Electric Hybrid

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Vigilant1

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The first thing you need to ask yourself is what the aim of the electric planes is? The obvious answer is greenhouse emissions reduction.
I think you are on to something here, but the approach still jumps ahead a few questions too far. I'd say the first questions are:
- Is increased atmospheric CO2 a problem worth addressing? If so:
- How do we address it in the most efficient way (best total CO2 reduction per increased cost inflicted?)

I'll skip question number one. To question number 2, I'd bet we can reduce CO2 a lot more efficiently in other ways rather than electrifying flying machines. They are an application where liquid fuels are particularly appropriate. Given that, your idea of making those liquid fuels in a more "carbon conscious" way appears to be attractive. But, we still need to not get ahead of ourselves, as it could be that biofuels etc don't give us the bang for the buck we'd get from, say, reducing CO2 emissions from fixed sites, reducing other greenhouse gasses, etc. The "do everything" approach isn't the best one.
 

John.Roo

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At US$100 per kW/h, the 21 kW battery pack in the electric Pipistrel is $21,000. I think a new Rotax 912 is no more than that. What is the life of that battery pack, in terms of hours flown?

That Pipistrel has a 60 kW/h motor in it. The 21 kW/h battery therefore will drive it for 20 minutes at full power. WE have a LONG way to go.
Seems like small misunderstanding....
If we go down to price of automotive battery (100 USD / 1 kWh) than we will pay for 21 kWh 2 100 USD. And that would be really cheaper than Rotax 912 :)

And... yes, you are right - flying with electric airplanes is really different.
I did a lot of flight tests with electric airplanes so I can say for sure that electric propulsion is different from what you know about flying with ICE. And honestly... I was always very glad for experience with sailplanes "Energy management" is really important :)

I thing that Malovanny pointed perfectly the main question....
The first thing you need to ask yourself is what the aim of the electric planes is?
What I tried to explain was that electric airplanes have many limitations, but is not necessary to wait for "super high end capacity batteries". There are already pilots and clubs able to use actual generation of electric airplanes even with limitations.
 

Dan Thomas

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Seems like small misunderstanding....
If we go down to price of automotive battery (100 USD / 1 kWh) than we will pay for 21 kWh 2 100 USD. And that would be really cheaper than Rotax 912 :)
"Small misunderstanding??" I was off by a factor of ten. That's not small. I must have done that after only half a cup of coffee.

Thanks for pointing that out. I'm still trying to believe that a 21 KW battery pack would only be $2100. Sounds fishy. Although, for 20 minutes at full power, maybe that's all you get for $2100.
 

Dan Thomas

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I think you are on to something here, but the approach still jumps ahead a few questions too far. I'd say the first questions are:
- Is increased atmospheric CO2 a problem worth addressing? If so:
- How do we address it in the most efficient way (best total CO2 reduction per increased cost inflicted?)

I'll skip question number one. To question number 2, I'd bet we can reduce CO2 a lot more efficiently in other ways rather than electrifying flying machines. They are an application where liquid fuels are particularly appropriate. Given that, your idea of making those liquid fuels in a more "carbon conscious" way appears to be attractive. But, we still need to not get ahead of ourselves, as it could be that biofuels etc don't give us the bang for the buck we'd get from, say, reducing CO2 emissions from fixed sites, reducing other greenhouse gasses, etc. The "do everything" approach isn't the best one.
Especially considering that much electricity comes from coal-fired generating plants, and is likely to do so for some time unless we're willing to go without electricity fairly often once we rely heavily on alternative sources.
 

Dan Thomas

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The first thing you need to ask yourself is what the aim of the electric planes is? The obvious answer is greenhouse emissions reduction. The whole movement with electric planes just went from that statement and the good experience with electrification of cars and started to investigate how we can make it work in planes. The better approach is too look how we can most efficiently reduce the net worldwide emissions, not how we can electrify planes. We can of course remove 2/3 of seats in a b737 and fill it with batteries and there you go - you have a “full size” electric regional commuter. The net greenhouse emissions per person and km would be probably even higher than for an ordinary turboprop. The battery production causes also greenhouse emission and installing more batteries to be able to lift those batteries in the air is not really a solution. 1 kWh of batteries makes a largest reduction of emissions when the transport of that batteries can be done efficiently and when the degradation is low. Take a sea transport as an example. It uses the dirtiest fuel but operates 24/7. The sea transport is the most efficient way to carry “heavy stuff”.
For airplanes the real realistic way forward in near future is renewable chemical fuel, like biodiesel used in piston and turbine engines. Good emission reduction and no need to rebuild the infrastructure or wait for the batteries to improve.
I did some numbers on that. Removing the fuel and 2/3 of the passengers from a 737-300 or -400 would free up 49,000 pounds, plus maybe another 3000 for seats and so on. At the typical 1/60 energy density of batteries per pound compared to jet fuel, I get an allowable battery of 9803 KW, or about 13,000 horsepower for one hour. The 737's engines are around 22.000 pounds thrust, which translates, at 650 MPH to 38.000 per engine, or 76,000 HP total, or close to 57,000 KW. That battery would fly the airplane for less than 15 minutes. And you still need energy for taxiing, flight reserve to an alternate, heating/air conditioning and pressurization.

