I was intending to write about electrical connections, but I think I will let that for another time because I have a recent update on my project.
- Problem in the first solar panel:
I checked earlier on my first solar panel mounted on the roof, and I found that my idea of holding the solar cells to the glass with a PVC tape is a total fail. Unfortunately I did not account for the elasticity of the PVC tape. The PVC tape stretched due to heat during day hours and finally they got dry and crunchy and finally lost its glue and separated from the panel. The result for this problem is the solar cells were sagging and exposed to environmental changes (humidity, dust, rain, ...etc).
- Accounting for the problem in the second panel:
I decided to go for another material for insulating the solar cells and holding them straight at the same time. The first material I thought of was the acrylic, but it was very expensive that I could pay EGP 500 (72 USD) for one sheet. Next material I thought of was wood. I wend to the wood store, but I would buy a very big sheet and I would not use half of it. After that I had an idea, what about the thin fiber sheet that is used in aluminium kitchen doors?. I found a leftover at the aluminium workshop that was barely the size I needed. This fiber sheet is thin, somewhat flexible and covered from both sides with a water proof layer and cheap that I paid 110 EGP (16 USD) for both solar panels backing. This was exactly what I wanted.
- Solving the problem in the first panel:
I replaced the new panel with the old one. I took the old one down to the working place and removed as much I could from the ruined PVC backing and mounted the fiber sheet with silicone sealant. Fortunately it was not damaged and it measurements were OK.
- Adding the second panel:
I finally added the old (modified) panel in parallel to the new panel on the roof. I now have a generating power of 140 Watts x 2 = 280 Watts.
Note that I increased the inclination of the solar panels to 45 degrees because we already passed September where the sun goes below the equator. The solar panels are directed to the true South.
- More numbers:
I can now operate the TV and the PC+Monitor (166 Watts) easily all day. The extra juice is stored in the battery for some time of night operation, and when these devices are turned off, the battery is charging even more quickly.
I bought the 65 Ah battery to have a total storage capacity of 72 Ah. In ideal case (for calculation) when my panels produce 16 A, then to recharge the battery bank from empty (never happens) to full capacity, then I would need 72 Ah/ 16 A = 4.5 hours. By observing once, it took about 5 hours to charge the battery from 30% to 90%.
Practically, I operated the TV and PC for about four hours on the battery. This really made my day.
The battery bank, when full, holds a usable (30% DOD) power of (72 Ah x 12 V DC ) / 30% = 600 Watts. The solar panels can produce daily (assuming 8 hours of bright sun) 280 Watts x 8 hours = 2.2 KWh.
After two days, I found that I consume daily about 1 KW from solar energy. That is divided between day and night. Then the losses in the system must be 50% (this is a big number, but I don't know if this is normal accounting for efficiency of the battery charger 95% and the power inverter 70% and the battery bank itself 85%. adding theses losses surprisingly results in 50%, but I'm still not sure about this).
I had to go around my basic design more than once to fulfill the budget which has reached now about 8000 EGP (1143 USD).
To conclude this post, I feel special because, in my country no one does as I do. I have my tiny solar power station which produces free clean sustainable energy. I sometimes keep looking at the power meter while it counts the used solar energy and I dream about a bigger station which operates all my home appliances off grid. All my effort in the past four months (whenever I have spare time) were fruitful. I am really happy and have a feeling of accomplishment.
