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.