Firms Team Up On Hybrid Electric Plane Technology (bbc.com)

An anonymous reader shares a report: Airbus, Rolls-Royce and Siemens are to develop hybrid electric engine plane technology as part of a push towards cleaner aviation. The E-Fan X programme will first put an electric engine with three jet engines on a BAe 146 aircraft. The firms want to fly a demonstrator version of the plane by 2020, with a commercial application by 2030. Firms are racing to develop electric engines for planes after pressure from the EU to cut aviation pollution. Each of the partners in the programme will be investing tens of millions of pounds, they said on a press call. The firms are developing hybrid technology because fully electric commercial flights are currently out of reach, a spokeswoman said.

Comments

Diminishing returns

[Dan East]

It's good to invest in research in this area, but the laws of diminishing returns are pretty harsh with aviation. Having a turbine powered generator to provide power for an electric turboprop is a lot of extra complexity (and components to fail) just to pick up a very small amount of efficiency (IE burning less jet fuel).

While it is certainly good to have figured out the technology involved in electric engines, it will require a revolutionary new battery technology that has vastly better energy density than what we have now to make this practical.

Also, I found this part a bit odd:

The weight of batteries coupled with the weight of equipment to cool electric engines are two limiting factors at present, she said.

It's really, really cold up at cruising altitudes (-70 F), so it seems odd they need cooling equipment. I guess maybe that's just for take offs?

Re:Diminishing returns

[MightyYar]

so it seems odd they need cooling equipment.

You still need a way to transfer the heat from where it is generated to the nice, cold heat sink. As a simple thought experiment, a motor operating in a thermos isn't really going to care much about the outside temperature - you need a way to get the heat from the motor to the air outside the thermos. Obviously you won't purposely insulate the aircraft motor, but the principle is the same.

Think about the amount of power dissipated... a 2 MW motor - even if 99% efficient - is going to dissipate 20 kW of heat. Think about the heatsink for your ~100W CPU and scale it up by 200x. Not an impossible task but definitely an engineering challenge.

Re:Diminishing returns

[Rei]

It's an awful lot of different benefits. Your generator always runs in an optimal power band. You can add more, smaller electric motors without sacrificing efficiency - to the contrary, they increase efficiency and can be used to significantly boost lift for takeoff / landing by pushing more air across the wing. The article discusses how quieter operation means that they can fly more, bigger planes into cities, especially at night. Same goes with lower pollution at takeoff/landing (airports tend to be big point sources of pollution). It's a lot of individual advantages.

Pure electric flight will come, but "not yet". Yes, you can make electric planes, but they're far from economic for ferrying passengers and cargo. Once you start getting closer to li-air energy densities, however, things start looking a lot more interesting; the much touted "solid state" batteries have some potential in this regard, in that they have potential to reduce or eliminate damage from dendrite formation. I know Musk really wants to be the first to build a pure electric aircraft to break the sound barrier. From that, I imagine he's thinking of something like a high-bypass arcjet rather than props, which would be really fascinating, although I'd expect it to have big problems with ozone generation (if that is in fact the approach he's thinking of). A high bypass engine involving microwave plasma heating might be another way to get to high speeds with decent efficiency, possibly with lower ozone concerns. Either way, you're constrained by not wanting your "exhaust" to be moving much faster than the aircraft if you want your efficiency to be good (a critical concern if you're going for battery propulsion).

BTW, I find it interesting that people don't talk nearly as much about electrifying the other elephant in the room: shipping. Where I am, the fishing fleet is our biggest fuel consumer (although cargo shipping is another huge consumer). A fishing boat goes out with a sizeable chunk of its net weight comprised of diesel, and returns with a sizeable chunk of its net weight comprised of fish. Not an easy challenge either - but it too will eventually happen.

Re:Diminishing returns

[bws111]

Engine: a machine with moving parts that converts power into motion.

Re:Diminishing returns

[vtcodger]

I dunno. I used to use arguments similar to yours about the dangers of Hydrogen as a fuel. Then someone pointed out to me (correctly. I checked) that "Town Gas" -- a noxious mixture of gases generated from coal -- which was widely used prior to the widespread availability of Natural Gas -- was often half or more Hydrogen and it was really no more catastrophe-prone in practice than NG.

Re:Diminishing returns

[Rei]

Hydrogen is about 50% by volume in town gas, not by mass. See Ullmann's Encyclopedia, "Gas Production", p4. Also 5% N2, 5% CO2, 40% CO. That's about 6% by mass. Town gas is mostly (~70%) carbon monoxide by mass.

