In the last blog we looked at how solar energy can be sustainable. Let’s do the same here briefly for wind farms.
In case you don’t know how a wind farm works in principle: A wind turbine is the opposite of an electric fan: while you run the fan with electricity to move the air, the air moves the wind turbine (the rotor) to generate electrical energy. The motor in the fan and the generator in the wind turbine work according to the same physical principle. In fact, a motor can operate as a generator and vice versa. That is why an electric car or bicycle charges the battery when it decelerates, and electric trains feed the overhead line when they go downhill.
While silicon PV plants hardly differ except in size, wind farms come in larger varieties. Therefore, we do not consider a specific wind farm, but an assessment  from an average onshore wind farm with 20 turbines. The following quantities of materials are used:
The turbines in onshore wind farms need to be firmly anchored and they are often located on mountain ridges where a road and a high-voltage power line need to be built, so they require large amounts of concrete and steel. Offshore wind farms are anchored with steel structures and require very little concrete, but usually longer power lines. Also, some manganese is added to make the steel corrosion resistant at sea . By the way, oil industry companies can help build offshore wind farms with their expertise in offshore oil platforms.
Sophisticated modelling predicts  that running the entire planet on 100% renewables will require wind energy capacity of at least 8 TW, which is less than PV. Let’s assume that the wind farms are frozen at the current state of technology and that these 8 TW are realised by multiplying the wind farm from the previous graph. This gives an estimate of the materials needed worldwide. Since these are large numbers that do not tell us much, we compare these quantities of material with that which was produced worldwide in 2020 :
Wind farms use mostly classic commodities that do not pose material supply risks or new mines to be opened, and are routinely recycled . The glass fibres and resin for the rotors only use abundant raw materials, but are not (yet) recyclable, but sometimes reused for other purposes .
Since wind farms use more steel and concrete than PV plants, their CO2 emissions during the construction phase tend to be somewhat higher   :
Many of these CO2 emissions come from the use of fossil fuels used for steel making and concrete, which will decrease in the course of the global energy transition. Hence, the manufacture and installation of all wind farms for a global energy transition will emit around 0.5 gigatons (Gt) of CO2, compared to a total of about 43 Gt emitted globally this year alone.
The construction of wind farms can have an impact on wildlife and humans. Bird deaths are often discussed by the public, but are negligible compared to how many birds are killed by windows in buildings, traffic, pesticides and even cats: only about 1 in 10,000 deaths are caused by the rotors . Bird deaths are more imagination than reality . For example gliding birds are aware enough to avoid wind turbines within a radius of about 700 metres. This causes a loss of functional habitat if the wind farm is large  but does not kill them. Smaller birds do not tend to fly at the height of the rotors, and monitoring shows that their chance of being caught by a rotor blade is low. Still, planning of wind farms needs environmental considerations, and recommendations for environmental impact assessments are being developed .
Another impact is noise pollution if wind turbines are located too close to human settlements. However, similar to bird mortality, the claims often cannot be confirmed by measurements. For example, if you have a tree in your garden, the tree is louder than a wind turbine 500 metres away at any wind speed (I have tested this myself with microphones). And there is usually a road near a house: switching to electric vehicles will reduce noise more than most wind farms create noise. Noise is in fact the biggest detriment to wildlife in offshore wind farms. It can disrupt fish communication  and should be avoided near marine parks. Nevertheless, it is not as bad as shipping traffic and the noise in very windy regions .
If the wind farms are carefully positioned, their environmental impact is well proportioned to the environmental benefit. Is that all we can say about wind farms?
You may have noticed the public debate about rare earths elements in wind farms. Neodymium, praseodymium, dysprosium…. geopolitical competition… material constraints on renewable energy….
Here are some often overlooked but – for technology insiders – obvious facts:
– Most onshore wind farms do not contain rare earths. It is a low-cost segment that usually cannot afford them .
– Most new offshore wind farms can afford rare earths because they reduce maintenance costs and because it is easier to build wind turbines bigger and more efficiently .
– There is no technological need for rare earths in wind farms; nor in solar or any other renewable energy that I am aware of . In the cases where they are used, it is for economic reasons so long as they are relatively cheap.
– Typical studies like  warn against geopolitical competition and material constraints for renewables. I think it is good that they question business as usual, but they are often not based on the facts just listed .
So that these points do not seem like mere assertions to you, I explain some technical details in a simple way. I have already mentioned that an electric motor can be operated as a generator and vice versa. Both need magnetic fields. You can create such fields either with a magnet or by letting an electric current flow through wire windings, which is what you see when you open an electric motor :
On land, wind turbine generators create their magnetic fields by diverting part of the generated current through such wire windings, and there is usually a gearbox between the rotor and the generator, which requires more maintenance. For offshore wind turbines, maintenance is more expensive, so the gearbox is avoided by using magnets instead of wire windings. To make such magnets stronger and more stable, rare earths are used, because only a few elements are magnetic: The most common element is iron, but its magnetic field is rather weak and can weaken over time.
However, by changing the geometry of the generator , a big wind turbine does not require magnets and it can still be operated without a gearbox. Suggestions for such geometries (hidden at the top of the tower) look like this:
There are many more possibilities than the ones shown here, and they look quite aesthetic because they are designed according to physical principles.
It is not easy to build generators in wind turbines with such geometries and still require little maintenance and suffer few losses. But given the many possibilities, do you think that engineers and physicists will not succeed in finding more than one solution in a relatively short development time?
This points to an interesting pattern in technology development: As a technology evolves, materials are optimised and supply chains are streamlined. This can make rare earths obsolete in most technologies . By the way: technology with prestige aspects does not usually follow this pattern but becomes more material intensive. An example of this is cars and electric cars, which I will talk about in a later blog article.
Sustainable or not?
Now comes the crucial question: Can wind energy be a sustainable technology when scaled up to a worldwide transition to 100% renewables?
My previous blogs have shown that sustainability has many aspects, which cannot all be covered in a few blog articless. Sustainability also depends on the supply chain and on how the technology is concretely applied. For example, clearing protected tropical forests to build wind farms is certainly not sustainable. I argue as follows.
Wind energy can be a sustainable backbone of our world running on 100% renewable energy if:
– Environmental and social conditions for copper mining are improved, as outlined in the previous blog.
– The magnets in wind turbines are either  designed for reuse,  or do not contain rare earth elements.
– Wind plants are designed for better reuse of parts , .
– Wind farms are placed in an environmentally responsible way.
Under these realistically achievable conditions, the use of renewable energy makes nearly every country, business, and household much more sustainable.
In a future blog, I will use a collection of data to show that this can all be done more easily if rich countries and some middle-income countries reduce their energy consumption, which is possible without sacrificing prosperity and wellbeing.
I hope this blog article has given you a more nuanced view of wind energy and its impacts.
Do you have a renewable electricity provider for your business or institution or household? In your profession, can you promote the deployment or usage of renewable energies? What arguments do the people around you put forward?
I am happy to hear your comments.
The photo of the wind turbine was taken by the author. The photo of the electric motor has nothing to do with wind turbines.
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