Electric commercial flight

[Siwastaja]

I can't imagine planes literally being completely flat as they land, a significant safety margin is clearly required.

They won't be flat, but adding the margin on bottom doesn't help with battery cycle life that much; most of the cycling damage is done charging near top, especially at high charge rates. To have that safety margin, the cells would have to be charged near 100%; and given the hectic schedules, at significant charge rate. Basically it would need to be some 35% - 95% cycles in one hour which works out some 0.6C average. You are not really stress-quick-charging, but not doing easy cycles either, quite close to "standard" conditions actually which result in some 500-1000 cycles.

So while 500 cycles might not be the exact limit, 1000 might be achievable with the current tech, mzzj is mostly correct in this point. You can't derate the cells much to increase the cycle life. You can't slow down charging already at 80% like Tesla does.

But I do question the assumption of the nearly-50% jet engine efficiency used by mzzj. I suspect this number is at highly optimum conditions. Designed to provide good overall efficiency for long flights, jet engines are likely a lot more inefficient during taxiing, takeoff, climb, and again, when running (near-)idle during descent. Electric shines in providing good efficiency at large dynamic range, important at short trips.

In order to make reliable calculations, I think we shouldn't try to back-calculate flight energy usage from the fuel consumption times assumed efficiency, but instead go more directly at the source and use actual mechanical energy requirements, mostly regarding aerodynamics. But sadly I can't contribute with actual numbers here. I know it's so easy just to take the well-known fuel consumption numbers for existing passenger jets then work from there, but there are quite some many hidden assumptions.

In any case, I don't think we can twist the reality to make this viable with the current battery technology, not even close, but OTOH, it's hard to predict what happens with battery technology.

[sandalcandal]

Far more so than with cars, swappable batteries would make a lot of sense and be much more practical for commercial flight operations. A need for high up time, the ability to reduce recharging stress on cells, having depot facilities and trained technicians available, the cost vs. benefits would likely weigh out far better for electric aviation than it did for electric cars. I think it's highly likely we'll see serious implementation of battery swapping for "practical" commercial electric aviation as it comes out.

[Siwastaja]

I don't believe in viability of swappable batteries, that's always a complex mechanical disaster which adds weight and cost. Even Tesla failed at it (deliberately, of course; it was just a publicity stunt for dumb people who think swappable batteries are a good idea and Tesla "should" do it.)

There is no reason, because there is no need for 15-minute quick charge cycles. There is plenty of time for normal charge. Currently, fueling, loading cargo and passengers, and doing all necessary checks, shutting down and starting jet engines take somewhere around an hour, or more. Note that charging power is easy to supply from multitude of points at the airport. It's like the "ground power" currently is, just a thicker cable and heavier connectors.

[Rx7man]

I don't believe in viability of swappable batteries, that's always a complex mechanical disaster which adds weight and cost. Even Tesla failed at it (deliberately, of course; it was just a publicity stunt for dumb people who think swappable batteries are a good idea and Tesla "should" do it.)

There is no reason, because there is no need for 15-minute quick charge cycles. There is plenty of time for normal charge. Currently, fueling, loading cargo and passengers, and doing all necessary checks, shutting down and starting jet engines take somewhere around an hour, or more. Note that charging power is easy to supply from multitude of points at the airport. It's like the "ground power" currently is, just a thicker cable and heavier connectors.

I'll bring your attention to this post if you missed it.. That charging power is NOT easy to supply

But then the plane lands. And you need to charge it up. Planes dont make money on the ground, so better do it fast. There are 500.000 Airplanes / year on Frankfurt airport. That's more than 1000 / day, or 62/hour. Counting with 65/ hour, that is 1500MW continuous charging. That's about 2-3 nuclear reactors operated next to the airport.

