In many regions of the world, freshwater is scarce, but saltwater is abundant. Desalination methods such as reverse osmosis, solar thermal desalination, or capacitive deionization can help to alleviate this scarcity. Research in this field has often focused on reducing the generally high energy consumption of these processes by developing improved materials. These materials can, e.g., be better membranes for reverse osmosis or materials with better light absorption for solar processes.
Menachem Elimelech, Yale University, New Haven, CT, USA, and colleagues have analyzed the efficiency of these advanced materials in reducing the energy cost of desalination technologies. The team found that for reverse osmosis, there has been a significant amount of work on membrane materials with enhanced permeability to improve energy efficiency. However, the actual reduction in energy cost is small. The researchers point out that a focus on improving water/salt selectivity might be more promising.
Thermal desalination can have a very high energy consumption, but might be the best method for water with a high salt content. Here, efficient solar absorber materials have been in focus. However, the team found that better process design (e.g., by recovering latent heat) and developing materials with improved stability could be more useful ways to improve these techniques.
Capacitive deionization is an electro-driven desalination technology in which an electric field is used to remove ions from water. Research in this field has generally been aimed at better electrode materials. However, the team found that this has little effect on the method’s energy efficiency, which is poor overall.
According to the researchers, desalination technologies are fairly mature and future improvements in energy consumption might only be marginal. They recommend a focus on robustness, reliability, and reduced waste instead.
- The relative insignificance of advanced materials in enhancing the energy efficiency of desalination technologies,
Sohum K Patel, Cody Ritt, Akshay Deshmukh, Zhangxin Wang, Mohan Qin, Razi Epsztein, Menachem Elimelech,
Energy Environ. Sci. 2020.