Seems like a great idea, they are seperating the incoming light with a
prism/diffraction grate sorta filter and concentrating only the useful
portion of the spectrum which keeps the silicon from roasting.
Yes, this all looks pretty cool, but you have to wonder about:
a) How long a hologram, which is typically printed on plastic media,
will last. Presumably, the hologram would have to be protected by a
glass UV barrier, to prevent premature degradation.
Maybe.
b) How long the pv cells will last without additional cooling, under
the extra light.
Whole point is they get extra useful wavelengths without the radiant
heat ? Presumably the prognosis is a whole lot better than other
reflector concentrators.
c) Why they are using cool-looking "high tech" holograms instead of
inexpensive fresnel lenses, which can be cast in glass.
Uh, no, that's not true of a hologram. You need at least a couple
wavelengths of light in thickness, in order to generate the
interference patterns upon which holographic effects are based.
OK. I though it was enough to reflect light or not, but I may have
missed the point.
A fresnel lens *IS* a lens.
Agreed.
It's based on the idea that it's really only the SURFACE of the lens
that does the refraction job required. So you eliminate much of the
optical medium (glass, plastic) between the refracting surfaces, while
maintaining their angles to incoming light. And of course, you adjust
those angles to account for the reduced transmissive distance within
the lens.
The bottom line is -- yes, you could use lenses -- but they would be
thick and expensive.
....
Conventional lenses would not be tunable in this manner.
