Eversource is proposing a 14.7-MW battery energy storage project on Martha’s Vineyard, Mass., that is designed to reduce the use of diesel generators on the island, provide voltage support, and defer construction of additional undersea cables to the island.
“This battery storage system will help Martha’s Vineyard meet its energy goals and reduce its carbon footprint,” Penni Conner, the utility’s senior vice president and chief customer officer, said in a statement.
The plan calls for the storage installation to be constructed in two phases. The first, 4.9-MW/20-MWh phase is scheduled to begin in the late winter or early spring of 2020 and be completed by the end of that year at a cost of about $15 million. The second, 9.8-MW/64-MWh phase is expected to begin in the spring or summer of 2022 and to be completed by the summer of 2023 at an estimated cost of $28 million.
The batteries will be housed in a 6,000 square foot Cape Cod-style building on existing Eversource property in the town of Oak Bluffs.
Eversource has filed a petition with the Massachusetts Department of Public Utilities (DPU) seeking an exemption from the Town of Oak Bluffs zoning bylaws, which do not allow for public utility uses. In addition to exemptions for individual portions of the project, Eversource is also seeking a comprehensive exemption from the DPU as a means of “serving to prevent delay in the construction and operation of the proposed use.”
Energy storage project in public interest
Eversource is asking the DPU to reach a decision on the zoning exemption within nine months of its Nov. 30, 2018, filing in order to keep the project on schedule.
In a separate petition, the DPU had earlier reviewed Eversource’s plans and pre-authorized rate recovery for the first phase of the Martha’s Vineyard energy storage project.
In that decision, the DPU found the storage project would be in the public interest because it could lead to the potential retirement of a portion of the diesel generators on the island that serve as a source of peaking and backup power. The storage project could also provide reliability by improving voltage regulation, reduce peak load, and defer upgrades to additional undersea cables. Martha’s Vineyard’s primary source electrical power comes through four 23-kV subsea cables that connect the island to the mainland. The island is also is served by five 2.5 MW diesel generators owned and operated by NRG Canal, although Eversource is responsible for their maintenance.
In recent history, the diesel generators have been used for as much as 6,212 hours in 2013, when one of the subsea cables failed, and as little as 71 hours in 2015. The diesel generators are also sometimes run to lower the usage of cables, a practice Eversource has adopted to help avoid the potential of cable failure if they are used at too high a capacity.
Positions Martha’s Vineyard for more renewables
Martha’s Vineyard also has 3.2 MW of large-scale solar power installations that are owned by independent generators. But further solar installations are limited, Eversource says, because they would run up against the limits of the unique characteristics of the island’s electrical infrastructure, which already is prone to “voltage flicker” related to the existing solar installations.
By being able to compensate for voltage fluctuations, Eversource says the proposed battery storage system would better position it to integrate additional distributed energy resources on the island.
The Martha’s Vineyard energy storage project is one of two approved in eastern Massachusetts by the DPU. The second is Eversource’s project in Provincetown at the tip of Cape Cod. Known as the Outer Cape Energy Storage Project, it is a 25-MW/38-MWh-battery installation designed to provide backup generation in the event of an outage on the local grid for customers in four towns: Provincetown, North Truro, Truro and Wellfleet. The project will defer construction of 13 miles of distribution line through the Cape Cod National Seashore and is expected to improve reliability in the served towns by over 50 percent.
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