Mark,
I believe that your plan would fail because you are forcing power to
flow through the XP inverter backwards to charge the batteries. I don't
believe the XP inverter can do that. The grid tied inverter would
probably connect then immediately shut down, or connect and immediately
ruin the XP inverter. It would work if you had a inverter with a
bidirectional architecture like a Magnum, Outback, or Schneider
inverter. But even then you'd have a hazardous situation because the
cooling water is going to evaporate.
Kent Osterberg
Blue Mountain Solar
On 2/29/2020 3:27 PM, Mark Frye wrote:
I have 2kw of grid tied PV on my house.
Suppose I:
- Open the main breaker to disconnect from the grid
- I open the PV breaker
- I connect a small good quality inverter like an Exeltech XP 500 to
one of the phases of the service (120 VAC)
- I put a small battery pack, 100 AH at 24 VDC on the inverter
OK so far, I could run some small loads for a relatively short period
of time before the batteries get low
-I have a PLC with an AD input and DA output. On the input I measure
the battery voltage, on the output I control a SCR. The SCR controls a
2kw immersion heater sitting in a big bucket of water. The PLC has a
scan time of 2 mS and I program it to increase the duty cycle of the
SCR as voltage of the battery rises above 24 VDC.
OK so far nothing has really changed from above.
- I close the PV breaker, the GT inverters see the battery inverter,
sync and connect after five minutes.
Voila, I can run house loads from 0 to 2kw with my existing GT PV with
the balance of energy dumped as needed to the immersion heater.
Right?
Mark Frye
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