Sunday, March 12, 2023

DEQ Amends its Data Center Diesel Generator Variance

After the Public hearing on February 27, 2023 in Woodbridge, the Virginia Department of Environmental Quality (DEQ) has decided to revise the proposed variance for data centers originally published on January 26, 2023, to restrict its application to emergency generators located at data centers in Loudoun County only, removing Prince William and Fairfax Counties from the proposed variance.

Data center operation relies on the use of large amounts of electricity from the grid. Due to the fast pace of growth in data centers in Northern Virginia Dominion Energy has not kept up with the surging demand for power. According to Dominion Energy, the transmission constraints will persist until at least 2025 and probably 2027. According to PJM the currently operating data centers could cause a cascade failure in the power grid during periods of high demand.

Maintaining an adequate level of generation resources, with the right operational and physical characteristics, is essential for PJM’s ability to serve electrical demand through the energy transition mandated by the Virginia Clean Economy Act of 2020. PJM anticipates that retirements of fossil fuel electricity generation are outpacing the construction of new electrical generation resources; and expects that the growth rate of electricity demand will continue to increase from electrification coupled with the proliferation of additional high-demand data centers in the region. The sheer size of the load needed for data centers and its flat profile throughout the day, require more name plate generation by variable sources in addition to  transmission capacity. So in their most recent report PJM indicated the electrical supply constriction may exist far beyond the period of the current variance, Spring 2023 and need to be renewed.

In the revised variance DEQ voices concern that Loudoun County is an area in which there may not be a sufficient amount of electricity available for data centers due to these severe, localized constraints in electricity transmission and demand. To prevent knocking out the entire region, in times of grid stress, they need for the data centers to power down. However, to keep operating, the data centers would need to step off the grid and use their generators. The data centers will be paid a bonus to step off the grid.

This proposed order and local variance would provide data centers located in Loudoun County a measure of relief from existing regulations and permit provisions that limit the use of Tier II and Tier IV emergency generators. Under the variance, data centers in Loudoun Count may operate their Tier II and Tier IV generators during periods that PJM has initiated a "Maximum Generation Emergency/Load Management Alert" or during periods that PJM has declared a "Post Contingency Local Load Relief Warning" for Loudoun County. According to the Washington Post: “Since 2020, three “Maximum Generation Emergency Load Alerts” have been issued — all of them last year, according to the PJM website.” The second category, “Post Contingency Local Load Relief Warnings” — are issued far more common, with 90 occurring in Dominion’s coverage area last year.  

DEQ estimates that there are approximately 4,021 diesel-fueled Tier II generators (older and of higher emissions) and 130 Tier IV (lower emissions) generators located at data centers in Loudoun County. The likely potential pollutants from a generator could include nitrogen oxides (NOX), particulate matter (PM10 and PM2.5), carbon monoxide (CO), volatile organic compounds (VOCs), and sulfur dioxide (SO2). The exact number and duration of events, if any, that may occur before the end of July 2023 when this variance ends cannot be predicted. However, by federal regulations limit the amount of nitrogen oxide emitted by permit holders to 100 tons per year and DEQ estimate the emission per hour per generator. With those restraints all the generators could run approximately 5.13 days this is the potential emissions in Ashburn for this variance.


The comment period has been extended through April 21, 2023. A new public hearing will be conducted in the Conference Room, Northern Regional Office, 13901 Crown Court, Woodbridge VA, at 11:00 a.m., on Thursday, April 6, 2023 the second day of Passover.


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