Solar Planes Aren't the Green Future Of Air Travel (vox.com) 286
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."
Still (Score:5, Interesting)
Having a solar driven plane circle the world is still cool.
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The problem is people are always thinking progress need to equate to a practical consumer level solution.
Many times the process of doing it just because you can, comes up with many side effect results.
I am wondering if the lessons learned to make an airplane fly around the world with solar, can have factors brought to the next generation fuel planes that are more efficient.
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The problem is people are always thinking progress need to equate to a practical consumer level solution.
Seriously, what a strange summary. "This technology demonstrator that is capable of flying around the planet using only solar power cannot replace a Boeing 747 with today's technology." Yeah, no kidding. Why did someone spend the time to write this? Is this an article paid for by Exxon-Mobile or something?
Re:Still (Score:5, Informative)
A solar-powered direct replacement for something like a Boeing 747 is impossible, period. Incremental technological development cannot get us from here to there.
Boeing 747-8I maximum fuel = [240 kL]
Energy density of Kerosene = [37 MJ / L]
Thermal efficiency of a modern turbofan engine = [40+%]
Flight duration = [16+ hours]
Energy required = ([240 kL] * [37 MJ / L] * [40%]) / [16 h] = [220 GJ/h] = [62 MW]
So, even a hypothetical 100% efficient solar-powered 747-8I replacement would require about 62MW of average (not peak!) power to operate. The maximum power that can be collected by a solar energy system (no matter how efficient) is limited by its surface area: it cannot gather more energy than what is present in the sunlight hitting it.
Maximum solar irradiance at Earth's Orbit: [less than 1.4 kW/m^2]
Upper surface area of a Boeing 747-8I: [less than 1000 m^2]
Maximum solar power available to a solar 747-sized object: [less than 1.4 kW/m^2] * [less than 1000 m^2] = [less than 1.4 MW]
Even an ultra-high-tech solar 747-8I replacement could not possibly generate more than about 2% of the power required to perform the same mission. It would inevitably need to fly much slower and lower (probably low enough for cloud shadowing to cause major problems), and/or carry a far smaller payload.
Barring a major (read: not foreseeable) physics or engineering breakthrough, true solar-powered jet replacements are not possible. Electric planes might happen eventually, but they will require refuelling or recharging on the ground, just like today's hydrocarbon-powered designs.
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Yes and no. Your math looks OK. However, I think a lighter than air craft with solar power might work out as a cargo carrier and possibly even as passenger vehicle. The Graf Zeppelin did a round the world trip sometime back around 1930. It took them something like a week and a half. They didn't use a lot of power and I'd expect that a modern design might be a bit faster. I think the zeppelins maxed out around 100kph (60mph in American).
I can't see them replacing jets at current fuel prices, but who k
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A battery-powered direct replacement, however, is possible. It simply requires a battery chemistry that can match jet fuel for energy density. There's nothing impossible in that; your own cells accumulate electric charge as an intermediate step in the process of "burning" your food, and plant cells can run the process in reverse (photosynthesis).
Or
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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 emergenc
Re:Still (Score:4, Insightful)
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.
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Likewise, solar planes will likely not replace a 747, but they may replace balloons and satellites (which are extremely expensive).
Just because something isn't a perfect replacement for an existing piece of technology, doesn't make the development pointless.
Also, a solar plane would not need to be able to fly at night or around the world to be useful. A solar plane that could take off and land in fair weather without using fuel would still be useful. It would still likely need a small battery for emergency landing but not for 8+ hours of flying at night.
Green can include jets and internal combustion ... (Score:4, Insightful)
... 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.
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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.
Technically, we only need 1960's "let's make it nuclear" optimism [wikipedia.org] and it doesn't even need to be electric. That thing is that's so awesome it needs a use. Maybe a supersonic atmospheric flyer on Jupiter for planetary research?
