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Power Technology

Batteries To Store Wind Energy 275

Posted by Soulskill
from the charging-at-wind-mills dept.
Roland Piquepaille writes "Scientific American reports that Xcel Energy, a Minneapolis-based utility company, has started to test a new technology to store wind energy in batteries. The company is currently trying it in a 1,100 megawatt facility of wind turbines in Southern Minnesota. The company started this effort because 'the wind doesn't always blow and, even worse, it often blows strongest when people aren't using much electricity, like late at night.' It has received a $1 million grant from Minnesota's Renewable Development Fund and the energy plant should be operational (PDF) in the first quarter of 2009. If this project is successful, the utility expects to deploy many more energy plants before 2020 to avoid more polluting energy sources."
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Batteries To Store Wind Energy

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  • by Anonymous Coward on Sunday December 28, 2008 @03:05PM (#26251001)

    I hope it's not 9 volt. Those are hard to find.

  • by Anonymous Coward on Sunday December 28, 2008 @03:07PM (#26251013)

    Why are more utilitys not using something like what beacon power is doing.

    Storing energy in flywheels. Spin it up when the wind blows. Draw it off when you need it. They last for a very long time when compared to batterys.

    Batterys are kind of high priced for a low lifetime. Require all kinds of nasty chemicals to make and need to be disposed of someday. And take HUGE banks to store what a large flywheel would store.

    Seems silly...

    • Re: (Score:2, Informative)

      by Anonymous Coward

      I believe that more isn't being done with flywheels because storing energy in flywheels costs much more than the NaS batteries.

      • by AndGodSed (968378) on Sunday December 28, 2008 @04:02PM (#26251461) Homepage Journal

        I remember that flywheels were considered for electric cars as well.

        Some of the issues I remember off hand were:

        1. Specialized materials needed to build flywheels that are small, yet heavy enough to keep spinning for a long enough time after being "charged"

        2. Getting the energy IN the flywheels in the first place - it takes more energy to get them spinning than what you draw from them.

        3. Given the high velocities - what will happen when they fly apart? Also, the gyroscopic effects they generate while spinning.

        4. The heavy mounts needed to safely position them negated any advantages through increased weight.

        I don't know if any of these apply to stationary flywheels built into power plants though...

        • by Meumeu (848638) on Sunday December 28, 2008 @04:41PM (#26251747)

          I remember that flywheels were considered for electric cars as well.

          Some of the issues I remember off hand were:

          1. Specialized materials needed to build flywheels that are small, yet heavy enough to keep spinning for a long enough time after being "charged"

          2. Getting the energy IN the flywheels in the first place - it takes more energy to get them spinning than what you draw from them.

          3. Given the high velocities - what will happen when they fly apart? Also, the gyroscopic effects they generate while spinning.

          4. The heavy mounts needed to safely position them negated any advantages through increased weight.

          I don't know if any of these apply to stationary flywheels built into power plants though...

          They don't apply for a power plant:

          1. you don't care about the size and you don't need to keep it charged for weeks
          2. you will have it with every design you can come up with, the question is how much do you lose?
          3. put a big container that can contain it if it flies apart, you don't care about gyroscopic effects
          4. not applicable to a stationary plant
          • Re: (Score:3, Interesting)

            by caitsith01 (606117)

            Other advantages of being stationary are that you can afford the space/weight to add additional infrastructure which you would never fit in a vehicle.

            For instance:

            - you could try building it in a near-vaccuum or at least low-pressure chamber to make air resistance negligible

            - the heavy and complex equipment needed for extremely low friction bearings (or even something frictionless) could be much more easily constructed on land

            For some reason I love flywheels. They're just so much more elegant than chemical

