Pilot project II.

The first pilot project has resulted in a solid full 72 cells panel. I am not entirely happy with this panel and I want to make two panels to try some changes. I will make two because two more fit on my shed and because I think there are two needed to make a "perfect" panel. There are some important things I want to change and some small updates I want to work on. The main changes are:

The glass I use is currently second hand greenhouse glass and this has some drawbacks. It is not clean and requires much effort to clean and then I feel that it's still not really clean. Furthermore, the glass is not tempered and a panel is quite expensive. I've never been hit by very heavy hail, but Murphys law "predicts" that this will occur at the time I got the last panel installed. That is slightly exaggerated, but it doesnt feel so good.

The silica gel that I bought comes in a small white paper bag of some sort, but it could be something else then paper. This material is very stiff and does not tear. This is bag is airtight packaged in silver foil-like material. The bag is so small that the silica gel is accumulated making it thicker than 3 mm. Therefore I cut the bags open and empty it on the panel just before I seal the panel. I thought the beads would ultimately end up at the bottom of the panel because it is mounted at an angle. But when putting the panel together the beads roll across the panel until at some time end up between a cell and the glass and stay there:

Silica gel between glass and solar cell.

I hoped that they would come loose eventually and still would roll to the bottom but that does not happen. On the contrary, probably under the influence of expansion by heat at one time the silica gel presses in the cell so the cell goes bad. Here is a picture:

Silica gel breaks solar cell

And another one:

silica gel breaks solar cell

And the final picture:

silica gel breaks solar cell

At present it seems to have little influence on energy production, but I want to fix it and therefore have to come up with and idea so the silica gel will be "fixed" in the panel.

When placing the aluminum I "pushed" the sealant between the glass plates until it came out. The result is that a second ring of sealant is created. I also tried to minimize air between the aluminum and glass so I used plenty of sealant. The disadvantage of this second line is the following. In itself it is a good concept having two lines of sealant, just what happens when the outer piece is not airtight? I expect there eventually comes moisture and in the long run water will come in there. This water will go down (to lowest point) and will ultimately fill the space between the two layers of sealant. This in itself is not a problem until it starts freezing. Water expands as it freezes and it is terribly strong and can break a lot. And in that case I fear it will break the panel. Therefore I want the second layer of sealant to be tight to the first layer.

Two layers of sealant

In the above picture it shows that the layers of sealant are here and there connected. But in most places it is certainly not. I will also use only white sealant, but that is just for looks.

The last change I want to implement is the use of bypass diodes. The use and operation of bypass diodes, I only found out after I had finished my first panel, and I want to apply them. Even though I have the panels on the roof where they are not affected by shadows, I certainly have that problem with the panels that are on my shed. It may also help if a cell in the panel break. Then is the whole panel wont be lost.

First I ordered glass. I have doubted a long time, but eventually decided to do it. I have made several offers and finally came to a price of Euro 12.95 per square meter. I though this is a very good price and had a chest (40 sheets) ordered. Then I thought a very long time about the silica gel problem but could not come up with a solution until someone game me a possible solution by using a stocking. I do not remember who it was who said it, but thanks. I've taken an old sock and cut a piece of it and use super glue to stick it to the glass. This worked surprisingly well:

Sock with silica gel.

In the The solar panel section I describe why and what diodes are to come. I have ordered from Digikey some diodes and put them inside the panel. Here is an overview of the diodes in the panel:

Diodes in panel - overview.

And here is a detailed foto of a diode:

Diode in panel - detail.

And this is how all panels look on top of the shed:

All panels on shed.

To date (6 weeks after installing the last panel), I average nearly 1kWh daily production. Because the panels are in the shadow till 12 I'm most happy. The leftmost panel is the first panel I made. This panel begins to look a little bit "fuzzy". I meanwhile found out what that is and will probably write more about it later. The small panel in the picture is one of the first test panels. This I sealed and placed on the roof without aluminum. This was the panel that broke (a crack in the glass), so I've glued a piece of glass over it. This panel provides the power for the fans that cool the OK4Es cooling fans and it charges some batteries. At night the lighting that I replaced with LEDs is powered from these batteries.

Electric wiring in shed.