Blades vs Wings: Wind Turbine Technologies to Save Bats and Birds

Are wind turbines indiscriminate bird killers as many news stories and politicians would have us believe, or are they the renewable energy technology that will ultimately save them? Let’s unravel the fact from the fiction to find out whether wind turbines really are a significant danger to birds, and discover which technologies are available to allow them to coexist.

Full disclosure

I am a mechanical engineer complete with PhD. I’ve worked with renewable energy technologies for the past two decades, a lot of that designing wind turbines. And, I’m also a certified bird nerd. Australia has the best birds in the world, in my opinion, and I often take my binoculars with me in daily life so I can identify and check off new sightings in my bird app. I have taken hours of video and thousands of pictures of birds over the years, some of which you’ll be seeing onscreen throughout this video. I even named my clean energy technology consulting business after my favorite bird, the tiny pardalote. With my dual perspective as an engineer and a devoted bird nerd, I strive to approach the issue of birds and wind turbines with utmost impartiality.

Eyeing birds and a birds eye view - I love both birds and wind energy

Why wind turbines are killing birds

So let’s cut to the chase: why are wind farms killing birds? After all a wind turbine is a huge piece of machinery and birds have notoriously good eyesight, so why aren’t the birds simply avoiding them altogether? Well one reason is that many birds, particularly birds of prey, spend much of their flight looking down at the ground in search of their next meal. With their eyes focused hundreds of metres below they fail to notice turbine blades rushing down from above.

Then there’s the speed of wind turbine blades. Yes they look peaceful and serene when viewed from afar, but though the rotational speed of large turbines is slow, the blade tips are usually travelling over three hundred kilometers per hour. Even the fastest and most agile birds are going to have trouble dodging that if it strays too close.

The other reason we have seen large numbers of bird fatalities around wind farms is the location and siting of those farms. For example, California’s infamous Altamont Pass wind farm was constructed right in the middle of a migratory bird route. The area is host to hundreds of thousands of migrating birds passing through each year, and is a permanent home to thousands more birds of prey that rely on the migratory birds to sustain them. With such large numbers of birds and wind turbines all concentrated together, avian fatalities were probably inevitable.

Wind farms and bats

Now, it’s not just birds that are at risk, wind farms also pose an equally serious threat to bats. But bats aren’t generally held in as much affection as birds, they don’t enjoy the good PR that birds do, and so you’re less likely to see news articles chronicling the plight of bats vs. wind turbines. I personally think that bats are amazing. They’re mammals like you and me, but they’ve managed to evolve themselves to the point where they have flight and sonar capabilities without needing to step inside a fighter jet or submarine like we do. And, I’m told bats are just as crucial to ecosystems as birds, being essential pollinators, seed dispersers and pest controllers.

Numbers in perspective

So just how many birds and bats are killed by wind turbines? There are some good US studies on this topic, which each showed estimates of a few hundred thousand bird deaths in the US attributable to wind turbines. They were using 2012 data, and since then the amount of wind energy generated in the US has just about doubled. So extrapolating from that, the general consensus is that these days around 1 million birds are killed each year by US wind turbines. The number of bats killed by wind turbines is similar, though bat fatality estimates are less certain than for birds. Of course the combined figure of potentially upwards of a million birds and bats killed by wind turbines is a vast one. And remember, that’s just in the US, global figures are obviously many times that.

Comparison of major sources of direct anthropogenic bird mortality for the United States and Canada. Loss et al 2015

I mentioned I’m a bird and bat lover, and as such I think that millions of bird and bat fatalities due to wind turbines absolutely sucks. However, this is nothing compared to the number of birds killed by other human causes each year. Power lines, communications towers, cars and buildings each cause ten to one thousand times more bird deaths than wind turbines do. But even this is a fraction of the number of birds killed each year by Felis catus, better known to you and me as the domestic cat. That’s right, that little purring ball of fur on your sofa is responsible for around two and a half *billion* bird deaths each and every year, just in the united states.

And there’s one other killer I haven’t yet mentioned. And it’s a threat that’s poised to kill not just hundreds of millions of birds and bats, but will wipe out entire species.

Climate change

The truth is that the biggest threat to birds, bats and indeed all wildlife is climate change. Unless something can be done to stop environmental change to the habitats and ecosystems in which wildlife lives, all animal life will face mass reductions in populations or even extinction. Of course one of the primary methods we’re going use to bring climate change back under control is through switching to renewable energy sources, particularly wind power. Every credible net-zero energy scenario includes a huge amount of wind energy in the equation. It’ll be vastly more difficult, more expensive and much slower to transition to renewable energy sources without wind. For example, only using solar would mean we needed huge amounts of energy storage for use at night, plus dramatic developments in long-duration energy storage to account for less solar energy throughout the winter months. So if wind farms are essential to combating climate change, and thus play a key role protecting all wildlife as a whole, what is the engineering community doing to reduce the impact wind turbines have on aerial wildlife?

