Bacon's Rebellion

The (Battery) Acid Test

Dominion coupled solar rooftop at Randolph Macon College with experimental battery storage.

Dominion Virginia Power is running experiments to see how well battery storage works with solar electricity. The verdict so far: mixed. 

Last year Austin-based ViZn Energy Systems had developed a zinc-iron redox battery system, the product of eight years of work, which it touted as safe, efficient, durable and flexible. The battery, the company stated, could absorb excess electricity when the sun was at its peak, inject power into the grid when production faded, and smooth over short, spiky fluctuations in voltage as output varied with cloud cover.

When Dominion Virginia Power opened a 50 KW roof-top solar installation at Randolph-Macon University in Hanover County in April 2015, it installed one of ViZn’s 48 kW “flow” batteries along with a smaller, 7 kW “wet cell” battery to test in real-world conditions.

“We wanted to evaluate and demonstrate some different battery technologies, explains Brett Crable, director of new technology and energy conservation. A big question was how the batteries would stand up to continual charging and re-charging.

As it turned out, the flow battery did not meet expectations from a reliability standpoint, says Crable. When the lease on the battery system expired, Dominion chose not to renew it.

As Dominion prepares to integrate increasing volumes of intermittent solar and wind power into its distribution system, it is looking at battery storage as one tool for dealing with the inevitable fluctuations of voltage and power. PJM Interconnection, the regional transmission organization of which Dominion is a part, says the high-voltage transmission system can handle up to 30% wind and solar without making it vulnerable to blackouts. But Dominion wants more hands-on experience with its lower-voltage distribution lines (which connect substations to homes and businesses) before committing to battery storage on a large scale.

Unlike the batteries people buy for home use, one size does not fit all in an industrial application. Batteries have varying characteristics depending upon the chemical composition and internal structure. Some batteries are designed for power (releasing electricity faster) and others for energy (total electricity stored). Some hold up better than others from charging and re-charging. Some are toxic, others non-toxic.

“As technology evolves, you look at power, energy, durability and safety,” says Crable. “Depending upon the application,  you’re looking for different characteristics.”

In addition to its small-scale deployment at Randolph-Macon, Dominion is testing a lithium-ion battery at an experimental solar facility in Kitty Hawk, N.C.

Among the dozens of battery deployments around the country, the Randolph-Macon project is one of only two facilities in Virginia using battery storage at the moment, according to the  U.S. Department of Energy Global Energy Storage Database. The other is a 25 kW zinc bromine flow battery at a Visa data center in Loudoun County.

Electro-chemical energy storage projects in northeastern quadrant of U.S.

While Crable sees battery storage as useful for narrow applications, he doesn’t regard it as practical for residential and small business customers who fantasize about going off the grid.

Say you’re an individual homeowner with a house of average size and energy consumption, he says. You’ll need about 5 kW capacity of solar to meet your needs during normal weather conditions. To keep the juice flowing on nights and cloudy days, you’ll need to augment the solar panels with a battery. If you want enough power to keep on the lights for four days — enough to sustain you through a long winter storm — that would be a very large battery. Then you’d need enough solar panels to fully recharge that battery while also meeting your household needs….which would require even more solar panels You probably don’t have enough rooftop to hold them all.

“Battery storage is complementary,” Crable says. “But as a replacement for the power grid, it is not economic or cost-competitive.”

The grid is evolving and modernizing, he says. “Solar will be part of that, and battery storage will continue to evolve and play an important role.” But it’s too early to say whether Dominion will deploy battery storage on a large scale in the future. “We always seek to learn.”

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