By SEAN SUBLETTE Richmond Times-Dispatch
POWHATAN — In an effort to curb global warming, solar and wind power are increasingly becoming part of the country’s energy infrastructure. The energy costs of these sources over their design life are decreasing, as neither requires a regular fuel source after their initial construction.
Because the sun doesn’t shine at night and the wind isn’t constant, utility-scale batteries are beginning to make up the difference in keeping the flow of electricity reliable.
Last week, batteries of utility scales at Dominion Energy’s Scott Solar facility in Powhatan County has gone live, which means the batteries are now actively charging and discharging on a daily basis. The battery system is configured on an automatic schedule that can be adjusted according to seasonal changes and local electricity demand during a day.
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Location of the batteries next to the solar farm logical to load them. During the day, the solar panels move with the sun across the sky for optimal solar power generation, so there are times when more power is generated than can be immediately used. This excess energy from the solar panels is routed back to the batteries for storage and can be used later. In the case of Scott’s installation, it’s for peak purposes.
The 12-megawatt battery at the Scott site can power 3,000 homes for up to four hours. Although it may not seem like much, batteries are not designed to store energy when other systems fail. Rather, they are designed to supplement during short periods of high demand. Imagine the surge in demand for electricity in the late afternoon when hundreds of thousands of people come home from work and cook dinner, turn on screens and change their air conditioners to a cooler setting.
Batteries are well suited for this process because current technologies limit how long they can provide power once fully charged. According to Eric Conner, structural engineer and head of production construction at Dominion, this is a more cost-effective way to meet limited, high-demand periods than building an entirely new production facility to meet this application.
In addition to the immediate impact during times of high demand, these batteries give Dominion real-world experience to understand precisely how this type of energy storage infrastructure will fit into its larger power grid.
Designed to last 15 to 20 years, these utility-scale batteries, called BESS (Battery Energy Storage System) look like nondescript gray shipping containers, about 50 feet long and 8 feet wide. This allows them to be shipped without special oversized permits.
Within each BESS case are smaller components working together to store and release energy.
Conner uses a binder analogy to describe the inner workings. “Individual cells are like folders in a filing cabinet, with 10 cells making up a module and 17 modules going into a rack.”
These are wired together in a sequence (aka, daisy-chained) to optimize performance.
Locating the batteries next to the solar farm was a simple decision. The solar farm has been operational since 2016, with a peak capacity of 17 million watts of power.
To make more sense of this number, start by converting this number from power to energy: multiply by the duration of use of the power.
On a typical electricity bill, energy used is measured in units of kilowatt hours, or 1,000 watts of power used for one hour. A typical home consumes about 30 kilowatt hours per day.
The solar farm was developed by Virginia Solar and purchased by Dominion in 2018. Like most solar installations, these panels are not static, but rotate during the day in order to follow the sun as it crosses the sky, obtaining light the most direct part of the sun towards the panels.
According to Conner, the panels don’t require much maintenance. Solar panels generally do not need to be cleaned, as regular rain is enough to wash away heavy impurities on their surfaces. The panels also generate heat, enough to melt the snow that falls on them during the winter.
And although clouds impact the amount of sunlight reaching the panels, there is always some light reaching the panels, even on the cloudiest day. Although the power generated is lower on these days, it is far from zero.
Conner recognizes the current limitations of renewable energy and the importance of batteries in maintaining a reliable supply of energy.
“The combination of solar and wind is really appealing,” he said. “Because the [offshore] the wind also helps offset the solar peak. The wind does not produce the most in the middle of the day like the solar. It produces more in the evening.
But for those worried about reliability, Dominion’s Jeremy Slayton reminds customers that renewables are far from the only tool in Dominion’s energy toolbox.
“Battery storage is an integral part of Virginia’s clean energy transition,” Slayton said. “In addition to battery storage, combustion turbines play a vital role in keeping the lights on when the sun isn’t shining and the wind isn’t blowing.”
Coal may be on its way out, Dominion is playing to withdraw coal units from Chesterfield power station next year. But natural gas isn’t going away anytime soon.