Dominion Energy recently received state regulatory approval to use developing battery storage technologies that could have major implications for the commonwealth’s renewable energy transition.
The projects include two battery systems at Darbytown Power Station, a natural gas plant in Henrico County. One will utilize an iron-air battery system; the other, a zinc-hybrid technology. An additional project to help power Virginia State University’s Multi-Purpose Center will use metal-hydrogen batteries.
Battery storage is expected to double on the United States electric grid in 2024.
But the lithium-ion batteries that make up most electric power storage can only discharge power for six hours or less at a time. If the future of the electric grid is to be powered by renewables within 26 years, as required by the Virginia Clean Economy Act, that might not be enough storage to get through one windless night.
“A long-duration battery will help you ride through a series of cloudy days or when the wind isn't blowing,” said Brandon Martin, Dominion’s business development manager.
The company’s recently-approved projects will use technology that utilities are only now starting to test out at grid-scale. The pilot projects fall into categories carved out by another piece of state law, the Virginia Grid Security and Transformation Act.
The Darbytown iron-air battery, slated for completion in late 2026, was developed by Form Energy and will use a process called “reverse rusting.” To charge, excess electricity is used to convert rust into iron. And when power is needed, oxygen is introduced, rusting the iron and releasing an electrical current.
The iron batteries can discharge power for up to 100 hours.
The VSU batteries, developed by EnerVenue, will offer about 10 hours of storage when completed in late 2027.
The projects are small — 8.94 MW at Darbytown and 1.5 MW at VSU — compared to Dominion’s offshore wind farm or its proposed natural gas plant in Chesterfield. But Martin said the battery projects will help Dominion understand how to ramp-up battery capacity for short- and long-term needs.
“Pilot projects like these across the country help build up the operational capabilities and understanding,” Martin said. “We want to spend time learning: Are they available when they're needed? And can you rely on them?”
Limits of lithium
There are other concerns over the mass adoption of lithium ion in battery storage, personal electronic devices and electric vehicles — everything from water usage and pollution in lithium mining to “modern-day slavery” and civil war in the Democratic Republic of Congo, where cobalt, an additive that extends the life of lithium cells, is mined.
Battery storage is an essential component of a renewables-powered electric grid. Unlike natural gas or coal, the sun or wind can’t just be turned on. And when renewables are producing, energy needs can be exceeded.
The grid managed by the California Independent System Operator services most of the Golden State.
Solar has covered more than half of the state’s minute-to-minute energy production between 8 a.m. and 5 p.m. almost every day this month. Solar, wind and hydro often exceed immediate demand, meaning they can charge the state’s biggest-in-the-nation battery fleet and be exported to neighboring grids.
So, when the sun goes down, batteries switch on, usually covering about 20% of electric demand at their peak each night.
But it’s a short-lived peak: CAISO’s batteries are usually spent by midnight, resulting in an increase in natural gas use and imports from more carbon-heavy neighboring power pools. Hydro power also ramps-up at night to reduce reliance on fossil fuels.
By comparison, storage on the much larger mid-Atlantic area grid managed by PJM Interconnection — which encompasses Dominion’s service area — produces less than 1% of the grid’s real-time electricity when the sun goes down.
Dominion’s storage outlook
According to Dominion spokesperson Tim Eberly, the utility has 114.04 MW of storage operational or approved for installation.
It also operates the Bath County Pumped Storage Station, which opened in 1985 and can store 3,000 MW. It essentially functions as a gravitational battery: Two reservoirs are located next to each other with 1,260 feet in elevation between them.
When the grid produces more power than is needed, that electricity is used to pump water from the lower reservoir to the higher one. And when demand for power is high, water is released into the lower reservoir, powering a hydroelectric plant as it goes.
Virginia state regulators also approved a 1.9 MW lithium ion array in Chesterfield County this month, slated to be operational in 2025.
The approved projects will cost about $90 million altogether, which will be recovered through base rates.
According to the company’s 2023 Integrated Resource Plan, Dominion plans to build out between 1,000 and 3,000 MW of storage capacity in the next 15 years.
