Hi-

Perhaps this is a newbie question!

I am in the stage of pondering how to design a system for my house.

I'm trying to figure out how I should wire up a set of 8 of the new Kyocera KC167G panels to a Suntie 2500 (there would be another array of 4 of these panels connected to this inverter, as well).

I'm having trouble understanding what the nominal voltage for these panels is - some people claim 24 volts, and some people claim 12 volts. The max voltage listed on the Kyocera spec sheets is 23.2V

Does anyone out there have any suggestions on how to wire up an array like this for a Suntie 2500?

Thanks for any pointers/guidance you can give me!

Dan

Hi Dan,

The KC167 and other similar panels confuse a lot of people. They are 48 cell panels. "12 Volt" panels are 36 cell so you could call the KC167 "16 Volt" panels. To further confuse things, they are often called "18 Volt" panels.

What ever they are called, they need to be in strings of 3 panels for a nominal "48 Volt" system like the SunTie. A string or 2 will be too low for the MPPT algorithem in the SunTie to work and a string of 4 will have too high of open circuit voltage for the Suntie in cold weather.

You will need to get at least one more panel for 3 strings of three (1500 Watts).

You could go up to 6 strings of 3 on the ST 2500 for 3000 watts DC input so you could add 1, 4, 7 or 10 more of the same kind of panels.

Ron Schroeder
Brookhaven National Lab

Hi Ron-

Thanks for the quick reply. Perhaps I could burden you with one more question.

The array of 8 KC167's would be at the same orientation, but at a *different tilt* from a second array of 4 KC167's. Both arrays have identical shading (the roof just changes pitch between the two arrays).

My reading of the literature tells me that it would work to put two of the modules from the array of 8 in series with 1 of the modules from the array of 4 KC167's. If this worked, then I'd be set.

Is this likely to be a problem? Any thoughts would be greatly appreciated!

Dan

Hi Dan,

It is best to have all of the panels in the same string in the same orientation and tilt since the panel getting the weakest sun will limit the whole string. How much difference in tilt will there be?

Dan,

Do you already have the panels? You might want to consider strings of 4 KC125's instead of strings of 3 KC167's.

Or could you put 2 rows of 6 KC167 panels on the same roof section?

Hi Ron-

The difference in tilt is 12 degrees versus 35 (the 2 panels would be on the 35-degree roof, on the 12-degree roof).

Perhaps I need to spend some time on the roof this afternoon to see if I can rearrange my vision a bit (the roof is irregularly shaped, but it may be possible to get 9 panels onto the 35-degree section with some work).

On the other hand, looking at the daily output graphs on the clean-power estimator (at http://www.clean-power.com/cec/default.asp , ZIP code 95128), it looks like the difference is probably not very large.

I did look at the KC125's - the problem is that they're somewhat longer (56 inches vs 51, and don't fit on my roof as well).

It looks like this would cost me no more than a few percent of the output from these three panels - does this sound in the ballpark?

Dan

Just to clarify what the roof looks like, the panels would be organzied like this:

<BLOCKQUOTE><font size="1" face="Verdana, Helvetica, sans-serif">code:</font><HR><pre>
Roof 1 [35 degrees, facing SE)
| X X X X X | <-- roof ends here
| X X X |<-- roof ends here
-----------
Roof 2 [12 degrees, facing SE)
| X X | <-- roof ends here
| X X | <-- roof ends here
--------
</pre><HR></BLOCKQUOTE>

Hi Dan,

The power drop off will be more in the winter than the summer but not a whole lot. Could you possably use a few inches longer standoffs on the top of the 12 deg. panels and a few inches longer on the bottom of the 35 deg. panels to make the angles a little closer?

Is the 12 deg. roof just below the 35 deg roof and connected to the 35 deg. roof?

Have you looked at Photowatt PW750-80 panels to see if they would fit your roof better (in strings of 4)?

Ron-

I did look at the Matrix/Photowatt - unfortunately, the aesthetics weren't adequate for my better half [img]images/smiles/icon_rolleyes.gif[/img]

The roofs are attached, so I can't really tilt the panels on the 12 degree roof. I'm beginning to think that I'll just have to deal with somewhat suboptimal performance on this series of panels. How bad an option is that?

Thanks!
Dan

Its a VERY big deal.

When putting solar panels in series , the current is limited to the weakest performing panel.

Since one of your 3 will be at a different angles , the current , which is proportional to the isonalation will be less and you will be taking 5-7% hit ALL THE TIME !!!

How ever you decide to layout your panels , number one priority should be to keep panels in the same string in the same orientation , make them side by side for the string if necessary

Henry