7 ms·

So, avgas has about 45 MJ/kg energy density, lithium ion batteries have 0.5 MJ/kg. Aviation engines are maybe 30% efficient, while electrics are about 90% effic

So, avgas has about 45 MJ/kg energy density, lithium ion batteries have 0.5 MJ/kg. Aviation engines are maybe 30% efficient, while electrics are about 90% efficient, so we've got about 15 MJ/kg usable versus 0.45 MJ/kg usable. Double the energy density of a lithium battery, and you're at 0.9 MJ/kg usable, versus 15. We're not there yet to propel airplanes with batteries, not useful ones, anyway.

mnbvkhgvmj 7y ago
Not for long haul jet flights anyway.
fulafel 7y ago
The current planes fly enormous distances - 15000 km - without refueling. (And there is not a lot od evidence that even this is fuel mass limited.) There are a lot of 2000 km routes to be replaced, like most countries' domestic flights. But yep, it's not a solution for keeping our current flying habits. We will have to cut down on flying, a lot.
- AmericanChopper 7y ago
  If you solution to a problem is “massive reduction in critically important infrastructure”, then you might not have a solution.
  - fulafel 7y ago
    You can call a lot of things "critical infrastructure" but it doesn't mean we can't phase out many of those those things in an orderly fashion. It just means dependencies we've added to our life, many of which are very recent. We have to make compromises, unless we prefer to lose the global warming battle. Humanity's benefits from cheap air travel are much less than losses from unchecked climate change.
    - AmericanChopper 7y ago
      This argument has absolutely no basis in economics. There is currently a particular demand for air travel. If you want to reduce that demand, you can only do one of the following things: 1. Create a competing product that people prefer over air travel. 2. Artificially increase the price through taxation. 3. Artificially decrease supply through regulation. There’s nothing on the horizon for option 1, and since we live in a democracy, democratic mechanisms are the only means you have for 2 or 3, unless you wanted to resort to something like terrorism. Your presupposition that we can’t have cheap air travel while avoiding catastrophic man-made climate change is in no way obviously true, and your suggested solution is a utopian fantasy.
      - fulafel 7y ago
        Your argument presupposes that we let the free market run its course, but it's widely agreed that co2 emission controls will have to involve regulation or market steeting such as emissions trading.
        AmericanChopper 7y ago
        Putting aside for a moment the fact that the most significant reductions in emissions have been generated by free market activity. You haven’t proposed gentle market steering and incentive creation, you quite literally suggested the “phasing out” of air travel.
        zzzcpan 7y ago
        > the most significant reductions in emissions have been generated by free market activity Not sure what you mean, globally there are no reductions in emissions. And you would have to phase out a lot more than just air travel. Personal cars too and overall reduce consumption like ten fold or more, basically destroy this whole capitalism-driven consumerist way of life.
        AmericanChopper 7y ago
  - tonyedgecombe 7y ago
    Flying on such a huge scale is a relatively recent occurrence, very little of it is critical, the world isn't going to end because you can't holiday in Bali.
    - AmericanChopper 7y ago