My numbers might be off some, but even if I'm off by a factor of ten, it explains why we don't see any electric airliners yet.
 

Vigilant1

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The wholesale price of bulk city bus batteries in China may not be especially relevant to the question at hand. At present, Tesla apparently charges $13,500 US for a 75 kwh replacement battery (so, $180 per kwh, nearly double the price of bus batteries in China). At that rate, the Pipistrel's 21 kwh battery would cost about $3800. But it doesn't, it costs over $21k. Why? Because it is going into an airplane? Because it is a low-rate production application? Because it has a super-duper BMS? Because it is a different battery technology more appropriate to acft use? Because that's the price that optimizes Pipistrel's profit at the volume they want to produce? I dunno.

A new small block Chevy crate engine costs about $14 per HP. They are mass produced commodities. Should we ever expect that a new 100 HP airplane internal combustion engine will be priced at $1400? No. The same principle apparently applies to battery packs.
ETA: If we could get to the point where battery packs or sub-units of them (higher than the cell level) are truly standardized and commodity items (common battery chemistry, common configuration, common connectors, common BMS interface, etc) and if these were suitable for use in aircraft, then maybe prices for airplane EV would come down a lot. Battery technology is changing too fast to allow this now, and the present incentives don't encourage it. That could change.
 
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emotodude

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At US$100 per kW/h, the 21 kW battery pack in the electric Pipistrel is $21,000. I think a new Rotax 912 is no more than that. What is the life of that battery pack, in terms of hours flown?

That Pipistrel has a 60 kW/h motor in it. The 21 kW/h battery therefore will drive it for 20 minutes at full power. WE have a LONG way to go.
Correction, @ $100/kWh a 21kWh pack is $2100. You were just off by 10x.

The batteries I use are good for over 1000 cycles. This means amortized cost is 2-3$/hr. A lot less per flight than your original estimate ($30/hr).

Additionally, the use of renewables is dramatically increasing, many countries are over 50% renewables already.

Does that change your perspective?

 

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Vigilant1

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Additionally, the use of renewables is dramatically increasing, many countries are over 50% renewables already.

Does that change your perspective?
In the EU, renewables account for about 34% of electric production. In the US it is about 17%. Also, in the EU electricity costs consumers more than twice as much as American consumers pay. I'll leave it to others to determine which way the renewables <---> high price "arrow of causation" should point, I'll just offer that the 25 cents per KWH club is not a club I want to join. Either way, it has very little to do with the practicality of aircraft electric propulsion.
 
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emotodude

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In the EU, renewables account for about 34% of electric production. In the US it is about 17%. Also, in the EU electricity costs consumers more than twice as much as American consumers pay. I'll leave it to others to determine which way the renewables <---> high price "arrow of causation" should point, I'll just offer that the 25 cents per KWH club is not a club I want to join. Either way, it has very little to do with the practicality of aircraft electric propulsion.
agreed the price of electricity is so low it has essentially no impact on the cost of my flying. I use 6-8kWh avg per flight so even at .25/kWh it's only 1.50-2.00 $/hr. My EV rate for car charging is like ~$.10/kWh which reduces the cost to under $1/hr of flight... And that's assuming I have to pay for it, which I don't, comes for free with the hangar...
 

John.Roo

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"Small misunderstanding??" I was off by a factor of ten. That's not small. I must have done that after only half a cup of coffee.

Thanks for pointing that out. I'm still trying to believe that a 21 KW battery pack would only be $2100. Sounds fishy. Although, for 20 minutes at full power, maybe that's all you get for $2100.
That is OK - it was discussion only about possible price, not calculation of wing main spare ;)

My friend is now building small electric aerobatic one seater - he expect to have enough energy for 10 minutes of training.
Normally he is flying with Jak 52 :cool:
Now he is testing cells, looking for affordable propulsion system etc. Really good job.

