4 ms·

Still orders of magnitude less energy-dense than jet fuel.

by ddoice 6y ago

henearkr 6y ago
To be fair, you need to compare a complete workflow including the renewable production of the jet fuel. If the overhead of heavy batteries does not annihilate the benefit of the carbon-neutral production rendered possible by using electricity (and associated carbon-neutral sources like photovoltaic etc... heck, even nuclear fission), then batteries are still the path to go. If there are carbon-neutral ways to produce the jet-fuel, and to have a completely carbon-neutral(or even negative) cycle production+consumption, then why not. If it could be done without turning the Earth into a giant bio-fuel crop, that would be nice.
umvi 6y ago
Yes but presumably electricity is order(s) of magnitude cheaper than jet fuel. And also order(s) of magnitude more available than jet fuel. And also order(s) of magnitude cleaner than jet fuel (depending on the source).
- bronco21016 6y ago
  I'd debate the 'more available' statement. It is more widely available overall but not in the places you'd want it. Of course that can be fixed but someone will have to build out that infrastructure to make electric planes viable. It's a bit like Tesla. Prior to them building out their charging network, electric cars had a bit of a chicken and the egg problem. You might buy a car but have no where to charge it, but nobody wanted to build places to charge them because nobody has an electric car.
  - harg 6y ago
    That’s not the case at all. Everyone has electricity at their home. You can charge basically any electric car from a domestic wal socket and higher power chargers are easily available. Commercial charge points only really need to be used for long distance travel. Most EV owners can do the majority of charging at home.
    - lacksconfidence 6y ago
      One confounding factor is parking arrangements. If you have a garage then a wall socket is reasonable, but for many years the only place i could park a car was somewhere on the street, hopefully within 100m of my address. In that situation commercial charge points (hopefully near my employer, if lucky) would be the only reasonable charge point.
    - tuatoru 6y ago
      > Everyone has electricity at their home. I do. But I can't get the car up the stairs. :-(
  - bdamm 6y ago
    Yeah basically all airports that have commercial service also have access to power. There are exceptions like seaplane bases and small country strips, but there are more than enough airports with access to commercial or even industrial grade power to make electric airplanes that require charging viable. The final step of linking up the airport power supply to the airplane charger is peanuts in the world of aviation. Almost all airports have a fleet of fuel trucks, therefore, the cost of buying a fuel truck is the low end of the acceptable cost for ground infrastructure investment to open a new route for an airline.
    - bronco21016 6y ago
      I just reread what I wrote and I think maybe I wasn’t very clear. There’s electricity at every single gas station in the US. Why can’t we pull into any gas station in the US and charge an electric car? Even now that electric cars are gaining market share and becoming more common. Someone has to build, supply, and hook up high power charging systems. You can’t just fly your $5 million eJet into any airport in the US and run a 100’ extension cord into the FBO. If that’s the plan, you certainly can’t hope to leave the same day. It will take at least 3 days for your 1 MWh eJet to finish charging. We’re in the pre-Tesla days of electric aircraft. There’s a few players working on the aircraft and they’re getting close. However, until a ‘Tesla’ comes along where they also install charging infrastructure at the airports their customers are planning on using, we’re not going to see a commercially viable electric aircraft.
      - ramses0 6y ago
        The best way to do it would be start in the corners and cross in the middle. Seattle/SF/LA => { colorado? vegas? texas? chicago? } => NY/DC/Miami If you can link up some sort of route(s) to deal with range-anxiety / weather, and can criss-cross the country, you're in business. Once your route is built, it's straightforward to manage capacity/flight-plans (reservations / networks / routing), and then you move directly to demand-generation, but you'll have a real tough time competing directly with coast-to-coast direct flights.
        6y ago
- aphextron 6y ago
