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27 Sep 2021, 02:27 [ UTC - 5; DST ]


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 Post subject: Re: Bye Aerospace eFlyer 800
PostPosted: 28 Apr 2021, 10:22 
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Username Protected wrote:
1000 KWH pack to recharge in 2 hours will take 600 KW service to the charger.

This may need a new line on the poles to the airport. Will definitely need a new transformer, one that probably produces 960 volt service.

Look at Tesla supercharger stations. The standard ones right now are capable to deliver 2MW (8 250kW stalls), and they are popping up left and right like crazy. And with battery storage on site they can lower the peak demand from the grid if they need to.

Charging is not a technical challenge anymore. It's just time and money factor.


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 Post subject: Re: Bye Aerospace eFlyer 800
PostPosted: 28 Apr 2021, 10:55 
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Location: The Woodlands, Tx. (KDWH)
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I love this stuff but nobody understands the numbers! Mike C does but still did not communicate the “challenge” very well- :duck: - what the heck is a MW / KJ / and KG anyway.

Inconvenient fact number one - Hydrocarbons have 100 x energy density of current battery technology - you are splitting chemical bonds and releasing energy vs unstacking electrons in storage boxes (ok that is gross oversimplification but stay with me). Electric motors are more efficient than ICE’s but the you still have a lot of space to make up. 90% vs 15% is tossed around a lot - still gives a 20X advantage to hydrocarbons. Note these numbers are optimized for electric - ideal temperature and discharge versus worst case for hydrocarbons.

Here is how I look at it - and I like battery cars.

A Tesla Model 3 battery weighs 1080 pounds and has a range of 350 miles - pretty dang good. Should be easy to do the conversions to airplanes. Challenge is that 1080 pounds of batteries gets you 82 KW Hrs OR (wait for it) 110 HP hrs and costs around $12,000. A Tesla can go 350 miles because it is using about 20 hp to maintain 60 mph. Those crazy acceleration numbers will get you about 30 minutes.

Easy numbers to remember batteries at current technology - 1 lb of battery = .1 hp / hr or 10 pounds of batteries to get 1 hp for 1 hour. I am a simple old engineer and pounds, hp and $ fit the equivalent scales in my failing brain better. Oh and $100 per HP hr cost today

For those of you who haven’t nodded off...

1 gallon (six pounds) of avgas gives a theoretical 187 hp hrs of energy. Go ahead and scale it down with the 15% efficiency number and you have 21 hp / gallon effective power - you can quibble with the numbers but it is close. (LOP rule of thumb is 14.9) (YMMV)

1080 pounds of avgas / 180 gallons will give you a real world energy yield of 3780 hp hrs - about 33 times the battery yield. Equivalent Tesla battery weight is about 35,000 pounds. Replace engines with batteries and motors in your baron and no range / no payload / no fun?

Bottom line - electric cars can obviously work though still lots of issues. The very low cruise consumption of a car makes the comparison / translation nonsensical. As Mike C mentioned as well - add in everything you have to do in an airplane - heating, deicing, air conditioning, pressurization, running avionics .... and do that on battery power vs hydrocarbon generation and it becomes a non starter for the foreseeable future. Also, the voltage required to give efficiency and reasonable charging is pretty intimidating.

Ok - back to the real world.

Maybe I am missing something - always ready to learn.

S


Last edited on 28 Apr 2021, 11:33, edited 1 time in total.

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 Post subject: Re: Bye Aerospace eFlyer 800
PostPosted: 28 Apr 2021, 10:59 
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Username Protected wrote:
Sulphur is probably the most abundant material on earth, so should provide for cheaper chemistry.


16th, probably according to wikipedia

https://en.wikipedia.org/wiki/Abundance ... %27s_crust


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 Post subject: Re: Bye Aerospace eFlyer 800
PostPosted: 28 Apr 2021, 11:22 
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Username Protected wrote:
I think they said they're looking at the Li-Sulphur technology which has a capacity of up to 500wh/kg. Problem I've heard with those batteries is that they don't have as many cycles in them as Li-Ion and will need replacing. On the other hand, Sulphur is probably the most abundant material on earth, so should provide for cheaper chemistry.

Exciting times ahead. I personally can't wait to get rid of the monkey motion stuff.


Still a long way from the goal - 500 wh/kg = .31 hp/lb

Avgas (Beechtalk LOP calc) is 2.48 hp/lb. That is efficiency adjusted - theoretical is 31.2 hp/lb but looks like 40% is reaching limit.

