back to article DARPA aims to make renewable power practical at last

Pentagon boffinry bureau DARPA, which deals with established technology paradigms in much the same way as Patrick Swayze and Demi Moore dealt with clay in their 1990 supernatural romanta-flick outing - that is as material for squidging into improbable shapes so as to satisfy the squidger's raging occult lusts - has done it again …


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  1. GCom

    Pneumatic or Flywheel storage anyone?

    Is it just me or does this typically DARPA request sound like a job for pneumatic, hydrochloric or flywheel storage, all have a growing pedigree in national and renewable energy storage.

    This all said its most certainly the case that as the human race we are not good at storing energy and its certainly a barrier to the next generation of energy intensive technologies being practically employed

    1. Anonymous Coward
      Thumb Down

      flywheel mass

      For a flywheel with that potential you can rule out a truck!

      1. Andy Howarth

        Add the mass onsite

        Maybe a complete flywheel with that kind of mass would be a problem but what about the skeleton of one that then has additional mass added.

        Hesco bastions are a good example of this where what's transported is merely a container that's filled with earth, rubble etc on site.

        I admit, there are lots of issues around balancing etc but to me converting it to some sort of kinetic or potential energy makes most sense.

        1. Naughtyhorse


          lots of issues

          i hear you, even over the rumbling of that dirt flywheel a mere 150 miles away

        2. Anonymous Coward

          No can do...

          eurgh no way it needs perfect balance, and it needs to maintain perfect balance at 10,000G or more if you want it to work!

          Gravel definitely will not do! Nor concrete, it needs to be a high tensile construction with perfect balance and heavy Mass.

          1. Dashby

            what about water?

            What about shipping empty hard shell containers that interlock into a cylinder and filling the containers with water. As more storage is required more devices can be added.

            In a cylinder of water with dimensions 2m radius, 10m high, rotating at 5,000 rpm the kinectic energy is around 34 mega watts.

            The only problem I see is that the centrifical force on the outside of the container would be close to 7,000 tons and it would have a static weight of 125 tons All calculations do not take into account the container.

            As for balancing, if water is used a automatic system to pump water from one chamber to the other to achieve an intial balanced state could be created.

            The only problem I see is that it is too simple for the DARPA bofins.

      2. Anonymous Coward
        Thumb Up

        Couldn't you

        hold the same power by making it spin really, really quickly? Active magnetic bearings, flywheel spun in a vacuum, mounted on a mechanism based around a clay pigeon launcher so it can be flung away in the event of impending failure.

        1. Anonymous Coward
          Anonymous Coward

          Na na na na...

        2. Paul 129


          "flywheel spun in a vacuum, mounted on a mechanism based around a clay pigeon launcher"

          I'd like to see that on you tube. Up close? Nothankyou!

      3. Mips
        Jobs Halo

        Flywheels a no no: I don't know about that...

        ...some years ago composite flywheels were proposed with TJ capacity. Big truck. Yes, maybe several. But it was supposed to be doable. Thing is I never heard of them since.

    2. Jellied Eel Silver badge


      May result in rapid energetic dissasembly of said flywheel plus containment structure. Might not be ideal or safe in a base.

      Fuel cells might be better, although saving the water exhaust for re-use is possibly not the best use. The exhaust water is hot, so showers!

  2. Tom 7 Silver badge


    I regularly go diving with air compressed to over 232bar on my back and having dropped tanks onto the road at speed can vouch for their solidity. Its not new technology and to store large volumes of hydrogen at that sort of pressure is not noticeably more risky than storing petrol in quantity - maybe not for transportable required in this case but for local storage and perhaps hydrogen for cars in in a renewable world it does represent a feasibly option.

    As for electrical->H2->electrical inefficiency >80% was achieved in the early 90's .

    This sort of approach has been practical for a long time and the only reasons why it hasn't been researched much are lack of will and lack of potential profit margin as most of these technologies will be very low cost in mass production quantities. A 1kw grid connected inverter using a monolithic solid state unit should cost around $10 for the silicon plus transformer + case + licensing but will set you back over £500 for a hand soldered job.

    1. lglethal Silver badge
      Thumb Up

      Just a small point...

      Have you tried shooting your tanks? ;)

      I suspect that might be the discouraging factor for a Forward Operations Base in a war situation.

      Otherwise I agree with what you say, Tom!

      1. Wize

        But batteries...

        ...have a fire breathing capability when damaged. Perhaps some sort of protection. Probably the same you'd have on your fuel tanker.

        Most energy storage solutions will have some sort of problem when damaged.

    2. Steven Jones

      Hydrogen economy myth

      The idea that hydrogen makes any sense as an energy storage system is a persistent myth. When you take into account the full life cycle only about 25% of the original energy content used to produce it will be available for use in a fuel cell. On top of that, it's bulky - even under very high pressures or even liquefaction. The very compression (or liquefaction) of hydrogen uses a very high proportion of the energy content. Because hydrogen atoms are so so small it is notoriously difficult to keep under very high pressure - it tends to percolate through liners and does bad things to the tank material over time. Diving tanks are simply unsuited to this purpose - they have to be built to a much higher level.

