For offshore turbines, such as those found off coasts in Europe, this approximation is valid. However, Hu explained, even seemingly flat land, like in Iowa, can make an appreciable impact on wind energy production.
Hu and his team are using wind tunnels, miniature generators and scale models of wind turbines to see how rolling hills, ravines and ridges can affect energy output. "Recently, we found that if you have a hill [near a wind farm], the distance between the wind turbines can be reduced significantly. Energy can be recovered faster," said Hu. "We can quantify how that decay will interact with the next row of wind turbines."
The researchers observed flow fields and vortices created by spinning blades and published some of their findings online in the Journal of Visualization last November. In addition, Hu is investigating how turbine operators can compensate for weather effects like icing on turbine blades.
With this information, energy developers can plan wind farms better, but also extract more energy from their existing turbines while minimizing wear and tear on their hardware.
What's going on at the hub?
However, over a turbine's operating life, the climate becomes a larger factor. "If we take the intermediate term, a five-year basis, there have been some studies that show there have been some periods where wind speeds are significantly above or below the long-term average," explained Eugene Takle, a professor of agricultural meteorology at Iowa State.
"That's the scale that's relevant for people that are investing in wind power," he said. Long-term predictions can also help utilities plan new generators to meet future demand.
According to Takle, predicting wind speeds that are relevant for wind turbines is still an emerging process. "One of the challenges we have is that most of the models we use don't have a long history of application and validation for forecasting wind at the hub height of these turbines. We've used these forecasts for years to forecast winds near the surface of the Earth," he said.
The reason that's important, particularly in places in the central United States, he explains, is that winds at the height of the hub of a wind turbine, roughly 260 feet, are different from the winds at the surface.
Like Kamath, Takle did acknowledge that the simulations need to be validated with field studies, measuring how accurate their predictions are in the real world. He said that using tools like weather balloons, airplane-mounted instruments and laser radar, scientists can test their simulations.
Eventually, the scientists hope to reduce the uncertainty in wind forecasting, lowering its overall costs and increasing its reliability.
Reprinted from Climatewire with permission from Environment & Energy Publishing, LLC. www.eenews.net, 202-628-6500