back to article Flexible flywheel offers cheap energy storage

Mechanical engineering isn't within the scope of Vulture South, so we'll welcome readers' input about whether this is genius or snake-oil: a Kickstarter project called the Velkess Flywheel hopes to offer low-cost energy storage. Flywheels are good at storing energy, but building them to fine mechanical specifications can get …


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  1. Flash_Penguin

    Dynamic Balancing already exists

    This is interesting because the ability of a flywheel to store energy is already proven.

    Something that deforms will tend to balance if it can deform far enough.

    4x4 guys are using dynabeads to dynamically balance tyres that are covered in crap, and it can react to a change in the state of the tyre too.

    Maybe manufacture a flywheel with a hollow section so they can use beads to balance the wheel?

    1. Eddy Ito

      Re: Dynamic Balancing already exists

      So if beads will self balance, the off the top of my head it seems to make sense to use a liquid as the major component and water is fairly cheap. Since it's going to be inside an evacuated housing it reduces the danger of a catastrophic failure since some portion will change phase and the liquid will act as a buffering medium for any flying shards from the rotating container that aren't on the outer edge and first to impact. I'm fairly sure there must be reasonable flaws to the idea but nothing comes immediately to mind.

      1. Yet Another Anonymous coward Silver badge

        Re: Dynamic Balancing already exists

        The energy stored in a flywheel all depends on storing a lot of mass at the outer edge of the rim, water probably isn't heavy enough. Mercury or molten lead would be good - but might have their own problems

        1. bazza Silver badge

          Re: Dynamic Balancing already exists - FLAW

          If the rotor is flexing as it spins then that will absorb energy. Not a problem on a 4x4, you're driving. But in an energy storage device they will be throwing energy away into heating up the rotor as it flexes.

          So the question is, does it flex continuously, or does it settle into a shape and stay in that shape? If the latter then only a small amount of energy will be lost. If the former (which I suspect will be the case), then it won't work very well.

          Using a fluid as the weight is a bad idea for the same reason - energy will be lost in stirring (thus heating) the fluid. And that will be a continuous loss, not a one-off as it settles into shape.

  2. GrantB


    Not sure if this is particularly good or not.

    Low tech Lead Acid batteries are good for about 40Wh per kg. So 340kg of lead acid batteries would seem to give a similar amount of storage (~14 kWh) without even looking at other battery tech like Lithium-ion which is far better. I know flywheels have been trialled as storage for bus's etc, but there is always the scary issue of having to deal with the potential for a flywheel to disintegrate following an impact. Not sure from the description how much this is an issue for the deforming flywheel.

    Existing battery technology obviously have life-cycle/recharge issues, but new tech like like this flywheel have a habit of not competing with existing technology in the real world due to maintenance and production issues.

    Still would love to see if they scale up - I think there is a place for very big (ferris wheel sized) flywheels to absorb wind/solar PV energy and release it. Can this tech scale to store MWh?s Would be cool to see.

    1. Malcolm Weir Silver badge

      Re: 15KWh?

      My take is that the 15KWh figure was selected precisely because it is the same sort of storage density as lead acid batteries; given the choice, a kinetic energy store is preferable to a chemical one, simply because of the toxicity of the latter.

      1. Naughtyhorse

        Re: 15KWh?

        My take is that the 15KWh figure was selected precisely because it is the same sort of storage density as lead acid batteries; given the choice, a kinetic energy store is preferable to a chemical one, simply because of the toxicity of the latter.

        My take is that the 15KWh figure was selected precisely because it is the same sort of storage density as lead acid batteries; given the choice, a chamical energy store is preferable to a kinetic one, simply because of the tedium of spending all morning pulling bits of a busted flywheel out of ones face.

        potato poe-tah-to i guess

        there fixed it for you.

        1. Michael Wojcik Silver badge

          Re: 15KWh?

          simply because of the tedium of spending all morning pulling bits of a busted flywheel out of ones face [and other tiresome comments to this effect]

          Right, what we need is a perfectly safe energy storage system. Oh, wait, there isn't one, because the point of an energy storage system is to store energy. Any time you have a sharp energy gradient, you have the potential for a Bad Thing. Talking about uncontrolled energy release in qualitative terms, rather than quantitative ones, is just handwaving.

          1. Anonymous Coward
            Anonymous Coward

            Re: 15KWh?

            > Right, what we need is a perfectly safe energy storage system.

            There is safe and then there is a 340kg flywheel spinning at somewhere between 15,000 to 30,000 rpm (or even more).

            This will have the same energy potential as 13kg of TNT and if it goes wrong it will release all of that energy in an instant. The energy discharge gradient will be vertical, just like TNT.

            A battery storage system will not be able to release the stored energy instantly because the speed of discharge is limited by the speed of the reaction within the batteries. It might overheat and catch fire, but it will not be an explosive event.

    2. BristolBachelor Gold badge

      Re: 15KWh?

      You can actually buy UPSs that use this tech. The tend to have much lower running costs than battery which always tend to have a small leakage current. Also there are no annual maintenance and battery swap-out issues.

