DONG Energy has completed one of the most comprehensive pile-testing campaigns ever, and based on initial findings, the results show that the cost of offshore wind can be greatly reduced.
DONG Energy and ESG, a U.K.-based testing and inspection services provider, tested 28 piles on two different onshore sites in order to assist the development of new design methods for offshore wind farms. The testing was undertaken by the Program International Student Assessment (PISA) and was performed to assess and validate a new design method developed by the PISA academic working group led by Oxford University and including Imperial College London and University College Dublin.
The academic working group supervised the testing on-site, as each of the 28 piles were pulled sideways into the soil until failure.
According to DONG Energy, the testing took place in Cowden, England, and in Dunkirk, France, because the soil conditions at the sites mirror those found in typical surface soil conditions found in much of the North Sea. Further, both sites have previously been used for pile-testing activities, mostly targeting oil and gas engineering, meaning that a rich amount of field and laboratory soil data is already available.
Bladt Industries and DanSteel supplied piles of three different diameters for the tests; the piles with a diameter of two meters are some of the largest ever tested. During testing, other instrumentation was used, including fiber-optic strain gauges installed by Marmota Industries. In total, 28 tests were conducted primarily investigating the static monotonic but also the response under cyclic lateral loading.
The academic working group now has six months to analyze the data collected and use it to confirm the new design methods. The final report is due to be delivered to the project partners in January 2016.