[RE-wrenches] PV harvest in grid-tied systems

[William Miller]

Friends:

There has been recent discussion on this forum about PV production in 
grid-tied with battery systems.  I have been faced with this same problem 
in a 3 XW system installed in 2009.

The customer's power bill never went down.  PV harvest was abysmal.  The 
system would create great short circuit current but would not harvest into 
the batteries.

It is starting to appear the XW firmware was at fault.  The inverters would 
charge the batteries too high so the charge controllers would back 
off.  Upgraded firmware seems to be helping, but the data set is still limited.

Remember this:  just because a PV system can produce does not mean it 
will.  The charge controller knows only one thing:  battery voltage.  If it 
is high, production is curtailed.

Off-grid production will also be reduced is consumption is curtailed.

Charge controllers that can be set for grid-tied applications help, but 
only if the inverter(s) do not keep the battery voltage too high.

William Miller


Miller Solar
Voice :805-438-5600
email: william at millersolar.com
http://millersolar.com
License No. C-10-773985