Mainspring’s linear generator may speed the transition to a zero-carbon electrical grid. //

The linear generator can quickly switch between different types of green (and not-so-green, if need be) fuel, including biogas, ammonia, and hydrogen. It has the potential to make the decarbonized power system available, reliable, and resilient against the vagaries of weather and of fuel supplies. And it’s not a fantasy; it’s been developed, tested, and deployed commercially. //

It is currently installed at tens of sites, producing 230 to 460 kilowatts at each. We expect linear generators at many more locations to come on line within the next year. //

So rather than mimicking an engine, we designed a new machine that ties the compression and expansion motion directly to the generation of electricity, and in doing so provides the necessary reaction control. This machine ended up looking completely different from—and having almost no parts in common with—a conventional engine. So we felt a new name was needed, and we called it the linear generator.

How the linear generator works
Picture a series of five cylindrical assemblies arranged in a line, held within a boxlike frame. The central tube is the reaction chamber; it’s where the fuel and air go. On either side of it sits a linear electromagnetic machine (LEM) that converts the push from pressure directly into electric power. At each end of the generator is an air-filled cylindrical chamber that acts as a spring to bounce the moving part of the LEM back to the center. The whole arrangement—two air springs, two LEMS, and a reaction chamber—forms a linear generator core. It’s long and skinny: A machine rated at 115 kW is about 5.5 meters long and about 1 meter high and wide.

The LEM, in principle, is an electric motor that has been unrolled to form a line instead of a circle. It consists of a moving part—the translator—and a stationary part—the stator. //

One real-world example of the system working this way pairs our generators with a 3.3-megawatt rooftop solar array. When the sun is shining, our generators turn off, and when the sun goes down or goes behind a cloud, our generators automatically turn on within seconds, immediately providing precisely as much power as the building requires.