Mainspring Energy closes on more than $150 million in Series E funding

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Mainspring Energy, which provides linear generators for microgrids, has closed on more than $150 million in first stage Series E funding, led by global growth equity investor Lightrock and joined by Khosla Ventures, Bill Gates, Fine Structure Ventures, the private equity firm affiliated with the parent company of Fidelity Investments, Princeville Capital, Lineage Ventures and others.

Mainspring Energy

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Mainspring will use the funds to develop new linear generator models and to accelerate use of the generators by businesses, data centers and utilities.

The California-based company also has signed an agreement with Lineage Logistics, a temperature-controlled industrial REIT, and logistics solutions provider, to deploy up to 150 linear generators across its network of distribution facilities in the United States.

The two companies will also explore bringing the Mainspring generators to markets outside of the United States and the use of green fuels to power the fuel-flexible units.

Linear generators are electromechanical devices that directly convert motion along a straight line into electricity using chemical or thermal energy. Mainspring’s generators can be dispatched on demand and emit zero carbon.

Mainspring is the brainchild of three Stanford University engineers, who were seeking a new approach to generating clean, resilient, affordable electricity. Their research into high-efficiency methods of converting fuel to electricity led to the founding of the company in 2010 and the development and prototype of its first linear generator.

Learn more about the technology at Microgrid 2022 in Philadelphia, where Mainspring Energy will present a workshop, “How to Accelerate the Transition to 100% Renewable Generation with Microgrids,” 1:15 p.m. to 2:15 p.m., June 2.

The workshop will include examples from several customers with varied load profiles and operational requirements. Speakers will educate participants on the firming generation opportunities available in renewable microgrids and will discuss the value of net-zero carbon power generation with clean fuels such as biogas, green hydrogen and others in displacing diesel backup generation.

The panel will be moderated by Kevin Normandeau, publisher of Microgrid Knowledge. Featured speakers are Wayne Johnson, manager of key segment management for education at Duke Energy; Adam Simpson, co-founder and chief product officer at Mainspring Energy; and John Igo, vice president, business development at Mainspring Energy.

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About Elisa Wood

Elisa Wood is the chief editor of She has been writing about energy for more than three decades for top industry publications. Her work also has been picked up by CNN, the New York Times, Reuters, the Wall Street Journal Online and the Washington Post.