Charged up over energy storage
Duke Energy is getting charged up about batteries — and their potential for strengthening the power grid and adding renewable energy.
The company matched a $22 million grant from the U.S. Department of Energy to install a large-scale battery energy-storage system at our 153-megawatt (MW) Notrees wind farm in Texas.
Completed in late 2012, the storage system is one of the largest of its kind in the world. The system can store 24 megawatt-hours of electricity, enough to power about 18,000 average homes for one hour.
Battery storage can smooth out the inevitable weather-related fluctuations in wind and solar generation, making the power system more reliable. It can also respond almost instantly to spikes in energy demand.
Energy storage is nothing new to Duke Energy. The company has had pumped-storage hydro projects for years. During off-peak periods, these systems pump and store water for use in generating hydroelectric power when demand rises.
But storage using batteries promises valuable new options — especially in the area of grid stabilization.
At the Rankin Substation in Gaston County, N.C., a battery system is smoothing out large minute-by-minute production peaks and valleys from a 1.2-MW solar project a few miles away. It was honored by POWERGRID magazine as Project of the Year for integrating renewable energy into the grid.
Another project stores electricity produced by a 1-MW solar installation at Marshall Steam Station in Catawba County, N.C., and discharges it directly to the grid when needed.
Both projects are helping Duke Energy keep the grid stable when intermittent renewable generation is connected.
The company is also testing small battery systems at customers’ homes and businesses in Charlotte, N.C., and Carmel, Ind., for a variety of capabilities, including solar integration and backup power.
But Duke Energy isn’t stopping there. In 2013, the company will kick off a pilot project to repurpose previously used Chevy Volt batteries on the company’s distribution system. With about 70 percent of their original capacity remaining, used auto batteries may have a useful second life — boosting the reliability of the electric grid. This would also make used batteries more valuable, potentially reducing the overall cost of owning electric vehicles.