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Power News Science Entertainment Technology

Miniature Fuel Cell To Keep Drones Aloft For Over An Hour (gizmag.com) 61

Zothecula writes: Drones are being utilized in everything from parcel delivery to search and rescue, but their limited flight times are restricting their ability to travel great distances or stay for extended periods of time in the field. Simply adding more batteries, however, affects flight characteristics and reduces the load the drone can carry. To help solve this problem, researchers at the Pohang University of Science and Technology (Postech) have created a miniature fuel cell they claim not only provides enough energy to keep a drone in the sky for over an hour, but may well find applications in powering everything from smartphones to cars in the not-too-distant future. Developed by Professor Gyeong Man Choi and his Ph.D. student Kun Joong Kim at Postech, the new solid oxide fuel cell is claimed by the researchers to be the first to use porous stainless steel in combination with thin-film electrolyte, all brought together using a technique known as tape casting-lamination-cofiring. Allied with electrodes of low heat capacity, this amalgamation not only results in increased performance, but also in higher long-term durability. The Postech device generates power by converting hydrogen (in this case, "Wet" H2 gas comprising 97 percent H2 and 3 percent H2O mixture) supplied as fuel gas to the anode to create electricity. It does this through the use of a solid oxide material acting as the electrolyte that allows the conduction of negative oxygen ions from the cathode to the anode. These ions diffuse through the solid oxide electrolyte to the anode where they oxidize the fuel. This reaction produces electrons, which then flow through an external circuit to provide power.
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Miniature Fuel Cell To Keep Drones Aloft For Over An Hour

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  • by turkeydance ( 1266624 ) on Thursday March 10, 2016 @07:44PM (#51675227)
    "solid oxide material" anyone?
    • it's notable if they're using stainless steel instead of platinum as the catalyst, but otherwise it's just a SOFC.

    • Re: (Score:3, Insightful)

      by KingBozo ( 137671 )

      You are aware that not all solid Oxide materials are flammable/explosive.

      Fe2O3nH2O or FeO(OH), Fe(OH)3 or Iron Oxides, otherwise known as Rust. Try to explode that.

      • You missed the perennial favourite, dihydrogen monoxide.
        • I have been hearing disturbing rumors lately that the artic is overwhelmed with polution by DHMO-solids ! Though some research suggests that global warming may inadvertently be helping to reduce the levels.

          • It's true, luckily though we can use technology to harness stored carbon ash to amplify sunlight and restore our precious polar jungles.
      • by Anonymous Coward

        You are aware that not all solid Oxide materials are flammable/explosive.

        Fe2O3nH2O or FeO(OH), Fe(OH)3 or Iron Oxides, otherwise known as Rust. Try to explode that.

        Maybe Iron Oxide is not the best of example to demonstrate that some oxides are safe.
        from this article:
        http://ehstoday.com/fire_emergencyresponse/news/need-know-dust-explosions-6171

        "When we understand that fire is a chemical process — an oxidation reaction — we more easily can understand how a seemingly non-hazardous material can become a great fire or explosion risk. In fact, most materials can oxidize. A prime example is iron that rusts, or chemically reacts, to form iron oxide. When we place

        • That actually confirms the GP's point. Rust is not a fire risk - unrusted iron particles are. Rust is the ash that fire leaves behind. Every tried to burn ash ?

    • Oxide, not oxygen (good luck getting the latter solid at room temperature).

      Most oxides are not explosive at all, they're often among the most stable compounds. Most of the earth is built up out of oxides. Many catalysts are oxides - this application is one such example.

  • ... but does it work? Or is it more "10 years out" kind of a thing?
  • I don't understand why they don't just put a small gasoline generator on top. Like, get one of those model airplane engines, hook it up to a generator, and continuously regenerate the battery. Add a small tank of red dye gasoline, and you're set for an indefinite amount of time.

    • Even a very small one plus the fuel tank plus a dynamo equals considerable weight. Plus they run on nitromethane, not on gasoline. Only the biggest ones do that.

      • by fnj ( 64210 )

        they run on nitromethane, not on gasoline

        Sorry. Most model airplane engines run on methanol with which is mixed a proportion of nitromethane - when I was flying, 5% was par, 15% was hot stuff, and 30% was crazy hot. But there are also model airplane engines that run on gasoline, and on diesel fuel. Just about all of them, regardless of fuel used, also require a goodly portion of castor or other oil premixed in the fuel. Not 50:1, like chain saws and old outboard motors - would you believe 5:1. Also, model a

        • So are most model airplanes 2-stage engines then ? Because as far as I know only 2-stage engines ever needed oil mixed in with the fuel, 4-stage engines can lubricate the pistons during the off-phases but 2-stage engines lack those and so must get the lubricant and fuel in at the same time. Such are generally limited to lower-end work like lawnmowers and small motorcycles because the 2-stage engines produce a lot more bad smoke (what with burning much of the oil) and are quite a bit less energy efficient (w

          • Yes, most R/C engines are two-strokes with compression ignition. Maybe things have changed now but last I looked, all the smallest engines ran on the part-nitromethane fuel with gasoline starting to take over in the multiple-cc displacements.