Even with a huge future and theoretical increase in battery efficiency, the delta is still 8x - convert that either to weight or shorter range.

Point again - there may be a place for electric in aviation in the future, but it is not going to look like our planes of today.

Another key point to remember - in cars - much more efficient engines than airplanes - they are replacing 90 pounds of gasoline with 1000 pounds plus of batteries for the same range and performance.

I still maintain the numbers won’t work for airplanes. I do believe a lot of people will make a lot of money on research and grants though.


Last edited on 28 Apr 2021, 11:44, edited 2 times in total.

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 Post subject: Re: Bye Aerospace eFlyer 800
PostPosted: 28 Apr 2021, 11:24 
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I was wondering when this topic would come up on Beechtalk. Avweb, AOPA, and Flying have reported this in the same manner that they would a press release from Textron or Gulfstream. The difference of course is that if Textron or Gulfstream announce a new plane, they will have a conforming prototype flying in a couple of years and they will be able to manufacture that plane (if they still think that it will make money).

There is a lot of wishful thinking, or maybe flip-flam, in these "news" articles. Keep in mind that battery electrochemistry hasn't really changed in the better part of a century. (I worked on developing lithium/polypyrrole batteries almost 40 years ago). What has changed is the packaging of the anodes and cathodes to make the chemicals more available, the inhibitors to suppress parasitic reactions, improved separators, electrolytes, etc., etc. Additionally, charge management circuitry has helped dramatically in limiting parasitic reactions. Amazing technology to be sure, but improvements for any given battery chemistry is going to follow a logarithmic curve not exponential (there is no Moore's law for chemistry). Changing chemistry changes the equation to some extent, but only as far as the reaction allows. Lithium Sulfur batteries for example have the prime benefits in that there are two lithium atoms for each sulfur atom which theoretically doubles charge capacity, but there are a lot of issues including a lot of parasitic reactions going on (limiting recharge cycles and capacity after recharging), the cathodes shrink and swell dramatically through the charge discharge cycles, etc. The Wikipedia article on Li/S batteries provides a fair treatment of the issues. Even if the problems are overcome, we're talking double the capacity, not orders of magnitude higher.

Hydrogen has been brought up as well. Some people think that hydrogen is an energy source, however it is not - it is a battery. The hydrogen molecule does not exist in nature, and has to be produced either chemically (producing lots of byproducts including CO2 in the most common method of creating hydrogen) or electrolytically (requiring a lot of energy). Of course it is our lightest element and on a weight basis a hydrogen oxygen fuel cell is very efficient. The problem is stuffing enough of those H2 molecules into the plane. Additionally, fuel cells for turning the H2 into H2O and for harvesting the electrons are not cheap. You could burn the H2 in a standard engine, but you are then taking the efficiency down from maybe 80+% down to Carnot cycle efficiency levels.

The bottom line is that we should believe it when we see it, and then add quite a few years for "it" to actually work.


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 Post subject: Re: Bye Aerospace eFlyer 800
PostPosted: 28 Apr 2021, 11:32 
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I yield my “packing electrons in a box” explanation to Phil!!

Did not understand all of it but it sounded very impressive.

I was a chemical engineer and we referred to anything electrical or electronic as sparks and magic - still do.

:eek:


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 Post subject: Re: Bye Aerospace eFlyer 800
PostPosted: 28 Apr 2021, 12:24 
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Username Protected wrote:

Still a long way from the goal - 500 wh/kg = .31 hp/lb

Avgas (Beechtalk LOP calc) is 2.48 hp/lb. That is efficiency adjusted - theoretical is 31.2 hp/lb but looks like 40% is reaching limit.

Even with a huge future and theoretical increase in battery efficiency, the delta is still 8x - convert that either to weight or shorter range.

Point again - there may be a place for electric in aviation in the future, but it is not going to look like our planes of today.

Another key point to remember - in cars - much more efficient engines than airplanes - they are replacing 90 pounds of gasoline with 1000 pounds plus of batteries for the same range and performance.

I still maintain the numbers won’t work for airplanes. I do believe a lot of people will make a lot of money on research and grants though.


I understand and agree that it might never compete with carbon fuel in energy density. However, it will "be enough" to change the industry. Let me explain (since I come from an industry that has seen the shift from film to digital firsthand):

When digital cameras came, they had terrible resolution and looked awful compared to SLR 35mm. It took well over 10 years before they could resolve more than a film frame and it's arguable if they have the same dynamic range even today. But because of ease of use and reduction of cost, and the immediacy, people took to it anyway.