            • by mosb1000 (710161) <mosb1000@mac.com> on Sunday December 28, 2008 @09:22PM (#26253691)
              No, I ran the numbers on this a couple years back. The amount of energy you can store in a fly-wheel is limited by the (tensile) strength to weight ratio of the materials you are using. They could never be as inexpensive as chemical batteries (unless you use carbon nanotubes or something like that that doesn't exist). Also, they have moving parts, while batteries have no moving parts. To me that means batteries are a more elegant solution.
        • Re: (Score:3, Informative)

          by icegreentea (974342)
          Well, point number 2 is true of any storage solution. From what I remember, very large flywheels rank fairly high in terms of efficiency, especially compared to battery solutions. In a stationary mount, you don't have to worry about gyroscopic affects, and presumably you could build them within enclosures strong enough to contain explosions. Also, apparently the new composites being used upon 'exploding' completely disintegrate, so instead of a supersonic steel shrapnel, you get a crap load of superhot sand
        • by kent_eh (543303) on Sunday December 28, 2008 @05:06PM (#26251915)

          3. Given the high velocities - what will happen when they fly apart? Also, the gyroscopic effects they generate while spinning.

          For a stationary plant, have it spin horizontally, and build it underground.
          If it does suffer a catastrophic failure, loss of life and damage to surrounding infrastructure should be minimal

          • by FatdogHaiku (978357) on Sunday December 28, 2008 @06:49PM (#26252695)
            If it spins horizontally, won't it be fighting the rotation of the earth... always turning a corner so to speak. So we build a bunch of them, then the Global Slowing crowd forms and someone makes a movie no one is ever allowed to spin anything without permission from the Rotational Protection Agency... Leave them up on edge and let the chips fall where they may.
        • by An Onerous Coward (222037) on Sunday December 28, 2008 @05:51PM (#26252259) Homepage

          The weight of a flywheel is far less important than the weight. Energy of motion is a product of mass times velocity squared, so doubling the rate of rotation quadruples the amount of energy stored. The ideal for many applications is to find a material that is very light, but won't fly apart at high speeds. I remember reading about somebody trying something with carbon nanofibers, but that was a long while back.

          The weight doesn't matter much for energy seepage either. A good flywheel will be suspended by magnets, so regardless of the weight, the friction due to weight is effectively zero. There is still air friction and electrical losses to deal with.

          Getting energy into them isn't a huge obstacle either. I've scoured the web, and it looks like the people actually selling flywheels-as-UPS solutions are claiming 90% efficiency.

          Something may be missing in my understanding here. The article claims that the battery backup for the wind farm costs about three million dollars per MWH, whereas the flywheel backup system I'm looking at right now [vyconenergy.com] claims that it can give you about 200kWH capacity for about $50,000. That's $250k per MWH installed, and very low maintenance costs.

          Their claims could be overblown, or I could have my math wrong, or there is something I'm missing that makes the flywheels unsuitable for this application. There might also be a huge economic opportunity, but somehow I doubt it.

          • Re: (Score:3, Informative)

            That first sentence was supposed to be "The weight of a flywheel is far less important than the rotation speed."

          • I wonder if you could lessen the air friction problem with either a directed airflow around the wheel, or putting the wheel in a vaccuum...

          • Re: (Score:3, Interesting)

            by swillden (191260)

            A good flywheel will be suspended by magnets, so regardless of the weight, the friction due to weight is effectively zero. There is still air friction and electrical losses to deal with.

            Put the flywheel in a permanently-sealed vacuum chamber. Accelerate and decelerate it with magnetic fields as well. Effectively it's a large electric motor that accelerates the flywheel when you feed power into it and a generator that decelerates the flywheel when you put a load on it.

            • by networkBoy (774728) on Monday December 29, 2008 @02:48AM (#26255437) Homepage Journal

              Put the flywheel in a permanently-sealed vacuum chamber.

              no such thing. Not that it's a big deal. Commercial vac dewars and such have ports for pulling out excess atmosphere that seeps in anyway. you would use the same thing here. Wrap the outside of the chamber with LN2 pipes to cool the air inside so that is is less energetic and "falls" to the bottom of the chamber, then with the help of a turbo pump suck the chamber of all air present that is reasonable to get out.
              -nB

        • Re: (Score:3, Interesting)

          by wylf (657051)

          Actually, a few Formula 1 teams are adopting a flywheel solution to implement KERS (Kinetic Energery Recovery System) for the upcoming 2009 season.

          http://www.greencarcongress.com/2007/11/second-major-f1.html [greencarcongress.com]

          From memory, BMW and Ferrari have opted for different technology though.

