Study on coal units conversion into clean energy storage facilities


United StatesMalta has joined forces with Duke Energy to study the socioeconomic, environmental and operational benefits of converting retiring coal units into long-duration, zero-emissions energy storage systems.

This can be done by integrating Malta’s 100-megawatt, 10-hour pumped heat energy storage system into existing infrastructure at a Duke Energy coal plant in North Carolina. A U.S. Department of Energy grant is funding the year-long study of the emerging technology.

Malta’s energy storage system

Malta is developing a pumped heat energy storage system that stores electricity either directly from a power plant or from the grid by converting electricity into thermal energy (heat and cold). Heat is stored in molten salt, a decades-old and proven method of storing thermal energy. Cold is stored in an antifreeze-like solution with components and subsystems widely used in the liquefied natural gas industry.

The system operates like a conventional power plant. When electricity is needed, the thermal energy powers a heat engine to produce clean, reliable energy.

The study

Though the study will focus on the energy industry’s current need for 10-12 hours of energy storage, the Malta system can be configured to store up to 200 hours of energy storage. The study’s deliverables include an engineering conceptual study, a technology maturation plan and a socioeconomic report on potential benefits.

The Department of Energy announced the grant in March, and the team is identifying which of Duke Energy’s six coal plants in North Carolina is best suited to serve as the test site.