This article discusses offshore wind turbine working principle, locations, and advantages, as outlined below;
How Offshore Wind Turbines Work
Offshore wind turbines work in three basic steps, which are; energy capture, conversion, and electricity generation. These are the same steps that comprise the working principle of onshore wind turbines.
1). Energy Capture (in explanation of How Offshore Wind Turbines Work)
Energy capture is the first step in the working process/principle of offshore wind turbines.
Offshore wind turbines capture energy using their blades, which have an aerodynamic geometry enabling them to achieve maximum contact with wind within their reach.
Because of the relatively-powerful wind currents and surplus wind supply in offshore locations, it is generally necessary to provide firm structural support for offshore wind turbines so as to prevent their damage and/or collapse under the pressure of ocean winds, or wave energy.
Offshore wind turbines are anchored either using rigid foundations (in relatively-shallow locations), or heavy ballasts (for floating systems in deep locations) .
This means that offshore wind turbines stay in place as a result of foundation or ballast-based structural support, which keeps them upright and resistant to aerodynamic or fluid pressure from their surroundings.
Offshore wind turbines are not better than onshore wind turbines in terms of basic design and functionality, but they are often developed with prioritization of structural resilience and efficient wind capture, because of their exposure to stronger and more consistent winds than those on land.
2). Energy Conversion
Energy conversion in wind turbines refers to the transformation of energy from one form to another.
It is important to note that electricity generation is not essentially the same as energy conversion, since electricity is a stream of charges produced by electromagnetic processes, and not a form of energy. However, it is still common to find electricity generation being discussed as a form of energy conversion in many studies.
In offshore wind turbines, the main process of energy conversion that occurs is that which transforms wind kinetic energy to mechanical energy .
This conversion is a relatively simple process, and occurs when wind energy that is captured by the blades of the turbine, induce rotation, that extends from the blades to the rest of the turbine rotor assembly, which includes metallic shafts.
The conversion efficiency of a wind turbine is a measure of how much energy is successfully converted from its original form to another; and is usually calculated by multiplying the ration of energy lost to energy converted, by 100.
An offshore wind turbine is fairly efficient, with an average conversion efficiency of around 30%, based on a 20-40% range.
While this may seem small, it is important to evaluate it with consideration of the dominant presence of frictional forces in the turbine rotor assembly, which cause a significant amount of waste energy to be released or lost as heat.
Efforts to improve the energy efficiency of all types of wind turbines have remained a prominent theme of wind and renewable energy innovation for decades so far.
3). Electricity Generation (in explanation of How Offshore Wind Turbines Work)
Offshore wind turbines generate electricity from wind-derived mechanical energy, through the electromagnetic effect; whereby a rotating conductor in an electromagnetic field activates a generator to produce a continuous stream of charges known as electricity.
The potential of electricity generation by offshore wind turbines, depends on the size and design of these turbines.
Offshore wind turbine size may range from 100-250 meters rotor diameter, while tower height and blade sweep area may reach 300 meters and 20,000 square meters respectively. These values are based on a broad range of turbine dimensions across various locations and years of development.
Modern offshore wind energy research and development have focused on the possibility of minimizing turbine size while maximizing efficiency.
The amount of electrical power which an offshore wind turbine can produce is between 2.0 and 3.6 MW, based on a broad range of values across various locations and years of development.
After electricity has been generated by offshore wind turbines, it is usually converted from direct current (DC) form to alternating (AC) form, using an in-built Voltage Source Converter (VSC) that operates similar to a power inverter .
Offshore wind turbines are connected to an electricity distribution system using high-voltage cables that are often anchored to the seafloor.
The same cable-connection method is used to connect offshore wind turbines to each other in wind farms or hybrid systems.
Offshore Wind Turbine Locations
Offshore wind turbine locations in the world, by country, include China, Denmark, Germany, Netherlands, Portugal, United Kingdom, and United States (as of 2023).
The country with the most offshore wind turbines as of 2023 is China, with an overall installed capacity of approximately 20.0 GW.
However, the United Kingdom has the largest offshore wind turbine in the world.
Advantages of Offshore Wind Turbines
Advantages of offshore wind turbines are;
1). Minimal environmental impact
2). Access to large amounts of wind energy
4). Job creation
Offshore wind turbines work by;
1. Energy Capture
2. Energy Conversion
3. Electricity Generation
Advantages of offshore wind turbines are; minimal environmental impact, large amounts of wind energy, flexible usage, job creation, and role in energy transition.
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2). Pan, L.; Shao, C. (2020). "Wind energy conversion systems analysis of PMSG on offshore wind turbine using improved SMC and Extended State Observer." Renewable Energy 161(1). Available at: https://doi.org/10.1016/j.renene.2020.06.057. (Accessed 6 February 2023).
3). Tawfiq, K. B.; Mansour, A. S.; Ramadan, H. S. M.; Becherif, M.; El-kholy, E. (2019). "Wind Energy Conversion System Topologies and Converters: Comparative Review." Energy Procedia 162(2019):38-47. Available at: https://doi.org/10.1016/j.egypro.2019.04.005. (Accessed 7 February 2023).