Solar panel question - PeachParts Mercedes-Benz Forum

davidmash · #1 06-13-2021, 12:08 AM

Quote:

Originally Posted by Dubyagee

Like I said, grid tied uses the grid as a “battery”. Thats why it shuts off when the grid fails like a battery powered inverter would if the batteries failed.

Panels feeding an inverter without a battery would have voltages all over the map. The battery helps smooth out voltage variances. Like a capacitor.

When a grid tied system loses the grid it shuts down to protect the inverter and not back feed the grid. If there was a battery bank in between the panels and inverter and the inverter had an automatic transfer switching system it would keep power on until the batteries were drained. A larger group of panels would lengthen the battery time.

Its not a legality issue, its a financial one.

I misunderstood the first part. My apologies.

If I have a off the grid house with solar panels, I get power from the panels do I not? Assuming yes, why can that not be done on the grid and just have a switch, like they do for a house that has a generator, which cuts off power from the grid?

ah-kay · #2 06-13-2021, 01:18 AM

Quote:

Originally Posted by davidmash

I misunderstood the first part. My apologies.

If I have a off the grid house with solar panels, I get power from the panels do I not? Assuming yes, why can that not be done on the grid and just have a switch, like they do for a house that has a generator, which cuts off power from the grid?

Get a better engineer, not a sale person. The inverter for grid tied and off grid system is DIFFERENT. That is why you can't turn off the grid and 'turn on' your solar panels. The panels doesn't work like a generator. Enough said.

Diseasel300 · #3 06-13-2021, 08:53 AM

Quote:

Originally Posted by davidmash

I misunderstood the first part. My apologies.

If I have a off the grid house with solar panels, I get power from the panels do I not? Assuming yes, why can that not be done on the grid and just have a switch, like they do for a house that has a generator, which cuts off power from the grid?

You have misunderstood a lot. An off-grid home running solar panels has a huge battery bank. Your house is powered from the battery bank in this case. The solar panels are charging the batteries. You do not take power directly from the panels in any case at any time. Ever.

You also cannot have the solar panels operating in parallel with a generator. The inverter will cause the generator AVR to literally go crazy. The generator must have a load on it and the inverter does not understand that, if you back-feed the generator hard enough, you will cause the windings in it to fail. The grid-tie inverter is not designed to "share load" with a generator, it is designed to dump the maximum power it can back into the grid. Seen it happen many times by people who thought they were clever enough to trick the grid-tie system, it isn't pretty and the load in your home gets real unhappy when it does.

If you want a true backup system, you need a generator. Even off-grid solar systems have a backup generator for when the system is down for maintenance or on cloudy/snowy days when there isn't enough sun to keep the battery bank charged.

davidmash · #4 06-13-2021, 11:30 AM

That's why I am asking questions, because I don't understand. But that's for sharing.

Not asking why panels and generator can't be used in parallel, I'd be looking to use one or the other.

I did find what seems to be a very detailed explanation here.

https://arstechnica.com/civis/viewtopic.php?f=26&t=1402629