          • by Dr. Spork (142693)

            This is really interesting! I'm not sure I completely get the principle, but it almost sounds like the flywheel is a glorified transmission - that the engine runs at a constant, optimal rpm to spin up the flywheel, and energy is removed from the flywheel as needed for the propulsion of the car. This means that more torque is available for straightaways than what the engine itself can provide, increasing both performance and efficiency.

            I can also imagine that the flywheel itself could be tilted with hydrau

            • by Thing 1 (178996)

              I can also imagine that the flywheel itself could be tilted with hydraulics to take advantage of the gyroscopic effect for enabling tighter turns. I doubt F1 would allow this, but it would be a pretty amazing ride! I can imagine future F1 drivers wearing a g-suit.

              So, it was a really shitty movie, but perhaps Speed Racer-style maneuvering is in our racing sports' futures?

    • by slimjim8094 (941042) <slashdot3NO@SPAMjustconnected.net> on Sunday December 28, 2008 @05:07PM (#26251927)

      I heard a story of a datacenter in California doing this for backup power. The center was powered off of the mains, and also had a large (20ft or so) flywheel kept running. If the power cut, the flywheel powered the necessary systems for the minute or so it took the generators to start up.

      Seemed ingenious to me.

      • by LWATCDR (28044)

        Actually it is pretty old school. Old mainframes had a UPS/surge suppressor that was just about as good as it gets.
        They used an electric motor hooked to the mains, the motor spun a flywheel that was spun a generator that powered the computer.
        There was also a clutch to a an IC motor. When the power failed the clutch engaged the motor and started it up.

      • Re: (Score:3, Informative)

        by LoRdTAW (99712)

        Caterpillar offers such a system: http://www.cat.com/cda/layout?m=37516&x=7 [cat.com]. Their flywheel UPS keeps the electronics up and running allowing the diesel/gas turbine generators to start. The idea is you don't need a big battery bank that holds minutes or hours of power. You just need enough power to allow the generators to kick in and transfer switch to resume power. It is much more efficient, cost effective and low maintenance than batteries.

        Another idea for high density power storage is the molten salt [wikipedia.org]

        • Re: (Score:3, Interesting)

          by bitrex (859228)
          An interesting aside: the Chernobyl accident occurred while the operators were running a test to see if, during an external power failure, the flywheel action of the steam turbines as they spun down could keep the reactor coolant pumps operating for a minute or two until backup diesel generators came online. It's academic now, but the tests showed that they couldn't.
    • by Anonymous Coward on Sunday December 28, 2008 @06:00PM (#26252325)

      Flywheels are attractive for short-term peak power delivery. They have low failure rates and easy fault detection (if the wheel is intact and spinning at the required speed, you know how much energy is available).

      For long term loads (hours) flywheels aren't competitive with lead-acid batteries, let alone more exotic types such as the NaS battery the article describes. For example, the Active Power CSDC-500 [activepower.com] flywheel storage system supplies 50kW for 138 seconds = 1.92kWhr. The cabinet is 78" x 54" x 34" and it weighs just over 3 tons. Four long-term loads, a system with two 12V 100Ahr VRLA batteries [cdpowercom.com] would be 14" x 14" x 10" and weigh 140 lb.

      A flywheel based system has nowhere near the energy density of a battery storage system. Peak power density is the flywheel's forte.

    • I've heard of Intel doing this for "critical power" systems that take forever to come back up after a power outage(and when your making hundreds of CPU's a minute, those costs in lost production get really high). The problem with the flywheel systems is you have a huge loss in the motor to turn the wheel, and the generator to power the equipment. Basically, you pump something like 1.5kW, and end up with 1kW on the other side. The power loss makes them incredibly expensive for all but the most important s

    • Re: (Score:3, Funny)

      by davidphogan74 (623610)

      Why are more utilitys not using something like what beacon power is doing.

