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  #31  
Old 12-14-2020, 11:32 AM
gasman gasman is offline
 
Join Date: Mar 2007
Location: Sonoma County
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Quote:
Originally Posted by molson309 View Post
Flying around with that much energy able to release in a short period of time (think either thermal runaway or catastrophic failure in a crash) gives me pause. Gasoline is energy dense, but it requires oxygen to release energy. Batteries do not...
Rarer than oxygen is the needed ignition source......................
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  #32  
Old 12-14-2020, 12:10 PM
gdrudolph gdrudolph is offline
 
Join Date: Jul 2019
Location: Mountain View, CA
Posts: 7
Default Electric airplanes are getting tantalizingly close to a commercial breakthrough

Click bait title for sure but some merit...

For $140,000, you can fly your own electric airplane. The Slovenian company Pipistrel sells the Alpha Electro, the first electric aircraft certified as airworthy by the Federal Aviation Administration (FAA) in 2018. Itís a welterweight at just 811 pounds (368 kilograms), powered by a 21 kWh battery packóabout one-fifth the power of what youíd find in a Tesla Model S. For about 90 minutes, the pilot training plane will keep you and a companion aloft without burning a drop of fossil fuel.


https://qz.com/1943592/electric-airp...ric%20aviation.
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  #33  
Old 12-14-2020, 12:42 PM
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Mike S Mike S is offline
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Join Date: Sep 2005
Location: Dayton Airpark, NV A34
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Default Classic case of NIMBY

Quote:
Originally Posted by gdrudolph View Post
without burning a drop of fossil fuel.
Other than at the power plant that generates the electricity to charge the battery.

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Mike Starkey
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Rv-10, N210LM.

Flying as of 12/4/2010

Phase 1 done, 2/4/2011

Sold after 240+ wonderful hours of flight.

"Flying the airplane is more important than radioing your plight to a person on the ground incapable of understanding or doing anything about it."

Last edited by Mike S : 12-14-2020 at 12:45 PM.
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  #34  
Old 12-14-2020, 12:48 PM
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bkervaski bkervaski is offline
 
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Location: Birmingham, Alabama
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Quote:
Originally Posted by Mike S View Post
Other than at the power plant that generates the electricity to charge the battery.
The big debate here is often misleading .. you do have to generate the electricity somehow, true, but the big difference is using the electricity is considerably more efficient than gasoline .. so in the case of electric cars you can get over 4x the driven miles on the same amount of fossil fuels .. or rather support 4-5 more cars on the road without increasing fossil fuel usage ..
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  #35  
Old 12-14-2020, 01:14 PM
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Raymo Raymo is offline
 
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There is a good article in the July 2019 Sport Aviation magazine (yes, I'm a little behind in my reading) called Electrified by the owner/builder of an electric Kit Fox. The engine is from an electric motorcycle with gear reduction and two sets of batteries (for CG purposes).
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RV-7A - Slider - N495KL - First flt 27 Jan 17
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  #36  
Old 12-14-2020, 01:36 PM
Freemasm Freemasm is online now
 
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Location: Orlando
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Quote:
Originally Posted by bkervaski View Post
The big debate here is often misleading .. you do have to generate the electricity somehow, true, but the big difference is using the electricity is considerably more efficient than gasoline .. so in the case of electric cars you can get over 4x the driven miles on the same amount of fossil fuels .. or rather support 4-5 more cars on the road without increasing fossil fuel usage ..
Big assumptions, here but this statement can't be validated. How was the electricity generated? No one can claim that answer with any certainty.

Fossil plant? Roughly the same amount of fuel would be used, before conversion and transmission losses. The "distributed" IC engine is an overall better use of resources.

Simple Cycle gas turbine? Close to the same, above.

Combined cycle plant? The electrical vehicle is easily a better use of resources for regarding aircraft but close to dead even for cars.

Wind or Solar? The economics are full of lies. If they were made to have a reliable supply, your associated electric bill would be more than your mortgage payment.

Hydro? Nothing can touch it's cost of generation if back-up resources are not included. Droughts do happen and reservoir levels do drop but it's at least predictable so the spot market stays flatter.

Electric vehicles including their related wattage sources are typically better regarding atmosphere pollution. Terrestrial pollution? Sorry but not really.

I can draw a box around anything to promote its merits as people who promote such do.

Would any of you VAF'ers like to invest in the new panocea known as the Hydrogen economy? There's a lot of people who would love to have your money.
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  #37  
Old 12-14-2020, 01:49 PM
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bkervaski bkervaski is offline
 
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Quote:
Originally Posted by Freemasm View Post
Big assumptions, here but this statement can't be validated. How was the electricity generated? No one can claim that answer with any certainty.

Fossil plant? Roughly the same amount of fuel would be used, before conversion and transmission losses. The "distributed" IC engine is an overall better use of resources.

Simple Cycle gas turbine? Close to the same, above.

Combined cycle plant? The electrical vehicle is easily a better use of resources for regarding aircraft but close to dead even for cars.

Wind or Solar? The economics are full of lies. If they were made to have a reliable supply, your associated electric bill would be more than your mortgage payment.

Hydro? Nothing can touch it's cost of generation if back-up resources are not included. Droughts do happen and reservoir levels do drop but it's at least predictable so the spot market stays flatter.

Electric vehicles including their related wattage sources are typically better regarding atmosphere pollution. Terrestrial pollution? Sorry but not really.

