Emerging Technologies Address the Water-Energy Nexus

Some of the most promising technologies target thermoelectric power plants, which not only are the largest single source of water withdrawals in the U.S. but also convert less than half of their primary energy to electricity, according to the report (see Saving Water by Conserving Energy). One solution is the use of supercritical carbon dioxide (SCO₂) recompression in a closed-loop Brayton cycle (RCBC).

Because carbon dioxide is denser than water and has a higher thermal storage capacity, this process uses less energy during recompression and recovers more waste heat, both of which also reduce cooling requirements. According to the report, this technology could improve total plant efficiency 3%-4% and could be applied to existing coal plants, nuclear reactors, and concentrating solar power towers. The materials needed to handle the requisite pressures and high power densities are expensive, but DOE recently produced a working prototype, and researchers have reported positive results at pilot scales.

Other emerging technologies covered by the report include advances in cooling systems, alternatives to fresh water for oil and gas production, desalination techniques, and methods for recovering energy and nutrients from wastewater.