They are made from free mirror strips which are garbage in various glass workshops.
These mirrors are free, and I will describe how they are manufactured and how they are installed in a solar concentrator.
These mirrors can be used for these various concentrators Parabolic trough.
My free mirrors are made from these strips which are scraps of large mirror sheets in a variety of glass workshops. In other words, these mirror strips are garbage, and they throw out these strips.
Thus, we need to give these mirror strips the right length, and I do it with a glass cutter. The result of these works is these sets for mirrors with different widths, and I made these sets from this heap of mirror strips from one small glass workshop, and this heap was collected during 6 months.
Now I am showing the manufacture of a mirror from one of those sets, and this is a sheet of expanded polystyrene with a thickness of 3 cm, and this is matches. We can see that the strips are put according to their width, starting from the widest and ending with the narrowest.
This is the tracks of polyurethane foam, and they are put with an interval of about 5 cm. Immediately thereafter, the strips are turned. After that, we put flat battens with loads on our mirror, and the surface of our table should also be flat as possible.
Then we remove the load and these matches. In addition, we can remove those pieces of hardened foam, and I have a hypothesis that these pieces will interfere with the focusing of the mirror. If we want the number of these pieces of the foam to be as small as possible, we must put those foam tracks in the form of such zigzags.
Now I show mirrors which has been operating during 8-9 years outdoors, in the cold, rain, snow, etc. We can see that the aging of the mirrors gave defects to their reflective layer, but these defects cover approximately 1% of the area of the mirrors. That is why I predict that the lifespan of these mirrors will be 15-20 years. However the lifespan can be reduced by hail, but these mirrors have already survived hail with a diameter of up to 10-15 mm in 2013 and 2021
I think that the main cause of these defects is some substances which are in the polyurethane foam, and they gradually destroy the reflective layer. In addition, perhaps the cause of these defects is moisture which is retained by those foam tracks.
Now I will show how to install this mirror on concentrator, and this requires 6 such points of polyurethane foam. You need to pay attention to this support of the mirror. This support is temporarily installed on the concentrator, and we can remove it in a few hours.
We must pay attention that more narrow strips of the mirrors should be placed here, on the periphery of the concentrator, and wider strips should be here, closer to the center of the concentrator.
We need to make the right width of the interval between the mirror and the concentrator, and these wedges are one of the possible methods. The upper edge of the mirror must also have the interval of the right width. Then we put the foam points at a depth of 20% of the height of the mirror.
I want to clarify that now we do not see those wedges, and this video is an example of another method of ensuring the right width of the interval, and now it is done by small flat pieces of wood which is not shown by this video, and we must remove those wooden pieces in a few hours. The upper part of the mirror also receives similar foam points.
Now we give the right width to the lower interval. The upper interval must also have the right width. Then, our polyurethane foam fixes the upper edge of the mirror and its lower edge, and it is obvious that we can remove these wedges in a few hours.
However we did all this, when we already knew the right widths of those intervals, and it is obvious that we must install our first mirrors in a different way, and I will describe it further, and one of our goals is to measure the right widths of the intervals.
