The first wind farm repowering in Minnesota

January 21, 2022
The Trimont Area Wind Farm (TAWF), located in Martin and Jackson Counties, was Minnesota's first commercial-scale, landowner-developed wind farm -- and the first in Minnesota to undergo a repower.
wind power

History of the Trimont Area Wind Farm

The Trimont Area Wind Farm (TAWF), located in Martin and Jackson Counties, was Minnesota’s first commercial-scale, landowner-developed wind farm. This project was a collaborative effort between Avangrid Renewables (Avangrid) and 43 landowners in the community, and after three years of planning and development, the 67-turbine wind farm began operation in 2005.

The Trimont Area Wind Farm has a Power Purchase Agreement (PPA) with Great River Energy (GRE), and power from the farm is sold to Xcel Energy in an arrangement to use the utility’s transmission lines. In 2005, TWAF was expected to generate 100.5MW of clean energy equivalent to the annual electric consumption of 29,000 homes served by Great River Energy’s 28 member cooperatives.

The TWAF not only helps reach local and statewide clean energy and clean air goals, it also provides many benefits to participating landowners and local communities. The landowners benefit from revenue participation, as well as from traditional easement payments. The community benefits through production tax revenues from the project.

wind power

The repowering process

Avangrid conducted a feasibility and economics study to survey the leases they currently held to see where opportunities for a repower existed. They were looking to make existing assets viable for a longer-term – make them more economically feasible, as well as enhance their performance. The federal government incentivizes repower initiatives by offering a new production tax credit for repowered sites, as long as 80% of the existing materials are replaced. Given the additional tax credit on top of enhanced performance and increased output even at lower wind speeds, Avangrid made the decision to repower TWAF.

The upgrades consisted of retrofitting the existing wind turbines by replacing turbine equipment with new components. The turbine retrofits included replacing equipment in the nacelle (such as the gearbox, oil cooler, drive shaft, and pitch drive), refurbishing the generator, replacing the rotor (nose cone, hub, and blades) and updating the electronic controls. These upgrades allow the turbines to operate at lower wind speeds and increased individual wind turbine outputs to 1.62MW (from 1.5MW), which brought the overall output of the farm up to 107.5MW.

Part of the repower plan involved increasing the wind turbine’s rotor diameter. Larger rotors produce more noise, so Avangrid ran an additional sound study to limit the impact of their farm on the surrounding community. The result was a series of blades that have sound dampeners built onto them, and these blades can be found on 12 different turbines around the plant.

“Because we’re increasing our net capacity factor and we’re able to run these turbines now in lower wind and still produce that power, I would think that we should see an overall increase in that production tax that goes out both to landowners as well as the counties,” said Bill Swan, the Plant Manager at Trimont and Elm Creek. Prior to the repower project, the farm was contributing $1.7 million and $2.6 million in taxes to Jackson and Martin County, respectively. After the repowering project, the farm now contributes $2.3 million and $3.5 million, respectively – a 35% increase in annual revenue to the counties.

windmills on a farm

Meaningful partnerships

Throughout the repowering process, Avangrid relied heavily on their positive relationship with GRE. While GRE is the offtaker of the energy produced at the plant, the relationship goes beyond the project. Before the COVID-19 pandemic, Avangrid hosted GRE for annual meetings to discuss how to maintain and diversify GRE’s energy portfolio.

“At the end of the day, we need to increase [our] portfolio and we need to increase the opportunities that we have to make green power,” said Swan. “And I think that GRE is on board with that, and them showing up here and listening to us with an open ear really shows that.”

The project also formed relationships with community members. As part of the repowering agreement between the county and the state, the project utilized Minnesota union workers, and Avangrid hired Mortenson and General Electric. With over 200 employees on-site at the beginning of the pandemic, safety became a top priority in this project – not just for the routine safety precautions surrounding the equipment, but new measures regarding the health of the workers as well.

“Safety really was number one here, and I just really want to push that out,” said Swan. “When we’re looking at doing construction projects or repower projects, by doing repower versus building new, we can reduce some of [the] risk [to our employees].”

The future of repower projects in Minnesota

As wind turbines age, their efficiency declines, and therefore the economic return to the company decreases as well. As operators look to replace these failed components, they are finding that some parts are outdated or no longer available, so repowering will be more common as farms reach the end of their lifecycles.

“When I first graduated from college, we were told that turbine life expectancy was about 25 years – that included full decommissioning of the foundations, the towers and everything. My understanding now is that new wind farms are projected to last 30 – 35 years. After that, there will be a need for more of the feasibility studies like we did here at Trimont. We came in, and we started looking at the underground cable collection system, the substation, the foundations, the roads, and we realized that a lot could be done here without adding a lot [of new equipment],” explains Swan.

Repower projects are relatively uncommon across the state, which means there are fewer concrete regulations in place. For the Trimont repower, Avangrid found themselves talking through more state permitting processes with their regulatory attorney than they had originally expected.

“I don’t know that I would necessarily go so far as to say that we wish that there was a specific rule about how to do repowering,” said Jacobs, “but I think flexibility is helpful. Hopefully, the state had some lessons learned from our project too, so that it goes a little bit smoother for the next group of people.”

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