Repurposing the Rust Belt
Renewell’s Plan to Turn Idle Oil Wells Into Gravity Batteries
Deep beneath the scorched earth of North America’s oil patches lie over 2 million idle wells, remnants of a century of fossil fuel extraction. While regulators view them as environmental liabilities, Kemp Gregory, CEO of Renewell Energy, sees them as the missing link in the global transition to renewable energy.
As wind and solar power expand, the electrical grid faces a critical “round-trip efficiency” challenge: how to store energy when the sun isn’t shining and release it when demand peaks.
Renewell’s solution is deceptively simple, relying on basic Newtonian physics rather than complex chemistry. The company converts abandoned wellbores into mechanical energy storage systems, effectively turning a “liability” into a “gravity battery”.
The Mechanics of Gravity
The process involves suspending a massive weight - currently 30,000 pounds, or approximately 15 tonnes - within the existing wellbore.
“We move a weight up and down inside the wellbore,” Gregory explained in the NatureBacked podcast episode. “That weight has a lot of potential energy when it’s at the top... as the weight is moving down the well, the winch spins backwards ... and we’re pushing electrons to the grid.” When electricity is cheap, or there is a surplus on the grid, the system draws power to winch the weight back to the surface, storing that energy for later use.
Unlike lithium-ion batteries, which degrade over time and suffer from “self-discharge,” Renewell’s mechanical system can hold energy indefinitely. “When the weight comes to the top of the well, we put a big mechanical brake on there, and it just sits there,” said Gregory. “It’s not going to lose any energy like a chemical system would.”
Solving a $450 Billion Problem
The economic driver behind Renewell isn’t just energy storage - it’s the mounting cost of “plugging and abandoning” (P&A) old wells. North America currently has approximately 2.15 million idle wells. Federal and state regulations require these to be decommissioned, a process that usually involves filling them with cement and cutting off the wellhead.
“Every single oil well in North America and beyond is a liability.”
Gregory estimates the cost to clean up every well in the U.S. at roughly $450 billion. By enabling oil companies to convert these wells into revenue-generating assets, Renewell creates a “win-win” solution for operators and regulators.
In California, Colorado, and New Mexico, regulators have already recognized this conversion as a valid method for meeting mandatory well-elimination quotas.
Scaling the “Orphan Well Apocalypse”
The scale of the opportunity is vast. Gregory points to Andrews, Texas, as an example, where satellite views show white dots - well pads - as far as the eye can see. Renewell estimates that about 10% of the idle well population, or roughly 200,000 wells, are suitable for their first-generation conversion product.
While the technology is currently being tested at a single site in California, the company’s vision is to coordinate hundreds of wells into a single, massive battery for the grid.
“If the grid says, ‘I need one hour of duration,’ and we’ve got ten wells, then we lower all the weights perfectly simultaneously,” Gregory said. If the grid needs ten hours, they lower them sequentially.
A Business Model Innovation
The ultimate goal is to bring the cost of energy storage down from the current lithium-ion standard of roughly $300 per kilowatt-hour to just $5 per kilowatt-hour.
“We didn’t figure out how to make steel for cents on the dollar,” Gregory admitted. “We created a world in which the oil and gas companies pay us to do this conversion, and then we use that money to more or less build... our CAPEX.”
By leveraging the infrastructure of the “old economy” to solve the storage problems of the “new economy,” Renewell is betting that the path to a sustainable future is paved with the repurposed pipes of the past.