My system has 2 MPPTs but can take 2 strings per MPPT. I will have 4 strings of panels and I'm trying to work out the advantages/disadvantages of using 2 strings per MPPT versus using another inverter/micro-inverters for the 'other' 2 strings... would appreciate any thoughts/pointers.
Thanks
Ian
Gary does solar has a good video on microinverters vs string inverters. My takeaway is that microinverters give you independence of operation, so if your roof has a lot of shading them individual panels can still work, but the big downside is that if the microinverter fails then its likely to be a scaffolding & expensive replacement (irrespective of the 20 year warranty) whereas a string inverter is much easier to replace but is a single point of failure.
I would personally choose optimisers over microinverters if you are wanting to resolve shading/panel orientation issues.
In terms of strings per MPPT, the more panels you have on a string (i.e. less strings) the less solar it requires to light up the solar generation in the morning/evening.
If you have 2 strings per MPPT then doesn't that mean you can only optimise generation for the pair of strings, e.g. if the strings are on differing orientations.
In general less equipment/inverters means less to go wrong
My experience of 2 strings on the 1 MPPT was that it didnt really work as in my case the strings were same orientation but not equal size so the larger string was dragged down to the performance of the smaller string. I suspect the same would happen if they were different orientation/shading. In the end we joined the 2 strings together as they were still within spec for the inverter and boom, full performance was achieved.
geoffreycoan Yeah I follow Gary thanks. This is more specific than he does.
The panels in question will be on a roughly E/W orientation shed c. 4kwp each side. We'll have already used the 2 MPPTs (in single string each) so it's whether to go for (a) 2 strings per MPPT (b) another inverter; or (c) microinverters.
My installer is not keen on (a) and says it will likely hit performance, but I was just looking for other opinions. We're already running AC to the shed so it sort of makes sense to use that cable to bring the energy back too.
The microinverters would be instead of another inverter (rather than covering shading) and would be easy to change since on the shed.
Thanks for your thoughts
Cheers
Ian
Hopeful Thanks, yeah that's my installer's thoughts - great you confirm with experience! I'll stick with AC return and micro inverters I think ... assuming the DNO doesn't play up!
Cheers
Ian