Although there’s still a lot to do, the world has come a long way in terms of renewable energy in the past few years. We’re becoming less reliant on fossil fuels every day, and advances in wind and solar technology are allowing some countries to be entirely powered by renewables (sometimes more than once over).
One of the best sources of renewable energy in the world is wind power – and one of the best sources of wind power is offshore wind farms. That’s why the industry has exploded over the past decade, increasing 12-fold since 2010. The Biden administration has recently given the go-ahead for the first US offshore wind farm, and Denmark is even building a wind farm island in the North Sea.
But according to a team from the Institute of Coastal Systems at Helmholtz-Zentrum Hereon, this dramatic increase in the number of wind farms doesn't necessarily translate into the same dramatic increase in power output. In German waters, where wind farms are now responsible for a power output equivalent to that of around eight nuclear plants, the researchers found that the farms are producing up to 25 percent less energy than expected – and now they know why.
“Our results show that clusters of large wind farms … have the potential to substantially modify the atmospheric dynamics,” explains the team in their paper, published this week in Scientific Reports. “[This can] lead to local mean wind speed reductions extending as far as more than 40 km [25 miles] downwind from the farm.”
In their study, the team looked at current and planned wind farms in the North Sea. Using a sophisticated computer modeling system, they then calculated the wind speeds that could be expected with this collection of farms.
“Our simulations show that the development of massive clustered OWFs [offshore windfarms] significantly impacts the wind climate and efficiency of renewable energy production on a regional scale,” confirms the paper.
The team found that the atmospheric effect followed a cyclic pattern throughout the year, with the biggest drop in wind speed occurring around March or April, when the weather is relatively calm. At the other end of the year, in November and December, the stormy, unpredictable weather results in a smaller wake effect from the farms.
“The wake [extent] varies,” explain the authors, "[I]t depends on wind speed and atmospheric stratification and might extend up to 70 km downwind.”
Windfarms are currently quite often built in big clusters along transmission lines, as is this minimizes cost. But this new research shows that there may need to be a new cost-benefit analysis in the design of future farms, since building too many too close together can significantly reduce the amount of power they produce.
“[Offshore windfarms] have the potential to develop into dominant ecosystem drivers,” conclude the authors. “Therefore, an optimization strategy based on both national and international considerations is required to minimize economic losses and to assess the limits and environmental impacts of industrial offshore energy production.”