Estuaries, where freshwater rivers meet the salty sea, are not only popular spots for birdwatching and kayaking but also hold great potential for sustainable energy generation. Researchers at ACS Energy Letters have developed a groundbreaking semipermeable membrane that efficiently harvests osmotic energy from salt gradients, converting it into electricity.
The innovative membrane design, showcased in lab demonstrations, boasts an impressive output power density over two times higher than existing commercial membranes. Osmotic energy, derived from the difference in salt concentrations, can be harnessed wherever salt gradients exist, offering a renewable energy source with significant room for technological advancements.
One approach to capturing osmotic energy involves a series of reverse electrodialysis (RED) membranes, acting akin to a ‘salt battery’ that generates electricity through pressure differentials caused by salt gradients. By leveraging the flow of positively charged ions from seawater to freshwater, such as sodium, the membrane experiences increased pressure, while maintaining low internal electrical resistance to facilitate electron flow in the opposite direction of ions.
Past studies have indicated that enhancing ion and electron transport across RED membranes could amplify electricity generation from osmotic energy. To address this, Dongdong Ye, Xingzhen Qin, and their team developed a semipermeable membrane using eco-friendly materials to minimize internal resistance and maximize power output.
Their innovative RED membrane features distinct channels for ion and electron transport, achieved by layering a negatively charged cellulose hydrogel for ion transport between organic, electrically conductive polymer layers for electron transport. Initial tests in a simulated estuary environment demonstrated a remarkable 2.34 times increase in output power density compared to a commercial RED membrane, while sustaining performance efficiency.
This breakthrough in osmotic energy harvesting not only showcases the potential for sustainable energy solutions but also highlights the importance of continuous innovation in renewable energy technologies. With further research and development, such advancements could pave the way for enhanced energy generation from salt gradients, contributing to a greener and more sustainable future.
