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Fuel Cells For UAV Drones

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Patrick

Thu Oct 25 2012, 03:48AM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

Im frustrated with flights of 8 minutes, then 47 minute charge times on expensive LiPo's. Im thinking i need a game changing innovation, that will give my drones capabilities that lipos just cant match.

there have been many manned and unmanned attempts to fly with fuel cells and even manned battery powered aircraft. but so far i only see the crap PEM type fuel cells being used.

heres what id like comments from here on the forum about...

what about solid oxide fuels cells? they suffer only the high heat disadvantage... and the associated 800 degree C insulation. theyer cheaper and dont use platinum and orgainc polymers, which are vulnerable to water flooding/drying out or carbon monoxide poisioning like the crap PEM cells... the solid oxide fuel cells, if small enough, might allow 1 or 2 oz fuel tanks (alcohol or kerosene) to yield 30-40 minute flight times... on a defensive note to skeptics, over the past 15 years SOFCs have come down in operating temp, shortend their start pre-heat time and are cheaper and easier to make.

other opinions? better suggestions for my energy needs? Any important factors i left out?

...

Thu Oct 25 2012, 03:57AM

Registered Member #56 Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445

One thing worth mentioning is that many modern LiPo cells can be charged at 3C, giving a ~20 minute charge time to 80% capacity.

Per the fuel cell argument, it seems like you would be way better off putting in a small gas/nitro engine, if there is significant electrical load you could even add a generator.

A fuel cell would be cool if you can find one with the power density you need, I am skeptical as to how far you will get though (then again I am a laser scientist and don't know much about fuel cells..)

Steve Conner

Thu Oct 25 2012, 06:57AM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

I agree, switch to gas engines

Ash Small

Thu Oct 25 2012, 11:24AM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

Whether you decide to use conventional motors or fuel cells, both of which require a liquid fuel, in your application you'll need to have well baffled fuel tanks in order to prevent the fuel 'sloshing' about, and upsetting stability.

BigBad

Thu Oct 25 2012, 04:00PM

Registered Member #2529 Joined: Thu Dec 10 2009, 02:43AM
Location:
Posts: 600

Hydrogen gas fuel cell? That way the fuel has negative weight. You end up with a blimp I suppose, but they do have good hang time.

Maybe try to design your vehicle to fly better; gliders have a much better L/D and can fly proportionately longer. Probably that means a higher Reynold's number though, which probably means a bigger vehicle.

Solar can work, but only if you have a very aerodynamically efficient vehicle.

BigBad

Thu Oct 25 2012, 05:09PM

Registered Member #2529 Joined: Thu Dec 10 2009, 02:43AM
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Beam power is another option, lasers or microwaves; even bright lights would work.

Proud Mary

Thu Oct 25 2012, 05:42PM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

How about an airframe skin formed from multi-layer organic dye-sentized photocells printed onto textile or paper?

Pinky's Brain

Thu Oct 25 2012, 06:54PM

Registered Member #2901 Joined: Thu Jun 03 2010, 01:25PM
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I presume this is for the quadcopter, gliders don't run dry in 9 minutes.

I wonder how efficient small pulse jet engines are, there is no rotating mass so you can presumably get the same quick power regulation as you get with electrical engines necessary for a quadcopter.

BigBad

Thu Oct 25 2012, 07:28PM

Registered Member #2529 Joined: Thu Dec 10 2009, 02:43AM
Location:
Posts: 600

For a quadcopter making the blades longer would greatly improve efficiency.

For hovering or going slowly, jet engines suck balls wrt efficiency. For long flights, everything else being equal, you want to throw a large amount of air down slowly (which is what big long wings do), rather than a small amount of air down fast (which is what jet engines do).

It's because energy goes as 1/2 m v^2, whereas the thrust goes as mv, where m is the mass, and v is the downwash speed; so if you work it you want m as big as possible and v as low as possible, so that mv = vehicle weight

Ash Small

Thu Oct 25 2012, 07:41PM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

BigBad wrote ...

Hydrogen gas fuel cell? That way the fuel has negative weight.

Not if it is compressed, which would be the only sensible thing to do. Weight would then be comparable (similar) to other fuels of the same calorific value.

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