Willmarites have been able to monitor and observe the operation of our two new wind turbines for several months now. Recent letters and stories in this newspaper, and numerous questions and comments received, prompt me to present some information concerning the Willmar turbines in particular and wind power in general.
The Willmar turbines were commissioned for full power operation in July and August. However, as is always the case with projects like these, problems remained on the fix-it list at the time of commissioning, such as paint scrapes on the towers, chips on the blades, electrical relay settings that we didn't know were set incorrectly until they did their job and shut down the turbine at the wrong time, missing cold-weather components we didn't know were missing, etc. Many of these "bugs" were corrected without having to interrupt the turbine's operation, but some either shut down the turbine or required the turbine to be stopped while corrections were made. This type of fix is the principal reason why occasionally one turbine has been seen to be turning while the other is stopped.
While nearly all of the above type of problems have now been corrected, another reason one turbine might be stopped is variation in wind speed. Simply put, the wind must be blowing at a sufficient speed before the rotor will begin to turn. Bear in mind that wind is by nature variable from place to place, and if the wind is only just fast enough to turn the blades of one turbine, it might not be fast enough at the other turbine. I have observed on Buffalo Ridge, narrow "rivers" of wind that are just fast enough to turn wind turbine rotors, where the path of the "river" is revealed by a line of turning rotors between still rotors.
As time passes and the software glitches and settings are corrected, and the turbine rotating components wear in, this type of issue will disappear. Remember these turbines will be turning for 20 years or more.
One more thing to remember -- if you add up all the power any turbine will produce in a year, it will never be more than half of the maximum possible. This is of course because the wind is sometimes calm and sometimes light and so the turbines can most times produce only partial power. On average we can expect to see the rotors actually turn less than two-thirds of the hours in the year. Nevertheless, this is fine -- we looked at Willmar's average wind speed and projected the turbines' power output, so we knew in advance the economics of this project were good. Regardless of a slow start, over the life of these turbines the cost of the electricity produced will be less than the cost to purchase it from the grid.
Jon Folkedahl is president of Folkedahl Consulting Inc., Willmar.