Multifunctional solar bamboo straw: Multiscale 3D membrane for self-sustained solar-thermal water desalination and purification and thermoelectric waste heat recovery and storage

Abstract Solar desalination and purification based on interfacial evaporation have great potential to alleviate global water scarcity. However, real-world interfacial evaporation suffers from several issues in clean water collection and solar-to-clean-water energy efficiency. Here, a new concept of multifunctional natural membrane interfacial evaporation (MNMIE) is demonstrated, achieving the whole cycle of energy conversion from solar energy harvesting to waste heat recovery and storage while effectively desalinating and purifying water. The 3D, multiscale membrane derived from sustainable bamboo presents a mean pore size of 150 nm and a porosity of 63.8%, comparable to the commercial membranes. The as-generated vapor from a self-sustained evaporation process is guided to permeate through the porous bamboo node into the bamboo chamber facing unfocused incident light (1 sun) and then condenses, resulting in a high water collection ratio of 81.0% and solar-to-clean water efficiency of 67.4%. Moreover, the waste heat from desalination is recovered through direct thermoelectric energy conversion and storage under unfocused solar light. The fully integrated cycle of energy conversion, storage, and utilization for clean water and electricity generation enabled by the multifunctional natural membrane is scalable, economic and represents a highly promising solution for sustainable energy cycles enabled by nanotechnology-empowered natural resources.