A consortium of Fistuca, Van Oord and TNO has performed a series of successful tests of BLUE Piling Technology (patented), an innovative technology to drive large piles offshore.
At a shipyard of Van Oord in Zuilichem, The Netherlands, next to the river Waal, two piles where driven from the quayside into the riverbed. The tests give more insight into the pile driving properties and underwater noise emissions of the technology.
The technology was invented by Fistuca, a spin-off of the Eindhoven University of Technology, and uses water to drive the piles, yielding it considerably more silent as well as more cost-effective than conventional techniques.
Offshore wind turbines are typically mounted on monopile foundations, large steel tubes with a diameter of 4-7m and around 50m in length. They are hammered in the soil with large hydraulic hammers using steel rams. This installation technology has some significant drawbacks.
The hammers are expensive to rent and the underwater noise caused by ramming piles in the soil raises environmental concerns with regard to sea life such as fish and dolphins. The use of this type of hammer is therefore restricted in many countries.
BLUE Piling Technology works as follows: a pipe is closed off at the lower end by a steel plate. On which a combustion chamber is placed. The pipe is then filled with water, creating a large water column. A gas mixture is injected into the combustion chamber and then ignited.
The rapid combustion of the gasses creates an increase in pressure, since the high mass of the water keeps the gasses from expanding freely. The pressure increase pushes the water upwards and simultaneously drives the pile downwards, into the soil.
When the water falls down again on the support plate, it creates a second force pulse, driving the pile even deeper. This cycle is repeated until the pile reaches its desired depth.
Because the mass of the water column is much larger than a conventional steel ram, the force pulse of BLUE Piling Technology is much longer. This will result in more soil penetration per blow and lower noise emissions.
During the tests in Zuilichem, one open-ended pile of 2.2m diameter and one closed-ended pile of 0.7m diameter were driven, while the driving parameters and underwater noise emissions were measured. The results will be presented at the EWEA Offshore conference, held in November 2013, in Frankfurt.
The tests were financially supported by a grant from the Top consortium for Knowledge and Innovation Offshore Wind (TKI-WoZ) of the Dutch government. This grant will be used for further development of the technology in a two-year joint project of Fistuca, Van Oord OWP and TNO. Fistuca plans to bring the technology onto the market in 2015.
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