I have a question about inverter startup relating to selecting panels and their configuration. Panels will be attached to a Sol-Ark 15K inverter, which has a 125v start-up threshold. Comparing different bi-facial panels which are in the 400w to 475w range (ignoring any bi-facial gain for now), I was looking at possible configurations via the Sol-Ark online sizing tool and wanted to get some advice.
Let's say Panel A is 475w and I can put 10 per MPPT in 5S2P configuration, and Panel B is 400w and I can put up 11S. This gives ~14.2kwh with Panel A and ~13.2kwh with Panel B. But the Vmp for the array with "A" is 225v, and for "B" it is 341v.
What I am wondering is whether the 225v set-up would be likely to lose much time each day in low-light conditions if the voltage is below the start-up threshold, which is ~56% of the voltage under STC, whereas with "B" the start-up represents about 36%. What I mean is, how quickly to panels tend to hit a certain level of their Vmp? I am thinking about whether it is important to go with a higher voltage configuration because where I live (around 47 degrees N) the winter days are short, so if wiring more in series would get me a longer window to generate power each day, then option "B" might be better for me than the higher theoretical output of "A", since in the summer when it makes max power I should have watts to burn anyway. Or is the Vmp of either configuration so much above the start-up of 125V that it really doesn't matter? On a side note, if anyone has experience with bi-facial panels in winter and wants to tell me I'm wasting money on them and should just max out on regular panels, feel free: I haven't bought the panels yet (they will be ground-mounted).
Let's say Panel A is 475w and I can put 10 per MPPT in 5S2P configuration, and Panel B is 400w and I can put up 11S. This gives ~14.2kwh with Panel A and ~13.2kwh with Panel B. But the Vmp for the array with "A" is 225v, and for "B" it is 341v.
What I am wondering is whether the 225v set-up would be likely to lose much time each day in low-light conditions if the voltage is below the start-up threshold, which is ~56% of the voltage under STC, whereas with "B" the start-up represents about 36%. What I mean is, how quickly to panels tend to hit a certain level of their Vmp? I am thinking about whether it is important to go with a higher voltage configuration because where I live (around 47 degrees N) the winter days are short, so if wiring more in series would get me a longer window to generate power each day, then option "B" might be better for me than the higher theoretical output of "A", since in the summer when it makes max power I should have watts to burn anyway. Or is the Vmp of either configuration so much above the start-up of 125V that it really doesn't matter? On a side note, if anyone has experience with bi-facial panels in winter and wants to tell me I'm wasting money on them and should just max out on regular panels, feel free: I haven't bought the panels yet (they will be ground-mounted).
