Battery power will be constrained by power density of the battery. Biofuel will be constrained by economics. Either one could win. Creating more efficient aircraft will benefit the use of biofuel just as much as the use of battery power.
For me, I’m happy to save the environment, but what gets me truly excited about electric flight is the ability to reduce operating costs, simplify maintenance and increase safety. I sometimes think about if I’d taken all the money I’ve spent on maintenance and compliance over they years and put that into stocks or the real estate market, I’d be a millionaire by now. I gotta be honest, it’s starting to get to me that everything in aviation is r*aping you. It’s getting old. Especially in the category of flying I want to do – long travels in an all-weather capable plane. I wish I was interested in RV’s and stuff like that – I’d be able to save a ton of money – but I’m just not. Aviation is the freedom from airline travel for me.
Obviously, there’s zero infrastructure for electric flight. I saw a clip of the first Pipistrel Alpha Electro in Australia where they did a long cross country by arranging for a diesel GPU to be at some grass field to recharge it at its rural destination. It was a hassle and not at all efficient in the end. No, unless you can recharge an electric plane over the grid, it’s just not such a good idea. But at least with removable batteries, that’s a possibility at a majority of airfields, perhaps with the exception of the most rural ones. Will there be charging stations at FBO’s eventually? 
Biofuel production competes with food production.
If I can’t get fuel to fly, I’ll stop flying.
If I can’t get car fuel, I’ll stop driving.
If I can’t get food, I will be prepared to do anything to get it, once I’m very hungry. I believe many other humans will act similarly.
Perhaps artificial waterpans in deserts can produce oil from microorganisms without competing with food production.
AdamFriach wrote:
my calculations hints that you could quite easily get into the 4-5hr endurance range at a power setting of 30-40%
Care to share these calculations?
Maoraigh wrote:
Biofuel production competes with food production.
Not necessarily. Biofuel can be made from wood for instance. Wood is not food.
Cobalt wrote:
Care to share these calculations?
Oh, I was just doing back-of-the-envelope calcs on a Cirrus-type size.
1. Let’s say MTOW is 4000lbs. With a good carbon fibre construction, I think you can have an empty of about 1500lbs when you remove the piston engine and all the gunk that comes with that. That’s 2500lbs useful.
2. If we accept we can go with a 1:20 power-to-weight ratio, a 4000lbs aircraft would need a 200hp engine. That’s 145kW. Won’t be a speed demon, but she’ll fly.
3. Deduct 400lbs for pilot and passenger. Yes, ideally, it would be great to fill the seats and go the full distance, but most gas powered planes also need to trade fuel for weight, so two passengers and “full tank” in batteries is a reasonable tradeoff. You could have a design where your remove batteries to make up weight for more passengers for shorter distances.
4. This leaves 2100lbs left over for batteries. That’s 954kg’s. Each kg of battery can hold about 250Wh with today’s battery capacity. Thus 954 × 250 = 238kWh battery capacity.
5. If we accept that about 30% power setting is what long range cruise would entice, we’re looking at a motor that needs 0.3 × 145kW = 43kW
6. Divide 238kWh by 43kWh and we have the endurance = 5.5hr, no reserve. Assuming aircraft can make 120kts, that would be a no wind range of 660nm with no reserves.
I haven’t checked the numbers but there must be some basic mistake, because nobody can currently achieve more than a fraction of 1 hour for a large twin.
Subsonic aerodynamics have been pretty well explored by the time WW2 came. Distributing lift is fun but you don’t reduce induced drag (a consequence of producing lift) by spreading it around the airframe.
Perhaps a part of the key is
the engines were run rarely above 30% power in cruise
The problem is that planes fly excruciatingly slowly at 30% power. You will struggle even to hold Vbg – the best-MPG speed. Well, unless “100% power” is some really large figure, which I guess is possible with electric propulsion, so 30% of that is still a lot, corresponding to say an IO540 running at 65% power. But then you aren’t flying a plane at “30% power”.
A plane that’s efficient at these low speeds will have huge long wings – basically a glider. The low wing loading will make for a rough ride even in the slightest turbulence. Public acceptance = zero.
And the slower you go the more headwinds affect you. And on average there is always a headwind; even a pure crosswind has a headwind component. So over a period of time, a “100kt TAS” plane will be averaging say 90kt. Flying at 100kt for any distance, into a common headwind, is painful.
When the speed falls to the speed of a car, almost nobody will bother…
The amount of GA activity is way too small to make it worth setting up battery swapping facilities.
I think the path of progress in electric planes will be something like this
All three of the above will need to be in place even just for achieving the entire PPL training package, with the most basic cross country flights doable. Actually going somewhere, say 500nm with reserves, seems to be a whole order of magnitude away. Remember liquid fuel holds about 50x more energy than batteries (by weight) so even the propulsion efficiency gains (electric motor versus IC engine) don’t help much.
I am working towards getting 3 phase installed at home and it’s a huge hassle, plus a 4 figure cost. Up and down the country, the main take-up will be by champagne socialists 
You can charge a car (or a plane) from existing mains if you drive (or fly) very little.
Peter wrote:
I am working towards getting 3 phase installed at home and it’s a huge hassle, plus a 4 figure cost.
That depends on national electrical installation practise. E.g. in Sweden every house has 3-phase since decades.
France used to run 3 phase to houses, but it stopped decades ago (I saw the ancient 3 phase power points in a house at a little village – Artaix).
I am sure all but the tiniest airfields have 3 phase too (3 phase is standard for power distribution in the countryside) but there is a significant financial barrier in upgrading the power capability from say 100kW (basically, something like 35mm2 conductors) to say 1MW. For a remote countryside location (i.e. most GA airfields ) the upstream work is likely huge as well. Unless subsidised, this is easily into 100s of k. I remember some of this stuff going on 20+ years ago when there was a fashion for what were basically server farms to have duplicate grid connections; they were paying fortunes.
Most GA airfields cannot afford to pay 30k per runway end for GPS approach design. They are certainly not going to pay for this, ahead of it materialising.
Unless of course the utility company does it at taxpayer expense
This really belongs into the electric propulsion thread but the impact is so much bigger if talking about flying serious distances – basically any usage away from basic PPL training. The power to charge the batteries has to come from somewhere, and the scenario of a full charge on a Tesla taking 3 days from a domestic power socket (3kW) is completely infeasible. Anything over an hour will kill the proposition (of commercial usage) completely.
Obviously there are workable scenarios e.g. 10 min flights to islands (another thread).
Peter wrote:
will be by champagne socialists
Why is it seen as “socialist” to want to drive an efficient car with low running costs with much lower mess/maintenance/need to go to petrol stations? If I had off-street parking, I’d have an electric car right now not due to any “social” issues but because I’d never have to visit a petrol station ever again (my absolute least favorite retail experience).
On the other points, it’s almost as if the right wing see inefficiency and pollution as virtuous. I’ve never understood this.
