page_title: Offshore wind power
section_title: Fixed foundation offshore wind turbines
hierarchical_section_title: Offshore wind power / Types of offshore wind turbines / Fixed foundation offshore wind turbines
caption_attribution_description: English: Progression of expected wind turbine evolution to deeper water. Produced by National Renewable Energy Laboratory.
context_page_description: Offshore wind power or offshore wind energy is the use of wind farms constructed in bodies of water, usually in the ocean, to harvest wind energy to generate electricity. Higher wind speeds are available offshore compared to on land, so offshore wind power’s electricity generation is higher per amount of capacity installed, and NIMBY opposition to construction is usually much weaker.
  Unlike the typical use of the term "offshore" in the marine industry, offshore wind power includes inshore water areas such as lakes, fjords and sheltered coastal areas as well as deeper-water areas. Most offshore wind farms employ fixed-foundation wind turbines in relatively shallow water. As of 2020, floating wind turbines for deeper waters are in the early phase of development and deployment.
  At the end of 2018, the total worldwide offshore wind power capacity was 23.1 gigawatt.
  All the largest offshore wind farms are currently in northern Europe, especially in the United Kingdom and Germany, which together account for over two-thirds of the total offshore wind power installed worldwide.
context_section_description: Almost all currently operating offshore wind farms employ fixed foundation turbines, with the exception of a few pilot projects.
  Fixed foundation offshore wind turbines have fixed foundations underwater, and are installed in relatively shallow waters of up to 50–60 m.
  Types of underwater structures include monopile, tripod, and jacketed, with various foundations at the sea floor including monopile or multiple piles, gravity base, and caissons.
  Offshore turbines require different types of bases for stability, according to the depth of water. 
  To date a number of different solutions exist:
  Most foundations are monopile (single column) base, six meters in diameter, is used in waters up to 30 meters deep.
  Conventional steel jacket structures, as used in the oil and gas industry, in water 20–80 m deep.
  Gravity base structures, for use at exposed sites in water 20–80 m deep.
  Tripod piled structures, in water 20–80 m deep.
  Tripod suction caisson structures, in water 20–80 m deep.
  Monopiles up to 11 m diameter at 2,000 tonnes can be made, but the largest so far are 1,300 tons which is below the 1,500 tonnes limit of some crane vessels. 
  The other turbine components are much smaller.
  The tripod pile substructure system is a new concept developed to reach deeper waters than with the shallow water systems, up to 60 m. This technology consists of three monopiles linked together through a joint piece at the top. The main advantage of this solution is the simplicity of the installation, which is done by installing three monopiles and then adding the upper joint.
  Tripod is an innovative concept that consists on a central pipe that lies on a tripod tubular frame configuration at its bottom part. This uses three small seabed driven piles at each leg of the tripod to link it to the seabed. The main advantage of the tripod system is that it has a larger base, which decreases its risk of getting overturned. Due to the large dimensions the installation process is more difficult and increases the cost.
  A steel jacket structure comes from an adaptation to the offshore wind industry of concepts that have been in use in the oil and gas industry for decades. Their main advantage lies in the possibility of reaching higher depths (up to 80m). Their main limitations are due to the high construction and installation costs.
caption: Progression of expected wind turbine evolution to deeper water
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