What is a linear generator?

Utilities are under pressure to deliver generation that is dispatchable, affordable, and clean enough to satisfy increasingly stringent environmental rules, notoriously hard to do in one asset. As renewables grow, the gas turbines and engines that have historically filled the gap come with a NOx problem, a CO2 problem, or both. Hydrogen offers a path through, but the supply isn't there yet. So what do you build today?

Host Bridget van Dorsten is joined by Shannon Miller, CEO of Mainspring Energy, and Will Hazelip of National Grid Ventures, to dig into a technology most listeners haven't heard of and the first commercial hydrogen-powered deployment of it. Mainspring's 250-kilowatt linear generator is being installed at National Grid's 1,500 MW North Port facility on Long Island, in partnership with NYSERDA, the Long Island Power Authority, and Stony Brook University.

Shannon explains how Mainspring redesigned the generator using the power electronics that drive solar inverters, batteries and EVs, replacing mechanical systems with software, eliminating the flame, and operating at temperatures low enough to take NOx out of the equation. An adaptive pressure cycle, software-controlled in real time, runs the same hardware on hydrogen, compressed natural gas, biogas, propane or blends, with no hardware change. The 250 kW form factor matters too: efficiency holds across the full load range, fleet redundancy replaces single-asset reliability risk, and deployment is a concrete pad plus electrical and fuel hookups rather than a multi-year build.

Will frames the project against the regulatory backdrop. Long Island sits in a non-attainment zone for NOx, and New York's path to a carbon-free grid requires what the state calls a dispatchable emissions-free resource. The unit will run for 12 months on green hydrogen and on compressed natural gas, with Stony Brook measuring emissions and efficiency, NYSERDA watching for regulatory design, and National Grid building operational experience for the rest of its ageing fleet.

The economic case rests on the alternative. New-build hydrogen-capable gas turbines run $3,500–$4,000/kW on capex (per Wood Mackenzie), with delivered power costs reaching $300–$900/MWh once hydrogen is layered in. Shannon's point is that committing to a single-fuel turbine only pays off if the fuel actually arrives at the scale and price you assumed. With hydrogen supply uncertain, that's a stranded-asset risk linear generators avoid by running on whatever fuel is available today. Will adds the carbon-market angle saying that as carbon pricing develops, real-time fuel switching becomes an optimisation lever, not just a hedge.

Then there’s the supply reality. Total US hydrogen production today isn't enough to fuel a single 500 MW power plant, and with 45V tax credit requirements tightening and federal climate policy in flux, the gap between hydrogen ambition and supply isn't closing fast. Will's suggests starting with the fuels that exist today and scale into hydrogen as supply grows.

The episode closes on demand. Mainspring's factory produces 325 MW a year today and can roughly double in 12–15 months, with pull from industrial customers, data centres and AI infrastructure, and utilities at once, driven by the same problem: nobody can get power fast enough.

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