Help, my solar cells seem to be overheating

[olivcrom]

I wired up 36 monocrystalline cells in series and encapsulated them onto a 8mm plexiglas, the sun exposed part of the cells against the plexiglas, then I used EVA on the back to encapsulate it. Worked okay when I tested it, I got 21 volts and 5 amps. But the cells seem to be overheating, very hot to touch, and the voltage and amps start dropping. Any ideas why?

[Mike90250]

Cells in sunlight, get quite warm. Heating and loosing voltage is one of the calculations needed to be done with a string when running with higher voltage battery banks, or grid intertie uses, 20 panels in series, can loose 100V on a hot day, compared to a cold morning.
While still cold, do the cells perform properly, for the # you have in series, and parallel - do the volts and amps match your expectations ?

[olivcrom]

The first time I tested the panel, I did get 21 open circuit voltage and 5 short circuit amps which is very close to the commercially bought solar panels that I have. The difference is the commercial solar panel has very little voltage and amps drop, I tested them side by side, same angle to the sun, and the one I made went down to 18 open circuit voltage and around 2.8 short circuit amps. I am using an 8mm thick plexiglas to attach my cells to, do you think the plexiglas is not dissipating enough of the heat generated by the cells? I touched the glass on my commercial solar panel and noted that it heated up fairly quickly while the plexiglas on the panel I made did not feel hot right away, it did heat up eventually, after a few hours (estimate). Also, the back and front of the commercial panel felt about the same in terms of heat but the back of the panel I made felt really hot and it did heat up very quickly.

[Mike90250]

Right, plexiglass is not as good of a thermal conductor as glass. And it won't last as long either.

[olivcrom]

I also tested the panel I made by connecting it in series with my commercial solar panels (I have 6 12-volt 80 watt panels) and something weird happened, the voltage detected by my solar regulator did go up as expected, but the output watts did not change, and even seemed like it went down a little bit.

[olivcrom]

I was thinking about using a pre-made window with 3 mm float glass, but when I asked how much it would cost if I got toughened or laminated glass, the price went up too much, that's why I tried plexiglas. I might try using a thinner plexiglas and see what will happen with that.

[olivcrom]

Do you think 6mm toughened glass is okay to use?

[dman446]

building panels...

In another thread someone asked about "sticker rating". But I build my panels as well with the 3x6 grade a pretabbed cells.

I constructed 36 cells in series per panel. So theory output would be 18V @ 3.125A. Actual results vary in voltage but amazingly the amperage stays fairly constant +/- .25A.

Heres a photo.

http://www.facebook.com/photo.php?fbid=1226463388381&set=a.1226463028372.2030009.1432931934&ref=fbx_album

so far i have built 3 of these. mounted on garage roof side by side.

edit: voltage drops to about 14.5 volts in mid day sun at 100F

[leonscorpio]

In another thread someone asked about "sticker rating". But I build my panels as well with the 3x6 grade a pretabbed cells.

I constructed 36 cells in series per panel. So theory output would be 18V @ 3.125A. Actual results vary in voltage but amazingly the amperage stays fairly constant +/- .25A.

Heres a photo.

http://www.facebook.com/photo.php?fbid=1226463388381&set=a.1226463028372.2030009.1432931934&ref=fbx_album

so far i have built 3 of these. mounted on garage roof side by side.

edit: voltage drops to about 14.5 volts in mid day sun at 100F

is that aluminum frame that you used on your panel? if so, did you fabricate it yourself? it's pretty nice.. also, did you use plexi or is that glass covering your panel. thanks

[thomaswarner]

Mdpub?

That looks exacly like what Mike Davis did!

[dman446]

Yes, not to take claim for someone elses work. I did fabricate my design from Mike Davis website.

I did use angle aluminum from home depot for the frame and did use the non yellowing plexi for the transparent. I put the first one up in mid april and the next 2 a month at a time. So far I am impressed with their steady efficiency since day 1. No warping from any intense 105+ days during this summer and no visible moisture inside the frame.


I will say after seeing some of the builds from other members on this site with LIT glass and slygard backing, my build seems almost preschool to theirs. So very good job to those members, I wish my skills and talent were that advanced.