Solar PV System Off Grid Options

I'd like to have the option to switch the use of my solar PV grid tied system to off grid (and back). I'm not really concerned with discussing how the cost "is worth it" or not. Just how it can be done.

Some ideas:

Some type of manual switch that can be used to move from the grid to the solar or generator supplied power to the house. A source of power to bootstrap the inverters would be needed, but that could be the generator, or even a 12 volt car battery and inverter.

The nighttime backup plan is a 8 or 9kW generator like this one that burns natural gas, propane or gasoline, and is big enough to charge a 6.6kW LEAF.

Yes, it would be neat to use the LEAF to power the house, except an extended power outage (earthquake, fires, terrorism, other disaster) would likely not leave any power in the LEAF. I have to be able to recharge the LEAF.

You need something like a Sunny Island and a battery bank to do this.

The Sunny Island will probably be about $4k for something that will do a about 4 kW maximum.

I would expect the lead acid battery bank that will support that to cost about the same.

And none of this has been tested or recommended with Enphase micro inverters...

You will need to find a grid tie inverter that supports micro grid or island operation for automatic operation. There are backup power switches but it's hard to find information on ones that support both grid tie operation and micro grid.

See http://certs.lbl.gov/certs-der-micro.html" onclick="window.open(this.href);return false;

drees said:

And none of this has been tested or recommended with Enphase micro inverters...

Click to expand...

Maybe I should call them first. They might have a few ideas.

TonyWilliams said:

I'd like to have the option to switch the use of my solar PV grid tied system to off grid (and back). I'm not really concerned with discussing how the cost "is worth it" or not. Just how it can be done.
Some ideas:
Some type of manual switch that can be used to move from the grid to the solar or generator supplied power to the house. A source of power to bootstrap the inverters would be needed, but that could be the generator, or even a 12 volt car battery and inverter.
The nighttime backup plan is a 8 or 9kW generator like this one that burns natural gas, propane or gasoline, and is big enough to charge a 6.6kW LEAF.
Yes, it would be neat to use the LEAF to power the house, except an extended power outage (earthquake, fires, terrorism, other disaster) would likely not leave any power in the LEAF. I have to be able to recharge the LEAF.

Click to expand...

+1! I brought this up in the solar thread so let me know if we can do it. After your blackout, I think you realized how we need to be able to do this. My micros are attached to the back of each panel.

I was looking for the same info and found this site:
http://www.wholesalesolar.com/back-up-power.html" onclick="window.open(this.href);return false;
which explains some of the different options. Also, it says if you add a solar panel to the existing system, you qualify for the 30% federal tax credit. That would be nice for us, since we were burned by being early adopters. Our rebate was a flat $3k, new rebate announced shortly after we put in our system, oh well.

solartim said:

I was looking for the same info and found this site:
http://www.wholesalesolar.com/back-up-power.html" onclick="window.open(this.href);return false;
which explains some of the different options. Also, it says if you add a solar panel to the existing system, you qualify for the 30% federal tax credit. That would be nice for us, since we were burned by being early adopters. Our rebate was a flat $3k, new rebate announced shortly after we put in our system, oh well.

Click to expand...

Thanks Tim!