[Red Squirrel]

If you go on Flightaware or similar site and realize how many planes are in the air at any given time it's mind boggling.  Even if we switch all passenger cars to electric, that is a drop in the bucket compared to planes.   So we do need to figure out a way to move towards electric, or at least clean fuel planes. Ships are another big one too.  A single container ship puts out more pollution in one day than a million cars in a year. (or something like that, I forget the stat)  Current battery tech is not good enough, perhaps we need to look at hydrogen, but I don't know if that is high density enough either.   But something needs to be figured out if we want to stop climate change.  It is already getting bad enough where it is affecting quality of life and it's only going to get worse, we've hit a point where the effects are exponential now.  Our ski and skidoo season here is much shorter now days.  Up north where they rely on ice roads, they have issues keeping those frozen as well. This affects shipments.   In the tundra regions, it is starting to melt, and causing issues with structures. Lots of other effects can be felt around the world.    Climate change is real and something needs to be done.

China and India are the two biggest polluters though, so even if we DO manage to switch to EVs - planes, ships, cars and all, it's STILL going to be a drop in the bucket if China and India continue to pollute at their current rates.

Also let's just assume here that if we do switch to electric planes, it means high scale energy storage has been figured out, so it would be safe to say the entire power grid would be all renewable too.  The idea of switching everything to electric still relies on the power grid using green energy.  Producing green energy is the easy part, we've been doing it for 100's of years.  It's storing it that is harder.

At the end of the day, I think we are royally screwed honestly.

[james_s]

Electric airliners are a non-starter, it's just never going to be practical without some kind of massive leap in battery technology. State of the art batteries are nowhere close to the energy density of hydrocarbon fuels and aircraft already struggle to carry enough of that fuel for long trips, fuel makes up a substantial fraction of the overall weight of the aircraft. I'm sure it has been mentioned already but a major advantage of liquid fuel is that the aircraft gets steadily lighter as fuel is consumed, something that does not happen with electric power. Passenger cars, trucks, buses, boats, ships, these are all reasonable candidates for electric power, large passenger aircraft are not. Various alternative fuels for aircraft could be practical, unlike passenger cars, planes flying between major airports don't need to be able to refuel at thousands of different locations dotted across the landscape so there is not the big infrastructure needed for personal cars. I don't think we'll be seeing anything meaningfully displacing kerosene as the fuel of choice to power large passenger planes any time soon though.

Regarding the efficiency of jet engines, they are most efficient near full rated power, and at high altitude, conditions that rarely exist at the same time for passenger aircraft. Turboprops are substantially more efficient, around 25% over turbofan engines, the disadvantage being they are slower. Even the old radial piston engines from the WWII era compare favorably to modern jets in terms of fuel efficiency however they are nowhere close in mechanical reliability or TBO. They sure do win in style and cool factor though IMHO, I'll take a seat on something like a Constellation or DC-6 over a 737 any day.

[james_s]

Thanks for all the replies, I'd used most of those arguments against this guy and he's just so convinced technology will get us there, And yes, someone came up with the nuclear battery, posted a link to some magazine or something that boasted this incredible energy density, but the prototypes were in the micro to milliwatt range

It sounds like you're engaged in a religious argument, in which case it is futile. He earnestly *believes* that he is correct and that it will happen, so no amount of facts, data or logic will convince him otherwise. One need not look further than the various threads on solar roadways, EVs, over-unity and other things or anywhere that allows political discussions to observe this phenomenon. You cannot win an argument with logic if your opponent's view is not built upon logic in the first place. You are arguing against their belief and you will never win, even when anyone who looks at it objectively will have to conclude that you are correct.

[james_s]

For the iPad maybe, but I ain't lugging a PC around with me just so I can use a dumb phone

Actually, before the iPhone that's pretty much what people wanted to do - have a PC in the pocket. Hence WinCE and all that followed, which was essentially a Windows desktop in a pocket. The iPhone showed that it wasn't the PC we wanted but the potential provided by a PC - the ability to do 'smart' things on the go, as opposed to taking a desktop simulacrum.

