UAVs Go Green With Fuel-Cell Powered "Ion Tiger" 83
Hugh Pickens writes "Increasingly, the military is deploying unmanned aerial vehicles, or UAVs, as eyes in the sky to scan the ground for targets and threats, especially for missions that are too dangerous for manned aircraft. Now Live Science reports that a new robotic spy plane called 'Ion Tiger' will harness alternative energy to make it more covert and longer lasting than battery-powered or engine-powered UAVs. A 550-watt, 0.75 horsepower hydrogen fuel cell will power the Ion Tiger with four times the efficiency of a comparable internal combustion engine and seven times the energy of the equivalent weight of batteries. When Ion Tiger took flight in October, it exceeded any demonstration of electrically powered flight so far, flying 23 hours and 17 minutes. 'And it carried a 5 lbs. payload to boot — enough to carry, say, a day-and-night camera,' says researcher Karen Swider-Lyons, head of the alternative energy section at the Naval Research Laboratory in Washington. 'No one has come close to flying 24 hours with a significant payload before.' Another big advantage is the Ion Tiger's reduced noise, heat and emissions. 'Think about lawnmowers or chainsaws — they're really loud,' says Swider-Lyons. 'It's hard to spy on people when they know you're there, so you had to fly them at high altitudes to keep them from being heard.'"
Huh? (Score:5, Informative)
When Ion Tiger took flight on October, it exceeded any demonstration of electrically powered flight so far, flying 23 hours and 17 minutes.
No it didn't. Have they never heard of the Qinetiq Zephyr [wikipedia.org]? It flew for 82 hours.
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The Ion tiger has a 2.5 meter wingspan. The Qinetiq Zephyr has an 18 meter wingspan.
You cannot seriously be trying to compare the two.
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Why not? Both can haul a ~5 pound load yet the solar/lithium*sulfur battery combo allows the 18 meter wingspan Zephyr to fly 3x as long. Swap out the battery for a fuel cell and an electrolysis cell and the craft might be able to stay up indefinitely. That is if we can ever get the electrolytic efficiency a bit higher than it is now.
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You think solar+electrolysis+fuelcell can be more weight/power efficient than solar+battery? I'm highly skeptical.
Re:Huh? (Score:4, Insightful)
Oh, I'm sorry -- point to me where they had a wingspan restriction in their unconditional statement.
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But still it's for spying. Everything else being equal, it's harder for something with a 2.5m wingspan to be spotted than something with an 18m wingspan.
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They didn't state a restriction but given size of the plane demonstrated, its likely there is an obvious restriction which makes the Zephyr just plain silly to bring into the conversation. Most tactically deployed UAVs are carried and launched in the area where they are to be used. That's simply impossible with an 18m plane.
His statement should likely be framed within context of what's being evaluated and how its to be used. That context was likely lost in the article - or they presumed the reader wasn't an
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"Something else you seem to ignore is large wings, while providing for lots of lift, directly translate into higher drag"
WTF?
The higher the aspect rario of a wing the lower its drag.
As English designer and glide manufacurer Fred Slingsby famously put it, "There is no substitute
for span".(In terms of increasing a wings efficiency)
The smaller the chord of a wing the lower its reynolds number, hence less efficient.
Try googling Aspect ratio effects and reynolds numbers.
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You're not telling me anything I don't already know.
A larger wing always means increased drag. Given two wings with the same aspect ratio, one being larger, the larger has more drag. If this were not true, all planes would have massive wings as there would be no penalty for doing so.
WTF is right.
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For a given span the higher the aspect ratio the lower the drag at the low speed end of the low drag bucket.
If one designs a wing to produce a certain wing span the the bigger the aspect ratio the LOWER the drag at low speed, but the lowest speed ios then higher.
To make it really simple, my 3 meter model can never be as efficient as a 15 metre span glider.
Of course a larger wing produces more drag, AT the same Co-efficient of lift. IF you use the extra lift available the drag would be higher. If not then th
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Something tells me there was a whooshing sound which you ignored.
