The appeal of fuel-agnostic power generation

Climate Energy

The appeal of fuel-agnostic power generation

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Flexibility during the energy transition will be key.

As the current energy crisis vividly illustrates, the withdrawal pains associated with ending the economy’s fossil fuel addiction and moving to clean, renewable sources are deeply painful. While purists and progressives champion a cold-turkey approach, reality requires the transition to alternative fuels for electricity and transportation to be more like an extended rehabilitation program. 

That’s one reason I’m intrigued by a breakthrough announced by Mainspring Energy, the well-funded company behind a revolutionary redesign of electric generators. It will help its customers avoid investing in climate tech that quickly becomes obsolete.

What makes Mainspring’s tech unique? Rather than relying on rotating magnets to generate electricity — as most engines have for more than 200 years — its technology is linear, sliding back and forth to produce power.

Soon, the generators will be able to run 100% hydrogen and 100% ammonia fuels directly, alongside other gaseous fuels. It’s the customer’s choice.

Most of the Mainspring models out in the field today, used by companies including Kroger, Lineage Logistics and NextEra Energy for on-site power generation and grid stability, are fueled by natural gas or biogas. The breakthrough is this: Soon, the generators will be able to run 100% hydrogen and 100% ammonia fuels directly, alongside other gaseous fuels. It’s the customer’s choice. As these alternative fuels become commercialized, older Mainspring units can be retrofitted to use them. And early adopters can have more confidence that the investment won’t be short-lived, as is often the risk with emerging climate tech.  

“Clean fuels are essential to decarbonizing the grid and supporting the rapid growth of solar and wind power,” said Mainspring CEO and founder Shannon Miller in the press release announcing its technological advance. “They provide all the advantages of fossil fuels — resilience, low-cost cross-seasonal storage and ease of transport — without the carbon.”

The viability of hydrogen and ammonia as clean, or at least cleaner, fuel sources is a subject of hot debate. Support is building for their potential to reduce the emissions of heavy-duty transportation, power generation, chemical production, etc. South Korea, for example, is pushing clean hydrogen as an important part of its clean economy future, projecting that it will account for about one-third of its energy by 2050. The actual cleanliness of these fuels relates directly to the fuel used to power their production. The only true green hydrogen is that which is produced with solar or wind power, still a relatively rare commodity.

In California alone, the collective power of diesel generators in the field today is about 12 gigawatts or roughly 15% of the state’s total grid capacity.

When I spoke with Miller about Mainspring’s new technology – which should be part of commercial units by the end of next year – she said her company is using its fuel-agnostic future to provide more confidence to commercial and industrial customers looking to get off diesel generators which are responsible for coughing up both substantial emissions and soot. In California alone, the collective power of diesel generators in the field today is about 12 gigawatts or roughly 15% of the state’s total grid capacity. Miller said that ammonia, in particular, promises to be a high-potential alternative for replacing diesel. 

One of the biggest challenges associated with running alternatives, such as hydrogen or ammonia, is that there can be performance disadvantages compared to fossil fuel sources. According to a company FAQ, there is a slight decrease when running the Mainspring linear generator on hydrogen. The ability to run on pure ammonia is unusual; fuel cells, for example, must convert ammonia to hydrogen, which results in an energy efficiency loss of 20% to 30%.

To a large extent, software can control the fuel mix used by a given Mainspring linear generator, which provides it with more flexibility than alternative technologies such as fuel cells or combustion engines, according to Miller. “You can move the oscillators to any position. It is all software-controlled,” she said. 

Mainspring’s latest announcement comes just a few weeks after it disclosed a big order from cold-storage warehouse operator Lineage Logistics, which plans to install up to 150 linear generators across its distribution facilities. In late May, the company also disclosed that it had closed more than $150 million in its Series E round from the likes of Lightrock, Khosla Ventures, Bill Gates and several other investors. That brings Mainspring’s total funding to $391 million, although the Series E fundraising isn’t over yet.

The technology’s footprint requires roughly the size of a parking space.

Mainspring also has a $150 million financing partnership with NextEra Energy that provides energy-as-a-service contracts for commercial and industrial customers that don’t want to take on the capital investment. When I asked about pricing, Miller declined to be specific but said the costs associated with the linear generator are similar to those for a conventional engine and lower than for fuel cells. The technology’s footprint requires roughly the size of a parking space. 

A fuel-agnostic future?

To be clear, Mainspring Energy isn’t the only company talking up fuel flexibility. In February, one of the world’s biggest combustion engine companies, Cummins, announced powertrain technology that will also support a transition to alternative fuels. Its new “fuel-agnostic” equipment is capable of running diesel, natural gas and hydrogen. 

Cummins’s press release touts the technology’s benefit: “This means it will be easier for OEMs to integrate a variety of fuel types across the same truck chassis, and there will be minimal costs to train technicians and re-tool service locations, resulting in a lower total cost of ownership for the end-user.”

Some companies that use Cummins for engines include Paccar, Navistar International, Volvo Trucks North America, Daimler Trucks North America and Ford.

Flexibility during the transition will be critical, a concept that both Mainspring and Cummins are lauding. “Having a variety of lower-carbon options is particularly important considering the variation in duty cycles and operating environments across the many markets we serve,” said the president of the Cummins Engine Business, Srikanth Padmanabhan, in the press release about the new technology. “There is no single solution or ‘magic bullet’ that will work for all application types or all end-users.”

This article originally appeared on as part of our partnership with GreenBiz Group, a media and events company that accelerates the just transition to a clean economy.

Written by

Heather Clancy

Heather Clancy, GreenBiz editorial director, is an award-winning business journalist specializing in chronicling the role of technology in enabling corporate climate action and transitioning to a clean, inclusive and regenerative economy. She started her journalism career on the business desk of United Press International, and her articles have appeared in Entrepreneur, Fortune, The International Herald Tribune and The New York Times. Clancy was the launch editor for the Fortune Data Sheet, the magazine's newsletter dedicated to the business of technology. She co-authored the Amazon best-seller for entrepreneurs, "Niche Down, How to Become Legendary By Being Different."