      Only for a few uses does hydrogen make much sense - whilst it's bulky, liquid hydrogen is at least light, so it makes sense in space rockets where the energy lost in liquefying it is not the most important issue.

      Pretty well nothing (at least chemically) beats the energy density of liquid hydrocarbons. It would make more sense to find an artificial way of generating those (perhaps using genetically engineered organisms and sunlight) rather than taking the high thermodynamic losses in spitting water by electrolysis and compressing or liquefying it then somehow finding a way of flying a 'plane using the stuff.

      Small nuclear reactors also don't make much sense - for those to operate you need copious supplies of cooling water. That's fine in a submarine, or a ship which are, literally, surrounded by oceans of the stuff, but it's hardly going to work in a desert where even drinking water might have to be shipped in.

      Here's one simple link to the basic overheads.

      Yes, and for those who know about these things, there is talk of using electrolysis under high-pressure to avoid much of the compression energy costs, but it's all rather speculative.

    3. Trygve Henriksen


      While a full Hydrogen tank might not explode if it was shot once, it will leak, and the next bullet, possibly a tracer or incendiary would do the job.

      The solution could be to build a protective structure over the tank, or even bury it underground. But both alternatives takes time and resources, which is something you don't always have when setting up a FOB.

      Now, what really boggles the mind is trying to set up a wind-farm or solar panels to gather the power in the first place. I wonder if that stuff will come with nice, big bullseyes already painted on them...

      1. perlcat

        Darpa's been eating the green muffins again.

        Wind? makes no sense. Maybe they can mount the windmills on the trucks, and drive them around in circles to generate electricity. /sarc

        These sort of plans only make sense at 2 am, immediately before eating a whole mound of Doritos.

    4. Mips
      Jobs Halo

      H2 Ha! Ha! Ha!

      Cylinders are not the issue. Tis hydrogen that is the trouble sir. It is very easy to ignite and if there is a leak there is likely to be an explosion. We go to great lengths in designing battery charging facilities to ensure hydrogen can get out of a building and not accumulate under the roof.

      Basically if you have a 100ton H2 storage that is the same as a 200ton bomb. Do you really want that in your FOB compound?

  3. Anonymous Coward

    If trucks are the key criteria...

    Then the energy density Per Litre of the fuel is more important than the energy density per KG..

    That's going to rule out any form of Hydrogen totally. Perhaps Methanol fuel cells? but methanol synthesis? hmm this is going to struggle to compete with oils.

  4. MyHeadIsSpinning

    Old news?

    FTA: - 'to store surplus power from the renewable generators when output is high, and use this stored juice to make up the shortfall when the sun goes in or the wind drops.'

    Yes, and? Is this new? I could have sworn that I read about people doing similar years ago, although they probably called it something different than 'deployed energy' whatchamacallit.

    It's what batteries are for, surely?

    1. lglethal Silver badge


      Didnt you see that Lewis mentioned Li-ion batteries and discounted them based on the massive requirements DARPA want handled and the ability to fit on a reasonable number of trucks...?

      Seriously try reading the article next time...

  5. Stephen Sherry

    Nuclear FTW

    I had a acne, and put nuclear on it, and it cleared right up.

    But seriously, DARPA is pretty good at what they do, I'd be willing to bet that whatever they come up with will be quite interesting, and make us all go, "why didn't we try this before?" Though usually the answer ends up being, because the energy industry makes less money if they always do R&D, than just re-marketing what they are already selling (thing that make fire, GOOD!). In fact, every industry tends to do that right up until there is competition in their market.

    A few years ago they proposed to the congress under Bush 2.0 that they were interested in releasing secret tech in the hopes of benefiting the general public, and the economy.

    1. Oninoshiko


      Actually, DARPA are notoriously BAD at what they do.

      If anything comes out of this, it will probably something totally unrelated. I'm hoping for the cure for cancer.

  6. Wize

    Even if it was there a while...

    "Basically for a li-ion DES to involve fewer truck deliveries than normal diesel generation, your FOB would need to be in place for decades."

    The batteries would need replacing several times during that time.

  7. Anonymous Coward
    Anonymous Coward

    50% solar

    DARPA have also had a long-running project to get 50% efficient solar cells for grunts to carry around to reduce the amount of batteries. Last I knew the best achieved in a lab* was 42.9%.

    I'm sure that even though they'd like super-duper renewable back-up storage they'd probably settle for super. After all, diesel supplies aren't reliable either, although they get interrupted by bombs rather than clouds.

    * Obviously an outdoor one.

  8. The Prevaricator

    wot? no shale gas?

    Come on Orlowski, your cause is flagging a bit with all this negative press about it being "about as greenhouse gas emitting as coal".