  >Yes but presumably electricity is order(s) of magnitude cheaper than jet fuel. It's really not even about the cost of fuel. With aviation it's all about maintenance costs. Electric aircraft will be orders of magnitude simpler and cheaper to maintain than jet turbines. This is what will unlock cost effective small scale commuter routes, allowing you to just hop on a small 10 passenger plane at a neighborhood airport and take a 300 mile flight with no need for security.
- asdfadsfgfdda 6y ago
  Jet fuel is ~36 kWh/gallon raw energy density (13 kWh/gallon mechanical power assuming 35% engine efficiency). The pre-covid jet fuel price was $2/gallon, or $.15/kWh. The average price of commercial electricity is $.06/kWh in America, or $.08/kWh including charging/motor efficiency. This cost will definitely be higher if you only buy clean electricity, and this ignores battery wear out. But where the economics break down is aircraft utilization. If charge time is greater than ~1 hour typical turn time, all of your costs will grow. Capital cost, crew costs, and airport infrastructure cost will increase. To charge in <1 hr is a challenge, you need a huge power source (tens of megawatts per plane) and serious cooling.
  - ramses0 6y ago
    Or swap the component, although that introduces its own design challenges and provenance risks. Aircraft refueling generally runs in-ground (at the largest airports), then 5-10k gallon trucks (~20-40k liters), then ~500-2000 gallon smaller trucks (2k-10k liters) for smaller aircraft or smaller airports. If you reimagined refueling trucks as "forklifts carrying batteries" instead of "tubes of gasoline on wheels" then you'd likely end up with similar delivery practices (central charging, swap/refuel, discard/recharge batteries instead of refilling the fuel tank on a fuel truck). Effectively it would be standardizing on some way to slot-in pre-charged batteries, and treat them similar to a propane tank rental company, where each removed battery is considered suspect and tested/refurbished/recharged after each use. Otherwise, yeah, putting a bunch of 220v outlets in the ground around an airport... you're going to be sitting there a while to recharge the ten planes that landed that day. It'd effectively be untenable for smaller airports to be able to provide "quick-turn" refueling services, and potentially risky to be able to guarantee overnight refueling. This is all nudging towards personal / corporate aircraft, not commercial aircraft operations, which would "never" want the plane in more than one spot for more than one hour, which would require something similar to battery-swaps that they control, OR some very fancy electrical and heat management associated with the airport/jetbridge that the plane pulls up at.
DesiLurker 6y ago
IIRC real-engineering on youtube did a detailed analysis of the current operating limitations with electric planes: https://www.youtube.com/watch?v=VNvzZfsC13o https://www.youtube.com/watch?v=VNvzZfsC13o He also identified a couple of sweet spots where electric flight would make sense factoring in engine efficiency & cost of fuel etc. bottom line is that the picture is more complex than just comparing energy density of jet-fuel & batteries. with batteries becoming much lighter IMO it should open up many more use cases for short haul frequent flights without the need of big central hub airports. which is good. an more importantly give the trajectory of battery energy density it should provide enough justification for heavy investment into research into electric planes so i wouldn't dismiss it out of hand.
blisterpeanuts 6y ago
>> Still orders of magnitude less energy-dense than jet fuel. Does that matter, if other aspects of the system compensate with lighter weight? For example, lighter weight electric engines versus heavier fuel-burning engines along with exhaust and cooling systems.
- asdfadsfgfdda 6y ago
  A PW150 turboshaft engine is ~5 kW/kg. Some electric motors are up to ~10 kW/kg. But, as an example, engines on a Q400 regional airliner are only ~5% of the total weight. Fuel is up to 15% of total weight. So the savings are not significant. Also, the batteries will likely require a cooling solution. This can be challenging (heavy) for high altitudes (where air is cold but very low density). Jet fuel requires no cooling. https://en.wikipedia.org/wiki/Power-to-weight_ratio https://en.wikipedia.org/wiki/Power-to-weight_ratio
- threeseed 6y ago
  If it's anything like ships/yachts then the lighter weight doesn't come anywhere close to making up for the loss of energy. Could still be very useful for flights between nearby cities e.g. LAX to SF.

