World first: DEME’s sea drill for windmill foundations
DEME, the Belgian world leader specialized in dredging operations, has developed a special kind of sea drill, together with the German construction expert Herrenknacht. A world first. The company usually uses a giant hammer to anchor the foundations of an offshore wind farm into the sea-floor.
For some locations, however, like the French wind farm in Saint-Nazaire, for which construction works will start in 2021, this technique is not appropriate.
DEME has to install 80 so-called ‘XL monopiles’ as the basement for the wind farm 12 to 20 kilometer of the coast of the Guérande peninsula. Usually, those XL piles have a 7-meter diameter, compared to the ‘normal’ ones of 4 meter. Besides, the subsoil is too rocky to be able to hammer those piles into the ground.
That is precisely why the Belgian dredging company developed a particular drilling machine. “A world first,” confirms Vicky Cosemans, spokesperson for DEME. The new drill is not only important to realize the French project, but also for other similar projects in the long run. The wind farm in France has to be ready by the end of 2022, and DEME will be responsible for the design, production, transport, and installation of the foundations.
Ecological and economic advantages
The new technology allows the construction of larger foundations and larger wind farms. “Installing drilled XL-monopiles is a new step forward in the offshore wind industry,” says Bart De Poorter, general director of DEME Offshore. “With this innovative solution, developed together with Herrenknecht, we ensure that the installation is performed safely and efficiently in challenging marine conditions.”
The drill chuck that is fixed to the DEME installation ship Innovation offers more advantages to the company. “The offshore drilling of foundations enables a mechanical installation of mono pillars, which offers ecological and economical advantages compared to traditional methods,” says Herrenknecht.
The German specialist already experimented in 1977 with a technology to drill horizontally into solid surfaces for the excavation of tunnels. DEME will apply this technique vertically. DEME also finances the initiative; the investment amount, however, is kept secret.
DEME has a 140-year history as a dredging specialist, and since 2000, the company focuses on sustainable energy. Meanwhile, DEME realized 45 offshore wind farms in Europe and China. End January, the company installed its 2 000th wind turbine.
In 2018, 46% of DEME’s turnover (€2,65 billion) came from renewable energy projects. DEME Offshore, a new cluster of some of DEME’s subsidiaries, realized a turnover of €895,5 million while dredging activities respresented €832,9 million.