Well I found that group that had developed high efficiency GaAs(gallium
arsenide as appose to silicon) solar cells. They have a large contract
to develope for China's 1 - hectre-size (2.5 acres or 10,000 square
meters) greenhouses, solar systems to power them. This is currently
under developement, so maybe in a year or two they'll have the
technology to make solar systems commercially viable for GH of 1000 sq
feet or more.

Check out their web site.

http://www.jxcrystals.com/

What's even more interesting is they already have the technology, but
so far not the demand, to convert IR energy to electricity. This means
that the it can convert the wasted heat energy (mostly IR) from
furnaces to electricity.

So if you're interested in planning for tomorrow solar technology,
learn how from these folks.

Mike