Exelon Set to Expand Massachusetts Peaking Plant

Exelon could begin construction as soon as next week on an expansion of its 135-MW West Medway oil-fired peaking plant in West Medway, Massachusetts. The company’s plan to add two units and 200 MW of generation to the existing three-unit facility was deliberated for 29 months by state and local officials before a state board approved the expansion August 4.

The expansion includes the installation of two GE LMS100 dual-fuel turbines, operating primarily on natural gas but also using ultra-low-sulfur diesel as backup for a maximum 30 days a year. The company’s website says the new units could start up and be online in about 10 minutes. Exelon in its reports on the project says the gas-fired generation will reduce CO2 emissions by 40% when it displaces generation from the three older units.

The construction, which will include two 160-foot emission stacks, along with a 50-foot sound barrier to minimize noise, reportedly is expected to take 14 months to complete. Exelon did not immediately respond to a request for comment from POWER about the construction timeframe.

A payment in lieu of taxation (PILOT) agreement between the town of Medway and Exelon values the expansion at $210 million, and per the agreement Exelon will pay the town a total of $75 million over the next 20 years.

Reports said construction will get underway between August 15 and September 30. The state’s Energy Facilities Siting Board (EFSB) tentatively approved the project in December 2016, but the Conservation Law Foundation filed an appeal of that decision, prompting changes to the plan to appease local opposition.

Water from two onsite wells will be used to cool the turbines, and Exelon originally proposed also using water from the nearby town of Millis via an interconnection with Medway’s water system. The original approval said the plant could operate at 60% capacity, with average water demand of 95,000 gallons a day. The plan was then changed to reduce operating capacity to 43%, and water demand to 68,800 gallons per day.

Boston Edison originally operated the Medway plant, installing the three oil-fueled peaking units after a massive blackout affecting eight states and Ontario in Canada in November 1965 left more than 30 million people without power for as much as 13 hours. The Rolls Royce Avon engines at the plant were the first of 12 such engines installed in the world, according to Exelon, which bought the plant from Boston Edison in 2002.

-Darrell Proctor is a POWER associate editor. (@DarrellProctor1, @POWER magazine)