News

# Linear Generator Technology Aims to Transform Local Power Generation

September 14, 2022 by Mike Falter

## Power generation uses linear generator technology to deliver clean and scalable back-up power across fuel sources.

In recent years, power outages due to strained grids and severe weather events have increased the need for more resilient, localized energy sources that can dynamically supplement primary sources of electricity during periods of high demand or reduced supply. Recently, heat waves throughout much of the U.S. have strained grids, and without backup damaging blackouts or brownouts can occur.

### Reliability Key for Stressed Grids, Renewables Adoption

The adoption of renewables presents its own set of challenges.  To ensure the continuous availability of power, renewable generation like wind and solar need back-up energy sources to supplement electricity supply during periods of low wind or solar output.

With its innovative linear generation platform, Mainspring offers a dispatchable power generation solution that addresses the need for commercial, industrial, microgrid, and utility customers–all with near-zero emissions.

### Clean Back-up Power Generation

Based in Menlo Park, CA, Mainspring Energy was founded in 2010 by three Stanford engineers looking to develop a new power generation solution for clean, reliable, and cost-competitive electricity. The result is the Mainspring Linear Generator which uses linear generation technology to offer a highly dispatchable and clean power solution.

Dispatchability is the ability to vary power and turn it on and off quickly as demand changes. This is critical for secondary power operations, whether backing up main grid power or supplementing renewable sources like wind and solar.

The Mainspring generator achieves a high level of dispatchability by automatically and quickly adjusting its fuel input rate to match power output with demand.

##### Power demand matching with renewables. Image used courtesy of Mainspring

Customers need dispatchable energy, but they also want net-zero emissions. The Mainspring solution delivers through a low-temperature chemical reaction that does not require a flame and has near zero emissions.

Compared to traditional combustion generators, its design directly converts linear motion to electricity without mechanical losses. Low capital and maintenance costs are achieved through simplicity of design and the use of standard materials which do not require fuel cell catalysts, engine oil, spark plugs, or the complexities of rotating parts. The Mainspring Linear Generator actually uses only two moving parts and no oil.

In July, the company announced a pilot project with American Electric Power (AEP) to deploy the linear generator for grid applications in Oklahoma. Use cases include scaling localized generation in high load pockets to delay or prevent grid upgrades and accelerated infrastructure electrification for EV charging stations and similar applications.

### Benefits of Linear Generator Technology

Working more like a piston in a car, the linear generator uses linear motion, as opposed to rotational, to induce electrical currents between the generator magnets and copper coils.

Due to its unique design and advanced controls, the linear generator can operate at a much lower reaction temperature than traditional combustion-based generators. Precise control of the oscillators within the generator compresses a fuel air mixture until the mixture reacts uniformly without a flame. The energy from this low-temperature reaction drives the linear motion of the oscillators which is directly converted into electricity with near zero NOx emissions.

In this manner, the Mainspring linear generator combines the high efficiency and low emissions of fuel cells with the affordability and dispatchability of traditional combustion engines and micro-turbines.

The Mainspring technology also has the ability to dynamically switch between fuel types and qualities, including renewables, since it continuously adjusts compression and expansion from cycle to cycle. Compatible renewable fuels include biogas, green ammonia, and green hydrogen.

##### Linear Generator. Image used courtesy of Mainspring Energy

The base package generator unit includes 2 internal linear generators that operate in tandem and can supply 230 kW of three-phase AC power at 480 V. Modular scalability up to 15 MW per acre is achievable for grid-scale array applications.

 Performance Specifications Outputs1 Power (net AC) Electrical 230 kW 480 V, 3 Phase, 60 Hz Inputs2 Fuels Input Pressure Water Consumption Natural Gas or Biogas with Hydrogen blend up to 30% 8-25 psig (15 psig normal) None Efficiency3 Electrical (LHC, net AC) Heat Rate (HHV, net AC) 45% 8,416 BTU/kWh Emissions4 NOx Noise < 2.5 ppm (<0.07 lb/MWh) < 70 dBA @ 6 feet Physical Weight Dimensions (L x W x H) 20 tons 20.5' x 8.5' x 9.5'

### Recent Funding

Just this past May, Mainspring announced the close of its Series E funding round, raising $150 million from global private equity investor Lightrock with participation from other notable investors, such as Khosla Ventures, Chevron Technology Ventures, and Bill Gates. The funding comes on the heels of its$95 million Series D earlier in the same month and the announcement of plans to deploy up to 150 Mainspring Linear Generators for Lineage Logistics, the world's largest temperature-controlled industrial REIT and logistics solutions provider.