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Just_a_fan wrote: ↑

23 Oct 2019, 09:58

Andres125sx wrote: ↑

23 Oct 2019, 07:45

mzso wrote: ↑

22 Oct 2019, 23:29

Electricity, renewable or not doesn't magically appear in batteries. It's costly.

True. Do you say the same about combustion aircrafts? Because they need several orders of magnitude more energy as ICE are not even a half efficient compared to electric motors

Electric aircraft face the same issue that electric cars face - energy density. Electric motors may be more efficient than combustion engines, but the energy density of oil-derived fuels is so high that batteries can't compete. Jet fuel is 43MJ/kg compared to batteries that are mostly significantly less than 1 MJ/kg.

If an aircraft requires 100 tonnes of jet fuel to fly three hundred people over several thousand miles, even with the efficiency savings of an electric motor over a high-bypass turbofan, you're going to need more than 100 tonnes of batteries. Indeed, you're going to need several hundred tonnes of batteries. And then your aircraft won't fly because it'll be too heavy.

If/when batteries can give 30+MJ/kg energy density, then electric aircraft for commercial use will be possible. Until then? Nope, not going to happen.

Sorry but you're missing the key point of the discussion, Alair batteries are around 6MJ/kg which changes the whole scenario. Nobody talked about airliners, no electric setup can replace a turbine tough. But for prop planes it may be possible, and specially for personal multirotors. They would obviously be very expensive, but as any new technology is. ICE cars also were a luxury when first released.

The main point IMO is with this new batteries now they're feasible, and that's a huge step forward

AJI wrote: ↑

23 Oct 2019, 10:41

Just_a_fan wrote: ↑

23 Oct 2019, 10:29

AJI wrote: ↑

23 Oct 2019, 10:11

Agreed. A throw away battery for daily use is ridiculous, even if you get 10,000ks per battery, which they don't, but I'm failing to see the downside in a motorsport application.

If Formula E is trying to be "green", throwing away batteries after a single use is going against the message, wouldn't you say?

Ever heard of recycling? How "green" is shipping a power station to every event?

Recycling is fine but rechargeable is better, surely. As for shipping a power supply system to each race, yes that is a bit drastic but presumably is a result of the locations they race in.

Andres125sx wrote: ↑

23 Oct 2019, 11:33

Just_a_fan wrote: ↑

23 Oct 2019, 09:58

Andres125sx wrote: ↑

23 Oct 2019, 07:45

True. Do you say the same about combustion aircrafts? Because they need several orders of magnitude more energy as ICE are not even a half efficient compared to electric motors

Electric aircraft face the same issue that electric cars face - energy density. Electric motors may be more efficient than combustion engines, but the energy density of oil-derived fuels is so high that batteries can't compete. Jet fuel is 43MJ/kg compared to batteries that are mostly significantly less than 1 MJ/kg.

If an aircraft requires 100 tonnes of jet fuel to fly three hundred people over several thousand miles, even with the efficiency savings of an electric motor over a high-bypass turbofan, you're going to need more than 100 tonnes of batteries. Indeed, you're going to need several hundred tonnes of batteries. And then your aircraft won't fly because it'll be too heavy.

If/when batteries can give 30+MJ/kg energy density, then electric aircraft for commercial use will be possible. Until then? Nope, not going to happen.

Sorry but you're missing the key point of the discussion, Alair batteries are around 6MJ/kg which changes the whole scenario. Nobody talked about airliners, no electric setup can replace a turbine tough. But for prop planes it may be possible, and specially for personal multirotors. They would obviously be very expensive, but as any new technology is. ICE cars also were a luxury when first released.

The main point IMO is with this new batteries now they're feasible, and that's a huge step forward

6MJ/kg compared to 43MJ/kg does not make them feasible. You're still talking about 7 times the mass of batteries compared to fuel for a given trip. So a 10 tonne fuel requirement becomes a 70 tonne battery requirement. Are electric motors 7 times as efficient as modern turbofans / turboprops? I'm betting no where near - if they were, we'd be using them already.