      I read that as "bacon power" and I just imagined the greasiest power plant ever.

  • This is an old dream, but is has almost always been defeated by economy. And according to the article, it still is, though it is getting better:

    [i]But it is expensive, costing roughly $3 million per megawatt plus millions for start-up and testing. "Right now, they're a little too expensive," Novachek says.[/i]

    Looking at the numbers, it seems like a small-scale test setup. 7 MWh is not much in an 1100 MW wind turbine facility.

     

    • by bugi (8479)

      Put back in the externalized costs, so's to compare real costs. Then we'll talk.

      • by hedwards (940851)

        Indeed, that's one of the things which has harmed the US' production capabilities the most. We don't include those extra costs. We don't consider the cost of coal pollution when calculating the cost and it's the real reason why we need some sort of tax that companies pay when they excessively pollute. Realistically there's going to always be some consequences, but when somebody else has to pay for the damage there's no incentive to pick up the tab oneself.

        • by mweather (1089505)
          Just imagine what we'd pay for energy is coal/oil companies had to actually pay for mineral rights instead of paying pennies on the dollar to the government.
    • Re: (Score:2, Informative)

      by orlanz (882574)

      Exactly, battery tech isn't economical yet. And it isn't improving anytime soon as batteries are pretty much at the end of their innovation (barring any major breakthrough). Similar to "how do you make a better wheel?" Batteries are the only solution in small setups, but I don't think they scale very well to really large systems.

      Our current solution is to send it to the grid and pump water back up in hydroelectric plants. Wouldn't dedicated HVDC lines from solar/wind plants to hydro be a more economical

  • i would have to say that it always blows in the day, however in the evenings and during the night there is seldom any wind.
    • by AndGodSed (968378)

      Depends on where you are.

      If you stand on the shoreline here in South Africa you will find shore bound winds in the morning as the coast heats up, and sea bound winds in the evening as the shore cools down.

      And this is long before/after the sun has risen/set.

      In Capetown in the windy season the SouthEaster blows basically 24/7.

    • by osu-neko (2604) on Sunday December 28, 2008 @04:53PM (#26251815)
      As a sailor, I'm sure your maritime experience is vast. But... do you happen to know where Minnesota is? You might want to check a map... XD
  • by wjh31 (1372867) on Sunday December 28, 2008 @03:19PM (#26251105) Homepage
    i believe some dams release water through the turbines during peak times, then pump it back up off peak at night with excess cheap electricity ready for the next day, is that not a reasonable form of energy storage? i imagine a similar level of energy storage in anything recognisable as a battery would be insanely expensive and/or involve alot of toxic chemicals
    • by Thundersnatch (671481) on Sunday December 28, 2008 @03:33PM (#26251223) Journal

      The best places for wind turbines (open plains) are usually far away from the best places for dams (canyons). The increased cost of building transmission lines and increased losses on those lines makes your solution impractical for most locations. A few exceptions may exist, but most "wind alley" locations like TX, OK, and IA don't have the elevation changes needed for hydropower.

      • by mollymoo (202721) on Sunday December 28, 2008 @04:11PM (#26251525) Journal

        Oklahoma already has two hydo plants and one pumped storage plant. You don't need huge elevation changes, a few hundred feet will do.

        • Re: (Score:3, Insightful)

          by Thundersnatch (671481)

          "A few hundred feet" is almost impossible to come by in the most ideal wind-power locations such as the I-states (Indiana, Iowa, Illinois) and west Texas. You can see the curvature of the earth in central Indiana over the corn. But as I said, there are some exceptions.

          There is, I believe, one small hydro plant in Illinois, for example. One. But there are something like 40,000+ square miles of good windpower territory in Illinois. Unless you use the existing grid somehow (don't know if you can), building tra

      • by copponex (13876)

        In the wind alley, they do a lot of farming, right? Why not create two level reservoirs, one a hundred and fifty feet higher than the other, and then when there is excess production, you pump the lower reservoir into the higher one. Even better, find some underground features that would make it easy to create underground reservoirs with different elevations. And if you hit a hot spot of granite, even better - redirect the steam so it spins some turbines.