We buy pre-sliced bread and go to drive-thru's for our food because we can't be bothered to slice our own bread or get out of the car. So, 5-10 years down the road, what you gonna chose?

1. The thing that belches, makes smoke, where you have to get your fingers dirty to check oil and do loud popping run-ups with ancient magnetos an spend a fortune on every little part...

OR

2. Take the one where you jet get in and push throttles forward and get whisked away in silence?

In the end it's not gonna matter that they have half the range, because the cost and convenience will win, just like it did for cameras, scooters and cars.

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 Post subject: Re: Bye Aerospace eFlyer 800
PostPosted: 28 Apr 2021, 12:31 
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Something to keep in mind for fully electric cars, and maybe fully electric airplanes to be, is that there is not enough capacity to recharge them all. Especially when most western countries are abandoning nuclear power generation. Hydrogen is probably a better solution.

Quote:
Rechargeable full-electric cars as we know them today are just a transition, reason why Toyota does not sell any full-electric cars, only hybrids. Toyota is focused on Hydrogen cars. Toyota President Akio Toyoda said in December that "Japan would run out of electricity in the summer if all cars were running on electric power."
https://www.wsj.com/articles/toyotas-chief-says-electric-vehicles-are-overhyped-11608196665

Quote:
Major Swiss supermarket companies and the Switzerland Postal Service are already using Hyundai H2 trucks.
https://www.reuters.com/article/hyundai-switzerland-hydrogen-trucks/hyundai-delivers-first-fuel-cell-trucks-to-switzerland-idUSKBN26S1FM


A few Hydrogen airplanes prototypes are already flying or will soon ...
https://www.zeroavia.com/?utm_source=DJ

https://fuelcellsworks.com/news/hypoint-unveils-breakthrough-hydrogen-fuel-cell-prototype-for-aviation-and-urban-air-mobility/


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 Post subject: Re: Bye Aerospace eFlyer 800
PostPosted: 28 Apr 2021, 12:32 
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Username Protected wrote:
It's sexy. I don't worry about recharging like Mike, because that's an easy problem to solve.

But 500NM with 45min IFR, that's a lot of batteries!!


Quote:
Maybe I am missing something - always ready to learn.


Don't be assuming that dreamers cannot count. ;)

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 Post subject: Re: Bye Aerospace eFlyer 800
PostPosted: 28 Apr 2021, 13:25 
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Username Protected wrote:
In the end it's not gonna matter that they have half the range, because the cost and convenience will win, just like it did for cameras, scooters and cars.

Half the range wouldn't be a problem, but if I understand the numbers above correctly we're talking about maybe 1/8th. I can't use a personal aircraft with one hour endurance for anything much beyond the traffic pattern. There is a threshold of usefulness that must be crossed before convenience and other preferential matters come into play. It's like if your digital camera example weighed 20 lbs and was the size of a watermelon. Even with the same resolution, color depth, instant output, etc. nobody is going to buy one.

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 Post subject: Re: Bye Aerospace eFlyer 800
PostPosted: 28 Apr 2021, 13:57 
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Several airframe and engine companies have been looking at electric propulsion, although not necessarily battery powered. We tend to focus on turbine engines for power.

Anyway, it does appear some technology issues remain. As was previously brought up, batteries are about an order of magnitude less power dense than a hydrocarbon fuel even accounting for the inefficient turbine/piston engine. My back of the envelope calculations assume the aircraft climbs 150 kts to 35 kft at 2000 fpm with 1400 HP available. A little less than 20 minutes which is a little sporty. That uses 300 kW-Hr of energy. The cruises 280 kts with 600 HP for close to 2.5 hours with the 45 min reserve using another 1100 kW-Hr of energy. Most of the concepts I have seen assume that a battery can approach 500 WH/Kg which is more than double todays technology. Some think that is achievable, not sure when though. I think some laboratory experiments have verified it is possible at least on a smaller scale. If that density is achieved than the battery weight would be right at 6000 lbs.....if the battery technology comes.

A long time ago in the aircraft propulsion community we came up with a saying. "It's hard to compete with dead dinosaurs for energy."

The avionics and lighting assuming 100 A at 28 V for 4 hours would only be about 11 kW-Hr, a couple orders of magnitude less than the propulsive energy used. Heat, AC and deice would be greater, but probably not more than 10% of the range.