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Exactly. Look at the Apollo moon landings. We haven't made traveling to the moon a reality for consumers, and we basically did it just because we could. But in the process, we came up with all kinds of spin-off technologies that were a huge boost to the economy.
The lessons learned in flying a solar airplane around the world might not just help with other aircraft, they could have benefits for many other not-that-related industries as well. The Apollo program provided a big boost to the electronics indus
Re:Still (Score:5, Insightful)
Limitless in-theater dwell time, controllable deployability (at 43mph). If the military isn't already all over this, something is horribly out of whack.
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Hmmmm. And only five centuries after Magellan circled the world powered only by wind.
Making progress by leaps and bounds.
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The key word is plane here.
Battery weight (Score:5, Interesting)
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."
This isn't even the whole story. As a plane flies, it burns fuel, essentially throwing mass out the engines for thrust. Getting lighter allows the plane to climb to a higher altitude where it is more efficient.
Re:Battery weight (Score:5, Insightful)
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.
Re: Battery weight (Score:5, Informative)
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Re: Battery weight (Score:5, Informative)
On a non emergency, such as a mild tail strike on takeoff, where the plane appears safe but they would not risk a transatlantic crossing, they'll fly around in small circles for a few hours with full flaps, full airbrakes and high thrust to burn off the fuel as fast as possible in order to safely land at the same airport. Dumping fuel is messy, dangerous and nasty, so it's only done in a real emergency.
Re: Battery weight (Score:5, Informative)
http://www.usatoday.com/story/travel/columnist/cox/2014/07/13/fuel-dumping-emergency-landings/12530075/
"It all comes down to the fact that certain planes are designed to be significantly lighter when landing than when taking off -- in some cases more than 200,000 pounds (90,909.1 kilograms) lighter [source: Boeing]. This may sound backwards; one might think that taking off at a heavy weight would necessarily be harder than landing with that same weight. But landing can put more stress on a plane. When a plane lands heavy, it's very easy to hit the ground too hard and cause damage to the aircraft."
http://science.howstuffworks.com/transport/flight/modern/planes-dump-fuel-before-landing.htm
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Yes, perhaps I should not have written "safely". They might return with all hands safe and sound, but the aircraft may be damaged.
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I was on a 737 leaving Baltimore for the West Coast (Southwest Airlines). We took off and were starting ascent when the pilot came on and said "there's a red light on in the cockpit that shouldn't be on so we'll have to go back".
We immediately turned and landed... probably less than 10 minutes in the air. We were greeted by fire engines which the pilot said were "a precaution" and we stopped away from the terminal for an inspection. We had to wait for them to find another plane to continue our trip which to
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One example: https://en.wikipedia.org/wiki/... [wikipedia.org]. There is about a 230,000 pound difference in takeoff weight and landing weight. Aircraft of this sort would have some means of dumping fuel if necessary, there are FAA regs covering this case. Of course, in the case of a true emergency, you do what you need to do to get the plane on the ground.
As a (student) pilot, I'm immensely interested in alternative power plants for aircraft. AvGas is not cheap. Solar may not get you 100% of the way there, especially for
Re: Battery weight (Score:3, Funny)
As a (student) pilot, I'm immensely interested in alternative power plants for aircraft.
I don't mean to rain on your parade but you probably ought to know: while pilots may be interested in solar- powered aircraft, physics majors are likely to be less so.
Huge potential for cost advantage, plausible (Score:2)
The wall street journal estimates that for a 100 seat airliner, 30% of the cost of a flight is fuel. And another 14% is govt fees and taxes. Thus if batteries let you get cheaper fuel, don't know if thats true, then there's a large margin for cost savings. And if the gov't were willing to kick back taxes for not polluting the upper atmosphere. Then there's an even greater margin. So there's a powerful incentive to come up with electric power aviation if the total cost of ownership for electric power can
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Obviously I ignored that takeoffs use a lot of fuel. But that's factors of 2 and I was just roughing it out to orders of magnitude.
