Our just-released ICCT report on electric aircraft concludes that electric models will be limited to short range flights (< 500 km) in the foreseeable future. Despite leaps-and-bounds improvements in battery technology in the past three decades, batteries remain inadequate to the task of electrifying most of passenger aviation. Our paper explored the capabilities of electric aircraft given current and projected battery technology. Now we address the inverse: how good do batteries need to be to power most flights?
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Comparing the required battery parameters with what is currently achievable highlights the difficulty in electrifying anything but commuter aircraft. Replacing regional, narrowbody, and widebody aircraft would require roughly 6x, 9x, and 20x improvements in the specific energy of the battery pack. In the 25 years from 1991 to 2015, the specific energy and energy density of lithium-ion batteries improved by a factor of 3. Assuming the same exponential growth (3x increase in 25 years), it will be 2090 before widebody aircraft can be electrified. However, this is impossible with current lithium-ion batteries or solid-state batteries, because of the physical limits of the chemistry of these technologies. The specific energy at the pack level for these batteries might not exceed 400-500 Wh/kg. New battery chemistries would need to be developed.
Does this daunting picture mean we should throw our hands up and stop developing electric aircraft? Not at all! The energy efficiency and zero-emission benefits of electric aircraft merit their adoption for short-hop commuter flights (9-19 passengers for < 200 km) wherever feasible. For example, short-hop flights are responsible for a disproportionate amount of local pollution from aircraft, so electric aircraft, which are zero-emission, could contribute to cleaner air in some regions. While these flights account for a sliver of aviation’s emissions, every electrified route represents a reduction in aviation’s climate impact and is a worthwhile investment.
From the article: I'd argue that is a pretty low bar assumption to assume 3x increase in the next 25 years given that for the vast majority of 1991 - 2015 there wasn't a massive push for huge...
From the article:
In the 25 years from 1991 to 2015, the specific energy and energy density of lithium-ion batteries improved by a factor of 3. Assuming the same exponential growth (3x increase in 25 years)
I'd argue that is a pretty low bar assumption to assume 3x increase in the next 25 years given that for the vast majority of 1991 - 2015 there wasn't a massive push for huge improvements in battery tech like there was since say 2010.
If the technology continues to improve, I can see it being adopted by commercial airlines for use on very local flights. I've occasionally had layovers between, say, England and Ireland in truly...
If the technology continues to improve, I can see it being adopted by commercial airlines for use on very local flights. I've occasionally had layovers between, say, England and Ireland in truly tiny passenger planes, which I guess count as "commuter" aircraft. The ICCT's actual report on CO2 Emissions from Commercial Aviation doesn't even seem to have this as a category, so I guess they're not joking when they call it "a sliver of aviation's emissions." I guess there is some advantage in doing the research on these smaller planes in order to scale it up to larger ones to the extent possible.
I suppose I have two categories of questions:
If long-haul flights won't be electrified for a long time, is it worthwhile to de-incentivize them on a governmental level? (That is, heavily tax them.) They have their own niche and there isn't really another mode to shift to, other than a million layovers. I know that Europe has recently banned many short-haul flights in order to encourage more train travel. At a certain point are we better off just... not flying? It would be a major lifestyle change for many people. I've often considered taking a ship across the Atlantic. I might do so one of these days.
What technologies are in the works to increase efficiency and decrease emissions of jet engines? Is it possible to develop "hybrid" models, like in cars? If battery technology can't really be applied to wide-body aircraft, we should still be investing in improvements to fossil fuel engines. (Or is this likely to increase accessibility and thereby increase overall emissions, even if per-capita emissions decrease? Are the benefits of that amount of travel worth it?)
I would ask about promising battery technologies to get around lithium-ion's physical limitations, but it's never been clear to me which of the batteries I hear about are the real deal and which are just gobbledygook.
Honestly, I think our best bet for reducing emissions for air travel (and rocketry, both applications where energy density is king) is to transition our fuel production into synthetic...
Honestly, I think our best bet for reducing emissions for air travel (and rocketry, both applications where energy density is king) is to transition our fuel production into synthetic hydrocarbons, with the carbon sourced from co2 capture. Its almost certainly easier than trying to transition the vehicles themselves to another energy source, where the only other thing that meets the energy density requirements would be a nuclear reactor, which are hard to due to their minimum size being rather large.
I also dont think long-haul flights can ever be eliminated, given the order of magnitude travel time disparity between them and ships when going overseas. Within a content, high speed train might be able to compete, but not ships.
There are a number of factors working against this. One is that the ”energy conversion unit” (motors) in cars are much more favorable towards EVs in ground travel vs air. Cars use piston engines,...
What technologies are in the works to increase efficiency and decrease emissions of jet engines? Is it possible to develop "hybrid" models, like in cars?
There are a number of factors working against this.