Re:Huh? (Score:5, Informative)
Also on the subject of misleading claims:
A 550-watt, 0.75 horsepower hydrogen fuel cell will power the Ion Tiger with four times the efficiency of a comparable internal combustion engine
That would mean an efficiency of greater than 100%. Which is obviously nonsense. ICEs are generally 35-45% efficient in peak operation. If you want to say that you're not comparing peak operation, then you can't compare fuel cells at peak operation, either. For example, when driving the NEDC (the New European Drive Cycle, one that generally is gentler than our combined city/highway cycles), the tank-to-wheel efficiency of a fuel cell stack is about 36% [sciencedirect.com] (gasoline engines in the NEDC are generally 20-25% efficient, and diesels, 25-30%). Even at low, steady loads, fuel cells are about 45%. And that's tank-to-wheel -- i.e., doesn't include the losses in making hydrogen, which are significant. Yes, you can get really high efficiencies, 50-70% or so, with fuel cells in the lab. But to do that, you have to feed them pre-compressed oxygen rather than low-pressure air, and not count any accessory loads.
and seven times the energy of the equivalent weight of batteries
Notice they chose the one metric that favors H2 -- rather than, say, volume, durability, power, price per watt, fuel price per energy or fuel price per watt, or any other such metric that fuel cells bomb at. And they're almost certainly just comparing the fuel, ignoring how heavy the fuel cell stack is.
Another big advantage is the Ion Tiger's reduced noise, heat and emissions.
Fuel cells lose out to battery-electric in all three of those regards.
Now, I will say that UAVs are a better role for fuel cells than cars -- steadier loads, cost is less of an object, and a higher percent of the vehicle's mass needs to be energy storage. But they still aren't very attractive.
Re:Huh? (Score:5, Insightful)
That would mean an efficiency of greater than 100%. Which is obviously nonsense. ICEs are generally 35-45% efficient in peak operation.
Yeah, that thought crossed my mind, too. But "efficiency" can mean different things depending on context. You could mean "time efficiency" - how much time gets wasted getting a job done, which would be irregardless of other resource usage. You are talking about "efficiency" in terms of ability to convert chemical energy into mechanical energy, and you are right, there.
But read the article. By context, I think they are actually talking about strength-to-weight ratio - how much useful power you get per pound of fuel/battery/engine. Combine that with the informal nature of the article, and it kinda makes sense that way.
Me? I'm curious about a system with obvious advantages for private aviation:
1) Better power/weight ratio, which is big. Even in a fairly substantial Cessna 182, when you take off with full fuel, you have to be honest in considering the actual weight of your passengers.
2) Fewer moving parts: Few pieces of equipment rival the reliability of an electric motor. If fuel cells are a simple chemical process without moving parts, the chances of failure could potentially drop through the floor. And that makes flying safer for everyone - most importantly, me.
Everything about a plane is about reducing failure rates. They are expressly designed to reduce mechanical complexity to reduce the chances of failure. The fuel mixture on a private plane is adjusted manually. The throttle is very simple. There are actually two ignition systems on each plane, and rather than use an electrical coil like a car, they each use an independent magneto system, like a lawn mower, so that an electrical failure (like a blown fuse) won't stop the engine from working.
If you could reduce the number of moving parts to ONE.... wow. That would be... AWESOME.
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He's not talking about a commercial airline. He's talking about small private planes [phazeddl.com] for private use.
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lol, wrong damn copy buffer. god I hate this WM.
Try this URL instead:
http://images.google.com/images?hl=en&safe=off&client=iceweasel-a&rls=org.debian:en-US:unofficial&resnum=0&q=cessna&um=1&ie=UTF-8&sa=N&tab=wi [google.com]
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and.... you could have figured out what I was talking about by looking up "Cessna 182" on Google...
Also, "1 moving part" could easily be defined as an electric motor with a prop bolted on. Not that the "1 moving part" couldn't be dissected, but that, when they are bolted together, they move together without friction between the parts. They function as "1 moving part" and this increases reliability.
But since you're commenting, what do you mean by "uses direct fuel"? Jets are fast because they aren't limited
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"But they're still both guns!"
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ICE's are generally most efficient at 60-80% of max hp at optimum rpm (less so at full or "peak" power, and less at lower power). Certainly 35-45% thermal efficiency at the highest efficiency operating point is achievable, but I don't think any available lightweight 0.75 hp ICE's come anywhere near that much. Maybe half; maybe less. Glow plug model airplane engines are fantastically inefficient; spark ignition somewhat better.
