martinairyyz
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Would It Be Possible To Make A Solar Or Other....

Sun Oct 03, 2004 11:00 pm

I was wondering if a Solar-Powered or other such energy-using plane could be made. Since oil is getting scarce and it will run out in around 50 years this would win one aircraft manufacturer the whole pot of gold!
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pilotpip
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RE: Would It Be Possible To Make A Solar Or Other....

Mon Oct 04, 2004 12:27 am

DMI
 
OPNLguy
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RE: Would It Be Possible To Make A Solar Or Other....

Mon Oct 04, 2004 1:26 am

Although the above solar-powered aircraft did indeed fly, getting solar-powered commercial/transport aircraft developed/deployed has a few more technical challenges involved. I hope they won't take 50 years to resolve, but I see two key issues.

1/ Given existing solar-generating capability, there's not much room for payloads, certainly not enough to make it commercially viable today. Over time, the efficiency of the solar stuff will hopefully improve to help make that possible.

2/ To obtain any kind of operational capability that will allow a solar-powered aircraft to replace a fuel-burning one, you'll need to be able to fly in cloudy weather and at night, and at long flight durations. Batteries with which to store the solar-generated power would seem to be the simple answer, but the weight of today's batteries would negate the aircraft's payload-carrying ability, and probably wouldn't allow the aircraft off the ground in the first place. Maybe some radical new low-weight battery (or other storage technology) will come down the pike someday...

While it's true that the high cost of fuel is hurting all airlines today, something that could help the industry pretty quickly would be relief from some governmental taxes/fees, and in particular, the government being responsible for security (as a part of National Security).
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oly720man
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RE: Would It Be Possible To Make A Solar Or Other.

Mon Oct 04, 2004 9:46 pm

Solar panels have a very low energy efficiency,typically 2%. I doubt if it would be possible to get a lot better than this. The physics of photons knocking electrons into different energy levels is what limits it all I'd guess. Given the relative sizes of photons and electrons the process is a bit like throwing a ball in the sea and hoping to hit a fish.

The best hope for the future of aviation is hydrogen. There's a lot of water on the planet and electrolysing it to H2 and O2 is probably most cost effective.
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MD11Engineer
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RE: Would It Be Possible To Make A Solar Or Other....

Mon Oct 04, 2004 11:53 pm

I think the indiect use of solar energy through hydrogen is the way to go (I expect to be working on hydrogene powered aircraft within the next 10-20 years). It would also mean a new source of revenue for oil countries like Saudi Arabia after the oil wells dry up. They have a lot of sun, empty desert spaces and the transport of LH2 can be handled using LNG tankers.

Jan
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prebennorholm
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RE: Would It Be Possible To Make A Solar Or Other....

Tue Oct 05, 2004 7:34 am

Just some rough figures:

Getting a loaded B747 off the runway takes power in the region of 300 Mw.

The unobstructed sun delivers roughly one kw per square foot.

Consequently, a solar powered B747 would need 300,000 sq.ft solar panels with 100% efficiency. That could be a wing covered with solar panels with a 1000 feet wing span and 300 feet cord. That's about a handful of soccer fields.

Now the very best (and most expensive) satellite grade solar panels have a roughly 15% efficiency. So that wing suddenly got seven times larger. (30-40 soccer fields).

We have to take off at Equator at noon without a cloud in the sky, or we need a larger wing.

We have not yet estimated the weight of four 75 Mw electric motors to run the fans. All we know is that the very largest 5 Mw electric motors on train locomotives make the train tracks buckle. But with some new and sophisticated cooling they can probably be made 20-30% lighter at a skyrocketting price increase.

There was a solar eclipse and a hundred airliners ditched in the ocean... Ha-ha-ha.

Now about batteries:

An ordinary battery for a midsize car is some 25 lbs and can deliver roughtly 3 kw for 45 seconds - the time it takes to bring a B747 from brake release to VR speed.

300 Mw is 100,000 more meaning 100,000 times 25 lbs = 2.5 million lbs of battery. That's twice the MTOW of an A380. And remember, we just got the B747 one inch off the ground, and it is already going to land again.

Solar power and batteries have to improve efficiency a hundred to a thousand times to become viable for transport aircrafts. And then we haven't talked about prices yet.

When talking about chemical power, not nuclear power, then the absolutely three most powerful elements are C (carbon), H (hydrogen) and O (oxygen), Oxygen is 21% of our atmosphere. Jet fuel is the very best combination of carbon and hydrogen. The Wright Brothers showed us how to utilize these three elements to power flight, and no chemical law has changed since their days.

So I guess that we are stuck with them for the foreseeable future. Good for me since - yes, you guessed it - I'm working in the oil business. But yes, we also produce solar panels.
Always keep your number of landings equal to your number of take-offs
 
bhill
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RE: Would It Be Possible To Make A Solar Or Other....

Tue Oct 05, 2004 8:23 am

Instead of the hydrocarbons being dumped into the upper atmosphere, I think the "very best" would be Hydrogen and Oxygen..the exhaust would be used to cool the engines or served to the pax..or used to flush the toilets!!!

Cheers,

bhill
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L-188
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RE: Would It Be Possible To Make A Solar Or Other....

Tue Oct 05, 2004 9:05 am

Well I don't see solar cells running a commerical airliner, but with some of the new stuff comming out could we possibly see airliners using them to power their electronics and environmental systems? That would mean less power would be robbed from the aircraft to run the systems and I would think that a solar cell would be more efficent at altitude.
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videns
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RE: Would It Be Possible To Make A Solar Or Other....

Tue Oct 05, 2004 2:36 pm

I'm surprised that no one metioned that NASA's experimental aircraft actually ended up crashing...
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prebennorholm
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RE: Would It Be Possible To Make A Solar Or Other....

Wed Oct 06, 2004 4:07 am

Good point L-188.

But I'm not sure that it will work out that way since solar cells are not weightless.

Spending fuel on hauling around solar cells which produce little energy - maybe a difficult balance. Well, when it's dark the math involved is quite easy.

Solar cells do produce more energy at higher altitude. The McCurdy solar powered plane, which crossed the Channel back in the 80'es, did climb better and better the higher it went. The solar rays are stronger on mauntain tops where they have passed a smaller fraction of the atmosphere. At the altitudes in question we are talking about some 20% increase compared to an absolutely haze free ground level at sea level altitude.
Always keep your number of landings equal to your number of take-offs
 
L-188
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RE: Would It Be Possible To Make A Solar Or Other....

Wed Oct 06, 2004 8:42 am

Right now I don't think you can do it, but the technology is getting better all of the time.

An presumably you wouldn't be carrying paint under those cells.
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lehpron
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RE: Would It Be Possible To Make A Solar Or Other....

Wed Oct 06, 2004 9:12 am

Solar airplanes have been done, if you mean a viable application, there are many.

An airliner like others have stated is a bit off. a UAV would be a better option, they're smaller and lighter anyway. That would be my guess at first use for solar electric airplane in commercial production: as a military spy drone.

The whole project has to be designed properly, it surprises me that no one has touched on that, aside from efficiency, which isn't the only issue. A solar electric drone could loiter for months near a target region and be much cheaper than a satellite. The concept/prototype design would have to be approached as a server, or some computer system that remains "always on".

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