Re:Battery weight (Score:5, Funny)
planes only fly at certain heights
Really? I'm sure I've seen them go up and down. Wouldn't they have to put on all the airports on mountains otherwise?
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Or next to a mountain, and launch the aircraft with a giant railgun catapult anchored to the base and the top of the mountain.
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The altitude for flying is fixed. Meaning planes only fly at certain heights.
For the most part, you have 'lanes', and most planes fly a set route at a set altitude, but this is more a traffic control measure and that they've worked out that that route is the most efficient, on average.
I've been on flights where the pilot varied his altitude by more than 5k feet in order to get a more favorable wind or to avoid weather.
Sail ships (Score:2)
May as well go back to sail ships [thepeoplescube.com]... Maybe, not as fast, but certainly much more capable.
The Future? (Score:2)
Re:The Future? (Score:4, Insightful)
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
Efficiency (Score:5, Insightful)
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?
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Critical thinking (Score:3)
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?
Regarding critical thinking, why couldn't we just use solar panels on the ground to make jet fuel(*)?
Jet fuel in this instance is just an energy carrier, and has a much higher energy density than lithium. While Lithium batteries may be appropriate in some cases (portable devices, ground transportation), for air flight it's more appropriate to use something else.
(*) Or perhaps a biological method such as GM modified algae or a bio-yielding plant. The Wikipedia page [wikipedia.org] of crop yields indicates that Algae can yie
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I doubt your 3 ha figure, but let's run with it just for fun.
And how many hectares of algae ponds would it take to supply one tank of fuel several times a day for each of thousands of 747-equivalents? Several MILLION hectares? That's several tens of billions of square metres, or several tens of thousands of square km. How about the colossal energy input you would ne
Offsetting? (Score:3)
I think it's pretty apparent that the solar concepts are just concepts. Obviously there's not enough energy output to replace passenger flight.
But the question is, can solar panels on a plane offset the energy consumption enough to make a difference? That's probably also a no, but that's where the question should start.
Keep in mind, some cargo ships have been experimenting with massive kites/sails that help offset the energy needed for their engines:
http://www.skysails.info/english/skysails-marine/skysails-propulsion-for-cargo-ships/
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>But the question is, can solar panels on a plane offset the energy consumption enough to make a difference? That's probably also a no, but that's where the question should start.
There's just not enough energy in sunlight per square foot to make it worth it. You put all you effort into creating a huge receptor area and keeping weight down that the other needs become impracticable (comfort, speed, luggage, etc). Storage density and associated weight are the things that matter. If we have a very big leap in storage capability, then short hop flights with small planes might become practical. Until then, we might see some recreational crafts that get used for a very short duration thril
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400 m^2 of sails might help more. There are a few sails on cargo ships [theloadstar.co.uk] out there as experiments. The fuel cost savings seems pretty good. Combining the two might be interesting.
Batteries (Score:2)
Not sure if solar panels on the airplane make sense tho
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Flying a battery with that kind of energy density is one of the stupidest conceivable things you could do. At 30x density, a cell phone battery holds the energy of 0.28 pounds of TNT or 0.54 sticks of dynamite. They blow up now when smacked with a hammer; imagine the tiny, tiny fault required to cause a chain reaction and the size and sheer reaction time of the explosion: it would detonate immediately. Now you want a plane loaded with that shit?
Just use solar power or some other source to convert atmo
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Perhaps a different design--like a Flying Wing [wikipedia.org]--might give more aerodynamic area and other options.
module efficiency (Score:3)
> 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 [...]
Besides that, I strongly suspect there isn't enough power in the form of sunlight falling on a surface the size of a 747's wings to achieve the objective. In other words, it's not just a matter of solar panel efficiency, it's also a matter of total energy available for capture.
