The number of offshore installations for expanding the use of renewable energy and the construction of coastal infrastructure has grown rapidly in recent years. As a result, demand for economical and environmentally friendly installation technologies for offshore foundations has increased. These are needed for wind turbines, substations, tidal power plants and bridges as well as for harbor infrastructure such as quay walls, breakwaters and jetties.
The newly developed Herrenknecht OFD technology uses a full-face drilling concept and a drive behind the cutterhead to overcome the limits of conventional methods. This applies in particular to difficult ground conditions unsuitable for pile driving and where established pile driving methods would cause critical noise emissions.
The first project to employ the OFD technology is the Saint-Nazaire wind farm off the North Sea coast of France. The Saint-Nazaire offshore wind farm is the first in the world to use mechanized drilling for the construction of large-diameter monopile foundations.
In June 2021 the first mechanized drilling was successfully completed.. In total, 73 monopile foundations have to be excavated in water depths between 12 and 25 meters with a diameter of 7,700 millimeters and with drilling depths of between 6 and 24 meters. As early as May 24, 2022, the crews on the installation ship “Innovation” completed the drilling for the last wind turbine foundation.
Follow-up project
For a second wind farm, OFD is used since May 2024 to drill boreholes for 61 monopiles in the rocky Atlantic seabed between the islands of Noirmoutier and Yeu. Each monopile has a diameter of 7 meters and will serve as the foundation for one of the more than 200-meter-high wind turbines. The new project off Noirmoutier is subject to similarly challenging weather, sea and ground conditions as off St. Nazaire. With water depths of up to 36 meters, the monopiles will be embedded in the rocky seabed. The boreholes are drilled with the machine used already in St. Nazaire, which was completely overhauled by Herrenknecht.
