Department of Agriculture

[kandrathe]

Then, assuming that this project would be a "pretty big frikken deal", you wonder if they could amp up the maximum output? Even a 10% improvement in quality, to 46.2% would have pretty drastic results:

.462 X 12 X 150 = 831.6 WHpD
...

I think you are confused on the 42% -- that is in a given 12 hour day, the sun is not always in the ideal position relative to your collector panel -- even if you could track the sun to always be perpendicular, in the morning and evening the sun is penetrating more atmosphere to get to you. Hence, why you sun burn more during the times just before to just after noon. The efficiency number is reflected in the 150 W out of 1000W possible (15%) -- 10% better would yield 165 W per sq. meter * (12 hours * 42% available sun) = also 831 W hours / day.

There are more efficient cells -- they just are made from rare materials that put the costs into the stratosphere. Gallium arsenide multijunction for example. The Shockley-Queisser limit for the theoretical maximum efficiency of a solar cell peaks at 33% for single junction cells. They use them on things like the Mars rover where solar cell cost is not a concern relative to the cost of getting a rover to another planet.