Exelon Generation to double capacity of 117MW Massachusetts plant

Exelon Generation has come up with a proposal to more than double the capacity of its 45-year-old power plant in Medway, Massachusetts.

The new units would run primarily on natural gas, with the ability to also use ultra-low-sulfur diesel fuel when natural gas is in low supply or priced too high. In its permit requests, Exelon says it would use diesel up to 30 days a year, but promises not to do so from May 1 to Sept. 30, which is considered to be ozone season. The town opposes any use of diesel, but if the state permits it, the town hopes to negotiate an agreement with Exelon to have the company pay the town a penalty fee when it uses the fuel.

The existing 117-MW plant was built in 1970 and acquired by Exelon from Boston Edison in 2002. Exelon says the new units are needed to help the region meet its power needs. Like the existing plant, which runs around 80 hours a year, they would be used only during peak demand periods.

About half of the daily average of 95,000 gallons of water needed for the plant’s operation would come from on-site wells. Exelon is negotiating with the neighboring town of Millis to purchase the remaining water.

The Conservation Law Foundation has intervened in the process primarily due to concerns about whether the new facility, which would annually discharge 721,000 tons of carbon emissions, is in keeping with a 2008 state law that requires the Commonwealth to drastically reduce greenhouse-gas emissions by 2050, according to David Ismay, a staff attorney for the foundation. The Massachusetts Energy Facilities Siting Board is scheduled to begin hearings on the proposal in December.