Primarily for general aviation discussion, but other aviation topics are also welcome.
By golfcharlie
#1576342
I reckon that this experimental project is likely to go through a few iterations before it ends up as something viable. My guess is, that the project will have to face the fundamental problem that an aeroplane requires a lot of phase one power to taxi, take-off and climb to cruise speed and altitude, all with a payload. Once it gets there, it will need a lot less energy to keep it going in phase two cruise, followed by a descent, approach and landing (where it will need reserves of gas turbine power for a possible phase three go-around).
Given this scenario, it would seem likely they will go for gas turbine-powered phase one, and then switch to electric power either from batteries or an on-board generator of some kind (APU?). Interesting design challenge.
The energy balance will determine the design outcome.
One possibility might be liquid hydrogen + fuel cell, but I personally would not fancy the fire risk.
By malcolmfrost
#1576344
I would see your Phase one as using electric power for taxi (500 kg fuel) followed by assisting the turbines for take off, enabling reduced power/noise or improving climb rate.
All very interesting.
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By Genghis the Engineer
FLYER Club Member  FLYER Club Member
#1576358
neilld wrote:I have to say I am completely baffled by this concept.
For a start, the 2MW generator will require a greater than 2MW gas turbine (due to generator efficiency being less than 100%) in order to drive the 2MW electric motor which will have an electrical input of greater than 2MW (due to the motor efficiency being less than 100%).
The aircraft will have to carry sufficient fuel for the gas turbine.
It is not clear what the energy store of (I assume 2 MWh - not 2MW) will be but if it's batteries then, assuming the current projected best energy density of 0.4 kWh/kg (for LiPo), then the 2MWh store will have a mass of c. 5 tonnes (per engine), this in addition to the mass of fuel required for the above mentioned gas turbine.
Electrical hybrid solutions work in the automotive world where range extender functionality is required but the mission profile in aviation (either GA or commercial) is totally different requiring continuous high power for most of the mission.
I can only assume that the joint resources of Airbus, Siemens and RR have something special up their combined sleeves. (Although committing the schoolboy error of quoting Energy storage in units of Power doesn't inspire much confidence)


I think that the companies are interested in learning how far they can *really* go with these various technologies, for purposes of then having a much deeper understanding of how to integrate electric propulsion, high power supply systems, and so-on into a large airframe. As such, it has a lot of value - but if this ever leads to an in-service electric BAe-146, I'll happily eat my favourite tweed cap.

G
By neilld
#1576380
kanga wrote:.. and Mr Trump assured voters in West Virginia that there was a bright future in coal .. :)

OK there's always an exception.

Genghis the Engineer wrote: - but if this ever leads to an in-service electric BAe-146, I'll happily eat my favourite tweed cap.
G
[/quote]

Save some for me please
By ChrisRowland
#1576386
Coal worked well for something like 100 years, to be replaced by oil, then gas and now people are moving to solar and wind power - what I think of as fusion power. Of course, if your time scale is long enough coal and oil are also fusion power.
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By Dave W
FLYER Club Member  FLYER Club Member
#1577201
From that article, this:


Plus this:

Saft Batteries wrote:A Li-S battery uses very light active materials: sulphur in the positive electrode and metallic lithium as the negative electrode. This is why its theoretical energy density is extraordinarily high: four times greater than that of Li-ion.

(My bold)

Doesn't quite equate with this, from the RAeS Proceedings linked a couple of posts above (Prof Turner from Bath Uni, whose very good presentation was noted by @neilld earlier):



Doubling of energy density in batteries is impressive in itself, but relatively speaking (for these applications) it is doubling an already low number in comparison with non-battery technologies.

There are evidently going to be several suitable applications for battery technology, or other methods of electrical power generation/storage such as Hydrogen and fuel cells, but primary propulsion for airliners seems to me very unlikely.

The other issue I have with batteries in GA aircraft is that you'll be flying close to maximum AUM all the time. That's not inherently a show-stopper, but it does limit flexibility quite considerably.
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By Europaul383
#1577240
Dave W wrote:
Saft Battries wrote:A Li-S battery uses very light active materials: sulphur in the positive electrode and metallic lithium as the negative electrode. This is why its theoretical energy density is extraordinarily high: four times greater than that of Li-ion.
(My bold)

The late Chris Kelleher told me (one day, cleaning the club Chipmunk) that they were getting remarkable yields (and 90 - 100 recharge cycles) from Li-S batteries in the QinetiQ Zephyr. He could quote MJ/kg figures off the top of his head, but I'm afraid I can't recall them (and I'd probably have to eat you if I told you).

Footnote: he named it after the RAE Zephyr, because he could. :D