# flywheel energy storage



## semipro (May 3, 2013)

A link to a story on an interesting flywheel energy storage design that is being scaled up to a size large enough for use in residential PV or wind energy systems.
http://www.gizmag.com/velkess-flywheel-technology-large-scale-energy-storage/27088/

Somewhat related; I've always wondered why energy couldn't be stored efficiently and inexpensively using a large weight that is lifted by a motor/generator. It would rise when energy was being stored and lowered when energy was being removed. Smaller versions of this idea are used for powering small lights and such.
http://www.indiegogo.com/projects/gravitylight-lighting-for-developing-countries

This might be a good use for an old silo or dug well?
I may have to make some calculations...


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## Delta-T (May 3, 2013)

I agree about the whole "weight storage" thing...I have always thought water as a good storage medium for gravity type energy generation. Even if its not terribly efficient, its pretty low tech, and low maintenance. On that subject...I think it was pop-sci (maybe pop-mechanics) had a piece about an led light powered by a weight, like a mechanical clock...lift weight and as it drops it makes 'lectricty, which powers the light...pretty cool.


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## semipro (May 3, 2013)

Well, I did the calculation.
Assuming I did it right if you raise a metric ton (1000kg, 2200lb) 10 meters high (about 30 ft.) you store only 0.027 kwh of energy. 
Hmmm.


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## Delta-T (May 3, 2013)

you had to use metric didn't you....


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## semipro (May 3, 2013)

semipro said:


> Well, I did the calculation.
> Assuming I did it right if you raise a metric ton (1000kg, 2200lb) 10 meters high (about 30 ft.) you store only 0.027 kwh of energy.
> Hmmm.


For a scale reference:
To store the same amount of power (1.46 kWh) as the 153 lb. NiMH battery in my Highlander hybrid I'd have elevate 59 tons to 30 ft.
That seems crazy.  Someone please prove me wrong. 
If I'm right I can see why this isn't a particularly good energy storage scheme.


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## semipro (May 3, 2013)

Delta-T said:


> I agree about the whole "weight storage" thing...I have always thought water as a good storage medium for gravity type energy generation.


Some power utilities do this with dams.  They pump water back (up) into reservoirs during low power usage times.


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## peakbagger (May 3, 2013)

Beacon Power got close on large flywheels but I think they went bankrupt after few commerical installations


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## Ehouse (May 3, 2013)

By converting to electricity and then to light (or pump) you lose something with each conversion.  You should be able to do better if you use direct drive.  Am I right that using a windmill to power a mechanical water pump is more efficient than going from wind to electric to pump?  Instead of wasting the potential energy of going up stairs, why not ride a platform down and lift a dumbwaiter full of firewood from your basement, or is that just dumb?


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## Flatbedford (May 3, 2013)

A few years ago a company wanted to use an abandoned quarry near me for a similar operation. They were going to pump water out during off peak times and then drain it through turbines during peak hours to generate electricity. The local people were afraid of the noise and construction traffic so it was squashed.


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## brian89gp (May 3, 2013)

semipro said:


> Some power utilities do this with dams. They pump water back (up) into reservoirs during low power usage times.


 
http://en.wikipedia.org/wiki/Taum_Sauk_Hydroelectric_Power_Station

http://en.wikipedia.org/wiki/Pumped_storage_hydroelectricity


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## woodgeek (May 3, 2013)

semipro said:


> For a scale reference:
> To store the same amount of power (1.46 kWh) as the 153 lb. NiMH battery in my Highlander hybrid I'd have elevate 59 tons to 30 ft.
> That seems crazy. Someone please prove me wrong.
> If I'm right I can see why this isn't a particularly good energy storage scheme.


 
The calculation sounds correct. This is why chemistry explodes and physics just breaks your toe.

Also, how high a hill can your highlander climb on the battery....


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## semipro (May 3, 2013)

woodgeek said:


> The calculation sounds correct. This is why chemistry explodes and physics just breaks your toe.
> 
> Also, how high a hill can your highlander climb on the battery....


I'm much more impressed by chemistry than I was before making that calculation. 
When you think about it, its pretty amazing how much energy is stored in batteries....and we're pushing for more.


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## begreen (May 3, 2013)

Flywheel storage was developing locally ten year ago. Still waiting...


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## velvetfoot (May 4, 2013)

peakbagger said:


> Beacon Power got close on large flywheels but I think they went bankrupt after few commerical installations


I think there's one near me.  No sure, but I think something  broke and they never fixed it.  Looking like a big waste of money for the ratepayers.


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## ewdudley (May 4, 2013)

Delta-T said:


> you had to use metric didn't you....


Oh all right, if you lift one gross stone up two rods it takes one thirtieth of a horsepower hour.


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## semipro (May 4, 2013)

begreen said:


> Flywheel storage was developing locally ten year ago. Still waiting...


I remember reading about flywheel storage in the 70s.  Issues to overcome included friction, exploding flywheels, etc.  What's innovative about this design is the self balancing capability and the flywheel tensile strength.  Its interesting they used hard drive supermagnets for the small scale model and that the magnets needed for a full scale version or too dangerous to work with by hand.


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