You might find that most people use their phones mostly for non-voice call things, and some have simply replaced the PC with a phone. Phones aren't really phones now - they are mobile computers which can make calls too. And, in fact, with a lot of IoT stuff you simply cannot use your computer with them - the phone is the only way to control or access them.

As such, I don't think the phone is duplicating much if you look at the detail rather than the superficial birds-eye view.

That is certainly true for me. The ability to make voice calls is a secondary feature of my phone. Most of the time I use it for text messages, as a still camera, as a camcorder, as a GPS navigator, as a portable music player, to check the weather, to check my email, to view my home security cameras, etc. It's not as good at any one of these tasks as a dedicated device but it's good enough and I always have it with me. Back in the pre-smartphone days I missed a lot of good photos for example because I didn't bring a camera with me. I got lost a few times and wished I had my GPS that I'd left at home. A smartphone is the Swiss army knife of technology, if I'm only going to carry one device with me that's the one I'm going to take. I still have more specialized dedicated devices that I can use when I know what I'm setting out to do.

[Rx7man]

Yup, i think concentrating on electric ships would be a far better testbed for major electric transport, container ships in particular.. they can just take however many  containers worth of batteries, all the infrastructure to load and unload is already there, you'd only need to change the drive systems and have a controller.. Sure, weight is an issue on ships too, but it's not a dealbreaker like on an aircraft

North america could certainly electrify a lot of the rail grid.. I mean Russia only did it something like 50 years ago

[mzzj]

Yup, i think concentrating on electric ships would be a far better testbed for major electric transport, container ships in particular.. they can just take however many  containers worth of batteries, all the infrastructure to load and unload is already there, you'd only need to change the drive systems and have a controller.. Sure, weight is an issue on ships too, but it's not a dealbreaker like on an aircraft

Lets start with big ships as they are most efficient: Maersk Triple-E class https://en.wikipedia.org/wiki/Triple_E-class_container_ship
35km/h,  Shanghai-Los Angeles 12 000km =342h  ( there is also lot longer shipping routes like china-europe past Cape Town but you have more potential locations to recharge)
2x 29 680kW engines = 10150560 kWh spent on Shanghai- Los Angeles.
10150 MWh Li-ion battery weights around 50 000 metric tons, about 25% of total DWT so kind of acceptable.
BUT: It would be 50% of Tesla Gigafactory 1 yearly production.. not to mention cost.

OK, big ships are obviously not the best use for batteries... Maybe short distance car ferries and cargo ships then. 

[NiHaoMike]

The first ships were wind powered. Why not make modern ships that are primarily wind powered with something like biofuel as a backup?

[sandalcandal]

The first ships were wind powered. Why not make modern ships that are primarily wind powered with something like biofuel as a backup?

Just a concept it seems but something that is being considered.
https://www.oceanbirdwallenius.com/

[tszaboo]

The first ships were wind powered. Why not make modern ships that are primarily wind powered with something like biofuel as a backup?

Their payload was also tiny, took them months to cross an ocean, and required a large number of sailors to maintain the ship. There are some experiments with the Magnus effect (witchcraft if you ask me) sailing ships. It might reduce the usage of a ship.
For cargo, WIG effect looks very interesting. It is a hybrid between hovercraft and aircraft, with small wings. If they can operate from shipyards, go a lot faster than ships, take more cargo than aircraft, and you dont need to build channels, because it works above solid ground just as well as water. Maybe if would be possible to operate these from batteries. But it is hard to say, as most of these WIG aircrafts were experimental. I dont think it would replace conventional ships, more like a cheaper alternative to cargo planes.

[james_s]

Well for big ships there is also the nuclear option, as far as I know it has only been done once for a civilian ship and was reasonably successful. A large number of military vessels are nuclear powered.

[Rx7man]

The first ships were wind powered. Why not make modern ships that are primarily wind powered with something like biofuel as a backup?

