Last week, the U.N. hosted a summit on sustainable development, including access to clean water. I have previously written about declining water levels in the western U.S. and the use of desalination to transform seawater into freshwater. Although over 17,000 desalination plants are operating worldwide, there are only about 325 in the U.S., with 45% in Florida, 14% in California, and 9% in Texas. The reason they have not been more widely adopted is traditionally, they are expensive to build and use a lot of energy. Most of the desalination plants operating today heat the salt water and pump it through specialized membranes that separate the water from the salts.