Is it OK to leave solar panels in sunlight not connected to anything?

[Paulj]

I am getting ready to install 400W of solar on the roof of my van, but it will be some time before I am ready to hook them up to an MPPT controller and batteries. Is there any harm in leaving the solar panels disconnected for a time?
Thanks

 

[fratermus]

They'll be fine. When the time comes remember to connect the controller to the battery bank before hooking up the panels.

 

[Substrate]

If those panels are thin-film amorphous types, rather than mono/polycrystalline, it is generally better not to expose them to sun and not be serving any purpose, since thin-film degrades quicker with exposure.

A few weeks, months of exposure with a thin-film panel not serving any purpose is one thing, but if they are going to be installed for a year with no use, why not save a years worth of degradation.

 

[Mac-7]

I was speaking to a couple of guys from an Austin Texas solar company

and they tried to tell me that the power had to be used or the solar panel would catch on fire from all the pent up energy

I’m just learning about solar but even I knew that was wrong

 

[Diysolar123]

I was speaking to a couple of guys from an Austin Texas solar company

and they tried to tell me that the power had to be used or the solar panel would catch on fire from all the pent up energy

I’m just learning about solar but even I knew that was wrong

those are the same guys that tell you to pay to put nitrogen in your tires....
Did they sell you a "solar panel energy draining device" to avoid explosions when not in use?

 

[Mac-7]

those are the same guys that tell you to pay to put nitrogen in your tires....
Did they sell you a "solar panel energy draining device" to avoid explosions when not in use?

No. Our conversation did not go that far

I walked away pretty fast

But every solar salesman I talk to swears that I must have a “smart” inverter/controller that kills my solar output to my home when the grid goes down

I’m sure that is wrong

But so far no solar company has been willing to configure an installation that gives me what I want

 

[pollenface]

Grid tie inverters will not produce power if there is no grid power available for it to synchronize with.

 

[wattmatters]

But every solar salesman I talk to swears that I must have a “smart” inverter/controller that kills my solar output to my home when the grid goes down

I’m sure that is wrong

Can't say what the regulations are where you are but here in Australia it is a legal requirement that if the grid goes down a grid tied solar PV system must immediately either:
- switch off, or
- become completed isolated from the grid

This is to ensure no voltage is presented to power lines for the safety of line workers.

Most grid tied inverters will immediately turn off when grid power is disconnected.

 

[Mac-7]

Can't say what the regulations are where you are but here in Australia it is a legal requirement that if the grid goes down a grid tied solar PV system must immediately either:
- switch off, or
- become completed isolated from the grid

This is to ensure no voltage is presented to power lines for the safety of line workers.

Most grid tied inverters will immediately turn off when grid power is disconnected.

thats sensible because we have to protect the workers who are trying to fix the problem

But the solar panels can and should be isolated from the grid and continue operating

I’m sure that it can be done

 

[WalterM]

If the grid goes down do they think that your solar system would be feeding the entire grid? I would think it would for your protection to disconnect so you don't damage your equipment.

 

[Trabuco]

If the grid goes down do they think that your solar system would be feeding the entire grid? I would think it would for your protection to disconnect so you don't damage your equipment.

Portable Generator Safety: Our Lives Are At Stake! | PC Electric

www.pcemc.org

“Portable generators, widely used when power lines are down, can prove fatal to line workers and your neighbors when used improperly. Of course, no one would ever purposely cause the death of a line worker. Nevertheless, a generator connected to a home’s wiring or plugged into a regular household outlet can cause back feeding along power lines and electrocute anyone who comes in contact with them—even if the line appears to be dead.”

 

[Mac-7]

Portable Generator Safety: Our Lives Are At Stake! | PC Electric

www.pcemc.org

“Portable generators, widely used when power lines are down, can prove fatal to line workers and your neighbors when used improperly. Of course, no one would ever purposely cause the death of a line worker. Nevertheless, a generator connected to a home’s wiring or plugged into a regular household outlet can cause back feeding along power lines and electrocute anyone who comes in contact with them—even if the line appears to be dead.”

I am not trying to do that

but its not difficult to disconnect the house from the grid during power outages and still get the output of the solar panels

 

[Shotgun]

I bought one of the all-in-one systems that does not back feed to the grid. Duke Power isn't going to give me anything for what I generate anyhow. I dropped in a panel below it, and ran several of my house circuits to it. Those circuits were driven by the grid over the past few rainy days, but are being driven by clear sunshine today. However, with no feed back into the grid, I don't have to worry about killing anyone, and didn't have to worry about the phalanx of inspectors that are trying to keep me from being partially energy independent with my 1.5kW of panels.

 

[Mac-7]

I bought one of the all-in-one systems that does not back feed to the grid. Duke Power isn't going to give me anything for what I generate anyhow. I dropped in a panel below it, and ran several of my house circuits to it. Those circuits were driven by the grid over the past few rainy days, but are being driven by clear sunshine today. However, with no feed back into the grid, I don't have to worry about killing anyone, and didn't have to worry about the phalanx of inspectors that are trying to keep me from being partially energy independent with my 1.5kW of panels.

that is just what I want to do

But so far I can't find any company that is willing to sell me a system like that

 

[wattmatters]

If the grid goes down do they think that your solar system would be feeding the entire grid? I would think it would for your protection to disconnect so you don't damage your equipment.