      The ones I've seen are multi kWh, but are normally specified to operate in the deadtime that it takes a diesel generator to spin-up and get to temperature (~1 min). They too run the flywheel in a vacuum, and use a SR motor/generator combo. I saw them put in in a remote location because maintenance was going to be an issue (but as the primary back-up without generator). Another remote location had the same type of set-up, but fuel-cell. THe fuel-cell was very nice in that it jsut sat there doing nothing until needed. The down-side was a life of about 1000 hours on the membrane.

      1. Anonymous Coward
        Anonymous Coward

        Re: 15KWh?

        > The tend to have much lower running costs than battery which always tend to have a small leakage current.

        The leakage for a battery is approximately 5% per month. The leakage for the flywheel is 2% per day. That alone is enough to increase the running costs. The 2% per day might well be higher since people looking for funding tend to be optimistic with their calculations.

        1. Wize

          Re: 15KWh?

          Thinking of the mess these things would make if there was an accident (if, say, used in a vehicle).

          Those who watched Robot Wars may be familiar with a competitor called Hypno Disk. They used a flywheel which rendered many a solid construction to a pile of twisted metal.

          This is an industrial sized version. Mounting one in a car or bus would be asking for trouble.

          1. Euripides Pants

            Re: 15KWh?

            "Thinking of the mess these things would make if there was an accident (if, say, used in a vehicle)."

            Cars have had flywheels inside them for about a century now...

            1. Anonymous Coward
              Anonymous Coward

              Re: 15KWh?

              Car flywheels are only there to maintain the torque between piston firings. They typically weigh less than 10kg and only turn as fast as the engine.

              The flywheel in this weighs 340kg and will spin at least one order of magnitude faster than a car flywheel (I could calculate it based on the flywheel size and 15kWh of energy stored but its late and I need sleep).

          2. cortland

            Re: 15KWh?



            1. Anonymous Coward
              Anonymous Coward

              Re: 15KWh? == 13kg TNT

              This is called regenerative braking. The bus doesn't use a flywheel for getting from A to B. What it does is use the braking to spin a flywheel up and then when it needs to start again it uses the energy from the flywheel to begin to move. The flywheels are typically heavy with a spin of a couple of thousand rpm.

              The flywheel in this project weighs 340kg and will have to spin somewhere between 15,000 and 30,000 rpm depending upon the flywheels size (radius).

              Should the unthinkable happen and the flywheel disintegrates it will instantly release the same energy as 13kg of TNT. This is not something I would want outside my home or any home in the vicinity.

        2. Richard_L

          Re: 15KWh?

          The expected usage of this flywheel isn't to spin it up and then put it away in the cupboard with your torches and paraffin lamp for months on end, only getting it out if you suffer a power cut. It's designed to provide overnight power for domestic solar & wind installations - to absorb excess power generated by the the system on a daily basis and then provide it as required throughout the night. Lead-acid batteries could provide that energy storage but they degrade with repeated discharge cycles, especially if the discharge is deep. A flywheel won't suffer that same discharge cycle degradation and it's 2% leakage per day isn't critical unless you live somewhere where you don't receive any sun or wind for weeks at a time.

          1. asdf

            Re: 15KWh?

            > unless you live somewhere where you don't receive any sun

            Wow must not been a Brit that wrote that. Oh well look on the bright side (haha) if the UK's weather wasn't so dreadful they might never have had so many colonies.

      2. Anonymous Coward
        Anonymous Coward

        Re: 15KWh?

        The ones we have are 300kW and 500kW Caterpilar devices.

        The flywheels can hold the load for about 30 seconds - long enough to ride out glitches and allow time for the integrated diesels to start.

        Contrary to popular belief vacuum-operated flywheels utilising magnetic floating bearings (no contact) do require annual maintenance and during that period we get exposed to the absolutely shitty power feed which led to the UPSes being installed in the first place, so a lot of critical stuff ends up being shut down.

        There's certainly an opportunity for some enterprising outfit to sell dual flywheel setups for full redundancy.

        The units we have cost about £500k apiece - and paid for themselves in less than 3 months, thanks to

        speeding up spacecraft instrument qualification exercises by a factor of 20 (they didn't have to constantly start over). Allow space for a 40 foot shipping container - and they're very quiet while the diesels are running but startup can irritate the neighbours, so placement is important.

    3. Great Bu

      Re: 15KWh?

      What are the efficiency losses for a battery system, though (I have no idea) ?

      Would the flywheel provide better performance in terms of the conversion loss for the power going into / out of storage ?

    4. annodomini2

      Re: 15KWh?

      This is intended for grid storage, so mass is less of a concern.

      To say they will have zero maintenance is naive, they have moving parts, they will need maintenance.

      At least inspection.

    5. Naughtyhorse

      Re: 15KWh? - disintegrate following an impact.

      Its a huge issue.

      in the dim distant past (about '80) i recall being talked at in college about JET, which used a big fuck off flywheel to store energy - all the numbers have long since eveporated (i just recall them being mind boggling), but i do remember that the building was sited so that in the event the flywheel got away, it was far enough away (miles and miles) from any population centres, as a flywheel going through bristol would have killed thousands.

      and further why MVA for PV and wind? a couple of kva would do it for britain :-) the sun dont shine and the wind..... well it's never the right _kind_ of wind.....

