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Natural Science Forum / Physics / Optics / August 2005Small (200mm) parabolas at low cost.
I notice lots of 200mm parabolas of reasonable accuracy in my local DIY store, piled up as "5000000 candlepower light", for about $35(us). Does anyone know of a source of the reflectors for reasonable money? Say $7 or so? I know that it'd be trivial to get them if you order a million - but I was wondering about maybe 25, to cover most of a square meter, as solar collectors. (A few plumbing fittings in place of the bulb, heating water to 120C or so, to be used in combination with more conventional solar panel, for periods when there is direct sun.) > (A few plumbing fittings in place of the bulb, heating water to 120C or so, err What pressure were you going to be working at then ? Steve > I know that it'd be trivial to get them if you order a million - but I was > wondering about maybe 25, to cover most of a square meter, as solar > collectors. How about a mirror made from segments, tiled with tilted plane mirrors and adjusted with dry-wall screws. Or a mirror spun in epoxy resin, or even one made out of an old satellite dish with aluminium foil glued in ? But why go for the dish approach anyway ? Are you space limited ? Steve >> I know that it'd be trivial to get them if you order a million - but I was >> wondering about maybe 25, to cover most of a square meter, as solar [quoted text clipped - 5 lines] > > But why go for the dish approach anyway ? Are you space limited ? To some extent. The dish approach can trivially produce high temperatures, which are useful for boosting already hot water, at maybe 40C, to 60C+, to improve its usefullness. > To some extent. > The dish approach can trivially produce high temperatures, which are > useful for boosting already hot water, at maybe 40C, to 60C+, to improve > its usefullness. True, but you could concentrate light onto a pipe placed on the focus of a linear reflector too, which is probably easier to fabricate. Steve If you're doing water heating, parabolic reflectors of that size really aren't needed. In addition, the small spot size of a spherical mirror of that size is still really too small for good heating. I'd go with a much larger mirror that will pretty much fill the pipe diameter (or better yet a flat surface) and leave it at that. In addition, you'll get about 1KW peak from a meter of aperture of the mirrors. -- Why do penguins walk so far to get to their nesting grounds? |
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