Siemens and Airbus To Push Electric Aviation Engines (networkworld.com)

coondoggie quotes a report from Networkworld: Siemens and Airbus teamed up today to develop electric and hybrid electric/combustion engines for commercial and private aircraft. The companies said they would amass a joint development team of about 200 employees that would jointly develop prototypes for various propulsion systems with power classes ranging from a few 100 kilowatts up to 10 and more megawatts, for short, local trips with aircraft below 100 seats, helicopters or unmanned aircraft up to classic short and medium-range flights. Hybrid-electric propulsion systems can significantly reduce fuel consumption of aircraft and reduce noise. European emissions targets aim for a 75% reduction of CO2 emissions by 2050. These ambitious goals cannot be achieved by conventional technologies, the companies stated. Airbus has developed a 2-seat electrically powered aircraft, known as the E-Fan. Siemens too has been developing an electric aircraft engine.

Comments

Energy density per kg

[NotInHere]

Is the energy density per kg of batteries really that much better than the energy density of methane gas, or liquid hydrogen?

Re:Energy density per kg

[Anonymous Coward]

Quite the opposite, but that's okay; the sun and wind are free! Slap some solar panels on the body and a windmill on the nose, and the plane will have all the energy it could ever use, while providing lots of jobs. It will never actually leave the runway, but that is a minor point, right? /s

Many of the "green" ideas are attractive, and superficially plausible to the layman. Ultimately though, reality has the final word, and the numbers just don't work. At a small scale, obscene subsides can partially compensate, but those technologies have no hope of achieving their ideals. Energy density is a real thing, and it matters. Scale also matters. Batteries are not even remotely capable enough for aviation applications, much less providing backup for a "renewable" grid.

The only practical technology at scale is the one that the crusaders are so eager to dismiss. Nuclear has an amazing energy density, with a very small environmental footprint in terms of land and resources. Also things which matter, but that the so-called "greens" are happy to sacrifice in enormous quantities in pursuit of their ideology. (Obviously, we aren't putting reactors on planes, but the heat can be used to produce synthetic fuels for planes and other transportation.)

Re:Energy density per kg

[Brett Buck]

Not at all. Kerosene is a very good fuel.

    The problem with methane, or even worse, liquid hydrogen, is that while the energy content per pound is good, the energy content per unit volume it terrible. That means very large fuel tanks, meaning more drag and more airframe mass, which leads you to making the wings bigger, which leads to you needing and even bigger tank, which leads to more drag, etc. Liquid hydrogen is one of the worst fuels imaginable for an airplane.

      Liquid hydrogen is only about 4.4 lbs/ cu ft and lerosene is something like 55 lb/cu ft. You simply can't make the airplane big enough.

Re:Energy density per kg

[Harlequin80]

Energy density for liquid hydrogen needs to be measure in MJ/L for you to really see why it sucks to use. LH2 is 5.6MJ/L and a LiPo is 2.28 MJ/L.

While batteries are probably a long way from being capable of driving aircraft liquid hydrogen is a non starter because it takes up too much space. Standard Kerosene jet fuel has an energy density of 37MJ/L and has none of the painful storage or explosive risks of hydrogen.

Re:Energy density per kg

[blindseer]

There are other advantages to hydrogen as a transport fuel besides the tree-hugger appeal.

There are also many disadvantages. Hydrogen eats steel and aluminum. It has a much poorer energy density by weight and volume than jet fuel. I could come up with more if I wasn't so tired right now but those two alone really kills hydrogen as aviation fuel, especially if derived from a very useful fuel like natural gas (which is mostly just methane) or propane.

Since the entire goal of using this system is to improve the efficiency of burning the jet fuel then producing hydrogen from a fossil fuel sounds like you'd be going backwards. Part of the energy of the fuel is in the carbon hydrogen bonds, if you break those bonds on the ground to make the hydrogen then it is not contributing to the movement of the plane in the air.

Unless you can show me where I've gone wrong, or something I missed, I still think that hydrogen fuel for airplanes is a very bad idea with the possible exception of hydrogen derived from cracking water with power derived from nuclear fission. I won't even consider wind, solar, or geothermal good alternatives since they currently cost more than nuclear power.

Nope. When you burn anything in an internal combustion engine, more than half of the energy from the reaction is lost as exhaust heat.

That would be relevant if the aircraft in question did not have an internal combustion engine. What they want to do is run a generator with an internal combustion engine, then use that electricity to run a motor that drives a ducted fan. While you caught me on the thermal efficiency angle since they claim to reduce fuel consumption by 25% with this system they also hope to gain on efficiency by having batteries be part of the airplane structure. That is not a simple task and they know it.

Their claim of these efficiency gains comes from the hope that they can develop an electric storage system suited to power an aircraft. Since we have not even found a suitable storage system for the much simpler problem of electric cars and trains I believe they are not going to find that solution soon. If they do then perhaps we can see internal combustion cars get beat out by pure electric and electric hybrid cars on every price point, not just luxury cars and tree hugger magnets.

If I use the definition of efficiency to refer to it's cost and complexity, and not it's ability to convert fuel to forward motion, then a common jet engine is more efficient than the hybrid. For an airline this is a make or break matter, they run on total cost of ownership. For a personal vehicle this might not be so critical since a hybrid might offer other advantages such as comfort, performance, or just bragging rights, that a common jet engine would not have.

