ENB Pub Note: This is a guest post from the Pengquin Empire Reports Substack. We highly recommend supporting and following them.
“In the financial world, it tends to be misleading to state ‘There is no free lunch.’ Rather the more meaningful comment is ‘Somebody has to pay for lunch.’ ” – Martin J Whitman
Just how big is a wind turbine?
While wind is ‘free,’ harnessing it isn’t. Wind is dispersed, or diluted. Even in windy areas, there’s only so much energy that can flow through a turbine’s blades. To capture that low density resource, we need really big machines.
In the subsidy fueled hype of the energy transition, we’re trying to move away from concentrated sources -such as oil, natural gas, and coal – and attempting to replace them with diluted, dispersed sources such as wind. But all of life is a trade-off. As Robert Bryce says, “The shape and size of our energy systems are not being determined by political beliefs about climate change. Instead, those systems are ruled by the Iron Law of Power Density which says: the lower the power density, the greater the resource intensity.”
To understand one aspect of the trade-offs to get that ‘free’ wind, let’s break out the scales and measuring tape.
We’ll start with something that many people will be familiar with.
Chances are, you or someone you know has flown on a Boeing 737. I spent a lot of time on 737s, going to and from college, work, or vacation on a certain budget airline known for its fleet of 737s, ‘free’ snacks, ‘free’ checked luggage, no assigned seating, usually friendly service, and *mostly* on time flights. It’s obvious but important not to overlook that those ‘free’ things were paid for with the money I spent on the tickets.
Photo by Miguel Ángel Sanz on Unsplash
While not the biggest airplanes by any stretch, 737s are still pretty big. The max take-off weight for 737-700, with up to 149 passengers, is about 77 tons. The much larger 737- MAX 10s can carry ~230 passengers with a max takeoff weight of ~ 99 tons.
Lets say you were on one of those 737s, on your way to a much deserved trip to the beach, Vegas, or perhaps the mountains. If you fly over the middle part of the continent, there’s a good chance you flew over a wind farm. You might even spot turbines from the plane, depending on which airport you fly into.
And from a plane, those turbines might seem small. But they are massive structures.
If you’re not the sky-diving, adrenaline junkie type who scales cliffs before breakfast on Saturday, then you might not want to climb hundreds of feet to the top of a wind turbine, just to appreciate how big it is. Here’s a picture from the base of one. Don’t stare at it too long or you might start feeling dizzy.
Photo by Abdulaziz Alfaleh on Unsplash
Let’s save on the steps. Instead of climbing one, here are some of the details of an ‘average’ turbine. According to the 2023 Land-Based Wind Market Report by the US DOE, the average onshore wind turbine installed in 2022 has:
A rotor diameter of ~132Ms,
Is rated at 3.2MW
Sits on top of a ~98 meter tower.
For reference, that 737’s wing span is just shy of 36 meters.
Since we’re not physically climbing the turbine, here’s a screen shot from GE Vernova’s website with commentary added. The turbine cutaway is for 3.2 to 4.2MW turbines which is a fairly typical size for current installs. As you look at it, it is almost overwhelming the amount of heavy stuff compacted inside of that housing, and you can start to appreciate a turbine’s massive weight.
A typical land based turbine has a large box (nacelle) or housing for all of the machinery. Inside you’ll find a main shaft coming from the rotor with a braking system nearby to turn off the turbine when the wind is too strong to safely operate. In normal conditions, the blades might only turn 30-60 times a minute but the generator needs to spin around 1000+ rpms. To speed up the spin, a gear box that acts like a heavy duty transmission is hooked up to a generator.
But when it’s time to generate power, the nacelle needs to turn to face the wind. Think of a warships’ gun turret: the entire turbine/ nacelle sits on top of a rotating- gear like platform allowing the entire housing/ rotor to change directions.
The combination of housing and heavy machinery in the nacelle adds up to ~ 100 tons for a 3.2 MW turbine. Larger, 4.2MW nacelles can weigh~ 130 tons.
And don’t forget about the blades. Each blade can clock in at 16–25 tons. Together, the 3 blades might weigh ~ 50-75tons, depending on the length and make.
Now that 50-75 tons’ worth of blades spins: how do you keep them from flying off? The lynch pin holding it all together is a 20-35 ton hub. Not only does the hub hold the blades to the housing, but the hub also needs to allow the blades to pivot to change the pitch.