Methods to reduce bird fatalities

Wind turbine design

One of the biggest reductions in wind turbine bird deaths has been the design of the turbines themselves. I mentioned earlier the Altamont Pass wind farm in California, which is often cited by wind turbine critics for the high number of bird deaths it caused. Well the turbines at Altamont Pass were designed and constructed back in the early 1980s, and were therefore much smaller than modern wind turbines. The blades on small wind turbines are situated much lower to the ground and rotate faster, so they pose a greater risks to birds and bats during takeoff and landing. Not only are engineers now designing larger wind turbines, but the designs are also sleeker. Older tower designs were often a lattice structure, similar to electricity towers that birds found ideal for perching on. Unsurprisingly, roosting directly under spinning turbine blades led to many bird deaths. Today wind turbines are designed with monopole towers that offer few perching places for birds or bats.

As the original 1980’s and 1990’s wind turbines at Altamont Pass and many other wind farms are gradually getting replaced by larger, modern turbines, they are becoming safer for birds. When bird deaths from old and new turbines operating concurrently at Altamont Pass were compared, it was found that the modern turbines have 66% lower bird deaths per unit of energy generated.

Black blades

Wind turbine in the Smøla wind-power plant with painted rotor blade [Roel et al 2020]

Another method engineers have looked into in order to make wind turbines safer for birds is to paint one of the turbine blades black. When all three turbine blades are left white, they ‘blend’ together as they rotate and are harder to see. But the addition of black - either a single blade or striped blades - creates a visible pattern as they spin, making it easier for birds to see them. A small study in Norway painted black blades on 4 wind turbines and over a period of 3 years, they found the number of bird collisions to be reduced by 70 percent compared to control turbines. A slightly larger trial with 7 turbines owned by RWE is ongoing in the Netherlands due to be completed at the end of 2024. [8]

This solution sounds simple, but in reality it does create some complications with blade manufacturing and function. Wind turbine blades usually get their colour from a gel coat that is put in the mould before the fiberglass and other materials are laid in there. It would be hard to make a third of the blades with a black gel coat, because blades straight out of the factory don’t all weigh exactly the same. They need to be matched into sets of 3 blades of similar weight so that turbine rotors are balanced. Adding in the need to match sets by colour as well as by weight would be a pain. Also, a black blade will heat up in the sun and become more flexible and therefore bend more against the wind. If it’s a single black blade, that could unbalance the turbine rotor, not to mention the possibility of hitting the tower or breaking from fatigue loading if the bend was severe.

So that might be the reason that twenty years after the original study into this idea was published, we have only seen a total of eleven turbine blades painted. It only sounds simple, it’s not as easy as just getting out a can of spraypaint.

Radars and cameras

Closer to home, or my home anyway, is the introduction of cameras and radar technology to wind farms. The Cattle Hill Wind Farm in Tasmania uses optical devices and AI software to detect vulnerable wedge-tailed eagles and white-bellied sea-eagles. When the system identifies either of these protected species it initiates a brief shutdown of the turbines, stopping their blades turning until the bird or birds have left the area. Cattle Hill Wind Farm went into operation in 2018 and the final report on the effectiveness of the IdentiFlight avian detection system was published in 2022, showing a significant drop in actual eagle fatalities compared to predicted fatalities. [9]

Also in Tasmania, the Musselroe Wind Farm uses a new avian-specific radar technology to detect endangered birds and enable the turbines’ operation to be adjusted to prevent collisions. The technology provides 3D coverage across a visible field from the horizon to one kilometer above ground. Once an endangered species is detected, the radar system can initiate turbine shutdown. During its first six years of operation with the radar system, Musselroe Wind Farm experienced just a single white-bellied sea eagle death and 11 wedge-tailed eagle deaths due to turbine collisions. [10]

Sonic deterrents

As I said at the beginning, birds aren’t the only flying wildlife affected by wind turbines, bats are equally at risk. To prevent bat deaths sonic deterrents have been installed at wind farms for over 20 years now. Speaker systems installed on top of wind turbines can emit a high-frequency ultrasound that discourages bats from approaching the area without causing them any harm. Being beyond the hearing limit of humans or other wildlife species, the sound is otherwise unobtrusive. The combined findings of governmental studies by the likes of the U.S. Department of Energy, and collaborative studies between universities, energy companies and regional wildlife departments have all been positive. Figures show reductions in bat deaths as high as 78 percent thanks to sonic deterrents. [11]

