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Wind turbine undergoes repairs

MORRIS – For almost a decade, the West Central Research and Outreach Center’s wind turbine has been a fixture sitting on the horizon outside of Morris. The tower serves as a landmark for visitors to Morris and the WCROC.

But for several weeks this spring, the turbine was noticeably still – the result of some worn parts inside the structures generator equipment.

Last week, service technicians with Vestas, the turbine manufacturer and service provider, arrived in Morris to replace the existing generator and get the turbine up and functioning once again.

The wind turbine was built with a $2 million grant received from the University of Minnesota’s Initiative for Renewable Energy and the Environment (IREE). Since initial operation in March of 2005, the turbine has generated a total of 44,910,081 kilowatt hours and over $2 million in gross revenues.

On average, the turbine generates roughly $800 of electrical energy each day. After taking out maintenance and repair expenses, half of the remaining net revenue is used for renewable energy research and the other half is used to support WCROC operations. Currently, UMM transfers to WCROC a monthly set fee for a minimum of 4.3 million kilowatt hours delivered to the campus each year. The remainder of the electricity is used to power the Renewable Hydrogen and Ammonia Pilot Plant.

Through the years the turbine has required relatively minor maintenance and repair. However, as the machine ages, major repairs including replacement of the generator, gearbox, and main bearings are inevitable. The components generally have a lifespan of about 20 years. The generator is usually the first piece that needs repair, said Mike Reese, WCROC renewable energy director.

During heavy winds this past spring, the turbine began to shut down due to high vibration. Maintenance technicians were on site trying to correct this issue as well as to perform the semi-annual maintenance. On May 27 the turbine began shutting down due to high temperatures at a generator bearing.

When technicians inspected the equipment, they discovered that one of the two generator bearings was worn out. This issue may have been responsible for the earlier vibration. The bearing race also had spun on the generator shaft causing significant pitting. This damage is a serious and costly issue.

Technicians with Vestas offered two options – repair the pitted bearing for about $65,000 or replace the entire generator with new shafts and bearings for about $175,000.

The WCROC staff opted to replace the generator, since the repair may not work and the aging generator would likely need to be replaced within the next two years anyway, said Reese.

Staff at the WCROC believe this repair will provide the least financial risk and most value moving forward. Approval was given by U of MN Purchasing to proceed with a contract and WCROC authorized Vestas to start the repair and generator replacement.

The generator was delivered to the Vestas service facility in Tyler, Minn. A mid-sized crane (on five semi-trailers) was brought in to hoist up the new generator and remove the old one. Service technicians will then hook up the new generator. The University carries insurance for equipment failures and loss of revenues, so staff will be working with adjusters to recoup some of the losses.

Once the generator is replaced, the wind turbine should continue to produce power for at least another decade.