Thanks Freebeard :-)
And back to solar panels...
Multi junction are too expensive, despite get 35% efficience. Concentrator can use tiny bits of multi juntions (reducing cost) and concentrate 1000 suns and reach a 47% efficiency. But it requires trackers are costly.
A company developed a optical that always take the sun light to the same direction, but concentrates just 200 suns. They said to have 36% efficience.
Not sure if the 36% limitation (instead of 47% like othjer concentrator using multi junction) it's just because of the 200 x suns concentration, or if it's due loss of light when get through the opticals.
WHy not concentratre 1000 suns instead of 200??? Maybe the precision of the opticals should be too much, and the price of good opticals with such precision would increase the price.