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Solar Planes Aren't the Green Future Of Air Travel (vox.com)
An anonymous reader writes: By any standard, the Solar Impulse 2 is a marvel of engineering. This solar-powered plane didn't use a drop of kerosene on its epic trip across the Pacific Ocean. It's a real testament to how far solar technology has advanced. Unfortunately, for anyone hoping that we'll all be puttering around in solar planes soon -- well, that's pretty unlikely. From a Vox report, "Consider: The Solar Impulse 2 features 17,000 solar cells crammed onto its jumbo jet "size wings, along with four lithium-polymer batteries to store electricity for nighttime. Yet that's still only enough power to carry 2 tons of weight, including a single passenger, at a top speed of just 43 miles per hour. By contrast, a Boeing 747-400 running on jet fuel can transport some 400 people at a time, at top speeds of 570 miles per hour. Unless we see some truly shocking advances in module efficiency, it'll be impossible to cram enough solar panels onto a 747's wings to lift that much weight -- some 370 tons in all. Nor is it enough to load up on batteries charged by solar on the ground, since that would add even more weight to the plane, vastly increasing the energy needed for takeoff. A gallon of jet fuel packs about 15 to 30 times as much energy as a lithium-ion battery of similar weight. That fundamental difference in energy density is a big reason we're unlikely to see large commercial airliners powered by batteries fill the skies."
In addition, a plane would have to be made stronger to support landing at full-takeoff weight. Current planes cannot land safely when fully loaded with fuel.
W..w..W - Willy Waterloo washes Warren Wiggins who is washing Waldo Woo.
Unless we see some truly shocking advances in module efficiency
It wouldn't work with 100% efficiency, so why would increase in efficiency matter as far as making it practical? What is happening to critical thinking skills?
yeah, this whole airplane thing reminds me of that fool who thought people would have computers in their houses. pfft! how can you fit a giant electromechanical machine that fills a warehouse into your living room? some people, am i right?
Anons need not reply. Questions end with a question mark.
Solar Planes Aren't the Green Future Of Air Travel
I never thought they were. Jeez, why always looking for the negative?
Next: The LHC can't solve global warming.
systemd is Roko's Basilisk.
We also stalled out with SST. Why?
Efficiency. The gains from going 1,200 MPH instead of 600 MPH aren't worth the extra expense. Amdahl's Law -- though aimed at computing -- comes to mind
"I don't know, therefore Aliens" Wafflebox1
Limitless in-theater dwell time, controllable deployability (at 43mph). If the military isn't already all over this, something is horribly out of whack.
Exactly - it's how progress is done. The innovation isn't that it'll replace a 747 immediately, but with R&D, it might. Or it might fit itself in a new niche.
I mean, it's like saying airplanes are stupid when you see the Wright brother's 1903 example. The thing only flew a few meters. What, airplanes are completely pointless because anyone can walk farther than they can fly?
No, progress is made by refining the process. It flies a few meters first, then as you learn from it, you fly farther and farther until you can go halfway around the world.
Likewise, solar planes will likely not replace a 747, but they may replace balloons and satellites (which are extremely expensive).
There's a lot of research going on airships too - while not as fast as a plane, they have enormous cargo carrying capacity and can be launched inland, so if you have cargo that's not required to be there within a day, but can take a week or two, it's competitive with regular shipping (which usually takes a month), plus you don't need a port and trains/trucks to bring it inland.
Just because something isn't a perfect replacement for an existing piece of technology, doesn't make the development pointless.
To slashdot's new masters: your readers aren't so ignorant that we think that Solar Impulse 2 means we'll be seeing solar powered 747s. Sheesh.
Post may contain irony: discontinue use if experiencing mood swings, nausea or elevated blood pressure.
... progress is made by refining the process ...
Yes, and the bias against internal combustion and jets and the bias towards solar are causing people to miss a major piece of that process. The fuel. There is nothing wrong with internal combustion and jets, the problem is only their current petroleum based fuels. Switch to bio fuels that are carbon neutral and we have no problem. Carbon is not the problem if it is taken from and returned to the current environment, as with bio fuels. Carbon is only a problem when we mine ancient sequestered carbon and reintroduce it to the current environment, as with petroleum.
Liquid fuels have incredible energy density. We would probably need a Back-to-the-Future-like "Mr Fusion" reactor, not improved batteries, to make electrically powered fixed/rotary wing aircraft practical.
LZ-129 (airship Hindenburg) surface area: 27,299 square meters. If upper half is covered with solar panels there would be ~4MW of power if we use current off the shelf 30% efficient solar panels. That power is actually more than the four 16 cylinder Daimler Benz diesels provided for that airship.
However when flying over water the reflected sunlight would provide energy too. It would be probably wiser to wrap the entire airship with solar panels. Remove diesel engine weight three times (one left for emergency backup) and reduce fuel volume to one quarter of the original amount of diesel. It might actually work during daytime. However I don't have any idea would even the lightest thin film solar panels be light and strong enough to replace current materials used as outer shells. Then there is the night cruising issue, there should be batteries or some other energy source for that.
If I recall correctly there are some solar powered airship projects where U.S. military is seeking a "all seeing eye" functionality, unmanned high altitude airship where solar power is the primary source of energy. Maybe something interesting spawns from there.