Flywheels - an amazing alternative to batteries that never took off
Flywheel energy storage might be just what we need to stop the world from heating up.
You've probably already noticed that automotive industry is slowly changing. The golden standard of internal combustion engines is being overthrown in favour of battery electric vehicles right in front of us. All of this is happening in the name of environment, which we should, at least in my opinion, preserve at all cost.
However, I'm not a big fan of battery electric vehicles. Whilst I like their looks and performance, they might not be as eco-friendly as manufacturers make you believe, as production of batteries requires a lot of precious and hard to get materials, which isn't ideal if you want to save the world. I've explored a Polestar's report regarding the sustainability of their 2 model in this article, you can check it out if you want to.
That is not to say I'm against the change. In fact, I get very excited whenever I hear about new developments of hydrogen power and other non-battery EV stuff. That's why I think it's a shame that flywheel energy storage hasn't made its way into automotive industry yet. What is the flywheel energy storage you ask? Let me explain.
A simple diagram of a flywheel energy storage. By Pjrensburg - a rendering from a solid-works model, edited to include labels, in png format Previously published: 2012-04-29, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=19258681
Technology from back in the day
Flywheel is, in simplest terms, a disc that spins on an axle which can be used as an energy storage. Amount of energy it can store is dependent on its mass, size and speed of rotation, so there are a lot of possibilities in this area. Flywheels have been with us for a quite a long time, they were a crucial part of James Watt's steam engine, a predecessor of all internal combustion engines and a cornerstone of the modern world. You are probably acquainted with them as well, as they are used to keep your car running when you are not on a throttle.
However, they haven't been used as an energy storage extensively (at least in the automotive industry). Their most prominent application was probably a gyrobus, an electric bus that used the flywheel to store energy that was later used to power its electromotor. It was developed around 1950 in Switzerland, it had a short range of about 6km and was intended to operate on short, infrequently used routes. Whilst the range might seem short, the bus could have been recharged in a matter of minutes, which somewhat compensated for it.
Possibly the only survivng gyrobus. It had its flaws, but it was a proof of concept. Photo by Vitaly Volkov, Волков Виталий Сергеевич (user kneiphof) - Own work, CC BY 2.0, https://commons.wikimedia.org/w/index.php?curid=4036944
Failed F1 perspectives
More recently, the flywheel energy storage system made its way into hybrid racecars. Developed by Williams Hybrid Power, a company owned at the time by Williams F1 (yes, this Williams), it has been featured in Audi R18, a Le Mans Prototype race car and has seen a lot of successes in endurance racing, going as far as to win 2012 and 2013 FIA World Endurance Championship. Whilst the race wins cannot be entirely attributed to the flywheel hybrid system, they've definitely proven that this technology has some great potential.
Unfortunately, despite many efforts by Williams around 2009, the system never made it to the F1. I won't get into too much details regarding their attempts, but if you want to know more, Chain Bear made a great video about it. Apart from the Audi's Prototype, flywheel energy storage was also used in a Porsche 911 GT3R, which debuted in the 24 Hours of Nurburgring endurance race in May 2010. The car didn't win it, but it successfully managed to stay in the lead for solid 8 hours of racing. Later on, the system was sold to GKN Automotive, a British firm manufacturing drive systems, and it didn't make any more headlines.
Why I think it is great
Since Audi and Porsche managed to find a pace advantage in the flywheel energy storage, there must be some merit to it. So what benefits did they find in this system?
First of all, the flywheel turned out to be very well suited to the racing environment. It was primarily charged from a regenerative braking and whilst it wasn't able to store as much energy as a conventional battery could, it could release it all very quickly, giving an extra boost every time the car accelerated out of a braking zone. Flywheel acted a lot more like an ultracapacitor than a battery in a sense that it was able to charge and discharge very quickly without breaking down. In fact, Hartmut Kristen, director of Porsche Motorsport at the time, claimed that the flywheel could last over one million cycles, whereas top-of-the-line batteries back then could last about 20,000 cycles.
This brings me nicely to a second advantage of the flywheel energy storage, significantly decreasing wear and tear on the car's components. Porsche 911GT3R might not have been as fast as other 911s racing in the 24 Hours of Nurburgring, but it made up for it with lower maintenance. It was way more efficient with its fuel use (in fact 25% more efficient), which meant it spent much less time refuelling. Additionally, the brake pads lasted much longer than on regular cars. What's even more fascinating is that regular batteries probably wouldn't last the whole duration of a race, which once again played into the advantage of the flywheel.
The list doesn't end there. Flywheels do not use rare earth elements like batteries do. If you can make them spin very fast efficiently, they can be very compact, as the amount of energy stored depends on a square of its rotation speed. And recent advancements in nanotechnology may be just what the automotive industry needs to make flywheels feasible, since they have shown their potential in other areas like research laboratories and grid energy storage.
Yes, there are drawbacks
Unfortunately, flywheels aren't perfect and there are several reasons as to why they haven't made it to regular passenger cars yet. First of all, making them operate efficiently isn't a piece of cake, as there are many losses associated with their operation, like air resistance and internal resistance of the bearing within the flywheel, which can get quite significant when it's spinning very fast. You can get around some of the inefficiencies by running it in a vacuum, but this isn't easy either.
And this seems to be the nail in the flywheel's coffin. Other drawbacks, like possible noisiness and danger associated with having fast spinning object in your near vicinity (come on, we are already driving around with boxes full of highly flammable liquid) pale in comparison to the sheer inefficiency of the flywheel, whether it is related to its size, weight or just energy losses.
In order to store large quantities of energy, flywheel has to be big, heavy or fast spinning, which is hard to achieve efficiently in a car
Is there a future for a flywheel?
This all might sound very pessimistic for a future of flywheels. They're drowning in inefficiency, which means that for now they are mainly used in places, where no other source can provide required bursts of energy. However, I think there might be the light at the end of the tunnel. If no significant improvements are made in terms of battery technology, we might have a shortage of power cells in a near future, especially with a rapidly growing sales of EVs. Then, some industries might look for others means of storing energy, and we may see a return of gyrobuses and possibly a wider adoption of flywheels in passenger vehicles. Or maybe I'm just daydreaming, and flywheels will only be used in certain specialistic areas, much like jet engines are.
For now, I can see them being used instead of chemical batteries in hybrids, taking advantage of regenerative braking and excess power made by the engine whilst idling. But then again, the forces in regular passenger cars aren't that great to begin with, and for the latter issue, we already have a solution - it's called start-stop.
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