WILLMAR -- Although some people may not believe it, Willmar Municipal Utilities' two wind turbines during their second year of operation have been available for energy production 93 to 94 percent of the time compared to the national average of the mid-to-upper 80 percent range for turbines of similar size, according to Bruce Gomm, utility general manager.
Gomm made the statement Monday during a status report on the turbine project to the Willmar City Council. Gomm was referring to down times when the public sees the turbines are not turning because of maintenance and repair issues.
Council member Ron Christianson asked Gomm if all turbines go through this.
"We have done the comparison ourselves and compared to the national average of availability of these same-size units, looking at the whole nation for a 2-megawatt-class turbine, you look at the amount of availability time and for our units they have during the second year been running 93-94 percent available,'' Gomm said. "So we're doing better than the national average.''
Gomm said a lot of people might not believe that because they see the turbines are not turning.
"But the thing that you don't see is running all night long, all weekend long or the time that you haven't had a chance to look at it,'' Gomm said. "We track that very closely and they're doing better than average.''
Gomm said he was glad to speak to the council but waited until the report on the first year of operation and production was completed.
The turbines were built and went into service in September 2009, partially to meet the state's renewable energy standard; because the utility saw the turbines as another economical source of generation for the city; and as a way to be environmentally responsible in light of the fact that the utility power plant consumes coal as part of the city's energy needs for electricity and heating.
"We did not proceed with the project until we were sure that they were economically viable,'' Gomm said. "I'm sure that's what most people are concerned about. We hear a lot of that concern in the community. I can assure everybody that our report of the first year does confirm it is a financially feasible project.''
He said the numbers came in a little bit better than expected in one respect and little worse in another,
The worst was that average wind speed for the year was a below average, which was consistent with reduced wind speed in the whole region. Gomm said there is no way to predict wind speed.
With reduced wind, the utility should have received less production, but the turbines did better than the power curve showed that they should have done, Gomm said.
Production was lost due to down time for various maintenance issues, but the loss was covered by warranty payments from turbine maker DeWind Corporation.
"But taking all the numbers into account, the units produced power at the anticipated rate of less than 5 cents a kilowatt hour, which is actually not much more than what we're paying for our average power supply costs,'' Gomm said.
The disadvantage with wind turbines is energy can't be scheduled. "You don't know when it's going to come. You have to take it whenever it's there,'' he said.
Fortunately, the turbines are connected directly to Willmar's grid and there are no transmission constraints that big wind farms face, he said.
Gomm said the utility continues to have maintenance challenges that are covered under warranty. He said three workers are tightening the Fiberglas nose cone over the hub of one turbine that had loosened and was making a clunking sound when the blades turned. He said the unit should return to service in a day or so.
Gomm said the utility is evaluating the value of extending the warranty for up to three more years. "I'd say right now we're leaning towards extending, but not decided yet,'' he said.
Overall, Gomm said, the units are doing well.
"They are doing what we anticipated them to do and we're very pleased with the performance,'' he said