I have a 10 Sharp NT-175U1 modules in my solar pv array and I am planning to expand the system by adding two more modules. However, it looks like my supplier can provide me only Sharp NE-170UC1 modules.
What's the effect of using dissimilar modules on energy production?
Comments
First, "when two dissimilar modules are wired in series, the voltage is ... additive, but the current will be only slightly greater than the current produced by the panel with the lowest current output in the series string."
-Photovoltaics: A Design and Installation Manual by Solar Energy International
The characteristics of your current modules, the NT-175U1, are as follows:
Vmp=35.4, Imp=4.95
The characteristics of the proposed alternative, the NE-170UC1, are as follows:
Vmp=34.8, Imp=4.90
As stated above, voltages will be additive while the current will trend down toward the lesser number. Thus, the trend-down will be, roughly, from 4.95 Amps to 4.90 Amps.
As it stands now, each string has an output of 1,752.3 Watts ([10*35.4]*4.95).
If you were to expand your strings using the NT-175U1, each string would have 2,102.76 Watts ([12*35.4]*4.95).
By mixing the modules as proposed, each string would have 2,075.64 Watts ([10*35.4+2*34.8]*4.9).
Therefore, your loss from mixing modules would be only 27.12 Watts. Not as bad as one might've thought!