One in ten human beings does not have access to clean potable water, a number that the United Nations predicts will more than quadruple in the next 13 years, mostly due to population growth in developing nations. These water needs can be met by desalination of ocean water but that requires a capital investment exceeding one trillion U.S. dollars. Therefore, development of affordable technologies to desalinate salt water for human consumption and agriculture is important. Toward this, my group recently invented a process for sunlight-driven desalination that can theoretically generate potable water 20 times faster than the competing process of solar thermal distillation. Central to our approach is a mechanism for direct conversion of sunlight into ionic power that we have demonstrated using inexpensive and scalable sheets of plastic.