Replacing Diesel: Gas, Turbines, Steam for AI Data Centers. 6 Min Read. Tight EPA Tier 4 standards for nonroad engines raise the bar on NOx/PM, making new diesel backup harder to permit while gas units continue to gain share.Getty. In this four-part series exploring potential substitutes for diesel generators, we have examined battery energy storage systems (BESS) (seePart One) and advanced power electronics (Part Two). In this installment, we examine what is replacing diesel for backup power and what can stand in for grid power when interconnections lag, focusing on natural gas reciprocating engines, gas turbines, and steam turbines fed by packaged boilers.. Natural Gas Engines: A Cleaner, Reliable Replacement for Diesel. For years, backup strategies have been shifting from diesel generators to natural gas reciprocating engines – the same basic technology that powers automobiles. On regulated pollutants such as particulate matter and nitrogen oxides, natural gas units typically achieve lower emissions than comparable diesel engines, especially when equipped with modern controls and after-treatment. Carbon dioxide intensity per kilowatt-hour can also be lower, although results depend on factors such as engine efficiency and site-specific operating profiles. Emissions comparisons should be considered alongside methane management in the upstream gas supply chain.. Related:Utilities Say Data Centers Could Lower Electricity Bills. Regulators Want Proof. A study by the National Lab of the Rockies (NLR) found both diesel and natural gas systems to be reliable, with natural gas generators reported as slightly less likely to fail during an outage. In many regions, natural gas supply is considered more dependable than diesel fuel availability. While operating costs for both remain higher than grid power, backup units typically run only during outages or grid events. Notably, NLR highlighted that lower fuel costs per kilowatt-hour make natural gas engines more attractive than diesel for revenue-generating grid support, enabling grid-connected generators to assist the grid during emergencies or peak periods rather than serving only the data center.. Gas Engines Move Up the Stack. Beyond displacing diesel in traditional backup roles, natural gas engines are increasingly providing primary power when grid interconnections are delayed or unavailable.. For example, a data center project in Ohio plans to deploy 15 Wärtsilä Energy 18V50SG gas engines to deliver nearly 300 MW of on-site power.. Caterpillar likewise secured a 2 GW order from American Intelligence & Power Corp. (AIP) for its Monarch Compute Campus in West Virginia. The project will use Cat G3516 Fast Response natural gas generator sets. Paired with BESS, they will absorb the extreme load swings AI data centers can experience. The 2,250-acre site could eventually add up to 6 GW more. These engines can ramp from zero to full load in approximately seven seconds and will run on natural gas with emissions controls, including selective catalytic reduction (SCR), to achieve ultra-low emissions and comply with air permits.. Related:How a Coal Plant in Buffalo Became TeraWulf’s 500 MW AI Campus. Gas Turbines: Competing for On-Site Prime Power. Gas turbines rarely serve as one-for-one replacements for diesel backup, although smaller mobile units can fill that role in certain contexts. Instead, they most often compete with gas engines as on-site prime power. Turbines can achieve lower levels of nitrogen oxides, carbon monoxide, and volatile organic compounds, while reciprocating engines more commonly rely on SCR and oxidation catalysts to meet comparable environmental standards.. Demand from major OEMs – GE Vernova, Siemens Energy, and Mitsubishi Power – has reportedly driven lead times for large turbines out to the end of the decade and beyond for some models. In response, smaller suppliers package natural gas turbines on trailers and tow them to a data center for rapid deployment. Dynamis Power Solutions, for example, offers trailer-mounted units from 8 MW to 70 MW. Historically used at remote, off-grid oil and gas sites that relied on diesel generators, these mobile turbines are now gaining traction in data centers. They can be moved from site to site – brought in to supply power during construction and early operations, then removed once grid power arrives – or left on-site to serve as backup.. Related:Can Data Centers Ditch Concrete – or Just Use Less of It?. Dynamis says its DT24 Mobile Power Plant is capable of 24 MW of power at 13.8 kV. (Image: Dynamis Power Solutions). Even without nearby pipelines, gas can be delivered. Certarus, a subsidiary of Superior Plus Corp. based in Houston, transports compressed natural gas (CNG), providing road logistics, along with on-site gas decompression and pressure regulation. One US hyperscale operator is using CNG until a permanent pipeline connection is ready.. “We are currently supplying gas to over 120 MW of on-site power for data centers and just announced another 135 MW project slated to start in 2027,” said Scott Williams, director of industrial sales at Certarus.. Where pipeline gas is readily available, AI factories are installing all the turbine capacity they can secure. For example, the Oracle/OpenAI Stargate site being built in Abilene, Texas, uses a mix of turbine power, including GE Vernova LM2500XPRESS mobile gas turbines and Solar Turbines Titan 350 units. Envisioned as one of the world’s largest AI campuses in the world, Stargate Abilene could grow to 4 million square feet across eight buildings and consume as much as 1.2 GW.. “AI data centers will require another 60 GW of new power capacity per year by 2030,” noted Shen Wang, an analyst at research firm Omdia.. Steam Turbines and Packaged Boilers: A Fast-Track Alternative. As gas turbine backlogs lengthen, some operators are revisiting a proven play: using industrial boilers to generate steam for steam turbines.. According to Gerardo Lara, vice president of boiler sales at Rentech Boiler Systems in Abilene, Texas, the most practical option is a packaged boiler – a factory-made, pre-engineered, self-contained unit with burners, controls, and accessories for rapid installation and minimal on-site work. Lead times are about one year, he noted.. “With demand for power so high, a packaged boiler can be used to feed steam to a steam turbine to generate energy at about the same efficiency level as a gas turbine used during peak hours,” Lara said. “Steam turbines, too, are likely to be much faster to deliver to a data center than gas turbines in the current market.”. Steam turbine manufacturers such as Howden, Siemens Energy, Triveni, and Ebara Elliott have supplied these machines for decades across nuclear, geothermal, combined-cycle gas, and concentrated solar plants.. A fire packaged watertube boiler. (Image: Rentech Boilers). Diesel Sunset. Federal policy is gradually curbing diesel use in transportation, and EPA Tier 4 standards for nonroad engines sharply limit nitrogen oxides and particulate emissions. New data centers specifying diesel backup can expect tougher permitting. While the latest diesel generators mitigate many legacy emissions issues, natural gas engines continue to claim a larger share of backup generation.. At the same time, gas engines are gaining favor for prime power applications due to shorter lead times than gas turbines in many cases. Expect both gas engines and turbines to be deployed in record numbers over the next few years as hyperscalers and AI factory developers race to build larger, more compute-intensive facilities.. In Part Four of this series, we explore technologies that are less mature or not yet widely deployed but are gaining attention.. About the Author
