The U.S. Department of Energy has announced the selection of 10 projects as part of a new Advanced Research Projects Agency-Energy (ARPA-E) program, Duration Addition to electricitY Storage (DAYS). Awardees will develop energy storage systems to provide reliable, affordable power to the electric grid for up to 100 hours, enhancing grid resilience and performance. Under Secretary for Science Paul Dabbar announced the DAYS awardees today at the Innovation XLab Energy Storage Summit at SLAC National Laboratory.

“The Department of Energy is committed to researching innovative energy technologies and discovering opportunities to make America’s energy infrastructure more competitive and more secure,” said Under Secretary Dabbar. “The DAYS awardees will take a good look at what tomorrow’s grid-scale storage could be, and work to develop the technologies that get us there.”

Most energy storage systems deliver power over a limited time to alleviate congestion, stabilize grid frequency and voltage, or provide intraday shifting services. DAYS projects’ extended discharge times will enable a new set of applications for grid storage, including long-lasting backup power and greater integration of intermittent, renewable energy resources.

DAYS projects will explore a new design space in electricity storage, exploiting opportunities for smart tradeoffs that keep costs low in electrochemical, thermal, and mechanical systems.

DAYS project teams will work to combine the long-term power output of technologies like pumped storage hydroelectric (PSH) systems with the flexibility of battery systems that can be deployed in multiple environments. PSH power provides more than 95% of stationary electricity storage capacity on the U.S. grid today, but there have been few new installations due to geographical and financial challenges. Lithium ion batteries, meanwhile, have experienced a rapid growth in deployment on the grid, but high cost limits viability in long-duration applications.

A selection of DAYS projects are below. The full list of selected projects can be viewed HERE.

PROJECT 1

Brayton Energy, LLC – Hampton, NH

Improved Laughlin-Brayton Cycle Energy Storage – $1,994,005

The Brayton Energy team will develop an energy storage system that combines thermal storage and a gas turbine to generate power. When the system is charging, an electrically driven heat pump will accumulate thermal energy in a molten salt solution, which can then be discharged later by heating gas and sending it through the generation turbine. Brayton Energy’s innovation lies in their reversible turbine design, in which each turbine acts as the compression stage for the other, whether during charging or discharging. This approach simplifies the system and increases durability.

PROJECT 2

Echogen Power Systems (DE), Inc. – Akron, OH

Low-cost, Long-duration Electrical Energy Storage Using a CO2-based Pumped Thermal Energy Storage System – $3,000,000

The Echogen Power Systems team will develop an energy storage system that uses a carbon dioxide (CO2) heat pump cycle to convert electrical energy to thermal energy by heating a “reservoir” of low cost materials such as sand or concrete. The reservoir will retain heat that will be converted back into electricity on demand. To generate power, liquid CO2 will be pumped through the high-temperature reservoir to a supercritical state, after which it will expand through a turbine to generate electricity from the stored heat.

For more information on ARPA-E’s DAYS program, click here.