Blowin’ in the Wind*

I recently drove from Northern Oklahoma through Kansas and on to central Colorado on a vacation trip and saw hundreds of wind turbines along the way in Kansas and Colorado.?I started thinking about the wind energy activity in the U.S., and just how much the average person in the country knows about wind energy.

Disclaimer – I am not a wind energy expert, but rather a curious retired engineer/ manager with more than 45 years of experience in the oil and gas midstream space.?I would welcome any suggested additional questions or modifications from those who read this article.

I’ll list the questions I had, and responses I’ve found available via multiple websites and articles from experts in the field:

1.?????How long have windmills and wind turbines been around?

Windmills utilizing sails like those on boats date back as far as the 4th millenia BC. (see HistoryofWindmills.com).?Somewhat reliable windmills were operational in what is now the area between Afghanistan and Iran between the 7th and 9th century AD.?Early windmills at that time were used to either grind grain, or pump water.?The “Smock” mill design (middle photo above), dates back to the mid-17th century in England, and many windmills of this type are still in operation in the Netherlands, where they are used to pump and redistribute water.?Windpumps, like the one shown in the bottom picture above, were quite popular in the 19th and 20th centuries in the U.S., with an estimated 600,000 operational windpumps active in the 1930’s, and current estimates of 60,000 still in service today, primarily on farms and ranches, for pumping water.

?2.?????How big are the current large wind energy turbines?

This illustration is from “The Physics of Wind Turbines” website, referenced below.?Note that the generator for these large turbines is located more than 300 feet above ground, and each blade is more than 160 feet long.?The generator/ gearbox (“Nacelle”) is approximately 30 feet long, which is about the size of an average school bus (25-45 feet).

?3.?????Why do they have 3 blades, and not 4, 5 or 6 like ceiling fans?

Most modern wind turbines used for electric power generation have 3 blades. While increasing the number of blades might increase the power output of the turbine, it would also increase the “drag”, or resistance of the turbine, requiring a higher wind speed to get the turbine to start turning.?Most modern turbines will begin turning at wind speeds of 5-9 mph, and current technology will shut down the turbine by “feathering” the blades at wind speeds above 50-55 mph. (see “The Physics of Wind Turbines” web page at The Physics of Wind Turbines - Home (uaf.edu). ??According to the web page “Nature’s Generator” Solar and Wind Power (naturesgenerator.com), the current large wind turbines spin at 13 to 20 revolutions per minute, which translates to a moving tip speed at the end of each blade of up to 180 miles per hour.

4.?????How much electrical power do they generate?

Modern onshore wind turbines are designed to generate 2 to 3 mW of power each. Taking into consideration an average “capacity factor” for a large onshore wind turbine, it can generate enough power for about 940 homes. However, when the wind is either not blowing at sufficient speeds, or during storm events with high winds, an alternate source of power must be relied upon.?Offshore wind turbines are typically larger structures with longer blades, and the latest designs at optimum conditions are projected to generate up to 16 mW of power per wind turbine.

?5.?????How much land is required for a wind farm, and how does that compare with other types of power generation?

One article, at How does the land use of different electricity sources compare? - Our World in Data, by Hannah Ritchie, published in June 2022, indicates that wind energy projects have consumed anywhere from 8.4 square meters per mW hour of annual electric power to 247 square meters per mW hour.?This compares to a natural gas fired power plant of 1 square meter per annual mW hour, 0.3 square meters per annual mW hour for a nuclear facility, and 3 square meters per annual mW hour for a solar (Photovoltaic) cell facility.?One footnote in the article is that the wind turbine facilities also often allow dual use for much of the land beneath and in between the wind turbines for farming and ranching.

6.?????Who are the major manufacturers of large wind turbines, and how much do they cost?

The top 5 suppliers of wind turbines by total installed power capacity in 2019 were: General Electric (US), Siemens (Spain), Vestas Wind Systems (Denmark), Goldwind (China), and Envision (China).?Six of the top ten manufacturers worldwide are based in China.?According to an article posted by author Dan Blewett on Weatherguardwind.com, the typical cost of a large onshore wind turbine in 2023 is about $1.3 million per mW capacity, or about $2.6 - $5 million for each onshore turbine.

?7.?????How many wind turbines are there in the U.S.??And what is the average age?

According to the US Geological Survey (www.usgs.gov), there are currently approximately 70,800 wind turbines at about 1,500 wind power plant sites in the US, Puerto Rico, and Guam.?The average age of wind turbines in the U.S. will be 11 years by 2025, according to an article on EnergyFollower.com.?The estimated life of wind turbines is 20-25 years, with blade replacements at 10 -20 year intervals.