Re:Energy density per kg

[Anonymous Coward]

Liquid Hydrogen would work well in Commercial jets - massive reduction in fuel mass reduces structure weights. It doesn't matter much that have to store fuel in fuselage tanks (just make a bigger fuselage), because so much of plane power use is to lift 1/3rd of takeoff mass in kerosene and bigger engines to accelerate it at takeoff.

EG 787-8 takeoff kerosene is 130tonnes dry, 100tonnes out of total 230tonnes needing about 125m for average mission weight of 180 tonnes.
LH2 would be about 140 tonnes for 25% power or energy saving, needing about 24 tonnes of fuel (engine and landing gear and structure would be lightened) and needing about 350m (tanks about 3.5 tonnes) in a fuselage length of 14m (which is roughly difference between the 787-8 and the 787-10).

If necessary you can just make your jet fly higher to reduce relative size of fuselage compared to larger wings, gives benefit of more internal volume for comfort.

Liquid Hydrogen is probably the best fuel for supersonic use - as it cuts fuel weight by about 75% (about 40-50% of takeoff weight) lowering structural loads and weights, lowering thrust needed proportionally and lowering boom noise by up to half (perhaps more if flying higher), and can easily give global range (eg see lapcat). Also possible advantages in improving gas turbine efficiency through pre or intercooling or using a superheated rankine cycle on the LH2 for even bigger fuel savings. Can also cool passengers.

LH2 would also be fine in Trucks and Ships. What it really sucks at is intermittent small applications like cars motorbikes etc where small scale long term storage issues and close proximity to humans make it dangerous. Fortunately batteries are good enough for that.

So in a post fossil fuel world LH2 is pretty attractive for all sorts of transport, as long as we can find cheap methods of manufacture (ideally nuclear or perhaps southern ocean floating wind turbines or around Antartica to use collosal power available in katabatic winds there.)

Re:Energy density per kg

[phayes]

Aircraft are only now beginning to use turbines to generate electricity which is then used in electric motors but is is a very widely used technology in many ships -- especially large warships.

A first application for adding an electric engine to the tail end of an airliner to re-energize the fuselage boundary layer airflow. As the plane flies through the air it slows down some of the air which ends up as drag. By putting a ring around the end of the fuselage directing the boundary layer airflow to an electric engine powered from the main turbines, drag goes down to the point that smaller diameter engines are needed (also diminishing drag). The major design change needed is that with the ring and engine, the horizontal stabilizers must be moved to a T tail.

Both NASA & Airbus are studying this for future designs: see here.

Use the US Navy seawater to jet fuel tech instead

[blindseer]

The US Navy has been experimenting with the technology that can extract carbon and hydrogen from seawater, connect those elements together in long hydrocarbon chains, with heat and electricity from nuclear fission. They've shown it works. This technology makes aircraft carbon neutral without any modifications to the aircraft itself.

The use of an electric hybrid aircraft would still require hydrocarbon fuels. If that fuel is dug from the ground then it is still adding carbon to the air. I suppose we could combine the two technologies, synthetic hydrocarbons and hybrid planes, but it would still require that we invest in synthetic hydrocarbons.

These electric planes are interesting I suppose but they would not solve the problem like synthesized fuels would.

Re:not going to work

[MightyYar]

Not to mention that the hydrocarbon-fueled aircraft gets lighter and more efficient as it burns fuel, while batteries stay the same weight that they were at takeoff.

Who said it was battery powered?

[WoTG]

This sounds a lot like the diesel-electric "hybrids" that power trains. Diesel generators generate electricity to power electric propellers. It makes sense to me... of course I know nothing about this stuff. If my assumption is correct, a nice benefit would be that aircraft could use cheaper fuel rather than jet fuel (which I assume costs more per litre... I think it does, if only because of lower volumes).

Re:not going to work

[Lisandro]

Yeah, but to a much lesser degree. Aircraft engines are usually optimized for a given altitude range - normal piston engines decrease power with altitude. Turbochargers improved on this, but they suffer the same issue. Turbofan engines used on airliners have peak efficiency at cruise altitude but suck when flying low.

In general, air density is the main factor impacting aircraft performance, because it impacts on three separate thing: how the engine runs, how much lift can the wings generate and how much air can a propeller push or a jet can suck. Of those, the first one is by far the most important, as it in it can compensate (to a degree) for the rest.

Re:Use the US Navy seawater to jet fuel tech inste

[blindseer]

And you failed to understand what a Hybrid Electric System is. It's a Combination of Internal Combustion engine with an Electric Drive Motor

A true hybrid allows for power from more than one energy source. An internal combustion engine driving a generator, and the generator driving a motor, is not a hybrid. That would make an electric drive train.

The Fucking Chevy Volt uses such a setup.

No the fucking Chevy Volt has a battery pack and a mechanical transmission. While it might not be able to go in reverse or slow speeds without the electric drive train it is capable of going highway speeds without it. These proposed aircraft do not claim to have a mechanical link from the on board internal combustion engine to the ducted fans. If they did then I might be impressed since that would be an engineering feat.

Locomotives are also Hybrids

Very few trains are true hybrids. Some are capable of using a "third rail" for power, those are hybrids. Even using capacitors or batteries on board would not make them hybrids since all the energy to drive the train comes from the fuel oil.

many of the latest cruise ships are using the same tech

Yes they do, but unless those ships use under water extension cables to power the ship at sea they are still just diesel powered with electric drives.

so why in hell can't you get it through your tiny little mind that Hybrid does not mean Fuel Cells and Batteries.

Because I actually looked up what "hybrid" means.