How does Partial Shade cause problems?

[BilljustBill]

I have what appears to be an aluminum goldish colored framework with matching anodized jaw clamps that would clamp on a post or pole. The Suntech H-60 watt panel was bought at a flea market almost 16 years ago. The old rancher fellow said he thought half of it was bad, but I was focused on scraping it to get the cells back then. It has 72 two inch square cells wired in groups of 36, and there are two red wires and two white attached to the buss bar. Pulling it out of my storage building, I've found that it operates at only 30 watts.

On one of the 36 cell series, it appears that a group of 3 cells seem dark and the glass area over those appeared to be warmer than the rest of the panel when I ran some test on it a few weeks ago. The soft rubber-like backing seems to allow for repair of the panel, so the $30 I paid for it might not be wasted.......

If this panel had shade on part of its surface during the day, would that have caused that series to go bad? How does that happen? Any tips on repair?

Thanks,
Bill

[Mike90250]

Shade on a panel won't damage it. When a panel is operating, and a cell is shaded, that halts electron flow, and cells around it can't "force" the electrons thrugh it either. Some panels have bypass diodes, so current will flow in an array, if one panel is shaded.

Repair - you are on your own, maybe the best bet, is to just bypass the 3 bad cells, and loos a little bit of voltage.

[BilljustBill]

Heard of this?

I ran across this link that sells a product which adjusts the varying output of the panels due to age, shade or dirty panels... any comments? I didn't see what the cost per panel was for their product...

http://www.solarmagic.com/news_events#events

Bill

[Mike90250]

It's pricey. Idea was to "equalize" many panels in a large array.

[Blackman]

I know one thing, today in Brisbane we had the worst dust storm ever recorded and my daily harvest was below 50%.
I visited the roof and could not believe how dirty the panels were, I actually wrote my name on the glass( No i would not do this to a car) Tomorrow its garden hose time, but my concerns are this stuff can cake on if left for a while.

[BilljustBill]

Another: "Heard of this?"

Lowes will start stocking smaller size solar panels before September ends made by a company called Brightwatts. Inc.

http://www.lowes.com/lowes/lkn?action=productSection&catalogId=15

The company Brightwatts, Inc., has a link to another of their vendors. There is a new thin film solar cell and 130 watt panel for under $230.00.... by December.

http://www.dmsolar.com/solar-module-111.html

Any input on this newer type of cell/panels?

Thanks,
Bill

[Mike90250]

> up to 10% cell efficiency

Most panels are 15% or better. The price per watt looks OK, but what's the warranty?

[BilljustBill]

> up to 10% cell efficiency

Most panels are 15% or better. The price per watt looks OK, but what's the warranty?

Here's what they say, I don't know what they'll do... ;>)

http://lib.store.yahoo.net/lib/yhst-21796510175022/module-warranty.pdf

[Robert So]

does it make any difference if the solar panel is 15%efficient and another one that is 12% efficient? if they are both rated at the same watts?

[Mike90250]

does it make any difference if the solar panel is 15%efficient and another one that is 12% efficient? if they are both rated at the same watts?

Depends on your mounting area, If you have lots of space, no problem, if you are trying to get the most watts on an RV roof, then efficiency does matter

[MarineLiner]

Bypass diode

Some panels have bypass diodes, so current will flow in an array, if one panel is shaded.

Very smart.
What is the type of that diodes?
So far, i only know one-way (rectifier?) diode.
Thanks.

[Mike90250]

There are many types of diodes, in solar applications, schottky diodes, have the least loss, and are used often.

http://en.wikipedia.org/wiki/Schottky_diode

excerpt: A normal diode has between 0.7-1.7 volt drops, while a Schottky diode voltage drop is between approximately 0.15-0.45 – this lower voltage drop translates into higher system efficiency.