Reciprocating Engine Technology Supports Grid Flexibility And Renewables Integration

Modern reciprocating engines are enabling reliable power generation while balancing renewable energy growth. Their rapid-response capabilities and multi-fuel flexibility are crucial to grid stability. Real-world applications and emerging sustainable fuel options demonstrate how this technology bridges current power needs with future environmental goals.

In an era where grid reliability and flexibility are paramount, reciprocating engine technology has emerged as a crucial component in modern power generation systems. These versatile engines, which operate on the same fundamental principles as automobile engines but on a much larger scale, provide unique advantages that complement the evolving needs of our electrical infrastructure. Their ability to start quickly, adjust output rapidly, and operate efficiently across varying loads makes them incredibly valuable assets in a grid increasingly dependent on intermittent renewable energy sources.

The integration of reciprocating engines into power plants (Figure 1) addresses several critical challenges facing today’s electrical grid. Unlike larger combined cycle gas turbine (CCGT) plants that may take hours to reach full capacity, engines can achieve full power within minutes, providing essential backup during unexpected demand spikes or renewable energy shortfalls. This rapid-response capability, combined with their modular nature, allows power plant operators to precisely match generation to demand, improving overall system efficiency.

1. Heber Light and Power, a public power provider based in Heber City, Utah, operates a reciprocating engine power plant featuring Caterpillar technology. Courtesy: Caterpillar

Beyond their operational flexibility, reciprocating engines represent a bridge between traditional and future power generation paradigms. Their ability to run on various fuels, including natural gas, biogas, and hydrogen blends, positions them as adaptable assets in the transition toward cleaner energy sources. As utilities work to balance reliability with environmental responsibility, engines provide a practical solution that supports grid stability while accommodating the growing integration of renewable energy resources.

“The integration of intermittent renewable energy resources to the power grid is still a challenge for our customers,” Michael Fiedler, senior business development manager for the Power segment with MAN Energy Solutions, told POWER. “Here, our gas engine power plants are an ideal match to close the gaps in the energy supply by balancing the fluctuations caused by intermittent renewable energy resources. We are convinced that flexible and decentralized, gas-fired power plants will play a decisive role for a secure power supply on the pathway toward 100% renewable energy.”

Fiedler said an increasing number of combined heat and power (CHP) plants is already relying on gas engine technology. “Especially in Germany we are actually leading in gas-engine-powered CHP plants with numerous projects in cities such as Chemnitz, Frankfurt an der Oder, and Schäbisch-Hall. Especially in regard to the decision to phase-out coal in Germany, these gas-fired CHP plants will gain importance since they use resources more effectively—with high overall efficiencies of over 90%—and consequently emitting less CO2,” he said.

Gas engines are also an ideal match for the power requirements of data centers. These applications especially need a reliable and flexible power supply in order to ensure a very high availability. Further integration of renewable energies into the grid, leading to fluctuations in the power supply, can result in the requirement for a data center to temporarily reduce its power consumption from the grid. In these cases, a gas engine power plant can be ramped up and down quickly to compensate for fluctuations in the energy supply. By doing so, the use of renewable energy can be maximized at all times, keeping costs and the carbon footprint as low as possible while ensuring a reliable energy supply.

Meanwhile, a gas engine power plant is also an excellent option for non-grid-connected data centers. Engines are a proven and reliable technology that can provide the necessary flexibility for artificial intelligence (AI) data centers, which are expected to have a fluctuating load profile. Furthermore, if the data center gets a grid connection after-the-fact, the power plant can be used for providing grid services.

“For example, the U.S. is currently the country where the most data centers are being planned and built worldwide,” Fiedler said. “Data centers in the U.S. currently require about 25 GW of power generation capacities. It is estimated that this will rise to 47 GW by 2030. In order to meet this demand, the necessary investments in the energy supply are estimated at around $50 billion. Gas engine power plants play an important role here to secure the supply at any time of day and in any weather.”

Natural gas remains the primary fuel for most reciprocating engine power plants, offering relatively clean combustion and widespread availability through existing infrastructure (Figure 2). However, the true value of these engines lies in their ability to operate on multiple alternative fuels, often with minimal modifications. In addition to pipeline natural gas and liquefied natural gas (LNG), many engines can be designed to run on petroleum gas from oil production, biogas from landfills or wastewater treatment plants, synthetic gas from biomass gasification, propane as a backup fuel, crude oil and heavy fuel oil (HFO) in certain models, hydrogen blends (typically up to 25% hydrogen with natural gas), mine gas from coal operations, and field gas from oil and gas operations.

