Primarily for general aviation discussion, but other aviation topics are also welcome.
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By PaulB
#1662381
I know we've covered this before, but this seems to be in the news recently



For those with a Twitter aversion (which should really be any sane person) the tweet merely send you tho this link

https://www.rolls-royce.com/media/our-s ... accel.aspx

I admit I'm not an aviation junkie, which explains why i don't know what I'm about to ask.....

In the early days of aviation, even airliners had propellors. However, the jet engine quickly cast the turbo-prop into obsolescence. However, most of the electric aeroplanes that you see have propellors.

Where is the electric motor that can compete with the jet engine?
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By akg1486
#1662397
PaulB wrote:Where is the electric motor that can compete with the jet engine?

Right now? Nowhere. But that's not the same as saying there won't ever be one.

One would think that the solution to an emission-free fuel would be an engineered photosynthesis that generates carbohydrates from the carbon dioxide in the air. In essence, something that mimics plants. But I've never heard anything about that. In the meantime, there's plenty of work being done to create (jet) fuel from biological sources such as waste material from the lumber and paper industries.
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By Genghis the Engineer
#1662402
Right now, there is probably nothing that electric aircraft can do better than a good IC aircraft.

But, we're heading into the overlap, and it seems highly likely that within the next 10-20 years there will be roles where electric, and particularly hybrid, aircraft become increasingly useful. In the short term we'll be looking at training aircraft.

A presentation on the topic is here, for those who use facebook, from November's RAeS GA design conference...

https://m.facebook.com/groups/285438698 ... 0830726334

G
User avatar
By PaulB
#1662403
akg1486 wrote:One would think that the solution to an emission-free fuel would be an engineered photosynthesis that generates carbohydrates from the carbon dioxide in the air.


I'd guess that you may as well cut out the (photosynthesis) middleman and just create energy direct from sunlight.
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By akg1486
#1662422
PaulB wrote:
akg1486 wrote:One would think that the solution to an emission-free fuel would be an engineered photosynthesis that generates carbohydrates from the carbon dioxide in the air.


I'd guess that you may as well cut out the (photosynthesis) middleman and just create energy direct from sunlight.

The energy density in carbohydrate fuels is higher than batteries. And they are easy to transport. Trees are efficient, but grow slowly. An industrial solution could be faster. The energy source could be direct sunlight or possibly artificial LED-light powered by wind- or hydroelectricity.

But I'm no chemist. There may be fundamental reasons of science for why it doesn't work.
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By Genghis the Engineer
#1662428
akg1486 wrote:
PaulB wrote:
akg1486 wrote:One would think that the solution to an emission-free fuel would be an engineered photosynthesis that generates carbohydrates from the carbon dioxide in the air.


I'd guess that you may as well cut out the (photosynthesis) middleman and just create energy direct from sunlight.

The energy density in carbohydrate fuels is higher than batteries. And they are easy to transport. Trees are efficient, but grow slowly. An industrial solution could be faster. The energy source could be direct sunlight or possibly artificial LED-light powered by wind- or hydroelectricity.

But I'm no chemist. There may be fundamental reasons of science for why it doesn't work.


Numbers supporting and expanding on your main assertion are in that presentation I posted.

George Olah, a Nobel Chemist has been advocating a switch to Methanol - that is around 30% heavier per energy stored than petroleum fuels, and the technology for creating this is still pretty inefficient - but there are ways and means.

My money is on a dozen or more different biofuel sources, with some new technology about mixing and quality assuring them going a fair way towards reducing the emissions on big jets. At our little aeroplane scale, electric is probably the solution - but needs steady improvements in battery life and cost particularly - energy density would also be a big bonus. Also however be aware that whilst the use of battery technology will save on greenhouse gas emissions, the chemicals used in those batteries generate a lot of nasty waste in production.

In between, hybrid/electric will probably be part of everybody's solutions - maybe starting at about the light/medium twin size and stretching upwards.

G
By avtur3
#1662433
If you look at how electric propulsion has developed in model flying, including hi-performance ducted fans, then it is only a matter of time before motor and battery technology can be scaled up to provide acceptable levels of performance suitable for GA aircraft. Some models are flying at 50% and even 60% of full size, so I'd suggest it is more a matter of when than if.

Undoubtedly there will be "range anxiety" in early attempts (as with automotive) but I don't doubt development will continue in the right direction.
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By Sooty25
#1662436
akg1486 wrote:
Sooty25 wrote:maybe Dyson should get involved.

Wouldn't his solution suck?


based on the quality of his vacuum cleaners, yes!

from an operational point, just swap the wires!
User avatar
By akg1486
#1662439
Genghis the Engineer wrote:At our little aeroplane scale, electric is probably the solution - but needs steady improvements in battery life and cost particularly - energy density would also be a big bonus.

Sorry for the massive snip in an interesting post.

Our club, Aeroklubben i Göteborg, is slated to get an electric Pipistrel sometime 2019. It will be owned by the airport, mostly paid for by taxpayer subsidies, operated by the club and fuelled by a solar farm just adjacent to the field. We'll get one more charging station that will be placed at an airfield around 30 minutes away. We can go there, have a coffee while it charges and then go back. Or we can do local bimbles; the range is some 40 minutes, AIUI.

The developer who owns the airfield, and who was heavily involved in these disucssions, recently sold it to another real estate company. Hopefully the Pipistrel deal lives on; their CEO is a PPL student at our club's school.

The wet rental cost, if you can say "wet" for battery powered aircraft, is estimated to be less than half per hour when compared to the C172 and PA28s we otherwise fly.

The national transport agency has given assurances that an SEP rating will be valid, even if there are no pistons involved. But as always with these agencies, you never know until you know for sure.

I'll post something here if and when everything is done and it's available to us members to fly. Stay tuned.