What do you do when wind-farm plans go south, but the turbines and towers have been ordered? Ouch. This scenario played out not long ago in Oregon when the Federal government axed plans for a 10 turbine wind farm. It was too close to a military base, it said. Chinese OEM SANY was to supply the turbines and towers and the towers arrived first.
So now, nine good towers each capable of holding 2-MW turbines plus a damaged tower are sitting in the Port of Vancouver, Washington looking for a new home. To see if the 10th tower could be fixed, President of ph-consulting group inc. Peder Hansen was called in to provide an analysis. “It could be repaired but the owners considered the cost prohibitive,” he says. No big problem. Given the current building boom, the others should be easy to sell. Right?
Not exactly. “The nine good towers are still at the port because SANY is not selling this type of machine in the U.S. anymore, and wants to get rid of the towers,” says Hansen. However, there is a practical and a dynamic problem to the sale. The practical problem is that the bolt diameter in the top flange may not fit other turbines, and so would require an extra cost adaptor.
And the dynamic problem is one of natural frequency. If the vibrations generated by a different turbine are close to the natural frequency of the tower, it could eventually weaken by fatigue or embrittlement. “A solution would be to alter the speed of the turbine or add mass to the tower. Several people have suggested where to weld on more mass or add concrete ballast. Both fixes are widely viewed as unsatisfactory solutions,” he says.
Hansen however, suggest other possibilities. “Schools that train wind technicians might like a tower for its climbing, safety, and rescue classes. Then the dynamics of the tower are unimportant. Another thought was for an adventure company to train people in climbing and rappelling,” he suggests.
Hansen says he sure there are many other ideas. If you have one, let him know.
Filed Under: News, Towers