Solar collectors - How and why to use them, build them or buy them
The idea of solar collector is based on the way smooth surfaces reflect electromagnetic waves of the medium part of the spectrum among which are ultra violet waves, visible to our eye lights, and infra red (heating waves).
Basically a sun collector is a set of mirrors placed either in spherical or in parabolic uniform to concentrate all reflected rays in one spot called focus.
So regardless of where on the collector the sun shines, they rays are redirected by the collector onto a fixed object. Usually onto a pipe surface to heat water inside the pipe.
Some times the solar collector is directed on a solar panel to get more useful energy from one spot using less solar panels. Or on a solar water distiller reservoir.
Mirrors could be either metallic or a usual glass mirror. The difference is that metal reflects heat better, but only when used for closeby objects (less than five feet away) For larger distances a usual mirror works better, despite loosing more heat while reflected.object is more then five feet away and usual mirror accordingly looses some heat while reflected.
Since there is no electronics involved, solar collectors are quite easy for an enthusiastic Do It Yourself builder. All you need is to build a base for mirrors either spherical (more proficient method) or parabolic uniform (for stretched heated objects).
Now if you want to use a spherical form as in satellite anthena you should buy a set of mirrors with summary square equal to a square of base. In case you want a parabolic base you can use a bended single plate. The best material for the base is probably wood, since it is both easy to work with and cheap.
Once you have all the materials you have to do the most laborious job ever to place the mirrors.
I consider that the most comfortable way is to place the mirrors on the wooden base where you can increase the layer of wood to achieve spherical shape. Then just glue the mirrors. You have to mention that to make your heliostat more effective you should locate it directly perpendicular to the sun's rays so you need to attach the mirrors very securily to avoid a crashing.
While you use a thin bendable single plate for parabolic mirror you can make a base with two thrusts. One movable and one not. And to move your adjustable thrust to bend or unbend your plate.
After you have achieved needed curvature just fortify that movable thrust. It is better to adjust bases and mirrors while there is 12.00 - 14.00 and sunny outside because the maximum area of your collector will be shined and it would be easy for you to detect the focus position.
There are some collectors in stores they appear with a rotating mechanism and a computer software to rotate mirrors to keep focus either concentrated or diffused light on whatever target you decide to light or heat.
Price for that device starts on $100 position and depends on size and material.