2. Four 20V35/44G TS gas engines with a total capacity of 48 MW were supplied by MAN Energy Solutions for a recently built power plant in the Indonesian city of Cicarang. Courtesy: MAN Energy Solutions

This fuel flexibility is crucial for several reasons. First, it provides energy security and reliability. If one fuel source becomes unavailable or cost-prohibitive, plants can switch to alternative fuels with minimal downtime. This is particularly valuable in regions with uncertain fuel supply chains or during natural disasters that might disrupt primary fuel delivery.

Second, it enables plants to take advantage of market opportunities. When prices fluctuate between different fuel types, operators can switch to the most economical option, helping to maintain competitive electricity prices for consumers. This ability to arbitrage between fuels can significantly impact a plant’s operational economics.

Third, fuel flexibility supports environmental goals and regulatory compliance. As emissions regulations evolve, plants can transition to cleaner fuels without requiring complete equipment replacement. The ability to use renewable fuels like biogas or hydrogen blends also helps utilities meet renewable portfolio standards and reduce their carbon footprint.

Lastly, this versatility makes reciprocating engines particularly valuable in remote or island locations where fuel availability might be limited or inconsistent. Plants can be designed to run on whatever fuel sources are locally available, reducing dependence on imported fuels and enhancing energy independence.

“Our future-proof gas engines offer a clear path toward net zero,” Fiedler said. “Already today, our gas engines can run on a variety of climate-neutral fuels such as biogas and synthetic natural gas (e-methane) derived from green hydrogen. Also, our 35/44G TS, 51/60G, and 51/60G TS gas engines are already ‘H2-ready’ and can be operated with a hydrogen proportion of up to 25% by volume in the gas mixture. At the same time, we are working on future concepts that will enable hydrogen fueling of up to 100% as soon as hydrogen becomes available in large quantities.”

Caterpillar is another engine provider that has expanded its line of gas generator sets capable of running on hydrogen fuel. Caterpillar now offers gas gensets ranging in power from 400 kW to 4.5 MW, each with the capability of blending natural gas with up to 25% hydrogen by volume.

Scala Data Centers, a Latin American platform of data centers in the hyperscale market, completed a “proof of concept” (POC) confirming the technical feasibility of using hydro-treated vegetable oil (HVO), also known as “green diesel,” in its Caterpillar backup generators. Derived from renewable sources, green diesel undergoes a hydro-treatment process, transforming it into a high-quality fuel with reduced environmental impact. Replacing fossil diesel with HVO can decrease greenhouse gas emissions by up to 85%, according to Scala, which it said supports the company’s commitment to sustainability. During the POC, conducted by Scala’s Center of Excellence in Engineering in collaboration with its operations team and Sotreq, Caterpillar’s dealer in Brazil, HVO demonstrated “excellent performance in backup generators, maintaining critical resilience of data centers without requiring changes to existing equipment,” the company reported.

“We closely monitored Scala’s test on Caterpillar equipment in a pioneering initiative in Latin America,” Mauricio Garcia, director of Sotreq’s Power Unit, said in a statement. “The use of HVO in generators opens up a universe of possibilities, in addition to ensuring lower maintenance costs, preserving equipment, and reducing greenhouse gas emissions.”

However, HVO is three times more expensive than diesel fuel at the present time in Latin America. Therefore, the widespread implementation of HVO in Scala’s operations is not expected immediately. “We closely monitor market trends, hoping to identify opportunities that could make the use of HVO economically viable on a larger scale,” the company said. “We anticipate that movements like ours will raise awareness within the supply chain about the substantial demand potential for HVO, prompting stakeholders to explore more attractive commercial terms conducive to its widespread adoption.”

In the U.S., more than 8 million gallons of HVO has been used to generate power by customers using Cat rental power solutions supplied by Peterson Power Systems, the local Cat dealer for electric power in northern California, Oregon, and southwest Washington. The Cat rental power solutions using HVO fuel have been predominantly used by utilities to supply energy around the clock during public safety power shutoffs and after wildfires damaged grid transmission lines in northern California. In Norway, STACK Infrastructure, a global developer and operator of data centers, implemented the use of HVO100—the purest form of HVO—as a standby power source for a new data center on its OSL04 campus in Holtskogen (Oslo).​

“We have already implemented power plants with engines operating on biofuels, as our recent contract with French utility EDF for a 130-MW power plant on the island of Corsica [France] underlines,” Fiedler said, noting that MAN Energy Solutions is also seeing demand for engines that can operate on synthetic fuels derived from electrolysis, such as green hydrogen, e-methane, and ammonia. “Already today, our engines can be designed to operate on climate-neutral fuels like e-methane or be retrofitted at a later stage, based on availability of the fuels,” he added. Furthermore, Fiedler said MAN Energy Solutions is collaborating with partners on two projects, called AmmoniaMot and HydroPoLEn, to develop advanced hydrogen and ammonia solutions. Both projects are supported by the German Federal Ministry for Economic Affairs and Climate Action.

—Aaron Larson is POWER’s executive editor.