Really interesting new electric plane

[MIFlyer]

Only if you ignore physics.
No. Hauling around a generator, extra motor, and fuel and not using it is not a cost savings.Hauling around extra equipment does not save money. Airplanes do not benefit from regenerative braking, so there is no advantage to a hybrid.

Don't forget about the electric motor, generator, and batteries you now have to maintain. Turning fuel into electricity and storing it in a battery, then using it to run a motor is even less efficient
Not relevant in comparing fossil vs hybrid
Ask a cargo hauler if he'd like to use up his useful load and space on every flight with redundant systems that aren't used.
Again, ignoring the costs of batteries, electric motor, and generator.
Not relevant in fossil vs hybrid comparison

well, besides the short flight where they would go all electric and perhaps have electric only AC with no backup generators on board, there's also the difference between the power to take off vs the power to economy cruise and land.

hybrid cars work this way too, they put a tiny electric and tiny gas engine together, and run the electric except when they need the power of both combined. seems to work well int he prius for example, where they get better mileage than a similar gas only car would.

I know cars aren't airplanes, but it does seem like there are some possibilities

 

[Salty]

well, besides the short flight where they would go all electric and perhaps have electric only AC with no backup generators on board, there's also the difference between the power to take off vs the power to economy cruise and land.

hybrid cars work this way too, they put a tiny electric and tiny gas engine together, and run the electric except when they need the power of both combined. seems to work well int he prius for example, where they get better mileage than a similar gas only car would.

I know cars aren't airplanes, but it does seem like there are some possibilities

Hybrid cars have regenerative braking. It's the only thing that makes them more efficient. Try driving a hybrid car at 70 mph for an entire tank. It gets just a as lousy a mileage as any other car. They only work well when you are stopping a lot and can charge the battery due to necessary slowdown. There is no necessary slowdown in a plane this size. If you tried to chatge the battery with the prop, you'd be wasting more energy slowing down than you would gain by charging the battery. It's physics.

 

[ktup-flyer]

After you get that working, you can replace the small fuel engine with a windmill.

Just throw a bunch of RATs on it

 

[MIFlyer]

Since you brought it up, shall we talk about the cost of replacing these battery packs that won't last long with lots of cycles? It makes a tank reseal look cheap.

sure, should we also talk about the hot section inspection you're not doing since it doesn't have one?

 

[Salty]

sure, should we also talk about the hot section inspection you're not doing since it doesn't have one?

I don't understand why people want to ignore physics and play pretend.

 

[edo2000]

Every one of those airports would also get TSA restrictions. Plus they'll need to add to the terminal (or build one from the ground up) for security screening, gates, baggage handling, ticket counters, parking, etc. It will not be a good thing for local airports.

Many smaller airports don't do TSA security. Examples I'm familiar with are in Alaska, where lots of scheduled flights operate from lots of smaller airports without TSA. The arrival gates for these flights at the big hub airport like Anchorage, are outside of security. These operators use aircraft from Caravans to Q400's.

 

[donjohnston]

"And if my mother had wheels she'd be a wagon"

I believe you were looking for "bike".

 

[tspear]

Every one of those airports would also get TSA restrictions. Plus they'll need to add to the terminal (or build one from the ground up) for security screening, gates, baggage handling, ticket counters, parking, etc. It will not be a good thing for local airports.

Actually that part is rather easy. Plenty of airports have a secure section which is really basic. A red marked off area on the plane side. Dedicated security door to the red zone. Then scanner and other areas are secured by police each morning before flights can resume.
It actually helps local airports. More of the public use it, generates tax revenue, increases the profile and public viability.

Tim

 

[tspear]

I don't understand why people want to ignore physics and play pretend.

Because when you were a child, the same thing was said about the new invention called a wheel. Just pretend it will make life easier, you can carry more, it will save you effort/money.....

Tim (could not resist)

 

[Salty]

Because when you were a child, the same thing was said about the new invention called a wheel. Just pretend it will make life easier, you can carry more, it will save you effort/money.....

Tim (could not resist)

Yeah yeah. But I could say the same about you for not talking about teleportation instead.

 

[tspear]

Yeah yeah. But I could say the same about you for not talking about teleportation instead.

lol, touche.

Tim

 

[MIFlyer]

I don't understand why people want to ignore physics and play pretend.

a BIT offensive, but...

