The following questions are directed to Alex Thompson, a communications specialist with the Wind Energy Technologies Office, which is a contractor to the U.S. Department of Energy (DOE.)
Why are wind turbines being built higher?
To capture more energy, since winds generally increase as altitudes increase. The hub height (distance from the ground to the middle of the turbine’s rotor) for utility-scale land-based wind turbines has increased 66 percent since 1998-1999, to about 94 meters (308 feet) in 2021.
Have there been other advances in the past few years?
In addition to taller towers, there has been an increase in blade length, which increases the area that a wind turbine has to capture energy. This also corresponds with a trend to wind turbines with lower specific power. The specific power of a turbine is the ratio of its nameplate-capacity rating to its rotor-swept area.
In layman’s terms, when engineers are designing a turbine in a specific location, they adjust the relationship between the diameter of the blades and the ability of the turbine engine to best capture the varying wind speeds. An efficient and long-lasting turbine will be able to both capture low wind speeds and stay intact during more drastic conditions, such as a hurricane. All else equal, a decrease in specific power will boost capacity factors—which measure how often a turbine is operating at full capacity—because the turbine can produce energy at a wider range of wind speeds.
DOE supports research, and the industry continues to make incremental improvements to wind turbine technologies to increase efficiency and cost effectiveness. One area of recent research is optimizing entire wind plants to maximize electricity production, rather than focusing on each wind turbine individually. DOE is also focusing efforts on research and development for offshore wind, including floating offshore wind for the West Coast.
Through technological advancements, coupled with continued improvements in siting practices and considerations, technologies focused on taller wind turbine towers and larger rotors—currently under development by DOE and its partnering national labs, universities, and private-sector companies—America can more efficiently capture the stronger and more consistent wind resources typically found at greater heights above ground level.
Do the taller heights make wind turbines more practical in areas where they wouldn’t have been feasible in the past?
Advanced wind turbines with taller towers and longer blades allow us to reach stronger, more consistent winds found high above the ground. Larger, more efficient wind turbines create new opportunities for wind energy generation and job growth in places like the southeastern U.S., where wind speeds are generally low close to the ground but much better with increasing height.
Is the cost of the greater height worth the extra power produced?
In general, yes; however, the exact specifics and economics depend on factors including location, technology, wind resources, and the overall electricity generation mix.
Some wind turbines are proposed in Carroll County that would be 650 feet tall. Are there any other turbines in the country onshore that tall?
The sizes you are referring to appear to be tip height or total height (keep in mind some projects report hub height instead.) Onshore, there are about 158 turbines in that height class in the U.S.
Are there tax incentives for making plans for wind developments even if they aren’t ever built?
Tax incentives are available for electricity production and capital expenditures (not planning).
Is there any way to produce wind power without towers so incredibly tall?
Yes, wind turbines are available in a variety of sizes, including many smaller sizes. Because larger machines tend to be more efficient and produce more energy, you would need a larger number of smaller turbines to produce the same amount of electricity. Wind turbines with longer blades and lower specific power can also be more efficient without a commensurate increase in the height of the tower.