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.'"
Re:Huh? (Score:4, Insightful)
Oh, I'm sorry -- point to me where they had a wingspan restriction in their unconditional statement.
Re:Huh? (Score:3, Insightful)
"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 regard), but they have more energy storage capacity than li-ion. And more importantly, they don't throw away the overwhelming majority of their collected energy.
Great place for a fuel cell (Score:4, Insightful)
Re:Green don't matter (Score:3, Insightful)
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
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.
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.
Re:Green don't matter (Score:2, Insightful)
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.
Re:Huh? (Score:3, Insightful)
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.