1. I'm not advocating this, i'm sharing something that is interesting with a community ostensibly established to shoot the bull about flying related topics. the comment felt a little personal (if it's not, that's fine, but it's how it came across) I have a BS in chemistry, so I understand enough about physics, mass and conservation of energy to understand your point.

2. this, nor anything, is not a purely physics exercise (I also have an MBA). there is cost, convenience, noise, MX, yadda, yadda factors to go into this beyond "what's the cheapest way to create an erg of energy on an airplane". Even with that, it's unknown (by me at least) if, for 100 mile routes, this would be lighter and cheaper than a turbine.

Then you have to layer in differing MX, including the fact that these would be used to fast cycle, short trips, which I understood to be bad for turbines and cause you to hit mandatory inspections quickly?

I'm not disagreeing that long haul will likely be fossil fuel until there is a massive change in energy density of batteries, but for the 100 mile trip (or less, maybe 50?) I don't think you need a million tons of batteries

 

[tspear]

A few more details.
http://www.popularmechanics.com/flight/news/a28540/boeing-backed-electric-plane-fly-2020s/

Tim

 

[deonb]

I'm not disagreeing that long haul will likely be fossil fuel until there is a massive change in energy density of batteries, but for the 100 mile trip (or less, maybe 50?) I don't think you need a million tons of batteries

To be exact, to replace the equivalent of 1 lbs of Jet A inside a Turbine requires 50 lbs of batteries.

What would you need for a 100 mile trip for an equivalent airplane? Maybe 400 lbs on a PC-12 if you include the reserve? That means you're talking about 20'000 lbs of batteries to carry. Even if you go all-out electric and throw out your PT6 and all support systems and get that weight back, you're still talking about 15'000 lbs of extra weight.

I love battery tech. I currently drive a Tesla Model S, a Leaf, have a Model 3 on order and drove hybrids before it. Waiting on the edge of my seat for an electric Semi. BUT I don't think battery tech is near far enough that Zunum to pull this off. They're basically designing an airframe and hoping for battery tech to catch up.

 

[MIFlyer]

To be exact, to replace the equivalent of 1 lbs of Jet A inside a Turbine requires 50 lbs of batteries.

What would you need for a 100 mile trip for an equivalent airplane? Maybe 400 lbs on a PC-12 if you include the reserve? That means you're talking about 20'000 lbs of batteries to carry. Even if you go all-out electric and throw out your PT6 and all support systems and get that weight back, you're still talking about 15'000 lbs of extra weight.

I love battery tech. I currently drive a Tesla Model S, a Leaf, have a Model 3 on order and drove hybrids before it. Waiting on the edge of my seat for an electric Semi. BUT I don't think battery tech is near far enough that Zunum to pull this off. They're basically designing an airframe and hoping for battery tech to catch up.

wow. great info. i had not done the calculations (obviously). I'm wondering how they think this is feasible then? what are we missing?

 

[tspear]

To be exact, to replace the equivalent of 1 lbs of Jet A inside a Turbine requires 50 lbs of batteries.

Just curious where that math comes from.

Tim

 

[Salty]

Just curious where that math comes from.

Tim

I'm not sure the math is quite that bad. I think maybe its closer to 50lbs per gallon of fuel.

But, the bad part is that as the batteries approach empty, the weigh of the batteries needed approaches infinity. I.E., an empty battery weighs the same as a full one.

 

[Tantalum]

Just curious where that math comes from.

I assumed it was a KW conversion? Seems that would be a relatively direct way to compare "power" available.. unless it is broken down to joules/kg of fuel and said battery

Thanks @deonb for the breakdown. I agree, hybrid and electric tech is really cool and definitely has applicable uses where it really is, from a physics standpoint, the most efficient and practical. We have solar panels on our house and the cordless weed trimmer and electric lawnmower for a small-ish yard make sense.. just like with cars hybrid tech makes sense as well. But for the vast amounts of sustained power that planes need plus their weight sensitivity (particularly if you are looking for efficiency) I don't think the energy density of "a battery" will ever match that of fuel. I am just not sure it is physically possible at the atomic level. But we don't know what we don't know... so maybe there will be some breakthrough someday

 

[tspear]

I assumed it was a KW conversion? Seems that would be a relatively direct way to compare "power" available.. unless it is broken down to joules/kg of fuel and said battery

