HG&E’s Energy Storage System’s (ESS) are used to enhance HG&E’s electricity system and help keep electric rates stable by reducing rising capacity charges for the utility and its customers. The ESS are charged during low demand periods, when energy costs are low. This stored power is called upon during local and regional peak load periods to cost-effectively lower demand. Demand charges are incurred for electricity and capacity taken from the power grid and used during peak demand periods.
These projects help HG&E’s ongoing efforts to minimize environmental impacts by hosting clean energy production locally. HG&E currently has two commercially operational, utility-scale BESS within our service territory with two more projects under contract.
The two commercially operational projects include the following:
Mt. Tom Energy Storage System (ESS)
Owned and operated by ENGIE North America (ENGIE), the Mt. Tom ESS is a 3 MW/6 MWh utility-scale lithium-ion battery and the second such system to be installed in the state, which went commercial in 2018. The battery draws power directly from the Mt. Tom Solar system, which is the largest community solar project in Massachusetts, and is stored for use during peak demand periods. The system is located adjacent to the former Mt. Tom Coal Plant along the Connecticut River, which ceased operation in 2014. HG&E currently has a 20-year power purchase agreement (PPA) with ENGIE.
Martin J. Dunn Energy Center
Owned and operated by Citizens Energy, the Martin J. Dunn Energy Center is a 4.99 MW/ 10 MWh utility-scale battery located across from HG&E’s North Canal Substation along the Connecticut River. The lithium-ion battery system consists of three 53-foot containers, 158 racks and 1,896 module batteries. Similar to the Mt. Tom ESS, the project will provide an alternative source of energy for HG&E customers when the demand and cost of power peaks throughout the day. At times when the price of energy and electric grid is stable locally, the BESS will participate in the ISO New England (ISO-NE) market to regulate power on the regional grid. The Martin J. Dunn Energy Center is Citizens Energy’s first completed ESS. HG&E currently has a 15-year PPA with Citizens Energy.