Energy density of li-ion batteries is less than 1/50th that of jet fuel, and modern high-bypass turbofans are far more efficient at turning that energy into forward power than a gasoline engine is.
A Boeing 777-300ER carries 304,000lbs of fuel fully loaded. This contains just under 6 terajoules of energy.
The battery pack of a Tesla Model S is about 300 megajoules.
So you,d need 19,700 Tesla battery packs to power your 777-equivilant jetliner. Problem is they weight over 15 millions pounds.
True, but no one is claiming that technology will stand still. Heck, we've even played around with nuclear powered aircraft in the 50s [1]. And there is enough uranium to be mined to last us 80 or so thousand years.
People have often claimed that we will exhaust our resources at some future point, but these predictions have always excluded technology advancements that have always come before any resource crisis has occurred.
Nuclear powered aircraft have undesirable failure modes.
The best possible battery designs actually do approach the energy storage density of liquid hydrocarbons, nearly, and theoretically (metal-air batteries, specifically lithium-air).
The best currently practical battery designs are at least an order of magnitude less dense.
And as I note above and in my longer piece (linked above), the additional engineering constraints for electrically powered aircraft argue against their feasibility.
Synthetic fuels strike me as much, much, much more viable, though even there the economics of flight will change markedly. Probably acceptable for the military and VIPs, not so much for everyone else.
Nuclear powered aircraft have undesirable failure modes.
I may not be fair because it may not have been what you meant, but I need to address this.
It wouldn't be like a nuclear bomb going off. It wouldn't even be like a nuclear power station going into meltdown. The US purposefully made a nuclear rocket go through a worst-case scenario in the 60s and it didn't permanently irradiate the desert or anything.[1] It would kill people on the ground and you would need professional clean up, but that's also the case with normal plane crashes.
Scattering bits of hot reactor all over the landscape is bad enough.
Add to this the tendency for aircraft to crash in two general locations: at or near airports, which is to say, in the middle of a bunch of people and/or other stuff generally considered valuable and whose preferred state is non-irradiated, or way the hell in the middle of nowhere, which is inconvenient for all and sundry to access, including radioactive contamination mop-up mod squads.
Then there's the general halt-and-catch-fire problem which further compounds the general tears and frustrations concerned with dumping fissibles and decay products all over creation.
Normal plane crashes tend to kill the people who are loitering around the crash site while it's busy being a crash site. They don't go for the slow lingering kill, or just the damned uncertainty that accompanies known or, well, we're not sure, maybe, maybe not, radiation exposures. The acute nature of most chemical fuel incidents means that the risks, while not insignificant, tend to be effectively mitigated often in a matter of minutes to hours. Not years or centuries.
Shift from turbofan aircraft operating at Mach 0.9 to ducted-fan turboprops at perhaps mach 0.7 would reduce fuel consumed per-mile quite a bit.
Ducted fans and propjets have their own issues (primarily weird/obnoxious noise characteristics) but if fuel costs spike I suspect that will be dealt with.
Lots of things can be done. Will they, should they, and is there a percentage in it, are the relevant questions.
I'm not an aviation engineer. I'm aware that electrically powered turbines (ducted fans) are possible, and that they're used on some RC-controlled model aircraft (as well as actual fuel-fired gas turbines). My understanding is that they have much lower efficiency than props.
Given the already unfavorable energy, weight, and storage characteristics of aircraft, I'd think that efficiency would win over speed in most cases.
We of course never exhaust our resources, but resource depletion certainly changes the economics of things. In the 1980's, the talk in aerospace was about supersonic passenger flight. The rise in fuel prices totally killed that idea, and set the direction for the past three decades in the industry, research into more efficient subsonic turbofan powered aircraft.
Fuel was an issue, but only one. Other impacts, including the prospect of over-ground supersonic flight inflicting millions of people to multiple sonic booms daily was another.
Garrett Hardin (of "Tragedy of the Commons" fame) was one of the critics of SST, and I believe it was that which prompted him to note, effectively, that humans didn't simply have to follow the technological imperative: that because we could do something we had to do it.
I'm surprised that, post-Concorde the claim is that Concorde was actually making BA a profit. It had always been presented as a commercial failure to my recollection:
On average Concorde made and operating profit of £30-50 Million a year for British Airways in the boom years where many passengers were travelling first class. British Airways reportedly received £1.75 Billion in revenue for Concorde services against an operating cost of around £1 Billion. Air France made a much smaller profit.
It has a energy density slightly lower than Jet Fuel[1], and increasing supply (thanks to new techniques for extraction and some huge gas field finds) and stable cost in the US[2].
Tupolev is developing a LNG power plane, and claims it will cost 40% less than a conventionally fueled aircraft to operate[3].
