Energy & Environment

Green Mountain Power to buy power from Great River Hydro

Power lines converge at switching stations for Green Mountain Power and VELCO in Williston. Seen on Tuesday, March 9, 2021. Photo by Glenn Russell/VTDigger

Vermont’s largest electric utility is turning to hydropower to meet company renewable energy targets that would eliminate fossil fuels by 2025 and nuclear energy from its portfolio by 2030.

On March 4, Green Mountain Power agreed to a 30-year contract with Great River Hydro. The Public Utilities Commission is expected to hear testimony on the case in the next few weeks as part of a state approval process. 

Under the agreement, Great River Hydro would provide hydroelectric power to the utility in 2023, starting at 145,000 MWh, enough energy to power nearly 20,000 homes. The supply would increase over time. 

With 13 dams on the Connecticut and Deerfield rivers, Great River Hydro has 589 megawatts of installed capacity — enough electricity to power about 213,000 homes. A subsidiary of Boston-based ArcLight Capital Partners acquired all of TransCanada Hydro Northeast Inc.’s New England hydroelectric power portfolio in 2017 and renamed the assets Great River Hydro. 

Vermont’s definition of renewable energy once excluded hydro that generates more than 200 megawatts. That changed in 2010 with the passage of Act 159, which opened the door to larger purchases of hydroelectric power to meet state renewable requirements. 

Under the statute, utilities were required to purchase 55% renewable energy starting in 2017. That number increases by 4% every three years. 

GMP’s goal is to reach 100% renewable energy by 2030; the state target is 90% by 2050. 

By 2033, Green Mountain Power would buy 625,000 MWh per year from Great River Hydro — enough to power for 86,000 homes. That represents about 15% of GMP’s current energy needs, a “meaningful” portion of the company’s portfolio, said Liz Miller, vice president of sustainable supply and resilient systems at GMP. She worked on the filing that was submitted to the PUC on March 4.

“It provides a really well-priced, clean anchor to our portfolio,” Miller said. About 10% of Green Mountain Power’s energy comes from hydropower sources the company owns. Miller said the fact that the energy is local and reliable also made it attractive to the company.

Green Mountain Power will pay between 4.5 and 4.7 cents/kwh and 4.7 cents/kwh for energy and renewable energy credits, “significantly lower than corresponding prices for current long-term sources,” according to Douglas Smith, the utility’s chief power supply executive.

Those rates are lower than the current 5 cent/kwh GMP pays to Hydro-Québec, a mega hydro operation in Canada. However, Miller said it’s not an “apples to apples” comparison because Hydro-Québec provides energy at different intervals. Great River will provide both “peaking” energy to GMP — energy that enters the grid at high-use times, such as the evening — and “firm” energy that’s provided around the clock. Firm energy can complement intermittent energy from solar and wind.

Other renewables are more expensive: GMP would pay 7.7 cents/kwh for Mayflower Wind, once it’s built, to provide offshore wind power from Cape Cod, according to the filing. Solar projects vary in price based on the size — bigger projects can achieve economies of scale that make them less expensive. For example, a large-scale solar project that’s over 45 megawatts costs 5.5 cents/kwh. Other solar projects cost closer to 9 cents/kwh. 

A growing need for energy

Energy needs are expected to grow over time, especially with the push to electrify sectors such as thermal and transportation that are now the biggest sources of carbon emissions. As other long-term contracts end, a gap will open between how much power Green Mountain Power has procured and how much energy will be needed to meet customer demand.

While no other long-term contracts are in the works, Miller said that gap will largely be filled with local renewables such as wind and solar, in a variety of sizes. Hydro can deliver in the winter and overnight, so Miller said it’s a good complement to other renewables.

Green Mountain Power’s Essex #19 Hydroelectric Project straddles the Winooski River between Essex and Williston. Seen on Tuesday, March 9, 2021. Photo by Glenn Russell/VTDigger

It’s common for utilities to have a gap in their planning process, said Ed McNamara at the Department of Public Service. It allows them flexibility as other renewables come online or new technologies are made available.

Power from Great River Hydro is already being delivered to the regional grid operator, ISO New England, according to Brandon Kibbe, director of business development at Great River Hydro, so powering Green Mountain Power customers won’t be a big hurdle.

Burlington Electric Department also has a contract with Great River, and the Vermont Public Power Supply Authority has had power purchase agreements with the company in the past.

“Those PPAs have been on a shorter duration and smaller volume scale than the GMP agreement,” said Kibbe in a written statement.

“Great River Hydro’s renewable generating resources have been providing New England with a significant source of carbon-free electricity for over 100 years,” Kibbe said.

But some environmentalists say that 20th-century resources won’t go far enough to combat climate change. New renewables need to come online to reduce carbon emissions, according to Steve Crowley, climate and energy chair of the Vermont chapter of the Sierra Club, a national environmental group.

“It doesn’t matter who’s buying it. Trading hands from one utility to another is not really changing the global outlook for climate change in any way,” Crowley said.

Miller, the GMP attorney, said hydro is part of the solution. “Existing renewables are absolutely a part of that, and should be both now and going forward,” she said.

Some hydropower ‘greener’ than others

Different hydro facilities can have vastly different impacts on the environment. And for Crowley and other Vermont environmentalists, Great River Hydro is environmentally preferable to the flooding of large areas undertaken by Hydro-Québec

“For the most part, they aren’t wide, ecosystem-gobbling reservoirs,” Crowley said about Great River Hydro facilities, unlike systems north of the border.

Kathy Urffer, a river steward with the Connecticut River Conservancy, agreed.

“I’m much more pleased that GMP is purchasing from Great River Hydro, which are existing dams, than purchasing from Hydro-Québec, which is still constructing dams and, frankly, severely damaging the Indigenous communities in Canada,” Urffer said.

Still, there are some ecological concerns about dams on the Connecticut and Deerfield rivers. Dams disrupt upstream and downstream passage of fish and other aquatic animals. The fish ladders now in place were built in the late 1970s and early 1980s for Atlantic salmon, according to Urffer. But other species — such as eel, shad and sea lamprey — are affected, too.

With the relicensing process underway for three of Great River Hydro’s facilities, “this is our next opportunity to make significant upgrades and changes to upstream and downstream passages,” Urffer said. The Wilder, Bellows Falls and Vernon dams are currently being relicensed.

Sediment also gathers upstream of a dam, filling the habitat. Meanwhile, downstream of the dam becomes sediment-starved.

At facilities that provide peaking energy — where water is held back and then released at high-demand times of the day — water levels fluctuate by 2 to 3 feet a day. Changes in water level can lead to erosion, causing streambanks to topple. According to Urffer, the dams on the lower Connecticut River have all been operating as peaking hydro facilities for the past 40 years.

Great River Hydro claims that its dams do not cause erosion

Urffer was optimistic that, hydro from Great River could be a good ecological option for energy. She said some work still remains.

“From my perspective as the river advocate, we want to get the best deal for the river,” she said.

Correction: Due to an editing error, an earlier version of this story imprecisely described the location of Green Mountain Power.

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Amanda Gokee

About Amanda

Amanda is a graduate of Harvard University, where she majored in romance language and literature, with a secondary focus on global health. She grew up in Vermont and is working on a master’s degree in liberal studies at Dartmouth with a concentration in creative writing.

Email: [email protected]

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