Still orders of magnitude less energy-dense than jet fuel.

by ddoice 6y ago

Still orders of magnitude less energy-dense than jet fuel.

To be fair, you need to compare a complete workflow including the renewable production of the jet fuel. If the overhead of heavy batteries does not annihilate the benefit of the carbon-neutral production rendered possible by using electricity (and associated carbon-neutral sources like photovoltaic etc... heck, even nuclear fission), then batteries are still the path to go. If there are carbon-neutral ways to produce the jet-fuel, and to have a completely carbon-neutral(or even negative) cycle production+consumption, then why not. If it could be done without turning the Earth into a giant bio-fuel crop, that would be nice.

umvi 6y ago

Yes but presumably electricity is order(s) of magnitude cheaper than jet fuel. And also order(s) of magnitude more available than jet fuel. And also order(s) of magnitude cleaner than jet fuel (depending on the source).

bronco21016 6y ago
I'd debate the 'more available' statement. It is more widely available overall but not in the places you'd want it. Of course that can be fixed but someone will have to build out that infrastructure to make electric planes viable. It's a bit like Tesla. Prior to them building out their charging network, electric cars had a bit of a chicken and the egg problem. You might buy a car but have no where to charge it, but nobody wanted to build places to charge them because nobody has an electric car.
- harg 6y ago
  That’s not the case at all. Everyone has electricity at their home. You can charge basically any electric car from a domestic wal socket and higher power chargers are easily available. Commercial charge points only really need to be used for long distance travel. Most EV owners can do the majority of charging at home.
  - lacksconfidence 6y ago
    One confounding factor is parking arrangements. If you have a garage then a wall socket is reasonable, but for many years the only place i could park a car was somewhere on the street, hopefully within 100m of my address. In that situation commercial charge points (hopefully near my employer, if lucky) would be the only reasonable charge point.
  - tuatoru 6y ago
    > Everyone has electricity at their home. I do. But I can't get the car up the stairs. :-(
- bdamm 6y ago
  Yeah basically all airports that have commercial service also have access to power. There are exceptions like seaplane bases and small country strips, but there are more than enough airports with access to commercial or even industrial grade power to make electric airplanes that require charging viable. The final step of linking up the airport power supply to the airplane charger is peanuts in the world of aviation. Almost all airports have a fleet of fuel trucks, therefore, the cost of buying a fuel truck is the low end of the acceptable cost for ground infrastructure investment to open a new route for an airline.
  - bronco21016 6y ago
    I just reread what I wrote and I think maybe I wasn’t very clear. There’s electricity at every single gas station in the US. Why can’t we pull into any gas station in the US and charge an electric car? Even now that electric cars are gaining market share and becoming more common. Someone has to build, supply, and hook up high power charging systems. You can’t just fly your $5 million eJet into any airport in the US and run a 100’ extension cord into the FBO. If that’s the plan, you certainly can’t hope to leave the same day. It will take at least 3 days for your 1 MWh eJet to finish charging. We’re in the pre-Tesla days of electric aircraft. There’s a few players working on the aircraft and they’re getting close. However, until a ‘Tesla’ comes along where they also install charging infrastructure at the airports their customers are planning on using, we’re not going to see a commercially viable electric aircraft.
    - ramses0 6y ago
      The best way to do it would be start in the corners and cross in the middle. Seattle/SF/LA => { colorado? vegas? texas? chicago? } => NY/DC/Miami If you can link up some sort of route(s) to deal with range-anxiety / weather, and can criss-cross the country, you're in business. Once your route is built, it's straightforward to manage capacity/flight-plans (reservations / networks / routing), and then you move directly to demand-generation, but you'll have a real tough time competing directly with coast-to-coast direct flights.
      - 6y ago
aphextron 6y ago
>Yes but presumably electricity is order(s) of magnitude cheaper than jet fuel. It's really not even about the cost of fuel. With aviation it's all about maintenance costs. Electric aircraft will be orders of magnitude simpler and cheaper to maintain than jet turbines. This is what will unlock cost effective small scale commuter routes, allowing you to just hop on a small 10 passenger plane at a neighborhood airport and take a 300 mile flight with no need for security.
asdfadsfgfdda 6y ago
Jet fuel is ~36 kWh/gallon raw energy density (13 kWh/gallon mechanical power assuming 35% engine efficiency). The pre-covid jet fuel price was $2/gallon, or $.15/kWh. The average price of commercial electricity is $.06/kWh in America, or $.08/kWh including charging/motor efficiency. This cost will definitely be higher if you only buy clean electricity, and this ignores battery wear out. But where the economics break down is aircraft utilization. If charge time is greater than ~1 hour typical turn time, all of your costs will grow. Capital cost, crew costs, and airport infrastructure cost will increase. To charge in <1 hr is a challenge, you need a huge power source (tens of megawatts per plane) and serious cooling.
- ramses0 6y ago
  Or swap the component, although that introduces its own design challenges and provenance risks. Aircraft refueling generally runs in-ground (at the largest airports), then 5-10k gallon trucks (~20-40k liters), then ~500-2000 gallon smaller trucks (2k-10k liters) for smaller aircraft or smaller airports. If you reimagined refueling trucks as "forklifts carrying batteries" instead of "tubes of gasoline on wheels" then you'd likely end up with similar delivery practices (central charging, swap/refuel, discard/recharge batteries instead of refilling the fuel tank on a fuel truck). Effectively it would be standardizing on some way to slot-in pre-charged batteries, and treat them similar to a propane tank rental company, where each removed battery is considered suspect and tested/refurbished/recharged after each use. Otherwise, yeah, putting a bunch of 220v outlets in the ground around an airport... you're going to be sitting there a while to recharge the ten planes that landed that day. It'd effectively be untenable for smaller airports to be able to provide "quick-turn" refueling services, and potentially risky to be able to guarantee overnight refueling. This is all nudging towards personal / corporate aircraft, not commercial aircraft operations, which would "never" want the plane in more than one spot for more than one hour, which would require something similar to battery-swaps that they control, OR some very fancy electrical and heat management associated with the airport/jetbridge that the plane pulls up at.

