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A Beacon employee stands next to a complete flywheel storage system. Each system features 10 flywheels and can store enough electricity to provide 1 MW of power for 15 min (250 kWh).  (Source: Beacon Power)

Beacon Power plans on offering 20 MW (5 MWh) units to utilities for back up power and demand levelling purposes.  (Source: Beacon Power)
Volatile energy market fuels demand for energy storage

Rising gas prices haven't just been spurring the automotive market to change, they've also been taking their toll on utility companies, who have struggled with the tradeoffs of raising prices and customer dissatisfaction.  Now creative thinkers at Beacon Power, an interesting startup, have a solution that just might help utilities out.

Beacon Power produces a novel form of power storage in the shape of large carbon fiber flywheels, which spin at 16,000 revolutions per minute -- a surface speed of about Mach 2.  At one meter in diameter and 8,000 lbs, each wheel can provide 100 kilowatts of electricity for 15 minutes.

The company, led by CEO William Capp, is packaging 10 of the flywheels together to give an impressive power output of 1 MW and energy storage capacity of 250 kilowatt hours.  With the average household consuming approximately 8,900 kWh yearly, this would be enough to power a home for over 10 days.

The new technology isn't just about the high energy costs, either -- it can help provide backup power in case of a storm.  Utilities and businesses could adopt the devices to minimize interruptions to customers during storms or brownouts. 

On the environmental side of things, the device could complement intermittent power sources such as wind power and solar power, and use their stored output to avoid incurring extra cost or outages during periods of peak demand.

Says Capp, "These are used for fine tuning to keep everything in balance. The way it's done today is that a dispatcher sends a signal to generators...to increase or decrease output."

The device is extremely simple on a most basic level.  Adding electricity spins the wheel faster.  At any time this spin can be converted via a generator to power.  Over time, the wheel slows, but this is a very gradual process.  The technology is among the novel storage technologies being considered for use with alternative energy products.  Another promising technology is molten solar power, which stores solar heat in a briny fluid, for power production in nighttime hours.

However, the flywheels are more promising in a way, in that they can deal with daytime peaks as well.  Capp says that utilities will buy them to help them fulfill emissions restrictions regulations stating, "Rather than generating the power using fossil fuels, we'll be recycling the energy."

The company is marketing plans currently for 20 MW storage facilities, consisting of 20 one megawatt units.

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Carbon Fiber?
By lukasbradley on 6/18/2008 9:36:16 AM , Rating: 2
Any ideas as to why they are made of carbon fiber? Does it have something to do with resistance to static charge?




RE: Carbon Fiber?
By masher2 (blog) on 6/18/2008 9:44:35 AM , Rating: 4
Strength, I would imagine. The centripedal force on the edge of a 4 ton wheel spinning at Mach 2 is tremendous.


RE: Carbon Fiber?
By aBott on 6/18/2008 9:48:27 AM , Rating: 2
Yay! You said centripetal and not centrifugal!


RE: Carbon Fiber?
By rdeegvainl on 6/18/2008 12:11:22 PM , Rating: 5
RE: Carbon Fiber?
By Pudro on 6/18/2008 3:57:05 PM , Rating: 3
I really don't get what is so wrong with talking about centrifugal force. It is a real thing - it just only exists in a rotating frame of reference and it doesn't fit the strictest definition of a "force".

It's just a term that simplifies discussing and calculating physics. There are so many different ways this is always done in physics, yet centrifugal force is the only one to catch all of the crap. I guess it makes people feel smart or something.

Why doesn't everyone get all uppity when a space-related article mentions astronauts in "zero G" or "weightlessness"?


RE: Carbon Fiber?
By wordsworm on 6/18/2008 5:48:00 PM , Rating: 2
quote:
Why doesn't everyone get all uppity when a space-related article mentions astronauts in "zero G" or "weightlessness"?


Maybe it's because if everyone said 'free fall' nobody would want to become an astronaut?


RE: Carbon Fiber?
By djc208 on 6/18/2008 9:47:03 AM , Rating: 3
It's usually due to issues with the integrity of the rotor. At 16,000 rpm the centripital force is huge and the rotor wants to fling itself apart, at which point it would become shrapnel. So making sure the rotor can withstand the spin is vital.

Plus I'm sure it sounds cooler than saying they've attached a bunch of metal disks to a motor/generator then asking for a couple of hundred grand each.


RE: Carbon Fiber?
By Adonlude on 6/18/2008 2:01:14 PM , Rating: 3
Wow, I had no idea that capacitors such as this even existed. Storing energy as kinetic motion instead of simply setting up E or B fields (capacitor or inductor, but almost always capacitor) is quite novel.

The biggest factor must be heat loss in whatever kind of "bearings" this disk or its shaft is rotating on. They must have spent tons of time determining the perfect mass/RPM ratios to get the highest efficiency out of the "bearing" system. Apparently they came up with a very high RPM that required a light, strong material like carbon fiber that wouldn't fly apart. Very cool!


