Project
The foundation for the wind turbine is built as a steel structure on four piles – a robust solution when an earthquake shakes the subsurface.
Many new offshore wind farms are soon to be constructed in Taiwan and at these latitudes, the turbine foundations must be able to withstand severe earthquakes and yearly typhoons.
When an earthquake shakes Taiwan, the seabed transforms into something resembling quicksand. The island state is located in a typhoon belt and has regular visits from violent wind forces. To build offshore wind turbines, which can withstand this kind of natural phenomena, is brand new in the field of offshore wind and requires special constructions, which ensures that the turbines stand firm – even when a layer of up to twenty metres of seabed is “liquid” and typhoons shake the turbines.
One of the solutions is called a jacket and it is a foundation built like a grid construction of steel resting on four piles. In relation to a foundation with only one pile – a monopile – a jacket is much more robust in relation to the size of foundation at greater depths and specific types of subsurface. A jacket is also used in Europe, for example, in very deep water.
Not only is there speed in the wind in the Taiwan Strait. New powerful winds are also blowing in the development of Taiwan’s energy sector. The island state’s nuclear power plants are to be replaced with, among other things, wind energy, and as the front runner in Asia, Taiwan is developing many wind farms. In one of the parks, NIRAS’ jacket design foundations will form the foundation piles for initially two offshore wind turbines.
NIRAS is behind the so-called detailed design – in other words, a design so detailed that it can be used to manufacture structures at the supplier. There is a comprehensive analysis of wave and current conditions prior to the detail design, as well as designing models of the seabed. If all goes according to plan, the blades on the new offshore wind turbines will rotate and supply power to Taiwan at the end of 2018.
Taiwan’s offshore wind turbines present completely new challenges to the engineers, because they have to cope with earthquakes and typhoons, which the European turbines are not exposed by.
The customer requested NIRAS to take over the detailed design og the two jacket foundations as an experienced consultant was required in order to move the project forward. During the detailed design of the two jacket foundations for the Changhua Off-shore Pilot Project, NIRAS has managed to reduce the seel amount by 462 tons for the 8 piles. The achievement is obtained through excellent cooperation between the client and NIRAS' specialists, covering the fields of geotechnical engineering, seismic engineering, and structural engineering. Using an approximate steel price of 1,500 EUR/tons proceeds steel the saving corresponds to 700,000 EUR corresponding to a significant part of the cost for the detailed design.