Well, for one, it takes a BIG crew to run those ships, in those times, there was no such things as OSHA, super dangerous job..

Here's an incredible video of a big sail ship going around Cape horn
https://youtu.be/9tuTKhqWZso

[james_s]

I don't think anyone is suggesting using replicas of 17th century sailing ships to carry cargo in modern times. I'm not sure how practical it would be, but I have little doubt that modern technology and materials could enable a large scale sailing ship that could be safely operated by a crew comparable to that on an oil powered ship. It's not unheard of for people to sail around in oceans solo on 30-60 foot sailboats, and hundreds of years ago any practical ocean going vessel would have required a substantial crew. Modern rigging and the availability of power assist for things like steering and winches, and electronic navigation equipment greatly reduce the need for large crews to handle the manual labor.

[Rx7man]

yes, but a big ship way back when (like the one I posted a link to in my last comment) was 8000 tons loaded, and was the biggest ship of its time (if you haven't, watch the vid, it's a treat!)
The Maersk ships are 55,000 tonnes EMPTY, fuel, cargo, crew, etc can add 210,000 more tonnes, so we're up to 265,000 tonnes fully loaded... there's a reason they're that size, because it's economical!

[PlainName]

I doubt it this one needs as many sailors to work - AIUI the sails are automatic.

[james_s]

The bigger the ship, the bigger the sails, the more force the wind exerts on them. The much greater weight is not really an issue, it's correspondingly larger. A 747 flies by the same physics as a Cessna. Again it may not be practical or cost effective, it's going to be much slower than a conventional ship but I see no technological reason why it couldn't be done.

[Rx7man]

that's the whole point, it has to be viable
No doubt we could build a plane 4x bigger than an A380 and make it fly, but few airports could take it and thus isn't viable.

I don't think the investment, crew requirements and capital costs of adding sails to a ship is going to be economical.. Would be more reasonable to have nuclear power, but that's not without problems either of course

[Clear as mud]

That first link someone posted to a modern cargo ship with sails, the Wallenius Oceanbird, says the ship takes 12 days to cross the Atlantic Ocean.  That seems to be comparable to a conventional cargo ship.

[Rx7man]

Is that the typical crossing time or the a pie in the sky figure if conditions are just great?  Also, it looks very difficult to load seeing it doesn't look like it takes containers, which is going to be a serious issue

[JohnG]

Unless I missed something in this thread, I don't see a lot of discussion on hybrid-electric turbofans.

I know that there has been a great deal of work on this from the engine side. The benefits are analogous to those for hybrid electric cars, except amplified because turbofans have a much smaller window of high efficiency in a relative sense compared to ICEs, and because you have a lot longer to recoup your investment versus automobiles. I have been out of the loop on this for the past few years, so I'm not sure what's happening these days.

John

[Rx7man]

Thunderfoot just made a video on Elon Musks supersonic jet idea
https://youtu.be/dMmaG_3NnGs

[james_s]

Unless I missed something in this thread, I don't see a lot of discussion on hybrid-electric turbofans.

I know that there has been a great deal of work on this from the engine side. The benefits are analogous to those for hybrid electric cars, except amplified because turbofans have a much smaller window of high efficiency in a relative sense compared to ICEs, and because you have a lot longer to recoup your investment versus automobiles. I have been out of the loop on this for the past few years, so I'm not sure what's happening these days.

John

Sounds like an interesting concept, although I'd be curious to see how the efficiency actually pans out. Perhaps having inboard turbine engines driving integrated alternators with residual thrust used to propel the plane and the electricity output used to power electric ducted fans. In theory the turbines could be run at full power where they are most efficient, and a battery bank could provide the extra power needed for takeoff and climbout.

I'd like to see more turboprops and unducted fans, turboprops are slower than jets but substantially more efficient, I think they look a lot cooler too but that isn't something most people care about. Propellers may be old fashioned but so are wheels and we still use those.