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The article didn't mention the craft having solar power as well to boost the amount of power available so it may still be the longest duration flight of any non-solar powered craft to date. Aircraft that use fuel cells + solar powered electrolysis have been speculated to be able to fly indefinitely if properly engineered. The solar power powers flight during the day and produces hydrogen from electrolysis and the fuel cells power the craft at night.
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"Fuel cell plus solar powered electrolysis"? Yeah, throwing away 70-80% of your energy is a good way to stay aloft, right? Low loads on a fuel cell means tank-to-drive efficiency of ~45%, and small-scale electrolysis tends to be very inefficient, generally 50% or less (the big steam electrolysis systems are more efficient).
The Zephyr stayed aloft with lithium-sulfur batteries. Being still experimental, they don't have a very long cycle life yet (although there have been some big lab breakthroughs in this
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very high efficnecy cells can have efficiencies over 60%. High temperature electrolysis can get around 60-70% electrolytic efficiency. For larger craft, the higher energy density of Hydrogen would start tipping the scale in favor of fuel cells owing to the weight reduction from not having to tow the extra weight of the lithium/sulfur battery material.
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very high efficnecy cells can have efficiencies over 60%
Yeah, if you feed them pre-compressed oxygen.
High temperature electrolysis can get around 60-70% electrolytic efficiency.
Good luck fitting a high pressure/high temperature steam electrolysis system on a UAV.
For larger craft, the higher energy density of Hydrogen would start tipping the scale in favor of fuel cells owing to the weight reduction from not having to tow the extra weight of the lithium/sulfur battery material
No, it will always be offset by
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When Ion Tiger took flight on October, it exceeded any demonstration of electrically powered flight so far, flying 23 hours and 17 minutes.
No it didn't. Have they never heard of the Qinetiq Zephyr [wikipedia.org]? It flew for 82 hours.
The article claims that it is record for a fuel cell powered flight - not an electrically powered flight.
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Right, but I don't think that vehicle would make a very good spy plane ;)
With an 18+m wingspan, it's rather hard NOT to see it.
Green don't matter (Score:3, Informative)
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The fuel cel is only green if you are separating the hydrogen and oxygen using power from a nuke plant. Otherwise it costs a tremendous amount of fossil fuel energy to separate the hydrogen.
The only truly green fuels at this point are hydrogen and electricity from nuke plants, perhaps supplemented by solar and wind, although the later two are extremely expensive per watt in comparison, as well as extremely inefficient land-usage wise.
--M
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Wind is quite cheap actually, even compared to modern nuclear power plants -- as long as you compare actual price for e.g. the new Finnish plants instead of prices in the budget. Like other large projects, nuclear power plants have a notorious tendency to cost more than expected. Wind turbines on the other hand are off-the-shelf.
If you're trying to create hydrogen wind turbines are fairly good, but they can't beat just cracking natural gas cost-wise. You can use heat from nuclear plants directly to create h
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Right. How does the army get its electricity in Afghanistan? A very long cable from the ÜS, or Europe, or India?
Of course energy efficiency matters for the army. More often than not they have to bring diesel in with trucks and run generators.
These convoys are expensive and vulnerable. Tons of black coal are definitely out of the question.
easy fix (Score:3, Interesting)
Just pay some neighbors to mow their lawn all day so that nobody knows the difference.
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Some UAVs really, really sound like lawnmowers flying above you. It's easy to tell when they're in the skies above you.
The bits of grass falling on your head should tip you off.
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if you can hear it , It has been watching you for a long time already.
Re:easy fix (Score:4, Funny)
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P.S. And I want a divorce, you lazy blister-butted cheap-pizza-smelling nerd!
Tiger in the tank (Score:2)
ion + tiger = (Score:2, Funny)
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tigerion. TIE-gair-EE-on.
Great place for a fuel cell (Score:4, Insightful)
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maybe... maybe not. Direct carbon fuel cells [wikipedia.org] can have efficiencies topping out at over 70% and some can run on hydrocarbon fuels commonly used in aircraft. They have efficiencies higher than any combustion engine and far, far higher energy density than any known battery by a wide margin, Battery technology would have to improve *dramatically* to even come close to beating these.