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Re:module efficiency (Score:5, Informative)
Exactly. I ran some back-of-the-envelope calculations on this 3.5 years ago in another Slashdot thread. https://slashdot.org/comments.... [slashdot.org]
And because we're presumably too lazy to click that link, I'll paste it below for your reading pleasure...
This is why: http://what-if.xkcd.com/17/ [xkcd.com] [xkcd.com]
There simply isn't enough solar power delivered to the surface of the aircraft, even at 100% conversion efficiency, to move people and luggage using only available sunlight.
Google tells me direct illumination to a surface perpendicular to incoming full intensity sunlight is about 1.4 kW per square meter. Google also tells me that the wing surface area of a 747 is around 5500 square feet. Only half of the 747 wing is directly illuminated by sunlight at any given moment, but the surface of the fuselage could be covered with photocells as well, so 5500 square feet overall is probably a decent estimate for the directly illuminated surface area of the aircraft as a whole. And for hand-wavy purposes lets assume that the entire surface of the 747 is perpendicular to the incoming sunlight (i.e. a planar plane... pun totally intended). And that we have perfectly efficient photocells giving us 100% conversion efficiency. Running the math, this gives us around 715kW under bright direct sunlight, or about 959 horsepower -- the equivalent of 1.5 2012 Ford Shelby GT500's.
Each engine of a 747 generates around 15,000 horsepower at cruise, and around 30,000 at takeoff, and a 747 has four engines. So you need around 125 times the power generated by a perfectly efficient perfectly illuminated solar-powered 747 to get said plane off the ground, and around 65 times the power for cruising. And then you could only fly it in the middle of the day near the equator.
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Master of the understatement. At high noon, there is only a peak on the order of 1/100 of the required power impinging on the wings in the form of sunlight - in the DAYTIME. And zero power after the sun sets. The idea of solar powered jetliners is no more than fantasy for the feeble-minded.
Won't help (Score:2)
to increase efficiency of solar cells - Sun radiation is not increasing, pretty much constant, I would say. Probably need a football-field size surface constant to generate enough oompf to compare to kerosene-propelled turbines.
Generating fuel from solar/wind/water and propel airplane traffic will probably show the discrepancy between necessity and actual use - no one will even touch restricting air traffic, so....
Compared fuel efficiency/use per person from airplanes to cars, airplanes are winners, hands d
"because I can't imagine such a future" (Score:5, Insightful)
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?
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It's not that no one can imagine such a future -- a little digging into science fiction stories should turn up a variety of examples of battery- or solar-powered air vehicles. One that I can think of is Robert Heinlein's novel Friday, with vehicles powered by Shipstones, an energy-storage device. What causes battery- or solar-powered air vehicles to be dismissed is an awareness of the energy density limitations of current generation and storage systems, and the progress of improvement in these systems; eith
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Yeah, and those people who say perpetual motion machines will never work and that we can't make a transistor out of something smaller than a single atom... we'll show them.
Computers in every house were solved through steady miniaturisation and were far from being impossible as defined by laws of physics.
By comparison here we're talking about a situation where a theoretically perfect solar energy source driving theoretically perfect engines on a theoretically perfect wing still won't have the ability to do e
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Er, okay (Score:4, Insightful)
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.
beam power by microwave? (Score:2)
I wonder if there's any potential to beam power to a plane by microwave, either from a satellite or from a network of ground stations?
(I'd read a proposal to do space ship launches this way, to save on fuel weight.)
Gee, patronize much? (Score:5, Insightful)
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.
Re:Gee, patronize much? (Score:5, Funny)
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.
Have you looked at some of the comments here?
Aw, C'mon... (Score:2)
... In order to make commercial solar, one has to abandon the wing, not solar power per se. Imagine a blimp whose entire bag is made up of ultrathin solar cells. Now lift is "free" -- all one needs is enough power to run a pusher that can exceed the drag force of the prevailing wind, and surface (of the blimp) to volume works in your favor, as increasing the surface area increases net buoyancy and hence the total weight of storage batteries one can lift. The Chinese are building a prototype already, as a
launch catapult (Score:2)
There are lots of small savings to be made
For a short commuter flight, say between LA and SFO. the speed of the plane is just one consideration, there are lots of on-the-ground delays that add to the total travel time
Here's my plan...
