May or may not be useful, but I seen at least application of using Mylar
space blanket with edge secured and partial vacuum on one side to create
parabolic reflector. Definitely cheap/light/simple, may not be rugged
enough for anything past experimentation.

On Wednesday, May 30, 2018, RussellMc <apptechnz@gmail.com> wrote:

> I have acquired a number of parabolic "satellite dishes" dishes (6 or so
> all up) which I wish to 'play' with as solar concentrators.
> I'm interested in suggestions for reflective coating methods not on the
> list below and for comments by people familiar with these methods.
> "Spray chrome" seems attractive if it works "half well".
>
> Aim is investigation of cooking, water heating and water sterilisation.
> Purpose is evaluation of practicality for developing country use. IOF the
> 3.3m dish proves useful it could grow a solar tracker (fairly easy) and m=
ay
> even be useful in personal applications.
> When used with a counterflow heat exchanger the water sterilisation
> capacity should be 5 to 10 times as much as water heating throughput at a
> given temperature.
>
> Intention is to gain practical knowledge - if anything practical results
> from this construction methods may well be quite different.
>
> Dish sizes are from about 300mm through about 1m dia in steel, 1.5m dia i=
n
> Al and a 3.3m dia Al mesh dish.
> [Mesh dish proper is very light. Dish dismantles to 8 panels which can be
> carried easily by one person wrt weight. Shape a bit annoying :-)].
>
> I wish to coat the surfaces with an optically reflective layer so as to
> provide concentrated solar energy at the focus.
> Ease of coatings and not much cost are rated ahead of efficiency - but hi=
gh
> efficiency is a welcome bonus.
>
> Flatness of surface and lack of 'bumps' not too too critical - these spre=
ad
> the focus point but this need not be as tight as in RF applications.
>
> The 3.3m dish is about 8 m^2 in area. In full sun at 50% efficiency would
> give about 4 kW. Useful :-).
>
> The mesh dish will need to be filled with a filler of some  sort and sand=
ed
> to a smooth surface - not too hard (ha!)
> The largest solid dish is Al and MAY sand to an adequate surface as is wi=
th
> eg a clear spray on coat to reduce ongoing oxidation.
>
> Possible options are:
>
> - 1. Adhesive backed aluminised mylar foil./ Less available here than in
> US.
>
> - 2. Non adhesive backed aluminised mylar foil - more available here.
>
> - 3. Space blanket - similar to 2. but usually more wrinkled from folding
> than desired.
>
> - 4. Al cooking foil (non adhesive backed). Cheap, available, lower
> reflectivity
>
> - 5. Spray on "fake Chrome. Goodness tbd
>
> - 6. "Real" chrome plate - commercial - even done with minimum effort cos=
t
> is highish.s
>
> - 7. Real chrome plate DIY - doable but high effort.
>
> -8. Other chrome imitators applied by eg tumbling. Dearish but cheaper th=
an
> chrome.
>
> - 9. Al surface sanded and clear coated.
>
> - 10. Front surface silver mirror using silver nitrate + clear coating.
> (Cost may not be TOO high. Result superb if doable).
>
> - 11. Small mirrors or broken mirror material stuck on surface. (Smallest
> focus size is about the same as mirror size and mirrors not sitting exact=
ly
> at dish angle beneath them will further degrade focus area minimisation. =
)
>
>
> Comments / ideas ???
>
>
>
>                Russell
>
> * "quick, easy & cheap" - choose any three.
> --
> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
> View/change your membership options at
> http://mailman.mit.edu/mailman/listinfo/piclist
>
--=20
http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist
.