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  #1  
Old 06-10-2021, 06:40 PM
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Solar panel question

I am looking into getting panels and a generator for power and back up. I was told something interesting by two f the sales reps and neither had the technical expertise to explain the reasoning for what they said and both agreed that it should be able to be done.

If you have solar panels and the power goes out, even though your solar system has the ability to power your house, it wont. The power your panels generate goes to the grid and the grid will power the house. If I were to get a system like the Tesla Wall, the same applies. Once the batteries exhaust themselves, the solar panels will not charge the batteries. Now, if I add a generator into the mix, the generator will charge the batteries.

The only thing that kind of makes sense is that the generator is AC and the solar panels are DC but, there is an inverter so that seems to indicate that this is possible. Besides, If I live off the grid, I can get solar panels, an inverter and power my house. So whats the deal? Is the power company some how getting their hands in the mix to prevent people from having an efficient system and cutting them out?

Any ideas?

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  #2  
Old 06-10-2021, 07:00 PM
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The power companies will pay you pennies to use the excess energy you make and charge the going rate for it downstream. I would install a hybrid system. Panel power for heavy use items like HVAC and the rest on solar.

A 5k smart inverter system with a power wall would be more than enough to carry you through any two to three day outages. More if sunny out.

The difference with solar is you have to keep an eye on all power consumption. You would be amazed at how much power those phone chargers and small transformers consume.
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  #3  
Old 06-10-2021, 09:12 PM
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Quote:
Originally Posted by Dubyagee View Post
The power companies will pay you pennies to use the excess energy you make and charge the going rate for it downstream. I would install a hybrid system. Panel power for heavy use items like HVAC and the rest on solar.

A 5k smart inverter system with a power wall would be more than enough to carry you through any two to three day outages. More if sunny out.

The difference with solar is you have to keep an eye on all power consumption. You would be amazed at how much power those phone chargers and small transformers consume.
Actually, Reliant and one other company will do 1:1 net metering. So any excess I produce on sunny days is put in a 'bank' and I use it 1:1 when I need to draw power.

According to Tesla, I would have to have 4 power walls to power my house for 5 days without power. Given how much power the 3T and 1.5T ac systems use, I do not see how they could last that long. My issue with the power walls is longevity. They are only guaranteed for 10 yrs which means they will likely fail shortly there after. Current price on a power wall is somewhere around $7k last I checked. If, worst case scenario, I have to replace 4 walls, that $28k out of pocket. Considering I have only lost power a handful of times over the last 20 yrs, spending that kind of money for backup power is not worth it for me.

They hybrid I am looking at is solar panels for day to day use and a 18kWh backup Generac for power failures. The only necessities are the AC, pool pump and fridge. The generator can handle that plus a few ancillary lights, ceiling fans and so forth.

They system I am considering guarantees 21 kWh a year. If I fail to produce that, the company will cut me a check for any shortage. Last year, I used a bit over 22 kWh for the year. So if that hold steady, my electric bill will be nearly zero and after the system is paid off, I will be saving about $2500 a yr in electric costs. More if/when utility prices go up.

I just do not understand why during a power failure, the power generated by the panels cannot power the house through the same switch the generator would. That does not make any sense to me.
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- With out god, life is everything.
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  #4  
Old 06-10-2021, 09:16 PM
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Grid tied system will NOT power the house if the grid goes down. It is because the inverter doesn't see the grid and it will not invert the solar power.

You need a hybrid inverter if you want power during blackout. It works on solar, battery in that order. If the battery is out then it will use the grid or generator to recharge. It is kind of a reverse UPS.
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  #5  
Old 06-10-2021, 09:26 PM
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Quote:
Originally Posted by ah-kay View Post
Grid tied system will NOT power the house if the grid goes down. It is because the inverter doesn't see the grid and it will not invert the solar power.

You need a hybrid inverter if you want power during blackout. It works on solar, battery in that order. If the battery is out then it will use the grid or generator to recharge. It is kind of a reverse UPS.
Why do they not use a hybrid? Both salespeople said that their systems do not charge when power is down and every article I have read since says the same thing.

