Neat rows of wind turbines dot seas and oceans across the world. But setting offshore wind turbines in straight lines may limit their power production, according to a new study.
Whether wind farms are on or off shore, there is a tradeoff between getting maximum energy from each individual turbine and packing a greater number of turbines into the space. As each turbine pulls energy from the wind, there is less energy in the downstream wind, which causes array losses for the entire wind farm. (Turbines not only affect their immediate neighbors, they can also affect other arrays miles away.)
But there may be a simple solution to boost energy production without expanding the boundaries of offshore wind farms. Researchers at the University of Delaware found that staggering turbines in the ocean can improve annual power capacity by 13 to 33 percent. The study appeared in the September issue of Geophysical Research Letters.
“Staggering every other row was amazingly efficient,” Cristina Archer, associate professor of physical ocean science and engineering and geography in University of Delaware's College of Earth, Ocean, and Environment, said in a statement.
The study used the Lillgrund wind farm near Sweden, which has turbines packed into straight rows, as its model facility. The researches then simulated six alternative configurations. Each of the simulations took weeks to run and accounted for the downwind eddies that turbine blades produce as they spin as well as the prevalent wind directions.
Some of the simulations looked at simply spacing the turbines further apart in rows, while others staggered the rows. Staggering every second row was the simplest method to improve capacity factor. The simulation showed that staggered turbines reduced array losses from 36 to 27 percent.
The most efficient combination was a both more spacing and a staggered layout, which dropped array losses to 14 percent and doubled the capacity factor for the wind farm.
Other researchers have developed complex algorithms to optimize wind farm patterns to maximize output and have also found that larger spacing can increase power production. But staggering could be a solution that allows for increased capacity without greatly expanding the footprint of wind farms.
The spacing of turbines, both in a single array and regional arrays, is just one consideration. Archer has also studied the seasonal variability of wind farms and how dominant winds can change throughout the year.
Despite the many factors that can reduce overall energy output, Archer’s previous research has shown that today’s wind turbines could supply energy for about half the world’s power needs.