DesiLurker 6y ago

IIRC real-engineering on youtube did a detailed analysis of the current operating limitations with electric planes: https://www.youtube.com/watch?v=VNvzZfsC13o https://www.youtube.com/watch?v=VNvzZfsC13o He also identified a couple of sweet spots where electric flight would make sense factoring in engine efficiency & cost of fuel etc. bottom line is that the picture is more complex than just comparing energy density of jet-fuel & batteries. with batteries becoming much lighter IMO it should open up many more use cases for short haul frequent flights without the need of big central hub airports. which is good. an more importantly give the trajectory of battery energy density it should provide enough justification for heavy investment into research into electric planes so i wouldn't dismiss it out of hand.

blisterpeanuts 6y ago

>> Still orders of magnitude less energy-dense than jet fuel. Does that matter, if other aspects of the system compensate with lighter weight? For example, lighter weight electric engines versus heavier fuel-burning engines along with exhaust and cooling systems.

asdfadsfgfdda 6y ago
A PW150 turboshaft engine is ~5 kW/kg. Some electric motors are up to ~10 kW/kg. But, as an example, engines on a Q400 regional airliner are only ~5% of the total weight. Fuel is up to 15% of total weight. So the savings are not significant. Also, the batteries will likely require a cooling solution. This can be challenging (heavy) for high altitudes (where air is cold but very low density). Jet fuel requires no cooling. https://en.wikipedia.org/wiki/Power-to-weight_ratio https://en.wikipedia.org/wiki/Power-to-weight_ratio
threeseed 6y ago
If it's anything like ships/yachts then the lighter weight doesn't come anywhere close to making up for the loss of energy. Could still be very useful for flights between nearby cities e.g. LAX to SF.