# Flywheels for energy storage.



## San_Carlos_Jeff (Nov 7, 2008)

This was done awhile ago on some buses, maybe they're still in use?? IIRC a couple of the problems are that the flywheels act like a gyroscope and cause weird handling, also in case of an accident it needs to be heavily isolated from the outside world. At one time a company was experimenting with flywheels made out of a composite material that would delaminate and fall apart if the wheel ever came off it's mount.


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## Duxuk (Jul 11, 2009)

Yes, this is something which needs a lot of developemnt and origional thought. I imagine that the buses you're refering toare theones used inseveralcountries including, believe it or not, Ziare! They used a slower moving 3 ton flywheel. If you look at the kinetic energy equation (half em vee squared) it is obvious that the thing you need is a high vee, in this case that's rotational speed. As for the handling you can either use 2 counterrotating flywheels, who's speed is EXACTLY THE SAME, or mout a single flywheel in a gimbal (I think that's the correct term and, hopefully spelling). This is a sort of cage with 3 axies of rotation.

Problem solved then!

I would like to know if a mercury bearing could be used. The mechanism could float on a very thin layer of Hg which extended up the side of a bucket like flywheel. THere are large stocks of Hg with no use or plans to use it. It might put the commercial cat amongst the enviromental pigeons, though! Imagine an exploding flywheel with 100,000,000 joules of energy distributing half a kilo of mercury around the place. Air-foil bearings might work though. They work in aircraft engines which have unbelievable rotational speeds.


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## icec0o1 (Sep 3, 2009)

Before you keep getting excited, think of it in terms of energy. How much energy is released in an exploding gas tank? You would have the identical amount of energy in a flywheel so whether it's fire and explosion or flying shards going at supersonic speeds, the damage would be the same. Further, would people be happy if their tanks exploded every time they were in a bumper to bumper accident? Because even a small imbalance of the flywheel would cause it to unravel and disintegrate.


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## Duncan (Dec 8, 2008)

Hi Duxuk,

5,000,000 joules is only 1.4Kwhrs and a 1 meter flywheel at 60,000 rpm !!!! would have to be made of unobtainium

bearings are not a problem - the issue is centrifugal force


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## Duxuk (Jul 11, 2009)

I posted this idea not because it is likely to be THE NEXT BIG THING, but because it does have some potential in certain applications. As i mentioned the technology is working successfully in power stations on a much larger scale. As fo the rotational speed- how fast does a turbocharger spin? 100,000 rpm is just ticking over!


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## tomofreno (Mar 3, 2009)

Manufacturer flywheels used in vehicles:
http://www.williamshybridpower.com/technology/flywheel-background

Manufacturer for grid storage:
http://beaconpower.com/


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## Duncan (Dec 8, 2008)

100,000 rpm at 100mm is easy 
60,000 rpm at 1000mm is not - the limitation is the strength of the materials

You get into very high strength composites - and 60,000 at 1 meter - the only thing that will work is unobtainium


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## MN Driver (Sep 29, 2009)

Take a simple lightweight flywheel such as a computers hard drive. For a small device that is 3.5" wide running at 7200RPM that doesn't weight much, when holding it flat, try to twist it and notice the result. Now imagine a flywheel big enough to store energy in an application that encounters bumps, turning, and braking. Flywheels of any significant size to hold the energy to even get up to 30mph in a car could likely rip itself and the car apart. 100,000 RPM on a turbo works because of its very small diameter and light weight there isn't much energy stored in that actual rotating part and the real energy created is from the extra pressure going into the engine.


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## Duxuk (Jul 11, 2009)

Many people have assumed that the KERS systems in current F1 cars were a capacitor devices. Although the manufacturers are very secretive there is enough information out there to show that they are a flywheel device. OK they only give 80bhp for a few seconds per lap but the rules restrict their use. Maybe they could already give significantly more energy storage, and this is just the beggining. Racing improves the breed and developements will be rapid. The link to Williams in a response above tells little but says a lot!


