Vermont Solar-storage Projects Aim to Lower Costs During Peak Demand

Green Mountain Power is developing three projects to add 14.4 MW of solar and 6 MW of storage to its system.

by Bill Opalka

A Vermont utility is adding solar panels and battery storage in hopes of lowering costs and improving reliability on hot summer days when electricity demand — and prices — tend to spike.

State regulators approved the first of three projects by Green Mountain Power on Jan. 16, when they granted a certificate of public good for a project in Essex that combines a 4.5-megawatt solar array with a 2-megawatt battery.

The Essex project, first proposed in August, is located on about 25 acres of a former sand pit. GMP has similar projects planned in Milton and Ferrisburgh. Together, the proposed nameplate capacity would provide 6 megawatts of battery storage, including 24 megawatt-hours of energy over a four-hour period, along with about 14.4 megawatts of solar energy.

Construction on all three projects is expected to start in the spring and take about four months, though a start date has not been announced. The goal is to have them available to provide system benefits during the summer.

GMP and solar company Green Lantern Development are building the project. In filings related to GMP’s most recent rate case, the company said the three joint-venture solar-battery storage projects are intended to drive down grid costs. The commission approved the overall rate case on Dec. 24, 2018. The Milton and Ferrisburgh projects were first proposed in December 2017.

The utility said there are multiple benefits. Energy storage and discharge during targeted peak load can save customers money on transmission and capacity. Other benefits include frequency regulation services to earn revenue for customers when the batteries are not dispatching energy to the grid, providing opportunities for energy arbitrage in times of high prices, and possible “islanding” capability.

The battery storage system, combined with other generation and storage resources in the area, would allow GMP to island a subset of Essex customers from the interconnected power grid during emergency and planned outages.

“Serious climatic events and changing weather patterns make improvements to system reliability and resiliency for customers even more important,” the company wrote.

Microgrid storage projects were highlighted as a component of GMP’s strategy to incorporate intermittent renewable energy sources in the company’s 2014 Integrated Resource Plan.

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