    6. talk_is_cheap

      Re: 15KWh?

      The problem is that basic lead acid batteries have a very poor duty cycle as they do not like to be discharged. The result is that you have to build a setup where you do not discharge the batteries to much before you charge them up again. For a basic car battery its best for the discharge to be no more that a few percentage points. For batteries that do support depth discharging its still best to only discharge by about 50% if you want to get the most life out of them.

      So it you want 15KWh of battery capacity you need to install 30KWh+ of batteries.

      A lot of background can be found at

  3. Cliff

    In which axis?

    Something in my gut says flexible won't scale easily - the dynamic system may well stabilise itself in the plane of rotation, I can't help but think uneven perimeter mass distribution could go critical then catastrophic pretty quickly. Maybe it is having heard my washing machine spin cycle with a pair of jeans, but I suppose I'm thinking being flexible means it's more likely to be off-axis slightly, and bad things happen.

    Happy to be proved wrong, of course, but I fear scaling will just amplify the problem exponentially!

    1. Anonymous Coward
      Anonymous Coward

      Re: In which axis?

      The theory still holds, though - even then it will have changed shape. Permanently..

    2. Mips

      Re: In which axis?

      Containment is an issue but if you have containment for a vacuum it will only need small improvements to make it suitable to contain disintegration. I would be more concerned about mounting the device in a vehicle. It would have to be flexible to prevent reaction with the flywheel but then coupling to the power supply is near impossible.

  4. Don Jefe

    Weebles Wobble But Energy Has to Go Somewhere

    Interesting. It is a nice idea and I'm very interested to see how they deal with vibration, flex and the inevitable harmonics in the full size model. Just watching the cute little desktop model made my brain dizzy thinking about the forces generated on the frame and bearings. I don't see why the flywheel itself wouldn't be reasonably sound in use but I'm not sure about the affordability of the bearings that can handle dynamic/unpredictable loads they will face. The casing and the foundation/mounting assembly will be interesting as well. Wonky spinning weight will certainly make for some wild noises: Like an inch worm with palsy would be my first guess...

    I'm going to send a few bucks their way & see how they do. It's nice to see people actually trying something instead of just ditching the idea because of naysayers & potential problems.

    1. Don Jefe

      Re: Weebles Wobble But Energy Has to Go Somewhere

      Boo. I didn't realize they already reached their goal.

    2. David Kelly 2

      Re: Weebles Wobble But Energy Has to Go Somewhere

      I agree, the energy has to go somewhere. If the flywheel flexes the energy to flex the flywheel becomes heat.

      Suspend the flywheel on magnetic bearings? Permanent magnets? Else more energy lost.

      Spin in a vacuum? More energy lost there creating and maintaining the vacuum.

      What are you going to do in an earthquake? Vibrations in the floor used to be enough to disturb early hard drives.

      1. John Gamble

        Re: Weebles Wobble But Energy Has to Go Somewhere

        Some of those problems were solved in the seventies -- a flywheel doesn't have to have the same stability as a hard drive, although you're right that there will be energy loss.

        Indeed, even the "flexible" aspect was done in the seventies, although the designs I saw had the fibers spinning radially out from the axis, rather than wrapped around the circumference. Bearings, vacuum containers, yes, this is old technology probably re-written with modern materials.

        So probably most of your questions have been dealt with. The main questions are whether, even after all that, will the energy density still be good enough to make this worthwhile.

  5. Uwe Dippel
    Thumb Down

    It does not work!

    (I'm not talking about the flywheel here, but El Reg's streaming method. I have reloaded a bunch of times, and stuff, but nothing comes from it; only the central icon shows a rotating arrow ... ... sitting on Chrome on Linux.)

    1. Anonymous Coward
      Anonymous Coward

      Re: It does not work!

      Still, the twirly thing is much nicer than the old error three thousand and something that used to come up for all Reg videos.

      Chrome / windows 7.

      1. Da Weezil

        Re: It does not work!

        Opera / iOS same... disappointing that a tech site gets details like that wrong.

    2. The BigYin

      Re: It does not work!

      "This video does not exist" according to YouTube.

      I'm guessing that this is what they wanted to show or possibly this.

    3. Dave 126 Silver badge

      Re: It does not work!

      You really aren't missing much in this video. It is 1:17 long, and spends that time telling you that a motor is also a generator, and that it takes energy to make something spin. That it is it. It is wholly generic, except for the last two seconds when the voice-over tells us "we have developed a new way of making fly wheels, then it fades to black.

    4. Dave Lawton

      Re: It does not work!

      Works for me, Firefox 3.6.24 64bit on SUSE 11.3

  6. PhilipN Silver badge

    Perennial problem

    Somebody did this with a motor car-size "motor" a few years ago and got to the stage of having a working prototype but further development collapsed through lack of funds.

    The prime mover behind the technology whinged, naturally, that the vested interests did not want to get involved.

