Jul. 16—Kern County oil fields look more and more like a viable place for storing renewable energy to help balance the state power grid.

Bakersfield startup Renewell Energy is working on its first commercial system using renewably powered winches to lift weights from near the bottom of oil wells. Later, after the sun goes down and wind stops, lowering the weights will run a generator that feeds the grid.

It's at least the second technology proposed for repurposing local oil fields to cover gaps in the availability of solar and wind power. Another Bakersfield company, Premier Resource Management LLC, hopes to turn depleted oil reservoirs into synthetic geothermal storage.

Renewell's simple gravity power system, as a much lower-price alternative to lithium batteries, offers a unique mix of benefits and drawbacks. It may be scaled up in series to discharge energy for long durations, for example, but it doesn't fully kick in for half a second to one second, leaving batteries a certain edge.

The technology might benefit Kern County by improving the economics of plugging idle or abandoned wells while generating rental income for their owners and preserving some of the property's taxable value to local government.

Director Lorelei Oviatt of the county's Planning and Natural Resources Department called the company's system a natural fit for Kern's energy future with large-scale solar generation planned for the Central Valley.

She added in an email that Renewell's product typifies the energy technologies being drawn to Kern, and that it parallels local industry aims.

"Oil companies are continually looking at how to use either existing, physical assets (or) employees' expertise to support the changing economy in California," Oviatt wrote.

Energy storage becomes more important as California races to carbon neutrality by 2045. The Newsom administration announced last week the state's large-scale battery storage capacity has grown 20-fold in the last four years to top 5,000 megawatts and now can power about 4 million homes for up to four hours before needing to be recharged.

Meanwhile, state policymakers are asking for diverse energy storage sources beyond batteries, and there's a particular need for systems like Renewell's that can return more than four hours of power.

CEO Kemp Gregory, a Texas native and now Bakersfield resident, co-founded the company in 2020 with Chief Technology Officer Stefan Streckfus, a fellow Stanford University graduate school alum. They estimate their system, at scale, would deliver energy storage at $5 per kilowatt-hour — 1% what battery storage costs now, or about 3% what it's expected to cost by 2030.