Efficiency of Solar Reflector/Generator

The reflectivity of the parabolic surface and the heat exchanger fluid and exchanger coating will be critical...You may be exceeding some critical points with NH3....

http://www.nrel.gov/docs/legosti/old/5607.pdf

Thanks for the great links.The yearly average for my area is around 43 Kwh for 8 square meters per day.

My efficiency will not be as great as a perfect reflector, but I intend to use dual tracking to keep dish on target.I have a couple of dish positioners left over from the old days old C Band.

What do you think of covering the dish with used CD's in a spiral- fish-scale pattern,overlapping the non reflective areas? I intend to cut them in half.

Heating them will make them conform to the proper curvature, and high temp silicon rtv should hold them in place.

I realize this will not win any prizes for efficiency, but it will recycle a plentiful cheap commodity.

Any links for a NH3 powered alternator system will be appreciated.I can design protection for over temp/pressure protection.Perhaps there will be enough bypass heat to power a secondary alternator,operating at a lower pressure(perhaps below atmospheric).

Your thoughts and advice on this are appreciated.

I don't think the CD's will hold up well, nor do I think ammonia is the best choice as an expander fluid. In any case you will have to construct the dish portion to get a reading on the operating temperature and go from there.

I would consider polished aluminum or stainless as a reflector surface, with a clear coating that could stand up to the elements. And in choosing an expander fluid, you want something with the highest molecular weight, that's non-toxic, whose performance curve is showing good results at the temperatures you will be operating at.

https://organicrankine.com/?page=orc_turbine

....mylar? Will that work? It is quite inexpensive, comes in different thicknesses, and has approx %94 reflectivity.

These mylar collectors are great for portable or temporary use, but for long term permanent install, I don't know how it would hold up...Yes cheap and lightweight perfect for experimenters though...

The cd's will probably spread the light rays away from your focal point. For a mirror to work it must be flat. Cd's are what used to be called 'diffraction grating'. That is not a mirror surface.

Hey there HiTek, I don't think your use of cut-up CDs will work all that well.

You should be using an aluminized mylar sheet instead. Check out this supplier:

http://www.mirrorsheeting.com/

"What kind of efficiency could I expect from an alternator powered by expanding NH3?"

Less than the efficiency of the alternator.

One thing to remember about engineering. Start at the OUTPUT and work backwards.

Alt efficiency (what, 40%?) less turbine efficiency, less radiation losses from the concentrator. Getting the sunlight focused isnt rocket science.

Then don't forget double-conversion losses, unless you intend to constantly use whats produced.

Then decide what you'll STORE the power in, and accept the massive storage losses.

Ill estimate, at best , 6-8K out.

the problem everyone overlooks in designing alt energy is that energy is notoriously difficult to store. best medium is a 10K gallon water tank.

PS the reason "alternate energy" is called "alternate" is that its an "alternate to something that works"