    Not being an engineer though I bounced this idea of an engineer whose immediate question was "What happens when you want to go up a hill?"

    1. Anonymous Coward
      Anonymous Coward

      Re: Perennial problem

      "What happens when you want to go up a hill?"

      Personally, I just find a suitable hill to go up on and satisfy my hill ascension urges. YMMV. HTH.

    2. Pookietoo

      Re: "What happens when you want to go up a hill?"

      It's easier to build the house in situ than it is to build it first and then locate it.

  7. Anonymous Coward
    Thumb Down

    Odd for a kickstarter

    This is of interest to me as we are off grid. However, given the choice of a passive chemical battery with no moving parts and something that has to run in a vacuum to close tolerances etc.,, I know which option I'll take. Now if they want to work on getting the nickel-iron battery into shape, that seems interesting. But as there is little patent potential (haha!) in it, as it was invented yonks ago, it's unlikely to be developed through the standard western greed model. See

    My requirements as one off grid are not necessarily the ability to store power for very long periods of time, just enough time when power from my few solar panels and my small turbine wane. Five days is acceptable. Given what I have learnt about the joys of running the mechanical wind turbine over the different joys of managing the passive lead acid battery, I know I would not choose a dynamic option such as a flywheel. By the way, my battery bank is a smidge over 15kwHrs.

    I would much rather have a NiFe battery that can take un-ideal charge states when power comes in, and most of all, I would rather the battery bank did not deteriorate the way lead acid ones do, leading to replacement after 5-7 years even with careful management. I always laugh like a drain when battery how-to's talk about charging a battery using so-many amps at so-many volts when in the real off-grid world you're simply grateful for ANY amps at ANY voltage that flow in.


    1. Tom 7 Silver badge

      Re: Odd for a kickstarter

      Ah you named your turbine - how sweet!

      1. Anonymous Coward

        Re: Odd for a kickstarter

        "Ah you named your turbine - how sweet!"

        It's not what I called it yesterday, up the tower in a breeze! But it does make me wonder what I meant...

    2. Tom 38 Silver badge

      Re: Odd for a kickstarter

      You're confused, a kickstarter project is not intended to actually work or deliver anything useful, just keep some post grad dicking around with their pet hobby, subsidised by schmucks who think they are changing the world by pledging money from their tablets.

    3. Suboptimal Planet

      Re: Odd for a kickstarter

      "unlikely to be developed through the standard western greed model"

      Fear not. I'm sure the noble Cubans and North Koreans will get around to it Real Soon Now.

      1. Anonymous Coward
        Thumb Down

        Re: Odd for a kickstarter

        "Fear not. I'm sure the noble Cubans and North Koreans will get around to it Real Soon Now.

        House Rules "

        Ah - symptomatic binary idiocy. Move along, nothing to see here.

  8. TrevTheRev

    Scam Bovine Excrement.

    Self balancing fly wheels have been in use since the late 1800s.

    look at the mechanism on the end of any large grinding wheel,(small beads in a track).

    The orientation of the flywheel is absolutely critical unless in a horizontal East West fixed installation, the Coriolis and Gyroscope effect of large flywheels would damage or destroy the bearings on any type ( magnetic, air or ball-race) .

    Look up Coriolis ( ) and ( )

    The losses even in a vacuum with magnetic bearings would unlikely be as low as 2 percent as quoted. the sums do not add up !

    This concept is just another perpetual motion machine (


  9. TeeCee Gold badge

    You want to know if it'll work?

    Ask Williams F1.

    Their KERS (Kinetic Energy Recovery System - for those who do not follow F1) solution is a flywheel design and they've spent a lot of time, effort and cash in getting it to work properly. They probably know more about storing energy in high speed flywheels than anyone else around.

    IIRC they had to resort to wrapping the things in bonded carbon whiskers as reinforcement to stop them disintegrating[1] and that's on a fairly small object. With that from the real world, I'd be a tad sceptical about a larger object made of anything less puissantly rigid.

    [1] Which leads to the other problem. Making a casing strong enough to contain the mess when it does come apart at eye-watering revolutions. Apparently the energy release involved when that happens makes most explosives look rather unimpressive, even on their little device.

    1. Anonymous Coward
      Thumb Up

      Re: You want to know if it'll work?

      You mean it's more impressive than a Trent 900 in a blade-off event? :-)

      Ohhhhhhh, I want to see THAT! :-D

      1. Anonymous Coward
        Anonymous Coward

        Re: You want to know if it'll work?

        "more impressive than a Trent 900 in a blade-off event?"


        Simon says "no need to tell the workforce anything about it, because it didn't happen". Even though one such incident (Trents have been several in the last few years) made it into the columns of something called the Sun, as well as the usual aviation industry papers.

        1. Anonymous Coward
          Anonymous Coward

          Re: You want to know if it'll work?

          I'm not even talking about 'that event in Singapore'. Even just a test blade-off event is impressive to watch. RR has put theirs online... :-)

    2. John Robson Silver badge

      Re: You want to know if it'll work?

