State environmental regulators want to make it easier for data centers in Northern Virginia to run on diesel generators in the event of a grid emergency. The measure is described as a precautionary step to protect the region's power grid, which is facing constraints due to the rapid growth of the data center industry.
The proposal by the Virginia Department of Environmental Quality is similar to practices during grid alerts in California, where data centers can switch to generator power to reduce the strain on the electrical grid, freeing up more electricity for residential customers. The measures would be invoked in the event of emergency declaration by the PJM Interconnection, which oversees the regional power grid on the East Coast.
Power constraints in Northern Virginia have been in the news since last summer, when Dominion Energy began telling data center companies that power for some new facilities in Eastern Loudoun County will be delayed until 2026 due to bottlenecks in the utility’s transmission infrastructure, which has not kept pace with the dynamic data center growth in Northern Virginia.
The language in the DEQ proposal suggests that even after limiting new data center connections, the region's grid could face challenges in coming months.
"An area in Fairfax, Loudoun, and Prince William counties has been identified in which data centers may not be able to obtain enough electricity due to transmission problems anticipated from March through July," the DEQ said in a press release. The agency also said "the period between March and July 2023 has been identified as a time of potentially acute stress on the transmission capacity of the grid."
"Dominion Energy identified the area of stress and timing of this variance need," said Aaron Proctor, Communications Manager for the Virginia Department of Environmental Quality.
Dominion said the variance was a precautionary measure while it continues to strengthen the region's transmission system.
"Out of an abundance of caution, DEQ proposed the temporary variance as an additional tool for data centers in case it’s necessary," said Aaron Ruby, Manager, Media Relations for Dominion Energy. "To be clear, transmission capacity is not constrained outside of 'Data Center Alley' in eastern Loudoun, and does not impact service to residential or small business customers, or any customers outside of the area."
Why Generators Matter
Data centers are designed to ensure that mission-critical applications never go offline, which is usually achieved through layers of redundant electrical infrastructure, including uninterruptible power supply (UPS) systems and emergency backup generators. Most backup generators run on diesel fuel, which generates emissions that contribute to pollution and climate change.
Virginia regulates the number of hours that data centers can run their diesel generators, while allowing exemptions for grid emergencies. The proposed DEQ variance goes a step further to waive those restrictions, while requiring companies to track and report their generator runtime and emissions.
“We are proposing this temporary and redundant variance out of an abundance of caution to maintain the reliability of the Internet and the electric grid while enabling data centers to continue serving their customers,” said Virginia DEQ Director Mike Rolband. “We will closely follow this developing situation and will use our robust compliance and permitting programs to ensure our environment remains protected.”
The variance specifies two scenarios that would trigger the emissions waiver :
- A Maximum Generation Emergency/Load Management Alert, an emergency situation where PJM seeks to add generating capacity while implementing "demand response" programs to reduce load on the grid.
- A Post Contingency Local Relief Warning, in which PJM notifies transmission system owners that equipment in a specific area is becoming overloaded and usage must be immediately reduced.
How California Manages Grid Alerts
California has periodically used warnings and brownouts to manage stress on the state's grid. In August 2020, the Infrastructure Masons called on its California members to shift to generator power, noting that they could run diesel engines without penalties or having the usage count towards strict annual limits.
During last September's heat wave, a number of California data centers participated in the Demand Side Grid Support (DSGS ) program. NTT Global Data Centers has shared details of its participation, in which it shifted 22 megawatts of load to its diesel generators during periods when the grid was strained by 110-degree heat.
Sources in the Northern Virginia data center community said if the restrictions are relaxed, more data centers might be willing to use their generators to reduce load on the grid. But they also noted that unlike California, there is no structured utility demand response program in Northern Virginia. Participation would be optional.
"The variance does not require data centers to operate their generators during PJM warnings, but allows them to do so if they wish," said the DEQ's Proctor, who noted that data centers operating their generators under the variance must comply with its notification provisions.
Although the variance would apply to data centers in Fairfax and Prince William counties as well as Loudoun, it does not suggest any change in the geography of the transmission constraints.
"Prince William and Fairfax were included in an abundance of caution," said Proctor. "However, the variance only applies to the specific areas within those counties for which the (PJM) warning applies."
Data Center Growth Strains Grid Capacity
The baseline challenge is that data center demand in Northern Virginia is growing faster than the utility grid. The region houses data centers that support Internet hyperscale platforms like Amazon Web Services, Microsoft, Google and Meta, as well as many enterprise companies. There is 26 million square feet of data center space in Loudoun County, with about another 5 million square feet in development, and many more projects in the planning stages.
In July, Dominion Energy began telling data center companies that power for some new facilities in Eastern Loudoun County will be delayed for years. The delays are due to bottlenecks in the utility’s transmission infrastructure.
"Data center load growth in that area has the potential to cause system constraints," said Daniel Lockwood, Strategic and Shareholder Communications at PJM. "PJM and Dominion are working to build out the transmission system to support this load growth."
Dominion is accelerating work on a 500kV transmission line in Southern Loudoun County, which is expected to be completed in 2026 and will relieve many of the transmission bottlenecks that are limiting new connections for data centers in Eastern Loudoun. Ruby said the company has other projects in the works as well.
"We’re continuing to develop several near and long-term transmission projects to alleviate the constraints in eastern Loudoun," said Ruby. "The first of the projects will be completed in late June."