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MN8, Google and Eos launch West Virginia LDES project
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MN8 Energy, Eos Energy Enterprises and Google have announced the Mammoth Solar development in Kanawha County, West Virginia: an integrated clean-energy project that combines 86MW of utility-scale solar with 70MW/280MWh of lithium-ion storage and a 10MW/100MWh zinc-based long-duration energy storage (LDES) system. MN8 will own and operate the facility sited on a reclaimed coal mine; Google will buy the energy, capacity and clean energy attributes. The partners plan staged commercial operations in 2028 (solar), 2029 (lithium-ion storage) and 2030 (LDES). MN8 estimates up to $350m in capital investment, about $4m in property tax revenue during the first 20 years, and roughly 200 construction jobs.
At Google, we’re committed to backing solutions that both serve our data centre capacity needs and accelerate progress toward cleaner, more affordable energy systems.
Lucia Tian, Google advanced energy technologies director
Key takeaways
- Project components: The Mammoth Solar development pairs 86MW of solar with 70MW/280MWh of lithium-ion and a 10MW/100MWh zinc-based LDES system.
- Commercial timetable: Commercial operations are planned for 2028 (solar), 2029 (lithium-ion storage) and 2030 (LDES).
- Ownership and offtake: MN8 Energy will own and operate the site and Google will purchase the project's energy, capacity and clean energy attributes.
- Scale and cost: MN8 estimates up to $350m in capital investment and about $4m in property tax revenue for the first 20 years.
- Local impact: The project is sited on a reclaimed coal mine and is expected to create approximately 200 construction jobs.
Table of contents
- Key takeaways
- How the Mammoth Solar project stacks generation and storage to deliver dispatchable power
- Schedule, contracts and technology choices
- Local economic effects and the site choice on a reclaimed coal mine
- Cases for and against the project meeting its objectives
- What to be careful about
- Frequently asked questions
How the Mammoth Solar project stacks generation and storage to deliver dispatchable power
Mammoth Solar is designed as an integrated system that pairs solar generation with two storage technologies to convert intermittent output into a dispatchable source for the PJM grid. The visible components are 86MW of utility-scale solar alongside 70MW/280MWh of lithium-ion storage for shorter-duration dispatch and a 10MW/100MWh zinc-based LDES unit intended to extend firm capacity across more hours.
By design, the project combines short-duration and long-duration capacity: the lithium-ion asset provides 280MWh of energy and the Eos unit provides 100MWh, which together total about 380MWh of storage energy across the site. The lithium-ion array offers high-power, shorter-duration response, while the Eos Z3 zinc-based system is intended to deliver up to ten hours of continuous discharge when required, extending the hours the site can supply dependable capacity into evening and overnight periods.
Schedule, contracts and technology choices
MN8 has scheduled phased commercial operation: solar in 2028, the lithium-ion battery system in 2029 and the Eos LDES in 2030. MN8 will own and operate the facility, and Google will purchase the energy, capacity and clean energy attributes produced by the site; the company said the project will support Google’s nearby data-centre needs. The project is the first commercial-scale deployment of long-duration energy storage in West Virginia and represents Google’s first use of Eos’s Z3 zinc-based storage system under the MN8–Eos Master Supply Agreement.
Eos positions the Z3 as a long-duration complement to lithium-ion, with its chief commercial officer Nathan Kroeker saying the system “extends the value of clean generation across more hours, strengthens the overall portfolio, and delivers more dependable capacity when it’s needed most.” Google’s Lucia Tian described the collaboration as a way to back technologies that serve data-centre capacity needs while progressing commercialisation of LDES.
Local economic effects and the site choice on a reclaimed coal mine
MN8 estimates the project could involve up to $350m in capital investment and deliver around $4m in property-tax revenue to county authorities and nearby schools over its first two decades, with additional revenues expected in subsequent decades. Construction is projected to create approximately 200 jobs, and MN8 highlights the plan to build on a reclaimed coal‑mine site so that previously disturbed land is reused.
Siting the development on a reclaimed mine shapes both the economic case and the project timeline: it can lower new land-impact concerns but may carry legacy remediation and permitting steps specific to former mining sites. The partners also frame the build as supporting PJM reliability by adding dispatchable capacity where Google operates data centres, tying local economic benefits to regional grid needs.
| Component | Power (MW) | Energy (MWh) | Commercial operations (planned) |
|---|---|---|---|
| Utility-scale solar | 86MW | — | 2028 |
| Lithium-ion storage | 70MW | 280MWh | 2029 |
| Eos zinc-based LDES (Z3) | 10MW | 100MWh | 2030 |
Cases for and against the project meeting its objectives
The case for
- Adds dispatchable hours to the PJM footprint by combining short- and long-duration storage with solar, improving capacity availability during evening and overnight periods.
- Secures a stable offtake in Google, which will purchase energy, capacity and clean energy attributes and so reduces merchant-market exposure at first offtake.
The case against
- Staged delivery across 2028–2030 exposes the project to construction-cost inflation, component supply constraints and shifting market conditions across the multi-year build.
- Concentration of revenue on a single named purchaser creates counterparty concentration risk if contract terms change or Google’s procurement needs evolve.
What to be careful about
- Schedule risk from the phased commercial timetable (2028, 2029, 2030) that could push costs higher or delay revenue.
- Financing and capital-cost risk against MN8’s estimate of up to $350m in investment.
- Permitting, remediation or site-preparation challenges at a reclaimed coal-mine site that could affect timing and costs.
- Operational and commercial risk if the Eos Z3 unit does not scale as expected in its first commercial deployment in West Virginia.
The bottom line
The Mammoth Solar project brings a familiar industry pattern—solar plus lithium-ion—together with a commercial-scale trial of zinc-based long-duration storage. The combination is intended to supply dispatchable capacity into PJM while supporting Google’s data-centre needs, with MN8 estimating up to $350m in investment, roughly $4m in property taxes in the first 20 years and about 200 construction jobs. The near-term tests for the scheme are executional: meeting the 2028–2030 timetable, completing site works on the reclaimed mine and ensuring the Eos Z3 unit performs as a first commercial LDES installation in West Virginia.
What to watch
- Watch for the Mammoth Solar project's solar component to begin commercial operations in 2028.
- Watch for the lithium-ion storage array to enter commercial operation in 2029.
- Watch for the Eos 10MW/100MWh zinc-based LDES unit to enter commercial operation in 2030.
Frequently asked questions
What capacity and storage does the Mammoth Solar project include?
The development pairs 86MW of utility-scale solar with two storage systems: a 70MW/280MWh lithium-ion array and a 10MW/100MWh zinc-based LDES unit.
When will the different components enter service?
MN8 has planned commercial operations in stages: the solar plant in 2028, the lithium-ion storage in 2029 and the Eos LDES in 2030.
Who will own the project and who will buy the power?
MN8 Energy will own and operate the facility, and Google will purchase the project's energy, capacity and clean energy attributes to support its data centres.
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