One is that the ”energy conversion unit” (motors) in cars are much more favorable towards EVs in ground travel vs air.
Cars use piston engines, which, while reliable and fairly fuel efficient, are very, very heavy. The motors that EVs use are extremely lightweight and small in comparison, which helps mitigate some of the extra weight needed in the storage device (batteries are WAY heavier than fuel tanks, especially when both are near empty).
You don’t have as much of an advantage in air travel, which use jet engines, which are way lighter per unit of power than piston engines.
Secondly, hybrid vehicles work because they’re able to scavenge energy that would be otherwise wasted by dumping it into heat via braking. Regenerative braking systems are the reason why hybrid vehicles exist at all. Obviously, airplanes don’t use brakes. They fly through the air at a relatively constant speed, and if they ever need to slow down, they just ease up on the throttle and let drag take care of the rest, so there’s no excess energy to scavenge.
There are a lot of technologies that have allowed jet engines to be more efficient though, and modern high bypass turbofans are way more efficient nowadays than they were even 20 years ago. Luckily the economics of air travel means that airlines and plane manufacturers are already heavily incentivized to prioritize efficiency, because competition on airfare is almost solely based on price, and fuel is one of the biggest costs that contribute to the price of a ticket, so if a manufacturer can boast even a modest increase in efficiency, airlines are willing to pay for it.
It seems like making jet fuel in a carbon-neutral way would be the way to go? There is some work on this. A carbon tax would provide the incentives to deploy this sooner, while also making jet...
It seems like making jet fuel in a carbon-neutral way would be the way to go? There is some work on this. A carbon tax would provide the incentives to deploy this sooner, while also making jet travel more expensive without it.
From the article:
…
From the article:
I'd argue that is a pretty low bar assumption to assume 3x increase in the next 25 years given that for the vast majority of 1991 - 2015 there wasn't a massive push for huge improvements in battery tech like there was since say 2010.
https://cleantechnica.com/2020/02/19/bloombergnef-lithium-ion-battery-cell-densities-have-almost-tripled-since-2010/
According to the link above, we have already 3x from 2010-2020...
If the technology continues to improve, I can see it being adopted by commercial airlines for use on very local flights. I've occasionally had layovers between, say, England and Ireland in truly tiny passenger planes, which I guess count as "commuter" aircraft. The ICCT's actual report on CO2 Emissions from Commercial Aviation doesn't even seem to have this as a category, so I guess they're not joking when they call it "a sliver of aviation's emissions." I guess there is some advantage in doing the research on these smaller planes in order to scale it up to larger ones to the extent possible.
I suppose I have two categories of questions:
I would ask about promising battery technologies to get around lithium-ion's physical limitations, but it's never been clear to me which of the batteries I hear about are the real deal and which are just gobbledygook.
Honestly, I think our best bet for reducing emissions for air travel (and rocketry, both applications where energy density is king) is to transition our fuel production into synthetic hydrocarbons, with the carbon sourced from co2 capture. Its almost certainly easier than trying to transition the vehicles themselves to another energy source, where the only other thing that meets the energy density requirements would be a nuclear reactor, which are hard to due to their minimum size being rather large.
I also dont think long-haul flights can ever be eliminated, given the order of magnitude travel time disparity between them and ships when going overseas. Within a content, high speed train might be able to compete, but not ships.
There are a number of factors working against this.
One is that the ”energy conversion unit” (motors) in cars are much more favorable towards EVs in ground travel vs air.
Cars use piston engines, which, while reliable and fairly fuel efficient, are very, very heavy. The motors that EVs use are extremely lightweight and small in comparison, which helps mitigate some of the extra weight needed in the storage device (batteries are WAY heavier than fuel tanks, especially when both are near empty).
You don’t have as much of an advantage in air travel, which use jet engines, which are way lighter per unit of power than piston engines.
Secondly, hybrid vehicles work because they’re able to scavenge energy that would be otherwise wasted by dumping it into heat via braking. Regenerative braking systems are the reason why hybrid vehicles exist at all. Obviously, airplanes don’t use brakes. They fly through the air at a relatively constant speed, and if they ever need to slow down, they just ease up on the throttle and let drag take care of the rest, so there’s no excess energy to scavenge.
There are a lot of technologies that have allowed jet engines to be more efficient though, and modern high bypass turbofans are way more efficient nowadays than they were even 20 years ago. Luckily the economics of air travel means that airlines and plane manufacturers are already heavily incentivized to prioritize efficiency, because competition on airfare is almost solely based on price, and fuel is one of the biggest costs that contribute to the price of a ticket, so if a manufacturer can boast even a modest increase in efficiency, airlines are willing to pay for it.
It seems like making jet fuel in a carbon-neutral way would be the way to go? There is some work on this. A carbon tax would provide the incentives to deploy this sooner, while also making jet travel more expensive without it.