[RE-wrenches] Bi-facial Open Circuit voltage testing

[Jason Kechijian]

Hey wrenches,

Does anyone have any guidance to which values to use when testing open circuit voltage on bi-facial modules, considering you take the temperature reading from the cell vs. the back sheet? Also, what would be the correct module Voc to use since there are values for both the front and back?

405W Module: Front/Back
Pmpp: 405 / 285
Vmpp: 40.89 / 41.10
Impp: 9.91 / 6.94
Voc: 48.42 / 46.99
Isc: 10.38 / 7.28
Module efficiency: 19.7% / 13.9% 
Temp coefficient Pmpp: -0.3528%/ºC
Temp coefficient Isc: +0.0400%/ºC
Temp coefficient Voc: -0.2769%/ºC
Nominal: 44+/-2ºC

I was using the front Voc and Voc temp coefficient, but I am getting some results which are not in line with the 5% of expected.

Jason D. Kechijian, LEED AP
NABCEP Certified PV Installation Professional™