Electric Airplanes!!

Those 14 engines have propellers that are used for takeoff and landing - but stowed for cruise. Narrower wing - less drag at cruise.

 

This is research program and will be a derivative of an already flying aircraft.
P2006T | Tecnam
NASA is going to put a new wing on it with a bunch of electric engines.

 

The article refers to the plane as a hybrid yet makes no mention of any fossil fuel powered power units, which I find a bit odd.

I'd love to know more details about the batteries and motors. I'd also like to know what materials are being used in the plane's construction/modification to keep the weight down...styrofoam? LOL

 

The reason for a bunch of small motors is that high rpm gets you higher power to weight ratio in conventional electric motors. But in order to get high rpm down to prop frendily speeds you still need a gearbox that costs money, weight and efficiency.

Siemens just announced a 250 kw (continuous) electric motor that weighs about 100 lbs. It has an output rpm of 2500 so there is no need for a reduction gearbox. This is a breakthrough in that it doubles the power to weight ratio for electric motors compared to those being used in electric cars.

The place where it all falls apart is the battery in terms of both energy density and power density. In order to have a 1 hour endurance with current technology batteries at about 200 kw you need 2500 pounds of batteries.

For a normal airplane like a C182 you could basically have zero payload and carry just the pilot for one hour. A really slick airplane might be able to go 250 miles on a charge, but the weight of the batteries is the limiting factor in any attempt to do an electric airplane.

Hybrids make no sense because you're going to lose 5% making all the power electric and then another 5% making back into shaft power, compared to 2% lost in a typical gearbox.

You'll need to double energy density of batteries to make anything that you could even use, and to make something close to a gas powered airplane in terms of range you'll need to more than quadruple battery energy density to make a real airplane.

And lastly you have to compare apples and apples. If you go to extraordinary lengths to cut weight from the electric airplane you have to compare it with a similar technology fossil fueled airplane to make an honest comparison.

 

I actually can see electric airplanes in the future.

They just set up a self driving single passenger quad copter testing area north of Las Vegas.

 

I read about an electric trainer from a European manufacturer (can't remember which one right now), which actually sounded pretty interesting. It had about a 1+30 endurance, which is just barely enough to be a functional trainer, but it was incredibly cheap to operate.

 

Its a research project.

Many home-built aircraft and other experimental aircraft, e.g. think 'Rutan', use foam in the construction.
https://en.wikipedia.org/wiki/Scaled_Composites_ARES

 

And the batteries don't get lighter as you drain power from them. Right now, the more fuel I burn, the faster I go.

The only way electric airplanes make sense is if they get power from the sun while flying. A battery is a store of energy. A tank of gas is a store of energy. Nothing has the energy density of fossil fuels.

 

Not much energy available from solar power... The amount of energy coming from sunlight is about a kilowatt of energy per square meter.. A wing with 2 meters of chord and a 20 meter span (typical of a light airplane) is worth only about 40 kw (about 53.6 hp) and that assumes 100% conversion efficiency. Real solar cells at best have about 25% efficiency, so if you cover a typical wing with solar cells you're going to get about 14 hp, and that assumes you're taking off on a sunny day and flying when the sun is high in the sky.. 14 hp isn't going to fly much of an airplane. Perhaps something that looks more like a sailplane, with a lot more wing area and doesn't need much power could get some help from solar cells, but now it isn't going to make a real airplane.

So if you have a huge wing area then you can get some power to fly slowly, and there's an airplane that has flown around the world this way, but it isn't even anywhere near practical.

 

Yeah, that's what I said.

So to keep going, even if batteries did have the energy density of JetA I still think it's a downgrade. Batteries weigh too much.

 

Not yet...

 

lol, to date it has demonstrated that a balloon is more expedient for flying around the world.

 

Probably true... If you get up high enough you can take advantage of the prevailing wind, but the Solar Impulse is doing it, just very slowly.. I had forgotten that they started the "around the world" flight in the middle east, and they're more than half way around as we speak. Just saw a blurb that they were over the Atlantic right now...

At sea level this has a max speed of 41 kts, and at altitude it can do 77 kts... Obviously it really can't fly into any appreciable wind, but if you get up to 15000 ft and are doing 77 kts plus a 50 knot tailwind you could cover a bit of ground...

Nice stunt, but as all have noted before, not a very practical solution..

Now that electric cars have become a reality and range of 200 miles is commonly achieved some folks are thinking that electric airplanes aren't far behind, but that's just not the case..

When you calculate the energy in a pound of fuel, and compare that with the energy density of batteries, the numbers sober you up real fast. Even with a 30% conversion of energy content to power, good old fossil fuel beats the heck out of any other way to try to store energy.