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Flywheels energy storage?

Peskanov

Critical Thinker
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Joined
Dec 30, 2002
Messages
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There is a lot of info about hydrogen (as fuel for vehicles) on the media lately. Usually, experts reckon hydrogen is only a form of energy storage, because hydrogen has to be synthesized using more energy.

My question is, why is hydrogen a better energy storage?
What happens with common batteries? Too much weight, or maybe too contaminant?
And, what about flywheels? Flywheels are clean, have large storage capacity and slow energy leaking times...

http://www.wikipedia.org/wiki/Flywheel_energy_storage

Plus, chemical batteries and flywheels have an extra advantage, you can combine them with solar pannels.
When a car is parked, solar pannels can refill batteries or flywheels.
And the biggest advantage: electricity is avalaible eveywhere, no nedd to develop a huge network of hydrogen synthesis/distribution...

Opinions?
 
Many of your questions were brought up in the recent fuel cell thread.

Regenerative fuel cells can also be recharged with solar or electric input.

Batteries - many kinds of batteries use toxic metals and caustic acids, and so present long term disposal questions. Weight is an issue as is power density. Current electric cars are lucky to go 100 miles or so.

Mechanical flywheels - energy density and safety would be issues. To carry more energy, they have to spin at higher velocity or be heavier.

The interest in hydrogen fuel cells lies in the presumption that the technology can be improved to make it more practical. To make that happen, ways must be found to store more hydrogen in a reasonable space. This could mean dealing with high pressure.

One possible advantage of hydrogen over battery systems is recharge time. It seems likely that a tank could be refilled with hydrogen more quickly than a batter could be recharged.
 
Isn't there a gyroscopic precession issue with flywheels? I can imagine a big flywheel whizzing round, say with a vertical axis. Any sudden pitching movements by the vehicle would make it roll to one side. I suppose two contra-rotating flywheels would cancel the effect out.

ceptimus.
 
ceptimus said:
Isn't there a gyroscopic precession issue with flywheels? I can imagine a big flywheel whizzing round, say with a vertical axis. Any sudden pitching movements by the vehicle would make it roll to one side. I suppose two contra-rotating flywheels would cancel the effect out.

ceptimus.
Click to expand...

That works, but you have an enormous torque on both of the flywheel bearings in such cases. It also doesn't quite cancel out, since there is space between them. In a rigid object, I think they mostly cancel, but consider, if you're turning, the radius is different for the inside and outside flywheels, yes?
 
ceptimus said:
Isn't there a gyroscopic precession issue with flywheels? I can imagine a big flywheel whizzing round, say with a vertical axis. Any sudden pitching movements by the vehicle would make it roll to one side. I suppose two contra-rotating flywheels would cancel the effect out.

ceptimus.
Click to expand...
They would be centered at two different points on the axis, so you would still have torque issues.
 
ceptimus said:
Isn't there a gyroscopic precession issue with flywheels? I can imagine a big flywheel whizzing round, say with a vertical axis. Any sudden pitching movements by the vehicle would make it roll to one side. I suppose two contra-rotating flywheels would cancel the effect out.

ceptimus.
Click to expand...
Mount the wheel in a free-floating gimbal framework. It will be able to continue pointing "axis up" even if the vehicle frame rolls or pitches around it.
 
AP:
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quote:
Many of your questions were brought up in the recent fuel cell thread.
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I did a search previously, but I did miss any interesting reference to flywheels.

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quote:
Regenerative fuel cells can also be recharged with solar or electric input.
----

That's news to me, that makes them much more interesting. How does it work? If we plug the cell to an electric source and add water, is hydrogen produced?
It sounds quite complex, feed electricity, water, and compress hydrogen back into the tanks...

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quote:
Mechanical flywheels - energy density and safety would be issues
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I found this link which tells more about the matter:

http://www.ott.doe.gov/hev/flywheels.html

However, I still fail to see the problem. After all, carrying gasoline in a combustion driven vehicle is also dangerous.
I guess the flywheels could be packed inside a cover of light weight, high resistance foam material.
I believe there exist some carbono based foam which is both very hard and light, developed by the US army.

garys_2k,
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quote:
Mount the wheel in a free-floating gimbal framework. It will be able to continue pointing "axis up" even if the vehicle frame rolls or pitches around it.
----

Is that necesary? I think we only need to align the flywheels with the wheel's axis. To avoid excesive torque just put two of them in opossite spins. Cars don't rotate to much in this axis, just a bit in ups and downs.
 
I think I've seen mention of flywheels for storing small amounts of energy, such as in regenerative braking. Using them to store energy for a long trip (300+ miles) would be quite another matter.

Regenerative fuel cells:
http://www.llnl.gov/str/Mitlit.html
http://www.fctec.com/fctec_types_rfc.asp
The highest profile application was in the Helios high altitude unmanned vehicle, where it would be used to store energy from solar panels: http://www.space.com/businesstechnology/technology/helios_sn_030624.html
Helios is an unusual vehicle in that is a slow high altitude vehicle, so has a large wing surface which can be used for solar panels. The cargo capacity is low relative to vehicle size. The electrolysis unit and fuel cell together should be compared to batteries for capacity, efficiency and weight. I don't know the numbers.
 