?8.??????What impact do wind turbines have on the environment?

-?????????Visual – depending on the terrain and number of wind turbines at a single location, they may be visible from 15 – 24 miles away (BLMWyomingvisual.anl.gov)

-?????????Noise – there are 2 types of noise generated from most large wind turbines – the “whoosh” sound of the blades cutting through the air with very fast wing tip speeds of up to 180 mph, and higher frequency noise generated by the gearbox and generator components.?There have been cases of some impact to humans and animals near wind turbines, and in more recent news there have been reports of at least 39 whales and 37 dolphins stranded on East Coast beaches in the US. Near where energy developers have been conducting offshore wind surveys.

-?????????Radar and U.S. Defense Department operations – the Department of Defense has recently raised concerns with plans to develop additional offshore wind turbine power projects, as they are likely to impact the effectiveness of low altitude long range radar systems as well as impacting the historical naval training areas off the East Coast.?There has also been some concern with the possible impact to ocean-going ship radar impact by the offshore wind turbines.

-?????????Birds and bats – depending on which source you consult, estimates of the number of birds killed by wind turbines varies significantly- some sources estimate only 1.4 million birds and 2 million bats killed in the U.S. annually (, while another website claims the actual count may be more than 10 times those figures (Windmillskill.com – St Francis Arboreal & Wildlife Association).?Something I was not familiar with was that the U.S. Department of Interior’s U.S. Fish and Wildlife department has issued 30 year permits to wind farm projects that allow for “incidental taking” (killing unintentionally) Golden and Bald Eagles which exempts them from public reporting of how many of the protected specie birds are killed at their locations.

-?????????Disposal of wind turbine parts – particularly wind turbine blades.?According to an article by Benedette Cuffari in 2021 posted on AZO Cleantech’s website, the average wind turbine blade in the U.S. has a useful life of up to 20 years, but in many cases, operators are replacing the blades after only 10 years due to vastly improved blade designs that will generate more power over a wider range of operating conditions.?Her article mentions that 1,000 fiberglass/ composite blades were disposed of in one landfill alone, in Caper, Wyoming, between September 2020 and March 2021.?An article in the Los Angeles Times from February 2020 stated that over a four-year period from 2020 – 2023, it was estimated that 8,000 turbine blades per year would be sent to landfills in the U.S., at sites including Lake Mills, Iowa, Sioux Falls, South Dakota, and the Casper, Wyoming site.?The older turbine blades are typically 100 – 160 feet long, and composed primarily of fiberglass, which is a difficult material to recycle.?The blades are typically cut into pieces 40-50 feet in length and buried in piles of up to 30 feet high.

?9.?????How many wind power projects have been cancelled or delayed due to public opposition in the past few years?

According to author Robert Bryce, in his database of renewable energy projects rejected, there have been 391 wind energy projects in the U.S. that have been cancelled or significantly delayed since 2013 due to local opposition in the communities where they were proposed – 56 of those were in 2022 alone.

?10.?How do offshore wind turbine projects differ from onshore wind turbine projects?

The first offshore U.S. wind farm project was the Block Island windfarm, which included five turbines, each with 6 mW maximum power output.?It began operating in 2016.?Offshore turbines are more expensive to construct than onshore wind turbines and are typically much taller and with much longer blades, which allows them to generate more power than the typical onshore turbine.?Power output from the newest designs is projected to supply up to 16 mW per offshore turbine – 5 times the power output of an average large onshore wind turbine. Maintenance costs are also reported to be significantly higher, due to the type of equipment and number of personnel required to access the turbines.

?11.?What are some emerging technologies and developments in wind power?

Several developments are underway by government researchers and Wind Energy industry participants.?(See Klarian.com) – Vertical axis turbines that look like a food whisk or mixer, as shown in the photo below – are already in use in Europe and offer the benefit of lower wind speeds to start turning the turbine, as well as quieter operation.?Wind deflecting devices at the center hub have been tested and determined to improve existing traditional 3-blade turbine efficiency.?Bladeless turbines that utilize vibrations to generate power, which would be lighter, shorter, quieter, and cost less, are already in development by Vortex Bladeless.??Recyclable blades for existing wind turbines, which would replace existing fiberglass and epoxy/ carbon fiber blades which were not designed to be easily recycled.?WWW.Canadianmanufacturing.com reports that a new ”nautilus shell” design wind turbine has been designed and has sold more than 7,000 of their turbines worldwide for home use, with each unit producing up to 1,500 kWh. (Picture at the bottom below).

*“Blowin’ in the Wind” is a song written by Bob Dylan in 1962.?You may recall the refrain in the song: “The answer my friend, is blowin’ in the wind…the answer is blowin’ in the wind”.