PEABODY — The proposed 55-megawatt natural gas-fired “peaker plant” will most likely emit more carbon dioxide per hour on average than the existing peaker plants in the city, but according to the Peabody Municipal Light Plant, this doesn’t mean the new plant will be less efficient than the older plants.
“You are not comparing apples to apples. The newer unit is more than double the size of Peabody's Gas Turbine Number One,” said PMLP Manager Charles Orphanos, referencing an older 20-megawatt peaker plant on the same property which PMLP plans to retire.
The new plant, Orphanose said, would be state-of-the-art and utilize a variety of new technologies to ensure it runs as cleanly and efficiently as possible, but it is difficult to compare the new plant with existing units without doing numerous mathematical calculations.
“Because of the size difference in the two units, you would have to break it down on a megawatt hour basis,” he said. “You have to look at the equivalent CO2 emissions on a megawatt hour basis.”
A megawatt hour, Orphanos explained, can be calculated by multiplying the number of megawatts a plant is putting out by the amount of time the plant runs. For example, a plant running at 55 megawatts for one hour would have run for 55 megawatt hours, he said.
Some plants, like Gas Turbine Number One, don’t always put out the same number of megawatts, Orphanos said. When PMLP refers to the 1970s-era Gas Turbine Number One as a 20-megawatt plant, he explained, the organization is referring to the plant’s “winter rating.”
“They don't put out the same power in the summer and the winter, so there are different ratings,” he said, explaining that plants are usually described using the highest number of megawatts which it puts out. “So 20-megawatts (for Gas Turbine Number One) is a winter rating, and in the summer it doesn’t put out as much power, somewhere around 16 megawatts.”
Because the new plant, which is referred to as Project 2015A in public documents, is newer and will include a modern cooling system, it will likely be able to run at 55-megawatts most of the time, Orphanos said. He also noted that it would be best to check this information with Project 2015A’s owner and operator, the Massachusetts Municipal Wholesale Electric Company (MMWEC).
An MMWEC representative said the organization was compiling information about the efficiency of Project 2015A, but the company did not provide this information before press time.
Previously, Orphanos explained that Gas Turbine Number One ran less than 60 hours and emitted approximately 646 tons of carbon dioxide in 2020. The same unit ran less than 70 hours in 2019 and emitted less than 800 tons of carbon dioxide in 2019, he said.
Project 2015, on the other hand, is anticipated to run 239 hours per year and emit approximately 7,085 tons of carbon dioxide, according to MMWEC.
Based on these numbers, Project 2015A would emit somewhere between 29 and 30 tons of carbon dioxide per hour, while the older Gas Turbine Number One would emit between 10 and 11 tons of carbon dioxide per hour.
However, Orphanos said, if the two units were both able to run at 20-megawatts, he assumes Project 2015A would emit less per hour.
“That should be a fair statement based on an apples-to-apples comparison. I would certainly have to do the math, but knowing the new turbine is state-of-the-art, that should be true,” he said, also noting that he is going out on a limb by making this assumption, but “it is a limb [he] feels more comfortable with.”
He said MMWEC would likely be more knowledgable about the truthfulness of this assumption.
Plans to build a new peaker plant, which would only run during periods of especially high demand for electricity, have been in the works since 2015. The plant was previously approved to be built at PMLP’s Waters River substation, behind the Pulaski Street Industrial Park, where Gas Turbine Number One and another 40-megawatt peaker plant already exist.
After pausing the $85 million project for two-months in order to respond to locals’ environmental and health concerns and investigate alternative energy options, MMWEC announced multiple changes to Project 2015A including the elimination of one of two 200,000 gallon oil tanks and the switch from ammonia to urea. PMLP also announced plans to retire Gas Turbine Number One.
Orphanos encouraged anyone with further questions about the PMLP-owned peakers, megawatt hours or plant efficiency to reach out to his office.
"All they gotta do is call," he said. "We're not withholding anything. We want to educate everyone because, if anything, it will help."
Staff writer Erin Nolan can be reached at 978-338-2534, by email at firstname.lastname@example.org or onTwitter at @erin_nolan_.