Electric Airplanes

[Chuckanut]

Here's a NOVA show on the development of electric airplanes.

https://www.pbs.org/wgbh/nova/video/...airplane-race/

Needless to say, they are not yet ready for Prime Time.

But, it is interesting. All of these aircraft are props, often with 8 10, 12 or more propellers. One outfit is trying to be the Toyota of the business by developing hybrid planes with electric and gasoline power. Most don't' carry many people, usually two to six including the pilot. And all of these planes are what is called 'commuter' aircraft designed to take a small number of people a few hundred miles at most. The eVTOL craft seem to be a very popular idea. Most use batteries, but one outfit is working on hydrogen fuel to power the aircraft. Is that still electric?

I don't see anything here that will challenge jet engines for long distance flights that start to approach the speed of sound. But it's interesting to see the research that is happening. And the planes and helicopters are 'cute' to say the least. They might make good hobby aircraft for those with the time and money to build one.

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[RetMD21]

I watched it too. Cool technology. Not ready for prime time.

[Walt34]

I've seen videos of several experimental electric powered aircraft. Progress is being made but they clearly are not ready for practical commercial use, or even much private use since they're so limited by battery capacity.

When a pound of battery can hold the same energy density as a pound of gasoline or jet fuel things will get much more interesting. I'm sure that will happen some day but not anytime soon.

[sengsational]

There are electric paramotors that are in some level of use. The duration of flight is pretty short, but one pilot I know is buying an electric kit. This reminds me of the early days of electric R/C. The electric guy was the oddball on the field, and the noisy, finicky glow plug engine guys said it would never be good enough. Now, you can't find anyone NOT flying electric. I hope it makes it in people-sized crafts.

[NW-Bound]

Quote:

Originally Posted by Walt34 I've seen videos of several experimental electric powered aircraft. Progress is being made but they clearly are not ready for practical commercial use, or even much private use since they're so limited by battery capacity. When a pound of battery can hold the same energy density as a pound of gasoline or jet fuel things will get much more interesting. I'm sure that will happen some day but not anytime soon.

A gallon of gasoline weighs 6.3 lbs, and holds 33.7 kWh. That's 5.3 kWh/lb.

The battery in a typical EV weighs 1,200 lbs, and stores 85 kWh. That's 0.07 kWh/lb.

[sengsational]

Can't leave out the losses been the storage technology and the force delivered, though.

[ejman]

Quote:

Originally Posted by Walt34 I've seen videos of several experimental electric powered aircraft. Progress is being made but they clearly are not ready for practical commercial use, or even much private use since they're so limited by battery capacity. When a pound of battery can hold the same energy density as a pound of gasoline or jet fuel things will get much more interesting. I'm sure that will happen some day but not anytime soon.

My understanding is that electric motors are 2-3 times more efficient than ICE so to my simpleteon mind that would mean that once batteries get to about half the energy density of gasoline parity will be achieved. Hope the engineers with actual expertise @ this board will confirm or deny.

[CardsFan]

Quote:

Originally Posted by NW-Bound A gallon of gasoline weighs 6.3 lbs, and holds 33.7 kWh. That's 5.3 kWh/lb. The battery in a typical EV weighs 1,200 lbs, and stores 85 kWh. That's 0.07 kWh/lb.

And, the plane does not get lighter as it uses the fuel

[NW-Bound]

Quote:

Originally Posted by ejman My understanding is that electric motors are 2-3 times more efficient than ICE so to my simpleteon mind that would mean that once batteries get to about half the energy density of gasoline parity will be achieved. Hope the engineers with actual expertise @ this board will confirm or deny.

For cars, yes. For prop planes, electric motors probably also have the same efficiency edge.

I don't know if there's any electric motor equivalent to jet engines for high-speed high-altitude flight.

[ejman]

Quote:

Originally Posted by NW-Bound For cars, yes. For prop planes, electric motors probably also have the same efficiency edge. I don't know if there's any electric motor equivalent to jet engines for high-speed high-altitude flight.

