Orsted Downgrades Wind Output Forecasts: Report

Major wind-power generator Orsted has found that the wind output from its turbines is less than it had expected, following analysis of data from the Danish utility's UK Westermost Rough project, the Financial Times reported January 6.  It found that it was not only turbines downwind of a turbine whose performance was affected, but also those to the side of it. And wind slows down as it approaches a turbine too. This latter effect, called 'blockage', means that individual turbine losses affect neighbouring turbines' output too, the overall effect being greater than the sum of the individual effects.

"Orsted hypothesised that as more offshore windfarms are built, there could be higher wake effects from neighbouring windfarms," the report says, citing also research by Norwegian DNV GL, which has found that the turbines in the front row of a windfarm will generally produce less than they would in isolation. "Every percentage point improvement in output makes a difference as profit margins tighten," the report says.

Orsted published its findings last October but since then other developers, including Iberdrola and SSE, have said that the research had not changed their own analysis of their profitability, the Spanish company saying that its investments had done better than the conservative forecasts had predicted at the time of project sanction.