LNG is still a fossil fuel. Its supply is inherently constrained. Most estimates are that we'll hit peak natural gas some time after peak oil and before peak coal -- somewhere in the mid-to-late 21st century. Jean Laherrere (who's also researched peak oil) suggests a 2030 date for peak NG.
One characteristic of gas that makes predictions more difficult than oil or coal is that wells tend to peak and fail very suddenly. Which makes sense: you're extracting a gas, not a fluid, under pressure. While oil can be extracted, effectively, by sucking harder, or by forcing water into wells (what Saudi Arabia's been doing for years now), gas flows until it doesn't. Experience to date with fracked natural gas suggests that wells peak even faster, often within a year.
As for NG as an aviation fuel: while it tends to perform well on a energy/weight basis, it's not so hot on energy/volume, and presents more significant storage and handling challenges. Where liquid fuels will stay in any reasonably contained tank, LNG needs either refrigeration or pressure to be viable. I'm not saying it's impossible but I'd strongly suspect it's much less practical than liquid fuels, so long as they're available.
That Russian NG aircraft has been under development for four decades and still isn't available. I take any paper-engineering estimates with several tons of salt. Of the touted benefit, carbon monoxide emissions reduction really isn't an issue: CO is a problem in confined environments such as garages and warehouses, in which commercial aircraft rarely operate. In the open atmosphere, CO both dissipates and reacts fairly quickly (forming CO2). Of itself it's not a long-term persistent atmospheric pollutant.
Similarly, NOx and hydrocarbon emissions are results of incomplete combustion and principally represent problems in urban smog where you've got large numbers of vehicles operating in a constrained area. They're not a particular concern in the wide-open reaches most flights occupy most of the time.
Oh, I agree that LNG is resource constrained (of course!)
The interesting thing is that the impact of peak LNG is difficult to model. For example, most of the modeling for peak oil didn't anticipate the rapid shift to LNG use, which has moderated the price impact on oil.
I find any predictions of peak gas made prior to 2009 extremely suspect, as they don't take account of extraction from shale oil fields. See, for example the predicted production graph on [1], which predicts increases in US production out to 2040. I find that graph reasonably defensible, and it doesn't take into account non-US sources (eg Qatar, Brazil & Australia all have huge gas fields).
I don't disagree with the concern about peak oil and peak gas. I just find it extremely difficult to predict what it means - especially since the technologies associated with the gas industry are rapidly changing.
On the price of oil: for a long time, and certainly when I was studying economics back when dinosaurs still roamed the Earth in the late 1980s, the line was that as resources became scarcer, market prices would increase. Julian Simon certainly argued for this. But then, he's an idiot (well, now a dead idiot).
A more interesting and accurate view is argued by Gail Tverberg of "Our Finite World" blog (also "Gail the Actuary" at The Oil Drum): oil prices are constrained between the minimum supply cost imposed by extraction costs, and the maximum demand price based on use value. There are a number of analysts who've cited a price ceiling between around $80 and $115 (my money's on the higher end), over which, if prices rise (because of extraction costs), the global economy tanks.
Another way of looking at this is by considering the productivity of energy on a $GDP/barrel basis -- you can compute this by taking national oil consumption and dividing by GDP -- Wolfram+Alpha allows this easily. The present world price is around $110/bbl and has been reasonably stable there for the past few years. In the US, that barrel produces around $1000 of GDP (though there's a fair argument that this is the result of outsourcing more energy-intensive activity). For China and India the number's closer to $450 - $500/bbl.
Which means that between the oil cost of $110 and the economic value of $450 is all the value that India can access from that oil.
They might be able to increase this through efficiency improvements, but practically, increasing the price of oil means foregoing the previously economically viable activities which produced a low but positive benefit. Or, in other words, raising the cost of energy is an inevitable damper on economic output.
Yes, fracking's seen a transfer of energy use from both coal and oil to natural gas, where such substitution's been possible, but NG supplies are distinctly limited, and I've posted the total reserve exhaustion dates based on present consumption, growth trends (which "years of supply" arguments always leave out), and proven reserves. The dates aren't far off (I can't see my post from this page, but it was ~2030 - 2050 as I recall based on 2.7% to 2.2% growth -- not all that distant). And we don't have an option beyond gas (other than coal, which is suicide from a climate perspective) that we can simply dig out of the ground.
I find any predictions of peak gas made prior to 2009 extremely suspect, as they don't take account of extraction from shale oil fields.
Fracking doesn't produce new gas finds, it increases what can be extracted from known ones. As with peak oil, the story with peak gas is that the biggest discoveries are behind us: about 40 years ago during the 1970s. Fracking is only increasing the rate at which we're extracting a nonrenewable and finite resource.
