FirstLight to Retire Kerosene-Fired Turbine, Plans Hydro-Powered Battery Replacement in Preston

The Tunnel Hydro power plant on the Quinebaug River, next to the Tunnel Jet fossil fuel peaking plant that FirstLight Power announced it will shut down with plans to replace it with a battery storage project (FirstLight Power)


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PRESTON – FirstLight Power said it will retire the last fossil fuel-powered plant in its fleet next year – a more than 50-year-old, 17-megawatt, kerosene-fired turbine – and plans to replace it with a battery storage system with the same capacity.

Standing in front of the turbine, tucked behind a farm along the confluence of the Quinebaug and Shetucket rivers, FirstLight CEO Alicia Barton said the visibly aging plant is a symbol of Connecticut’s energy past – and that the company is looking to the future with plans for a 17 MW battery that it would develop with New Leaf Energy

That battery system will tie in to its Tunnel Hydro facility – a 3 MW “run of river” hydropower plant set a few hundred feet up the Quinebaug River – and the extensive Eversource grid infrastructure already built on the site.

“It’s a great showcase of the opportunity to pair batteries with renewable hydropower to supply renewable energy to Connecticut communities when it’s needed the most,” Barton said.

Built in 1969, the aging power plant is driven by a jet engine fueled by kerosene, and is used as a peaking plant – meaning it runs only when it is needed to bolster the power supply of the electric grid. 

The Tunnel Jet, 17 megawatt, fossil fuel-fired power plant was built in 1969, and has run for an average of fewer than 24 hours a year for the last decade. FirstLight Power announced it will shut down the plant next year (CT Examiner)

Barton said the plant is rarely called on, and runs for a few hours a couple times a year. Over the last decade, it’s run for fewer than 24 hours a year on average, she said.

Barton said that a peaker plant like Tunnel Jet can operate economically for a long time in the New England energy markets. The economics of running a battery system like FirstLight is proposing are still “under development,” and partly depend on incentives.

“We’re committed to doing the project, but in order to see the whole fleet of peakers turn over [to battery storage], we do need to see changes in market rules and programs, both at the ISO-New England level, and in the state of Connecticut,” Barton said.

The Connecticut Department of Energy and Environmental Protection has said it intends to open a procurement for battery storage systems in the near future – similar to its procurements for renewables like wind and solar in the past. In 2021, the Connecticut General Assembly directed DEEP to procure 1,000 MW of battery storage projects by 2030. 

Barton said FirstLight plans to participate in that program when it is available. The co-location with the Tunnel Hydro plant could be a boost to FirstLight’s plans, as the Connecticut law specifically pointed out supporting battery projects that pair with existing hydro plants to allow the renewable energy source to provide power to the grid when it’s needed, Barton said.

The Tunnel Hydro 3 megawatt “run of river” hydropower plant on the Quinebaug River in Preston (CT Examiner)

Tunnel Hydro, located just downstream of the Quinebaug River from Taft Tunnel, is a small “run-of-river” hydro plant, meaning it doesn’t store water in a large pond or reservoir before running that water through turbines – rather, it runs turbines from the flow of the river.

“It’s a little bit like solar in that regard. Solar is on when the sun is shining, and [run-of-river] hydro is on when the water is running,”

Many hydropower plants use their reservoirs as a sort of energy storage – allowing water through turbines when they need the power. A battery system would allow Tunnel Hydro to operate in a similar way, storing the electricity it produces for when the grid needs it.

Peaking plants serve an important role in the New England electric grid. Like the Tunnel Jet generator in Preston, these fossil fuel-fired plants sit dormant for most of the year until the regional grid operator ISO New England sees the potential for the demand for electricity to outpace supply.

That’s when the peaker plants are called on to run in short spurts to make sure there is enough electric supply to power the grid. That will become increasingly important as weather-dependent renewables start to make up a larger share of energy production in New England, which is currently dominated by natural gas, Barton said.

“While that type of backup reliability has been, and will continue to be needed to ensure grid reliability, there can be no doubt that getting reliability from fossil fueled assets like this is something that we have to think hard about as we look at the necessity of combatting accelerating climate change,” Barton said.

While the battery’s role would partly depend on any conditions in DEEP’s battery procurement, Barton said the battery could serve a similar function to the peaking plant.

“This concept of storing 17 MW of backup power that’s on demand when the grid really needs it and the ISO calls on it, we absolutely will be able to provide that,” Barton said.

Barton said nobody will lose their job with the closure of Tunnel Jet. FirstLight has a team that operates its fleet of plants in the area, and none of those jobs will change. She said the battery project will create construction jobs when it gets to that stage.

There are several steps the project needs to go through before it can be built, including DEEP’s upcoming procurement for storage projects, environmental permitting and local siting approval. The biggest hurdle will be ISO-New England’s interconnection queue, where proposed projects wait for approval from the regional grid operator to connect to the grid, Barton said.

Jared Connell, New Leaf Energy VP of Development, said the queue has over 13,000 MW of applications for storage projects – a fraction of which have actually reached the final stage of interconnection agreements, and an even smaller fraction that has been constructed or is being constructed.

“This just highlights that these projects need many, many things to go well in order to be successful,” Connell said. “They need capital, they need expertise in engineering, they require patience as the project navigates difficult and lengthy interconnection studies, permitting, capacity market qualification processes.”

“All this is to say that, while this is a fantastic site and great project, nothing is ever an absolute for success. This project has many miles to go before it’s in the ground, and it will undoubtedly require the support of local policymakers,” Connell said.