Flywheel based electrical storage

LBergmanLBergman Posts: 42Solar Expert
Came across this today:

http://www.dailytech.com/article.aspx?newsid=12110

Could be very interesting if the marketing is true. Would probably have implications for renewable energy.

Comments

  • BB.BB. Posts: 28,034Super Moderators, Administrators admin
    Re: Flywheel based electrical storage

    Flywheel systems have been around for decades... Usually the problem are losses from the spinning wheel.

    This system seems to have an operational 2% overhead for storage. So--I guess, just running for 50 hours of standby (2 days)--and you have a 100% loss.

    Nothing listed on the web site referenced energy storage/output for longer than 30 minutes... So, I would guess it is still intended for sustaining emergency power long enough until a generator can kick-in--or it might be nice for something like a wind farm where you have variable power output--allows averaging the output power over 10-30 minutes. Be easier for a utility to support as a generator source.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • newenergynewenergy Posts: 291Solar Expert ✭✭✭✭✭✭
    Re: Flywheel based electrical storage

    BB,

    How do you figure the 2% standby-loss means it loses 2% of power per hour?

    (that still wouldn't really mean it was 100% loss in 50 hours)
  • BB.BB. Posts: 28,034Super Moderators, Administrators admin
    Re: Flywheel based electrical storage

    As I read it from a PDF presentation (and other documents):
    Standby loss
    <2% of rated power
    Others just said 2%... My guess is that if you have the flywheel up to 100% speed (capacity)... You would still have to feed power at a rate of 2% of the rated power... In 50 hours, you would have "burned" the equivalent in storage...

    And even then, I may still have underestimated the losses--From the same spec:
    Output power
    20 MW max. continuous for
    15 minutes
    So--it may instead be 2% of 20MWatt which is only available for 15 minutes... so the real losses may be 2% * 60 min /15 min duty cycle = 8% losses. Or 100% cost of power to keep spinning at 100% RPM for 12.5 hours...

    I certainly may be wrong--but I did not see any other clear efficiency ratings/definitions.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Solar GuppySolar Guppy Posts: 1,959Solar Expert ✭✭✭
    Re: Flywheel based electrical storage

    BB is right, the mechanical friction losses make using flywheels limited UPS type functions. Also a concern is when these thing fail, the mechanical enegry released is very dangerous, requiring they be placed into concrete bunkers ( no bull ) otherwise it will wipe out anthing for a football field around it
  • newenergynewenergy Posts: 291Solar Expert ✭✭✭✭✭✭
    Re: Flywheel based electrical storage

    Which one was right? 12.5 hours or 50 hours? Exactly what does the 2% efficiency mean and how do you use that to calculate how long the flywheel will spin on it's own?

    I should have said that I didn't doubt the general point that flywheels aren't good for just sitting there storing energy for long periods.
  • BB.BB. Posts: 28,034Super Moderators, Administrators admin
    Re: Flywheel based electrical storage

    The reason that I "guessed" how much power running at 100% full standby is because that was the only spec. I could find.

    Because many of the frictional losses may be related to the square of the rotational velocity and others are linear--it is difficult to say how long the flywheel may effectively store power.

    If we assume that 8% standby loss is proportional to the rotational velocity--you could guess that the amount of power remaining at any point in time might be (as an exponential decay):

    100%*(0.92^t)= % energy remaining in t hours...

    92% at 1 hour
    85% at 2 hours
    66% at 5 hours
    43% at 10 hours
    19% at 20 hours
    1.5% at 50 hours

    Don't have a clue if the above is accurate or not--but it is probably as close as you will come to comparing the energy storage to a "battery" without calling Beacon up and getting more specifications.

    And, after reading the specs. more closely--I believe that the 8%/12.5 hour number is correct. This is a typical method used by marketing to bury the negatives of a system (use % power losses without clearly stating any real numbers and spec system out to 30 minutes of use--but define power output as a maximum amount over 15). Not quite deceptive--but defining strengths of a system in the best ways possible.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • newenergynewenergy Posts: 291Solar Expert ✭✭✭✭✭✭
    Re: Flywheel based electrical storage

    I guess they aren't marketing the flywheels for long term storage, so they don't need to provide info that helps you figure such things out.