As a general rule, a wind turbine and blade assembly weighs about 55-60 tons (50-54 metric tonnes) per MW installed, based on data from the National Renewable Energy Labs. So, a 3.2 or 3.3 MW turbine and assembly easily weighs ~180-210 tons or 2 to 3 fully loaded 737s at maximum takeoff weight.
To support all of that weight, you need a steel tower, weighing ~ a couple hundred tons. Of course, mixing steel and rain leads to rust. To keep the whole thing from turning into a rust bucket in just a few months, you can use a zinc coating. According to IEA data, a 3.2 MW land based wind turbine and tower uses about 30,000 to 40,000lbs of zinc to help protect it from rust.
Adding up the turbine and tower, you’re looking at ~450-570 tons (408-517 tonnes) for a 3.2 to 4.2MW turbine.
How do you keep that from tipping over? Especially in places like “Oklahoma, where the wind comes sweepin’ down the plain.” I asked a friend that and he replied: “With a ____ ton of concrete.”
On average, a US land based wind turbine’s foundation uses ~440 tons (~398 tonnes) of concrete per MW. Doing the math, that means a 3.2MW turbine needs somewhere in the neighborhood of 1300 to 1500 tons of concrete.
Tying It All Together
Because wind is dispersed, wind farms naturally are spread out over vast areas. Also, it’s partly to avoid the turbulence kicked up by one turbine interfering with another turbine. Here’s a google maps images from the Frontier Wind Farm, located just north and west of Ponca City, Oklahoma. While the farm became operational in 2016, its 3.3MW Vestas turbines are fairly close to the average 3.2 MW beasts installed in 2022.
The picture shows about 9 turbines, for a total of 30MW of capacity. If you walked from the far left turbine, following the roads as much as possible, you’d walk nearly 3 miles to get to the last turbine on the right.
That gives you an idea of how much cable a wind farm might need to tie in just a handful of turbines. Plus, each turbine at Frontier is approx. 292 feet (89m) above the ground, meaning you’d need another ~1/2 mile or so of cables to bring the power down from the 9 towers. Copper is one of the main ingredients in cabling.
But there’s more.
Land-based wind turbines tend to produce low voltage (pressure) electricity. But that low voltage needs to get stepped up significantly to meet the transmission line’s high voltage. Think of it this way. If you took your low pressure garden hose and tried to force water from it down a high pressure fire hydrant, it’d be a disaster. To get the the low pressure power from the turbines into the much higher pressure transmission lines, you need to significantly step-up the voltage.
Often, a wind farm has transformers at each wind turbine, bumping up the lower voltage to medium voltage within the wind farm collection area. Then, at a substation, the medium voltage is bumped up to high pressure.
Copper is a great proxy to understand the high material demands of the so-called renewables transition- a transition that is trying to force us away from dense energy to diluted energy. The more dispersed and low pressure the power source, the more copper you might need to tie it together and bring it up to pressure.
Let’s contrast that with a natural gas power plant. Here are those same 9 (3.3MW) wind turbines from the Frontier Wind project. But we zoomed out just a little, and now we can see a 103 MW+ gas peaking power plant and a substation in the lower right hand corner. The gas plant, owned by the Oklahoma Municipal Power Authority OMPA, came online in 2015 and is only used as necessary.
That gas plant doesn’t need all of those multiple step up transformers, it can skip the extra miles of the interlay cables, and it only needs a fraction of the concrete. Plus, it’s not suspended on top of ~300 foot galvanized steel towers.
So it’s no surprise when we go over to the IEA’s website and look at the material demands for wind turbines. Here’s a chart below (excluding steel and concrete). Based on the global average, an onshore turbine uses 10,000kgs (~22,000lbs) of minerals per MW of installed capacity while natural gas plants tend to run around just over 1,000 kgs (2200-3000lbs).
In closing, here is a table summarizing the material needs of an onshore wind turbine. It’s from the National Renewable Energy Labs – NREL– and it includes the steel, concrete, and the road rocks needed for all parts of the turbine: the tower, housing, blades, etc.
In this article, we just discussed the material costs of capturing wind- we didn’t touch on what to do when the wind dies down, article link here. Because wind is intermittent, it means you build full sized turbines that (effectively) only do a part time job, multiplying the already high material needs. And we didn’t have time to go over the challenges in predicting wind, which you can read here.
Life, and the energy business in particular, is a series of tradeoffs. As the old saying goes, there’s no such thing as a free lunch. The question is, who’s paying for it? Because wind is a scattered and diluted resource, we pay for that ‘free lunch’ with lots of land, copper, concrete, steel, and other specialty minerals.
Source: Penguin Empire Reports
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