      Although F1 cars have another couple of pressures (total mass, and total size) which tend to encourage very small flywheels (counter rotating to deal with gyroscopic forces) at very high speeds.

      IIRC The Joint European Torus used to use a fairly hefty flywheel to power one of their diagnostic lasers...

      1. Oliver Smith 1

        Re: You want to know if it'll work?

        It was the various magnetic coils that needed the flywheels at JET. I seem to recall the pulse length being limited by the voltage ramp for the induction of the plasma current (& hence poloidal field). But it was 20 years ago that I was there.

        The largest diagnostic lasers weren't anywhere near that powerful. The Thomson scattering lasers were only a few Joules per pulse (@4Hz) and so could run from 3 phase mains. I doubt the interferometers needed to be that powerful.

    3. Mike Richards Silver badge

      Re: You want to know if it'll work?

      Didn't British Rail used to have some electric locomotives that used flywheels to carry them over gaps in the conductor? Or am I imagining something much cooler?

      1. Anonymous Coward
        Anonymous Coward

        Re: You want to know if it'll work?@Mike Richards

        "Didn't British Rail used to have some electric locomotives that used flywheels"

        Yes, British Rail's class 71, running on the third rail 750V dc system of the former Southern Railway had a flywheel booster, and that was a development from the Southern Railway's CC1 that introduced the system back in 1941.

        1. Juan Inamillion

          Re: You want to know if it'll work?@Mike Richards

          Trainspotters on El Reg!


          (Actually I'm always envious of people who can keep all that information in their heads).

      2. Anonymous Coward
        Anonymous Coward

        Re: You want to know if it'll work?

        " British Rail ... electric locomotives that used flywheels to carry them over gaps in the conductor?"

        More recently, see also: Parry People Mover, tramtrain cars that use flywheel power between stops and recharge at the stop (or have an onboard engine if stops are too far apart).

    4. Tom 38 Silver badge

      Re: You want to know if it'll work?

      Ask Williams F1.

      Their KERS (Kinetic Energy Recovery System - for those who do not follow F1) solution is a flywheel design and they've spent a lot of time, effort and cash in getting it to work properly.

      Ask Williams what - why they don't use the flywheel design in F1? Ted Kravitz went through in in-depth detail the exact operation of a Williams F1 KERS system just this Sunday, it has no flywheel, just a mass of Li-ion batteries.

      IIRC they spun out the flywheel tech to use in roadcars, they never used it in F1.

      1. Anonymous Coward
        Anonymous Coward

        Re: You want to know if it'll work?

        I'm not sure what the situation was with the Williams KERS, but it wouldn't surprise me if the FIA scented the disgusting reek of innovation and put the kibosh on it.

        I do know that it quickly got turned into a spec system that all the teams have to use the same way and that has the same performance.

        You know, the better to showcase F1's high tech heritage.


  10. kryptonaut

    Gyroscopes in cars

    Having played with toy gyroscopes as a kid, I have a mental image of the driver putting his foot down and the car just rearing up on its back wheels and slowly precessing round and round in ever wider circles, until it comes to a halt lying on its side.

    1. Dave 126 Silver badge

      Re: Gyroscopes in cars

      > I have a mental image of the driver putting his foot down and the car just rearing up on its back wheels

      Hehe.... that would be the equivalent of having your internal combustion engine attempt to turn all your petrol into kinetic energy in one go... (not good)

  11. G R Goslin


    I'd tend to doubt any organisation that begins it's spiel with:-

    "The cost of clean & distributed electricity generation like wind and solar has fallen dramatically over the past few years making them the cheapest sources of electricity in the world."

    Yhey're obviously not talking about the real world, so perhaps their flywheel is in the same world as cheap wind and solar power.

  12. John H Woods Silver badge


    14kWh is 50MJ - is a couple of pounds / dollars worth of energy: a few micrograms of uranium or a couple of litres of diesel. But this is a third of a tonne! Why are we, in the 21st century, so short of ideas for sensible energy storage that we are considering massive flywheels?

    1. Chris Miller

      Re: Context

      It's also equivalent to about 12kg of TNT. I'd be interested in a failure mode analysis. If one of these is near people and suffers a catastrophic failure, it will need substantial containment to prevent injury.

      Battery failures can lead to them dumping all their energy into the environment over a period of a few seconds or minutes - causing a fire risk and potentially major problems if they're on an aircraft, say - but one of these could do the same thing in a few ms.

      1. Dave 126 Silver badge

        Re: Context

        For grid storage, containment isn't that much of an issue- you just choose a remote site and place the whole thing in a big hole, and maybe grow a copse of trees around it.

  13. Steve Williams

    Nice big flywheels

    The computer company I worked for used to build drum storage, both small and large.

    During the 1960's the was a (no-doubt apocryphal) story that a small drum was crated up for shipment without the magnetic brake being set. It was only discovered when the fork-lift guy carrying the crate tried to make his first turn in the opposite direction to rotation.

    Better documented were the problems installing the larger drums on US Navy destroyers. These were pretty large drums produced by taking standard iron sewer piping and machining it quite precisely. Once spinning they had a definite effect on the vessels' turning circles.