Lighter than air craft won't work

[sjbe]

More use of lighter than air craft. Blimps, zeppelins, etc.

We tried that. It didn't end well. It's a romantic idea but not a practical one for mass transportation. They have some niche uses but they aren't the answer you are looking for.

Zeppelins! Air travel of the future?

[Geoffrey.landis]

More use of lighter than air craft. Blimps, zeppelins, etc.

We tried that. It didn't end well. It's a romantic idea but not a practical one for mass transportation. They have some niche uses but they aren't the answer you are looking for.

Partly true. But the serious problem with Zeppelins was weather: they are inherently large and slow, so storms absolutely kill them. Forget the Hindenburg: overwhelmingly, the cause of dirigible crashes was thunderstorms.

But in the 1930s we couldn't really predict weather, and we couldn't really look at what the weather was like far away. Today we have satellites and weather prediction. If there's a thunderstorm, we know about it. We don't have to fly the dirigibles through it because we didn't know it was there. So, the main cause of dirigible crashes is, today, a solvable problem.

Still-- today people really don't want to spend a few days crossing the Atlantic, and people expect their flights to take off whether or not it's raining: people won't take "oh, come back tomorrow, weather's bad" for a trip.

So, no, probably not mass transportation. You're right that they could be useful for other niches, though.

Physics is a harsh mistress

[sjbe]

News-fucking-flash: materials and propulsion technologies may have improved just a bit in the past eighty years.

News fucking flash: physics of airships has not. They are slow, bulky, cannot fly in inclement weather, require huge and expensive hangars, are expensive to operate, and no technological advance in the last 100 years has made them an economically viable replacement for jet/propeller driven aircraft. Airships had their day for transporting people and that day has passed. There are better and more sensible options in close to every circumstance you can think of for transporting both people and cargo.

Re:Physics is a harsh mistress

[WheezyJoe]

So, your point is light and more rigid materials. You haven't answered sjbe's point of slow, bulky, and cannot fly in inclement weather. No matter how light you make your airframe, an airship is always going to be bulky because of how buoyancy works; to float, it must be lighter than an equal volume of the surrounding fluid. But being less weight is awful in view of winds and storms, and being bulky sucks for achieving any appreciable speed.

So, at best, you're offering the public a mode of transport that is slower than airplanes, takes up more room at an airport, and flights must be canceled if wind gusts along the route get too high, winds that a 777 can punch through with barely a bump. And yet still your airship must slurp tons of fuel to fight wind-resistance and air currents. Who's gonna buy a ticket for that? You wanna get somewhere, you're better off walking or taking a bus.

The nail in the coffin is the lighter-than-air substance. Hydrogen? Expensive and burns, see Hindenburg. Helium? Expensive, planet Earth is running out of the stuff, and retrieving what there is often comes as a byproduct of dirty fossil fuel drilling. And they both leak like mad from whatever container you put it in, especially something lightweight for floating, consequence of being such tiny atoms. Worse, you got to bleed even more of it right out into the atmosphere in order to land. Lighter, more rigid materials don't do shit for this. Dirigibles suck. Own it.

Economically cannot work

[sjbe]

We really didn't.

Yes we really did. Heck we still fly blimps today so it's not as if the economics or performance characteristics of them are a mystery. Every decade or two someone seems to think the laws of physics and economics have been repealed and they take another run at it with predictable results. They have a few uses but passenger transport isn't going to be among them.

If you mean the lack of LTA craft was replaced by the conventional airplanes, you're right. If you mean anything else, like a certain overwrought tragedy, you're missing a lot of the actual harm because of a bright and shiny light.

The Hindenberg was merely the most celebrated of the crashes but there is no lack of others. The Shenandoah, Akron and Macon all were lost to accidents, particularly weather and there are many many more. They cannot fly at all in a stiff breeze, they a slow, they are expensive, and there quite simply are better options both aerial and terrestrial in nearly all circumstances.

Well, you won't let us do trains anymore, so what else is there?

When did I say anything about trains? Trains are demonstrably practical in a wide variety of circumstances, especially for freight but also for passengers. Airships are not practical for either passengers or freight. They have a few niche uses and that is all they will likely ever have.

Re:Jets aren't going away

[Shotgun]

Conceptually, a jet sucks air, heats it, then blows it out the back. A hair dryer is a jet. . . a crappy, low thrust, and inefficient one, but a jet nonetheless. All a high-bypass system does is suck more air which it doesn't heat quite as much. The bypass is just MORE exhaust. It is still all F=ma, with the bypass air being weighted to more 'm' and the "exhaust" air being weighted to more 'a'.