perspex sheets

[AndyD]

PV panels become noticably innefficient as the temperature rises so this might also be a consideration in your choice of materials for the frame and cover. As a rule of thumb you could lose 0.5% of the output for every degree Celsius over 25C. Figures may vary for better or worse depending exactly what type of cells you're using also terms and conditions apply.

Good luck with you project, keep us informed of your ups and downs.

[Justloadit]

Just remember that the PV cells require quite a bit of UV to make them work, that is why there is still energy from the cells when it is overcast. The light refraction due to the air between the glass and the cells will also play a part in the efficiency, so any glass which has lead in it, and majority do, it is what makes them translucent, will have a serious effect on the cell efficiencies.

As a matter of interest - how much did each cell cost you?

Solar panels are really dropping in price, so shop around and you may be surprised at the cost. There are figures around R11 per watt being bandied around, and there are suppliers who wish to clear their stocks out to replace with cheaper more efficient panels.

To get the kind of voltage you want, you are going to have to put cells in parallel, which will require diodes to ensure they are independent on each other, the volt drop across a diode plays a part in the losses as well. A silicon diode with 0.7V drop across it at 7 amps will create a loss of 4.9Watts, on 140watts that is just over 3.5%, with all the other lossy items you are going to use to make your panel, it may be that the effort will not really pay off.

[twinscythe12332]

paid 27 rand per cell, I'll need to put them in series otherwise the voltage will never reach the 18V mark... will keep you all up to date on how it turns out =)