Thanks @deonb for the breakdown. I agree, hybrid and electric tech is really cool and definitely has applicable uses where it really is, from a physics standpoint, the most efficient and practical. We have solar panels on our house and the cordless weed trimmer and electric lawnmower for a small-ish yard make sense.. just like with cars hybrid tech makes sense as well. But for the vast amounts of sustained power that planes need plus their weight sensitivity (particularly if you are looking for efficiency) I don't think the energy density of "a battery" will ever match that of fuel. I am just not sure it is physically possible at the atomic level. But we don't know what we don't know... so maybe there will be some breakthrough someday

Storage kwh does not matter. Production of kw (power) or thrust (work) matter. So if you are converting storage energy you then need to multiple by the rough efficiency of the engine to produce HP at the shaft. Assume identical propellers to keep the math/concept principle as close as possible. You then are concerned with the power requirements at the turboshaft from a turbine engine. Going on memory, most turboprops run between .4 and .5 conversion. So less then half of the energy stored in the fuel is converted into mechanical energy. While electric motors typically run around 95% efficient; but use 90% to account for losses in the electrical system. That brings the ratio previously mentioned from 50lbs of batteries to one pound of Jet-A closer to 25lbs of bat6teries to one pound of Jet-A.

The end result, not as far apart as many assume; and potentially viable for short range. The other consideration; in the hybrid plane they are discussing a 500kw generator. The bigger the engine the more efficient it tends to be....

Tim

 

[deonb]

Just curious where that math comes from.

Tim

Sure:

Jet-A published efficiency is 39.5kWh/gallon
Jet-A in a turbine is 60% efficient vs. 90% efficient for electric, so that's 39.5kWh * 60% / 90% = 26.33 kWh/gallon equivalent in kinetic conversion
26.33 kWh/gallon = 3.87 kWh per lbs of Jet-A (6.8 lbs per gallon for Jet-A)
Managed and cooled batteries weigh 13 lbs/kWh (Tesla does a 100kWh in 1300lbs), so 3.87kWh weighs 50.33 lbs

Thus: 1 lbs of Jet-A is the equivalent of 50.33 lbs of lithium batteries. Rounded down you get 50.

NOTE: This is for temperature controlled batteries like Tesla does. If you don't do temp-control the batteries it can improve the weight ratio by a bit (up to 30% or so lighter), but then you get 500 cycles on them instead of 1500 cycles. This is what Pipistrel is doing for now, but that means replacement costs goes through the roof.

NOTE 2: This is comparing against Turbine-burned Jet-A, which is a very efficient thing to try and compete against. Comparing instead to an internal combustion engine burning 100LL the ratio isn't quite as bad (about 25lbs/lbs equivalent).

 

[GlennAB1]

Just throw a bunch of RATs on it

You might want ADG's.

 

[Palmpilot]

...hybrid cars work this way too, they put a tiny electric and tiny gas engine together, and run the electric except when they need the power of both combined....

That's the way a Prius works, but my civic Hybrid does the opposite. It runs the gas engine all the time*, and the electric motor provides extra power when needed.

*The one exception to that statement is that the driver can set the controls to turn off the gas engine when the car is stopped.

 

[Palmpilot]

Hybrid cars have regenerative braking. It's the only thing that makes them more efficient. Try driving a hybrid car at 70 mph for an entire tank. It gets just a as lousy a mileage as any other car. They only work well when you are stopping a lot and can charge the battery due to necessary slowdown. There is no necessary slowdown in a plane this size. If you tried to chatge the battery with the prop, you'd be wasting more energy slowing down than you would gain by charging the battery. It's physics.

I wouldn't call the 50+ MPG that my hybrid got at 70 mph when it was new "as lousy a mileage as any other car." That was one reason why I got the Civic Hybrid instead of a Prius. My Civic got better mileage at highway speeds than it did around town, whereas the Prius did the opposite, according to the published specs, and I was doing a lot of highway driving at the time.

Unfortunately, the low-rolling-resistance tires that it came with are no longer available in the size that fits my car, so my highway mileage has dropped below 50 now.

 

[ateamer]

Actually that part is rather easy. Plenty of airports have a secure section which is really basic. A red marked off area on the plane side. Dedicated security door to the red zone. Then scanner and other areas are secured by police each morning before flights can resume.
It actually helps local airports. More of the public use it, generates tax revenue, increases the profile and public viability.

Tim

Oh, good to know. Thanks.

