Flywheel Energy Storage.

[Ivan]

I don't imagine they are cheap, but these things look good as an alternative to battery storage. http://www.vyconenergy.com/pdfs/vycon_overview_bro.pdf

I spoke to a manufacturer a few years ago, and they reckoned 2% loss of energy over 24hours - so not good for long term storage, but great for ironing out demand/production and perhaps to buy/sell electricity.

[Adam]

I just cant see them storing much power, they just don't seem large enough to have a large mass rotating inside them

However they could solve my friend's problem, he's a metal fabricator and runs a generator for 3phase (nearest mains 1mile away) he has to run a larger than nessacery generator just so cope with surge loads (motor starting).

He is on building his workshop and has installed underfloor heating under 9" of concrete and will be connecting to the generator via engine water jacket and exhaust heat exchanger, he will also install an second hand bulk milk tank (has excellent insulating propities) with heating elements inside to keep the generator under load to store hot water for over night and periods when the generator is not running.

Bacck to topic I could see these units bieng used in cars/trucks ect for when they are in traffic, stop/start situations.

[northern installer]

I came across a flywheel motor generator many years ago ,on an early computer installation,the whole of the computer room power was derived from a motor driven alternator around 20 kva,with a large flywheel built in;in normal operation,it smoothed and isolated the supply from mains variations,on mains failure the flywheel held up long enough on load to enable the auto-start genset to start and warm up,and absorbed the changeover outage;a dinosaur by todays electronic standards,but state of the art then,and very reliable.Modern versions I think ,must rely on high rpm to achieve a compact installation.

[Gary T]

For a comparison of available electrical storage technologies see the web site of the electricity storage association

http://electricitystorage.org/tech/technologies_technologies.htm

There follows an artical about Beacon Power - who have just been apointed to supply a 20 Mw storage project to New York

http://phx.corporate-ir.net/phoenix.zhtml?c=123367&p=irol-newsArticle&ID=1147716&highlight=

For very brief start up support, super-capacitors - otherwise known as ultra-capacitors may be a better option than flywheels, especially now they can be bought off the shelf as high voltage modules.

http://www.maxwell.com/ultracapacitors/products/modules/bmod0063-125v.asp

[Ivan]

Any idea of the supercapacitor prices?

The beauty of the flywheel is that it is unaffected by total discharge cycles (but the ultra capacitors look good in that respect too).

Yes, the flywheels store a reasonable amount of power. One unit is 10 or 20kWh. I guess they are about the size of an oil drum. It's an interesting technology, to say the least...

[wyleu]

63 Farads ! .... 

[Gary T]

I managed to find prices from a US supplier

http://www.prestostore.com/catalog.php/tecategroup.com/pd359703

They quoted a 165 Farad 48.6 volt ultracapacitor module at around £1100. This will store around 7500 joules, and will allow a discharge power of the order of 2-3kW for about 3 or 2 seconds reqpectively.

500 farad 16 volt comes out at around £400 with 8000 joules stored energy.

3000 Farad 2.7 volt capacitors were quoted at around £60, with each capacitor storing 8100 joules. It would seem therefore, that much of the cost is in the electronics to balance the capacitors in a module rather than in the capacitor itself, and the cost rising with increasing voltage of module. It may make sence to store energy at low voltage, and use power electronics to step the voltage up or down.

These capacitors have a design life of 1000,000 cycles so ideal for momentary high power requirements frequently repeated

[charlieb]

I just got back from the Energy Storage Association meeting funnily enough. These low(ish) tech flywheels are basically designed to fill in the 2-3 second gap between a grid failure and a backup diesel or gas generator kicking in. They can do that and a bit of voltage support pretty well (surge load support could be a great application). But they're not going to be much good for onsite renewables smoothing - not on their own anyway.

The Beacon technology is clever - and their business plan even more so. They're really heavy composite flywheels so store more energy (up to 15 minutes discharge apparently). Their plan is to play on the Frequency response markets (second by second system balancing) operated by the likes of National Grid- where peak buy prices for electricity can be huge and you can be paid do absorb electricity.  Looks like that system in NY might actually get built, but just pretty drawings so far..

THere's lots of other funky storage ideas out there. Compressed air also interesting. And Lithium Ion / Sodium sulphur...

C

[KenB]

Gary, List,

I'm using a tiddly 0.22F, 5.5V super capacitor in a new product.

The energy stored is 1/2 C V2 so about 3.3 J per capacitor.

We are paying $0.32 each for them.

That suggests you can get 10 joules for a dollar, this makes the 48.5V 165F ultracapacitor seem a bit expensive?

I wouldn't want to solder several thousand of them together though. 


Ken

[Gary T]

I know the 48v modules look expensive at around 2 joules per $, but that is because the other components and the balancing costs make up a substantial part of the total cost. Using a single 3000 farad 2.7 volt capacitor, you get more like 30 joules per $.

Please halve the energy quoted in my previous post as I used the wrong equation for my calculation.

[NickW]

I don't imagine they are cheap, but these things look good as an alternative to battery storage. http://www.vyconenergy.com/pdfs/vycon_overview_bro.pdf

I spoke to a manufacturer a few years ago, and they reckoned 2% loss of energy over 24hours - so not good for long term storage, but great for ironing out demand/production and perhaps to buy/sell electricity.

Aha - flywheels could be a more benign use for depleted uranium

Seriously - at 17 times the density of water a lage lump of DU spinning round at several thousand RPM should store a fair bit of power!

[Ivan]

how soft is DU? I've always imagined it would be soft like lead. Might need to be built into a steel or titanium framework to provide the strength. Has anyone ever tried using lead in a flywheel. Almost all I have seen are brass or steel, whereas even commonal garden lead would be a significant improvement.

[Gary T]

      Ivan, there are two types of energy storage flywheel.

The first are heavy, and rotate at relatively low speed with relatively low energy density, and have been around for many years. These are rather large, and experience significant wear.

The second more modern type are high speed flywheels using very high strength light weight rotors made of things like advanced ceramics, or carbon fibre. These spin in a vacuum at tens of thousands of RPM, and are suspended between magnetic bearings like a mag-lev train. As such, these flywheels have very little wear, very low energy losses, and store energy at a high density. As energy stored is proportional to mass, and to the square of rotational speed, it is better to double the rotational speed rather than to double the weight of the rotor.

As an aside, one of the possible reasons why so few flywheel energy storage systems are in use may be that very similar technology i.e. centrifuge rotors made in the same manner, and spun in a vacuum suspended on mag-lev bearings can be used to separate Uranium isotopes for a nuclear weapons program!

[NickW]

It must be a lot harder than lead which is why it was used instead of tungsten in armour piercing rounds. THe 30mm rounds used on the A10 are sabot rounds - so the penetrator is DU.  Steel shatters above about 4000 fps and is relatively light. Lead would be as much use as plasticine against tanks.

[Gary T]

Pure Uranium has rather low strength, but alloyed with between 4 and 35% Tungston or Titanium, strong alloys can be prepared. Still, such an alloy would have a far lower strength, and consequently rotational speed than carbon fibre, so would not store as much energy per Kg.