Offshore wind power in the Baltic and North Seas is supplying more and more households with climate-neutral electricity. What is an offshore wind farm? The following article provides a definition and explanation of how offshore wind power works, what it costs and what effects this type of energy generation has.
What is offshore wind power? While hydrogen fuel cells generate electricity from hydrogen, offshore wind power generates electricity from kinetic energy. What is the difference between offshore and onshore? The term offshore wind power refers to electricity generated by wind turbines offshore, which means at sea; onshore wind power generates electricity from wind on land. Offshore wind farms – that is, clusters of several wind turbines in close proximity to each other – offer significant advantages over comparable turbines on land. Because wind speeds at sea are much higher and more consistent, wind farms there produce about twice as much electricity as those on land.[1] Thus, a comparison of the full load hours of offshore wind power shows that wind turbines on the high seas achieve up to 4,500 full load hours per year, while turbines in inland Germany record much fewer full load hours.[2] Thus, offshore wind turbines prove to be particularly reliable electricity generators in the field of renewable energies. What is offshore wind power installed for? Offshore wind power makes a decisive contribution to the energy transition in Germany, i.e. the switch from fossil fuels and nuclear power to renewable energies. The development and expansion of offshore wind power off the coasts of Germany is being driven by the Offshore Wind Energy Foundation (Stiftung der deutschen Wirtschaft zur Nutzung und Erforschung der Windenergie auf See). This was founded in 2005 on the initiative of German offshore companies and in cooperation with the German Federal Ministry for the Environment."[1]
"What are the advantages of offshore wind power? Offshore wind power generates environmentally friendly electricity more than 90 percent of the year, making it a highly reliable energy producer. For example, offshore turbines in the North Sea and Baltic Sea produced about 18 terawatt hours of green electricity in 2018. The plan is for them to reach a total capacity of 20 gigawatts by 2030, supplying around 20 million households."[1]
In addition to its high efficiency, offshore wind power brings another major advantage: the electricity generated is based 100 percent on renewable energies. Offshore wind power is therefore applied environmental protection. In contrast to the use of fossil fuels such as oil and gas and coal, the production of electricity from wind power does not release any climate-damaging CO2.[1]
"How does an offshore wind turbine work? Whether offshore or onshore, wind turbines convert wind energy, or the kinetic energy it contains, into electrical energy. In a nutshell, this means that when the wind’s current acts on the wind turbine’s rotor blades, they begin to rotate. As soon as the rotational energy is transferred to the generator, the latter converts it into electric current. If the electricity is from offshore wind power, it is delivered to the coast via submarine cables and fed into the power grid there."[3]
The interaction of several important components is essential for the function of an offshore wind turbine. The rotor blades, for example, are made of glass fiber-reinforced composite material and have a high aerodynamic efficiency. The material ensures that the blades are light on the one hand and sufficiently strong on the other. The rotor blades are attached to the machine house, the so-called "nacelle". This is where all the mechanical as well as electrotechnical elements are gathered that serve to convert the kinetic energy into electricity.
The nacelle can be rotated so that it can automatically align itself according to the respective wind direction. The rotor blades can also be adjusted (blade pitch angle). In this way, you can actively influence the air inflow from the computer – and stop the turbine if necessary by turning the blades out of the wind.
The heart of every offshore wind turbine is the generator driven by the rotor blades. If it is directly connected to the power grid or not depends on the type of turbine. Most modern turbines are connected to the power grid by means of a full converter. In this case, the electricity that is produced does not flow directly from the generator to the power grid, but first through the inverter.
Before the generated energy is fed into the power grid, it must also be brought up to medium voltage. This important step is performed by a medium-voltage transformer. It transforms the energy produced, which has a voltage of between 400 and 1000 volts, to medium voltage, i.e. 10 to 30 kilovolts. The power is then fed into the public power grid.[4]
"How much does an offshore wind turbine cost? Compared to onshore wind farms, offshore wind power is extremely cost-intensive. This is already evident from the costs incurred for the planning and construction of the turbines alone. For example, the investment volume for an offshore wind farm that produces between 300 and 400 megawatts of electricity per year is more than 1 billion euros. However, since the offshore wind power industry is still relatively young, experts believe that the cost of building and operating offshore wind power, and thus offshore electricity, will fall rapidly in the coming years due to new technology."
Like all renewable energies, offshore wind power is subsidized by the Renewable Energy Sources Act (EEG). Based on this law, grid operators are obliged to purchase electricity from offshore wind power. Until 2016, the law also provided for a fixed compensation rate, which gave operators as well as investors more planning security. The fixed compensation rate ensured that the costs for offshore wind power calculated over 20 years were in the midfield of renewable energies. Since 2017, however, offshore wind operators have had to manage without a fixed feed-in tariff. Instead, the level of support is now measured by competitive tenders.[1]
"What are the impacts of an offshore wind farm? Environmental protection organizations complain that the expansion of offshore wind power has negative consequences for marine nature. The main impact on the North Sea and Baltic Sea is caused by construction and the associated underwater noise. During the construction phase, the pile driving of the foundations in particular becomes a noise problem. But the operation and maintenance of offshore wind power can also have harmful effects on fish and marine mammals as well as birds. The noise drives animals out of their habitats and can even injure them. The migration routes of migratory birds are cut by the large turbines, and resting and feeding places are destroyed. In addition, seabirds repeatedly collide with the rotor blades of the turbines. All of these problems associated with offshore wind power put additional strain on the already overfished and polluted oceans. In addition, there are the impacts of other industrial activities, most notably shipping and oil and gas extraction."[5]
In order to prevent this development, the topic of environmental protection is increasingly coming into focus in the context of the construction and expansion of offshore wind power. Thus, offshore wind power operators are already investing large sums in the development of sustainable materials and the ecological design of production processes. In addition, offshore farms must also comply with various, very strict legal requirements for environmental protection and the protection of marine life. Among other things, compliance with these regulations plays a role in the approval process for offshore wind farms. For example, operators are required to submit comprehensive concepts for noise protection and to take measures to protect marine mammals, which are protected species.[1]
Offshore wind power refers to electricity produced by wind turbines offshore, including in large wind farms. It is indeed very expensive to build and operate wind turbines at sea. However, offshore plants offer the advantage that the wind speed there is much higher than on land. The achieved full load hours of offshore wind power are therefore twice as high. Disadvantages of offshore wind power are evident in the area of environmental protection. Marine mammals and fish, as well as seabirds and migratory birds, suffer from the destruction of their habitat and the noise pollution caused by the construction and operation of the turbines.
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