        Drought presents problems to open air reservoirs. It m

      • by thisissilly (676875) on Sunday December 28, 2008 @07:33PM (#26253007)
        So the obvious thing to do is to run half the windmills in reverse at off-peak times, and push the wind back so it can be used later!
    • by rrohbeck (944847)

      That's correct, but only if you have an existing dam. Building one just for storage is only viable if you have a huge height difference, i.e. a mountain.

    • by necro81 (917438)
      Believe me when I say that the Dakotas and western Minnesota are no place to build a dam.
  • by crovira (10242) on Sunday December 28, 2008 @03:27PM (#26251179) Homepage

    I'd pump water UP to store the energy and let it flow DOWN to release the energy.

    Granted it might not be as efficient as battery storage but it would be cheap, deploy-able right now, and it can be made as large as needed, plus it can be used to extinguish fires "downhill' and slake thirst.

    It doesn't even have to be in the same place as the wind farm. Just in front of it, like in the mountains like the ones that cause the chinooks winds in Alberta.

    I can see setting up a mountain top reservoir, filling it with water pumped by excess energy and emptying it when needed.

    • by hypersql (954649) on Sunday December 28, 2008 @03:36PM (#26251243)
      They do that. It's called Pumped-storage hydroelectricity [wikipedia.org].
    • Re: (Score:3, Interesting)

      by barfy (256323)

      They do this off the Grand Coulee Dam. But they are hardly ever used, as they are only really needed when there is need for flood control, AND lack of Power Need.

      There already exist these giant "batteries" and couldn't the power be utilized for things like this, rather than something new?

      There seem to be a ton of places where one could use excess energy at night, that you wouldn't need a new "Battery" source.

      • by timeOday (582209) on Sunday December 28, 2008 @04:08PM (#26251505)

        There seem to be a ton of places where one could use excess energy at night, that you wouldn't need a new "Battery" source.

        Selling a few million plug-in hybrids should help quite a bit.

        It would be even better if those cars were on the Internet so they could talk to the power company. For instance if I tell my car to be charged by 8am the next day, it could negotiate with the power company to draw power whenever it is cheapest.

      • Re: (Score:3, Interesting)

        by hedwards (940851)

        I know there's been some consideration to storing energy in freezers. It's not technically storing, it's more like shifting power draw from peak to off peak times allowing for the capacity to be more efficiently used.

        Basically with refrigerated warehouses being set a few degrees colder off peak and being allowed to warm subtly during peak. It's always below the necessary temperature, but the cooling system is off during large chunks of the peak consumption hours.

    • by slim (1652)

      I'd pump water UP to store the energy and let it flow DOWN to release the energy.

      This is already mainstream technology. Traditionally it was used as a buffer between a constant power source (e.g. coal fired power station) and a variable demand (pesky consumers).

      But it's not a big step to use the same technology to buffer between a variable source such as wind, and a variable demand.

      OTOH I'm sure I've read statements by proponents of wind power stating that on a grid as large as the UK's (and the UK's not that big), drops in wind in one part of the country would almost always be compensa

    • Re: (Score:3, Informative)

      by ionix5891 (1228718)

      they do that here in Ireland [wikipedia.org]

      ive been at the facility few years back, quite impressive engineering stuff (for a small country)

    • by Nerdfest (867930)
      Wouldn't wind storage be best done with balloons?
  • MIT's Daniel Nocera is working on fuel cells and solar power [blogspot.com] as the energy storage, if the economics can be worked out.
  • Batteries need to be replaced, and are composed of a number of undesirable chemicals. Seems like ultra-capacitors might be of use here. Several orders of magnitude more recharge cycles and generally safer. Portability isn't an issue, so they could be as big and heavy as needed.

    • by rrohbeck (944847)

      LOL. 1 MWh = 3.6 GJ. An ultracapacitor stores a few J max so you'll need about a billion of them.