      Airports are a part of every country’s critical infrastructure. > the world isn't going to end because you can't holiday in Bali Perhaps not. But the Balinese economy would simply collapse. I’m sure the Balinese economy is of critical importance to the ~4 million people who live there. What you’ve chosen as a contrived example doesn’t even illustrate your point.
      - tonyedgecombe 7y ago
        On the other hand: https://www.worldcrunch.com/food-travel/how-mass-tourism-is-destroying-bali-and-its-culture https://www.worldcrunch.com/food-travel/how-mass-tourism-is-... perfectly illustrates the problems with your thinking.
        AmericanChopper 7y ago
        My thinking doesn’t have anything to do with it, it’s simply a fact that 80% of Bali’s economy is tourism. An industry specifically promoted by the Indonesian government as a long standing policy. “But, what if tourism wasn’t critical to the Balinese economy, what if they had instead spend the last 50 years developing a different industry” you might say. Well, who knows. But they didn’t, and the criticality of air travel to Bali is not up for any meaningful debate.
        Tharkun 7y ago
        This argument doesn't hold much water. Sure, it might be technically correct for Balinese ecomomy. But lots of people fly lots of places for very capricious reasons. If vacation is the goal, then everyone can go on a trip a bit closer to home without flying. Certain major tourism centers will lose out, but on average, there will be just as many tourists, just in different places. Air travel is far too cheap, everything else follows from that.
- evandijk70 7y ago
  Actually, the range of current planes is absolutely fuel mass limited. The 777-LR, which can reach these distances, carries up to 145 000 kg of fuel. This is 42% of its maximal take-off weight [1]. As a result of added weight for longer distances, planes use the least amount of fuel/km on flights of 2500 km, despite the extra fuel used to take off [2] An electric plane flying 2000 km as opposed to 15 000 km would require an even larger proportion of their take of weight as batteries, and would thus not be able to carry a lot of passengers/cargo on such a relatively short flight. It will require a fundamental breakthrough to make passenger flights of that distance economically feasible. [1] https://en.wikipedia.org/wiki/Boeing_777#Specifications https://en.wikipedia.org/wiki/Boeing_777#Specifications [2] https://en.wikipedia.org/wiki/Fuel_economy_in_aircraft#/media/File:777-224_fuel_burn-range.png https://en.wikipedia.org/wiki/Fuel_economy_in_aircraft#/medi...
duaoebg 7y ago
Another big problem is landing weight limits which are lower than takeoff limits.
Dylan16807 7y ago
That's not the right analysis at all. Imagine if you did the same math for avgas in a world where some other fuel does 100 MJ/kg. You'd declare "We're not there yet to propel airplanes with avgas, not useful ones, anyway". You don't have to outperform existing solutions to have a viable product. Price and other factors can easily swamp a particular performance stat. Different performance will lead to different use cases, but that is in no way the same as zero use cases.
- close04 7y ago
  I guess we can sum it up as "it can't replace everything (yet)".
lb1lf 7y ago
Some markets are viable - even well suited - for electrically propelled planes. Norway is sparsely populated and it has been a strategy for decades to have small airports everywhere out in the boonies. Most flights are operated by twin-engined turboprops seating 20-80 passengers, in part doing short flights between islands in the north - an excellent use case for electrical planes. The big question is whether one can recharge them fast enough - by swapping battery packs if need be. No airline is interested in replacing 50 turboprops with 100 electro planes to serve the same routes.