Remember also one big "advantage" of fuel over batteries in aircraft - as the flight goes on, the mass reduces. This means that the aircraft becomes more efficient the further it flies - you need less lift to hold the aircraft up so you can trim it for a lower angle of attack / lower drag or fly higher which gives reduced drag (and so more efficiency). The battery-powered aircraft will be the same mass at the end of the flight as at the beginning and so doesn't benefit from this lowering of drag as the flight progresses.

Then there is the very big issue that aircraft can take off at weights higher than they can land. A battery aircraft will land at the same weight that is takes off. So you're limited to the maximum weight that the landing gear etc. can handle - more weight then being needed to make stronger landing gear to land a heavier aircraft.

I think we're stuck with fuelled aircraft for the foreseeable future. Better to develop carbon-neutral, low pollutant fuels to reduce the impact of aircraft.

Sure, there are limited cases where an electric aircraft is practical but they're limited to things like high altitude sensor platforms for the military i.e. relatively small, no need to fit in people and keep them alive etc. so can be built for aero efficiency above all else. They're going to be a very high aspect ratio winged, powered gliders, in effect.

Just_a_fan wrote: ↑

23 Oct 2019, 12:17

AJI wrote: ↑

23 Oct 2019, 10:41

Just_a_fan wrote: ↑

23 Oct 2019, 10:29

If Formula E is trying to be "green", throwing away batteries after a single use is going against the message, wouldn't you say?

Ever heard of recycling? How "green" is shipping a power station to every event?

Recycling is fine but rechargeable is better, surely. As for shipping a power supply system to each race, yes that is a bit drastic but presumably is a result of the locations they race in.

Sure, recharge is the better option if you can do it. However, it seems there isn't enough grid infrastructure at any of the race locations to be able to charge all of the cars..? I was surprised initially, but I guess it makes sense.
They have a better chance of charging from the grid in major city than at a track, but right now no venue can support the power requirements so they bring it with them. At least that's my understanding of the situation, happy to be proven wrong

AJI wrote: ↑

23 Oct 2019, 12:40

At least that's my understanding of the situation, happy to be proven wrong

That sounds a reasonable understanding. Taking fully charged batteries from the factory would seem to be more sensible than taking large generating sets to each race.

Just_a_fan wrote: ↑

23 Oct 2019, 12:31

6MJ/kg compared to 43MJ/kg does not make them feasible.

Feasibility does not depend on matching same energy density as fuel

Just_a_fan wrote: ↑

23 Oct 2019, 12:31

You're still talking about 7 times the mass of batteries compared to fuel for a given trip. So a 10 tonne fuel requirement becomes a 70 tonne battery requirement. Are electric motors 7 times as efficient as modern turbofans / turboprops? I'm betting no where near - if they were, we'd be using them already.

Not 7 times but yes they are more efficient so real requirement will be much lower

We're not using them already because AlAir batteries are new, not even released yet

And you keep comparing with turbofans and turboprops when that's not reasonable, as I said no electric setup can replace those, I was talking about piston engines

Just_a_fan wrote: ↑

23 Oct 2019, 12:31

Remember also one big "advantage" of fuel over batteries in aircraft - as the flight goes on, the mass reduces. This means that the aircraft becomes more efficient the further it flies - you need less lift to hold the aircraft up so you can trim it for a lower angle of attack / lower drag or fly higher which gives reduced drag (and so more efficiency). The battery-powered aircraft will be the same mass at the end of the flight as at the beginning and so doesn't benefit from this lowering of drag as the flight progresses.

True, good point

Just_a_fan wrote: ↑

23 Oct 2019, 12:31

I think we're stuck with fuelled aircraft for the foreseeable future. Better to develop carbon-neutral, low pollutant fuels to reduce the impact of aircraft.

