Fundamentally, energy and water resources are deeply interconnected. This presents urgent demands for impactful innovation in light of trends in population and energy consumption. Appropriate technologies can substitute for water in two of its three main roles (thermal medium, solvent, and biological medium); however, innovation is needed as these technologies have evolved over time from engineering needs, and not first-principles scientific thought.
Central research priorities in the water-energy nexus are water-free energy generation, CO2 sequestration, low-energy separations, and enhanced fluids. Above all else discussed in the article, water pretreatment is presently a mystery and could transform future water and energy landscapes on an ultimate path to sustainable energy generation with no water waste.