mnbvkhgvmj 7y ago

Not for long haul jet flights anyway.

fulafel 7y ago

The current planes fly enormous distances - 15000 km - without refueling. (And there is not a lot od evidence that even this is fuel mass limited.) There are a lot of 2000 km routes to be replaced, like most countries' domestic flights. But yep, it's not a solution for keeping our current flying habits. We will have to cut down on flying, a lot.

AmericanChopper 7y ago
If you solution to a problem is “massive reduction in critically important infrastructure”, then you might not have a solution.
- fulafel 7y ago
  You can call a lot of things "critical infrastructure" but it doesn't mean we can't phase out many of those those things in an orderly fashion. It just means dependencies we've added to our life, many of which are very recent. We have to make compromises, unless we prefer to lose the global warming battle. Humanity's benefits from cheap air travel are much less than losses from unchecked climate change.
  - AmericanChopper 7y ago
    This argument has absolutely no basis in economics. There is currently a particular demand for air travel. If you want to reduce that demand, you can only do one of the following things: 1. Create a competing product that people prefer over air travel. 2. Artificially increase the price through taxation. 3. Artificially decrease supply through regulation. There’s nothing on the horizon for option 1, and since we live in a democracy, democratic mechanisms are the only means you have for 2 or 3, unless you wanted to resort to something like terrorism. Your presupposition that we can’t have cheap air travel while avoiding catastrophic man-made climate change is in no way obviously true, and your suggested solution is a utopian fantasy.
    - fulafel 7y ago
      Your argument presupposes that we let the free market run its course, but it's widely agreed that co2 emission controls will have to involve regulation or market steeting such as emissions trading.
      - AmericanChopper 7y ago
        Putting aside for a moment the fact that the most significant reductions in emissions have been generated by free market activity. You haven’t proposed gentle market steering and incentive creation, you quite literally suggested the “phasing out” of air travel.
        zzzcpan 7y ago
        > the most significant reductions in emissions have been generated by free market activity Not sure what you mean, globally there are no reductions in emissions. And you would have to phase out a lot more than just air travel. Personal cars too and overall reduce consumption like ten fold or more, basically destroy this whole capitalism-driven consumerist way of life.
        AmericanChopper 7y ago
- tonyedgecombe 7y ago
  Flying on such a huge scale is a relatively recent occurrence, very little of it is critical, the world isn't going to end because you can't holiday in Bali.
  - AmericanChopper 7y ago
    Airports are a part of every country’s critical infrastructure. > the world isn't going to end because you can't holiday in Bali Perhaps not. But the Balinese economy would simply collapse. I’m sure the Balinese economy is of critical importance to the ~4 million people who live there. What you’ve chosen as a contrived example doesn’t even illustrate your point.
    - tonyedgecombe 7y ago
      On the other hand: https://www.worldcrunch.com/food-travel/how-mass-tourism-is-destroying-bali-and-its-culture https://www.worldcrunch.com/food-travel/how-mass-tourism-is-... perfectly illustrates the problems with your thinking.
      - AmericanChopper 7y ago
        My thinking doesn’t have anything to do with it, it’s simply a fact that 80% of Bali’s economy is tourism. An industry specifically promoted by the Indonesian government as a long standing policy. “But, what if tourism wasn’t critical to the Balinese economy, what if they had instead spend the last 50 years developing a different industry” you might say. Well, who knows. But they didn’t, and the criticality of air travel to Bali is not up for any meaningful debate.
        Tharkun 7y ago
        This argument doesn't hold much water. Sure, it might be technically correct for Balinese ecomomy. But lots of people fly lots of places for very capricious reasons. If vacation is the goal, then everyone can go on a trip a bit closer to home without flying. Certain major tourism centers will lose out, but on average, there will be just as many tourists, just in different places. Air travel is far too cheap, everything else follows from that.
evandijk70 7y ago
Actually, the range of current planes is absolutely fuel mass limited. The 777-LR, which can reach these distances, carries up to 145 000 kg of fuel. This is 42% of its maximal take-off weight [1]. As a result of added weight for longer distances, planes use the least amount of fuel/km on flights of 2500 km, despite the extra fuel used to take off [2] An electric plane flying 2000 km as opposed to 15 000 km would require an even larger proportion of their take of weight as batteries, and would thus not be able to carry a lot of passengers/cargo on such a relatively short flight. It will require a fundamental breakthrough to make passenger flights of that distance economically feasible. [1] https://en.wikipedia.org/wiki/Boeing_777#Specifications https://en.wikipedia.org/wiki/Boeing_777#Specifications [2] https://en.wikipedia.org/wiki/Fuel_economy_in_aircraft#/media/File:777-224_fuel_burn-range.png https://en.wikipedia.org/wiki/Fuel_economy_in_aircraft#/medi...

duaoebg 7y ago

Another big problem is landing weight limits which are lower than takeoff limits.

Dylan16807 7y ago

That's not the right analysis at all. Imagine if you did the same math for avgas in a world where some other fuel does 100 MJ/kg. You'd declare "We're not there yet to propel airplanes with avgas, not useful ones, anyway". You don't have to outperform existing solutions to have a viable product. Price and other factors can easily swamp a particular performance stat. Different performance will lead to different use cases, but that is in no way the same as zero use cases.

close04 7y ago
I guess we can sum it up as "it can't replace everything (yet)".

lb1lf 7y ago

Some markets are viable - even well suited - for electrically propelled planes. Norway is sparsely populated and it has been a strategy for decades to have small airports everywhere out in the boonies. Most flights are operated by twin-engined turboprops seating 20-80 passengers, in part doing short flights between islands in the north - an excellent use case for electrical planes. The big question is whether one can recharge them fast enough - by swapping battery packs if need be. No airline is interested in replacing 50 turboprops with 100 electro planes to serve the same routes.