Offshore Wind Turbine Foundations: Monopile, Jacket, and Tripod
The main drivers of offshore wind power development are onshore site limitations and global targets to expand renewable energy capacity. Thus, there is a high potential for offshore wind power development.
Monopile, jacket, and tripod offshore wind turbine foundations:
Monopile foundations are one of the most used in offshore wind power projects. A monopile foundation is a steel pipe, that is made by circular welding of a steel plate, and it has up to eight meters diameter (Zhang et al. 2016) and 150mm wall thickness (World Steel Association 2012). The length of monopile foundations can be around 60 meters, and they can be driven into a seabed by hydraulic hammers (Zhang et al. 2016).
Monopile foundations are more suitable for soft or semi-soft seabed conditions and offshore sites commonly up to 25 meters in depth (Hau 2013).
The ratio of the diameter to the wall thickness of a monopile structure varies depending on forces. A combination of a higher diameter with a lower wall thickness makes a lighter structure, but it may not survive under the pressure of some forces (Zaaijer 2003).
 |
| Figure 1*: Monopile Offshore Foundation |
*Source Figure 1: Hermans, K. W., Peeringa, J. M., & Stichting Energieonderzoek Centrum Nederland. (2016). Future XL monopile foundation design for a 10 MW wind turbine in deep water.
Jacket Foundation
Jacket foundations have a similar design to lattice towers. A jacket foundation contains a squared network of steel rods (World Steel Association 2012). A jacket foundation is a rigid structure with a good ratio of stiffness to weight (Hau 2013).
Jacket foundations are the second most used offshore foundations in wind power projects, and jacket foundations are suitable for a water depth of 30 to 80 meters (Zhang et al. 2016).
 |
| Figure 2*: Jacket Foundation Structure |
*Source Figure 2: Hau, E., & ebrary, I. (2013;2011;). Wind turbines: Fundamentals, technologies, application, economics (3rd, translat;3. Aufl.;3rd 2013; ed.). New York: Springer. doi:10.1007/978-3-642-27151-9
Tripod foundation
A tripod foundation is a tube with three bottom rods. A tripod foundation attached a seabed with its smaller diameter piles (World Steel Association 2012). It can be driven into a sea bottom up to 20 meters depending on the soil structure (Hau 2013). A tripod foundation has a high resistance to wave and current loads, and it is suitable for a water depth of 25 to 50 meters (Zhang et al. 2016). Tripod foundations are not cost-competitive in the market (Hau 2013).
 |
| Figure 3*: Tripod Foundation |
Source Figure 3: Zhang, J., Fowai, I. & Sun, K., 2016. A GLANCE AT OFFSHORE WIND TURBINE FOUNDATION STRUCTURES. HRČAK, 67(2), pp.101–113.
References
Hau, E., & ebrary, I. (2013;2011;). Wind turbines: Fundamentals, technologies, application, economics (3rd, translat;3. Aufl.;3rd 2013; ed.). New York: Springer. doi:10.1007/978-3-642-27151-9
Hermans, K. W., Peeringa, J. M., & Stichting Energieonderzoek Centrum Nederland. (2016). Future XL monopile foundation design for a 10 MW wind turbine in deep water.
World Steel Association, 2012. Steel solutions in the green economy Wind turbines.
Zaaijer, M.B., 2003. Comparison of monopile, tripod, suction bucket and gravity base design for a 6 MW turbine. Delft University of Technology, Section Wind Energy.
Zhang, J., Fowai, I. & Sun, K., 2016. A GLANCE AT OFFSHORE WIND TURBINE FOUNDATION STRUCTURES. HRČAK, 67(2), pp.101–113.