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Electric Propulsion's Dirty Secret: Why Lithium Can't Fly (Or Float) Profitably

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Re: Electric Propulsion's Dirty Secret: Why Lithium Can't Fly (Or Float) Profitably

#151

Post by unyttigfjelltol »

pfdietz wrote: post #146
lawrenceduk wrote: post #139

Earlier quoted context omitted.

Pilot here, I don’t think this is right. Aircraft typically operate at 80-100% power output. It’s not the average 20% power output of your car. Weight is pretty much everything, the savings from regenerative braking in an aircraft are almost 0% but the cost of enabling it is some tons. This tech makes loads of sense in a car but I’ve never flown an aeroplane in stop-start traffic because that’s not how the sky works.

I don't see how that can possibly be correct, at least for commercial airliners. An airliner will use maximum power at takeoff, somewhat less for climbing, and much less during cruise. The figure I see is takeoff fuel consumption/hour is like 3x cruise fuel consumption/hour. Power needed will also decline as fuel is burned off, since the required lift goes down.

Thinner air. Engine is not capable of burning as much fuel, or generating as much thrust, with full performance at cruising altitude.

Re: Electric Propulsion's Dirty Secret: Why Lithium Can't Fly (Or Float) Profitably

#152

Post by XorNot »

pfdietz wrote: post #146
lawrenceduk wrote: post #139

Earlier quoted context omitted.

Pilot here, I don’t think this is right. Aircraft typically operate at 80-100% power output. It’s not the average 20% power output of your car. Weight is pretty much everything, the savings from regenerative braking in an aircraft are almost 0% but the cost of enabling it is some tons. This tech makes loads of sense in a car but I’ve never flown an aeroplane in stop-start traffic because that’s not how the sky works.

I don't see how that can possibly be correct, at least for commercial airliners. An airliner will use maximum power at takeoff, somewhat less for climbing, and much less during cruise. The figure I see is takeoff fuel consumption/hour is like 3x cruise fuel consumption/hour. Power needed will also decline as fuel is burned off, since the required lift goes down.

Couldn't this just be related to relative engine efficiency? You could easily be running the engines effectively full power the entire time, but obviously high-altitude cruise is where you spend most of your time and presumably the engine's are optimized for that operating regime.

Re: Electric Propulsion's Dirty Secret: Why Lithium Can't Fly (Or Float) Profitably

#153

Post by pfdietz »

unyttigfjelltol wrote: post #151
pfdietz wrote: post #146

Earlier quoted context omitted.

I don't see how that can possibly be correct, at least for commercial airliners. An airliner will use maximum power at takeoff, somewhat less for climbing, and much less during cruise. The figure I see is takeoff fuel consumption/hour is like 3x cruise fuel consumption/hour. Power needed will also decline as fuel is burned off, since the required lift goes down.

Thinner air. Engine is not capable of burning as much fuel, or generating as much thrust, with full performance at cruising altitude.

Ah, that explains it. Thank you.

Re: Electric Propulsion's Dirty Secret: Why Lithium Can't Fly (Or Float) Profitably

#154

Post by kjkjadksj »

MostlyStable wrote: post #25

Just going off the tweet about electric scooters being a scam: Nothing in that tweet is convincing. Let's just take at face value the assertion that a KWh of energy in an electric scooter costs $5 (as an EV owner: I'm skeptical). I'm going to use Lime (an SF based scooter rental company, chosen at random) as an example. I tried finding exact battery specs, and couldn't, but based on the range and some general scooter…

Driving it full speed is how you drive these things. They are safer when the speed delta is minimal between you and the rest of the traffic and you are charged by the minute so the incentive is full speed short of obligatory stopping for traffic lights or stops (really blown through) or slight slowing for turns.

Battery estimates fwiw are very optimistic on the app in my experience. Assume error of 1/3 in range to be safe.

Re: Electric Propulsion's Dirty Secret: Why Lithium Can't Fly (Or Float) Profitably

#155

Post by numpad0 »

api wrote: post #93
numpad0 wrote: post #85

Earlier quoted context omitted.

> They always assume that the technology will never get better, that industrial economies of scale don't exist The technology hadn't improved not much more than a quarter's worth so far in my lifetime as far as EV is concerned. Wh/kg figures hasn't changed, even fusion seems closer than solid state batteries, mileage figures for EVs is same 4mi/kWh, battery recycling still hasn't been figured out. They can't even rec…

Computers have psyched us out. There is no other technology in human history that has ever seen a capability growth curve like Moore's Law. Even aviation, which went from biplanes to moon landings in 50 years, doesn't compare. Still, there has been huge improvement in batteries. The main improvement has not been in energy density but in cost. Find some graphs of battery cost per kWh of storage. Storage cost has dropp…

Cost doesn't matter when something is just too darn heavy to be viable aviation fuel. Can't fly rockets on sails just because it's efficient.

