Dan: Thanks very much for the detailed analysis. So the short answer is that a 48 v micro-inverter will be compatible with either module. I am old school and like a little more head room than that, especially since we have not learned yet if inverter damage will occur on overvoltage. I am anxious to try the Power One units. Anyone else tried these yet?
William -----Original Message----- From: re-wrenches-boun...@lists.re-wrenches.org [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of Exeltech Sent: Monday, September 30, 2013 6:01 PM To: RE-wrenches Subject: Re: [RE-wrenches] Using legacy modules on micro-inverters William, PV temperature coefficient of voltage is a function of the number of cells in series. For 72 cell PV (or two 36-cell PV in series), the coefficient is 2X that of 36 cells. Two SP75 in series, in an ambient temperature environment of -10C, and presuming a cell temperature of -10C at reduced light and a low solar altitude to minimize cell heating, would exhibit nominally 45.4Voc, and 35.6Vmpp respectively. Two SP75 in series, in an ambient temperature environment of 38C, and presuming 1000 W/m^2 orthogonal to the PV module at solar noon, would yield nominally 36.6Voc, and 28.7Vmpp respectively. Nominal cell temperature under the latter circumstances would be 69.3C, presuming a rooftop mount, 6-8" above the roof surface, with 1.5 m/s or less wind speed, and perfectly orthogonal to the sun at solar zenith. Two SQ150 under the identical cold ambient conditions would exhibit 44.4 Voc, and 34.8Vmpp. Two SQ150 under the identical hot ambient conditions would exhibit 36.1Voc, and 28.3Vmpp. Nominal cell temperature for the SQ150 under the latter circumstances would be 70.5C, with the same presumptions as above. Very slight differences exist between two SP75 in series, and one SQ150, but as you alluded to below, they're close enough to be considered essentially identical. Regards, Dan _______________________________________________ List sponsored by Home Power magazine List Address: RE-wrenches@lists.re-wrenches.org Change email address & settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org List rules & etiquette: www.re-wrenches.org/etiquette.htm Check out participant bios: www.members.re-wrenches.org