Question about integrating solar panels with genset

[greglepore]

I had a 9kv solar system installed recently. I have a preexisting 30kw water cooled generator with an auto switch. If it maters, the inverter is Smart Edge.

My concern is that the solar is tied into the mains at the gen switch on by taps into the utility side. What happens if utility goes out, but panels are producing? Do i have a brownout if load exceeds solar output as the switch still sees power? Or am I missing something?

Couldn't get a straight answer from the solar installers, just that "its ok'".

[pete3799]

Paging Red Beard.

[billybek]

Pretty sure that if your power goes out and you solar will not power the house unless you are harvesting and storing in batteries.
Generator will start on occasion to charge batteries to capacity when power from the grid is not available.
System is disconnected from the grid by a transfer switch so that your system is not putting power down the wires. That would be a little dangerous for the linemen working to restore power.
Red Beard will give you the definitive answer though....

[greglepore]

yeah, waiting for Redbeard. My issue is the taps appear to be on the utility side of the the transfer switch and that the panels, if daytime and sunny, could put out enough power to keep the genset off but not sufficient power for the house load, thus browning out the house and damaging stuff. I don't have batteries, haven't found a cost effective solution.

I'm hoping that the inverter somehow needs to see a/c from the utility to operate, but I can't confirm that.

[jrj3rd]

Originally Posted by greglepore

I'm hoping that the inverter somehow needs to see a/c from the utility to operate, but I can't confirm that.

That is the way it should be designed. I my house the inverter needs to see grid power to allow panel power to flow. When power goes off inverters stop letting anything through. Generator comes on and panels start flowing again.

[red-beard]

Originally Posted by greglepore

I had a 9kv solar system installed recently. I have a preexisting 30kw water cooled generator with an auto switch. If it maters, the inverter is Smart Edge.

My concern is that the solar is tied into the mains at the gen switch on by taps into the utility side. What happens if utility goes out, but panels are producing? Do i have a brownout if load exceeds solar output as the switch still sees power? Or am I missing something?

Couldn't get a straight answer from the solar installers, just that "its ok'".

The Solar MUST be connected to the utility side of the transfer switch. When the utility power goes out, the solar will stop producing, per UL-1741

The issue is that the solar panels could backfeed the generator if they are on the house side of the transfer-switch. In other words, you are using 2kW and they produce 5, where does that power go? The grid tied inverters are not designed to modulate their output.

The systems we build are setup with AC or DC coupling.

With DC coupling, you are connecting the solar panels to the battery side of the inverter system. If the batteries go full and the utility power is up, they will sell power to the grid. If the batteries go full and the utility is NOT connected, the charge controllers will modulate the solar output down to your usage.

With AC coupling, we use a relay to connect the solar panels. When the utility is off-line, if the batteries go full we disconnect the solar panels. If the generator is running, we also disconnect the solar panels.

[red-beard]

Originally Posted by greglepore

yeah, waiting for Redbeard. My issue is the taps appear to be on the utility side of the the transfer switch and that the panels, if daytime and sunny, could put out enough power to keep the genset off but not sufficient power for the house load, thus browning out the house and damaging stuff. I don't have batteries, haven't found a cost effective solution.

I'm hoping that the inverter somehow needs to see a/c from the utility to operate, but I can't confirm that.

Unless it is a battery based system, you cannot use the grid-tied solar equipment to power the house. This should have been explained to you before you purchased the system. Grid tied systems are designed to save money, not keep the lights on.

UL-1741 mandates that a grid tied system shutdown if the utility goes out. Your solar installer installed it correctly.

[jrj3rd]

^^^ this makes sense

Guess I need to go re-look at how they installed my system

[red-beard]

Originally Posted by jrj3rd

Guess I need to go re-look at how they installed my system

No one will install an inverter in the US that is not UL-1741. No extra equipment is needed to make it compliant. The Grid-tied inverter will automatically shutdown to prevent backfeeding the utility.

[jrj3rd]

more concerned about how it is tied into the system relative to the transfer switch. I thought it was on the breaker side, not the utility side

[red-beard]

Originally Posted by jrj3rd

more concerned about how it is tied into the system relative to the transfer switch. I thought it was on the breaker side, not the utility side

It must be on the Utility input side. You cannot have the solar operating with the generator.

[greglepore]

Ok. That's all I wanted to know. I'm fine with it not keeping the lights on, that's why I have the genset. Was more worried about brownout, but you've explained that.