Solar module cell-count [RE-wrenches]

[Bill Brooks]

Joel,

A key to better system design is not directly cell count. Higher cell =
counts make it more difficult to maximize dc voltage into an inverter since
= each module step is so large. Lower cell counts necessitate larger cells
so = that wiring costs are reduced. For larger scale projects, it would be
nice to have 6" to 8" cells so that each string has the highest possible
current = and voltage therefore getting the most power per labor dollar.

Smaller rooftops necessitate smaller cells so that the designer can get =
more voltage per smaller area. Therefore, big systems need big cells and =
small residential systems need smaller cells.

Everyone seems to talk about module power and cell count, but they = rarely
discuss the issue of cell size and current. That's my story, and I'm
sticking to it.

Bill.

Bill Brooks, PE
Brooks Engineering
873 Kells Circle
Vacaville, CA 95688
office and mobile phone: 707-332-0761
fax:707-451-7739
email: billbrooks7 at yahoo.com
web: www.brooksolar.com

> -----Original Message-----
> From: Joel Davidson [mailto:joel.davidson at sbcglobal.net]
> Sent: Friday, May 11, 2007 2:37 PM
> To: RE-wrenches at topica.com
> Subject: Solar module cell-count [RE-wrenches]
> 
> 
> Wrenches,
> 
> A lot of wrenches only install PV systems with batteries, but the vast
> majority of PV megawatts installed in the U.S. are non-battery grid-tie
> systems. 36- and 72-cell solar modules for battery charging make sense,
> but
> is there a better cell-count for systems with 300 to 600 VDC input
> inverters? Some installers prefer the Sanyo 96-cell module or the 50-cell
> Mitsubishi module or the Kyocera 54-cell module or the Sharp 60-cell
> module
> and some just buy whatever module is available. Is there a technical
> advantage to one module cell-count over another or is the growing number
> of
> module cell-counts indicative of a disconnect between module and system
> designers?
> 
> Joel Davidson
> 
> 


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