Is there some cost or legal impediment?
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2014 C250 21,XXX my new DD ** 2013 GLK 350 18,000 Wife's new DD**

- With out god, life is everything.
- God is an ever receding pocket of scientific ignorance that's getting smaller and smaller as time moves on..." Neil DeGrasse Tyson
- You can pray for me, I'll think for you.
- When you understand why you dismiss all the other possible gods, you will understand why I dismiss yours.
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  #6  
Old 06-10-2021, 10:40 PM
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Quote:
Originally Posted by davidmash View Post
Why do they not use a hybrid? Both salespeople said that their systems do not charge when power is down and every article I have read since says the same thing.

Is there some cost or legal impediment?
Grid tied system is always like that. They don't want to electrocute the technicians fixing the blackout. Solar panels never invert during blackout and put voltage on the wires. It is a design feature.

Bottom line is it will be very expensive to make a grid tied system to retrofit with battery.
__________________
Not MBZ nor A/C trained professional but a die-hard DIY and green engineer. Use the info at your own peril. Picked up 2 Infractions because of disagreements. NOW reversed.

W124 Keyless remote, PM for details. http://www.peachparts.com/shopforum/mercedes-used-parts-sale-wanted/334620-fs-w124-chasis-keyless-remote-%2450-shipped.html

1 X 2006 CDI
1 x 87 300SDL
1 x 87 300D
1 x 87 300TDT wagon
1 x 83 300D
1 x 84 190D ( 5 sp ) - All R134 converted + keyless entry.
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  #7  
Old 06-10-2021, 10:57 PM
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Solar panel question

https://unboundsolar.com/2550157/outback-power/inverters/outback-power-gs8048a-01-inverter

This ties into the grid and solar. It draws from and and charges the batteries. Its stackable and is grid tied. You can set priorities depending on what you want. For example, pull from grid first and batteries second or reverse. You can charge the batteries anyway you want to and let this charge them from the grid as a last choice. It will not back feed a dead grid.

Install PDF

https://documents.unboundsolar.com/media/2550157_gsa_w_v_1616428321.pdf


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  #8  
Old 06-10-2021, 11:07 PM
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Keep your system off the grid. Flip the main fuse and engage your system for, as you say: for power and back up"
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  #9  
Old 06-11-2021, 12:07 AM
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Quote:
Originally Posted by ah-kay View Post
Grid tied system is always like that. They don't want to electrocute the technicians fixing the blackout. Solar panels never invert during blackout and put voltage on the wires. It is a design feature.

Bottom line is it will be very expensive to make a grid tied system to retrofit with battery.
Perhaps I am not being clear. I can set up a whole home generator that when the power goes out, it will kick on, power my home and not put current into the grid. Why cant a solar panel use the same switch that a generator does?
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- With out god, life is everything.
- God is an ever receding pocket of scientific ignorance that's getting smaller and smaller as time moves on..." Neil DeGrasse Tyson
- You can pray for me, I'll think for you.
- When you understand why you dismiss all the other possible gods, you will understand why I dismiss yours.
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  #10  
Old 06-11-2021, 12:11 AM
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Quote:
Originally Posted by davidmash View Post
Why do they not use a hybrid? Both salespeople said that their systems do not charge when power is down and every article I have read since says the same thing.

Is there some cost or legal impediment?
I believe the issue is phase matching. The inverter output has to be perfectly in phase with the power line current, otherwise it's just injecting noise when it feeds power to the grid. So it senses grid phase and creates a matching waveform from battery power. No grid, no sine wave.

When the generator is on, a transfer switch has to be present, and that will disconnect the system from the grid. The system shouldn't be feeding power back to the generator, so the control system has to know which power source it's on and behave accordingly. And when switching back from generator to grid, it first needs to adjust the phasing. So a lot more sophistication and expense would be required.

20kwhr/yr seems way too low. I can use that in a month, without A/C.
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  #11  
Old 06-11-2021, 12:19 AM
davidmash's Avatar
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Quote:
Originally Posted by Dubyagee View Post
https://unboundsolar.com/2550157/outback-power/inverters/outback-power-gs8048a-01-inverter

This ties into the grid and solar. It draws from and and charges the batteries. Its stackable and is grid tied. You can set priorities depending on what you want. For example, pull from grid first and batteries second or reverse. You can charge the batteries anyway you want to and let this charge them from the grid as a last choice. It will not back feed a dead grid.

