Rigging grid tied system for power when grid goes down

[ed6269]

Hello everyone
I know it is not recommended but hear me out.
My system is a 11 year old grid tied set up that does not have any rapid shutdown capabilities so I was thinking that if I added a blue sea A B switch before the solar panel disconnect to divert the solar panel output to a separate all in one off grid unit (say something like the growatt SPF 300TL LVMES that Will recently reviewed) I could safely get power out of my panels when the grid goes down.
Unfortunately my panels put out too much voltage (260 volts) so that growatt would not work for me. If anyone has a suggestion for a off grid all in one unit that could do 300 volts or more I would like to hear about it.
I would like to hear any thoughts or warnings on this ,what do you think?

 

[snoobler]

 

[Ampster]

That is a good video. I use an Outback Skybox to AC couple 5.7kW of solar on a Solaredge GT inverter and 1kW of Enphase micros.
What the OP is considering is DC coupling which is much simpler if he can match his string voltage to an inverter.

 

[ed6269]

That is a good video. I use an Outback Skybox to AC couple 5.7kW of solar on a Solaredge GT inverter and 1kW of Enphase micros.
What the OP is considering is DC coupling which is much simpler if he can match his string voltage to an inverter.

So you think this would work ok , any suggestions for a all in one type that would have a 300 volt DC input? I like that batteryless growatt that Will reviewed but my aray is putting out like 252 volts just slightly higher than the 250 volts that the growatt can take so I am looking for something in the 300 volt range.

 

[svetz]

The Sol-Ark has a 150-425V MPPT range, but you might as well throw your old GT setup away.

If you can't find a suitable all-in-one, you might look for a suitable SCC and inverter.

 

[Ampster]

I only know much about the Skybox and SolArk. They are $3500 and $6000 respectively. If you are going to replace a grid tied inverter the replacement probably needs to be UL approved. I think you are on the right track with looking for an All in One. Is there any way you can rearrange your panels to make the Growatt work or other options like @svetz suggested?

 

[ed6269]

I only know much about the Skybox and SolArk. They are $3500 and $6000 respectively. If you are going to replace a grid tied inverter the replacement probably needs to be UL approved. I think you are on the right track with looking for an All in One. Is there any way you can rearrange your panels to make the Growatt work or other options like @svetz suggested?

I thought about removing some panels to drop the voltage down, I am so close now , but I don't really know how much below the 250 max I should be. My grid tied until has a max DC input is 300 volts.
If I just need to be a shade under the 250 I think just dropping 1 panel might do it but any more than that and I would hate to do it.
That growatt unit is only 750.00 and doesn't require batteries to work so that seems like a pretty cheap option though I would still put some sort of cheap battery setup to stabilize the power.

 

[Ampster]

but I don't really know how much below the 250 max I should be.

You need to refer to your panel specs. The situation to design to, is a cold clear day where the panel voltage goes high. The concept I was suggesting was splitting the string in half and parallel the half strings. That would be half the voltage but twice the Amps. Look at the specs for the Growatt to see what the minimum voltage is. Does it have two MPPT channels? Does it need batteries to work?

 

[ed6269]

You need to refer to your panel specs. The situation to design to is a cold clear day where the panel voltage goes high. The concept I was considering was splitting the string in half and parallel them. That would be half the voltage but twice the Amps. Look at the specs for the Growatt to see what the minimum voltage is. Does it have two MPPT channels? Does it need batteries to work?

Thats a good idea, thanks I am going to look at doing it that way

 

[svetz]

If you're not familiar with the math, there's some examples here: Figuring out how many panels in series and parallel based on your MPPT

 

[ed6269]

I just wish there was a device that you could hook up to a large array and set the voltage to what ever you want, just set it and forget it.
That would be so cool.

 

[svetz]

I just wish there was a device that you could hook up to a large array and set the voltage to what ever you want, just set it and forget it.
That would be so cool.

There is, they're microinverters. They convert the DC to AC at the panel, so no worry about strings, voltages, temperatures. One per panel and you can easily scale over time.

 

[ed6269]

There is, they're microinverters. They convert the DC to AC at the panel, so no worry about strings, voltages, temperatures. One per panel and you can easily scale over time.

Yes ,but they shut down when the grid goes down

 

[svetz]

Yes ,but they shut down when the grid goes down

Unless you're AC coupled, have a Powerwall, or something like Enphase's Ensemble.

 

[ed6269]

But I would like to be able to us my grid tied system when power is out without spending thousands of dollars to set it up. By using the Growatt all in one batteryless system I would be able to do that for 750.00 but I need to knock the voltage down to 250 . Not really looking to buy a hole new system.

 

[Ampster]

By using the Growatt all in one batteryless system I would be able to do that for 750.00 but I need to knock the voltage down to 250

Did you ever look up the voltage range to see if splitting your existing array into two strings would work? Have you confirmed that it would work without batteries when the grid is down?

 

[ed6269]

Yes I did check and if I split the array up it would drop the voltage to low for the grid tied system to work.
And watching Wills video on the Growatt battery less system it seems like it would work for small loads, it would not start the air-conditioning unit without a small battery system though.

 

[ed6269]

Did you ever look up the voltage range to see if splitting your existing array into two strings would work? Have you confirmed that it would work without batteries when the grid is down?

Oops I replied without pressing reply. Check the response above

 

[Ampster]

if I split the array up it would drop the voltage to low for the grid tied system to work.

Why do you need two inverters? Couldn't the Growatt be your grid tie and your back up inverter. That would be much simpler.

 

[ed6269]

Why do you need two inverters? Couldn't the Growatt be your grid tie and your back up inverter. That would be much simpler.

I don't think that Growatt is a grid tied unit . Will did not say it was in his video. Did you watch that video? He set it up in his solar trailer.