Fusion is the way to go anyways. It’s, in my eyes, the definite key technology for advancing the human race. Too bad that it’s always “20 years in the future” for about 70 years now…
Plant leaves split water into hydrogen and oxygen using light to excite electrons, which leave their shells and combine with the 10-7 H+ ions, temporarily separated from their OH- partner.
The H then join NADP to form NADPH2.
Could chloroplasts be genetically engineered to produce some hydrogen, while just producing. the minimum food needed for their own needs.
The Pipistrel electic aircraft works (just about, endurance <1hr) because it is just about possible to work around the weight issues with a particular configuration – that of the two-seat ultralight in the 500-600kg MTOW range.
Compare it to a traditional 2-seat avgas burner (such as the PA17 I fly, MTOW 521kg) and you can work around the weight issue in three ways.
1) Modern design and materials. With a small aircraft the actual kg saved this way is a significant % of the overall weight.
2) You get a relatively big benefit from removing the engine. In a small aircraft the 4-cyl Lyco/Conti is a very significant % of the overall weight, so when you swap it out for a 20kg electric motor you are freeing up a lot of kg as a proportion of the target MTOW.
3) Small aircraft have small fuel tanks anyway, so you are not trying to replace 150kg of fuel with batteries, more like you’re looking to replace 50kg of fuel (and certainly not all of it anyway).
So it gets quite close to working out. Your payload and endurance are heavily compromised compared to the avgas equivalent – some would say to the point of making it not much more than a novelty – but you do have a functioning aircraft.
The problem is, it doesn’t work as you try to scale it up. Once you’re looking at a 1-2 ton 4-seat aircraft those factors start to change – you don’t save such a large % with your modern design and materials, the engine is not such a high % of overall weight so swapping it out for an electric motor doesn’t free up that much as a %, and the amount of fuel you need to replace with batteries is much greater.
There’s no getting away from the fact that the thrust a Lyco/Conti delivers from 200 litres of avgas weighs, in battery form, about a ton.
Graham wrote:
The problem is, it doesn’t work as you try to scale it up.
So why don’t everyone who are working with larger aircraft designs understand this? Or maybe they understand something that you do not?
Sometimes the simple answer is the right one e.g.
) on the family tableA casual walk around Aero Friedrichshafen makes it clear the majority of electric plane projects are firmly in the above categories – one or both.
Even with a solid 1hr endurance, and charging facilities everywhere (and we are many years away from that), you still have the basic issues of
Also remember that if you want say 5x the range then regardless of battery technology you will need 5x the charger power for any given charging time, and we are already looking at 100s of kW per aircraft, for a “fast” charge. Do a google/images for say a 10MW transformer. And the power lines needed to feed it; at 33kV 3 phase that works out at 25mm2 wires (100A per phase). Yeah, and you really would need 33kV. Getting that connected up is gonna cost the average airfield way way more than getting GPS approaches 
It will cost roughtly the same as an ILS – hundreds of k. I am looking at ~5k just to get 3 phase 100A run to my house, about 15m distance. Then chuck in the safety / vandalism / security aspects of this installation, and you are looking at a permanent Flugleiter scenario.
There are just so many things which don’t even begin to add up. It’s like the “if everybody in the street gets a Tesla and drives it 100km a day, the transformer at the end of the street will explode” argument, which is currently probably false, in most streets, because most people aren’t doing 100km/day, except that in GA people are actually flying at cruise power the whole time.
I think that for this decade, for any serious transport machines we’re going to be seeing hybrid solutions at best.
As to all-electric, you are probably right that there quite a few phantom, subsidy/equity scooping projects out there (Lilium?)
Or maybe not, and the one below may be a bit more serious? They even claim to have a launch customer, Cape Air. Although that’s probably a potential customer only. And we haven’t seen real flight data yet.
@Airborne_Again is anyone really working on any serious larger electric aircraft designs that aren’t a case of:
a) burning research money,
b) spending a bit to bolster green credentials, or
c) having the aircraft design ready for when the miracle battery comes along?
This isn’t a question of aircraft design. It’s about batteries.
No, I think that design is a big part of it and that sticking a motor and batteries in an existing airframe is doomed to mediocrity.
Electric flight makes VTOL much easier but getting a decent range, harder. VTOL should mean that you need lower reserves, and also that you can use a smaller more efficient wing because you can design it for efficiency during the cruise rather than during the landing. I think a well designed electric plane should have an useful niche but will look different and be used differently (I.e. be complementary to) our existing aircraft.
There are battery chemistries e.g. Aluminium-air that have a good enough theoretical energy density to give conventional aircraft a decent range, but I don’t know when if ever they will be ready.
kwlf wrote:
Electric flight makes VTOL much easier but getting a decent range, harder.
IMO too much focus is put on a 1 to 1 replacement of the typical B-737. That may never happen. What I think is more realistic is electric aircraft will create their own niches. Maybe completely new niches that no one today has thought of yet. There may never be a 1 to 1 replacement. The “737s” may simply be made obsolete by a different industry altogether. The aircraft in that new industry may not be able to compete with a 737, but they don’t need to.
Peter wrote:
Sometimes the simple answer is the right one e.g.there is a lot of research money to be had, especially from Brussels, and everybody needs to put bread and butter (or veg ) on the family table
spending say 1M on some electric project gets you way more press coverage, and way more green credentials, than spending 1M on advertising
That’s what you often say about development projects but I’m not quite as cynical.