    I was just curious and trying to figure it out myself. I don't see from their specs or FAQ or some brief research even what a good definition of standby-loss is. I don't see where it says any particular time unit (8% loss per hour, day, week...) so either I missed it or it's just something you knew before.
  • BB.BB. Posts: 28,034Super Moderators, Administrators admin
    Re: Flywheel based electrical storage

    I am going by 2% loss based on maximum power rating--this is a rate, so you just multiply by hours if you want kWhr losses:

    2% standby losses of rated power * 20MW (15 minute peak rating) = 0.4 MW or 400 kWatt required to keep the flywheel spinning at 100% speed? At $0.10 per kWhr--that is $4 per hour standby losses.

    Sounds really high--but this is for a 200 "unit" installation. So the cost per flywheel is 2kW per flywheel ($0.20 per per hour per flywheel) for a 100kW peak in/out per unit. Still a fair amount of heat being released (wasted energy).

    :confused:

    -Bill

    But, I should also add that we "budget" 10-20% loss, per cycle for AGM/Flooded cell lead acid battery losses. If you are cycling a lot of power to even out (like from a wind farm) over short periods--the losses from a flywheel system may end up being a lot less.
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • newenergynewenergy Posts: 291Solar Expert ✭✭✭✭✭✭
    Re: Flywheel based electrical storage

    20MW for 15 min means that the flywheel max is 5MWh. It takes a constant .4MW in order to keep it at max energy, so just assume it would lose .4MWh/h. 5MWh/(.4MWh/h) = 12.5 hours.

    Ok, sounds good to me. I'm sure the numbers are a little different because it will have less resistance at lower speeds, but good enough. Sorry for being dense.
  • LBergmanLBergman Posts: 42Solar Expert
    Re: Flywheel based electrical storage

    I'd be interested to know what kind of bearings they use. In particular, I wonder if they're fluid-type ones. Wonder if it would be possible to use some type of magnetic levitation, and have no bearings at all.
  • BB.BB. Posts: 28,034Super Moderators, Administrators admin
    Re: Flywheel based electrical storage

    They apparently use Magnetic Bearings....
    Active lift and magnetic bearing system

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • LBergmanLBergman Posts: 42Solar Expert
    Re: Flywheel based electrical storage
    BB. wrote: »
    They apparently use Magnetic Bearings....



    -Bill

    Thanks, I must of missed that. So (in theory) the only source of friction should be whatever is caused by electromagnetic fields.
  • BB.BB. Posts: 28,034Super Moderators, Administrators admin
    Re: Flywheel based electrical storage

    Also, if they use "Active Lift"--that would seem to imply to me that there are also losses with the electronics needed to supply the levitation (and perhaps shaft position). 2kW standby power per unit implies that there are significant amounts of power required to keep this thing idling.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • rickeolisrickeolis Posts: 110Solar Expert ✭✭✭✭
    Re: Flywheel based electrical storage

    This is in their write-up:
    "With the average household consuming approximately 8,900 kWh yearly, this would be enough to power a home for over 10 days"

    Wow, I could probably run a RV type generator for 10 days for a sliver of the cost of this huge flywheel bank. Even with the price of gas as it is right now.

    -Rick-
  • BB.BB. Posts: 28,034Super Moderators, Administrators admin
    Re: Flywheel based electrical storage

    A name from the past:

    Beacon Power goes bankrupt.
    Beacon Power Corp filed for bankruptcy on Sunday just a year after the energy storage company received a $43 million loan guarantee from a controversial U.S. Department of Energy program.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Solar GuppySolar Guppy Posts: 1,959Solar Expert ✭✭✭
    Re: Flywheel based electrical storage

    They never should have been given the loan to begin with Beacon has flopped on every product they have attempted
  • RCinFLARCinFLA Posts: 1,280Solar Expert ✭✭✭
    Re: Flywheel based electrical storage

    Primary application of flywheel UPS is to provide temporary power to give time for backup generator to come online.

