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Quick question about solar power, transfer switches, and generators.

billybob_81067

billybob_81067

Redneck
Joined
May 19, 2020
Member Number
150
Messages
851
Loc
Southeastern Colorado
So all these rolling blackouts freaking people out got me thinking today... I have a grid tied solar system on my house that has to have incoming line voltage in order for the panels to generate electricity. If a person were to install a proper transfer switch and backfeed your panel with a generator couldn't you then use the solar panels to produce electricity because the inverter would be seeing the voltage from the generator?

A transfer switch would be best placed after your meter and before your main box right?

After the initial startup load and waiting for the panels/inverter to come online then your generator would have it easy as long as you had good sunlight and normal power loads correct?

Let me know if I'm missing something.
 
If it is cloudy, would it not be better to use the generator to power the house?
 
Roktoy829 said:
If it is cloudy, would it not be better to use the generator to power the house?
Click to expand...

That's the thing though, I basically will be using the generator to backfeed the panel and power the house, but wouldn't the solar panels kick in what they can too? If the panels themselves make enough to power everything then the generator would be living the easy life and the load and fuel consumption should be down. If the sun went behind a cloud or went down then the generator should take over the load then right?
 
I was not aware of a solar panel system like that. It sounds plausible that it should work.

I only thought solar panels worked strictly from the sun moving the photogenic cells to create the electricity.
 
It sounds like the grid is the battery bank. Are you sure whatever power you don't use isn't just sent back into the grid to supply other homes?
 
billybob_81067 said:
No I don't want a battery bank to maintain.
Click to expand...

A junk yard I used to live near would get random shit in, supposedly the 8 55gal drums of 18650 cells they bought were from truck and trailer accidents, I bought 20 pounds for ten bucks. They aren't much maintenance and that was cheap as fuck for what they were, they haven't gotten any in a while and if they do again I'll buy a whole drums worth. they fetch a buck a piece on ebays for vandwellers and diy powerwall builders once they are charged discharged and rated for capacity. fuck keeping tabs on a bank of lead acid cells unless its a forklift battree.
 
Roktoy829 said:
I was not aware of a solar panel system like that. It sounds plausible that it should work.

I only thought solar panels worked strictly from the sun moving the photogenic cells to create the electricity.
Click to expand...

The panels themselves still work the same, you can either have a stand alone battery bank system that the solar panels create the DC voltage to charge the batteries and then an inverter converts that DC voltage into a usable AC voltage for your appliances.

OR you can have a grid tie system where your house is still hooked to the grid and the panels go straight into a "smart" inverter. This inverter must see line voltage from the grid in order to use the power from the solar panels. As soon as the power goes out though it shuts the inverter off so that you aren't back-feeding power onto the grid. But with a transfer switch and generator I think you could power it back up and then get your panels generating electricity again.

I'm sure there are other hybrid systems out there as well that are still grid tied as well as having a battery bank for emergency power situations. I just don't want the hassle of having to store and maintain the batteries needed to run such a system. And in that regard the grid tie system has been nice. It would just be cool to have a backup plan in case the grid went down for an extended time...
 
Roktoy829 said:
It sounds like the grid is the battery bank. Are you sure whatever power you don't use isn't just sent back into the grid to supply other homes?
Click to expand...

That is exactly what it does. During the day my solar panels produce more than I use and whatever I don't have a demand for is sent back into the grid. During the night I of course pull off the grid because my panels aren't making a damn thing. I was just hypothesizing that if a guy wanted to power up during a grid outage you could have a transfer switch to take your system offline and then feed it with the generator to get the smart inverter back up and running and then your panels would take over the majority of the load for your house. Or would the panels generate too much electricity and not have anywhere to go with it because you wouldn't have the grid to backfeed and end up blowing fuses and other shit?
 
billybob_81067 said:
I just don't want the hassle of having to store and maintain the batteries needed to run such a system. .
Click to expand...

youre making it out to be a lot more difficult and expensive than it has to be, maintaining modern batteries is no more difficult or expensive then maintaining and fueling a generator :homer:
 
billybob_81067 said:
No I don't want a battery bank to maintain.
Click to expand...

Yeah you do. Lithium. No maintenance. You are trying to do the same thing I already do with my motorhome. That wheel has already been invented, and you are trying to take a pie cut out of that wheel. The batteries will put that power to the system you are looking for to keep the solar/inverter working. The right inverter will already have the transfer switching already built in to go from grid power to generator and still be getting the charge from solar. When the lights go out, you don’t want to be fumble fucking around, trying to remember how to get the fridge working again.
 
