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Using Flywheels to Meet Peak Power Grid Demands
hackertourist writes "A novel type of electricity storage was recently added to the New York power grid. The unit, supplied by Beacon Power, uses flywheels to store energy. This system is intended to replace gas turbines in supplying short-term peaks in power demand (also known as frequency regulation). It can supply up to 20 MW, using 200 flywheels."
If you can't afford a 200-flywheel system, you can always get a racetrack-ready Porsche 911 GT3 R Hybrid, which has a single energy-storage flywheel that can give you a 160 HP burst of power when you need a little extra oomph.
From the article: Beacon Power's spinning flywheels, which are made of carbon fiber and levitated in a vacuum by magnets, absorb energy from the grid and discharge 1 megawatt for as much as 15 minutes
Dumb question, I suppose. But, given that the earth rotates, and given that the flywheels will have a huge angular momentum, are they gimbaled? The article says they're suspended in a vacuum, levitated on a magnetic field, which is cool. But if they're not gimbaled a huge amount of energy will be wasted fighting precession as the earth rotates.
I assume the people making these things are smart and know their shit. I'm just curious how a problem like this is solved. If not gimbals, what?
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Why don't these alternative energy/power storage articles ever include cost comparisons? What do these flywheels cost to buy and operate compared to what they're replacing?
In the case of these things, there seem to be many small ones (less risk if one "escapes") and something tells me that carbon fiber disks that are carefully stabilized and levitated in a vacuum while spinning incredibly fast...would break into a thousand pieces the second they left containment rather than rolling down the street and through someone's house.
Bottles.
Also in use in vehicles since the 50's.
http://en.wikipedia.org/wiki/Gyrobus
Rather than carrying an internal combustion engine or batteries, or connecting to overhead powerlines, a gyrobus carries a large flywheel that is spun at up to 3,000 RPM by a "squirrel cage" motor. .... ... ...
Fully charged, a gyrobus could typically travel as far as 6km on a level route at speeds of up to 50 to 60 km/h,
Charging a flywheel took between 30 seconds and 3 minutes;
Sounds nicer than most electric cars.
The Coriolis effect is far too small to have any significant impact on flywheels this small, it only really has an effect on large scale systems such as cyclonic storms and even then it's amplified due to the proximity to the equator.
I reject your reality and substitute my own.
The JET tokamak has had a couple of huge flywheels to provide the power to its field coils since the early 1980s, and those are around 400MW peak output. True the pulse only lasts around half a minute or so, but it's still very impressive. Each flywheel has a moment of intertia of something around 14 million kgm^2. This may not even be that relevant to TFA but I thought it might be interesting.
An intriguing solution to a problem that should never have existed in the first place...
At present only industrial customers pay different rates for their electricity based on the time of day. Domestic electricity prices are constant all day. There is no incentive for anyone to defer their power consumption to off-peak hours, or to invest in any technology to smoothen out their power consumption curve. If we pay one price for the day time electricity and get a deep discount for the night time electricity, these fly wheel storage devices can be used to soak up energy at night and use it during the day. Since most of the day time power consumption is air conditioning, we could simply make ice/chill water at night and use it to cool the home during the day.
sed -e 's/Chuck Norris/Rajnikant/g' joke > fact
..but there was a lot of NIMBY paranoia about flywheels breaking loose and roaming the countryside.
God, am I the only one who wants to live in a world where this actually happens and you see a bunch of ME's from the power plant with yellow hard hats on sprinting after it yelling "Shit-shit-shit-SHIT! -*crushes car* - SORRY! - shit-shit-shit-shit!"
The efficiency of an electric motor can be in excess of 90%. Energy is transferred to a flywheel via electric motor, and extracted (mostly likely) through the same electric motor, so your maximum theoretical efficiency is going to be your motor efficiency squared. If they tried hard, probably something like (92%)^2 or something like 85% total storage efficiency.
This is of course assuming that mechanical losses are zero, but given the design they are very likely to be close to perfect. There will also of course be some energy lost indirectly in levitation/cooling/ohmic stuff outside of the flywheel.
I think the thing about this article that bugs me the most is they say that the flywheels can store 20MW. What on earth kind of way to measure an energy storage device is that? 20MW for 0.5 seconds? 20MW for three days? Embarrassing.
One of my physics teachers at school used to work in a power station for a bit. He showed us some pictures of a 'fuse' that they used. When I think of a fuse, I think of a small, thin, piece of wire. This was a large copper bar. He also had some pictures from when it blew - the entire bar was vaporised. When people talk about MWs and GWs, the numbers don't seem real. When you see lumps of copper being instantly turned to gas, you get a real feeling for the amount of power involved.
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My worry isn't rolling stones, it's shrapnel. Beacon Power's flywheels store 25 kwh of electrical energy. If the rotor fails, this energy will be released in a fraction of a second, causing an explosion with the same energy as 20 kg of TNT. But TNT releases most of its energy in the form of heat, which is imperfectly converted to kinetic energy, while the flywheels will release pure kinetic energy. And it's kinetic energy that kills people. You'd better hope the engineer who designed the metal casing for the flywheel knew what he was doing!
That average energy consumption isn't just electricity. Average electricity per person is just 1460 W for the US, which is what this system is for.
If memory serves, the giant flywheel that MIT uses to spark their fusion test reactor is rigged with explosive charges to blow it to pieces if it ever came loose. I believe the calculations show that without detonating it, it would likely continue *through* several buildings before landing in the Charles River... could have been an urban legend though.
No, TFA is confusing statistics of individual flywheels with clusters of them. The individual 25 kwh flywheels are grouped into modular clusters of 10: each of these 10-unit modules delivers 250 kwh (1 MW for 15 mins), and is the size of a couple of cargo containers. See this white paper from the manufacturer.