Solar Concentrator

[veewee77]

I have 3 dishes, all solid aluminum.  Polishing the aluminum does take time, but once you get it polished, it just takes waxing with a regular auto wax to keep it shining.

Mt dish is only 6 foot but it will set a piece of 1x4 on fire in about about 5 seconds.

Visit my gallery and I think there are ics there. . .

Doug

P.S. http://www.anotherpower.com/gallery/dougs-place

[windjunky]

Nice Job!

What if you used contact cement on the dish and on the mylar.  Then tacked the mylar around only the rim of the dish, pulling it tight like the head of a drum.  Next, get your shop vack and slowly suck out the air inside.  Is there enough strech in the mylar for such a trick?  I have done something like this to make a mold for a poyester lens I cast as a kid.  Worked well.

Windjunky

[Titantornado]

This is such a good idea, I'm surprised it got glazed over so easily.  The plate could be sized up a bit, say one foot, and placed a little bit beyond the focal point to distribute the energy across the entire plate evenly, and not so intensely.  Even if there was a circulator pump failure, you are only talking a few ounces of water to turn to steam.  A simple P/T valve in the system could easily vent off the pressure build up should such a failure occur.

[pyrocasto]

Though it takes 80mw to light a match.

[Norm]

  As about 4 others have posted...the main idea

here is to lessen the concentration ...that means

either up above the focal point or a larger

circumference object to be heated....in the case

of the Pyrex....above the focal point.

  Another good way would be to stretch a sheet of

Mylar across the aluminum dish sealed ....a

vaccum tube in the center of the dish adjustable

to change the focal point and lessen the concentration.

             ( :>) Norm.

[Jeff]

A few years back, I designed & built a machine for Proctor-Silex that welded heating elements for irons & toaster ovens. For the base, I used machineable ceramic. I used smaller pieces, but a piece 1/2" thick by 1 foot square cost about $100. It's just like graphite to machine (soft & brittle!), but once heat-treated, it's just as you'd imagine any ceramic to be.

Just a thought for a collector. Google "machineable ceramic".

[MattM]

Very good suggestion.  Its the only practical way to transport the heat any distance, too.  Pumping liquids is a energy consumer, which means you have to input another form of energy to make it happen.  With the phase change you could insulate the line, the gas will naturally draw through the line, and by using a simple Liebig condenser elevated above the source to cool the gas at your destination you can try to take advantage of gravity to flow the condensate back to the reserve.  You could always get more complicated later.  If you are going to use something that expands to a dangerous pressure level like water then a pressure relief valve or two is necessary.

Any idea how you'll seal up the lines under that kind of heat?  If aluminum is getting hot enough to lose integrity then copper probably isn't going to do much better.  Brass won't be much different than copper.  Hell, even the hard solder you'd normally use to build the piping is going to have problems with that kind of heat.  Old iron pipe might do it because you can fit with threads.  But most of your traditional water pipe methods probably won't be all that helpful if they are in the line of fire so to speak.

[spinningmagnets]

Hi Frank, you mentioned that it took the pyrex about ten minutes to be damaged, but I'm certain if you had water flowing through it and drawing the heat away, it would have lasted.

XWZCIENCE has done some work with steam tube boilers, and one of his posts is about a coil he made from very thick-walled steel pipe. He indicated the mass of the steel acted as a thermal buffer that absorbed the fire heat and evened out the heat transfer to the water-steam conversion, making it steadier and more controllable.

If anyone still asks about you shooting planes out of the sky... (I agree with Volvo Farmer) If the focal point is 12' out, then the "hot zone" is everything within 24', and will look like two funnels connected at their tips (similar to an hourglass shape). The reflected light (to a plane or neighbor on an elevated hillside) will be no worse than any 1-foot flat mirror.

If you don't want to move the entire dish if flow stops from a failure, you might also consider a system where the heat-exchanger moves just a couple feet. Such a system might also allow you to adjust the position of the HE for maximum absorbtion on a mild day and partial absorbtion on a sunny day.

I have seen a hydraulic system on aircraft where the actuator moved as it cycled the flaps. Rather than supply it with a short section of rubber hose, a short section of metal tube was used for longevity. It had been coiled with 5 turns, and the coil was aligned with the actuators base pin. I expressed suprise, and my boss looked up the specs, then assured me 5 coils of stainless steel tubing could take millions of cycles. The pic below is from a moonshi...um...I mean a "water distiller".

http://www.conquestinc.com/images/Life%20Saver/LifeSaver4.jpg