ØRSTED has referred to an industry-wide issue following the announcement that the company had overestimated the amount of power that offshore wind turbines are able to produce.
This could mean revenues from its facilities are significantly lower than expected as generation figures fail to live up to initial production forecasts.
According to Ørsted, the company’s production forecasts underestimated the negative impact of two effects across their asset portfolio, the blockage effect and the wake effect.
The blockage effect arises from the wind slowing down as it approaches the wind turbines. This causes an individual blockage effect for every turbine position and a global effect for the whole wind farm, which is larger than the sum of the individual effects.
The company’s new wind simulation models show that they had historically underestimated these blockage effects.
This finding was also supported by industry consultant DNV GL’s recent report on blockage, which indicates that this effect is more broadly underestimated.
The second effect is the wake within wind farms and between neighbouring wind farms. There is a wake after each wind turbine where the wind slows down.
As the wind flow continues, the wake spreads and the wind speed recovers.
This effect, with wind turbines shielding and impacting each other, has been subject to extensive modelling by the industry for many years.
Ørsted’s previous forecasts had underestimated the negative impact of the two effects across their asset portfolio – the effect of wind turbines blocking and slowing the wind flow to the rest of the wind farm behind them, reducing the amount of power that can be generated.
With respect to wake effects between neighbouring wind farms, the company states that they are in the process of developing a new model capable of more accurately predicting wake effects over longer distances.
As this is referred to as an industry-wide issue, this revelation can be interpreted to suggest that other wind power producers could face similar findings in their production records in the future.
ICON spoke to RenewableUK, the trade association for wind power, about their impressions following Ørsted’s announcement.
Luke Clark, RenewableUK’s Director of Strategic Communication, said: “The offshore wind industry has done a huge amount of analysis of blockage and wake effects, and that’s led to developments in the layout of wind farms to minimise these effects and maximise production.
“Developers understand that load factors vary at different sites and at different times. As we learn more, we’ll see further innovation and the industry is already using larger, more productive turbines which will drive growth over the next ten years, so that offshore wind will meet at least a third of UK power needs by 2030”.
Ørsted stressed that their findings would not prove a major setback for the industry and said offshore wind energy remained significantly more competitive than gas or coal.