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## Duxuk (Jul 11, 2009)

Mechanical systems capture braking energy and use it to turn a small flywheel which can spin at up to 80,000 rpm. When extra power is required, the flywheel is connected to the car’s rear wheels. In contrast to an electrical KERS, the mechanical energy doesn’t change state and is therefore more efficient.

This is taken from the Formula 1 website. Currently a KERS system (Kinetic Energy Recovery System) can give a power boost to an F1 car of 60Kw. From 2014 this will be increased to 120Kw. The durration is only, I think for 6 seconds per lap. That means the flywheel only needs to store ~ 100Wh of energy. This will double but clearly there is potential for much more. I'm sure that not all the stored energy is ever used up. 

If the F1 teams (only 3 teams use KERS) are using Unobtainium already which a coulpe of responants above have said would be neccessary, then I think I'll be investing a bit of money in the unobtainium futures market!

Surely if 3 F1 teams can acheive what has been done already in only 2 seasons, (KERS was not used in 2010) then this is an area for serious research. Please don't say that an idea is impossible when it's already out there and in use. A little knowledge is a dangerous thing.


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## Duncan (Dec 8, 2008)

_a small flywheel which can spin at up to 80,000 rpm

_The key word here is small*- *you were talking about a 1 meter flywheel at 100,000rpm
That's when you need unobtainium_

A little knowledge is a dangerous thing._ - especially if you wodge together a 1 meter flywheel and try to spin it up!

_If the F1 teams (only 3 teams use KERS)_ - 
Red Bull, Ferrari, McLaren, Williams and Mercedes definitely use KERS
And I'm pretty certain the other teams do as well

You may mean only three teams use a flywheel rather than capacitors - I think the leading teams use capacitors - certainly they seem to be very aware of working with high voltages.


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## Duxuk (Jul 11, 2009)

Excuse me. The effective centre of mass of a rotating flywheel scribes a circle. If the flywheel is a perfact cylinder then it needs to be 45cm diameter for the effective mass to travel 1 meter per revolution. If the mass is concentrated near the outer edge then this diameter can be reduced. I know that this might still cause you to question the feasabilty but if the technology was already fully developed there would be nothing to discusshere. My feeling is that this is an area for serious research and fortunately F1 has picked up the baton. Williams don't use KERS yet but are speculating that flywheels have a real chance for the future of transportation. Chemical batteries have been developing slowly in recent times but we would need a massive breakthrough if EVs using batteries are to be anything other than a side show. 

A flywheel would probably be best used by harvesting the energy as electricity rather than mechanically. The use of paired flywheels or a gimbal would cope with the gyroscopic effects. Also 2 paired flywheels could be slowed and speeded up relative to each other to turn the vehicle or even to propel it! Now that really is living in dreamland isn't it?


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## MN Driver (Sep 29, 2009)

"Chemical batteries have been developing slowly in recent times but we would need a massive breakthrough if EVs using batteries are to be anything other than a side show."

You might need to look around a bit, its fairly easy to make a 100+ mile car today. Not to mention production cars at over 200, future cars coming at 320, university conversion cars getting 300, and a small car at 350 miles. These cars have plenty of power with some conversions outperforming their original production specifications.

Sure a flywheel can store energy, but how much and how easy and practical is it to use? So far you are calling a proven technology that is still rapidly improving and calling it a slide show while taking a technology that can easily be disproven by physics as a viable primary mover for a vehicle and knocking what already works. You might get a small amount of gain from a regenerative application but you aren't going to match the storage capacity of a battery with a spinning disk, its easier to transfer the electricity directly to the wheels than to use electricity to spin up a flywheel and try to go somewhere with it lobbing around acting as a gyro changing vehicle handling dynamics and taking up a large chunk of space that would be difficult to engineer into a car.


