Introducing the Onshore Monopile Foundation
As the number of locations suitable for development become more limited, onshore wind parks are being installed in more and more difficult soil conditions. At the same time, developers are being challenged to reduce costs. Innovative foundation concepts are the enabler to develop new locations, improve economics and meet local low-carbon energy objectives. To meet these challenges, Ballast Nedam has developed a unique onshore monopile foundation.
What is the Onshore Monopile?
The onshore monopile is similar to the offshore monopile foundation and consists of a single foundation pile on which the turbine can be directly installed. Main advantages include the installation in more wet and unstable soils, which are less suitable for a traditional foundation, and a significant reduction in installation time. Moreover during construction, installation and transportation, movements are reduced. And the foundation is fully re-usable at the end of its lifetime, lowering the overall carbon footprint. The onshore monopile has been successfully introduced on twelve turbines of Windpark Maasvlakte 2: an industry first.Limitations of a Traditional Foundation
Traditional onshore wind turbine foundations consist of multiple foundation piles and concrete slab which is poured in situ. While this is a proven and cost-effective technique, its application is significantly more difficult in wet and unstable soil conditions. Not only does the concrete foundation require drainage of the construction area, a significant amount of concrete and piling may be required to give the foundation sufficient stability. The monopile has excellent soil interaction characteristics and in this respect the monopile has the potential to open the door to new areas of development.Benefits of an Onshore Monopile
The installation of a monopile foundation only takes less than a day and can be installed by the same crane used to install the turbine itself. Careful attention is required for the logistics as the pre-fabricated monopile is moved from the factory to the construction site, but also to the efficiency of all the lifting operations of turbines and foundations on the development site. Typically a 6 megawatt turbine would require a 4.5 meter diameter pile with a length of 25-30 meters, similar in sizing to turbine tower elements and therefore easy to transport. For larger wind farms in particular, the time it takes to bring power to market can also be reduced to improve the economics.CO2 Emission Level of Onshore Monopile Foundation
Environmental benefits of a monopile over a traditional foundation are substantial. CO2 emissions for the production of a steel monopile versus a concrete foundation are lower. And the reduction of transportation and installation movements cuts a lot of local emissions, not only of gasses but also noise and vibration. Considering the diameters for shallow foundations of 6 megawatt turbines are reaching 25-30 meters, the footprint in the landscape can be significantly reduced. Furthermore, at the end of its life the monopile foundation can be reused or is otherwise fully recyclable, making it a much greener alternative to traditional foundations.Improved total lifecycle cost
The onshore monopile concept has received a DNV GL Statement of Compliance and has already been successfully installed at Windpark Maasvlakte 2. Feasibility and economics of the onshore monopile can be easily assessed for each project by Ballast Nedam. In most reported cases, the initial cost of an onshore monopile is close to that of a concrete foundation, provided the logistics of the chosen foundation are attractive. With a lower installation time and full recyclability at the end of its lifetime, the balance of total lifecycle costs swing in favour of the onshore monopile.Source: Introducing the Onshore Monopile Foundation
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