Solar at its Best

I'm not trying to be negative or nitpicky, but does the shade from the item in the bottom of the picture affect the incoming current? I've seen even 1-2 square inches of a panel shaded cause the whole panel to lose 50-95% of the incoming energy compared to full sun.

I love these solar setups. I am working on ideas for two (one fixed and mounted on the roof), and one detachable (so when touring it stays at home, but boondocking, I have it available.)

The nice feature for a decent solar setup will be not having to fire up a generator when out in the wilderness unless it is to exercise it. Even my Yamaha makes a lot of noise compared to the quiet of a forest or meadow.

That picture was taken at around 4:00 pm on Sept 8 with the truck and trailer facing north while I was winterizing the trailer. The sun is quite a bit lower in the sky up here in northern Canada as fall approaches. There is a little shade but by this time of day the system has been in float charge for hours. The panels are wired in parallel and still do a very good job. Most of the season when we have sunlight until 10 PM shading isn't a problem with the AC unit. I have not run the genset very much since putting in this system.....never to charge batteries anyway. :)

Hi Almot,

Individual solar cells are often about over 0.5 volts each. So to get to 17 volts, 36 are placed in series. If there are blocking diodes between each cell then the loss of one cell will drop panel output by a little more than 1/36 of the total output, but the voltage would be ~16.5. Since the guru's say charge at 14.8, if six cells are lost--the voltage won't be sufficient to do much charging at all.

Individual blocking diodes do drop the overall panel voltage. Mine run at 16.5 volts, and there are 22 cells per panel. Here are all the details in a non clicky http://www.kilowatts.com.au/US64/solar-panel-details.php

pianotuna wrote:
Yes, there are diodes between all cells. I did do some quickie tests in the summer of 2009 that showed I did not loose the entire panel when one cell was totally shaded. However, Salvo has suggested that partial shading of a single cell is worse than total shading. If I understand what he meant (and often I don't)--the diode fails to "lock out" the cell under those circumstances which results in the panel outputting at the level of the "weakest" cell.

There is something here I don't understand. If all the cells are in series, then one partially blocked cell will result in the whole panel working at the current of the weak cell.

One fully blocked cell will result in losing the whole panel. Or in this case those bypass diodes do their magic trick and you only lose one string, say, 1/4 of the panel if there are 4 bypass diodes? It's interesting that you have diodes on all cells - I thought they usually put just a few diodes.

Hi KendallP,

Yes, there are diodes between all cells. I did do some quickie tests in the summer of 2009 that showed I did not loose the entire panel when one cell was totally shaded. However, Salvo has suggested that partial shading of a single cell is worse than total shading. If I understand what he meant (and often I don't)--the diode fails to "lock out" the cell under those circumstances which results in the panel outputting at the level of the "weakest" cell.

Here is an extreme example. Put a six volt eight amp motorcycle battery in series with a six volt 400 amp fork lift battery. Current will be limited by the weakest (smallest) cell, so output would be 8 amps.

It is always better to have zero shading. I do get 7 amps in leafy shade at solar noon if the battery bank is "hungry".

pianotuna wrote:
Hi KendallP,

No, my unisolars don't produce power in moonlight. The flexible ones were purported to be able to do so--but I've never seen documented proof of that. Personally I think it is a hoax.

I have seen amorphous panels produce voltage and a teensy bit of current from being under a street lamp. My Unisolars won't do that either.

Roger. I thought for sure I had seen evidence that, at least the flexible units had that capability... though... to a tiny degree. It's been awhile, though.

But you still have diodes between each cell in yours and thus only proportional loss based on the amount of shade, yes?

Is anyone else doing that yet?

Hi KendallP,

No, my unisolars don't produce power in moonlight. The flexible ones were purported to be able to do so--but I've never seen documented proof of that. Personally I think it is a hoax.

I have seen amorphous panels produce voltage and a teensy bit of current from being under a street lamp. My Unisolars won't do that either.

mlts22 wrote:
I'm not trying to be negative or nitpicky, but does the shade from the item in the bottom of the picture affect the incoming current? I've seen even 1-2 square inches of a panel shaded cause the whole panel to lose 50-95% of the incoming energy compared to full sun.

Unless there are diodes between each and every cell... then you may be correct. However there may still be enough ambient light there to keep it running.

That's the main reason Pianotuna went with Uni-Solar. He can still get a little power from moonlight.

For a home system, one can control location and tree growth. But for a camper moving from campsite to campsite...

RickSo wrote:

I'm not trying to be negative or nitpicky, but does the shade from the item in the bottom of the picture affect the incoming current? I've seen even 1-2 square inches of a panel shaded cause the whole panel to lose 50-95% of the incoming energy compared to full sun.

I love these solar setups. I am working on ideas for two (one fixed and mounted on the roof), and one detachable (so when touring it stays at home, but boondocking, I have it available.)

The nice feature for a decent solar setup will be not having to fire up a generator when out in the wilderness unless it is to exercise it. Even my Yamaha makes a lot of noise compared to the quiet of a forest or meadow.

smkettner wrote:
Nice gizmo shown in the OP. I still prefer the low maintenance and probably lower cost of panels flat on the roof.

MEX, how many air conditioners on that RV? How long is it?
Would have not been much extra to just have a scaffold and go solid across the whole roof. :B

I just love the idea of hanging some hinged panels off the side and then stuffing the basement with Lithium batteries. Or putting a diving board in Scrooge McDucks Money Bin...

Solar at it's best.

Me thinks (RJ) Rich, is in on the ground floor with his set-up. Now the Chinese are following. Wonder what a year from now will look like with Solar Trackers. Solar in general is going to increase by the month. Coming to my home town is a new MFG plant for the new 2D panel for installation in the big Texas money Solar Station. Will employ 600 by next year.

O$S
Floyd