UAVs Go Green With Fuel-Cell Powered "Ion Tiger"

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.'"

Comments

Huh?

[Rei]

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? It flew for 82 hours.

Re:Huh?

[Rei]

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% (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?

[mcrbids]

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.

Re:easy fix

[MoeDumb]

Honey, is that you posting? All right all right, I'll get off the computer and mow the lawn! Although I never thought you'd stoop so low to troll here just to get my attention.