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The hummingbird laughs at your 5 pound capacity (Score:1, Informative)
Nobody has heard about the OFFICIAL holder of the rotocraft endurance tests? Boeings A160.
"It was the longest un-refueled flight of any rotorcraft, and the FAI has awarded Boeing the official endurance record in the 500 kg to 2,500 kg autonomously controlled UAV class for the flight.
-Staff. "Unmanned Aerial Vehicle (UAV) World Records". Fédération Aéronautique Internationale. http://records.fai.org/documents.asp?from=u&id=15059. Retrieved 2008-11-30."
http://en.wikipedia.org/wiki/Boeing_A1
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Also, do you think that the hummingbird can use less fuel than this? Again I doubt it. Keep in mind that these is intended for a place like Afghanistan where it costs money to bring fuel. You hummingbird will suck the fuel out in one trip, what this would use in a year.
Size difference (Score:2)
Your is the size of a normal passenger carrying helicopter, theirs is the size of a model plane.
Somehow I think your thingy requires a LOT more in terms of support then theirs.
Theirs can be carried by a field unit, yours needs a support base.
Why can't you spot this simple thing by the fact yours comes on the back of a large truck while theirs is carried by hand?
Thanks for the redundant unit conversion! (Score:2, Interesting)
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"The dimension of power is energy divided by time. The SI unit of power is the watt (W), which is equal to one joule per second."
Horsepower is a non-SI unit. "One horsepower is equivalent to 33,000 foot-pounds per minute, or the power required to lift 550 pounds by one foot in one second, and is equivalent to about 746 watts."
550 watts would be 0.74 horsepower but why even bother with horsepower? Only cowboys and the idle rich use horses.
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Can't we all just stick to SI units to avoid problems like this?
It is very obvious that we cannot. why did you even bring it up?
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While SI is is a bit more consistent that Imperial/US customary units (would be nice if the unit of length was the light-nanosecond), there are cases where calculations are easier to do in "English" units than SI. An example is calculating the power in HP required for an airplane in level flight which is simply the product of weight in pounds times speed in MPH divided by
Tesla (Score:2)
One of these small cells in a Tesla would make it an awesome car. Two of them in a Tesla would make it an even more awesome car. I really think the future is fuel cells, not batteries. Batteries are just a 'bridging' technology until we have overcome all the challenges surrounding a conversion to fuel cells and hydrogen fuel.
Just the opposite (Score:4, Insightful)
Far more problematic, production and transportation of hydrogen will remain highly inefficient compared to battery or far more likely ultra-caps. Oddly, I have seen the pro-h2 side claiming that it is more efficient to build fueling stations in which the hydrogen is generated from water vs. batteries. So, now, they want to transmit the power the same distance and then convert, store locally, fuel a car, store on the car, convert to electricity vs. storing on a battery. Keep in mind that each step has lose of efficiency, and batteries are more efficient than any of the steps just mentioned (and one step vs 4).
The only issue will be energy density of a battery/ultra cap. And that is increasing rapidly. Even now, the lithium air with 10x increase in energy density over lithium ion, will likely take out all hopes of the fuel cell being a commercial success.
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Let's see who is right :)
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Eventually they will have to. I am afraid though, that they first will tap the enormous coal resources in Africa, wreaking havoc in the communities there in the process.
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I know that. It is the result of George's 'green' plan, which he launched a couple of years ago to show his concern about the environment^H^H^H^H^H^H^H^H^H^H oil companies.
For domestic use only (Score:1, Troll)
'It's hard to spy on people when they know you're there,
Ask yourself: why care of the targets know they're being watched? In a hostile situation this acts as a a means of suppressing activities - the bad guys won't enact their badness while there's a drone buzzing around. That's effectively what you're intending, so the spy-plane is as good at preventing attacks as an armed intervention. However, if you want to use it for surveillance against people who might have a legitimate complaint against being watched - for instance your own citizens, then yes, having the
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Ask yourself: why care of the targets know they're being watched?
Firstly, when the enemy knows that you're watching, he can attempt to deceive you.
Secondly, if the enemy can reliably know when he is being watched, then he can also reliably know when he is not being watched and is thus free to do whatever he wants.
Liquid able to absorb and transport hydrogen (Score:1)
Ion Tiger? (Score:1)