2 buoys will help the U.S. explore vast offshore wind power potential

Source: Niina Heikkinen, E&E reporter • Posted: Thursday, September 18, 2014

Developers hoping to make offshore wind power a commercial reality in the United States have been slowed in part by one problem: None of the instruments measuring offshore wind speeds is recording winds at 600 feet above sea level, the height of the wind turbine blades.

This particular obstacle may soon be solved with the launch of two bright-yellow highly equipped research buoys designed to do just that.

Starting in November, $1.3 million buoys will begin taking measurements for up to a year at the sites of two offshore wind demonstration projects, one near Virginia Beach, Va., and the other by Coos Bay, Ore.

Previously, researchers had judged offshore wind power from extrapolated data of wind speeds measured at sea level or by using computer models, according to Will Shaw, who leads the Department of Energy-funded project at the Pacific Northwest National Laboratory.

Finding out how fast the winds are actually traveling will reduce risks for companies interested in investing in offshore wind, making the alternative energy source more feasible, Shaw said.

“The real motivation for doing this is we want to reduce the cost of offshore wind,” he said. “Data provided by the buoys will give us a much clearer picture of how much power can be generated at the specific sites on the American coastline — and enable us to generate the clean, renewable power sooner.”

According to the 2014 annual market assessment published last week by the firm Navigant Consulting Inc., the current estimated cost to install a 500-megawatt wind farm is $2.86 billion, or $5,700 per kilowatt. That cost is a 6 percent drop from estimates in the 2011 report.

As it becomes more affordable to produce, offshore wind power could become a major source of clean energy for both the coastal and Great Lakes states, areas that account for close to 80 percent of the U.S. electric demand, according to DOE.

In the United States, there are 14 offshore wind power projects that are in advanced development. The buoys will be measuring the wind speeds at two of the three demonstration projects each granted $46.7 million in federal funds in May. One of the demonstration projects is run by Dominion Virginia Power, which will have a 12 MW capacity. The second project is a 30 MW floating wind farm run by Principle Power Inc. in Oregon.

Both projects are expected to begin construction in 2017, after the buoys are done collecting data, said Shaw, who has worked with the developers of both projects.

Measuring wind speed with lasers

Weighing in at 20,000 pounds apiece, the buoys measure wind speed in much the same way that a police officer checks the speed of passing vehicles, said Shaw. But instead of using radio waves to measure wind speed, the buoys are equipped with advanced instruments called lidar devices that emit low-intensity infrared lasers. Lidar stands for light detection and ranging.

When the laser beams project upward from the buoys, the light strikes tiny particles in the air, dispersing them. The lidar device measures how long it takes for the light to return to the ocean’s surface. That information is then used to determine the speed and direction of the wind at a number of different heights above the buoy. The beams can reach up to 600 feet, which is the height of the wind turbines.

Measuring wind speed is complicated by the fact that the buoys are constantly moving on the surface of the ocean. To correct for this, instruments measure wave size (their height and period) and adjust the data accordingly.

Although many buoys have instruments to measure wind speed, they only have records of speeds near the ocean’s surface. Wind behavior can vary significantly at the height of the wind turbine blades, so extrapolating the data from these wind speed records is not always accurate, Shaw said. Researchers also rely on computer models to estimate wind speeds higher above the ocean’s surface, but to date there has been no long-term study over years and varying seasonal conditions that supports these models, he said.

In addition to recording data on wind speeds, instruments on the buoys will measure air and sea surface temperature, barometric pressure, relative humidity, and water conductivity. Once the project is underway, the Pacific Northwest National Laboratory will post the data the buoys collect in real time for anyone interested in using it for his or her own research.

“I’m optimistic, the systems are looking very good,” Shaw said. “We are eagerly anticipating going out to sea and getting started collecting data.”

Before the buoys are transported to Virginia and Oregon, the equipment will be tested in Sequim Bay and near the Dungeness Spit in the Strait of Juan de Fuca, which is between Washington state’s Olympic Peninsula and British Columbia’s Vancouver Island. The tests will ensure everything is working properly and to familiarize the investigators with the equipment, he said.

Big power potential, little U.S. experience

Offshore wind power in the United States is still a new alternative energy source that could have a lot of potential.

A DOE representative placed the wind-generating capacity of the area within 50 miles of the U.S. coastline at 4,000 gigawatts, about four times the amount of electricity produced in the country each year. Offshore wind projects are more appealing than building turbines on land, because winds tend to be stronger and more consistent, and the strongest winds with the most potential for energy production tend to happen during periods of high electricity use.

Capturing that much offshore wind power is unlikely anytime soon.

There is about 7 GW of offshore wind installed around the world, with over 1,700 MW of offshore wind power capacity added last year. Most offshore wind power development is in northwestern Europe, and about 47 percent (814 MW) of new capacity was in the United Kingdom. China is currently constructing 1,000 MW of offshore wind power. Overall, there was a 50 percent jump in new capacity development from 2012, but the rate of new development may be leveling off, according to the assessment report.

By comparison, the United States is just starting to transition toward demonstrating the commercial viability of offshore wind. The report was compiled for the Wind and Water Power Technologies Office within DOE’s Office of Energy Efficiency and Renewable Energy.