My array was getting shading from my house in the morning. My eight Sharp 165w panels were positioned in a single row with the panels vertical. The house shading would cast a shadow across all of the panels effectively keeping them from producing any significant output until they were all fully in the sun. After reading another post about the number of diodes in the Sharp panels (3), I started to think about how they were configured. It seemed that since the junction box was at the long end of the panel, the cells had to be configured in 3 columns in parallel. So, I had two theories. First, I assumed that if I rotated the panels into two rows of four panels each, that the row farthest from the house would be in full sun sooner (between 30 and 45 minutes) and thus I would have full output from them sooner. Secondly, I assumed that if the cells were in wired in three columns, that as the shading line moved up, a full column of cells would be in full sun and the diodes would prevent any reverse voltage into the shaded columns. So, I figured that I would get sort of a stair step output as each column of cells got into full sun. It appears though that I was only half right. I do get the bottom row of panels into the sun sooner and I do get power out of them sooner. However, I still get almost nothing if there is any shading on them at all. The bottom line is that it appears that any shading at all regardless of whether a row or column of cells will keep the panels from outputting. Here is a picture (FishBowl graph of SunTie output)of what I am talking about. The left side was with the single row of panels vertical, and the right graph shows the two rows of panels horizontal. The step is when the bottom row of panels is in full sun. More pictures can be seen on my site linked below.

[img]http://www.marks-home-theater.com\stuff\shading.jpg[/img]

[ 09-01-2003: Message edited by: Mark Lopez ]

Mark :

Your latest graph indicates your array is SSW oriented, since you don't have a step on the graph before sunset. You've done a lot of good incremental work, and I'm not sure a suggestion to shift the whole array to the west would work for you. Also, I recall seeing tree shadows in one of your pictures, which shades the western side of the array come winter (which means you'll need to spin your panels 90 degrees again to maximize efficiency). I suppose the association is against asking your neighbor if you could hack his tree a bit ?

Since you've settled on particular gear already, I can't suggest panels with built-in inverters (like RWE Schott) that'll gain you a little more power & flexibility. Anyways, I think this is the best you can hope for, and I laud you for wedging in PV into a very tight space.

Larry H

Larry,

The problem is that I will always get some sort of shading. In the summer, it's from the house and in the winter it's from the trees. The tree issue is not so bad since it is usually pretty late in the afternoon before it hits and power loss is negligible. BTW, the trees are mine. [img]images/smiles/icon_smile.gif[/img] The summer house shading is more of a problem because I would be getting partial shading sometimes up until 11:00am which is during high production. I had helped the situation by making the whole array 'tiltable' thus moving it few feet away from the house. However it did not totally remedy the problem. Since I was getting nearly a straight shade line across the top of all of the panels it was effectively killing them. That is why I rotated them. This way at least half of them (2 strings) are in full sun much sooner. You can see that in the graph above. What was disappointing was that I was not getting more of a 'stair step' effect with the other bank of panels as the shade line moved across them. I had thought that as long as I was getting a 'column' of cells in the sun, they would be outputting. In actuality, it appears that partial shading kills the output regardless of whether it's a row or column that gets shade.

Anyway, the whole project has been a good learning experience and should I ever move to where I have more options, I will have a better idea on how to set things up.

Hopefully your learning experience will open your eyes (and others) to the possibility of built in photovoltaics. What is BIPV , you ask ? Try scanning the info found at
http://www.google.com/search?hl=en&ie=UTF-8&oe=UTF-8&q=built+in+photovoltaics&btnG=Google+Search

and you will notice an interesting pattern emerge. Most of the next generation PV R&D and implementations are being done, right now, in Europe, on new & existing structures. PV elements in the building's envelope, on the rooves, in the walls, along highways and railways. In all sorts of colors, shapes, textures, opacity and sizes. The Europeans realize the gain in creating RE elements without worrying about optimum performance under any conditions like most Americans.
This may be the kernel for another thread, and hopefully it will at least get some folks thinking outside the constrictive solution box we've put ourselves in here in the US.

-- Larry Hale

i just ordered sharp 175W NT-R5E1U panels at my dealers suggestion.. can i expect similiar results with these too? i have been reading about unisolar panels which are supposed to work better in situations like this. I am waiting any day for parts to my starter PV system to come in which is just those 2 sharps for now.
i expect more than id choose shade morning and afternoon here and its a concern. i was thinking of mixing/matching for my next pair so id have some flexibility but not sure of my wiring options.. we chose the sharps as i am getting a mx-60 mppt controller and i guess they have pretty high voltage output.

thanks for any info