RE: Carbon Fiber?
By kenferg1 on 6/18/2008 7:15:32 PM , Rating: 2
There was an engineer a few years ago that used a small gas turbine coupled to a flywheel sealed in a vacuum. The turbine generated electrical power that spun the flywheel. The flywheel stored the energy in order to release it on demand to a generator that drove the wheels. He had backing from financiers but had issues with the vacuum contained flywheel. It was cool technology, but never got off the ground.


RE: Carbon Fiber?
By ElFenix on 6/19/2008 1:18:28 AM , Rating: 2
it's not a capacitor. it's a big spinning wheel. they're used all over the place. those roller coasters that launch from a dead stop rather than being pulled up a hill typically use flywheels to build up the energy used to launch the coaster. one of the car companies (i think chrysler) was experimenting with a flywheel hybrid back in the mid 90s.


RE: Carbon Fiber?
By Hawkido on 6/20/2008 12:50:52 PM , Rating: 2
quote:
I had no idea that capacitors such as this even existed.


See Landini Tractor:

http://en.wikipedia.org/wiki/Landini_%28tractor%29

Flywheels have been used to store energy between engin strokes all the way back to the steam engine.


RE: Carbon Fiber?
By drank12quartsstrohsbeer on 6/18/2008 9:54:45 AM , Rating: 2
fatigue resistance, most likely.

hopefully those closed containers mean that they pull vacuum on those containers when the wheels are spinning.


RE: Carbon Fiber?
By mattclary on 6/18/2008 10:04:10 AM , Rating: 2
That's a really good question. It seems like you would want a wheel with lots of mass. It would take more power to spin up, but once it gets to speed will take longer to slow down.


RE: Carbon Fiber?
By masher2 (blog) on 6/18/2008 10:12:09 AM , Rating: 3
From eyeballing the units, I would imagine the flywheel itself is made of carbon fiber, but is internally lined with lead or some other dense material. Otherwise, I don't see the volume being large enough to contain a four ton flywheel, along with all the other necessary apparatus.


RE: Carbon Fiber?
By codeThug on 6/18/2008 6:23:10 PM , Rating: 2
If it's spun fast enough can it fold space?


RE: Carbon Fiber?
By Mitch101 on 6/19/2008 10:24:00 AM , Rating: 2
Possibly however if you conected a bunch in series and they spin at 88MPH you travel back in time.


RE: Carbon Fiber?
By bohhad on 6/22/2008 2:14:59 AM , Rating: 2
only if it can feed 1.21 jigawatts to the flux capacitor


RE: Carbon Fiber?
By guacamojo on 6/18/2008 10:23:38 AM , Rating: 2
What's really needed is high strength and high rotational inertia, not mass per se.

The formula for energy stored in a flywheel is 1/2 I w^2, where I is the inertia of the wheel, and w is the rotational velocity (radians per second, although you can convert that to RPM easily enough.) So the inertia is important, but the speed is even more so, because of the squared term.

Carbon fiber has among the highest strength to weight characteristics of modern materials (okay, diamond is better ...) so that alone means that you can spin the hell out of the flywheels.

Most flywheels have a thick rim and relatively thin spokes connecting to a central bearing hub. These flywheels may or may not have a center hub, depending on how the support bearings are set up. They could be running gas bearings on the rim itself, maybe on the OD, where they would naturally put a compressive stress on the rim and act to help hold it together at speed.

Interesting technology.

On a side note, I remember flywheels like this (but smaller and faster) being proposed for automotive applications. There were some really interesting problems to tackle with precession (a 20k rpm flywheel makes a hell of a gyroscope... picture a car that won't turn or pitch up and down...)


RE: Carbon Fiber?
By Solandri on 6/18/2008 1:02:14 PM , Rating: 2
quote:
The formula for energy stored in a flywheel is 1/2 I w^2, where I is the inertia of the wheel, and w is the rotational velocity (radians per second, although you can convert that to RPM easily enough.) So the inertia is important, but the speed is even more so, because of the squared term.

Well, moment of inertia (inertia of rotating bodies) goes as m*r^2 for a thin ring, so the radius of the thing is just as important. IIRC, tension in a thin rotating ring is proportional to the centripetal force, which goes as v^2/r. So tension increases in proportion with rotational velocity (and energy), but actually decreases the more you increase the radius. So the best design direction to maximize energy but minimize forces is to maximize radius.
quote:
Carbon fiber has among the highest strength to weight characteristics of modern materials (okay, diamond is better ...)

Diamond is better in compression, but not in tension. This is true of pretty much any ceramic or crystal.
quote:
On a side note, I remember flywheels like this (but smaller and faster) being proposed for automotive applications. There were some really interesting problems to tackle wi