High Performance Wood Scroll Evaporator for All-Day Evaporation in Saline Water

A novel all-day evaporator in the form of a scroll is developed by rolling a thin layer of wood. Two different wood layers are used to fabricate a wood scroll with diagonal natural water channels (d-WS) and a wood scroll with parallel natural water channels (p-WS). Vertical water transport through gap channels (i.e., spaces between the overlapping wood layers) is >10 times higher than that through natural water channels. Because only diagonal channels allow water transport across the wood layer, d-WS exhibits good lateral water transport whereas p-WS exhibits poor lateral water transport. The synergistic effect of the gap channels and diagonal channels in d-WS increases evaporation performance. The total evaporation rate of water of d-WS is 9.08 kg m⁻² h⁻¹ in the absence of wind, which increases to 37.95 kg m⁻² h⁻¹ in the presence of 2 m/s wind. These evaporation rates are among the highest values ever reported under similar conditions. Furthermore, the difference between the evaporation rates of p-WS and d-WS increases with height. The higher evaporation rate of d-WS is attributed to the presence of diagonal channels, which enhances lateral water transport to the outermost surface, where dark evaporation occurs. The difference in lateral water transport affects not only the dark evaporation rate but also salt resistance. The evaporation experiments are conducted in a 3.5 wt% NaCl solution under 1 sun illumination. No salt is observed on the top surface of p-WS, but a significant amount of salt is accumulated on the side surface, indicating that the gap channels facilitate sufficient water supply to the top surface, but the microchannels alone fail to supply sufficient water to the side surface. Interestingly, no salt accumulation is observed on both the top and side surfaces of d-WS. The excellent salt resistance of d-WS is attributed to the synergy between its gap channels and diagonal channels, which enables sufficient water supply to the top and side surfaces. The evaporation rate of d-WS does not deteriorate even after 5 days, demonstrating the possibility of long-term operation.