Researchers in California may have found a way to make wind farms more efficient. California Institute of Technology researchers have revisited some of the fundamental assumptions that guided the wind industry for the past 30 years, and now believe that a new approach to wind farm design may improve their efficiency.
Their design places wind turbines close together instead of far apart.
This challenges the common notion that the only remaining improvements in wind energy are in developing larger turbines or putting them offshore.
"What has been overlooked to date is that…wind farms are still rather inefficient when taken as a whole," says John Dabiri, professor of Engineering and Applied Science, and director of the Center for Bioinspired Engineering at Caltech. "Because conventional wind turbines must be spaced far apart to avoid interfering with one another, much of the wind energy that enters a wind farm is never tapped. In effect, modern wind farms are the equivalent of 'sloppy eaters.' To compensate, they're built taller and larger to access better winds."
But this increase in height and size leads to increased cost, difficulty in engineering and maintaining the larger structures and radar interference problems.
Dabiri is focusing on a more efficient form of wind 'farm' design, and focusing less on individual wind turbine efficiency.
"The available wind energy at 30 feet is much less abundant than that found at the heights of modern wind turbines, but if near-ground wind can be harnessed more efficiently there's no need to access the higher altitude winds," he says. "The global wind power available at 30 feet exceeds global electricity usage several times over.”
The challenge is capturing that power.
The Caltech design does this by relying on vertical-axis wind turbines (VAWTs) in arrangements that place the turbines much closer together than is possible with horizontal-axis propeller-style turbines.
VAWTs provide several immediate benefits. They have a much simpler design (no gearbox or yaw drive) that can lower costs of operation and maintenance and reduce environmental impacts.
Two of the primary reasons VAWTs aren't more prominently used today are because they tend to be less efficient, and the previous generation of VAWTs suffered from structural failures.
Field data collected by the researchers last summer suggests that they're on the right track, but this is by no means 'mission accomplished.' The next steps involve scaling up their field demonstration and improving upon off-the-shelf wind turbine designs used for the pilot study.