I don't know nothin' but your answer made me ask Google and this is what popped up "The world's fastest propeller plane is the Russian-made Tupolev Tu-114, which has a maximum speed of 540 mph (869 kph). The Tupolev has held that record since 1960, even though another prop plane, the XF-84H Thunderscreech, was designed to fly at about 1,000 mph (1,609 kph)." I dunno about jet engines but I guess props could kind of get the job done. ( I do realize the Tupolev is a turbine engine plane with a propeller attached to the shaft). I'm way out of my lane so I be quiet now.

[Walt34]

Quote:

Originally Posted by NW-Bound I don't know if there's any electric motor equivalent to jet engines for high-speed high-altitude flight.

The math and physics are way over my head but as I understand it the upper "speed limit" for propeller-driven aircraft is about 540 mph in large part because beyond that the propeller blades have to exceed the speed of sound. At that point efficiency falls off a cliff and more power doesn't have much effect.

[NW-Bound]

^^^ The XF-84H "Thunderscreech" has an interesting history, as told in an article on Wikipedia.

Indeed, even at idle trust, the prop tips were already traveling faster than the speed of sound.

Quote:

The XF-84H was almost certainly the loudest aircraft ever built, earning the nickname "Thunderscreech" as well as the "Mighty Ear Banger". On the ground "run ups", the prototypes could reportedly be heard 25 miles (40 km) away. Unlike standard propellers that turn at subsonic speeds, the outer 24–30 inches (61–76 cm) of the blades on the XF-84H's propeller traveled faster than the speed of sound even at idle thrust, producing a continuous visible sonic boom that radiated laterally from the propellers for hundreds of yards. The shock wave was actually powerful enough to knock a man down; an unfortunate crew chief who was inside a nearby C-47 was severely incapacitated during a 30-minute ground run...

The development of this aircraft was stopped after 12 test flights because of various problems. It never reached its speed goal.

See: https://en.wikipedia.org/wiki/Republ...Thunderscreech


PS. By the way, helicopters have a much lower top speed compared to fixed-wing aircraft because of their long rotors. When the chopper is flying forward, the tip of the advancing blade will reach sonic speed long before the retreating blade.

If you make the chopper blade shorter, then you have to spin it faster to generate the same lift, and still have limitation with keeping the tip speed under the speed of sound. I am not an aeronautical engineer, but know that rotorcraft designers try to tweak a lot of things over the years, and can only get so far, and rotorcraft can only fly so fast. The laws of physics are tough to evade.

[ERD50]

Quote:

Originally Posted by ejman My understanding is that electric motors are 2-3 times more efficient than ICE so to my simpleteon mind that would mean that once batteries get to about half the energy density of gasoline parity will be achieved. Hope the engineers with actual expertise @ this board will confirm or deny.

Yes, but if you take the numbers NW-Bound provided, (5.3/.07 = 75x advantage to fuel vs battery), and adjust by a factor of 3, that still a huge 25x advantage to fuel.

And then...

Quote:

Originally Posted by CardsFan And, the plane does not get lighter as it uses the fuel

that's a big one. Drag along 25x the weight, and halfway to your destination it's almost 50x the weight! I think we've all seen films of planes fully loaded with fuel that can barely take off from a long runway, but do much better once they burn off some of that weight.

Although, it appears there may be some short hops that fit the profile and take advantage of other properties of electric flight, so we might see them in that niche in a few years. That would be pretty cool, I think.

-ERD50

[NW-Bound]

Whenever the comparison between electric power and fuel power comes up, it brings up in me this misgiving: What happens to humanity when fossil fuel runs out, which it will inevitably do?

Will we have found another source of power, or invented that super-duper battery, or the suitcase-sized nuclear plant?

And if we don't, what happens to mankind?

