The key point that I am trying to drive home is the limit on the amount of
solar power available.  This is a hard limit: ~1000 watts/square meter is
the peak under ideal conditions.  A more usable number is 200 watts during
daytime, which takes into account average cloud cover and reduced energy
reaching ground when the sun is low in the sky.

By comparison, 1 gallon of diesel has the potential energy of 130,000
BTU's.  200 watts of solar power is the equivalent of about 3400 BTU's /
hour.  That ~40 order of magnatude difference is why we drive cars and
trucks with internal combustion engines and why we don't have solar cars
(or airplanes) that can do useful things.  Diesel has ~40 times more energy
density than solar power, comparing one gallon of diesel to one square
meter of solar energy.

Charleston SC

On Thu, Jun 18, 2015 at 2:11 AM, fmiser via Mercedes <>

>   As
> pointed out, even 100% efficiency from the panels would not
> be enough to sustain flight except at high noon in the
> tropics on a sunny day.

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