Solar heat 190 ºC from a mirror stainless steel sheet


We can find many interesting uses for this
spot of solar radiation from these stainless steel sheets which were installed by me a
few weeks ago. It is interesting that the spot can heat a
black surface to a temperature higher than 190 ºС We understand that the heating temperature
will increase drastically if we cover the black surfaces with a transparent sheet, increase
the thermal insulation under them and replace their black paint by selective coating. For several years, I have been using similar
solar concentrators for hot water supply, for home heating and for heating swimming
pool water. In addition, similar solar concentrators are
commonly used for district heating of cities, for generating a large amount of steam, for
electricity production, for solar cooling or other purposes. Unfortunately, these widely known solar concentrators
are very expensive, and therefore it is difficult for them to compete with traditional energy
sources or photovoltaic solar panels. That is why my YouTube channel is looking
for cheap types of solar concentrators, and this my concentrator is the next step of the
search. This white screen will help us better see
the spot of solar radiation from my stainless steel sheets. We can notice that the height of the spot
is less than 10 cm while all my stainless sheets have a total height of 170 cm If we need a lower spot, we must use a different
type of fixation of stainless sheets on a solar concentrator. For example, the stainless sheets of these
solar concentrators focus the solar radiation more accurately than my concentrator. These stainless mirrors of my solar station
are another example of the accurate focusing, and I installed them 3 years ago. The mirrors consist of thin sheet of stainless
steel which is fixed to this sheet of expanded polystyrene. Then the mirrors are fixed on this sheet of
expanded polystyrene which has these wooden battens. Of course, there is an idea that those two
polystyrene sheets between the stainless steel and these battens are redundant, although
that polystyrene gives us the ability to accurately focus solar radiation. This my solar concentrator puts that idea
into practice, and we see that the stainless sheets are fixed on the wooden battens without
the polystyrene. The battens fixed with screws to this wooden
board which connects to this stake through this primitive hinge. This surface of the board has the shape of
a parabola, although the focus accuracy will not deteriorate drastically if that shape
is a circle. These are the screws which fix my stainless
sheet on the battens, and the free rotation of this washer tells us that the screws do
not press the sheet tightly. The diameter of the holes in the stainless
sheets is significantly larger than the diameter of their screws, and therefore the sheets
have a few millimeters of freedom for their shift. I remind you that such solar concentrators
usually require constant changes in the position of their mirrors from morning to evening according
to the movement of the sun across the sky. However I use solar concentrators which do
not require the changes in their position. Now I begin to show the movement of this spot
from my immovable concentrator at different points in time of one day on 26 September
last year. I plan to describe several types of similar
solar concentrators in the coming months and years, and they do not require the changes
in the position of their mirrors from morning to evening if they meet the following three
conditions. 1) This direction should be exactly along
the West-East line. 2) The solar radiation receiver should be
located here, and it should have a height of 40-60 cm That is why this spot with a height of 10-20
cm is quite satisfactory for us because it is several times smaller than the height of
the receiver. 3) Sometimes we will have to change the vertical
inclination of our solar concentrators, and now I show how I change the inclination at
my solar station. We must do it once in a few weeks or months,
and these photos show the difference between winter and summer inclination. This is stainless steel of this mark with
a thickness of 0.4 mm, and I bought these sheets for 12 $ / sq. m However we can calculate that the wholesale
prices of similar stainless sheets are approximately 5 $ / sq. m This table describes the cost of materials
for the entire solar concentrator with these stainless sheets. We see that the total cost of materials is
about 15 $ / sq. m of mirror, and it is a few dozen times cheaper than these solar concentrators. But this table does not take into account
salaries and other costs of manufacturing and installing our concentrators. So, the stainless sheets form 80 % of the
total cost, and this fact helps us to see the economic sense of replacing these wooden
parts with metal. Perhaps those replacements will increase the
construction cost of our solar concentrator, but its lifespan will be longer and the focus
accuracy will be better. We understand that our method of fixing the
stainless sheets has some disadvantages, and for example, these screws and washers will
prevent cleaning of the mirror surface of our stainless sheets. In addition, drilling these holes can be time
consuming if we make them with an ordinary hand drill, and not with a similar machine. We understand that our sheet fixing method
does not yet have lengthy technical tests which should find drawbacks of the method. For example, perhaps aging of the wooden battens
will reduce their length, and therefore in a few years we will be forced to fix the screws
to other points of the battens. It is also obvious that these intervals between
the screws and between the wooden battens must match the maximum wind speed in your
region. Now I am showing my stainless mirrors after
3 years of operation open air, and we see that their reflective surface remains in good
condition. In addition, we know that a similar covering
of mirror stainless sheets remain in good condition for several decades. Perhaps wooden and other parts of the solar
concentrator will also have a long lifespan because they are similar to this row of my
solar station which is made of pine and has been in operation for almost five years. I think its lifespan will be more than 10
years, but its “weak point” is these wooden stakes which are rotting due to contact with
the ground, and therefore they need good antiseptic impregnation. We must pay attention to the fact that now
the mirror sheets are almost vertical, but I am afraid that their horizontal or inclined
position will noticeably worsen their focusing of solar radiation. That is why this of my experiments uses these
steel strips with a thickness of 2 mm, and they resist bending the thin steel sheet under
its own weight. We must pay attention to this upper additional
wooden batten, and this lower additional batten. This good focusing is possible thanks to those
two additional battens, but now I am showing the focusing without them, and here we see
that the focusing has become worse. These spots are the result of manufacturing
defect of the lower edge of my lower stainless sheet. We can slightly correct this shortcoming by
installing that lower additional batten, and here we see its screws This is the focusing after installing the
lower batten, but before installing that upper additional batten. These spots are due to the upper edge of my
upper stainless sheet. I fixed this flaw thanks to that upper additional
batten, and this is its screws. This gap tells you that the lower edge of
my lower stainless sheet deviates slightly from the parabolic shape. However this deviation improves the focusing,
and therefore it may be better to correct the shape.

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