In Europe, offshore wind turbines have become an accepted technology for producing energy. Although offshore wind is not yet used in Canada and the U.S., America’s first offshore wind farm, Cape Wind in Nantucket Sound, Mass., is planned for 2014.
Offshore wind turbines are typically mounted on monopile foundations, large steel tubes with a diameter of four to seven metres and around 50 metres long, which are then hammered into the soil with large hydraulic hammers. While effective, this installation technology has some significant drawbacks. Because the turbines tend to get bigger and are installed in ever-deeper water, the monopiles need to get bigger, which in turn demands the ram and anvil to be bigger and heavier. Global production capacity for exceptionally large parts such as these is limited and the prices are high.
The use of conventional hydraulic hammers, which create a high peak force within a short time span, also poses significant ecological concerns with regards to marine life. As a result, their use has been restricted in many countries, although the type of legislation varies per country. In Germany, for example, there is a strict norm that must be met, while in The Netherlands, there are seasonal restrictions, permitting pile driving only half of the year. In general, the current trend in Europe is legislation getting stricter.
Worldwide, most countries have general legislation on the protection of wildlife. In Canada, there is the Species at Risk Act, where the mitigation measures to be applied are defined per project in the permit by the legislator, usually after an ecological impact study.
Triggered by the problems encountered with conventional offshore pile driving technology, Jasper Winkes, M.Sc., and his business partner, Bart Genuit, M.Sc., were determined to invent a better way. The two men form the management team of Fistuca BV, a young company based in The Netherlands. The company was founded in 2008 by Winkes as a spin-off from the faculty of Mechanical Engineering at the Eindhoven University of Technology (TU/e) and is developing innovative solutions for the foundation industry. Genuit, a graduate from TU/e in 2011, has been with the company since its inception.
Both men bring their own unique perspective and expertise to the business. Winkes’ specialties include combustion, mechanical design, creative thinking and managing technical innovations; Genuit’s focus includes dynamic modeling, control design, software engineering and data analysis.
Understanding BLUE Piling Technology
In 2011, under the direction of Winkes and Genuit, Fistuca BV invented BLUE Piling Technology (patented), a revolutionary new technology aimed at reducing both the costs and emitted noise of piling offshore foundations.
“Hydraulic hammers make use of a steel ram, which is dropped onto an anvil resting on the pile, creating a force impulse that drives the pile,” said Winkes. “To reduce the underwater noise, complicated measures need to be taken to lower it to acceptable levels for sea life, significantly increasing the costs of installation. That cost is naturally passed on to the end user, making it an expensive process.”
Instead of a steel ram, BLUE Piling Technology uses a large water column inside a steel tube. This water column is supported by a horizontal steel plate, and on this plate, a combustion chamber is placed. 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,” explained Winkes. “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 results in more soil penetration per blow and lower noise emissions.”
BLUE Piling Technology can be applied in multiple ways; it can be used for jacket piles as well as (XL) monopiles, allowing for more silent, cost-effective and faster installation of piles. Even concrete piles are considered a serious option. Moreover, BLUE Piling Technology is well scalable, so there are virtually no limits to the amount of energy and force that can be delivered.
“In August 2013, a consortium of Fistuca BV, Van Oord and TNO performed a series of successful tests at a shipyard of Van Oord in Zuilichem, The Netherlands,” said Winkes. “The tests were done next to the river Waal, where two piles were driven from the quayside into the riverbed. These tests gave us more insight into the pile driving properties and underwater noise emissions of the technology.”
During the tests in Zuilichem, one open-ended pile of 2.2-metre diameter and one closed-ended pile of 0.7-metre diameter were driven, while the driving parameters and underwater noise emissions were measured.
The pile driving analysis was performed using the Profound PDA/DLT-system, consisting of two sets of combined strain and acceleration sensors. The water pressure in the column near the bottom of the support plate was measured using pressure transducers. Acoustic measurements were performed using hydrophones. First results indicate a significant sound reduction of over 25 decibels, which means that BLUE Piling will most likely comply with even the strictest regulations offshore. In this case, expensive noise mitigation measures would no longer be required.
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 BV, Van Oord OWP and TNO. In the coming months, Fistuca BV will further develop and test this technology to bring it onto the market in 2015.
For more information, including a video of the test results, visit www.fistuca.com. 