    The factory was always a great source for interesting stories.

  14. Nuke
    Thumb Down

    Part old hat, part snake oil

    I thought the interesting bit would be the "flexible" aspect, but their website says little about that, and is mostly a school science presentation on flywheels and motor-generators, all well established stuff.

    It is ambiguous whether they are talking about flexible flywheel material or flexible bearings. Their desktop demo is about flexible bearings, but that principle has been used in spin driers for years, and in large steam turbines (at power stations) - you need to get above a critical speed. There is no reason flexible material for the wheel itself should be better than rigid; expect worse because any eccentricity would distort further in the same direction leading to even greater imbalance.

    There have been dynamically self-balancing gadgets around for years though. Perhaps this guy's secret lies in that area, but he reveals nothing about it in his presentations (pending a patent ?) but instead we get the usual soundbites about renewable energy and toxicity. He is a salesman, and the cost comparison between an aircraft engine and a piece of rope is fatuous.

    The basic problem with any flywheel is the small amount of energy for its cost and size (even his will cost more than the piece of rope), making them suitable mainly for transients such as allowing a contolled shutdown of equipment following a mains power failure, or recovering vehicle braking energy. The idea of covering wind power during calm periods is moonshine.

  15. Bruce Hoult

    seems like the wrong niche

    Flywheels are really great at absorbing or providing huge amounts of power over short timescales: a few seconds to maybe a few minutes. They're also great for a very large number of charge/discharge cycles. I don't think there's any successful example of using them to store energy for days.

    A Trojan IND17-6V battery weights 188 kg, stores 7.21 kWh of energy (if you take 4 days to extract it, about 5.5 kWh if you extract it in one day). It is designed for 1500 cycles at 80% discharge depth or 5000 cycles at 20% discharge depth. It costs about $1250.

    So two of these batteries will hold as much energy, weigh 380 kg (840 lb), cost $2500, and last 4 - 12 years depending on how far you discharge them each time on average.

  16. John Smith 19 Gold badge

    A few notes

    Gyroscopes don't have quite the energy density of batteries.

    OTOH they have no degradation modes. A flywheel energy storage system can store as much energy in 10 years as it can the day it was installed.

    Personally I always thought for low cost the train wheels on the TGV would be a good candidate.

    Mass produced, designed for high speed and with a significant mass on the rims (where you want them).

    I also not that a Halback array can double the force on the flywheel from passive magnets (the T/W of magnets is pretty good at about 50:1).

    The jokers are mass, containment and motor/generator electronics.

    AFAIk this proposal side steps the heavy containment and lowers the precision of the drives needed to keep the flywheel in position and properly orientated.

    As for gyroscopic effects on vehicles the obvious solution is a contra-rotating pair. However there are issues with bumps in the road and what would happen if the 'wheel hits the casing at full speed?

    1. JimC

      Re: A few notes

      *No* degradation? That's pretty impressive life for all the bearings, associated motors generators etc...

      There are all sorts of engineering challenges about this concept, and of course such things are soluble, but are they soluble for less cost of ownership than just regularly replacing batteries?

    2. MacroRodent Silver badge

      Re: A few notes

      "As for gyroscopic effects on vehicles the obvious solution is a contra-rotating pair. "

      It solves the problem when considering the pair as a whole, but wouldn't this put a HUGE stress on the axle connecting the pair?

  17. Ed 13


    but I'm still not clear what's novel. Why is comparing a Trent900 (10,000rpm and >70,000lb thrust) with a rope (0hp) useful?

    Other flywheels I know of:

    The JET project has two 9m dia. 775 tonne energy storage flywheels:

    On a rather smaller scale, firms like Parry People Movers have been using them to even out load in a mass transit situation.

    1. Anonymous Coward
      Anonymous Coward

      Re: Interesting

      It was the BLADE-OFF event of a Trent 900 that I was referring to. Ever seen one? It's impressive when it goes BOOM.

      So seeing a Williams F1 KERS flywheel go BOOM would be interesting too :-)

  18. Fred M

    Batteries OR flywheel

    All this talk of whether batteries are better. Just use a load of batteries for the mass of the flywheel and you've doubled your storage. Hybrid storage FTW.

    What could possibly go wrong? I'm off to patent it now...

  19. MJI Silver badge

    Beaten to it

    The Parry People Mover is a good example

  20. Schultz Silver badge

    scale it up

    Surely the energy transmission and efforts to keep good vacuum should scale well with size. I'd like to see GW energy storage facilities with massive flywheels.

    Feel the hum in the ground? Yea, that's last night's electricity in the Brandenburg storage facility.

    1. Anonymous Coward
      Anonymous Coward

      Re: scale it up

      "Surely the energy transmission and efforts to keep good vacuum should scale well with size"

      I doubt it. Keeping vacuum on a very large vessel would probably require some extraction for the inevitable leakage, and then you start eating into the stored energy. Maintaining a good degree of vacuum isn't a very energy efficient process. Personally I'd have thought that larger masses and slower rotation were a better bet than fancy high speeds and vacuum, although the energy density would be quite poor.

