Dong Energy and its partner ESG, a provider of testing and inspection services have completed test of wind turbines piles, and found that new pile design can significantly reduce the cost of offshore wind projects.

pile test

As part of the testing, the partners used 28 piles of three different diameters on two different onshore sites in Cowden, England and in Dunkirk, France, for the development of new design methods for offshore wind farms.

The piles supplied by Bladt and Dansteel were tested using fibre optic strain gauges installed by Marmota Industries in order to assess the static monotonic and the response under cyclic lateral loading by pulling them sideways into the soil until failure.

The testing, which was carried out under the Pile Soil Analysis (PISA) project, involved evaluation and validation of new design method developed by the PISA academic working group led by Oxford University and including Imperial College London and University College Dublin.

PISA R&D manager Jesper Skov Gretlund said: "If the thickness or length of the steel piles can be reduced by even a small fraction, the saving in cost is quite considerable since smaller construction vessels can be used and larger turbines constructed.

"The next challenge is to analyse all of the data collected in order to refine our methods and apply these findings to our foundation designs."

ESG project director Steve Turner said: "With the largest test, we were simultaneously monitoring more than 250 different precision instruments, whilst applying a load greater than the weight of 37 London double decker busses."

Over the next six months, the team will assess the data collected during the tests to confirm the new design methods.

Dong Energy lead Geotechnical engineer Alastair Muir Wood said: "The results indicate that in these site conditions there may be opportunities for savings identified by reducing the quantity of steel in the foundation. In other words, there’s a savings potential, that will contribute to reducing the cost of electricity."

PISA project was undertaken by industry DONG Energy-led group comprising EDF, RWE, Statoil, Statkraft, SSE, Scottish Power, Vattenfall, Alstom and Van Oord.

Image: About 28 piles were tested at two different onshore sites in Cowden, England and in Dunkirk, France. Photo: courtesy of Dong Energy.