Step 1 - abolish the TSA, they're worthless and that saves an hour off the trip for a start
Prior to flight, batteries loaded, fully charged, into plane on the runway. The batteries here have a different function, they are a power boost for a daylight flight not a reserve for o
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Still way off, sure, but the future sometime
Batteries need similar engines for thrust (Score:5, Informative)
Batteries, or solar cells, don't make thrust by themselves either. You'd still need the same turbofans, just with heavy electrical windings in the middle rather hollow combustion cavities. Electric motors tend to be quite a bit heavier than empty cavities are, so I'd expect the electric engine to be probably a bit heavier.
You could put a prop on an electric motor. That limits maximum speed, and still electric motors are heavy.
> The fuel system itself
Such as the fuel lines and fittings , the hollow copper tubes? Compare with the copper required to carry thousands of amps safely, with heavy-duty insulation. The fuel line and fittings are probably lighter than electrical lines and fittings capable of transmitting the same amount of power.
> If wing didn't have to carry fuel could it be more efficient?
Wing efficiency is determined by shape and surface smoothness. What's inside doesn't matter, except a snall effectbthat carrying load in the wing is slightly more efficient than carrying the same load inside the fuselage, by eliminating the bending moment on the wing root. Putting solar panels on the SURFACE of the wing, where it's right in the critical boundary layer airstream , is a much bigger design constraint than putting something IN the wing.
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I was also curious and looked up what a Tesla weighs - at 2100kg it weighs more than the equivalent gas car (E-class mercedes) and ~63% of the weight is batteries and motors. So we have an example of a ground up gas to electric design and it doesn't come out ahead on weight.
Re: Batteries need similar engines for thrust (Score:3)
at 2100kg it weighs more than the equivalent gas car (E-class mercedes)
I wasn't aware there was anybody who considered the Model S and the E-class Benz to be equivalent. In what way??
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There are plenty of advances and savings with not having a fuel system, starter system, throttle, ballast pumping system and all the rest that a dirty fuel burning plane needs, but all of them will never EVER equal the displacement in power-to-weight ratio that a hydrocarbon plane has over solar, for one simple reason:
The sun is just not bright enough from Earth
Even if we did manage to make solar cells 100% efficient, they just won't capture enough light
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You would need these batteries to charge very fast while on the ground, have long life-spans and cycle-count ratings for it to be economically worth it.
No, you don't need fast charging rates. With an airport, you have dedicated ground crews handling the preparation of the planes between flights, employed by the airline. So instead of refueling the plane, they just need to swap out some battery packs while the people are unloading. It should be entirely possible to build a fast-swap battery module into th
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That's not really what electric aircraft are about. There are basically two types.
You have light weight solar powered aircraft that can stay up indefinitely. The benefits are obvious.
The other type is the commercial passenger/cargo aircraft. It will still need liquid fuel, but can cut emissions around the airport by using battery power when taking off and landing. Take off in particular needs very high thrust, and thus very high emissions.
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I believe I read recently that someone was working on a "hybrid" airplane which would use battery power for takeoff and on the ground maneuvering which would help with emissions and efficiency. (I believe the article may have even made it to /. where it was trashed, of course.)
Here's one hybrid almost ready to fly. It has a 300 mile battery range and a small motor for 1000 mile range.
http://voltavolare.com/ [voltavolare.com]
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Thanks, interesting link.
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That's a pretty good point: why don't they use catapults for airports? Probably inertia at this point: it'd require all the airports to install them, all the airplanes to be redesigned for them, all the pilots to be retrained for them, etc.
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Wrong.
