MN8 Energy will build Mammoth Solar, an 86 MW solar project in Kanawha County, West Virginia, coupled with 70 MW/280 MWh of lithium-ion storage and a 10 MW/100 MWh zinc-based long-duration system supplied by Eos Energy Enterprises, according to ESS News.
Google will take the energy, capacity and clean energy attributes of the project under a long-term agreement, MN8 said.
The Eos Z3 units are designed for 10 hours of discharge duration, per MN8. That sits alongside the four-hour profile implied by the lithium-ion block, giving the site two storage assets with different dispatch windows on one interconnection.
MN8 estimates the development represents up to USD 350 million in capital investment. Construction is expected to create approximately 200 jobs, the company said.
The three components come online in sequence rather than together. MN8 expects the solar array to reach commercial operation in 2028, the lithium-ion storage in 2029 and the Eos long-duration energy storage system in 2030.
The site itself is a reclaimed coal mine. MN8 said the project is the first commercial-scale LDES deployment in West Virginia.
The staggered schedule matters for the zinc component. Eos Z3 chemistry is being deployed at commercial scale in a market where lithium-ion dominates grid battery procurement, and MN8's timeline puts the zinc units into service two years after the solar generation they will store. The 100 MWh of zinc capacity is a fraction of the 280 MWh of lithium-ion on the same site, consistent with a pilot-weighted split between the two chemistries.
Google's role is confined to offtake rather than ownership, covering energy, capacity and attributes in a single long-term contract. That structure ties a technology-company load to a coal-legacy site in Kanawha County, with the buyer contracting for firmed output across both the four-hour and ten-hour storage tranches.