Wind Turbines Offshore Foundations and Connections to Grid

Abstract

Most offshore wind farms built thus far are based on waters below 30 m deep, either using big diameter steel monopiles or a gravity base. Now, offshore windfarms are starting to be installed in deeper waters and the use of these structures—used for oil and gas like jackets and tripods—is becoming more competitive. Setting aside these calls for direct or fixed foundations, and thinking of water depths beyond 50 m, there is a completely new line of investigation focused on the usage of floating structures; TLP (tension leg platform), Spar (large deep craft cylindrical floating caisson), and semisubmersible are the most studied. We analyze these in detail at the end of this document. Nevertheless, it is foreseen that we must still wait sometime before these solutions, based on floating structures, can become truth from a commercial point of view, due to the higher cost, rather than direct or fixed foundations. In addition, it is more likely that some technical modifications in the wind turbines will have to be implemented to improve their function. Regarding wind farm connections to grid, it can be found from traditional designs such as radial, star or ring. On the other hand, for wind generator modeling, classifications can be established, modeling the wind turbine and modeling the wind farm. Finally, for the wind generator control, the main strategies are: passive stall, active stall, and pitch control; and when it is based on wind generation zone: fixed speed and variable speed. Lastly, the trend is to use strategies based on synchronous machines, as the permanent magnet synchronous generator (PMSG) and the wound rotor synchronous generator (WRSG).

Harnessing the Wind Power of the Ocean with Green Offshore Ammonia

“…In shallow water, which in this study refers to water depths less than 60 m, fixed-bottom wind turbines can be used. There are various types of substructures for fixed-bottom wind turbines, including monopile, gravity base, jacket, tripile, tripod, high-rise pile cap, and suction bucket, where the first four are most commonly used. − Monopile foundations are suitable for water depths less than 15 m, gravity-based foundations are usually constructed for water depths up to 30 m, and for water depths greater than 30 m, jacket-type foundations are required. , …”

“…Almost all existing offshore wind farms have been built in shallow water. The main reason is that for water depths greater than 60 m, we need to construct floating wind turbines, which are less developed and considerably more expensive than their fixed-bottom counterparts. Foundations for floating wind turbines include semisubmersible platforms, tension-leg platforms, and spar-buoy foundations, where 89% of the currently announced floating wind turbine projects intend to use semisubmersible foundations .…”

Entropy Indicators: An Approach for Low-Speed Bearing Diagnosis

“… Offshore wind turbines. ( a ) Wind turbine over a fixed foundation [ 14 ]. ( b ) Floating offshore wind turbine assembly [ 15 ].…”

“…Thus, it is particularly challenging to determine condition monitoring (CM) for this type of bearing because of the circumstances previously described. [14]. (b) Floating offshore wind turbine assembly [15].…”

Environmental Impacts of Global Offshore Wind Energy Development until 2040

“… 29 Moreover, there are few environmental assessments for emerging technologies, like superconducting generators, 30 new fiber technologies 31 in blades, hybrid tower concepts, 32 and spar, and TLP floating foundations. 33 Further, potentially important life cycle phases such as the installation, maintenance, and EoL recycling are not well captured in the typical reference life cycle inventory (LCI) data sets (e.g., ecoinvent 1–3 MW, and National Renewable Energy Laboratory (NREL) 5 MW). 34 Background system changes, such as the energy transition, are also not commonly considered 5 , 7 , 9 , 13 − 15 , 17 , 19 , 20 , 23 , 25 or not sufficiently and transparently described in the literature.…”