      • According to this article (which may or may not be accurate- I don't know enough to say):

        http://www.batteryuniversity.com/partone-8.htm

        The gravimetric energy density of super-capacitors is approximately 1/5 to 1/10 that of traditional batteries. That is to say, on the order of 1 to 10 Wh/kg. The original article says the array in Minnesota is designed to store 7 MWh. So, to store that much energy in a super-capacitor, assuming the energy density figures from that link are correct, the device would need t

    • by causality (777677)

      Batteries need to be replaced, and are composed of a number of undesirable chemicals. Seems like ultra-capacitors might be of use here. Several orders of magnitude more recharge cycles and generally safer. Portability isn't an issue, so they could be as big and heavy as needed.

      There is one question I have about supercapacitors and you'd think it would be one of the most basic things about them, yet I have never seen an answer to this. Capacitors, at least the few I have seen, generally want to release their stored energy all at once. How is this addressed when supercapacitors are used? For example, let's say you have a supercapacitor that can power a light bulb for eight hours. How do you make it actually provide a lower current over those eight hours instead of providing all

      • Re: (Score:3, Informative)

        Capacitors, at least the few I have seen, generally want to release their stored energy all at once. How is this addressed when supercapacitors are used? For example, let's say you have a supercapacitor that can power a light bulb for eight hours. How do you make it actually provide a lower current over those eight hours instead of providing all of that energy in a single instant and frying the bulb?

        By understanding I=V/R [wikipedia.org].

        A capacitor has a certain voltage (whatever you charged it to) and an internal resistance. The load (light bulb) you attach also has a certain resistance. The discharge rate is determined by those two resistances (added together) and the voltage. The "all at once" just means that the internal resistance is almost zero, so if you connect a load that also has zero resistance the capacitor will discharge very quickly. If your load doesn't have near-zero resistance, there won't be any rea

    • by Firethorn (177587)

      At least those undesirable chemicals are pretty much 100% recyclable. For energy storage like this, you need two things. It needs to be cheap per kwh, keeping in mind maintenance and longevity. Efficiency is also huge - a few points of efficiency can make all the difference, cost wise. Still, a lesser factor than cost, especially when you're simply looking at recovering power that would otherwise not be used.

      NiMH is around 66% efficient charge wise, LiIon, though twice as expensive(at this time), is 99.

  • Vanadium redox (Score:3, Informative)

    by rrohbeck (944847) on Sunday December 28, 2008 @03:36PM (#26251237)

    sounds like a cool potential battery technology too. The battery element determines the power, and the amount of energy storage is only limited by the size of the tanks.
    http://discovermagazine.com/2008/oct/29-the-element-that-could-change-the-world/ [discovermagazine.com]

  • by smartin (942) on Sunday December 28, 2008 @03:36PM (#26251241)
    I don't know if this is feasible but I've always thought that a mechanical solution would be better. Use the excess energy to lift a huge weight like the weights on a pendulum clock. When the wind dies down, just let the weight power a generator. Assuming concrete is reasonably environmentally friendly this would be a pretty clean solution.
    • That's being done... with millions of tons of water.
      Millions of tons of concrete would be slightly more difficult to handle.

      • by cparker15 (779546)

        While we're at it, we should find a way to fit a piezoelectric generator into the picture.

      • Re: (Score:3, Insightful)

        Why concrete? Cement is ridiculously energy intensive to produce. Why not stick with water, or if you really want something more complicated to handle but heavier, go with good ol' rock. We'll need to conserver all the cement and steel that we can in the coming years.

        • by smartin (942)
          I figured concrete was heavier than water, but even just wet sand might be good if you can contain it.
    • by slim (1652) <john.hartnup@net> on Sunday December 28, 2008 @04:01PM (#26251451) Homepage

      Assuming concrete is reasonably environmentally friendly this would be a pretty clean solution.

      Concrete has a massive carbon footprint. The calcination of lime releases a lot of CO2, on top of the fossil fuels used in manufacture and transport.