Install PDF

https://documents.unboundsolar.com/media/2550157_gsa_w_v_1616428321.pdf
From what I can tell, this does not change the fact that the solar panels will not supply power to either batteries or the home when the grid if off line.
__________________
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2014 C250 21,XXX my new DD ** 2013 GLK 350 18,000 Wife's new DD**

- With out god, life is everything.
- God is an ever receding pocket of scientific ignorance that's getting smaller and smaller as time moves on..." Neil DeGrasse Tyson
- You can pray for me, I'll think for you.
- When you understand why you dismiss all the other possible gods, you will understand why I dismiss yours.
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  #12  
Old 06-11-2021, 12:19 AM
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Quote:
Originally Posted by INSIDIOUS View Post
Keep your system off the grid. Flip the main fuse and engage your system for, as you say: for power and back up"
There is no fuse to flip.
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2014 C250 21,XXX my new DD ** 2013 GLK 350 18,000 Wife's new DD**

- With out god, life is everything.
- God is an ever receding pocket of scientific ignorance that's getting smaller and smaller as time moves on..." Neil DeGrasse Tyson
- You can pray for me, I'll think for you.
- When you understand why you dismiss all the other possible gods, you will understand why I dismiss yours.
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  #13  
Old 06-11-2021, 12:23 AM
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Quote:
Originally Posted by Mxfrank View Post
I believe the issue is phase matching. The inverter output has to be perfectly in phase with the power line current, otherwise it's just injecting noise when it feeds power to the grid. So it senses grid phase and creates a matching waveform from battery power. No grid, no sine wave.

When the generator is on, a transfer switch has to be present, and that will disconnect the system from the grid. The system shouldn't be feeding power back to the generator, so the control system has to know which power source it's on and behave accordingly. And when switching back from generator to grid, it first needs to adjust the phasing. So a lot more sophistication and expense would be required.

20kwhr/yr seems way too low. I can use that in a month, without A/C.
A kWh is not the same as a kWhr. I went through each bill and I used 22k kWh in the year. My current rate is about $.09kWh.

Are you saying that the panels produce a power that the Home cannot use but the generator does?
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2014 C250 21,XXX my new DD ** 2013 GLK 350 18,000 Wife's new DD**

- With out god, life is everything.
- God is an ever receding pocket of scientific ignorance that's getting smaller and smaller as time moves on..." Neil DeGrasse Tyson
- You can pray for me, I'll think for you.
- When you understand why you dismiss all the other possible gods, you will understand why I dismiss yours.
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  #14  
Old 06-11-2021, 01:58 AM
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No grid, no power. It is to sync the incoming AC phase for grid tied system otherwise you can't feed power back to the grid. Grid tied solar with battery backup is more expensive and payback period is long.

Whatever you do, DON'T lease a system.
__________________
Not MBZ nor A/C trained professional but a die-hard DIY and green engineer. Use the info at your own peril. Picked up 2 Infractions because of disagreements. NOW reversed.

W124 Keyless remote, PM for details. http://www.peachparts.com/shopforum/mercedes-used-parts-sale-wanted/334620-fs-w124-chasis-keyless-remote-%2450-shipped.html

1 X 2006 CDI
1 x 87 300SDL
1 x 87 300D
1 x 87 300TDT wagon
1 x 83 300D
1 x 84 190D ( 5 sp ) - All R134 converted + keyless entry.
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  #15  
Old 06-11-2021, 09:54 AM
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Quote:
Originally Posted by ah-kay View Post
No grid, no power. It is to sync the incoming AC phase for grid tied system otherwise you can't feed power back to the grid. Grid tied solar with battery backup is more expensive and payback period is long.

Whatever you do, DON'T lease a system.
Definitely not going to lease.

Perhaps I am missing something but if a house that is not even tied to the main grid can have a solar system powering their home, why cant a house that is tied to the grid work the same way but have a switch that cuts off power to the grid when main power fails. They do it for a generator, why not for solar?

This sounds more like a legal issue than a technical one.

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- With out god, life is everything.
- God is an ever receding pocket of scientific ignorance that's getting smaller and smaller as time moves on..." Neil DeGrasse Tyson
- You can pray for me, I'll think for you.
- When you understand why you dismiss all the other possible gods, you will understand why I dismiss yours.
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