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## Duxuk (Jul 11, 2009)

We are increasingly of the view that the use of chemical storage (in particular batteries) should be prohibited in Formula One owing to the unsuitability of the batteries currently available,” said Mosley in the letter

I think it may be worth watching the developement of flywheelenergy storage in Formula 1. From 2014 the smaller 1.6 litre 4 cylinder motors will be supplemented by 120Kw KERS systems. If you do the maths for a flywheel with a rotational speed of "upto 80,000rpm" as is stated in variuos reliable websites, then the flywheels need to be either quite heavy (many Kg) or have a significant diameter (50cm?).


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## Duxuk (Jul 11, 2009)

www.torotrak.com/pdfs/literature/*KERS*_CVT_brochure.pdf

Sorry to keep banging on about this but I think this brochure says a lot.


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## yosemitesamiam (Feb 7, 2012)

Didn't Porsche use this successfully in a Le Mans race? We need to contact them...they have all the unobtainium


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## Whitehawk (Apr 12, 2012)

Why does a FESS have to spin to 60,000 rpms? Can't a little bit larger diameter flywheel store the same energy at a fraction of those RPMs?

Back of napkin example, using 1 meter disc:
50kg disc, 1m diameter, I moment = 6.25

14,000kg vehicle traveling at 40 mph, has a potential 2,000 kilo-joules

To store that in the disc needs about 825 rad/sec, or 7,900 RPM


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## Ziggythewiz (May 16, 2010)

Do you realize how big 1m is in a car?


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## Whitehawk (Apr 12, 2012)

Ziggythewiz said:


> Do you realize how big 1m is in a car?


Look again, I didn't say car, I said 14,000kg vehicle.


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## Whitehawk (Apr 12, 2012)

Ziggythewiz said:


> Do you realize how big 1m is in a car?


Scaled down a bit, 2000kg CAR, 40-0 MPH in 10 seconds = 284 k-joules

25kg disc, 0.3 m diameter (1 foot), I = 0.28, req'd RPM, 13,500 RPMs.

Again, back of napkin calcs


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## Ziggythewiz (May 16, 2010)

Sorry, I thought we were still talking car applications.

I think in most cases batteries are still safer and more bang for the buck. Just like super caps, sure it's possible, but if you spend the same amount on batteries, or even a booster type pack like Jack R proposed, I think you'd get more benefit.

The reason for KERS in F1 was not to get power more efficiently, but to get more power without braking stupid rules.


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## Whitehawk (Apr 12, 2012)

Ziggythewiz said:


> Sorry, I thought we were still talking car applications.
> 
> I think in most cases batteries are still safer and more bang for the buck. Just like super caps, sure it's possible, but if you spend the same amount on batteries, or even a booster type pack like Jack R proposed, I think you'd get more benefit.
> 
> The reason for KERS in F1 was not to get power more efficiently, but to get more power without braking stupid rules.


=) I think you are very correct. The cost to R&D a kers for personal use would be very a big challenge, as well as home-brew ultra caps. Cheaper just to buy more lithiums.


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## Ziggythewiz (May 16, 2010)

Yeah, I'm not even talking about development costs. I think just the material cost if someone built it for you for free would be magnitudes greater than the cost/kWh of lithium.


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## mchp (Dec 28, 2012)

tomofreno said:


> Manufacturer flywheels used in vehicles:
> http://www.williamshybridpower.com]...wheels just to improve lifespan of battery...


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## Rrr (Nov 29, 2021)

Whitehawk said:


> Scaled down a bit, 2000kg CAR, 40-0 MPH in 10 seconds = 284 k-joules
> 
> 25kg disc, 0.3 m diameter (1 foot), I = 0.28, req'd RPM, 13,500 RPMs.
> 
> Again, back of napkin calcs


hi. and if we are talking about 200 KG box, 0-60 KMH in 10 sec... ?
and i want that "BOX" to work max 15 min...?
kg? diameter? rpm? k-joules?


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## brian_ (Feb 7, 2017)

Rrr said:


> hi. and if we are talking about 200 KG box, 0-60 KMH in 10 sec... ?
> and i want that "BOX" to work max 15 min...?
> kg? diameter? rpm? k-joules?


I doubt that the person you are asking is going to respond to a nine year old thread, using an account that hasn't logged in for over seven years.


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