Offshore Windmills Can Break Like Matches
Medium-sized waves can break wind turbines at sea like matches. These waves occur even in small storms, which are quite common in the Norwegian Sea.
“The problem is, we still do not know exactly when the wind turbines may break,” says Professor John Grue from the Department of Mathematics at the University of Oslo. Grue is one of the world’s foremost experts on wave research. In 1989 he discovered an inexplicable wave phenomenon called ringing, which is a special type of vibration that occurs when choppy waves hit marine installations. The discovery was made in a 25-metre long wave laboratory located in the basement of the mathematics building at Blindern Campus.
So far scientists have studied ringing in small and large waves, but as it turns out, ringing is more common in medium-size waves.
For wind turbines at sea with a cylinder diameter of eight metres, the worst waves are those that are more than 13 metres high and have an 11-second interval between them.
UNFORTUNATE WAVE POWER: When waves above 13 metres hit wind turbines, an unfortunate force arises at the rear of the turbine. This is called ringing. John Grue is now looking for a general mathematical formula that can explain the special phenomenon.
The ringing problem may increase significantly in the years ahead. There are plans to build tens of thousands of wind turbines at sea.
“If we do not take ringing into consideration, offshore wind turbine parks can lead to financial ruin,” warns John Grue.