Most of the energy in a gallon of jet fuel is wasted as heat. You're correct about planes losing mass as they fly, but the inefficiency of turbine engines and of anything Carnot-cycle-based probably more than makes up for that. Electric motors, OTOH, are well over 95% efficient, and there'd be more losses in the batteries themselves.
So yeah, we definitely need a significant increase in battery energy-density before electric planes become feasible, but not nearly as much as you claim. Probably more
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What could possibly go wrong?
Apart from one crashing that is.
At least the NB36 never crashed.
Yes I know the reactor never powered the plane.
Why not just keep using hydrocarbons? (Score:3)
"Hydrocarbon fuel" doesn't necessarily imply "fossil fuel," you know! Synthetic fuels and biofuels are easy sustainability solutions that even work with the infrastructure and aircraft we have now, without the physical impossibility of solar or the political impossibility of nuclear.
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Didn't Audi make a synthetic diesel that could be synthesized from CO2 (although to do so requires a good chunk of energy)?
Battery innovations are quite useful, but if we can pull a usable, energy-dense fuel from the air, this would help with sustainability. As an added bonus, it would be a carbon negative or at worst, carbon neutral.
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Right. Batteries are not the only way to generate fuel for a plane from solar power. In theory, if you were somehow able to pull carbon from the atmosphere and use that material to make hydrocarbon fuels, you'd at least have a nearly carbon neutral jet fuel, even if carbon was emitted at some point in the cycle. Obviously, this is not something we know how to do at the industrial levels required to support all air traffic, but if we're able to scale out current methods, or more likely, find a more effici
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Synthetic fuels and biofuels are easy sustainability solutions
If they were easy sustainability solutions, we'd be using them by now. But they're not:
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Synthetic fuels may be easy but fossil fuels are so cheap that they can't compete. A carbon tax would level the playing field.
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Synthetic fuels
As in "using energy to combine carbon monoxide and hydrogen"?
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I think it's more like this from Wikipedia https://en.wikipedia.org/wiki/... [wikipedia.org]
Biofuels processes
One example of a Biofuel-based synthetic fuel process is Hydrotreated Renewable Jet (HRJ) fuel. There are a number of variants of these processes under development, and the testing and certification process for HRJ aviation fuels is beginning.[35][36]
There are two such process under development by UOP. One using solid biomass feedstocks, and one using bio-oil and fats. The process using solid second-generation biom
Military biofuel jumpstarts biofuel infrastructure (Score:3)
Synthetic fuels may be easy but fossil fuels are so cheap that they can't compete. A carbon tax would level the playing field.
So would passing peak petroleum production, which we may have already done.
So would national security concerns about foreign petroleum supply lines. Note the military has had jets flying on biofuels since 2010. They can justify the higher cost with more secure supply lines. Satisfying the military's need for jet fuel, or a large part of it, can jump start the biofuel generation infrastructure and bring costs down.
Biofuel aircraft farther along than solar aircraft (Score:2)
Synthetic fuels and biofuels are easy sustainability solutions
If they were easy sustainability solutions, we'd be using them by now. But they're not:
Bio-fuel powered flight is far farther along than solar powered flight. The US Navy has had some F/A-18 Hornets flying on bio-fuel since 2010. Scaling up bio-fuel generation is quite a bit more practical/doable that batteries that have the energy density of jet fuel.
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Synthetic fuels and biofuels are easy sustainability solutions
If they were easy sustainability solutions, we'd be using them by now. But they're not
Bio-fuel powered flight
Biofuels are not the same as synthetic fuels.
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Elbonian Air?
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Elbonian Air?
More like "railgun airways".
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Elbonian Air?
More like "railgun airways".
Sounds like takeoffs could be rather unpleasant.
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People are a bit picky about planning travel in advance and getting places on-time.
There are usually thunderstorms daily in the USA, and buses, trains, cars and airplanes go right through that.
Zeppelins have to wait for the storm to pass.
Regardless of Hindenburg, their fate was already sealed.
