The crippling Arctic blast into Texas in February and blistering California heat wave in August 2020 exposed climate vulnerabilities of the conventional electric grid and created opportunities for battery storage, microgrids and other distributed energy resources.

Mainspring Energy Inc. — an onsite power upstart backed by billionaire Bill Gates, Khosla Ventures, utility American Electric Power Co. Inc., Norwegian energy giant Equinor ASA and other investors — on March 9 launched its fuel-flexible "linear generator" to offer businesses another distributed energy option to provide much-needed power during outages and an alternative when the grid is up and running.

The Menlo Park, Calif.-based company also announced an initial customer: NextEra Energy Resources LLC, the competitive generation arm of NextEra Energy Inc., which signed a $150 million agreement to purchase generators and help to finance their initial commercial deployments.

"What we do is really provide the multiday outage support ... where you need that additional resiliency," Shannon Miller, Mainspring Energy's CEO and co-founder, said in an interview.

Born out of a thermodynamics laboratory at Stanford University in 2010, Mainspring's generators can run on natural gas, propane, biogas or hydrogen, and are designed to ramp up and down to fill in gaps in power supplies, either in standalone configuration or in microgrids with renewable energy and battery storage, she said.

"Having those key features while being low cost is something that really just doesn't exist today," Miller said.

"Many commercial and industrial customers as well as utilities want clean, reliable power generation, with the capability to switch to 100% renewable fuels like biogas and hydrogen as they become available," NextEra Energy Resources President and CEO John Ketchum added in a statement.

Rollout to begin mid-2021

While not disclosing its customers or installation locations, NextEra said in an email that it expects to deploy the technology for "behind-the-meter customer locations and grid-side applications."

According to Mainspring, shipments to multiple unnamed "Fortune 500 customers" will begin in mid-2021. One customer is a "national supermarket chain" that previously piloted the generator and signed an agreement to install the technology at up to 30 grocery stores, it said.

The company refers to its linear generator, initially packaged in 250-kW blocks, as "a fundamentally new power generation technology" that converts motion across a straight line into power using chemical or thermal energy. The design enables high efficiency and near zero nitrogen-oxide emissions, according to Mainspring, as well as low- to zero-carbon-dioxide emissions when running on renewable biogas or green hydrogen.

Miller views the generators as an alternative to diesel generator sets at data centers and in California's effort to maintain electricity service during wildfire season, when Pacific Gas and Electric Co., or PG&E, and other utilities intentionally cut power to prevent transmission lines from igniting fires during hot, dry and windy weather.

"PG&E's been looking at a lot of diesel generator systems as backups, and we think renewable microgrids are a really compelling alternative to that and something we should focus on as a state," the CEO said.

After raising roughly $130 million in venture and strategic capital so far, Mainspring plans to seek another round of investment in the near future, she added. The company, which employs more than 150 full-time employees in Menlo Park, plans to expand its headcount by 40% in 2021.