CRMC, international team to research wind turbine engineering

April 10, 2019, Providence – The Rhode Island Coastal Resources Management Council (CRMC) will be overseeing a 28 month research project examining the engineering of the Block Island Wind Farm’s jacketed support structure. The results of this study will be utilized in many other wind farm applications worldwide.

The Bureau of Safety and Environmental Enforcement (BSEE) and the Bureau of Ocean Energy Management (BOEM), agencies of the U.S. Department of the Interior, have identified a gap in the industry knowledge base with regard to the design and operation of offshore wind infrastructure in the Atlantic. In order to close this gap, BSEE has awarded a team of engineers and other specialists led by the CRMC, in cooperation with the University of Rhode Island’s (URI) Ocean and Civil Engineering Departments, Tufts University and the Norwegian Geotechnical Institute (NGI), $608,722 to study the United States’ first commercial project, the Block Island Wind Farm operated by Ørsted U.S. Offshore Wind.

Block Island Wind Farm turbine 1

Jacketed wind farm support structures, as currently used in the offshore oil and gas industry, are a popular option for use in mid-depth (30 - 60 meters) offshore wind farms. Data from this study will assist BSEE, BOEM and CRMC to develop regulatory standards and industry recommendations for this rapidly developing U.S. industry.

Wind farm developers choose support structures based on water depth, cost, seafloor characteristics, enforceable policies, and construction noise, among other factors.

“Monopile support structures are the dominant technology for existing offshore commercial wind farms installed in shallower water,” said David Ciochetto, an ocean engineer at the CRMC, and manager for the research project. “Jacketed structures are rarely used in wind farms in Europe; these structures are more common to offshore oil platforms. It’s not the same application, though, as a wind turbine is designed to extract 40 to 50 percent of the wind energy exerted on it so we are dealing with a much different interaction of the structure with the environment. We’re not certain how these structures will react throughout their operational life to the forces of the wind experienced off the Atlantic coast with fewer upwind obstacles and more frequent hurricanes.”

The research team consists of Ciochetto, Dr. Christopher Baxter from URI, Dr. Eric Hines from Tufts, Per Sparrevik from NGI, Dr. Babak Moaveni, also from Tufts, Dr. Aaron Bradshaw and Dr. James Hu, also from URI, and Dr. James Strout, also from NGI. Ørsted/Deepwater Wind representatives and their affiliates, led by URI Ocean Engineering alumni Stephen Wilkey, are also working with the team. This team is working closely with offshore wind and energy experts within BOEM and BSEE.

The project will have four tasks. The team will first develop a suite of sensors to be affixed to the turbines. Measurements of accelerations at different turbine locations will be taken to determine the resonant frequencies and soil damping. Stresses and bending moments will be determined at different locations on the turbine structure, including at the tower and jacket interface. Possible tilt of the jacket structures from foundation soil displacement will be measured. And the team will assess the actual fatigue of the overall structure by analyzing cyclical stress and strain on the structure versus design assumptions.

“The study aims to verify that these structures as engineered and installed will meet or exceed their 30 to 35-year design life,” Ciochetto said regarding the research study. “This will help inform BSEE, BOEM and the CRMC, and will also help inform other states that are looking to develop offshore wind. This project also encourages cooperation between industry, universities and government establishing a path into the future to continue this collaboration.”

The team will be developing the sensor systems beginning in May of this year, and then Ørsted will install a temporary data collection system on the structures to record about 30 minutes of data to help determine the best placement for the sensors that will be deployed for an entire season. Monitoring will begin in May 2020 with the project wrapping up in December 2021.

Ciochetto outlined a host of logistical obstacles to overcome to prepare for the project but is confident that Ørsted U.S. Offshore Wind and their parent company Ørsted are committed to the success. The team must also make sure the warrantee on the turbines isn’t voided, so nothing can be directly welded onto the structures and protective coatings will not be removed from the installed structures. NGI are experts in measurements on offshore structures and are developing innovative ways to obtain the measurements.

“The team is making the sensors robust – it’s a very harsh environment,” he said. “Like the wind farm, the team’s sensors and data communication networks will be exposed to the salt spray, wind, sun and possibly the larger waves for an entire season. Cables will need to be attached to the large structure to connect the various sensors to a computer system recording the data and transferring it to shore. All of this must be developed and installed on the existing structures with the rotor hub 110 meters off the surface of the water. We also have to build a communication system to monitor the sensors and retrieve data for the structural analysis by Tufts and URI. I am confident that the team assembled for this project is up to the task. BSEE, BOEM, CRMC and the team are all eager to begin this study and close this gap in the industry knowledge base for future growth of the offshore wind industry off the coast of the United States.”

This study is funded by the Bureau of Safety and Environmental Enforcement (BSEE), U.S. Department of the Interior, Washington, D.C., under Contract 140E0119C0003.