The phrase "grid goes down" means many things.

From a home inverter's point of view, whether it's because there's been a massive grid scale power station outage, or the high voltage transmissions lines 500 miles away have been damaged, or it's because a tree fell on one of your local poles and wires, your grid tied inverter doesn't know the difference. All it knows is the power is off.

So while it's unlikely your grid tied inverter would produce enough voltage to cause safety problems beyond your local substation, it most definitely can kill someone working locally. And outages are most commonly due to local grid transmission issues rather than failures with the big stuff (although that can happen too).

But the solar panels can and should be isolated from the grid and continue operating

I’m sure that it can be done

It can. As I said the system needs to be either be switched off or automatically isolated from the grid. To do the latter you will need a local automated grid isolating switching system and a battery, similar to how the Tesla Gateway and Powerwall operates during grid outages.

You need the battery because you are in effect creating your own micro grid and need to balance energy supply and demand at every moment, something very tricky to achieve with solar PV systems alone. Some newer grid tied inverter systems can manage a bit of backup without battery, e.g. the New Gen 24 Fronius inverters, but the functionality is rather more limited than systems integrated with a battery. An inverter can reduce the output from solar PV panels but it can't get more out of them than they are delivering should the home's backup circuits require more energy than is available (e.g. a cloud passes overhead and suddenly the available power drops below what the home is currently demanding).

 

[Mac-7]

The phrase "grid goes down" means many things.

From a home inverter's point of view, whether it's because there's been a massive grid scale power station outage, or the high voltage transmissions lines 500 miles away have been damaged, or it's because a tree fell on one of your local poles and wires, your grid tied inverter doesn't know the difference. All it knows is the power is off.

So while it's unlikely your grid tied inverter would produce enough voltage to cause safety problems beyond your local substation, it most definitely can kill someone working locally. And outages are most commonly due to local grid transmission issues rather than failures with the big stuff (although that can happen too).


It can. As I said the system needs to be either be switched off or automatically isolated from the grid. To do the latter you will need a local automated grid isolating switching system and a battery, similar to how the Tesla Gateway and Powerwall operates during grid outages.

You need the battery because you are in effect creating your own micro grid and need to balance energy supply and demand at every moment, something very tricky to achieve with solar PV systems alone. Some newer grid tied inverter systems can manage a bit of backup without battery, e.g. the New Gen 24 Fronius inverters, but the functionality is rather more limited than systems integrated with a battery. An inverter can reduce the output from solar PV panels but it can't get more out of them than they are delivering should the home's backup circuits require more energy than is available (e.g. a cloud passes overhead and suddenly the available power drops below what the home is currently demanding).

I think I am with you so far

I need battery backup such as the Tesla Powerwall or similar

And I need the proper switch between the power coming in from the grid and the solar panels on the house

One reason I know its possible is because Generac does it with their generator backup systems

During a power outage the generator kicks in and causes no danger to power line workers

But explaining that to a solar system salesman who paints by the numbers has been impossible up to now

 

[Shotgun]

that is just what I want to do

But so far I can't find any company that is willing to sell me a system like that

No one is going to sell you a system like this. Not enough profit in it. This is 100% DIY.

Used panels and batteries from one place. Controller from another. Other bits and pieces from the big box hardware stores.

Don't get your controller from PowMr. Just don't <sigh>.

 

[Mac-7]

No one is going to sell you a system like this. Not enough profit in it. This is 100% DIY.

Used panels and batteries from one place. Controller from another. Other bits and pieces from the big box hardware stores.

Don't get your controller from PowMr. Just don't <sigh>.

tell me more about the used panels and batteries

How good are they and where are they sold?

 

[Gone]

You can't go wrong with SanTan Solar.

I bought 42 used 250W panels for about $30 each plus shipping.
They test at full spec, and I'm pleased as punch.

I have an off-grid setup; they can't be used for grid-tie.

 

[EricBarbour]

I was speaking to a couple of guys from an Austin Texas solar company
and they tried to tell me that the power had to be used or the solar panel would catch on fire from all the pent up energy
I’m just learning about solar but even I knew that was wrong

My experiences have been similar. Very few "professionals" are really all that knowledgable, and none of them wants to anger the electric utility companies. So they feed people who want off-grid capability all kinds of crap "advice" and outright misinformation. Not one of the licensed electricians in my county knows piss-all about solar power. One of them tried to sell me a 200-amp utility upgrade, when I was telling him I wanted to use LESS utility power.

And the solar contractors are usually greedy, lying, incompetent, and/or totally insane. It is a "new" and poorly regulated industry. Google "DC Solar" if you don't believe me. It was one of the largest solar contractors in the San Francisco bay area....until the FBI came after the owners. THAT is the "home solar industry" for you.

DC Solar - Wikipedia

en.wikipedia.org

Seriously, you should look into DIYing an off-grid system with battery, just to run the critical systems in the house. If you don't know how to deal with high-power electronics, hire a local technician or engineering student to help. Or buy one of those prebuilt solar trailers and park it in the backyard. You can get an electrician to install a transfer switch and generator input on the house, and then connect your solar inverter to it. Watch and manage the system and it should work well enough for you.

I doubt any of those contractors will help you build the solar part. Luckily it isn't too difficult--you just have to be smart and careful.