A recent study from the Max Planck Institute investigating the efficiency of large-scale wind farms claims that large-scale wind energy deployment slows down winds in and around a wind farm, therefore reducing wind turbine efficiency.
A Brief Wind Energy Science History
In my time here at CleanTechnica I have covered a lot of wind energy stories, and read a lot more. Subsequently, I had already come across studies over the past few years which have dealt with the potential loss of efficiency in a wind farm. Wind turbine placement is imperative to reaching the highest level of efficiency possible for any wind farm. Stick a wind turbine directly behind another, and there will be an obvious loss of wind making it through to the second turbine. Back in 2011 computer researchers from the University of Adelaide in Australia and MIT in the US were using a “selection of the fittest” step-by-step approach to determine the best placement for wind turbines. In 2013, a study from the University of Delaware concluded that efficiently spacing or staggering wind turbines can increase offshore wind energy by up to 33%.
Looking farther afield, a study published in 2014 found that the development of wind farms in Europe only have “an extremely limited impact” on the continental climate, meaning that the number of wind turbines installed (through to 2020) are unlikely to be causing changes to the climate by literally stealing wind from the atmosphere. And in 2015, a study conducted by an international research group continued the studies into the impact a wind farm might have on the climate and lower atmosphere, but concluded that at the time there was no project operating or currently planned that came even close to the size and concentration of wind turbines to begin yielding diminishing returns.
So when I came across a study from the Max Planck Institute for Biogeochemistry in Jena, Germany, with suggestions that lowered the expectations of wind energy when used at large scales, I was immediately suspicious.
The Basics of the Max Planck Study
The report highlights what has been highlighted before — that every wind turbine takes kinetic wind energy out of the atmosphere and converts it to energy. The authors of the study state the obvious, that there will be a reduction in wind speeds across a large-scale wind farm — though that’s not their primary point. As we have seen, proper placement of wind turbines do a lot to mitigate these diminishing returns. Rather, the Max Planck study ran two models which provided them with results suggesting that if there were too many large-scale wind farms in a close area — say in the North Sea, for example — they would begin affecting one another, and reduce the available wind speeds and kinetic energy in the region.
“One should not assume that wind speeds are going to stay the same with a lot of wind turbines in a region,” said Dr. Lee Miller, first author of the study. “Wind speeds in climate models may not be completely realistic, but climate models can simulate the effect that many wind turbines have on wind speeds while observations cannot capture their effect.”
Specifically, the authors found that when wind energy was used at its maximum potential in a given region, each turbine in the presence of others would on average only generate about 20% of the electricity compared to an isolated wind turbine.
Further, on land, the authors of the study determined that only 3% to 4% of land areas have the potential to generate more than 1 watt of electricity per square meter of land surface, with a more typical potential of about 0.5 watt per square meter or less.
Say Goodbye to Reality
Given all of this, I decided to take my concerns to my friends at the American Wind Energy Association. Michael Goggin, AWEA’s Senior Director of Research, sums up what I initially thought: “While interesting as an academic exercise, this paper has no bearing on the prospects for wind deployment in the real world.”
Specifically, Michael Goggin explained that “The level of wind deployment examined in this analysis is absurd, blanketing the entire planet, including the oceans, with enough wind turbines to meet humanity’s electricity needs 100 times over. For reference, the study assumes the installation of 5,400,000 GW of wind, around 12,000 times more than the 450 GW of wind installed globally today.”
Michael Goggin explained to me that, at a recent gathering of leading wind energy experts at Harvard, the unanimous verdict of all present regarding the wake effects of wind production was that there was no chance these effects would hinder wind energy’s potential to meet humanity’s energy needs.
The reality is, wind energy resources are so staggering and widespread, that in many cases a region or country’s wind energy resources could supply total electricity coverage numerous times over. We saw that back in 2015 when the Lake Erie Energy Development Corporation studied the offshore wind energy potential for America. Michael Goggin similarly pointed to an analysis by the Department of Energy and the National Renewable Energy Laboratory which concluded that the US has enough developable, high-quality wind energy resources to supply the country’s electricity needs more than a dozen times over — an estimate which is probably now conservative, as it is based on older wind energy technology such as 80-meter wind turbines.
In this day and age where there is so much political activity surrounding energy resources, it should come as no real surprise that there are studies and reputable institutions putting out research which is less than legitimate. Whether or not this was the intent of the Max Planck Institute is up for debate, but the facts don’t speak well of their methodology.
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