The wake effects of upwind farms can be more significant than previously thought.
Optimal locations for wind farms can make a world of difference to their efficiency. If located in windswept areas either on land or offshore, wind farms can generate electricity in a steady and reliable way. Yet there is more to it than that. Upwind farms generate “wake effects,” whereby downwind wind speeds are decreased, and that can undermine a downwind farm’s potential to generate electricity and revenues.
These wake effects can be more significant than previously thought, according to a new study by three researchers in the United States. If wind farms are clustered too closely together along wind corridors, they can adversely affect one another’s efficiency, they explain.
The solution, the researchers, is to space out wind farms adequately because wake effects can reach up to 50km. “[W]ind farm wake effects are real, discernible and arise from clearly understood physical processes,” the authors of the study write. “These differences in wind power generation due to wakes have significant economic and environmental impacts.”
The researchers analyzed the impact of an upwind farm in Texas had on its downwind neighbor, which they found produced 5% less energy on average because of the wake generated by the upwind facility. That led to losses of revenue of some $3.7 million between 2011 and 2015.
“We show that although wake effects vary with atmospheric conditions, they are discernible in monthly power production,” the scientists explain. “In stably stratified atmospheric conditions, wakes can extend 50+ km downwind, resulting in economic losses of several million dollars over six years for our case study.”
In addition to its losses of revenue, the downwind farm surveyed offset around 111,000 fewer tons of CO2 emitted between 2009 and 2016 than it would have done had it not been located in the vicinity of the upwind farm. In other words, its loss of efficiency had marked consequences over time.
For want of available space, however, developers often situate wind farms in close proximity to one another along wind corridors, often unaware of the consequences. Routinely, wind farms are also set up next to existing transmission lines, which too increases the likelihood for overlapping wakes.
“The failure to recognise the issue and predictably provide solutions for conflicts may raise the cost of wind energy and thereby slow development,” the researchers note. “Given ongoing increases in global wind development, [there is a] need to understand physical, economic and legal interactions between wind farms to ensure sustainable development and stewardship of wind resources.”