Large Loudoun power users fired up diesel so families didn't lose power

RICHMOND, Va. - When the grid serving Virginia ran short in September, some of Loudoun County's largest electricity users unplugged and ran on their own diesel generators, sparing households the risk of rolling blackouts.

PJM Interconnection's compliance report to the U.S. Department of Energy shows six diesel units in Ashburn ran on Sept. 17 under emergency Order No. 202-26-45. Units VA1, VA2 and VA3 ran 8 hours each, VA5 ran 10 hours, and VA6 and VA10 ran 9 hours each.

PJM's resource list, Exhibit A, puts all six in Ashburn, ZIP 20147, with nameplate ratings of 7, 11, 13, 28, 21 and 18 megawatts, about 98 megawatts combined.

Who they are isn't public

The filing does not say who owns the Ashburn units or what kind of facilities they serve. Ashburn is known as the heart of Northern Virginia's data center corridor, and PJM said on Sept. 17 that the order let it "direct data centers and other large load customers to switch to backup generation resources, if necessary." But neither PJM nor DOE has identified the Ashburn units as data centers. Ownership isn't in the filing.

A 30-megawatt diesel unit in Gainesville, labeled CH1, was also on the list but didn't appear on the Sept. 17 report.

The trade-off

The idea is straightforward. Large power users with their own generators step off the grid in an emergency, freeing power for homes. PJM said so in its Sept. 16 application: letting large loads "rely on power generated by backup generation facilities could help the RTO avoid residential load shed at EEA level 3."

Residential load shed means cutting power to homes. EEA 3 is the grid's top emergency level, the point where operators can begin rolling blackouts. The order authorized backup generators "as a last resort before declaring an EEA 3 (i.e., before firm load interruption) or during an EEA 3."

For conservatives who have watched Richmond pile mandates on the grid while demand climbs, this is the system working the way it should. Private owners invested in their own backup power, and when the public grid needed help, they carried their own load.

The rules got out of the way

The order allowed backup generators to run "notwithstanding any applicable environmental limitations under federal, state, or local law or regulation," as PJM requested. For each Ashburn unit, Exhibit A lists the relaxed constraint as "Limitation on emergency engine operation." Hours run under the order don't count toward rolling-average limits, though owners must still monitor and keep records where practicable.

Generators protecting hospitals, 911 centers, water plants, defense sites, first responders, air traffic control and gas pipelines were exempt. Backup units used under the order don't count as capacity resources, so customers don't pay for them through PJM's capacity market.

How close it got

PJM forecast demand near 133,285 megawatts and a shortfall of about 700 megawatts below its reserve margin on Sept. 17. It said the squeeze was worst in the BGE, Pepco and Dominion zones. That morning, a plant serving those zones went offline unexpectedly, and PJM still hasn't named it. PJM called emergency demand response that afternoon.

The compliance report gives run hours only. It doesn't give power output or emissions for the Ashburn units.

The bigger picture

Northern Virginia's large power users are often blamed for driving up demand. September showed some of them can also help when the grid is short. The harder question for Richmond is why the grid needed a federal emergency order in mid-September at all. PJM pointed to heat, maintenance-season outages, transmission limits and exports.

The order was in effect through Sept. 18. The State Corporation Commission was copied.

Documents

The order, PJM's application, its supplemental letter and Exhibit A are posted on the Department of Energy's 202(c) page for Order No. 202-26-45 at energy.gov. PJM's daily compliance report for Sept. 17 is posted at pjm.com.

Loudoun County is a county in Northern Virginia. Its county seat is Leesburg.