    In all truth, hydrogen is an excellent energy storage medium. People just assume it's going to be wildly inneficient, hazardous, bulky, or all three. This really is rather unjustified. ~700 bar storage vessels are slowly becoming standardised for vehicular applications, so it is only a matter of time before somebody does something useful with it.

    You don't need to be as loopy as DARPA to see this.

  9. Charlie Clark Silver badge


    Aeoliosynthesis: don't bother with hydrogen, just make a hydrocarbon from ambient air and water. Simple alkanes are pretty easy but real boffins might aim for synthetic oil which could be used for vehicles as well. Yes, it's poor efficiency but it's great for storage and flexible in use.

  10. Christoph

    The answer is obvious

    This is DARPA we're talking about, after all.

    They want the best power storage possible, however loony it is.

    They're going to store it as antimatter.

    1. lglethal Silver badge


      Antimatter is old hat, CERN have already done it.

      Havent you read Dan Brown?

    2. Mike Richards Silver badge


      As you said yourself - this is DARPA. You aren't thinking crazy enough.

      They'll store solar power as biomass in giant hydroponic gardens fertilised by squaddie crap. The plants will then be fed to the genetically modified cyborg slugs which in turn will be consumed by the flesh devouring killer droids.

  11. Anonymous Coward
    Anonymous Coward

    What about supercaps?

    A large container stuffed to the brim with super- or ultracapacitors should hold a bit of a charge, though I can't be arsed to work out the resulting capacity. Oh wait, this here datasheet has Wh numbers. Ok, so, er, that's, er, maybe, er, something like this thereabouts then. Make that roughly somewhere along the lines of 20kWh per shipping container give or take some generous number. Hm, not beating LiIon yet. Oh well, worth a try.

    Apropos flywheels, I read somewhere long ago they'd hold more capacity when they're light, like made our of kevlar fibre or something, and spun really fast, like on the order of 30kRPM. And in a vacuum and with at least one magnetic bearing. No idea what the resulting energy density of that would be, though.

    The problem with hydrocarbons and anything else that needs fuel is that you can't easily charge it with a bit of surplus 'leccy, which seems to be a rather important goal. A couple MW genset already fits in a shipping container and they already know about fuel logistics so that's no challenge for the military at all. But a sufficiently large storage bank buffer would be useful next to gensets just as it would be next to these unreliable sources, if sufficiently efficient.

  12. jonnyrad

    What about sodium?

    7.2MWh sodium suphur battery 'packs' which go onto 2 trucks have been available for a few years. So that’s eight trucks for almost 30MWh with commercial technology. Not unreasonable for a DARPA project to be pushing the boundaries a bit: it's advanced research, not procurement.

    And as NaS batteries were developed in Japan by NGK and TEPCO, I have full confidence in their ability to withstand any hazard with no measurable health consequences. errr


  13. Dani Eder

    Vanadium Redox batteries

    Recently improved vanadium redox batteries can store 1.4 MJ/liter of electrolyte with 90% efficiency. Diesel stores about 38 MJ/liter, of which perhaps 30% makes it to electric in the generator, so a net of 11.4 MJ/liter electric. Thus redox batteries win on volume after 9 charge cycles. Electrolyte solution is somewhat denser than water, while diesel is somewhat lighter, so breakeven by weight is more like 15 cycles.

    If you get your water locally, and only bring the electolyte mix, the breakeven by weight might be quite a bit better. Deserts don't have a lot of water, but nearest water supply is probably a lot closer than nearest fuel depot, and you only need it once to mix up the electrolytes.

  14. Yet Another Anonymous coward Silver badge


    Most wars today are "asymetric conflicts in human resource rich countries" = us with guns, them with lots of non-white people

    So simply round up 1000 of them, put them on a treadmill, @150W each you have 150KW for as long as you want. Optional power boost available with well known whip technology.

    In conflicts closer to home where either the locals are too fat and lardy to be of any use, simply exchange for squaddies. With the correct inducement you could probably get more than 150W out of them and at worst they would get fit

  15. John Smith 19 Gold badge

    A note on flywheels.

    They do store better faster.

    Some of the lightest were based on the technology used in Uranium gas centrifuge technology.

    Hollow carbon fibre cylinders

    Rotor pattern impressed on iron based ink in the skirt.

    High vacuum for minimal windage losses.

    The joker in the pack is the trade off between "cleverness" factor and robustness.

    Note. Wide and flat is better than narrow and tall. Faster is *better* by a lot. 2x speed -> 4x energy storage.

  16. Mips
    Jobs Horns

    Geostationary generating satellites

    This is old hat but maybe DARPA can get it off the ground. They would be steerable to target the FOB energy collection area. If no operations are current then they could be put to civilian use (fat chance of that).

    Of course DARPA black hats could propose they be weaponised to defend the FOB, might even be better than Reaper .

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