    • by hcdejong (561314)

      Well, to give you an idea of the weight and height needed:
      Dinorwig (a large pumped storage plant in the UK) uses 390 m^3 of water per second and has a water column of 570 m above the turbines to produce 1800 MW.
      So they're using 1.4 million m^3 of water an hour.
      Now a mechanical solution would work differently, but I'd be surprised if 1.4 million tons suspended at 570 m height was not within an order of magnitude for a pendulum storage system that can produce 1.8 GWh. That's quite a lot of weight to be hoisti

    • by An Onerous Coward (222037) on Sunday December 28, 2008 @05:12PM (#26251965) Homepage

      I did some calculations (yay!), and came up with the following: Raising the Empire State Building (365,000 tons of material) to the height of one meter would store a little shy of a megawatt hour of energy.

      I'm imagining this weird future city where the buildings slowly rose and fell as energy was stored and withdrawn. It's a cool thought, but it seems that the engineering difficulties would be considerable, and the payoff not so much.

      A system where water was stored at the top of a skyscraper might be more feasible (putting the weight a hundred times higher means you only need 1% of the material. You might be able to do something with water, or a block on a chain. But the storage payoff seems relatively small.

      It might make more sense to deal with material that's already being lifted up and dropped down. Like integrating some sort of storage and release system for the water already being pumped to the top of skyscrapers. Given separate reservoirs for potable water and sewage, and some leeway about when to pump water in and release waste out, something might be arranged.

      The calculation: 365000 tons * 907 kg/ton * 10 joules/kg * 1kWH / 3,600,000 joules. The 365000 tons figure is from this kid's site [esbnyc.com].

    • Not sure why but I read the title of that post as "Store the energy in a massive virgin".
  • Flywheel energy storage [wikipedia.org]

    "Applications

    Uninterruptible power supply

    Flywheel power storage systems in current production (2001) have storage capacities comparable to batteries and faster discharge rates. They are mainly used to provide load leveling for large battery systems, such as an uninterruptible power supply for data centers.[9]

    Flywheel maintenance in general runs about one-half the cost of traditional battery UPS systems. The only maintenance is a basic annual preventive maintenance routine and replacin

  • Pumped storage is about 60-70% efficient, I wonder how this compares?

    • The wikipedia article on sodium sulfur batteries claims that they are about 90% efficient - which is noticeably better than pumped storage.
    • Re: (Score:3, Interesting)

      by rcw-home (122017)

      Pumped storage is about 60-70% efficient, I wonder how this compares?

      The sodium-sulfur [wikipedia.org] batteries they are using are apparently 89-92% efficient (efficiency should increase with scale - these batteries must be kept at a temperature of about 300C and because of the square-cube law [wikipedia.org] it's much easier to keep very big things hot). Large (>100kW) fully-inverting UPSs are often 94% [mgeups.com] efficient - the rectification/inversion needed for this could be similarly efficient.

  • In my limited experience of using battery banks (2-4 AAs or Cs in series or parallel), the most common cause of failure is having them in series while charging: small changes in cell chemistry mean that the batteries in a pack don't discharge at the same rate, so when you start charging one battery is at 0% and the other at 20%. This kills the battery that was at 0%. Battery life is extended greatly if you charge every cell individually instead of putting them in series (as most home-grade battery chargers

  • Use that.. 54 megawhat hours of storage

    • 54 kWh.

      But not such a silly idea.

      These are 7MWh sodium-suplhur units, with a 1MW output capacity. You'd only need 135 EESU units to match it. A vaguely half-remembered stat puts it's production cost per piece at around $4000, which puts a 7MWh unit at a mere $540,000 ; a snip compared to the $1M dollars for these sodium-sulphur things, without the tribulations of operating at 700 degrees C.

  • If ultra-capacitors become something more tangible than vaporware, I can see this approach becoming much more viable. As it is, with the hidden costs to the environment and economy of chemical batteries, the actual cost-benefit ratio here is a bit more murky, I think.