            They DO have four-stroke engines in this size class, IIRC starting around the .21ci models. The ones I've seen have adorable little external pushrods like a Harley, only itty bitty. But I still think you'd have to build a pretty damned big multicopter before it would ma

    • by ScentCone ( 795499 ) on Thursday March 10, 2016 @08:14PM (#51675355)
      For a lot of these applications, the noise would be prohibitive. The weight of the generator may be a problem. And if it's being used for imaging in a stationary hover, the (usually very visible) exhaust cloud from those small engines could be a show-stopper. But I'm betting that an engine/generator/fuel combo with enough output to replace what's coming out of (say) a 6S 8000mah LiPo would be much too heavy.
      • I'm not thinking that exhaust gas is much of an issue in a quadcopter downdraft... but the minimum size and weight of a gas engine, combined with the need for electric motor speed control to stabilize the craft, would mean a very large quadcopter to start gaining efficiency from gasoline as fuel as compared to Lithium Ion cells.

    • by barc0001 ( 173002 ) on Thursday March 10, 2016 @08:27PM (#51675397)

      Efficient gas engines are heavy. Lighter gas engines used in RC applications are not at all what the kids would call fuel efficient and to generate the amount of electricity a normal quadcopter uses they'd probably go though 8 ounces of fuel in about 8 minutes which would actually be a step back in endurance, plus now you've added a whole bunch of moving parts to potentially go wrong. Plus, noise. Plus most of those RC engines are 2 stroke so pollution as well.

      It's only once you're scaling your vehicle up to large drone size that a gas engine becomes reasonable, and that only if your drone is a fixed wing variety.

      • 8 oz of fuel would get you 9 kWh of electric energy. considering this is enough to drive an electric bus 4 miles, i'm sure it would be fine for some drone work. people forget how energy dense fuel is.

        I don't think the noise would be a big deal. have you ever been around a quad? they're noisy as heck from the props.

        • You are assuming that 8kWh is extracted in some manner that approaches efficiency. As I've said, these little RC engines are anything but efficient.

          I own a quad. I can promise you the racket they make is NOTHING compared to what a 2 stroke RC plane motor makes.

          Example:

          https://www.youtube.com/watch?v=2BtCQd7OlOU

          Most lawn mowers and leaf blowers are quieter.

          • right, but the noise from a RC plane is mostly the prop anyways. youd be getting rid of that.

            • Sure that cuts down on the noise problem somewhat (they are still loud sans prop), but you're still left with the inefficiency problem. Some of these motors literally drink 3 oz/minute at full throttle. The more fuel you carry the more weight you have, which means you have to run the motor faster to generate enough electricity to provide lift which means your engine drinks more fuel which means you need more fuel which is more weight....

              • Batteries have 0.5 kWh per kg, and gasoline has 45 kWh per kg. Depending on the weight of the engine and alternator, there's a size where the engine is a better choice than batteries.

                • Edit: source is from Wikipedia.

                • Yes there is, but that size is not the size we're talking about. I'm not sure where the disconnect is, but you're not getting the fact that while there might be 45kWh of energy in a liter of gas, you're going to MAYBE extract 4 or 5 kWh of it with that RC engine and the rest will be wasted as heat or not even burned and blown out as part of the engine exhaust. And in order to take advantage of that fuel system you will need to add the weight of a gas RC engine:

                  http://www.horizonhobby.com/airplanes/airplan

                  • worst case the engine is 33% efficient, which is 15kWh, not 4. Also, that's still 30x more better than batteries. a kg of fuel + a kg of engine/alternator would still be 10x more energy than 2kg of batteries. It's clear that you need a bigger drone for this to work, where the weight of the drone itself > the weight of the engine. Maybe tabletop sized? or car sized? there's a size at which it makes sense.

                    maybe you're overly focused on the radio shack drone world. there's more to explore than that! once y

                    • > worst case the engine is 33% efficient, which is 15kWh, not 4

                      ???? Have you ever seen the efficiency reports for full size gasoline powered car engines? Spoiler alert - they are less than 20% efficient power from the gas to the wheels, in many cases under 10% after the drivetrain eats some.

                      https://en.wikipedia.org/wiki/Internal_combustion_engine

                      "Most steel engines have a thermodynamic limit of 37%. Even when aided with turbochargers and stock efficiency aids, most engines retain an average efficiency

                    • > You are not going to get an efficient gas powered quad that's any smaller than a large dinner table.

                      ok fine, build one the size of a dinner table! that sounds awesome! give it like 12 blades and call it a dodecacopter. that shizz would be dope.

        • 8 oz of fuel, plus 16 oz of engine to burn it in, plus another 16 oz of generator and capacitor to create energy flexible enough to stabilize a quad (electricity). A straight mechanical prop drive and control system for stabilization of a quad would be rather hellish to build and maintain.

          • I think that's an understatement. I don't think it would be possible at all, the constant adjustments needed to keep a quad flying or actually direct it would be almost impossible to make with direct mechanical input without some super fancy clutches that would probably tear themselves to shreds in a few minutes.

