Virginia Regulatory Town Hall
Department of Environmental Quality
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3/1/23  10:49 pm
Commenter: Joel Yu, Enchanted Rock

Technical Analysis and Policy Recommendations on Order and Local Variance for Data Centers

Dear DEQ leadership and staff:


            Enchanted Rock writes with a shared commitment to support Virginia’s position as an economic powerhouse and a world-renowned data center hub, while promoting local air quality improvements and bolstering the reliability, resiliency, and affordability of the electric grid that serves as the foundation for further economic growth. We understand the current electrical reliability circumstances and support the DEQ’s near-term actions to protect grid reliability. Our comments, however, are focused on reducing going forward risks and impacts of continued reliance on diesel backup generation.


Enchanted Rock is a leader, nationally, in resiliency microgrids with over 1,000 MW of microgrid capacity in operation or under construction in Texas, California, Virginia, and several other states, serving a broad range of critical customers like data centers, manufacturing operations, and defense facilities. Since 2014, we have been laser focused on helping customers and communities pivot away from highly polluting diesel backup generation by deploying our ultra-clean gas microgrid technology.


Technical Analysis Utilizing EPA Co-Benefits Risk Assessment (COBRA) Health Impacts Screening Tools Indicate Material Health Impacts from 5 Months of Diesel Backup Contingent Operation


Based on conservative estimates using the EPA’s COBRA tool, the DEQ action under consideration today could result in up to several million dollars of public health impacts to the residents of Virginia in just the few months that the variance would be in effect.









Table 1: Total Health Effects for Virginia (per 5 months)



Diesel, $/MWh

Natural Gas, $/MWh












In order to calculate this impact, we used the emissions factors for Tier 2 diesel, the standard technology choice for backup power today, versus Enchanted Rock’s natural gas microgrid technology. The Tier 2 Diesel hydrocarbon and NOx emissions rates are combined into one standard. To calculate the emissions factors of VOC and NOx, we used a proxy for the ratio of Non-Methane Hydrocarbons (NMHC) to NOx using the Tier 4f standard (.19 NMHC/.4 NOx). The NMHC value calculated for VOC is an overestimate because it includes ethane, which VOC does not. It is notable that Enchanted Rock’s engines reduce particulate matter emissions by over seventy-nine percent when compared to the cleanest Tier 4 diesel technology and a reduction of volatile organic compounds and nitrous oxide emissions by over ninety percent.


Table 2: Emissions Factors for Tier 2 Diesel and Natural Gas, per 10,000 MWh of Generation


Mt/10,000 MWh Generation






Tier 2 Diesel





Natural Gas






The model estimates health impacts on a state-level basis. We used the emissions factors above and a 3% discount rate. The low and high values represent differences in methods used to estimate the health impacts in COBRA. For example, the high and low results for avoided premature mortality are based on two different epidemiological studies of the impacts of PM2.5 on mortality in the United States.


Table 3: Health Costs per MWh of Diesel v. Natural Gas Generation in Virginia


Diesel, $/MWh

Natural Gas, $/MWh












Finally, we pulled 2022 PJM data on Post Contingency Local Load Relief Warnings, MW deficiencies and event durations. We made conservative estimates around the total GWs of generation that could be called via the order and local variance from a claim by Dominion Energy about data center capacity connected since 2019.[1]


Table 4: Estimated Generation Capacity and Runhours

Average Size of Generator, MW


Run Hours per Generator


Total Data Centers


Generators per Data Center


Total Generation, MW



Additionally, based on the estimated amount of generation, fuel usage[2], and run hours, we estimate that the counties could see about 3,500 trucks (assuming 11,000 gas tankers) on the road to make necessary refueling deliveries. The health impacts of the refueling deliveries by diesel trucks was not modeled in our impact analysis.


Policy Recommendations


While relief is on the way with transmission projects in progress, it is likely that the growth of Northern Virginia’s electrical demand will continue to outpace the available capacity of the broader grid and diesel generation will be called upon to bolster reliability in the future, to the detriment of local communities. PJM has noted that generation is retiring faster than new supply can come online[3] not to mention the continuing trend of data center growth and electrification of everything. Transmission planning and deployment, with its associated permitting timelines and siting challenges, will not keep up.


In light of these challenges for the grid, we recognize the need for the current measures. However, the state must act now to prevent further proliferation of and reliance on diesel backup generation for data centers, other critical energy users, and for grid support. Highly polluting Tier 2 and Tier 4 diesel engines continue to be approved and sited even while there are commercially proven technologies that can provide superior technical performance and significantly reduced local criteria pollutant emissions, all while providing more dispatchable, local capacity for the grid.


Enchanted Rock’s natural gas generators substantially reduce local emissions and our engines run as quiet as some residential dishwashers. As a result, our microgrids can run in support of the grid with minimal impacts to the surrounding community. We have already partnered with utilities in similar situations around the country to deploy these microgrids rapidly and cost effectively.[4] Furthermore, we are working with a top four hyperscaler to deploy our microgrid supplied with renewable natural gas (RNG) to achieve net zero operations in alignment with state and federal decarbonization goals.[5]


With proven, cleaner alternatives readily available, policymakers should consider urgent actions to encourage the transition away from diesel, including:

  • updated backup generator permitting standards, i.e., updating the Best Available Control Technology;
  • expedited permitting for projects using clean alternatives to diesel;
  • incentives or other mechanisms to encourage the selection of natural gas generators; and
  • support for natural gas infrastructure to allow for cleaner alternatives at designated data center expansion areas.


Enchanted Rock is committed to supporting the DEQ in efforts to secure cleaner air and more reliable power for Northern Virginia.


Thank you for your consideration.

[2] Diesel engines use about 70 gal/MWh. Diesel Generator Fuel Consumption Chart - Hardy Diesel

[4] See Entergy’s recently approved Power Through program in Louisiana. Power Through | Entergy | We Power Life

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