the negative influence of intermittent solar radiation alternating day and night; thus, incorporating a material recommended as thermal energy storage material into the photoabsorber is a profitable strategy to supply the heat for 24-h steam generation. Herein, graphene oxide (GO) was incorporated with the candle waste to store the thermal energy and encapsulated into the SiO2 shell to prevent the leakage of the paraffine wax and enhance the membrane hydrophilicity. A collaborative device including the evaporator and a commercial thermoelectric (TE) module was designed for steam-electricity cogeneration which exhibits a simultaneous evaporation rate of 1.09 kg m−2 h−1 and power density of 6.8 W m−2 under one sun irradiation. Besides, the paraffin component can store thermal energy, enabling the device to maintain a certain steam and electricity cogeneration of 0.35 kg m−2 h−1 and 2.8 W m−2 after light-off. This work may provide a cost-effective strategy for the fabrication of potential photoabsorbers from environmental wastes for all-day water evaporation and power cogeneration device to mitigate freshwater and electricity shortages.