Here is the way I figure this kind of problem out. (1) Old modules. Figure out the number of cells and the cell size. For example 72 cells, 100 mm (4") square. (2) New module. If you can, find a module with the same number of modules and same cell size. (3) Make sure were are talking the same PV Cell material (crystalline Si, poly or single) To first order, the two modules should have nearly the same characteristics: Voc, Isc, Vmp and Imp. You should be able to build a new string with the same number of modules. Caveat: older modules will show lower Isc due to the fact that there have been significant advances in surface treatment (AR coating, surface etching) and in the case of poly special treatment of the wafer (heat treatment plus H2 gas?). Failing that, try to match up total number of cells in the string, keeping cell size the same. I don't have the SW data at hand but it doesn't look like they are a good match. Don't give up on SW175s. There may be someone who has some lying around or the precursor Shell Solar 175-PC. You might have to fixture them with new connectors. - Peter Peter T. Parrish, Ph.D., President California Solar Engineering, Inc. 820 Cynthia Ave., Los Angeles, CA 90065 CA Lic. 854779, NABCEP Cert. 031806-26 [email protected] Ph 323-258-8883, Mobile 323-839-6108, Fax 323-258-8885
_____ From: [email protected] [mailto:[email protected]] On Behalf Of William Miller Sent: Saturday, January 15, 2011 10:51 AM To: RE-wrenches Subject: [RE-wrenches] Matching modules into Xantrex GT Friends: I have a client with a Xantrex GT2.8 inverter. Feeding it are 8 Solar World SW175 modules. This is half the modules that this inverter can handle. The client wants to realize the full potential of this inverter. Adding 8 additional SW175 modules would be ideal, but they are no longer manufactured. I need to find a group of modules to match the 175s. I am contemplating 9 SW240s. The specifications for this match up are below. I imagine the IV curves are similar for these two modules as they are the same chemistry and the same manufacturer. 8-SW175 9-SW240 Voc 403 382 Vmp 283 275 Imp 4.95 7.87 Pcsi 1252 1715 Ptotal 2.967 Might this match be close enough? I know this over-powers the inverter slightly. I imagine that the Xantrex will self regulate this very rare over wattage condition. Comments? William Miller Please note new e-mail address and domain: William Miller Miller Solar Voice :805-438-5600 email: [email protected] http://millersolar.com <http://millersolar.com/> License No. C-10-773985
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