Mainspring’s 1.6 GW AEP Deal: How Linear Generators Are Reaching Gigawatt Scale
On October 13th, AEP announced a contract to purchase up to 1,600 MW of Mainspring Linear Generators through 2034, with a first tranche of 190 MW to be delivered starting in 2027.
Mainspring claims its linear generator technology delivers a “unique combination of high reliability, dispatchability, efficiency, and low emissions. It’s also rapidly deployable, compared with gas turbines that may take 5 years to acquire.
A linear generator looks – as Bloomberg once described it- like a horizontal pogo stick. A mixture of air and fuel is delivered to the central reaction chamber, where it is compressed by air springs that use energy stored from the previous cycle.
That compression creates a low-temperature, non-combustible reaction that pushes the magnetic oscillators (pistons) out away from the center in two directions, where they run through the copper coils and create electric current - a process happens 13 times per second.
Without combustion, one gets low nitrous oxide emissions, and quiet operation in a compact, modular system built for local generation.
The machines can be programmed to switch relatively easily between natural gas, RNG, biogas, propane, and hydrogen. They convert the raw energy of natural gas into power at a 46% conversion efficiency rate, less than the 60% typical of a combined cycled gas turbine, but better than the 40% typically resulting from an aeroderivative turbine. With waste heat capture, the California Energy Commission puts the combined heat and power efficiency at over 80 percent.And there’s no NOx (a precursor to ozone). In addition to being quiet, they don’t use any water, and they ran at temps between -30 to 50 C (about -22 to 122 F).
Mainspring’s linear generators have been in the wild for six years, with many financed by NextEra Energy. Customers include grocery giant Kroger, global cold storage leader Lineage Logistics, Fedex, Amazon, and the Defense Department. But this AEP announcement is next level.
They come in standardized 2.5 megawatt configurations bundling 10 x .25 MW generators, plus skid-mounted inverters and transformers that can accommodate various voltage levels.
On October 13 of this year (same date as the AEP announcement), Mainspring also announced a $242 mn Round F funding deal, putting its funding total at over $1 bn.