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There are usually thunderstorms daily in the USA, and [...] airplanes go right through that.
You don't fly much, do you?
First, airports will close in bad weather. That means airplanes either have to wait for the airport to reopen or they will land elsewhere.
Second, airplanes will go around bad weather. This means that the flight might arrive late, which affects the flight after it, and so on and so forth. Airlines hate bad weather because it messes up their schedules.
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You don't fly much, do you?
Quite a bit, actually.
First, airports will close in bad weather. That means airplanes either have to wait for the airport to reopen or they will land elsewhere.
Airports closing in bad weather is rare for more than a few hours. We're usually talking about a single airport, and the delays are usually on the order of an hour or so. Sometimes 4-8 hours, but it's not that common.
However, a storm front moving across the plains would ground nearly every transcontinental zeppelin for a day or more.
Also, if we're just looking at airplanes, we're talking about around 500mph, not 80 mph. An airplane can suffer through a 2-hour delay and still beat the z
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We already have aircraft that can go 80MPH and take almost no fuel
Gliders (sailplanes) can hit about 170. Granted, then they occasionally need to slow down and fly around in circles in pockets of lift, but even their average speed is probably a lot faster than most people realize.
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I thought of that too -- lighter than air craft helps make solar power more practical by significantly reducing the energy required for lift.
But there's a catch-22 waiting for you there. The Hindenberg disaster was related to the use of hydrogen, which is easy to make but very volatile. Modern lighter than air craft use helium, which is not volatile at all, but extremely difficult to make. Once we use up the helium available to us on Earth, we're pretty much out. Kinda like fossil fuels.
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The Hindenburg was going to happen eventually. It was only a matter of time with hydrogen. More usage of Zeppelins would have just increased the probabilities.
Which is not to say it is impossible to make them much safer even with hydrogen, but I think the probability of an accident was always going to be high enough that its hard to imagine them having gotten far enough into the future for them to have been fully developed.
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Graf Zeppelin was 770 ft long, carried 40 crew and 20 passengers. (Note that an American football field is 300 ft from goal line to goal line.) Boeing 747-400 is 230 ft long, carries somewhere between 400 and 600 passengers.
That means that the ground facilities to handle the zeppelin are going to be a lot bigger and you're going to need a lot more of them, to handle the zeppelins.
You'd need 20 to 30 Graf Zeppelins to carry one 747 passenger load. Fly to Tokyo Narita, or Bangkok Suvarnabhumi, and look at
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Not really the point. The technology itself has limits that prevent it from scaling up to reasonable size. This is not a matter of figuring out how to make a better motor. The issue is the density (energy per weight) of the energy source itself. Surely this could be improved upon, but unlikely that sufficient gains could be made to power a passenger airplane.
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Yes, barring an absolute revolution in battery storage densities, we're not going to approach the energy density of hydrocarbon fuels even with sustained incremental advances.
That revolution may happen at some point in the future, but we may need to have a much better handle on physics to do it.
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Yep large aircraft will be the last type of vehicle to run on liquid hydrocarbon fuels. Land vehicles, small planes, and small boats can run on batteries. Large boats can run on a combination of nuclear, solar, and wind power (yes, as in bringing sails back, for certain values of "sails").
The best solution for large aircraft is biofuel.
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Yes, barring an absolute revolution in battery storage densities, we're not going to approach the energy density of hydrocarbon fuels even with sustained incremental advances.
That revolution may happen at some point in the future, but we may need to have a much better handle on physics to do it.
We already know how to store energy at the same density as hydrocarbons. They are called hydrocarbons. The most straightforward solution for a greatly improved battery might be to figure out how to create hydrocarbons on the fly. Likely won't help small portable devices but a plane is large enough that if you could generate hydrocarbons with 500 pounds worth of equipment, it would be worth it. The real problem is not the "battery" but rather that solar just doesn't create that much energy per square fo