Michael (superb site and products BTW, thanks for your explanations), Back on the concentrated PV topic Jones's solution seems overkill to me, I wonder if a single film entirely occupied by adjacent non-imaging concentrators, laminated onto the solar panel "dotted" with cells localized at, and in direct contact with, the array's concentrated light outlets, wouldn't do the trick.
Another use of such a film occurs to me, it could be metallized on the output side, everywhere except at the light outlets, so that it would let most sunlight in on the input side, from a very wide angle, but only a small fraction of light and heat out on the metallized side, which would reflect them like a survival blanket. This could be used in thermal solar applications (water heaters, combined heating and insulation of eexternal surfaces of buildings....). Would such schemes work do you think, and would the film be manufacturable, and if so can it be done with a smooth easy to clean surface on the input side? (I assume you would know!) Michel ----- Original Message ----- From: Michael Foster To: [email protected] Sent: Monday, May 05, 2008 8:13 AM Subject: RE: [Vo]:Stationary Fresnel Array (Hybrid) --- On Sun, 5/4/08, Hoyt A. Stearns Jr. <[EMAIL PROTECTED]> wrote: > From: Hoyt A. Stearns Jr. <[EMAIL PROTECTED]> > Subject: RE: [Vo]:Stationary Fresnel Array (Hybrid) > To: [email protected] > Date: Sunday, May 4, 2008, 4:47 PM > I don't know if this is relevant, but I'm reminded > of what I thought was a > clever design of a supermarket bar code reader, whereby > they built the > conventional spinning mirrors/optics system, then took a > hologram of the > system, and now just spin the laser illuminated hologram to > scan the complex > raster on the bar code. Yes, it's relevant. It's relevant as an example of misapplication of technology. I was briefly involved in that one. These discs were made with dichromated gelatin, a wonderful but touchy and tempermental holographic recording medium, a medium for which I am incorrectly given credit for inventing in some books. These were eventually shown to be more expensive than the optics they replaced, and certainly more expensive than the simple oscillating scanner mirrors that replaced them. I worked as a consultant about 25 years ago for a company that had a DOE contract to research holographic solar energy concentrators. The people who had the contract were just a group of scientists who were good at getting government contracts. They hadn't a clue how this might actually be done, and weren't about to tell the DOE representative who showed up periodically. Essentially, I did all the work and they would make sure I wasn't around when the DOE showed up. Their basic idea was to make flat holographic reflectors with a virtual parabola. Again dichromated gelatin was used as the recording medium. There were to be three closely space foci, each a different spectral band, in other words, RGB. The purpose of this was to allow IR wavelenths pass through the holographic reflector to avoid heating three different photovoltaics, whose maximum efficiency would be at the three wavelengths. I pointed out to these geniuses that it would be far cheaper to use fresnel lenses coupled with transmission blazed diffraction gratings to achieve the same result. They said not to mention anything about that, because they would lose their DOE funding. So I went ahead and did what they wanted and left. This part is the most fun. A month or two after I left, they called me in a panic, saying they suddenly couldn't duplicate my results. The reflective efficiency and wavelength separation had dropped dramatically. I told them their problem lay in the coating, which they initially didn't believe. To shorten a rather long and comical story, they had to pay me ten grand for three words, "Make it thicker." That was so sweet. This whole enterprise was a lesson to me in how government contracts are funded and for what reasons. These guys spent millions on this boondoggle and they knew that's what it was. M. ____________________________________________________________________________________ Be a better friend, newshound, and know-it-all with Yahoo! Mobile. Try it now. http://mobile.yahoo.com/;_ylt=Ahu06i62sR8HDtDypao8Wcj9tAcJ
