• MN8's West Virginia portfolio combines 86MW of solar with 70MW/280MWh of lithium-ion storage and a 10MW/100MWh Eos zinc battery
  • Solar is due in 2028, followed by the two storage systems in 2029 and 2030, so the full portfolio will take several years to come online

The fact

MN8 Energy, Google, and Eos Energy Enterprises announced plans on 2 September for a solar and battery-storage portfolio in Kanawha County, West Virginia. MN8 will own and operate the projects, known collectively as Mammoth Solar, while Google will buy their energy, capacity and clean-energy attributes.

The portfolio includes an 86MW solar project, a 70MW/280MWh lithium-ion battery and a 10MW/100MWh Eos Z3 zinc battery designed for 10-hour discharge. MN8 expects the solar project to begin commercial operation in 2028, followed by the lithium-ion system in 2029 and the Eos system in 2030.

The projects will connect to the PJM grid, which also serves Google's data-centre operations in the region. They are not a dedicated power plant connected directly to a Google campus, and the three assets will not enter service at the same time.

The assessment

MN8 is not bringing all of this capacity online as one power project. The solar plant is due first. A four-hour lithium-ion battery follows a year later, with the 10-hour Eos battery planned for 2030. What the portfolio can do will therefore change as each asset enters service.

In 2028, the project is expected to add solar generation but no new storage from this portfolio. The lithium-ion battery should add 70MW of storage capacity in 2029, while the smaller Eos system extends the available storage duration when it arrives a year later. Neither battery creates additional electricity; their role is to move energy between different periods.

For BTW readers, the three commissioning dates are more useful than adding the headline MW figures together. Google's West Virginia load may grow on a different timetable, and the projects feed the wider PJM grid rather than one data centre. The important question is whether the generation and storage assets arrive as that demand develops.

What to watch

The first milestone is commercial operation of the 86MW solar project in 2028, followed by the lithium-ion battery in 2029 and the Eos system in 2030. Construction and interconnection progress will show whether those dates hold. Once the batteries are operating, dispatch data should show when each system charges and discharges and how the different storage durations are actually used.