Re: Electric Propulsion's Dirty Secret: Why Lithium Can't Fly (Or Float) Profitably

#156

Post by londons_explore »

Animats wrote: post #123
londons_explore wrote: post #92

For the marine uses specifically, the use of hydrofoils promises to dramatically reduce the amount of energy needed for movement at any decent speed. Previously hydrofoils weren't used because they rely on complex feedback mechanisms to maintain ride height despite waves etc. Sure, someone could pair hydrofoils with gasoline engines, but I suspect they won't, and that means hydrofoil+electric will win out over conven…

Probably not. Hydrofoil boats work OK, but few applications need the speed. The US Navy went through a period of hydrofoil enthusiasm, and built some.[1] Boeing built a hydrofoil ferry, and some are still in service. The Navy version used 10x as much fuel per hour in hydrofoil mode, running off a gas turbine. Of course, it was going fast in that mode. [1] https://www.youtube.com/watch?v=zQ2sSRBMPqs

> few applications need the speed.

Speed is key to profitability for most usecases. If you are transporting people from A to B, and you can do it in half the time, then you can make twice as many trips per day, doubling revenue (or, if there isn't enough demand, you can buy a smaller boat and reduce your capital costs whilst maintaining the same revenue).

And thats before you consider that by going faster you might win more marketshare because the users want the fastest route. And you can often charge extra per person/per ton for faster/express services.

Re: Electric Propulsion's Dirty Secret: Why Lithium Can't Fly (Or Float) Profitably

#157

Post by kjkjadksj »

londons_explore wrote: post #92

For the marine uses specifically, the use of hydrofoils promises to dramatically reduce the amount of energy needed for movement at any decent speed. Previously hydrofoils weren't used because they rely on complex feedback mechanisms to maintain ride height despite waves etc. Sure, someone could pair hydrofoils with gasoline engines, but I suspect they won't, and that means hydrofoil+electric will win out over conven…

They use t foil catamarans on the catalina express route. Diesel engines and water jet not gasoline though. Ride is about an hour to avalon from the port of long beach.

Re: Electric Propulsion's Dirty Secret: Why Lithium Can't Fly (Or Float) Profitably

#158

Post by kjkjadksj »

Aren’t airlines investing into zero carbon biofuels? Seems like that is not a bad route to go because you use the same paradigm of airliner but the fuel is carbon neutral and not contributing to greenhouse. Although it does continue to affect air quality downwind of the airport.

Re: Electric Propulsion's Dirty Secret: Why Lithium Can't Fly (Or Float) Profitably

#159

Post by kjkjadksj »

chris12321 wrote: post #7

I recently read The Ministry for the Future by Kim Stanley Robinson, and one of the ideas in it that I thought was very good was replacing our cargo ships with wind-powered ships, basically giant sailing ships. In the book, they were incredibly slow, with shipments taking months to complete, but if supply lines were set up correctly, that wouldn't matter for a lot of cargo. Cargo ships are a massive CO2 contributor,…

We probably don’t have the physical space to onshore 6x the capacity in warehouse or whatever it would work out to around ports. Short of multilevel warehouses but I mean containers have been stacked 5 high since covid around the port of LA and I think that is about the limit without some significant rethinking of process. Maybe the ships could just anchor off shore for longer and function as the warehouse.

Re: Electric Propulsion's Dirty Secret: Why Lithium Can't Fly (Or Float) Profitably

#160

Post by hedora »

xbmcuser wrote: post #144
fragmede wrote: post #121

Earlier quoted context omitted.

In the larger discuss is of course, solar panels, and how they can be installed cheaply enough and with enough storage to make it feasible. Vertical integration is the key here and yes it's additional initial capital outlay, but if someone wants to run the numbers, I bet there's somewhere where it makes sense.

He is wrong on the price of electricity by a factor of 100. The LCOE of solar and Bess is below cost of coal in China already ie around $0.04-0.05/kwh. Recently UAE signed a contract for 1 Gwh 24 hour solar and BESS supply for 10 years at around $6 billion which is approximately $0.07/kwh but after 10 years the solar and batteries will still be working at 85-90% capacity cost 0. I cant say about planes but as far as…

A bit later, he claims the lifetime cost of a vehicle is $345/kwh. It’s unclear if that’s capacity (an SUV with a $100kwh battery costs $34.5K new, which is the low end of retail pricing, and actually great news), or energy costs (that SUV will cost $34.5M over its lifetime, assuming 1000 charge cycles), which is clearly off by a factor of >100.

Either way, he concludes the time to payoff of switching to the planes is 2/3rds their expected lifetimes. I didn’t get far enough to find out what that’s versus, but most airlines would happily roll over to a new technology that “only” reduced their fleet costs by 33%.

For comparison, the 737 MAX reduced fuel costs by 14% and is still selling despite all the safety issues.

Edit: My 33% math is a bit off. It assumes the fuel costs dominate. Still, payoff before end of life is still saving money.

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