Richard Heinberg and Gail Tverberg are two sources I'd strongly recommend for more on what the actual dynamics are.
http://www.postcarbon.org/ Heinberg's published numerous books, The End of Growth covers much of the economic impact, Snake Oil addresses oil and fracking specifically.
We have about 60 years of proven NG reserves at today's current consumption levels. There is probably a lot more than that waiting to be discovered.
The problem with alternative fuels for aircraft is that jet fuel is still so darn cheap and there is no crisis right now. So none of these are economically viable...yet.
Note that "peak in 2030" and "60 years proven reserves" aren't incompatible statements. The problem is that post-peak, it gets a lot more expensive (in terms of energy cost) to extract.
There's also the rate of consumption growth to take into account -- find an annual rate, apply the rule of 72, and realize that in the last period you're using as much as you have in all the previous ones, combined.
And no, there's probably not a whole lot more waiting to be discovered ... at least not anywhere that's readily accessible. Prospecting for mineral resources has been pretty bloody extensive, the types of formations in which natural gas is found are well understood, and any of those which are accessible have been accessed.
What remains is going to be what's difficult to get to, or difficult to get to market (natural gas doesn't ship well in barrels -- it's got to be compressed, liquified, or piped).
Yeah, maybe there's untapped reserves in Antarctica or Greenland, but by the time we're going after that, we'll have a few other concerns at hand.
So let's look at that. Wikipedia's statement expands on the cited reference by specifying constant consumption, but let's accept that as standard practice in energy reserve estimate statements:
Dr. Anthony Hayward CCMI, chief executive of BP stated in October 2009 that proven natural gas reserves around the world have risen to 1.2 trillion barrels (190 km3) of oil equivalent, enough for 60 years' supply if consumption is non-increasing, and that gas reserves are trending upward.
A quick check turns up a Motley Fool piece stating that global NG consumption is growing at 2.2% annually, or doubling every 32 years. The ten-year average has been 2.7% for a 26 year doubling.
The "gas reserves are trending upward" comment is consistent with the passage immediately preceding in Wikipedia noting that new discovery estimates are hard to establish, so they're often amended upwards. The increasing reserves noted by BP's CEO aren't the result of new finds, but of revised estimates of old finds. And new gas field discoveries peaked in the 1970s, 40 years ago. We're not finding new gas, we're simply recognizing how much was already found.
Fracking also isn't turning up new gas fields, but is allowing known plays to be further extracted. Again, it's digging further into what we'd already known about.
So: given BP's 2013 report of proved reserved of 187 trillion cubic meters, present consumption of 3,314 billion cubic meters, and an annual growth trend of 2.7%, we'll actually exhaust reserves by 2047. With a 2.2% growth trend, we'll last until 2050.
That could easily work. AFAIK a jet turbine will run fairly happily on just about anything, it's just a matter of making sure compatiblity is ok (that it doesn't corrode fuel lines, doesn't freeze at altitude, etc).
Elon Musk has talked about making electric planes, so I don't think they are entirely nuts.
Thinking out loud, you might build it with minimal fuel on board at all, doing a sled launch[1] or having it run its own engines off of external power for launch. Then require beamed power throughout the flight, with the provision that the plane can still land if all ground stations fail to provide power. But the plane starts and ends with less weight than a normal plane does because it's not carrying fuel, so it just might be feasible.
Then again, you can also manufacture hydrocarbons from atmospheric CO2 given energy input.
They exist. Do you have any references in which Musk details his plans other than "that would be cool"? Because I'm not finding anything.
All of the electric airplane work I've seen is either highly experimental (e.g., solar-powered aircraft), effectively powered gliders, or some very small and not-particularly-capable 1-2 person craft.
I mean, it's cool that humans won't have to give up the skies entirely, but we've also got perfectly viable aircraft with no engines whatsoever, for which a ground-tow launch is a present reality.
If you're looking at a credible commercial passenger or freight aviation model, this ain't it.
Fuel synthesis is something I've discussed elsewhere in this thread. I actually think the US Naval Research Lab's concept of using seawater as both an H2 and CO2 source is inspired -- there's about 140x the CO2 by volume than in air.
There may be some way to power it externally, like beamed microwave power. Sure there would be huge transmission losses, but the plane would weight a lot less, and the power could be from large, efficient ground based plants rather than portable engines.
A Boeing 777-300ER carries 304,000lbs of fuel fully loaded. This contains just under 6 terajoules of energy.
The battery pack of a Tesla Model S is about 300 megajoules.
So you,d need 19,700 Tesla battery packs to power your 777-equivilant jetliner. Problem is they weight over 15 millions pounds.
So no, there is no magic bullet in aviation.