Where the Wind Blows

A CIRES scientist investigates the unknown: offshore wind at the heights of modern wind turbines

The sort of wind that tosses around a person’s hair and upends umbrellas just doesn’t cut it for wind energy producers. They’re not interested in ground-level winds.

Rather, energy producers want to understand what’s going on 100 meters (about 330 feet) or higher in the air—the heights of modern wind turbines.

Unfortunately, scientists’ understanding of these higher-up winds—which can whip in a different direction than surface winds or blow stronger or weaker—is limited. Few studies have focused on wind patterns at these heights, especially over the ocean. That’s a problem because offshore is where many energy experts envision wind farms in the future.

So CIRES’s Yelena Pichugina, working with CIRES and NOAA colleagues, has figured out how to capture detailed portraits of those elusive turbine-height winds, both onshore and offshore. Pichugina used NOAA high-resolution Doppler lidar measurements to track these high-blowing winds’ behavior. Doppler lidar instruments send out laser beams that bounce off aerosol particles in motion. Sensors pick up the reflected laser light, giving researchers information about the direction and speed of the wind.

“We show that Doppler lidar is a powerful tool for understanding offshore winds at turbine height,” Pichugina said. She hopes the concept may eventually help wind energy developers faced with tough decisions about where to deploy wind farms offshore.

In 2004, a NOAA-led research team installed a Doppler lidar on a ship in the Gulf of Maine, to make wind measurements in support of a New England air quality research project. A unique motion compensation system, developed by NOAA’s Alan Brewer and his engineer colleagues, let the device capture exquisitely detailed measurements of shifting winds.

Post-analysis of the data showed consistent differences between night and day wind speeds and directions, and revealed how quickly winds could shift—an important factor in wind energy production. The scientists also identified wind patterns that were due to the shape of the coast itself, and differences between near-shore areas and those farther out—information that could be critical for siting wind farms.

Pichugina said there are many similar data sets, from offshore and land studies, that could help researchers better understand winds at the height of modern wind turbines. It takes time and effort to extract that information—finding the full data sets, quality-checking and analyzing data—but that’s far cheaper than the alternative of collecting new data, especially offshore.

“You can imagine the challenges in making wind profile measurements in the marine boundary layer,” Pichugina said. On land, a scientist might install instruments on a tall tower, but to build a tower in the ocean is expensive. And like tall towers on land, measurements made in one spot over the ocean would only provide information about only one relatively small region.

As wind farms continue to expand, it becomes even more important to move beyond using surface measurements to estimate wind behavior at turbine height. CIRES and NOAA scientists hope to address this issue by continuing detailed analysis of unique existing data sets of lidar wind measurements.

Their hopes are to supply a more relevant indicator of wind behavior than simply another bad-hair day.