How Do Windmills Work and How Do They Compare

How do windmills * work, and how do they stack up against other renewable sources in terms of environmental impact?

* Technically a windmill uses energy collected from the wind specifically to grind grain into flour. But, I’ll use this term interchangeably with wind turbine to mean anything that converts wind energy into electricity.

Technically the first one is a windmill and the second one is a wind turbine, but who cares.

I’m always curious about the carbon footprint of different foods, clothes, and other consumer products. Obviously it takes resources and energy to build anything – including renewable energy sources. So I started wondering, which renewable source has the lowest carbon footprint?

Related: Carbon Footprint Sources

Just calculating the carbon footprint of any power plant isn’t very helpful in determining how efficient it is, though. There are different sizes of plants. Clearly the largest solar farm in the world is going to have more solar panels (and therefore a larger carbon footprint) than a single wind turbine. There are a couple of ways to look at this. One is Energy Return on Investment (EROI). That is, how much energy do you get out of a plant compared to what you put in while creating that plant? Also, no power plant can stay around forever without any maintenance – which requires more energy. Another option is to look at the carbon footprint per kilowatt of energy generated over the lifetime of the plant.

Fortunately, people much smarter than me have already done all of these calculations! The winner is (as you’ve probably already guessed from the title)…wind! 

Why Wind?

Multiple studies have shown that wind turbines consistently rank as one of the greenest sources of energy in terms of carbon emissions. It makes sense if you think about it. Wind turbines are relatively small compared to other energy sources, so they don’t require a lot of materials to build. They also don’t require special elements like the gallium and indium found in solar panels or the uranium used for nuclear fuel rods.

Wind energy also doesn’t have the unique issue hydroelectric dams are dealing with. Some of these dams actually have a huge carbon footprint! That’s because the flooded area created when making the dam has a lot of biomass covered by water. This causes it to decompose anaerobically creating large amounts of methane – a gas with 25 times the global warming potential of carbon dioxide. Last but not least, no fuel is fuel required to run wind turbines other than wind! 

How Do Windmills Work

When you look into almost any method of generating electricity, at its core you will find a spinning turbine. There are a few exceptions, including photovoltaic solar. But coal, gas, nuclear, geothermal, hydro, wind, and concentrated solar all operate on this principle. Once you get a turbine spinning, you have an electric generator.

windmills
Spinning in the wind.

Most of these methods rely on using heat to boil water and create steam. That steam goes up through a shaft and spins a turbine. Coal, gas, nuclear, geothermal, and concentrated solar all work this way. Hydro generates electricity by spinning a turbine with the water that comes rushing out of a dam.

It makes sense that windmills would be such an efficient use of materials for generating electricity. If you think about it, it’s like we’ve taken the core electricity generating device that almost all other methods use, the turbine, and just put it by itself, out in the wind. Instead of having to heat water to create steam, we can just sit back and let the naturally occurring wind spin the turbine for us.

Windmills Aren’t Perfect

The point of this article is not to say that all of our problems can be solved with wind power. Although we could meet all of the world’s energy needs with an area half the size of Alaska. But, of course, the wind isn’t always blowing. Intermittent power sources need to be stored for later use when needed, and large scale battery systems can be prohibitively expensive.

Then there’s the issue of the impact to wildlife. A surprisingly high number of birds and bats flying into wind turbines. Over half a million birds and at least 600,000 million bats are killed every year by wind turbines. However, power lines kill at least 28 million birds a year, and that doesn’t even come close to over 2 billion killed by house cats annually.

kitty cat
The real bird killer.

But you have to weigh that against the fact that all birds, bats, and every other living thing on this planet is threatened by global warming, and renewable energy is one of the best ways to combat that.

Related: Polar Bears Extinct by 2100 Due to Global Warming

Ultimately, like most things in life, the answer to our fight against global warming will have to have a bit more nuance. It will need to be a combination of all the renewable sources we currently know about. We’ll also need to invest in carbon capture and sequestration, and even plenty of fossil fuels to help with the transition. (Not too much though, since we need to leave two thirds of all the fossil fuels we currently have in global reserves in the ground in order to prevent a 2 C rise in temperature.)

Related: When Will We Run Out of Oil

2 thoughts on “How Do Windmills Work and How Do They Compare”

  1. Good points. Is there a resource that shows where wind turbines are most effective? The mid west, for sure, but how about East Tennessee?

    1. Yes! Actually I really like this map by the University of Texas that shows the most cost-effective source of energy for each part of the US. If you click the checkbox labeled “include externalities” you’ll see the most cost-effective sources of energy with the price of capturing and sequestering the carbon emissions factored in. If you do that you’ll see that East TN’s most cost-effective energy source is actually photovoltaic solar. I’ll be writing an article soon that talks about environmental externalities in more detail!

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