We have been so reliant on fossil fuel, first coal and now petroleum. It's not just as an energy source, but plastics, fertilizer, and other compounds also come from petroleum. Just for fuel alone, will people be able to travel as they do now? Who wants to sit in a sail boat taking a month or more to cross the ocean? Not just jet travel, but what will run the cruise ships that now guzzle huge amounts of diesel?

I guess biodiesel can be a replacement, and vegetable cultivation can be done with the aid of power from solar energy, but can biofuel be as cheap as petroleum?

Yet, we are still indulging in wasteful activities, such as development of rocket planes that can travel between any two points on earth in an hour, or space travel for recreation. Such BS, even among some self-proclaimed green energy advocates. Unadulterated BS, unless they can show me an electric-powered rocket.

[Closet_Gamer]

If the government ever starts taxing carbon or specifically targets the aviation industry (for either climate change or as a bank shot to go after wealth disparity) we will see investment in these areas surge.

We may start to see real trade-offs in terms of price vs. time to travel. Want to go Philly to Denver in 4 hours, $1200. Willing to do it on a more fuel efficient plane that takes 8 hours or has to land to swap batteries? $600.

Will be very interesting to see this play out.

[DrRoy]

Watched it also. Would be cool to have/rent one. The Alpha Electro was ~$155K.

[Koolau]

Quote:

Originally Posted by ERD50 Yes, but if you take the numbers NW-Bound provided, (5.3/.07 = 75x advantage to fuel vs battery), and adjust by a factor of 3, that still a huge 25x advantage to fuel. And then... that's a big one. Drag along 25x the weight, and halfway to your destination it's almost 50x the weight! I think we've all seen films of planes fully loaded with fuel that can barely take off from a long runway, but do much better once they burn off some of that weight. Although, it appears there may be some short hops that fit the profile and take advantage of other properties of electric flight, so we might see them in that niche in a few years. That would be pretty cool, I think. -ERD50

While weight is an issue in ground based vehicles (cars, trucks, trains, etc.) it's much more important in aircraft as a HUGE amount of the energy involved in flying is 1) Lifting an aircraft initially to its most efficient altitude and 2) simply holding the aircraft up at all times. In ground based vehicles, weight is a small factor in additional rolling resistance and a bit bigger factor in acceleration. IOW if you drive my big old Buick in town it gets 20 mpg because you have to accelerate that huge car up to speed several times in a trip. Traveling cross country, you accelerate once (1st approx.) so weight isn't near the issue it is in town. My Buick gets about 32mpg at 70 mph w/AC on. In aircraft, every pound you have to lift costs you a bunch of fuel and that's before you even accelerate it to 500 mph OR hold it up in the sky for 5 hours.

When you drive a couple of hundred miles in your Tesla, you're unlikely to be lifting that heavy battery more than a couple of thousand feet. Also, you arguably regain much of the energy on the way back down. One might think that coming down in an aircraft also involves "recapture" of the potential energy that was expended getting to altitude. In a small aircraft (like the C-150 I used to fly) that may be true. Modern airliners have to scrub off speed as they descend because of air-traffic management and the issues of maintaining lift at different altitudes. It's complicated.

So, if I'm making a point it would be this: In addition to what has already been mentioned about the issues that currently prevent reasonable range of aircraft (but not so much for EV cars) there are other less obvious factors that do NOT favor electrifying aircraft.

One example to make my point: In rotary aircraft (helicopters) I think I've heard that as much as 75% of the fuel is used JUST to keep the aircraft at altitude. In conventional aircraft, I'm sure the proportion needed to keep the aircraft aloft is considerably smaller but still WAY more important than weight is in a car/truck/bus, etc.

Next, let's talk about "batteries." Unless you consider a hydrogen fuel cell to be a battery, then the problems are even greater. A fuel cell is like an ICE engine. It takes on-board fuel adds oxygen from air and converts to electricity - actually consuming something (which has weight). Therefore, maybe we'll be able to use fuel cells in aircraft some day. Batteries, I seriously doubt - maybe with exception of small aircraft with limited range.

