by James A. Bacon
A utility-scale battery storage system has gone online at Dominion Energy’s Scott Solar Facility in Powhatan County, according to the Richmond Times-Dispatch. During the day when solar output is peaking, excess energy is rerouted to the batteries. When the sun goes down and output falls, batteries release electricity back into the grid. The 12-megawatt battery complex can power 3,000 homes for up to four hours.
The purpose of the Scott Solar project is to give Dominion real-world experience in understanding how batteries can integrate into the larger electric grid. Dominion officials contend that battery storage can be a more cost-effective way to meet high-demand periods than, in the RTD’s words, building “an entirely new generation facility.”
The “levelized cost” of electricity, which includes up-front capital costs, operating costs, and fuel costs (which are zero for solar) over the lifetime of the project, is lower for solar than any other energy source available on a large scale in Virginia. However, solar farms are part of a larger system that must meet the demand for electricity 24/7. Solar facilities, while highly cost-efficient on a stand-alone basis, are highly variable. Output cannot be dialed up and down as needed. Therefore, they require significant backup. Batteries are one means of providing that backup. And batteries have a cost.
A 2019 Dominion press release said that Scott Solar would be one of three lithium-ion battery projects in Central Virginia totaling $33 million to build. The plan was to evaluate their performance over a five-year period. The two Scott Solar battery systems totaled 12 megawatts, while battery systems in Ashland and New Kent Counties totaled four megawatts. Assuming that the cost per megawatt was roughly the same, the Scott Solar batteries cost in the realm of $25 million.
To get the true sense of the cost of solar-generated electricity, the $25 million cost of the batteries must be added to the original $50 million cost of the solar park, adding 50% to the cost. And that doesn’t take into account the backup Dominion needs for when clouds block the sun and output falls off significantly for days at a time. The batteries, designed to supply power for four hours after the sun has been shining, can’t come close to making up for such a deficit. Providing fallback electricity sources will entail an additional cost.
Perhaps solar+batteries will prove to be both economically competitive and compatible with grid reliability even when all costs are taken into account. We’ll have a better idea when Dominion gets some experience with the batteries. Dominion’s 2019 press release mentions a five-year evaluation period. That will be complete in 2027, giving the utility only 18 years to complete the design and overhaul of its General Assembly-mandated transition to a net-zero electric grid.