My guess is the aircraft might be close to 18000 lbs to do what is claimed.

It is interesting that the plane may have optional solar cells and electric wheels for taxi. I assume the solar cells might be useful to charge your cell phone and iPad in flight.

And the whole zero emissions claim. We need a bunch of solar and wind power to be zero emission. Or nuclear.

Our airport KSGH recently installed aircraft electric charging stations, though I am guessing they are maybe similar to the Tesla charging station in capability. For an aircraft that is designed to create revenue flying passengers waiting hours to recharge batteries is probably a non starter.


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 Post subject: Re: Bye Aerospace eFlyer 800
PostPosted: 28 Apr 2021, 14:18 
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Username Protected wrote:
Charging is not a technical challenge anymore. It's just time and money factor.

And that makes it precisely 0% easier to solve.

All of aviation is time and money.

Heck, so is living on Mars.

Mike C.

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 Post subject: Re: Bye Aerospace eFlyer 800
PostPosted: 28 Apr 2021, 14:19 
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Username Protected wrote:
Most of the concepts I have seen assume that a battery can approach 500 WH/Kg which is more than double todays technology. Some think that is achievable, not sure when though.

I'm sure it is. Tesla is already more than half way there with the new 4680 cell.

The problem is energy density of the cell vs. of the battery pack. Original EV cars had a lot of 'dead weight' in the battery pack. Manufacturers are fighting that battle introducing structural batteries. This will be even more important in planes.


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 Post subject: Re: Bye Aerospace eFlyer 800
PostPosted: 28 Apr 2021, 16:21 
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Technically you guys are all over it.

Government Contracting is part of my business. Considering budgets and priorities--what a great time to have an electric airplane company!

Let's see if they get a $535M DOE Loan Guarantee like Solyndra.

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 Post subject: Re: Bye Aerospace eFlyer 800
PostPosted: 28 Apr 2021, 16:58 
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A challenge for electric airplanes with a job is transport efficiency (how much energy it takes to move payload i.e. ton-miles/hp-hr, pax-miles/hp-hr or whatever your favorite units are).

For an aircraft in cruise that is given by payload fraction x L/D. So even if you can get the battery electric aircraft design to close, if it requires a significantly heavier aircraft for the same payload then you start off in the red, so to speak and have to find some other advantage that outweighs the transport efficiency loss.

There was a NASA funded Boeing study that found for airliners the crossover point for GHG emissions was at low (although not zero) levels of hybridization. Of course the crossover depends on emission per power of a turbofan vs grid, battery/electric performance, and the design goals (cost vs emissions etc).

Byron

Username Protected wrote:
Several airframe and engine companies have been looking at electric propulsion, although not necessarily battery powered. We tend to focus on turbine engines for power.

Anyway, it does appear some technology issues remain. As was previously brought up, batteries are about an order of magnitude less power dense than a hydrocarbon fuel even accounting for the inefficient turbine/piston engine. My back of the envelope calculations assume the aircraft climbs 150 kts to 35 kft at 2000 fpm with 1400 HP available. A little less than 20 minutes which is a little sporty. That uses 300 kW-Hr of energy. The cruises 280 kts with 600 HP for close to 2.5 hours with the 45 min reserve using another 1100 kW-Hr of energy. Most of the concepts I have seen assume that a battery can approach 500 WH/Kg which is more than double todays technology. Some think that is achievable, not sure when though. I think some laboratory experiments have verified it is possible at least on a smaller scale. If that density is achieved than the battery weight would be right at 6000 lbs.....if the battery technology comes.

A long time ago in the aircraft propulsion community we came up with a saying. "It's hard to compete with dead dinosaurs for energy."

The avionics and lighting assuming 100 A at 28 V for 4 hours would only be about 11 kW-Hr, a couple orders of magnitude less than the propulsive energy used. Heat, AC and deice would be greater, but probably not more than 10% of the range.

My guess is the aircraft might be close to 18000 lbs to do what is claimed.

It is interesting that the plane may have optional solar cells and electric wheels for taxi. I assume the solar cells might be useful to charge your cell phone and iPad in flight.

And the whole zero emissions claim. We need a bunch of solar and wind power to be zero emission. Or nuclear.

Our airport KSGH recently installed aircraft electric charging stations, though I am guessing they are maybe similar to the Tesla charging station in capability. For an aircraft that is designed to create revenue flying passengers waiting hours to recharge batteries is probably a non starter.


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