Google, MN8 Energy and Eos Energy Enterprises are developing a 350 million dollar solar and storage facility in West Virginia to power Google's regional data centers, with operations beginning in 2028.
The Mammoth Solar project will combine 86 MW of utility-scale solar, 70 MW and 280 MWh of lithium-ion battery storage, and 10 MW and 100 MWh of Eos Z3 zinc-based long-duration storage on a reclaimed coal mine in Kanawha County. Google has committed to purchase the project's energy, capacity and renewable-energy credits. The facility represents the state's first commercial-scale long-duration energy storage deployment and Google's first deployment of Eos' zinc technology.
The three-phase buildout runs through 2030. Solar operations begin in 2028, lithium-ion storage in 2029, and the zinc long-duration storage in 2030. The Eos Z3 system, which stores energy in zinc-bromine chemistry, is designed for discharge durations of 6 to 10 hours, a gap that traditional lithium-ion batteries do not address. Eos manufactures the Z3 at a facility in Wilsonville, Oregon.
Google has announced over 25 gigawatts of renewable energy purchasing commitments globally since 2010. The company pledged in 2020 to run on carbon-free electricity 24 hours a day, every day, by 2030. Long-duration storage systems like the Eos Z3 are central to that target because they can smooth intermittency across hours when solar and wind generation dips.
MN8 Energy, a renewable energy developer, is leading project development. Eos Energy is a public company listed on Nasdaq under the ticker EOSE. In August 2026, Eos announced a 100 million dollar strategic investment from Breakthrough Energy Ventures, the climate technology fund co-founded by Bill Gates. The company has completed deployments in California, Oregon, and Arizona and has projects in advanced stages across the Midwest and Southeast.
The 350 million dollar investment and multi-year timeline place the Mammoth Solar project among the largest hybrid solar-storage facilities Google has committed to in the United States. The project sits in a region where coal mines have closed at accelerating pace; the facility's location on reclaimed mine land aligns with both West Virginia economic development policy and Google's stated preference for brownfield sites.
The zinc-iron chemistry of the Z3 system operates at lower temperatures and with fewer thermal management constraints than lithium-ion, reducing operational complexity over multi-decade lifecycles. Eos' previous deployments have focused on demonstration and pilot-scale projects; Mammoth Solar marks the first utility-scale rollout of the Z3 as a major component of a production-stage grid asset. If zinc-iron systems prove reliable at scale, the technology could reshape the cost and duration curve of energy storage available to large data-center operators, where Google and other cloud providers face mounting pressure to decarbonize power consumption while maintaining dispatchable capacity.
