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Unisolar SMA deisgn quandry
My firm is rectifying a horrendous install (many skinned PV cables, wrinkled laminates etc) by a now defunct high profile installer of hybrid PV/thermal systems.
There are three strings of Uni-solar laminates on a Sunnyboy 4000. Two 9 strip strings of PVL136s (Vmp 33.0/Voc 42.2/105W) and one 12 strip string of PVL68s (Vmp 16.1/Voc 23.1/ 68W)
The tech support for the SMA inverter (Unisolar PV is belly up) said the imbalance in the strings would average out, this has got to come at a cost of efficiency.
My question:
Why would the designer use only 12 of the PVL68s? With a Vmp of the string currently at 193.2 and the PVL136 strings at 297,
would it make sense to add an additional 2 PVL68s to bring that string to 230V reducing the imbalance, increase the the operating time (the SB4000 has a starting voltage of 260v and being asthetically better as the additional two strips would align with the strings above?
There are three strings of Uni-solar laminates on a Sunnyboy 4000. Two 9 strip strings of PVL136s (Vmp 33.0/Voc 42.2/105W) and one 12 strip string of PVL68s (Vmp 16.1/Voc 23.1/ 68W)
The tech support for the SMA inverter (Unisolar PV is belly up) said the imbalance in the strings would average out, this has got to come at a cost of efficiency.
My question:
Why would the designer use only 12 of the PVL68s? With a Vmp of the string currently at 193.2 and the PVL136 strings at 297,
would it make sense to add an additional 2 PVL68s to bring that string to 230V reducing the imbalance, increase the the operating time (the SB4000 has a starting voltage of 260v and being asthetically better as the additional two strips would align with the strings above?