jimp wrote

In rough numbers, you get about 1 kW/m^2 of energy from the sun on
a clear day.

Current conversion technology is about 22% at best.

Technologies in the works are promising 50-60% (the check is in the
mail and I will respect you in the morning).

One presumes a sailplane is going to spend most of its time sailing
and only using the motor (with batteries) to get off the ground
and occassionaly cruise between thermals.

So most of the time you are just charging the batteries.

That is why I specified cruising with the motor without thermals; to get a
feel on how the extra surface area and high aspect ratio (efficiency) would
mimic a cross country, motor cruise.
--
Jim in NC