I can draw a box around anything to promote its merits as people who promote such do.
We have two Teslas and spend about $50/month fueling them instead of $250 for petro .. just sayin' .. but there's some solid research out there if you stay away from the crazies ..
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  #38  
Old 12-14-2020, 02:08 PM
Freemasm Freemasm is online now
 
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Quote:
Originally Posted by bkervaski View Post
We have two Teslas and spend about $50/month fueling them instead of $250 for petro .. just sayin' .. but there's some solid research out there if you stay away from the crazies ..
Don’t get me wrong. I’m a big fan of Tesla. That technology and related economics don’t translate to aviation.

As for your comparison, you are probably, indirectly burning natural gas in your Tesla by way of the power grid. The heating values of natural gas and gasoline are in the same ballpark. The relative economics come down to cost/BTU of fuel; natural gas versus gasoline. As you initially stated, it’s misleading.

Adding to my opinion here. I said I was a fan of Tesla. Going to add that I'm a fan of Musk as well. I can't think of anyone else that totally disrupted two major markets in a relatively short life; automotive and space launch. Opinion over.

Last edited by Freemasm : 12-14-2020 at 02:22 PM.
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  #39  
Old 12-14-2020, 02:56 PM
krwalsh krwalsh is offline
 
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Location: San Francisco, CA
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Default Not yet, for the mission you may want

Quote:
Originally Posted by c5company@aol.com View Post
I know there many very talented people on this forum. Someone must have thought of putting a Tesla motor, inverter, controller, and batteries in an RV.
Just the motor, for example weights only 70 lbs and puts out 362 hp. Although itís seems some of the numbers differ on the internet, they all are in the same ballpark. If Bye aircraft with their Eflyer 2 can fly for 3 1/2 hours , the Tesla setup
In an RV might be interesting?
Maybe someone has already suggested this, hope this isnít a repeat.
Thanks
Chuck
I worked as Sr Engineering Manager for Powertrain at Tesla's Fremont plant in charge of all of the automation to build Model S/X modules, packs, small drive (SDU), large drive (LDU), chargers, center consoles, etc. I also worked in Manufacturing Engineering at Alta Motors doing powertrain as well as main line assembly before they closed their doors. I have more than a casual understanding of cylindrical cell lithium batteries and high power-density electric motors.

The numbers you quoted above are not correct, or at least a little misleading. None of the Tesla motors (M S/X LDU, SDU, or 3DU) weigh 70 pounds. Just the rotor and stator casing, perhaps. But once you add the two stage reduction units, inverters, and other required bits, they weigh considerably more than twice that. Close to 3x, actually. More for the LDU.

It is important to understand that at highway speed the motor in a Tesla (and pretty much any EV) is spinning relatively quickly. The reduction ratio on a Tesla two-stage gearbox is between 8.2 and 9.3:1, depending on the model. So while you are cruising down the highway at 60 MPH and your wheels are spinning at roughly 730 RPM, your motor is closer to 6800 RPM. You would need to accommodate some level of gear reduction to adapt a motor spinning that fast to a propeller. Also, you should understand that while horsepower numbers are fun to throw around, for an EV you will basically never actually attain that maximum value. As stated previously, the torque curve is basically flat from zero RPM. That means you do not actually achieve the headline horsepower value until very high RPM. So while the acceleration of an EV is incredible because the torque is available from a standstill, you are not actually feeling horsepower.

Next, the highest range Tesla Model S can achieve 402 miles per 100kWh pack. That means at 60 mph you are averaging just under 15kW. That translates to 20 HP. I cannot imagine actually flying along at max L/D for very long to keep the energy consumption down to a number close to that. Any increase in power is met with a proportional decrease in duration. In fact, the slope is worse than that because 18650 cells have lower total capacity ratings when you increase the C-rating discharge. Add to that that the power required to go faster on that side of the curve goes roughly cubically with airspeed. Things are getting worse very fast in terms of cruise speed and range now.

Next we can consider the mass of the battery. A single 18650 weighs right around 50grams. In a Tesla 100kWh pack you have 16*6*88 cells, or 8448 18650s, for just a cell mass of 930 pounds. On top of this you need the high current bus bars, wiring, cooling channels as associated fluid, pumps, etc. You have to have enough structure for the cells to not be compromised during G loads, as well as valves to deal with "thermal events" should your day go very, very poorly. You would be very lucky to get away with a final pack weight of 1000 pounds. Of course, you can reduce pack mass by reducing cells, which again increases the per-cell C-rate for a given load, so now you're back to trading mass for duration, and again you find yourself on the back side of the curve there.

At Alta we got away with significant weight savings by eliminating the fluid cooling system for the pack and using other thermal management techniques. This was to the detriment of overall cell lifespan, but for the use case of a high performance dirt bike, it was worth the tradeoff. We had a pack that was nominally 6kWh, and a motor capable of 40kW (53HP). Our pack alone was right around 65 pounds. But very few riders would pin the throttle and leave it there until the pack was empty, and we had thermal limiting to manage that if they tried.

This is not to say that electric aircraft are not happening. They are. The eVTOL category is full of vehicles that actually fly using these same technologies. They do so by managing the overall power profile over the duration of the flight very carefully, flying at max L/D for cruise at speeds that are in the neighborhood of 100mph, and have a total range of something less than 100 miles.

So, I think what you are asking for is going to happen sooner rather than later. But I do not think we are to a point where swapping powertrains on an E-AB and expecting Lycoming/Continental cruise speed and range is a thing.
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  #40  
Old 12-14-2020, 03:15 PM
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Mike S Mike S is offline
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Kevin, thank you.
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Rv-10, N210LM.

Flying as of 12/4/2010

Phase 1 done, 2/4/2011

Sold after 240+ wonderful hours of flight.

"Flying the airplane is more important than radioing your plight to a person on the ground incapable of understanding or doing anything about it."
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