 

[Salty]

I wouldn't call the 50+ MPG that my hybrid got at 70 mph when it was new "as lousy a mileage as any other car." That was one reason why I got the Civic Hybrid instead of a Prius. My Civic got better mileage at highway speeds than it did around town, whereas the Prius did the opposite, according to the published specs, and I was doing a lot of highway driving at the time.

Unfortunately, the low-rolling-resistance tires that it came with are no longer available in the size that fits my car, so my highway mileage has dropped below 50 now.

Nope. You didn't get 50 mpg running an entire tank out at 70 mph. Your battery died long before that.

 

[GlennAB1]

Many hybrid automobiles gas milage is exaggerated by averaging in an unrealistic amount of low mph travel, where the electric motor is solely used.

 

[deonb]

Many hybrid automobiles gas milage is exaggerated by averaging in an unrealistic amount of low mph travel, where the electric motor is solely used.

True for all vehicles. Nobody gets EPA mpg.

The places highlighted in red below is where people actually drive at the EPA tested highway speed of 60mph. 'Where's Waldo' you say?

 

[Palmpilot]

Nope. You didn't get 50 mpg running an entire tank out at 70 mph.

Well, if you want to quibble, I wasn't doing 70 mph until I got up to speed, but that's a relatively short percentage of the total trip. The measured gas mileage on highway trips, from fill up to fill up, was consistently above the manufacturer's spec of 51 mpg.

Your battery died long before that.

It most certainly did not, and does not. The only time there is any battery drain is on upgrades and during acceleration.

I take it you've never driven a Civic Hybrid.

 

[Salty]

Well, if you want to quibble, I wasn't doing 70 mph until I got up to speed, but that's a relatively short percentage of the total trip. The measured gas mileage on highway trips, from fill up to fill, up was consistently above the manufacturer's spec of 51 mpg.



It most certainly did not, and does not. The only time there is any battery drain is on upgrades and during acceleration.

I take it you've never driven a Civic Hybrid.

You're not making sense. If you're not draining the battery, then you aren't gaining any benefit of being hybrid. The only case where you can get on the highway and do 70 mph for the entire tank and gain benefit from a hybrid is if there are lots of large grades up and down. And in this case again, you are not going to get this benefit in an aircraft that does one climb and one descent. You will not even get the benefit in the descent because you'd have to be using the propellor to regenerate power, which would slow you down and waste the energy.

 

[Palmpilot]

Many hybrid automobiles gas milage is exaggerated by averaging in an unrealistic amount of low mph travel, where the electric motor is solely used.

With my Civic Hybrid there is no time when only the electric motor is being used.

When I still had the original equipment type tires, it was easy to get the promised 51 mpg on the highway, and I often exceeded that. In city driving, I found that I had to drive with a very light foot to get the promised mpg (which was in the mid forties).

 

[Velocity173]

Nope. You didn't get 50 mpg running an entire tank out at 70 mph. Your battery died long before that.

The battery on hybrids just isn't charged by regenerative braking. The car's alternator charges the battery while the engine is running.

I used to drive mostly highway to work when I drove my Ford C-Max hybrid and would average 50 MPG for the trip. Actually used more gas on short daily trips because of the gas consumed during stop and go acceleration.

 

[GlennAB1]

True for all vehicles. Nobody gets EPA mpg.

The places highlighted in red below is where people actually drive at the EPA tested highway speed of 60mph. 'Where's Waldo' you say?

View attachment 57050

My Ford Escape has consistently got better than the advertised highway MPG.

 

[deonb]

You will not even get the benefit in the descent because you'd have to be using the propellor to regenerate power, which would slow you down and waste the energy.

Yip. You'd either have to cruise longer (more fuel) and take a steeper descent to be able to use regen in the descent. Or reduce your descent angle to stretch your range - more fuel again. Any way you shape it, if you've done regen, you used up more fuel to do that than energy you'll be able to get back out of the battery.

Different in a car - you're substituting brakes for regen. In an airplane, the need to brake is minimal.

 

[Palmpilot]

You're not making sense. If you're not draining the battery, then you aren't gaining any benefit of being hybrid. The only case where you can get on the highway and do 70 mph for the entire tank and gain benefit from a hybrid is if there are lots of large grades up and down. And in this case again, you are not going to get this benefit in an aircraft that does one climb and one descent. You will not even get the benefit in the descent because you'd have to be using the propellor to regenerate power, which would slow you down and waste the energy.

