grid powered solar panel usless in blackout. Alternative use to charge battery?

Re: grid powered solar panel usless in blackout. Alternative use to charge battery?

st2288 wrote: »

Thanks to Hurricane Sandy, we were out of power for 7 days. Meanwhile I have 9KW grid tie system tie to the LIPA,which became totally useless..Of the 9kw system , I have a sting of 5 200watt panels (each with micro-inverters) which I can access quite easily. (The string of 5 micro-inverter is isolated from the rest of the system) They are tie into a circuit breaker to my main circuit panel.
My question:
Can I put a Y-cable on the 200 watt panels (one feeding the micro-inverter, and the other one wired parallel with other solar panels) I will use the parallel wired panels to hook up a solar charger to charges a bank of deep cycle marine batteries. I will then attach the a pure sine wave inverter to feed my transfer switch.

I have a shut off breaker for the micro-inverters which will be off when I need to use the panels to charge the battery bank.

Will this work?

Thanks
Thanks

I have contemplated the same question, but never tried it. I wondered if the non functioning inverter would short the output of the panel. It could be done with a Latching Relay where you just took the inverter out of the equation.

Re: grid powered solar panel usless in blackout. Alternative use to charge battery?

inetdog wrote: »

The one thing which you want to avoid is to have two different MPPT type devices connected to the panels at the same time. They will fight over who gets the power, creating an unstable situation. But the inverter or charge controller which is switched off should not present any load to the panels (except maybe a trivial amount to power the inverter's controls.)

no fight involved with no grid power being present. i believe the question might be one of how the gt inverter circuits would react if the pvs were paralleled. to me i don't think the gt inverters would know the difference, but this is a circumstance when the grid is up of having a common pv source to separate inverters and then back to a common load. i'm not real sure if the same rules would apply to these gt inverters as they would to controllers and would be a question that would warrant an answer from some of the inverter manufacturers if there would be any problems in doing this. if it is a problem then i would say you could still be able to wire them in parallel with the main entrance breaker to the grid to remain off and the physical access of connecting/disconnecting of the paralleled pvs to be done at the pvs that would need to be changed over each time depending on if the grid is desired or not at the time.

st2288,
what would you have done with the paralleled pv outputs if you had it at the time? do you have a large battery bank and cc to run off of the pvs, plus an inverter for key ac appliances and if so then what would be maintaining the batteries when you are grid tied as those pvs would now be disconnected from the battery bank(if said to not be viable in being connected to the cc while grid tied)? people that opt for gt for its higher efficiency take the chance of a long term outage occurring that would also make the system useless

Re: grid powered solar panel usless in blackout. Alternative use to charge battery?

I guess it'll always be a roll of the dice as to whether your PV's are involved in the disaster in some way. The one time in 30 years I could have used the PV.s they were covered with 3" of ice for 10 days. I opted for the Inverter and a bank of 4 GC-2's and a 75 Amp charger for my Honda. A couple gallons of gas I am good to go. It looked like in Sandy if you didn't have the Inverter mounted on the roof you were out of luck.

Re: grid powered solar panel usless in blackout. Alternative use to charge battery?

yes, i forgot about the backfeeding on inverters. that can be shakey to do if you don't know what you're doing.

i don't think he had this in mind though as he's seeking a simpler solution in paralleling the pvs for a battery based dc solution for batteries. the fact that all of the pvs would be paralleled while at the same time selling to the grid is the problem. the pvs may need to be auto disconnected when the inverters are feeding the grid. if they feed the grid then they aren't being used to upkeep the batteries in the first place. maybe your real solution is to take some of the gt inverters out of line and have those pvs feed a brand new inverter that can sell to the grid with battery backup without even acknowledging that some of the so called ac panels may backfeed the new inverter adding extra capacity available while the sun shines.

Re: grid powered solar panel usless in blackout. Alternative use to charge battery?

The overriding problem is that a grid tied inverter is a current source. When it's connected to the grid there is a nearly infinite sink for that current to flow into at a clamped voltage, but in a microgrid environment you must have some way of throttling back the inverter's output to match the demands of the load. You cannot draw current on demand at a constant voltage from a GT inverter like you can from a battery inverter. Also, what happens when the demand exceeds the output of the inverter? This is why off-grid systems use batteries, to buffer the output of the inverter and supply current on demand to the loads. These forums are chock full of schemes to fool a GT inverter into thinking the grid is up without using batteries or by using tiny batteries compared to the demands of the load. To date and to my knowledge, none have been successful.

UL1741 is there to ensure that a GT inverter does not try to energize the grid when the grid is down, but it is in a way just legislating what physics has already decreed. When the grid is down it appears a a virtual dead short to the inverter because of all the loads still on line, and it would require nearly infinite current output to bring the voltage up. UL1741 notwithstanding, you aren't going to power up your city's grid with your puny little 5kW inverter.

There is a right way to do this, but it ain't cheap.

Re: grid powered solar panel usless in blackout. Alternative use to charge battery?

is that 10a at 12vdc, 24vdc, 48vdc, 120vac, or 240vac? good to have when there's nothing else in any case.

Re: grid powered solar panel usless in blackout. Alternative use to charge battery?

inetdog wrote: »

That is 10 amps at 120 volts, I believe. Since the exact same backup output is available from the 3000, 4000 and 5000 models, I do not think it could be 10 amps at 240 volts. The PV you would normally attach to the 3000 just could not handle it.

It is a single 120V outlet mounted under the inverter. I saw it at SPI. I don't know if it's available in the States yet.

Re: grid powered solar panel usless in blackout. Alternative use to charge battery?

niel wrote: »

you were at spi in pa?

I was at Solar Power International in Orlando in September.