I am not an electrochemist but was "forced" to study the subject and "do" the subject occasionally (anyone ever use a dropping mercury electrode polarograph - well never mind.) But what I learned about batteries in general is that you are essentially storing charge within a reversible chemical reactive "cell." No matter how hard you try, no matter how much you "improve" the technology, you are not going to store the kind of energy in a chemical cell that you can store in the equivalent weight of (for instance) gasoline. I know even less about capacitive storage of electrical energy, but I'm guessing the same thing applies. You simply can't compete with gasoline when it comes to strong energy. Yes, we'll get closer. I'm hearing of 5% improvement per year in batteries. I think that bodes well for eventually become an EV driving society. For aircraft - we would never get there at 5% improvement per year - especially when there is a "limit" on how much energy a cell can "theoretically" hold (and we can calculate that for any set of chemicals.) I have once again told you way more than I know, so YMMV.

[Koolau]

Quote:

Originally Posted by NW-Bound Whenever the comparison between electric power and fuel power comes up, it brings up in me this misgiving: What happens to humanity when fossil fuel runs out, which it will inevitably do? Will we have found another source of power, or invented that super-duper battery, or the suitcase-sized nuclear plant? And if we don't, what happens to mankind? We have been so reliant on fossil fuel, first coal and now petroleum. It's not just as an energy source, but plastics, fertilizer, and other compounds also come from petroleum. Just for fuel alone, will people be able to travel as they do now? Who wants to sit in a sail boat taking a month or more to cross the ocean? Not just jet travel, but what will run the cruise ships that now guzzle huge amounts of diesel? I guess biodiesel can be a replacement, and vegetable cultivation can be done with the aid of power from solar energy, but can biofuel be as cheap as petroleum? Yet, we are still indulging in wasteful activities, such as development of rocket planes that can travel between any two points on earth in an hour, or space travel for recreation. Such BS, even among some self-proclaimed green energy advocates. Unadulterated BS, unless they can show me an electric-powered rocket.

I feel your pain re: eventually running out of fossil fuels. I won't address the "BS" argument. One man's BS is another man's "pushing back the boundaries of science."

The obvious initial answer is that we'll prioritize - just like we do now - on the basis of cost. Our one and only "cruise" I think they mentioned it took 1 gallon of bunker oil to move our ship 11 inches in the water. Guess what, the cruise industry will be hard hit by more scarce fossil fuels - or, maybe they'll go back to sails. Cruise ships aren't really in a hurry anyway. BUT, you want to go to granny's place for TG or XMAS - would you pay twice what you pay now? Three times? Probably. That trip to Palm Springs for the weekend - probably gone when FFs cost $10/gal. BUT planes will still be flying even when it's more expensive. Maybe not as many flights and much more expensive, but they'll fly. Also, in concept, energy is fungible. At some point, we'll take electricity (either like we make it now with windmills or solar panels - or hey, how about psssssst. nuclear) and turn it into some kind of "storable" fuel (maybe hydrogen - it is already easy to make hydrogen "from" electricity - not cheap, but easy.) SO, we'll figure it out. Just get ready to pay more or travel less luxuriously. Fossil fuels will never actually run out. Where they are needed they will be discovered, extracted, refined and used for 1000 more years - just not in the quantities (and especially not at the price) of today. There will be applications that simply demand SOME fossil fuels that will make them "available" for long after our grand kids are gone. YMMV

[folivier]

Two years ago on our Alaska trip there was an electric float plane near Anchorage that was scheduled to do some test flights, not sure of its success.
There is some interest in bringing back blimps for slow travel. These could use solar panels for additional charging while traveling. But the current Helium shortage could slow down that development.

[GreenEggs]

High-speed rail seems like the most efficient option for inland people transport. The US needs to get "on board" with developing high-speed rails. Save the jet fuel for crossing the oceans.

In my elementary opinion, it seems that hydrogen would be the best bet for powering airliners in the future.