Measuring Offshore Wind Power
Through measurement sensor technology and the most extensive data to date, we are collaborating with stakeholders in Germany to advance offshore wind power.
WHY MEASURING OFFSHORE WIND POWER MATTERS
Our work with the Research at Alpha Ventus (RAVE) program delivers important knowledge needed for a vision of the future — a future where large and powerful offshore wind farms and other forms of Sustainable Energy generation will soon deliver a substantial portion of the electricity in Germany that used to be provided by nuclear power plants. Insights and experience that we gain from this project may also facilitate a broader pursuit of offshore wind generation around the world.
On the heels of the Fukushima nuclear accident in Japan, Germany passed a historic package of laws that commits the nation to a phase-out of nuclear power by 2022.1 In order to realize the bold goals of this unprecedented Sustainable Energy plan, successful, environmentally responsible and economically feasible generation of offshore wind power is critical.
Onshore wind power, though an important element in an overall renewable energy plan, does not have the potential that offshore wind power presents in the North and Baltic seas. Offshore, the wind speeds are greater than on land throughout the year, and there is less turbulence. It is also not necessary to limit the size of the wind turbines. On the other hand, there are greater investment and operating costs, and the maintenance and repair are considerably more complex than on land. To further complicate the issue, since Germany’s near-shore maritime areas are almost entirely protected as nature conservation areas, only areas in the exclusive economic zone (EEZ) can be considered for offshore wind energy (i.e., beyond the 12-mile zone).2 This means that, in comparison with those of its European neighbors, these wind farms will be situated farther away from the coast and at greater depths, creating conditions so different from other wind farms that it requires a completely new approach to equipment, operational procedures, maintenance, measurement and reintegration of Sustainable Energy into the power grid.
During the next few years, a dozen large-scale wind farms are being installed far off the coast of Germany in the North and Baltic seas. These are already earmarked to make up more than one-third of Germany’s installed wind energy output by 2020.3
WHAT THE RESEARCH DEMONSTRATES
RAVE is a revolutionary government-sponsored research initiative bringing together public and private stakeholders across the Sustainable Energy industry for a first-of-its-kind collaboration to accelerate the advancement of offshore wind power. The focus of this important research is to optimize offshore wind technology, providing critical feedback on efficiency, costs and environmental impact to wind farms currently in planning and development in the area. Located 45 kilometers north of Borkum, the Alpha Ventus test field began operation in April 2010 with 12 wind turbines. In 2011, 267 million kWh of wind power were produced there.4
The German Wind Energy Institute (DEWI), a UL company, has been responsible for developing, deploying and monitoring the technology to record accurate measurements on several of the wind turbines. In addition, we are providing critical long-term data through the FINO 1 research platform, where the most comprehensive wind measurements in the offshore sector in the world have been collected over the past 10 years.5
MEASUREMENT SENSOR TECHNOLOGY
The Alpha Ventus wind test field is situated in an area of the North Sea that is typical for offshore projects in the German Bight. The wind turbines have been constructed on foundation structures that, depending on the depth of water, can be up to 45 meters deep and are anchored in the seabed at a depth of up to 30 meters. Wind turbines at sea are subject to coupled loads caused by wind and wave conditions. Important research aspects can therefore be investigated here. These include the external operating conditions, structural dynamics, foundations for the wind turbines and, in particular, grid integration. The main loads on wind turbines are caused by environmental parameters such as the sea state, wind, sea wash, weathering, corrosion and scouring.6
In conjunction with our project partners in RAVE, we developed the measurement system necessary to capture critical data under the coordination of the Federal Maritime and Hydrographic Agency (BSH). To get accurate measurements, we equipped four of the 12 wind turbines constructed as part of RAVE with measurement sensors.7
Measurements are currently being conducted on the mechanical stresses and loads (vibration, expansion, torsion), electrical characteristic data and operational noises. In addition, oceanographic and geological studies are being conducted in the test field to investigate the interaction between offshore wind farms and the maritime environment. Temperature sensors have been mounted at various depths in the water to provide information on stratification and temperature changes in the test field. Numerous echo sounders on the foundations supply information on the scouring behavior and dynamics.8
Sensors to measure more than 1,200 parameters have been installed on the wind turbines, foundation structures for the turbines, transformer station and seabed. We transfer the data daily from the measurement computers to be analyzed and transferred to the central research archive, which can be accessed by the RAVE scientists.9
In the next few years, the focus of this important RAVE research will be on further optimizing the technology. Each small increase in efficiency and reduction in the specific investment costs will achieve a large overall impact on the 5,000 wind turbines scheduled to be constructed in German waters by 2030.10
Particularly important topic areas include the testing of new support structures and the optimization of existing ones, the further development of simulation tools, improved yield forecasts taking so-called farm effects into consideration, and research into new materials and anticorrosion strategies. The further development of remote sensing methods for measuring wind and the environmental compatibility, such as Light Detection and Ranging (LIDAR), also continue to be ongoing research topics.11
Note: DEWI is a leading expert in wind energy that was acquired by UL in June 2012. UL is committed to the field of renewable energy and will continue to advance this expertise globally.