Echogen Power Systems

Stationary electrical energy storage plays several important roles in the U.S. electricity system, and these are expected to grow as the grid continues to evolve. Long-duration energy storage systems address grid needs beyond those covered by daily cycling. Such systems could provide backup power for several days, improving grid resiliency, or allow for the integration of even larger amounts of intermittent renewable sources like wind and solar. In the near term, such systems could help shape the output from individual wind and solar installations, improving the reliability of these resources and thus greatly increasing their value to the grid.

The Echogen Power Systems team will develop an energy storage system that uses a carbon dioxide (CO2) heat pump cycle to convert electrical energy into thermal energy by heating a “reservoir” of low-cost materials such as sand or concrete. During the charging cycle, the reservoir will store the heat that will be converted into electricity on demand in the discharge or generating cycle. To generate power, liquid CO2 will be pumped to a supercritical pressure and brought to a higher temperature using the stored heat from the reservoir. Finally, the supercritical CO2 will be used to expand through a turbine to generate electricity during the discharge cycle.

If successful, DAYS projects will provide new forms of long-duration stationary electricity storage systems that enhance grid resiliency, provide low-cost energy capacity, support grid infrastructure, and enable a greater share of intermittent renewable resources in the generation mix.