Andy, even if the solar collectors got better, the batteries are the primary component that is sorely lacking; and will be for most probably the rest of our lives.

I help people with getting off grid all the time, (installing solar, wind & hydro) and they all start off saying the same thing; "how many panels do I need"?

The question REALLY needs to start with "how big of a battery do I need to accommodate the amperage I'm going to use on a regular basis w/o killing the battery from overuse?

Then, add solar panels, LOTS of them, until you make enough power on December 21st if you're in the Northern Hemisphere; June 21st in the southern. Just like there's never been a problem having too much horsepower in an airplane, there's never been a problem with having too many solar panels, but there's always a problem associated with not having enough.
Fwiw-
Chris

So, has anyone heard anything about Bye Aerospace recently?
I caught a blurb that Sun Flyer 2 is up and flying. But no specs or details.

Tim

Hi Tim,

I stopped in the Sun Flyer booth at Oshkosh. They completed first flight in April and had some spec sheets available. This aircraft is being designed initially for the training market. The engine weight was basically replaced with batteries. Up to 3 hour duration if I remember right.

Here is a link: http://sunflyer.com/

That's how we do it - circled in red is the extension cord. Why not the same for airplanes? How hard can it be?

I have been through the website, rather sparse in terms of information and status.
Too bad they have not provided more information. Oh well, I think they are also stuck on waiting for the Part 23 changes, who knows when those will happen.

Tim

Ah, 18.7-20.6 max glide ratio. That's getting into motor glider territory and it makes sense for an electric airplane- or a 100hp gasoline airplane with a 10 gallon fuel tank.

(I'm not trying to make a pro or con statement about the concept, just a technical observation.)

It has regenerative braking (propeller can drive the motor as a generator to recharge the battery). That's a nice plus for slightly extending the range but more importantly it eliminates the need for spoilers or speedbrakes- which are otherwise necessary for that kind of glide ratio.

It would be strange that when on the ground and stopped waiting to taxi or take off that the prop stops. With the electric airplane, this will be normal operation according to the Sun Flyer reps.

Having fast-charging stations at FBOs is going to be another thing that will need to be dealt with for this to be used beyond training. Power management will take on new meaning...imagine being on your first solo cross-country and figuring out you only have "x" minutes of power left and the airport doesn't have a charger.

Carry an extension cord, and have a built in slow charger. Would not weigh much, just very annoying.

Tim

or...if the charger is heavy...you aren't going to be able to fly very far with any battery tech on the horizon, so just have one of your kids throw the charger in their car and make the short drive to charge you up at your first charging stop.

or...if the charger is heavy...you aren't going to be able to fly very far with any battery tech on the horizon, so just have one of your kids throw the charger in their car and make the short drive to charge you up at your first charging stop.

I spoke with Mrs. Bye at Airventure. She said they envision a series of supercharger stations located at FBOs across the U.S. for charging with no on-board provisions.

However, some of the numbers don't add up - cost per hour, battery weight / density etc. Their stated cost / hour rate for electricity is $3.00. With a U.S. average of $0.13/kWh, that equates to 23 kWh. Could you fly a 1900 pound plane at 70 knots on ~25 horsepower?

In this spreadsheet, you can see just how little the Pipistrel Taurus G4, the NASA CAFE Foundation record holder, uses in terms of energy. You can see it hits over 400mpg, compared to the best piston powered entrant which could only muster about 93mpg (still impressive). This is also almost 10 years ago, so who knows what the stats would be today?

https://cafe.foundation/v2/gfc_2011_results.html

So, if you take into the account that an electric plane can be 4x more efficient in its use of power (due to electric motor efficiency), then it's also obvious to see that battery capacity never has to meet the energy storage of fuel. It only needs to meet a quarter of it. Yes, we are nowhere near that yet, but it's also not impossible that we will be sooner rather than later.

If I was a stock broker, I would not be betting short on electrical propulsion. I would bet short on oil.

Actually, I think drag is a larger factor. Cooling drag for the avgas engine is a major penalty in performance.

Tim

Actually, I think drag is a larger factor. Cooling drag for the avgas engine is a major penalty in performance.

Tim

Well... yes.

1900lbs at 70 kts at 20:1 L:D is between 20-21 hp. Add about 20% to take into account efficiency losses and there ya go.