My physics is kind of weak, but would there also be torque problem when trying to draw the energy off of the flywheel quickly - which would be necessary when leaving traffic lights?
 
Ladewig said:
My physics is kind of weak, but would there also be torque problem when trying to draw the energy off of the flywheel quickly - which would be necessary when leaving traffic lights?
Click to expand...

Not really. Don't confuse force with power - it takes just as much force to accelerate from a stop as it does to accelerate while you're already going fast, but a lot less power. Gasoline engines have poor torque at low speeds, which is why many people think that starting at a traffic light demands high performance. But electric motors can provide full torque even at low velocities. Starting from a stoplight is actually what they're best at, since the energy required isn't that great. So assuming that the flywheel is coupled to a generator which in turn drives a motor (rather than some kind of mechanical connection), that shouldn't be a problem at all. I think the much bigger problem with flywheels is trying to overcome decay times - how fast does the flywheel lose energy from friction?
 
¡Pero, casi todo de ese sitio es en Español!

And since that sentence is about the limit of my comprehension of Spanish, it's not much use to me.
 
One hurtle for flywheels has been containing the pieces in an accident; when it breaks up, it's just like a bomb going off. Not sure if they use kevlar now or what they might have done about it.
 
rwald said:
¡Pero, casi todo de ese sitio es en Español!

And since that sentence is about the limit of my comprehension of Spanish, it's not much use to me.
Click to expand...

I got almost all of it in english (I really uderstand not a word of spanish!)
 
All of the links across the top are in English ("The Engine," "The Car," "Further applications," etc.). However, any other link you try ends up in Spanish.
 
Not really. Don't confuse force with power - it takes just as much force to accelerate from a stop as it does to accelerate while you're already going fast, but a lot less power. Gasoline engines have poor torque at low speeds, which is why many people think that starting at a traffic light demands high performance. But electric motors can provide full torque even at low velocities. Starting from a stoplight is actually what they're best at, since the energy required isn't that great. So assuming that the flywheel is coupled to a generator which in turn drives a motor (rather than some kind of mechanical connection), that shouldn't be a problem at all. I think the much bigger problem with flywheels is trying to overcome decay times - how fast does the flywheel lose energy from friction?
Click to expand...

Thanks. I was thinking that if the flywheel were a measureable percentage of the car's weight, then trying to draw a lot of energy off it would make the car want to twist or rotate in the opposite direction. I was imagining a mechanical transfer of energy. Your solution is much more appropriate. I really should have thought of it because I drive a Honda Insight.
 
BTW, I forgot one of the best advantages for flywheels. Flywheels, unlike batteries, can be charged at any speed. This means you can obtain energy from braking, and store it in the flywheel. Very economic for city cars...

Ziggurat:
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quote:
I think the much bigger problem with flywheels is trying to overcome decay times - how fast does the flywheel lose energy from friction?
----

Take a look at the wikipedia link I posted at the top of this page; current flywheels spin in a vacuum chamber, and the axis levitate over magnets. It can store energy for years!


jimmerson,
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quote:
Chrysler had a racecar with flywheel energy storage.

http://www.rqriley.com/sld010.htm
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Whoa! That's really cool stuff! Using a turbine to get the maximun energy from fuel, and storing it in a flywheel!
That article also covers the problems with flywheels, security and torque:

"A flywheel, however, is a very testy device. The biggest problems, aside from high costs, are the gyroscopic effects of the rotor, and the effects of the sudden release of energy on rotor failure. Gyroscopic forces, if they are not correctly oriented, are enough to cause a vehicle to roll over in a turn, and the flywheel has to be well protected from road shocks. The energy released during the failure of a 1 kW-h flywheel is enough to lift a mid-size car 100 feet into the air."

Does not sound nice...
In the same article, I found also info about a technology I was totally unaware:

"Ultracapacitors are another high-tech storage device that should be much more benign than a flywheel. Both ultracapacitors and flywheels can accept and deliver energy many times more rapidly than a battery"

It sounds a bit like superconductor batteries; does anybody know about Ultracapacitors?
 
Peskanov said:
BTW, I forgot one of the best advantages for flywheels. Flywheels, unlike batteries, can be charged at any speed. This means you can obtain energy from braking, and store it in the flywheel. Very economic for city cars...
Click to expand...
The three hybrid vehicles I know off already charge batteries from braking, at any speed.

Walt
 
Walter Wayne said:
The three hybrid vehicles I know off already charge batteries from braking, at any speed.
Click to expand...

I drive one of them: the Honda Insight

I get about 55mph city/county. Getting onto a highway heading up a hill can be a bitch, but maybe I'm just used to more powerful cars.

Sitting in the hot sun on very hot days can cause it's battery to drain down to a very low level. When that happens you have to drive it for 5-10 minutes til the battery is charged up enough that it assists the engine. Until that happens, you're relying entirely on the gas engine.

Other than that, handles well.
 
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