      • by swb ( 14022 )

        I'm curious if a drone could be built that uses a lawn mower or weed trimmer gas engine directly as the power source (skipping the electric generation part). A helicopter design seems reasonable but I can see where a quadcopter might be impractical from a transmission perspective.

        I know they make RC turbines for use RC planes and helicopters, perhaps a quad-turbine quadcopter to avoid the transmission gearing? The turbines are really expensive, but I would imagine for deep pocketed organizations, a quad-t

        • You could build a fixed wing drone but it would have to be considerably larger, like 7+' wingspan larger. A quad you couldn't, the only reason quads are able to fly is because the controllers make minute adjustments to their thrust based on feedback from the gyros and they also drop or add extra power to one or more rotors based on the input commands from the operator. Trying to do that with mechanical input shafts would be impossible without some sort of incredible fast transmission systems.

    • by raymorris ( 2726007 ) on Thursday March 10, 2016 @11:11PM (#51675827) Journal

      I decided to do the arithmetic because I know that diesel locomotives do just what you described.

      I looked at the ratings for a sample glow-plug engine consuming 1 fluid oz of fuel per minute, and found it can produce about 1300 watts. That's more than I expected. A fluid once of fuel weighs about an ounce, or 28 grams. So 1300 / 28 = 46.42 watt minutes per gram. We normally use watt /hours per kg for these things, so we do the arithmetic and get 774 watt hours per kilogram for the nitro engine.

      Lithium ion batteries are about 200 W/h / kg. So the fuel, run through a nitro motor, DOES have more energy than a battery of equivalent weight. The fuel weight also goes away as it's burned, whereas a battery stays the same weight.

      HOWEVER, the engine weighs 17 ounces (486 grams). Add to that a small alternator at let's say 10 ounces. You'd have 27 ounces of engine and alternator to burn the 12 ounces of fuel, and your total specific energy comes out about the same as the battery.

      if you can get X energy from either a battery weighing 27 ounces or an engine/alternator/fuel combination weighing the same, the simpler choice of just a battery makes more sense.

      If you REPLACED the electric motors with engine(s) instead, that might make sense. It does make sense when you only need one, in a plane or helicopter. For a quad, you'd need either four engines or a complicated adjustable belt-drive system. Electrics make more sense for small quads.

      On a land or sea vehicle, you can carry much more fuel in relation to the engine size, and volume is as important as weight, so fuel makes more sense than batteries.

    • Now, THAT would be the ultimate final solution: a nuke-powered drone!

  • by wvmarle ( 1070040 ) on Thursday March 10, 2016 @08:21PM (#51675379)

    How the hydrogen is stored and supplied to the fuel cell is my biggest question.

    The gas is infamous for requiring very high pressure and very low temperature to remain liquid, and even then has pretty low energy density (large volume, however low weight - but the heavy tank takes away that advantage). Wondering how they solve that for an application where limiting size and weight are paramount.

  • by queazocotal ( 915608 ) on Thursday March 10, 2016 @08:29PM (#51675401)

    Over an hour is quite possible with conventional drones - there is a tradeoff between prop diameter and power usage - most quads optimise for low prop diameter for performance reasons.
    http://www.rcgroups.com/forums... [rcgroups.com] >2h flight.

    • most quads optimise for low prop diameter for performance reasons.

      And size reasons! The quad you linked is almost twice as big as a normal camera carrier.

  • They say, "peak power density of 560mW cm2 at 550C" but don't list the room temperature of the container.

    At that level of information I could put the room to -50C and publish values that are irrelevant within normal operating temperatures on planet earth.

    Who made this shit? Knowing it's an Oxide at least is nice.

    • by Ungrounded Lightning ( 62228 ) on Thursday March 10, 2016 @11:37PM (#51675881) Journal

      They say, "peak power density of 560mW cm2 at 550C" but don't list the room temperature of the container.

      What matters is how hot it is at the oxygen transport site - which is heated by the losses (because this is high energy, insulated, and less than 100% efficient.). Some solid oxide cells can run VERY hot - like orange - no problem.

      You have to insulate them anyhow, to keep them hot, so the oxygen ions will be mobile enough for them to work at all. If they're running at 550C and were designed for a 25C room environment, running them at -40C (where C and F come together and mercury freezes) requires increasing the amount of insulation by less than 13%.

      It's about time somebody made them out of thin films, so they can start up quickly and are small and light. Making them tiny also shrinks the insulated container. Big win.

  • ...well, hopefully not fuel that you burn all at once.

    Sooner or later, helium is going to be too expensive for even the military to use it in large lighter-than-air craft. We'll have to move to using hydrogen. As long as we've got a big bag of hydrogen, why not use some of it for fuel?

    I wanted to do something like this when I first learned about fuel cells back in middle school. I didn't know much about fuel cells, as it turned out. I also didn't have a platinum budget.

  • ... they should have posted my submission about Ardupilot continuing on as nonprofit.

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