  • by emandres (857332) on Sunday December 28, 2008 @04:48PM (#26251783)
    1,100 megawatts, eh? Why, that's almost 1.21 gigawatts! Now we just need to come up with a flux capacitor and find an old Delorian!
  • When we put the batteries at the consumer end we have only half the transmission losses, compare to a distributed system like bittorrent.
    Now the world seems to embrace the electric car these can, as long as they are connected to the charging point, be excellent buffers for excess energy.
    • Batteries at the consumer end with local microgeneration would have transmission losses closer to zero, for charge used locally.

      Of course, large centralized projects are more attractive to the pocketbooks of Big Energy.

  • by anorlunda (311253) on Sunday December 28, 2008 @06:38PM (#26252621) Homepage

    I am so sick of science writers who mess up the story because they don't understand the units of energy and power.

    The article says the batteries store 7 megawatt hours. Fine.

    Then it goes on to say "meaning the 20 batteries are capable of delivering roughly one megawatt of electricity almost instantaneously" WTF does that mean? Power, measured in megawatts is by definition an instantaneous unit. What's with "almost instantaneous". Also, the rate of discharge of a battery MW is unrelated to its storage capacity MWh, so the entire meaning of the sentence makes no sense.

    Then the article says, "Over 100 megawatts of this technology [is] deployed throughout the world," Huh? Battery capacity is measured in megawatt-hours, not megawatts.

    Then the article says, "costing roughly $3 million per megawatt" same thing. Battery cost must be proportional to megawatt-hours, not megawatts.

    I suspect that their idea is to make a battery with 24 megawatt-hours of capacity able to deliver 1 megawatt of power uniformly for 24 hours, then say so.

    Shame on Sciam writers and double shame on Sciam editors for not mastering such basic units in an article about energy.

    How about a little economics. The article mentions two understandable numbers, an 11 MW wind plant, and 7 MWh of battery capacity. The combination of the two, allowing for wind variations during the day believably deliver 1 MW continuously to the grid. That's 24 MWh per day.

    Now the batteries cost $3 million, and the wind generators cost $22 million. Total $25 million to deliver 1 MW of base load. That's $25 billion per GW.

    The peak generating capacity of North America is about 750 GW. Let's say 250 GW when levelized to base load. Therefore, to supply 100% of that with wind and batteries would cost roughly $6.2 trillion dollars. Now Al Gore says, "No problem. We can do that in just 10 years." WTF is he thinking?

    Even if we did spend $6.2 T, there will still be periods where not much wind blows for large regions for many weeks at a time. I live where it's cold, and I know that when it hits -30F, the wind is almost always still and the sky dark, and that it can stay like that for a couple of weeks. We therefore, need to double or triple the $6.2T plus more for transmission, to provide backup power sources, plus the means of delivering the energy over large distances.

    Wind and solar are wonderful for up to 15-1-20% of the total grid generation and the cost of construction and operations dominate. More than that, and reliability and deliverability of the electric supply become dominant in the economic equation.

    • by Jeremi (14640) on Sunday December 28, 2008 @09:06PM (#26253591) Homepage

      Then it goes on to say "meaning the 20 batteries are capable of delivering roughly one megawatt of electricity almost instantaneously" WTF does that mean?

      It seems pretty obvious to me... it means that the output of those batteries is available at a moment's notice, i.e. as soon as the operator presses the "gimme battery power" button. Compare that with, say, a natural gas turbine that might need 20 minutes to spin up to full power.

    • Re: (Score:3, Informative)

      by adisakp (705706)
      It was simple enough for me to understand.

      When they refer to "megawatts" in a power plant or storage, they're generally referring to the peak output capability. For example, the 20 Megawatts almost instantaneously would mean the batteries can supply a peak power of 20 Megawatts. The "almost instantaneously" means there is no significant time delay between the request for more power and actually getting the power out (which you might have with a coal fired plant for example).

      The "megawatt hours" defines
  • To me, it seems like the problems of making energy and storing energy are different problems and a good way to store energy has applications no matter how it is produced. Obviously a energy source with no carbon footprint is better.
  • They should be using a thermal energy system. Simply save the electricity as heat and then feed it back later.

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