Quote:
Originally Posted by ldjessee
I always assumed that the evacuated glass tube collectors were mirrored on the inside on the 'bottom' so that it would be more efficient.
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Yes, I've seen evac. tube collectors with parabolic mirrors under them.
Quote:
Originally Posted by ldjessee
I also thought by rotating the tube, you could 'tune' the system to better collect for a particular setup.
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I believe only certain types of collectors allow this. The tubes can be rotated a few degrees left or right if the roof isn't exactly facing south. Of course then the parabolic mirrors underneath are more or less worthless (they still may insulate the bottom by reflecting heat which escaped the tube). It would be ideal if the tubes could be rotated automatically during the day, but I haven't seen that.
I spoke to a guy who both researches and installs solar systems and he told me that evacuated glass tubes aren't worth the money. They may be 20% more efficient, but almost twice as expensive, and you'll barely save enough to make up the difference. Well, maybe. But maybe efficiency is more important than money? Which car is better: a cheap SUV or a car that is twice as expensive, but gets twice the milage? It might take long years to make up the difference, but the econocar is still better. At least in my opinion.