    For critical applications like medical and computer systems backup, the choice is either a flywheel UPS or large battery rack UPS. Both have inverters to make the phase/voltage transition from grid to UPS to generator and generator to UPS back to grid without interruption of power.
  • chevensteinchevenstein Posts: 100Solar Expert ✭✭
    Re: Flywheel based electrical storage
    BB is right, the mechanical friction losses make using flywheels limited UPS type functions. Also a concern is when these thing fail, the mechanical enegry released is very dangerous, requiring they be placed into concrete bunkers ( no bull ) otherwise it will wipe out anthing for a football field around it

    Yes, that is exactly what happens:

    flywheel-failure.jpg

    Beacon used some kind of carbon fiber material in the flywheel (the black residue), which makes failures like the one above somewhat containable with their burial strategy.

    The Beacon product was targeted for frequency regulation service, where the grid operator dispatches the flywheel controllers to export or import energy in real time with other regulation capable generation assets, like smaller combined cycle turbines and pumped hydro setups. This means that the flywheel is not storing energy for more than a few seconds or minutes, most of the time. I don't believe that flywheel based regulation ever got over about 90% overall system efficiency (controller losses as well as other parasitic loads beyond the flywheel's loss itself are substantial).
  • dreesdrees Posts: 481Solar Expert ✭✭✭
    Re: Flywheel based electrical storage
    Yes, that is exactly what happens:
    Ouch, is that one of Beacon's in NY?

    Looks like they need more concrete as the lid popped off and there is visible damage outside of the containment unit.

    Seems that it wouldn't be safe to have personnel around those when spinning at high speeds even with the containment unit designed as is.

    Edit: It is, here's a link to the story when it happened back in July: http://eastwickpress.com/news/2011/07/a-mishap-at-the-beacon-power-frequency-flywheel-plant/
  • YehoshuaAgapaoYehoshuaAgapao Posts: 280Solar Expert ✭✭
    Re: Flywheel based electrical storage

    My house without the solar or swamp coolers or insulation or overkill attic ventilation was consuming around 22,000 KW-h per year. Almost half of that went straight to that air conditioner.
  • MarkPMarkP Posts: 41Registered Users ✭✭
    Re: Flywheel based electrical storage

    I have read most of the links provided about these flywheel storage units and I give up trying to decipher their "efficiency". It seems almost intentionally ambiguous. The standby losses shouldn't be linked in any way to the power output of the modules, which would necessarily be a maximum number. In other words they can put out a maximum power of 100 kw but as with batteries they can put out anything from 0 to 100 kw. It makes more sense to say they store 25 kwh when they are at maximum speed and how fast you take it out is up to you as long as it is less than 100 kw. At that point I would expect to see a curve showing how many watts are dissipated vs rotational speed. Some calculus would then give you how the power remaining vs time (as long as you were not drawing power). This would be per 25 kwh unit. The fact that no such curve is provided says more about the whole concept than anything else. Also that the only actual installation was for such short term storage says a lot and this is consistent with the advertised rate of discharge of 100 kw for 15 minutes. The manufacturer of my golf cart batteries advertised how many hours they would run, not how many minutes.
  • BB.BB. Posts: 28,034Super Moderators, Administrators admin
    Re: Flywheel based electrical storage
    MarkP wrote: »
    I have read most of the links provided about these flywheel storage units and I give up trying to decipher their "efficiency". It seems almost intentionally ambiguous.

    Yep, when I made many of those posts, it was very unclear how they calculated efficiency--But I was pretty sure I understood the model and the actual losses were pretty high.

    If your storage battery went "flat" in hours or a day--You would not be very happy.

    And that is the issue, the larger the system, the more power it "burns" to keep up to speed and ready to help stabilize the loads/generation.
    The standby losses shouldn't be linked in any way to the power output of the modules, which would necessarily be a maximum number. In other words they can put out a maximum power of 100 kw but as with batteries they can put out anything from 0 to 100 kw.