I know there's a lot more elegant solutions, but wouldnt a simple 12v to 120v inverter hooked to a single battery (only for the signal, not for storing solar power) provide the signal your solar inverter looking for?

But there are much better solutions
 
The reason its shuts off when there is a power loss is so that you don't back feed (energize) the grid if there is someone working on something like downed wires. All you need is a transfer switch and unfortanally you will need a battery and a system to "burn off" the extra power that is produced. You can't just feed power from the panels into the house. Have you looked into the Tesla wall battery? I have not looked closely at it but is seems to work like a whole house battery backup durning black outs.
 
go big, build a vanadium redox (flow) battery. Much better than any lipo battery stuff
:grinpimp:
 
billybob_81067 said:
So all these rolling blackouts freaking people out got me thinking today... I have a grid tied solar system on my house that has to have incoming line voltage in order for the panels to generate electricity. If a person were to install a proper transfer switch and backfeed your panel with a generator couldn't you then use the solar panels to produce electricity because the inverter would be seeing the voltage from the generator?

A transfer switch would be best placed after your meter and before your main box right?

After the initial startup load and waiting for the panels/inverter to come online then your generator would have it easy as long as you had good sunlight and normal power loads correct?

Let me know if I'm missing something.
Click to expand...


I too have wondered about "tricking" a grid tie inverter into thinking it's on a grid and getting it to act as a normal inverter. I'm only curious about going this route because I have some old equipment sitting around and would like to put it to use at a remote property with no utilities. I read the link on why this type of solar and generators don't play nice with each other, but I wonder if you could find some simple signal generator to supply the right voltage and frequency to get the inverter to come on and do it's thing.

The problem with trying to research this stuff is there are quite a few different options on how to do things, but most people only seem to be familiar with one or two, or just with what they are doing, and therefore have no clue what they are talking about if your situation doesn't apply. Kinda like you're already seeing in this thread with people talking about what kind of batteries you should be using :rolleyes:
 
Maybe. On one hand, I doubt the fuel cost / pain of running a generator under light load is much less than handling full load.

Also, it sounds like typically grid tie inverters are designed without any load regulating capability - they put the amount of energy the solar system is generating out at 110 AC, which means that if you tried to trick on or use as a standalone it's not going to work right - sort of like trying to charge a car battery with a arc welder.

Only practical way I can think of would be to use the DC bus to charge a battery bank and then have a standalone inverter. Problem is that unless you run an entirely separate wiring system, the dc bus voltage is probably too high for any of the cheap inverters.

At the end of the day, it's probably easiest to just buy gas for the generator.
 
So without completely jacking this dudes thread, if someone wanted to do a solar install, what options are there for being grid tied to sell excess, but in the event of long term outage having the capability to utilize your solar, with or without storage capacity?
 
sdmuleman said:
Maybe. On one hand, I doubt the fuel cost / pain of running a generator under light load is much less than handling full load.

Also, it sounds like typically grid tie inverters are designed without any load regulating capability - they put the amount of energy the solar system is generating out at 110 AC, which means that if you tried to trick on or use as a standalone it's not going to work right - sort of like trying to charge a car battery with a arc welder.

Only practical way I can think of would be to use the DC bus to charge a battery bank and then have a standalone inverter. Problem is that unless you run an entirely separate wiring system, the dc bus voltage is probably too high for any of the cheap inverters.

At the end of the day, it's probably easiest to just buy gas for the generator.
Click to expand...

What do you mean by load regulating capability? Generators and regular inverters don't "regulate" the load, they just make power available to it. It's the load that determines the power the system produces until you trip a breaker or something. This is another detail people who are into solar but don't know much about electricity often get wrong, especially in youtube videos.
 
billybob_81067 said:
If the panels themselves make enough to power everything then the generator would be living the easy life
Click to expand...

Nope. That's bad. You'll put the pain on your genny if it runs at minimal load. Look it up. They want to run at half load, ideally.
Also, as far as transfer switch between meter and main, most folks put in a sub after the main and put in the circuits you'll run. Better option would be a manual lockout switch on the panel and just add another breaker for the generator. Then it's up to you to know and balance how much you draw.
 
Derp said:
What do you mean by load regulating capability? Generators and regular inverters don't "regulate" the load, they just make power available to it. It's the load that determines the power the system produces until you trip a breaker or something. This is another detail people who are into solar but don't know much about electricity often get wrong, especially in youtube videos.
Click to expand...