Slowing blades

Sometimes the simplest solutions are the most effective and the Dutch government are currently trialing one such program. Wind farms situated across known migratory routes will slow or halt the rotation of their turbines during migratory seasons, thus reducing the chances of birds being harmed. A model developed by the University of Amsterdam predicts up to two days in advance when birds will be migrating across the North Sea in search of warmer climates. Using this advance warning, the Dutch government will require the energy companies to reduce the rotation of turbine blades or stop them completely for 12 to 48 hours, allowing birds to safely pass through specific areas. This program is brand new and currently undergoing trials, but it is believed it will significantly reduce the approximately 50,000 bird deaths caused by Dutch offshore wind farms each year. [12]

Land management

It’s not just changes to wind turbines that can prevent bird and bat collisions. Studies into land management suggest that lightly tilling the soil around wind farms makes the area a less attractive habitat for birds of prey to settle in. Superficial tilling prevents rodents and other small animals from making the area their home, and with nothing to feed on, birds of prey will look elsewhere. A study in the Journal of Environmental Management showed that soil tilling around wind farms led to a 75 to 100 percent decline in collisions between kestrels and turbine blades over a two-year period. [14]

Regulatory measures and environmental approvals

The ongoing study of bird behaviours has become a determining factor in the planning and construction of wind farms. From an operational standpoint the location dictates how effective and efficient a wind farm will be. But the location also plays a huge role in the coexistence between the wind turbines and the surrounding wildlife. It used to be that wind farms were constructed pretty much solely based on where winds were strongest and most consistent. But now the environmental approvals that all wind farms are subject to during their planning and development phase include ensuring that wind turbines cause minimal disruption to birds and bats. The Altamont Pass wind farm in California that I mentioned a couple of times is a good example of how these legislative changes based on scientific studies’ findings are shaping just where energy companies are allowed to construct new wind farms. And as our understanding of exactly how wind farms affect birds, bats and other forms of wildlife improve, so new legislation will be enacted, making wind farms ever better for the ecosystem and wildlife as a whole. [16]

So, as we’ve seen, while wind farms aren’t perfect, they are nowhere near the worst threat to the safety of birds and bats. Thanks to the work of scientists and engineers across the globe there are now a range of solutions being implemented by governments to ensure the safety of wildlife, and especially of endangered species. I think it’s interesting that the amount of attention paid to wind turbines and birds is so disproportionate to the number of deaths they cause. You’ve probably never thought to worry about how many birds are killed by buildings or powerlines each year. If you are worried about birds then I would suggest that keeping your cats inside is a much more impactful thing to do than opposing a local wind farm.

References

1. https://www.sierraclub.org/michigan/wind-turbines-and-birds-and-bats

2. https://www.energymonitor.ai/tech/renewables/weekly-data-how-many-birds-are-really-killed-by-wind-turbines/

3. https://stopthesethings.com/2021/01/28/bidens-bird-slaughter-green-new-deals-wind-turbines-will-kill-1000000-birds-annually/

4. https://wildlife.onlinelibrary.wiley.com/doi/abs/10.1002/wsb.260

5. https://www.engineering.com/story/the-realities-of-bird-and-bat-deaths-by-wind-turbines# and https://wildlife.onlinelibrary.wiley.com/doi/full/10.1002/wsb.260

6. https://www.sierraclub.org/michigan/wind-turbines-and-birds-and-bats and https://us.orsted.com/renewable-energy-solutions/offshore-wind/seven-facts-about-offshore-wind/birds and https://www.energymonitor.ai/tech/renewables/weekly-data-how-many-birds-are-really-killed-by-wind-turbines/and https://www.engineering.com/story/the-realities-of-bird-and-bat-deaths-by-wind-turbines and https://www.energymonitor.ai/tech/renewables/weekly-data-how-many-birds-are-really-killed-by-wind-turbines/

7. https://www.nationalgeographic.com/environment/article/notorious-altamont-wind-area-becomes-safer-for-birds

8. https://www.evwind.es/2022/02/02/black-turbine-blades-reduce-bird-collisions/84464, https://www.newscientist.com/article/2361507-stripy-wind-turbines-could-prevent-fatal-seabird-collisions/ and https://fortune.com/2022/11/22/wind-farms-bird-deaths-blades-turbines-paint-black/, https://www.theatlantic.com/science/archive/2023/01/solar-farms-renewable-energy-killing-birds/672877/

9. https://cattlehillwindfarm.com/wp-content/uploads/2022/03/Assessment-of-IDF-Avian-Detection-System-FINAL_updated.pdf, https://www.cradlecoast.com/5091-2/ and https://www.identiflight.com/how-it-works-2

10. https://reneweconomy.com.au/musselroe-wind-farm-to-deploy-bird-protecting-radar-in-australian-first-trial-89517/, https://www.cradlecoast.com/5091-2/

11. https://www.sciencedirect.com/science/article/pii/S2351989420301827, https://www.energy.gov/eere/success-stories/articles/concept-commercialization-bat-deterrent-wind-energy-goes-global and https://news.txst.edu/research-and-innovation/2020/study-shows-ultrasonic-deterrents-significantly-reduce-wind-turbine-bat-fatalities.html