Solmar Insights
Google has signed an agreement to offtake energy, capacity, and clean energy attributes from the Mammoth Solar project in West Virginia, aiming to match its regional data center demand with firmed renewable supply. Developed by MN8 and leveraging zinc-based long-duration battery systems from Eos Energy Enterprises, Mammoth Solar transforms a former coal mine into a site for 86 MW of solar generation, supplemented with both 70 MW/280 MWh lithium-ion and 10 MW/100 MWh zinc-based storage, among the largest zinc deployments to date in the United States.
Key figures
86 MW solar PV project
70 MW/280 MWh lithium-ion storage
10 MW/100 MWh Eos zinc storage
Expected solar commercial operation in 2028
Google’s regional load matching
The offtake agreement aims to directly serve Google’s growing data center operations in the PJM region, where hyperscale demand continues to stress grid reliability and capacity pricing. By contracting for both solar production and long-duration storage, Google will be better able to align clean energy output with round-the-clock consumption profiles typical of data center workloads, addressing regional grid volatility and emission concerns.
With this move, Google and MN8 are responding to a PJM market where capacity auction price ceilings have been triggered and a recent backstop auction was required to meet a nearly 7 GW reserve shortfall. Reliable, dispatchable clean capacity is increasingly valuable to ensure both the company’s carbon commitments and the physical resilience of hyperscale compute facilities.
Storage technology mix and scale
Mammoth Solar stands out for its hybrid storage configuration: the 10 MW/100 MWh Eos zinc battery system is one of the country’s largest non-lithium long-duration deployments, offering up to 10 hours of discharge per cycle. Most such zinc projects in the US have previously been sized below 1 MW, according to DOE data. The longer discharge profile enables load support well beyond the 4-hour typical window for lithium-ion batteries, a key differentiator for power-intensive operations such as data centers.
The additional 70 MW/280 MWh of lithium-ion storage offers flexible energy shifting and standard short-duration ancillary services. By layering the two chemistries, MN8 and Eos seek to balance cost, safety, and operational resilience, while hedging against the lithium supply chain volatility that has characterized recent years in battery procurement for grid-scale projects.
Former coal mine transformation
The project’s siting on a reclaimed West Virginia coal mine exemplifies a trend of repurposing legacy energy sites for new generation and storage assets. Repurposing brownfield locations can expedite permitting, leverage existing grid interconnection infrastructure, and support community transition from coal-dependent economies to renewable-driven development.
This sites’ integration into the PJM Interconnection allows participation in wholesale capacity and energy markets, directly contributing to regional reliability as traditional generation units retire. The choice of West Virginia further reflects increasing hyperscale developer interest in Appalachian grid nodes and transmission corridors, ensuring proximity to both fiber routes and available power interconnection points.
Timeline and project partners
According to statements from Google, MN8, and Eos Energy Enterprises, the solar portion is scheduled for commercial operation in 2028, with the two battery systems following in 2029 and 2030. This staging allows the developer to phase interconnection and commissioning work while observing market developments and regulatory review, especially as PJM capacity mechanisms and FERC proposals evolve in response to reliability concerns.
Last year, MN8 and Eos entered into a supply agreement for up to 750 MWh of zinc-based battery modules to be delivered to various projects across PJM and other US markets. The Mammoth project is among the first to realize this strategy, underlining growing institutional interest in diversified storage portfolios for grid and data center integration.
Market significance for hyperscale buyers
The scale and chemistry diversity of storage at Mammoth Solar highlight changing procurement standards among leading hyperscalers. Direct procurement of hybrid clean energy assets is not only carbon-accounting motivated but increasingly essential for cost control in regions with tight capacity margins and volatile reserve pricing. Projects like this set precedents for integrating advanced long-duration storage into grid-interactive designs for mission-critical digital infrastructure.
Successful deployment at this scale could accelerate adoption of alternative battery chemistries and influence merchant storage project underwriting. It may also shape how developers approach interconnection studies for brownfield sites in states transitioning away from coal, broadening the pipeline of available data center-ready projects in the Mid-Atlantic.
What this means for buyers
Data center capacity and grid-interactive storage in the PJM Interconnection are directly affected by this agreement. The Mammoth Solar project’s combination of 86 MW solar, 70 MW/280 MWh lithium-ion, and 10 MW/100 MWh zinc-based storage is now committed to commercial operations from 2028 through 2030, setting a timeline for market entrants. Buyers planning power procurement or project development in PJM this quarter must factor in growing competition for late-decade interconnection and long-duration, hybrid storage assets with firm contracts from major hyperscalers.
Reporting via the original publisher