    The answer is "it depends"... If the stored energy is there to run the local power for ~5 minutes until a diesel/natural gas genset can get up to speed and take the load--Then you would run the flywheels near maximum speed (and, as I understand, there are a some flywheel based storage systems for computer centers).

    If you where trying to "smooth out" a wind farm--Then you would be looking more at running at 50% capacity so that it can be a load or a source as needed to better match loads to variable generation power.
    It makes more sense to say they store 25 kwh when they are at maximum speed and how fast you take it out is up to you as long as it is less than 100 kw. At that point I would expect to see a curve showing how many watts are dissipated vs rotational speed. Some calculus would then give you how the power remaining vs time (as long as you were not drawing power). This would be per 25 kwh unit. The fact that no such curve is provided says more about the whole concept than anything else.

    From what I can tell, this post (of mine :-)) is still about as accurate as I have seen:
    BB. wrote: »
    The reason that I "guessed" how much power running at 100% full standby is because that was the only spec. I could find.

    Because many of the frictional losses may be related to the square of the rotational velocity and others are linear--it is difficult to say how long the flywheel may effectively store power.

    If we assume that 8% standby loss is proportional to the rotational velocity--you could guess that the amount of power remaining at any point in time might be (as an exponential decay):

    100%*(0.92^t)= % energy remaining in t hours...

    92% at 1 hour
    85% at 2 hours
    66% at 5 hours
    43% at 10 hours
    19% at 20 hours
    1.5% at 50 hours

    Don't have a clue if the above is accurate or not--but it is probably as close as you will come to comparing the energy storage to a "battery" without calling Beacon up and getting more specifications.

    And, after reading the specs. more closely--I believe that the 8%/12.5 hour number is correct. This is a typical method used by marketing to bury the negatives of a system (use % power losses without clearly stating any real numbers and spec system out to 30 minutes of use--but define power output as a maximum amount over 15). Not quite deceptive--but defining strengths of a system in the best ways possible.

    -Bill
    Also that the only actual installation was for such short term storage says a lot and this is consistent with the advertised rate of discharge of 100 kw for 15 minutes. The manufacturer of my golf cart batteries advertised how many hours they would run, not how many minutes.

    So--At this point, flywheels would be for short term storage and, ideally, would have better cycle life than a big bank of lead acid batteries (or even super caps, etc.).

    Otherwise, AGM Batteries and Flywheels have similar capabilities (~15 minutes discharge/charging cycle "best case" specifications). It is really the electronics (and any electromagnetics of the flywheels) that are limiting the actual peak output (i.e., make the flywheel support a 1 minute charge/discharge cycle--15x peak wattage--Sounds great, but are the variations in, for example wind farm output, on a 1 minute time constant, a 15 minute scale, or what).

    You can go to the California Independent System Operators web site and see the variability in wind on a state wide scale (CAISO is ~85% of the electric power in the state)... It looks like 15 minutes would be about the minimum useful storage time to manage variable wind farm output.

    It would be interesting to see what the "fine grained" variability is (on a local/regional level, and down to the minute or less resolution)...

    Anyway--At this point, I don't think flywheels are going to be used for short term power/load management at this time.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • peakbaggerpeakbagger Posts: 341Solar Expert ✭✭✭
    Re: Flywheel based electrical storage

    By the way, Beacon is back from bankruptcy and selling equipment

    http://www.powermag.com/issues/features/Beacon-Power-Makes-a-Comeback_5712.html

    Looks like there target market is short term power load management.

    In reality I expect their market is whatever one has the highest incentives.
  • BB.BB. Posts: 28,034Super Moderators, Administrators admin
    Re: Flywheel based electrical storage

    Here is their current marketing presentation... Nothing on efficiency, but quite a bit of detail on short term power variations and overall cycle life:

    http://www.beaconpower.com/files/bp_intro.pdf

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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