On Thu, 18 Jun 2015 08:15:31 -0400 Meade Dillon via Mercedes
<mercedes@okiebenz.com> wrote:

> 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.

1000 Watts = 3412 BTU/hr
 200 Watts = 682.4 BTU/hr

------- = 190.5

So, it's roughly a factor of 190, not 40 orders of magnitude (= 10^40).



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