      Either way, I'll be surprised if flywheels scale well for grid storage. In terms of scaling, the Fraunhofer idea of using renewables to generate synthetic methane, and storing that in the gas network seems far more practical, given that chemical energy tends to have good energy density, but the net efficiency is still fairly poor.

      1. David Pollard

        ... renewables to generate synthetic methane

        Pyrolysis of waste to syngas and biochar would provide simple and effective energy storage. However, with the rush to green energy most sources of renewable biofuel, such as municipal waste and wood chippings, have been consigned to combined energy/incineration plants for the next two or three decades.

        1. Anonymous Coward
          Anonymous Coward

          Re: ... renewables to generate synthetic methane

          "most sources of renewable biofuel, such as municipal waste and wood chippings, have been consigned to combined energy/incineration plants for the next two or three decades."

          Why store syngas when you could simply schedule the burn of the waste? Obviously depends on the economics of the different elements, but I can't see why you'd want the complexity of gas cleaning and compression/decomp and the inevitable efficiency hit compared to simply over-sizing the CHP plant and burning when the demand is there for heat and power.

          Generally speaking you'd expect heat and power demands to be well correlated, and the probably enhanced speed of response from stored syngas over scheduled (or requested) burn isn't going to be enough to make a difference across the whole electricity system.

  21. holomntn

    The invention is fairly straightforward

    Since they published their patent application (US 20110175371 A1, among others) it is quite possible to see what they claim to be an invention. I didn't bother reading past Claim 1, and not being a flywheel expert I can't say if this is novel.

    At the top and bottom of the axle place flexible mounts, or alternately a flexible axle itself. The gyroscopic force of the flywheel will keep it level in the event of a disturbance. Not sure what value this has, especially since it only protects in 2 of the 3 dimensions of disturbance. A disturbance exactly along the axle will be absorbed completely by the bearings, but a disturbance near the axle direction would result is some large swings.

    This appears to be the actual flexibility they are talking about. You can see this in the desktop model with the swing mount at the top of the axle, and the almost invisible in the video ball socket mount near the flywheel.

    The model appears to be built of solid metal so I suspect there is minimal flexibility to the flywheel itself.

  22. Chris Long

    A related idea...

    Has this ever been considered / tried? Mount a huge gyroscope on an equatorial bearing, and it will stay still in space as the Earth rotates. How much torque (and hence power) could you extract from the system?

    1. Chris Long

      Re: A related idea...

      Note to self: Google first and ask questions later....

      It has already been patented and therefore, one must assume, isn't practical for some reason, or we'd all have free energy to power our hover boards and jet packs.

    2. Alan Firminger

      Yes, it has been tried

      But we call it tidal energy.

  23. A 15

    Regarding going up a hill

    A possible solution, in the case of a vehicle (though this wasn't proposed by the inventor), rotating to go up a hill, is to mount the fly wheel on a gimbal.

  24. Winkypop Silver badge

    Red flag alert

    Just a lot of spin!

  25. David Pollard

    Sirius Disclosure Project

    Steven Greer's latest scam is a movie to be released on the 22nd April, presently promoted on the internet by a small army of acolytes. Initial funding was raised on Kickstarter. It promises to explain how knowledge given to us by extra-terrestrials has been suppressed by government and big business. However, with disclosure the era of free energy which these alien technologies provides is about to begin.

    Greer has been promoting 'free energy' technologies for a decade or more; apparently making a good living from it. His movie might well stimulate a small spate of similar chancers seeking to hoodwink the unwary.

  26. Alan Firminger

    Good old Wikepedia

    This is relevant for starters : Gyrobus

    And this is a primer on magnetic bearings : magnetic bearings

    What is new ?

  27. Anonymous Coward
    Anonymous Coward

    1980 technology

    Jt vance, bt murphy. 1980 flywheel tecnology.

    Old paper basically details all the 'achievements' of the velker.

    Being taken for a kickstart ride?

  28. Ian Johnston Silver badge

    Looks like bullshit me

    Their kickstarter page is pure waffle and they miss the central problem with flywheels: stopping them falling to bits when they are going round fast.

  29. Alan Denman

    floor me but is it flawed

    Surely, anything but short term energy from any flywheel has to rely on perpetual motion !

  30. NIck Hunn

    What about the other losses?

    I worked on rotating anode X-ray generators many years ago, which were very similar, in that they had a large mass of metal spinning at high speed in a vacuum. The biggest problem was maintaining the vacuum across a bearing that's rotating at high speed, whilst supporting a large mass. This won't need as high a vacuum as an X-ray generator, but even with the progress in ferrofluidic seals you'll still need pumps running to maintain the vacuum, contributing to the losses.

    The other think he'll need to think about is the housing. When the bearing fails on a flywheel this size, the flywheel does a scary amount of damage, like ripping through several inches of steel. So you'll end up with something that probably weighs in excess of a ton. Which means you might be better off sticking with batteries.

  31. Chairo

    Fibreglass? Meh!

    For storing energy you want to have the highest mass possible in the smallest form factor.

    I would recommend neutronium, as it is the densest material available.

