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| Fig. 1: View of a typical offshore wind turbine anchored to the seabed. (Source: Wikimedia Commons) |
Harnessing the energy of the wind has been practiced for centuries. From using the strong ocean breeze to sail the seas or using the wind to pump water, humans have utilized this abundant resource for many services. In recent years, there has been a lot of push for using wind to generate electricity to meet the climate change goals set by many countries.
Wind energy is a natural, renewable resource which means exploiting it produces no direct emissions of greenhouse gases that contribute to global climate change. As a natural resource, there is no fear of running out of the "fuel" like there is with fossil fuels like oil and gas. However, the wind's undulations in speed, shear, and gusts make it a variable energy source, making it less reliable than conventional fossil fuels.
Wind turbines are the most common way the energy in wind is extracted. They are used to generate electricity for customers nearby. A conventional wind turbine stands 80-120 meters (260-400 feet) high, with blades spinning a rotor that produces electricity via a generator. This form of energy supplied the world about 1% of its total energy consumption in 2021 and just over 6% of its electricity generation. [1] Needless to say, wind energy contributes to a significant portion of the world's energy needs.
Conventional wind farms are either built onshore or offshore. Diving deeper into offshore wind will highlight the differences between these two. Fig. 1 provides a visual of what a typical offshore wind turbine looks like. Wind farms can have up to around 50 wind turbines in one area. The European Union has set its sights on having 60 GW of offshore wind power and 300 GW of onshore by 2030. [2] As governments hope to expel the use of fossil fuels from their energy mix, wind energy has a huge potential role in filling that gap. The total capacity of offshore wind from the 27 European Union countries (EU-27), plus the United Kingdom, is around 27 GW as of 2021. [3,4] The United Kingdom makes up about 40% of that. The EU's benchmark for offshore wind by 2030 is about a 550% increase in offshore power. [3]
As mentioned previously, wind energy is not constant. Turbines are not constantly on, meaning their electricity supply is intermittent. A way to illustrate this is through capacity factors, which is a numerical way to represent how often wind turbines, or other energy plants, run at max capacity. Nuclear power plants run at capacity factors of around 90% whereas solar PV is roughly 25% due to the variability in sunshine throughout the day.
For the EU-27 countries, offshore wind turbines had an average capacity factor of 35% in 2021. [3] While this number may seem low, it is 12% higher than onshore turbines. Offshore wind typically has much less variability than onshore winds ergo, allowing turbines to produce more electricity per turbine. [5] When wind turbines do not produce enough electricity to meet minimum demand, they are usually shut down, and a different source has to step in. When wind generation is too high, the energy is curtailed because there is not enough demand on the customer side. While this proves to be a great advantage of offshore wind turbines, it is certainly not the only one.
The power output of a wind turbine is one of the major drivers of wind energy developments. They have a large power output per wind turbine. Offshore winds are typically slightly stronger than onshore winds, meaning the average velocity value is higher. [5] This small change in velocity yields a sizable increase in power. Moreover, offshore wind turbine blades are typically larger, meaning the diameter is greater, and thus the power increases even more. Ultimately, these two factors contribute substantially to why offshore wind projects are attractive.
Offshore conditions seem unfavorable to onshore. Builders anchor turbines into the ocean floor, dealing with undulating ocean waves, miles out from shore. However, technologies of other offshore practices are used to excel in the construction and development of offshore wind. For example, Norweigan offshore oil and gas technology has been used in offshore wind turbine construction. [6] Through this exchange of knowledge and technology, the offshore wind industry does not have to reinvent the wheel. Ultimately, this relationship explains why the biggest players in the offshore wind game (United Kingdom, Germany, Denmark) are home to historical offshore oil drilling practices.
Typically, offshore wind projects are constructed within two years. [7] To make projects happen, offshore wind farms need to prove economical. One of the many ways that projects can become too expensive for investors is if they take a long time to construct. While construction takes about two years, it can take up to 9 years for offshore wind projects to be permitted. [7] Permits are given by governing bodies that own the seabed adjacent to its land. The permitting process involves obtaining the necessary approvals, licenses, and environmental clearances from regulatory authorities before a project can proceed. All of this takes money and commitment. But, there are certain methods to fast-track this to speed up development, which are common in the largest offshore wind countries. For example, Denmark utilizes an open-door policy to incentivize quicker development, meaning developers make money faster. In determining feasible sites, the proximity to customers, quality of wind resources, and efficiencies in the supply chain promise greater economic potential. [5] Ultimately, this results in the North Sea having some of the highest potential for developing offshore wind. [5]
Offshore wind will play a crucial role in the future energy fleet. It utilizes an abundant energy source. Furthermore, as new offshore wind technologies improve and reach capacity factors increase, there will be a high reliance on this technology in the future. According to the IEA, new offshore wind turbines are reaching capacity factors similar to those of coal and natural gas power plants, which will increase its use even more. [5] Despite their high upfront costs, offshore wind is an effective way to generate renewable electricity and meet the demand of many coastal communities. The 27 GW of European offshore wind will feel fractional to what the future will bring.
© Michael Nazari. The author warrants that the work is the author's own and that Stanford University provided no input other than typesetting and referencing guidelines. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
[1] "BP Statistical Review of World Energy 2022," British Petroleum, June 2022.
[2] "An EU Strategy to Harness the Potential of Offshore Renewable Energy for a Climate Neutral Future," European Commission, COM(2020) 741, November 2020.
[3] G. Costanza et al., "Report 2022: European Commission and WindEurope," International Energy Agency, 2022.
[4] S. Wyatt, "Report 2021: United Kingdom," International Energy Agency, 2021.
[5] "Offshore Wind Outlook 2019," International Energy Egancy, 2019.
[6] T. Mäkitie et al., "Established Sectors Expediting Clean Technolog Industies? The Norwegian Oil and Gas Sector's Influence on Offshore Wind Power," J. Clean. Prod. 1778, 813 (2018).
[7] R. Williams and F. Zhao, "Global Offshore Wind Report 2023," Global Wind Energy Council, August 2023.