GTE is a constant current source, not a constant voltage source. No, gen set/inverts don't regulate load, but they do regulate power output to match load. GTE doesn't - it's outputs as much current as the solar system produces, so if the output exceeds available load you have a problem.

Yes, not well phased
 
suppose this is a better thread to ask in, but I'm looking at this shit and all the inverters I can find look to be generic chinese ones endlessly rebranded, and the ones that aren't are probably just the same boards in a different box
fucking google used to be okay for finding anything, now it just gives you the same monitized adverts no matter what you're looking for
Look for a forum on the shit and all you get is from 2011... just sick of the shit

anyways, what's a good place to look for a grid-tie inverter from?
Don't really care about any sort of power outage backup type stuff. Just looking to buy something without it being a reboxed aliexpress special
 
Thatg9659 said:
A junk yard I used to live near would get random shit in, supposedly the 8 55gal drums of 18650 cells they bought were from truck and trailer accidents, I bought 20 pounds for ten bucks. They aren't much maintenance and that was cheap as fuck for what they were, they haven't gotten any in a while and if they do again I'll buy a whole drums worth. they fetch a buck a piece on ebays for vandwellers and diy powerwall builders once they are charged discharged and rated for capacity. fuck keeping tabs on a bank of lead acid cells unless its a forklift battree.
Click to expand...

So you've found the secret stash of $1 18650s, it's perpetual, and nobody will ever find out. Gotcha.
 
billybob_81067 said:
That's the thing though, I basically will be using the generator to backfeed the panel and power the house, but wouldn't the solar panels kick in what they can too? If the panels themselves make enough to power everything then the generator would be living the easy life and the load and fuel consumption should be down. If the sun went behind a cloud or went down then the generator should take over the load then right?
Click to expand...

I don't know why anyone is answering this except for people who own such a system.

You sound like you're thinking of starting a petrol generator to just 'trick' the house system into moving electrons for you. This sounds like a stupid idea.

Better yet, why don't you get someone that understands your system to take a look and tell you what needs to be done:

I have a grid tied solar system on my house that has to have incoming line voltage in order for the panels to generate electricity.
Click to expand...

WTF is this? This sounds like a design feature for a system designed to have batteries or a generator hooked to it. It also sounds like you don't know how your system operates or what makes it work. So hooking up a generator is the dunce way to maybe make it work but why don't you find out how it actually operates before making modifications?
 
billybob_81067 said:
So all these rolling blackouts freaking people out got me thinking today... I have a grid tied solar system on my house that has to have incoming line voltage in order for the panels to generate electricity. If a person were to install a proper transfer switch and backfeed your panel with a generator couldn't you then use the solar panels to produce electricity because the inverter would be seeing the voltage from the generator?

A transfer switch would be best placed after your meter and before your main box right?

After the initial startup load and waiting for the panels/inverter to come online then your generator would have it easy as long as you had good sunlight and normal power loads correct?

Let me know if I'm missing something.
Click to expand...

Possible as long as:
1) Your demand is never less than the panels are putting out so that the generator is always generating a little bit.
2) The generators THD is low enough that the inverters/microinverters are happy. The sine wave from a normal small genset is typically pretty bad compared to the grid, especially when lightly loaded. THD is typically at the IEEE limit of 5% only at full load. The inverters would likely fault or error out, or could possibly smoke out.
3) Your loads are really well balanced between the legs. Your inverters are likely only connected to two legs and not the neutral (240v) so there isn't really a way to keep the neutral at +/-120 of each leg. This is what I'd worry about the most because the windings in the genset would be responsible for making up any difference since the AVR is probably not controlling each leg's voltage. In a home with lots of 120v loads this could be a big challenge and the possible risk is getting way under and over voltages to your 120v loads. The inverters aren't going to know the difference so they won't trip off if something weird is going on. You might be able to connect the secondary only of a small split phase transformer to even this out some more, but I don't know.

The right way would be a combiner, battery bank (I'd go with lead acid or maybe LFP), and inverters that are capable of running grid tie or stand alone. Take a look at enphase's website.
 
Some of our friends in San Antonio have solar panels and they weren't able to use them because the SA power company won't allow battery backup to solar installations. So when the grid goes down al of those with solar are down too. This is the situation you are trying to get around and I understand why. But, are you subject to inspectors of your system? I don't know how the power company keeps someone (in your area) from building a battery backup on their own but none of my electricians that have those systems have been able to get around it in San Antonio.
 
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