I don't doubt that it doesn't make sense to you, but I've been driving the Honda hybrid for 14 years, so the chances of my not knowing its characteristics by now are pretty much nil.

I think that what you're missing is that one of the benefits of a hybrid is that the gas engine can be a lot smaller. When you're driving at a constant speed on a level road, the power requirements are low enough so that no help from the electric motor is needed, and the small gas engine is sufficient to maintain speed. This is confirmed by watching the ammeter, which under those conditions shows the current going into and out of the battery to be zero.

The above explanation does not apply to a Prius, which as I understand it uses the electric motor full time.

 

[deonb]

The battery on hybrids just isn't charged by regenerative braking. The car's alternator charges the battery while the engine is running.

I used to drive mostly highway to work when I drove my Ford C-Max hybrid and would average 50 MPG for the trip. Actually used more gas on short daily trips because of the gas consumed during stop and go acceleration.

Different purpose when the battery is charged off the alternator. Hybrids do an engine-based recharge for 2 reasons:

a) To preserve the hybrid battery. If you run it empty it breaks.
b) To be able to give you electric-assisted acceleration. Increases performance.

But this is not an efficiency thing. Even if you have a super-efficient electric motor, if the generator just directly drives the electric motor (ala GM Volt) it will have less losses than storing the energy in the battery and retrieving it for later.

 

[deonb]

The above explanation does not apply to a Prius, which as I understand it uses the electric motor full time.

Not quite. A Prius has a hybrid synergy drive. It can use either electric or gas or both and it combines the power in a planetary gearbox.

A GM Volt will however fit your example. It has only electric motors on the drivetrain that gets powered by a battery, and it has a gas generator to fill the battery.

 

[Palmpilot]

The battery on hybrids just isn't charged by regenerative braking. The car's alternator charges the battery while the engine is running.

I used to drive mostly highway to work when I drove my Ford C-Max hybrid and would average 50 MPG for the trip. Actually used more gas on short daily trips because of the gas consumed during stop and go acceleration.

On my Civic Hybrid, there are two batteries, a smallish lead-acid one in the engine compartment, which I believe is charged by an alternator, and a battery of nicad cells behind the rear seat. The latter is the one that is used to power the electric motor, and is charged by the electric motor during deceleration or braking. What connection there is between the two batteries, I don't know. I suspect that the lead-acid battery can power the electric motor during starting, to deal with times when the nicad charge gets too low to do it.

 

[Palmpilot]

Not quite. A Prius has a hybrid synergy drive. It can use either electric or gas or both and it combines the power in a planetary gearbox.

A GM Volt will however fit your example. It has only electric motors on the drivetrain that gets powered by a battery, and it has a gas generator to fill the battery.

It's interesting to see the different approaches that different manufacturers have used in hybrid design.

I'm not even sure whether current-production Hondas are set up the same way as mine (which was a 2003). That's why I've been careful to say "my Hybrid," rather than referring to Honda hybrids in general.

 

[Velocity173]

Different purpose when the battery is charged off the alternator. Hybrids do a engine-based re-charge for 2 reasons:

a) To preserve the hybrid battery. If you run it empty it breaks.
b) To be able to give you electric-assist acceleration. Increases performance.

But this is not an efficiency thing. Even if you have an electric motor that's more efficient, if the engine just directly drives the electric motor (ala GM Volt) it will have less losses than storing the energy in the battery and retrieving it for later.

Three ways the Cmax battery is charged. Regenerative braking being a quick charge is the primary. Second, in coast mode while the engine is shutdown, the spinning of the electric motor charges the battery. Finally, while the engine is running, it is charging the battery through the alternator. Once the battery gets to a certain charge (highway), the battery kicks in and will power the motor (max 85mph). When the battery gets below a certain level, the auto EV kicks the motor off and the engine engages. Once the battery is charged again, the cycle repeats.

Regenerative braking alone isn't going to provide enough charge to get 50 MPG on mostly highway driving.

 

[Salty]

The battery on hybrids just isn't charged by regenerative braking. The car's alternator charges the battery while the engine is running.

I used to drive mostly highway to work when I drove my Ford C-Max hybrid and would average 50 MPG for the trip. Actually used more gas on short daily trips because of the gas consumed during stop and go acceleration.

You don't gain efficiency converting back and forth to electric. You lose it.