    It should be easy to mine from the brains of public officers, fanbois/-droids/winmobile fanatics and, of course, user interface designers.

    Did I forget anyone?

    1. Robert Forsyth

      Re: Fibreglass? Meh!

      I would imagine they build an empty shell of fibreglass, and the locals fill it with soil dug out to make the containment pit.

      Surely, it would be better to use the mechanical rotation directly (like during the industrial revolution: a man or boy or steam-engine got the wheel up to speed).

      Changing the radius of the mass, would change the speed of rotation.

      Kinetic energy; K_r = 0.5 m v^2 or 0.5 I w^2

      Moment of inertia for a particle mass m at radius r; I = m r^2

      So it is better to increase radius of the rim and angular velocity w, except centripetal force is F_c = m r w^2

      Lets say 1 tonne rim at radius 1 metre, energy 15 kWh = 54 MJ; w = 329 rad/sec = 52 Hz = 3138 RPM; tangential velocity = 329 m/s (almost speed of sound) = 1184 km/h = 740 mph -- sonic boom anyone?

      A 12V 60Ah battery is 0.72 kWh -> 15 kWh = 21 batteries

  32. Charlie van Becelaere

    Bloody Gyroscopes

    Precessing all over the place; how do they work?

    1. ElReg!comments!Pierre

      Re: Bloody Gyroscopes

      > how do they work?


  33. Anonymous Coward
    Anonymous Coward

    A lot of the comments are making the assumption that there will be one enormous single wheel.

    Anyone care to comment on the economies of using a number of smaller ones? They would be safer, but presumably less efficient?

    I know very little on the subject.

    1. ElReg!comments!Pierre

      I would think bigger is better.

      Multiplying the wheels also multiplies the point of failure, the loss in wiring, and the overall complexity.

      If it had to be done my money would be on one single gignormous wheel spninning very slowly, let's say, horizontally underground (under the whole windfarm that would use it for example).

      But as others have said it's still going to be a very expensive and hard-to-maintain gizmo when compared to off-the-shelf batteries.

      1. Pookietoo

        Re: gignormous wheel spninning very slowly

        You want it to spin as fast as safely possible, because energy stored is proportional to the square of the speed.

        1. ElReg!comments!Pierre

          Re: gignormous wheel spninning very slowly

          You want it to spin as slow as possible because the energy loss scales exponentially with the speed (unless in a vacuum, which makes it financially impossible).

          The energy stored is proportional to the mass of the spinning thing, with a helpful bonus for an increased radius.

          Get your physics straight!

  34. Jim Birch

    Mobile flywheels

    Thinking aloud...

    A mobile flywheel would have to be in a chassis that allows full rotation relative to the vehicle, ie, so the flywheel can maintain its orientation as the vehicle changed direction. Exactly the same mounting principle as a gyroscope. Not sure how this would work with all magnetic bearings but it could be a simple mechanical harness for orientation and magnetic for the rotational bearings. The electric connections used to store or recover power would need to handle donuts.

    In the case of a flywheel in a hole in the ground in a fixed orientation to the earth there is still a deflective force caused by the earth's rotation, aka Coriolus force, that would need to be handled. A fixed flywheel at the equator would need to completely reverse it's considerable angular momentum over a 12 hour period. There could be a lot of force involved on a high energy flywheel. Of course, this wouldn't be a problem if you could site the flywheel at the either pole but you may need a few thousand km of environmentally hardened extension chord :)

    At first looks, even a "stationary" flywheel would need to be able to rotate so that it's axis will always point at a fixed point in space. This is actually applies to the vehicle flywheel too; it you left it parked for 12 hours at Entebbe airport the flywheel would try to fully invert itself.

    OTOH there may be some kind of cunning low-loss magnetic arrangement/trick to gradually deflect the flywheel at a rate that matches earth rotation component at the latitude of the site. In which case, there'd be no problem.

    1. Pookietoo

      Re: Mobile flywheels

      Why do so many people seem to be fixated with vehicular applications? This project is not about vehicles.

  35. Choofer

    Flywheels can be scary

    Personally i've never trusted a Flywheel UPS ever since I saw one go "bang' in a datacentre. It had been service 2 days earlier, so the suspicion is that the engineer did something wrong, but due to the large amount of damage (it basically destroyed itself) when it let go, nobody will every know. Oh it it's trail of destruction included cutting through some HV cables which required the complete shut-down of power to the facility.

  36. Mussie (Ed)

    Fly wheel UPS

    We had 3 IIRC Flywheel UPS's in a large data center, yo dont need long for the gennys to cut in so they did the job perfectly.

  37. Anonymous Coward
    Anonymous Coward

    My $0.02 worth

    Has anyone considered making a flywheel out of liquid metal, such as bismuth-tin-lead and encasing it in an insulated ceramic containment vessel then spinning it electromagnetically?

    The liquid phase should be stable as long as it stays hot, and no moving parts need contact the outside so a stack of these could be constructed using a single coil set for low cost.

    Ought to work in theory, you can see a miniature version of this in operation on Youtube, "spinning mercury"

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