By the way... another info about electric motors.
For example Pipistrel has 60 kW for TakeOff, but he cannot use 60 kW for more than few minutes due to motor overheating. So most of time is electric Velis flying at 17-20 kW of cruise power.
I have +-similar experience - on Phoenix I have 60 kW for TakeOff but 30 kW max. cont. power.
So in fact you really cannot discharge battery in 20 minutes.... ;)
 

John.Roo

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That is OK - it was discussion only about possible price, not calculation of wing main spare ;)

My friend is now building small electric aerobatic one seater - he expect to have enough energy for 10 minutes of training.
Normally he is flying with Jak 52 :cool:
Now he is testing cells, looking for affordable propulsion system etc. Really good job.

By the way... another info about electric motors.
For example Pipistrel has 60 kW for TakeOff, but he cannot use 60 kW for more than few minutes due to motor overheating. So most of time is electric Velis flying at 17-20 kW of cruise power.
I have +-similar experience - on Phoenix I have 60 kW for TakeOff but 30 kW max. cont. power.
So in fact you really cannot discharge battery in 20 minutes.... ;)
The info about max. cont. power of electric motor (usually much lower than max. power you can find in specification) is not mentionned because is some "advantage". It shows that you have to be really carefull when looking for electric propulsion system for your project. Pilot flying with Rotax expects to have 5 min. of max. power. Well... in case of electric propulsion you can have only 60-90 sec. of max. power. All this means you need detailed training on electric airplane to understand the difference between ICE and electric propulsion - for your own safety.
 

Speedboat100

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I can see only 2 things where electric hybrid could be advanced.

1. You can have more functional and aerodynamically sound vehicles.

2. You could also use solar energy as range extender.
 

Malovanyy

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But, we still need to not get ahead of ourselves, as it could be that biofuels etc don't give us the bang for the buck we'd get from, say, reducing CO2 emissions from fixed sites, reducing other greenhouse gasses, etc. The "do everything" approach isn't the best one.
Even though I agree with you that there might be better ways to decrease the emissions, it is not that easy to just blame the other polluters and do nothing in the aviation. Every area should take its own responsibility and try to decrease the emissions. There are really no low hanging fruits that could decrease the emissions to the needed level. The concept of implementing the measures based on cost effectiveness is good but why should a power plant or industry take 100% of costs and aviation do nothing? The solution to this is to implement the CO2 tax on everything which will lead to the market implementing those solutions that are most cost-efficient. But I guess a 50$ CO2 tax on a kilo of beef will not be super popular in any country.
 

Speedboat100

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Even though I agree with you that there might be better ways to decrease the emissions, it is not that easy to just blame the other polluters and do nothing in the aviation. Every area should take its own responsibility and try to decrease the emissions. There are really no low hanging fruits that could decrease the emissions to the needed level. The concept of implementing the measures based on cost effectiveness is good but why should a power plant or industry take 100% of costs and aviation do nothing? The solution to this is to implement the CO2 tax on everything which will lead to the market implementing those solutions that are most cost-efficient. But I guess a 50$ CO2 tax on a kilo of beef will not be super popular in any country.

Emissions actually have decreased a lot...but there are new players with high income.

co2-predict-china-us-row-fm-gdp-s_7.jpg
 

Aesquire

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As long as batteries that are light AND energy dense use rare elements like Cobalt or Unobtanium, mined only in a few politically unstable places, the price cannot fall very far as demand increases. And the demand for aviation is a tiny fraction of the whole. The new miracle battery "only 5 years away" ( for a few decades now ) that uses cheap elements and clever configurations is coming... Eventually.

Yes, you can argue that fossil fuels also have the problem of being produced in politically unstable places, but it already has the proven energy density to work in today's airplanes.

We are in a transition period much like over a century ago. Short flights with heavy low powered engines in the cutting edge.
 

EzyBuildWing

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Emrax 228 puts out maximum 109 kW and weighs 12 kg.
That's about 140 HP for say a 15 second "ludicrous take-off", then back off to say 25 HP for a leisurely cruise around the circuit followed by a leisurely "regenerative-glide" back down to the strip!
Lockwood Aircam has 2 pusher props, so we've got maybe 1000 lbs total thrust for an accelerating near-vertical climb-out!
For thrills, this would beat any roller-coaster on the Planet, and would win all the STOL competitions hands-down!
We need an electric "Mega-sizzle" plane!
Vid below shows how long it took for Jay Leno to decide to buy the "sizzle" that comes with the new Tesla Roadster:
 
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