Bent Tree Wind Farm undergoing refurbishment

Alliant Energy, which owns Bent Tree Wind Farm located south of Hartland, has a two-year project underway to refurbish its 122 wind turbines. According to project managers Rich Miller and Ed Gilkes, this year’s schedule calls for completing work on 44 of the towers, with the remainder scheduled beginning in May of 2027.

 

Miller and Gilkes explain Bent Tree became operational in February of 2010. General maintenance and repairs have been constant since then; this refurbishment project is expected to decrease the forced outage rate for repairs and will lead to an increase in energy output (availability) over the remaining expected life of the facility. The work, they point out, is “like for like” equipment replacement. The maintenance currently underway will allow the equipment at Bent Tree to continue producing the same amount of electricity it has since it opened, about 1.65 Megawatts per turbine, with combined output sufficient to power roughly 75,000 homes.

 

Gilkes and Miller say the refurbishment process is financially viable at this time because of a federal production tax credit available to facilities which make use of sustainable resources.

All summer near Hartland, three crews–each using a crane capable of reaching the tops of the 250-foot tall towers–are completing work at each tower, which begins with a drone assessment using high definition cameras to determine the condition of the three giant blades. The entire rotating assembly, that is, the three blades and the hub which connects them, is then removed from the tower, and repairs are carried out.

 

The project managers explain that, over time, the ultra smooth finish on the fiberglass surface begins to wear due to constant collisions with tiny airborne particles. The smooth finish is essential for reducing drag, and so any patches showing wear are given a new epoxy finish. Miller and Gilkes explain the hub is also serviced at this point in the process. Equipment inside the hub is responsible for supporting the blades and changing their orientation as needed during operation. Crews replace any worn parts and the mechanism is lubricated.

 

The generator inside the tower is also assessed and maintained. In addition to cleaning and lubrication, at the very least, the bearings are replaced along with the gearbox and main bearing. If it should be necessary, the entire generator can be changed out, drawing from a stockpile Alliant Energy keeps available for use on any of its wind farms. Information on the corporate website indicates the company manages more than a dozen wind farms located in Wisconsin, Iowa, and Minnesota.

 

The project managers mention that the three crews which have been working at Bent Tree all summer will be joined yet before the construction season ends by another seven or so crews currently completing work at a wind farm in Iowa. Next year, even more work crews are likely to be available, so that Bent Tree “will be a very busy place” beginning in May to ensure the project is completed before the end of 2027.