Offshore wind turbines have been constantly enlarging in sizes over recent years in order to capture stronger wind energy, where the height has been growing and the blades have been longer, though such development brings numerous challenges, including upgrades in engineering, as well as maritime and foundation facilities.
The largest offshore wind turbine will begin generating power starting from this year. Dogger Bank Wind Farm adopts the Haliade X series by GE, and a Haliade X 14.7MW wind turbine sits at about 260m in height, which is a bit shorter than the Taipei Nan Shan Plaza (272m).
This type of large wind turbines is one of the heroes behind the annually dropping cost of offshore wind power. Large wind turbines have been penetrating into the market at a pace faster than the industry’s expectation. The industry expected in 2018 that the price of offshore wind power would be lowered to below £100/MWh in 2020, though the rapid decrease of cost has promoted developers to promise on selling electricity at below £50/MWh without further subsidization from the government.
Theoretically speaking, as wind turbines constantly grow in height, their longer blades are obviously going to have a larger sweeping area that would capture additional wind and generate more power, however, there are also restrictions at the same time.
The speed of blade tip, in order to avoid corrosion from collision between the blades and rain drops and waves, must be restricted at 90 seconds/m. With the rotor slowing down as wind turbines become taller and blades become longer, the blades must deflect the wind direction at a greater degree so as to generate the same level of power, which would result in wind turbines sustaining additional force that will increase both the weight and cost of wind turbines. Longer blades will become more flexible at the same time, and are unable to fully control the surrounding airstream and prevent blades from colliding with the tower under extreme wind conditions.
The continuous heightening of large wind turbines is not only troubled by issues in production, installation, and operation, but also transportation, where transporting blades and towers from factories to the site, as well as assembling the wind turbines at the site, will be a major challenge. In addition, port infrastructures, giant installation carriers, and cranes, are also challenges at the same time.
Hence, many coastal countries with multiple shallow sea areas and excellent wind farm sites that are suitable for the development of offshore wind power would still need to consider the production chain of wind turbines, port facilities, quantity of installation carriers, and professional technicians.
(Cover photo source: Unsplash)