My installer has specified JA Solar 395w panels for use with the 5kw gen 2 inverter set up with an east/west 2 string array - 10 panels each side. There will be 2 9.5 batteries installed.
Max current of the panels is specified at 12.81 A (IMPP) whereas the GE gen 2 hybrid seems to be 11 A max input. Has the installer made a mistake please? Electrical work is not my area of expertise but I'm keen to understand what I'm reading on the spec sheets.
Cheers
sponev Should be fine. The inverter will limit its current draw to 11A per string. Selecting the higher performance panels gives you more energy throughout the day, even if there is some clipping at very sunny times.
Ah I see, so not a safety concern as such. So we only lose a little bit of efficiency when the panels are at peak output? Is it worth considering an alternative inverter or is that difference in max current relatively minor in the grand scheme? I'm new to this so no real feel for the various parameters yet.
I think I also saw another thread that the GE inverters can work a little bit above the specified maximums but no idea if that's correct?
Thanks for your help, appreciated!
Oversizing the array is now fairly standard. If you're that worried and have the roof space, you could go for a slightly higher number of less efficient panels in each string - same power with a higher voltage and lower current. However, that may cost more than you'll actually save.
stevelewis Understood, thanks. The edge cases seem to be a pain to evaluate fully. We do have additional space but I guess we'll stick with what we've been quoted. Stepping outside of the GivEnergy ecosystem gets expensive as does installing additional albeit lower powered panels. Cheers.
Still got a few concerns here if anyone can help please. Another supplier suggests the following, so a power reduction all the time, not just at peak sunny times. Is this correct please and do I need to review the panel/inverter selection (see above) with my preferred installer? I'm keen to stick with the GivEnergy products but may need to re-think if what the other installer is saying is in fact correct. Thanks again.
"Usually you do want to oversize an inverter which will cause some clipping which is balanced out by the inverter working more efficiently the rest of the time, however this is a different scenario as clipping as its regularly discussed in the sense of oversizing is to do with the voltage of the panels, where you would only see the system clipped at peak production. Clipping in a current sense however will mean that you lose that 15% production most of the time, as the current of the panels will just about always be above 11A. To get around this you'd want to fill the same area with a larger number of panels which have a lower output, to get rid of this"
If it helps I can inject Pseudo PV into my GE hybrid on demand. This has the potential to add 10A of "fake PV" onto of whatever the PV is doing on its own.
The MPPT tracker only takes what it can, so any beyond 11A is simply not used (it's not burnt off as heat or anything either)
I was always under the impression that its the String Voltage that's the limiter not the current so the string cannot exceed 580V.
Forgot to mention, GE answer a query a few days back as to how much DC they can handle:
3.6 hybrid can do 6.2kW PV (3.6 + 2.6) until the battery is full then self limits to 3.6
5 hybrid can do 7.6kW PV (5 + 2.6) until the battey is full then self limits to 5.
So you can read between the lines that it's the DC to AC converter part that's the limiter rather than the PV side.
hoggy Thanks for that. My limited experience also suggested that it was voltage as a limiting factor but electrics is not my expertise at all. I'll see what the GE support guys say just to be on the safe side. Cheers
sponev That's not what I'm seeing on my system. You oversize the array to allow for the fact that the sun is rarely (if ever) at broadside to the array and the array output reduces with age. Inverters tend to be most efficient near their full power output, so why would you want to oversize the inverter? Inverter output is usually limited by export constraints to 3.68kW. The string voltage must never exceed the inverter's max input voltage or it will damage the inverter (the string voltage is usually higher at low temperatures). But a higher string voltage will reduce copper losses. The string current varies considerably with output power as the MPPT changes the effective load resistance to hunt for the sweet spot. The 11A statement is simply wrong: my two strings are currently running at 261V/4.1A and 324V/2.65A. Depending on geometry, weather, time of year, you might lose up to 15% of production for a brief period on some warm and sunny days when the string voltage is lower and the current is highest. But then that's exactly when you'll have some energy to spare.
stevelewis Thanks Steve. I just spoke with GE tech support and they are saying the same as you - power loss should only be for a very short period at the sunniest times. So we'll push on with what's been specificed.
I can't believe that GE would have released a new inverter which is inefficient across a wide range of conditions where more powerful panels are in use. I guess the alternative supplier is pushing to install their preferred system, SolaX.
Thanks again.