MANUFACTURING OF PHOTOVOLTAIC PANELS

Plant designed by Roberto

Hello, my name is Roberto, and I have decided to build my own solar panels starting from the raw material; the photovoltaic cells.

A choice I have decided to make because I believe that the technical differences compared to the purchased panels are not significant, and saving significant amounts is a great achievement and a definitely important as well as satisfying experience.

First of all, I obtained the photovoltaic cells from https://www.mrwatt.eu/en/ from which I had the opportunity to consider the advantageous prices, especially for large quantities. Additionally, not to be forgotten, included in the price is the supply of ribbon sufficient for the work to be done.

The square cells have dimensions of 15.5 cm on each side, a voltage of 0.5 V, and a power of 4 W.

Initially, I wanted to combine 60 cells arranged in parallel rows to create a single panel with the dimensions and therefore the power of the panels available on the market, which is 240W and 30V in open circuit with a current output of 8A.

Exactly like the ones you buy!!

For a matter of transport on the roof, I was forced to build 9v panels, and then connect 3 in series once they were brought to the destination on the roof, sure that it wouldn't make any difference, just the voltage of 27v instead of 30v, since my inverter would require 24v.

The difficult part would have been constructing a container for my cells that is durable over time and resistant to the elements, so I decided to use glass and silicone.

Having been occasionally building custom aquariums for over 20 years, I am very familiar with the bond that connects silicone and glass, the "suction cup effect."

No other material can be as reliable as silicone on glass, but only on glass; be cautious when using silicone and polycarbonate, as the latter may seem smooth, but sooner or later the two materials will separate, and air coming into contact with our cells will quickly oxidize them (not to mention the rain).

Using a soldering iron of at least 50w, I began to connect the cells to create 3 rows of 6 cells each, then I siliconed them face up onto a 2mm thick glass sheet that is slightly larger than the area of the cells I arranged on it.

The function of the silicone is only to keep them more or less steady; alternatively, it is possible to use another type of adhesive as long as it is neutral.

 

As can be seen from the photos, I left the head and tail terminals longer than the edge of the glass for subsequent connections, and of course, the rows are arranged with opposite polarity to achieve the 9v. At this point, it is possible to perform measurements of the performance and characteristics of the product during assembly.

My intention is to build a sandwich panel, so I placed this sheet/panel on another 4mm thick glass sheet using powerful suction cups. The glass sheet is 2cm larger on each side than the 2mm one, perfectly centered.

The step that forms on all sides between the two slabs is sealed with aluminum corner profiles and silicone to ensure a secure waterproof seal and extreme sturdiness of the nearly finished panel.

It can be observed that the aluminum has been drilled on the sides so that the silicone can seep through the holes and create a more secure anchorage (same reasoning as before, silicone and aluminum will never hold as firmly as glass-to-glass, which is why there are holes that allow the silicone to expand appropriately to simulate the head of a screw).

I will then apply silicone on all sides of the inner/outer rectangle outlined by the aluminum profile, taking care to pass it through the holes, in order to ensure a solid bond between the glass and aluminum, also covering the ribbon terminals appropriately folded inside the panel, awaiting subsequent soldering with a wider ribbon.

This photo shows that the silicone starts from the underlying glass, encompasses the aluminum through the holes, and reaches the other internal glass pane through the other holes.

Basically, the two sheets are welded together with silicone, encapsulating the aluminum profile.

Once the welding of the elements was completed, I placed the usual diode and the connection cables using a cable of the appropriate gauge.

  

rear/front view of the finished panel

It can be noted that I did not frame the entire panel with an aluminum angle as I preferred to leave it smooth so that the rain can pass through the panel, even cleaning it, and it cannot stagnate on the usual lower edge, depositing dirt sediments as can be seen in commonly available panels.

If the work is done well, there should be no condensation forming inside at any time of the day or season, nor should the cells oxidize, as there is very little air inside the sandwich.

I produced several examples of these panels, and only in one did a small patch of condensation form in the morning due to a small air leak, which I immediately addressed by applying another layer of silicone.

The installation on the roof has been simplified because the panels obtained, as I mentioned earlier, are small in size, namely 1m x 54cm.

Once connected in series with 3 panels, I was able to perform measurements and technical assessments and noticed that the open-circuit voltage was around 29V and the short-circuit current was about 6.4A, for a total power output of 185W. Not bad, considering that I couldn't find the optimal angle of exposure to the sun and that my panels consist of 18 x 3 = 54 cells and not 60.

The roof anchoring was carried out by placing L-shaped profiles on a series of threaded rods protruding from the tiles, all of which are height-adjustable to align the L guides.

The panel rests on the L-shaped guide through the aluminum profile embedded in the silicone, and the panel's glass is pressed onto the guides using screws equipped with rubber caps to avoid damaging the glass of the panel itself.

Finally: cables, conduits, junction boxes, battery section, measuring instruments, charge controller, inverter, and various automation systems complete the adventure I set out to tackle and achieve with comprehensive results... but that's another story.

A heartfelt thank you to https://www.mrwatt.eu/en/ for giving me the opportunity to obtain the materials I needed and to start, albeit experimentally, the construction of photovoltaic panels, which are the main subject on which all the practical work is based, and to consider the savings and quality of the products.

From theory to practice... to satisfaction!!

A greeting

The name "Roberto" does not require translation as it is a proper noun.

Thank you again to Roberto for sharing his experience with us.