Sure, there are limited cases where an electric aircraft is practical but they're limited to things like high altitude sensor platforms for the military i.e. relatively small, no need to fit in people and keep them alive etc. so can be built for aero efficiency above all else. They're going to be a very high aspect ratio winged, powered gliders, in effect.

Agree with this too, but at least now there's an option for electric aircrafts which was not possible before

Andres125sx wrote: ↑

24 Oct 2019, 11:53

We're not using them already because AlAir batteries are new, not even released yet

And you keep comparing with turbofans and turboprops when that's not reasonable, as I said no electric setup can replace those, I was talking about piston engines

Aren't the AlAir batteries non-rechargeable? No one is going to use them for anything other than maybe a long life torch.

Another article here

https://cafe.foundation/blog/the-17x-al ... r-battery/

Just_a_fan wrote: ↑

24 Oct 2019, 14:36

Andres125sx wrote: ↑

24 Oct 2019, 11:53

We're not using them already because AlAir batteries are new, not even released yet

And you keep comparing with turbofans and turboprops when that's not reasonable, as I said no electric setup can replace those, I was talking about piston engines

Aren't the AlAir batteries non-rechargeable? No one is going to use them for anything other than maybe a long life torch.

Bold statement

Price will be the decisive factor, and for some aplicaions like FE or personal drones (only for wealth people) not even that

Andres125sx wrote: ↑

25 Oct 2019, 07:55

Just_a_fan wrote: ↑

24 Oct 2019, 14:36

Andres125sx wrote: ↑

24 Oct 2019, 11:53

We're not using them already because AlAir batteries are new, not even released yet

And you keep comparing with turbofans and turboprops when that's not reasonable, as I said no electric setup can replace those, I was talking about piston engines

Aren't the AlAir batteries non-rechargeable? No one is going to use them for anything other than maybe a long life torch.

Bold statement

Price will be the decisive factor, and for some aplicaions like FE or personal drones (only for wealth people) not even that

Personal drones? You were talking about piston engined aircraft previously. Big difference between an aircraft and a drone.

But even with a drone, why would someone use expensive disposable batteries when cheap rechargeable ones work perfectly well?

Just_a_fan wrote: ↑

25 Oct 2019, 09:10

...
But even with a drone, why would someone use expensive disposable batteries when cheap rechargeable ones work perfectly well?

Range/flight time, in military or emergency applications?

So what does get replaced? only the aluminum or everything?

FW17 wrote: ↑

25 Oct 2019, 09:57

So what does get replaced? only the aluminum or everything?

I believe just the aluminium and the electrolyte

AJI wrote: ↑

25 Oct 2019, 10:19

FW17 wrote: ↑

25 Oct 2019, 09:57

So what does get replaced? only the aluminum or everything?

I believe just the aluminium and the electrolyte

Electrolyte is water?

Just_a_fan wrote: ↑

25 Oct 2019, 09:10

Andres125sx wrote: ↑

25 Oct 2019, 07:55

Just_a_fan wrote: ↑

24 Oct 2019, 14:36

Aren't the AlAir batteries non-rechargeable? No one is going to use them for anything other than maybe a long life torch.

Bold statement

Price will be the decisive factor, and for some aplicaions like FE or personal drones (only for wealth people) not even that

Personal drones? You were talking about piston engined aircraft previously. Big difference between an aircraft and a drone.

But even with a drone, why would someone use expensive disposable batteries when cheap rechargeable ones work perfectly well?

Sorry I meant personal multirotors

Andres125sx wrote: ↑

07 Oct 2019, 21:47

When that arrives, everything will change, not only the automotive industry, for example all these will become viable:
https://www.youtube.com/watch?v=VMBBLuusW0g
https://www.youtube.com/watch?v=WsKpva914PY

Btw, not sure what you mean with cheap rechargable batteries, as current LiIon are expensive and heavy for aircrafts use.

AlAir looks like far from perfect, but with an energy density around 6 times higher to current LiIon there will surely be applications where they will make a difference, and aircraft use is the most obvious, both to replace piston engines or to make possible aircrafts which didn't exist before