Options for Grid-Intertie System

 Hi,

I am considering installing a 4kW grid-intertie, solar PV system. I am
trying to future-proof the system if at some point I elect to cut the cord
with our local utility. I am leaning toward installing a system with a
small battery bank and suitable controller/inverter for this reason. It
seems to me that going with a SunnyBoy or Xantrex inverter would be a waste
of $$$ based upon the potential for someday going off the grid. Plus, I'd
hate to rewire an array from high VDC to low VDC if I was to someday switch
out inverters using the SMA Sunnyboy.

Here's my questions:

I assume that if I go with an Outback or Xantrex Inverter that work in off-
grid and on-grid scenarios, I need some form of battery bank for them to
operate?

Should I just keep it simple and go with grid-intertie for now? Not having
battery backup is not a big deal, our grid has been quite reliable (close
to sub-station.)

Does anyone currently use Outback Inverters? They just got UL approval for
grid-intertie.

Appreciate your opinions.

Thanks!

  The cost of a different inverter in the future is trivial compared to the
cost of the panels. Technology continues to improve so you may be better off
with a batteryless inverter system for now rather than go through the hastle
of getting appropriate batteries and their tender care. Then should you go
off grid, get anew inverter then.

If however you want backup should the grid fail, then you might consider the
batteries now and the Xantrex SW series. However, you would in that case not
go with expensive batteries since adding extra batteries a few years from
now is unwise, better to start with a fresh string.

I have the Trace SW series and the Prosine series. Work well. I have never
used Sunnyboy. Nor have I used Outback.

Simon

 Hi Simon,

 If I knew that sometime in the next 5 years someone would develop a
charge controller that would work with high DC voltages, I wouldn't
hesitate to just go with a Sunnyboy for now and replace it later IF I
decided to go off-grid.

It certainly would make sense for someone to develop a higher DC voltage
controller to keep wire sizes down to a minimum for longer runs. My
panel array will be a good 100' from the house.

Thanks for the reply,

Alan




saminsilver@yahoo.com wrote in

 Yes , High voltage is good for wire sizes ...

BUT,

Its BAD for getting the most out of your array due to panel mismatches ...
What you say , that can't be !! read on ...

When you wire many panels in series , the current flow will be limited by
the weakest panel. Manufactures spec there panels -3%+5% for a typical Si
panel. So if you have one weak panel in a string of 12 or 24 series
connected panels , the entire string acts like all 12 or 24 panels are weak
!!.

In a low voltage array , you can current match the panels so the
weak/typical/strong are all in there own string ( 2 or 4 to a series
string), no can do with a Sunnyboy !!

You can control wire size ... just spend a few extra dollars and get the
correct gauge wire .. you CAN'T control what the manufacture sends you ,
your stuck if the panels aren't closely matched.

I perfer to have the ability to build the best performing net watts to the
grid I can , and that means 48V nominal arrays and Xantrex Sunties.
Sunnyboys are better at raw efficiencies , but with any difference in panels
greater than 2% , the Suntie wins (correct wire size of course). With my
current array , the 155 watt rated panels (36 of them) were from a low of
146 watts to a high of 179 watts , computed gain from using the Suntie was
5% with these arrays ..