Grid-tied solar

[dmccarty]

Now, am I correct in thinking that the micro-inverters work by sensing power through their connection to the house and syncing to that. As such, if they dont detect power, they dont put out power?

Correct. Just like a single inverter, this is done to prevent back feeding the grid.

As such, could they be connected to a subpanel (say the 100 amp panel in the barn) and provide power back to the house?
Also, would they work if (for example) I were to have the line going to them as one of the circuits powered by a backup generator?

Thanks

Aaron Z

Those last two questions the wifey were discussing today but I don't know the answer.

Are you trying to figure out how to get the panels to provide power when the grid is down and the PV system is without batteries? I know I am. :laughing::laughing::laughing:

We are talking about the possibility of having enough battery backup to power the fridge, freezer, study and well pump. Those are our major concerns in a power outage and we could run the generator to recharge the batteries if the PV panels were not keeping up for some reason.

One of the nice things about the microinverters is being able to add a few PV panels at a time when you have money which is problematic with a single inverter.

Later,
Dan

 

[aczlan]

Those last two questions the wifey were discussing today but I don't know the answer.
Are you trying to figure out how to get the panels to provide power when the grid is down and the PV system is without batteries? I know I am. :laughing::laughing::laughing:

I am wondering if the power from a small inverter generator or the large UPS would be enough to fool the PV panels into thinking that power was on and let me have (for example) 5kw of solar to add to the 1600w genset. Would be a whole lot cheaper than fuel for a larger genset.
Another possibility would be to pickup a small diesel genset (was a 3KW one on Craigslist a few months back for $300 that would have been perfect)

Aaron Z

 

[Redneck in training]

Grid commutated inverters will not work with a generator or battery powered inverter. Reason being that they will try to push all available generated power to the grid. To do so they will increase voltage. If the "grid" is made by small generator and the demand is less than the PV generation they will increase voltage to about (262 V) and shutdown. I am not sure at this point how the shutdown is reset but I can speculate that you would have to turn the power completely off or they reset at night. They have also low voltage and high/low frequency shut off.
In other words they would work only if the battery or another type of storage (in example electric hot water tank) would be able to absorb all generated power.

 

[aczlan]

Thanks.

Aaron Z

 

[dmccarty]

Grid commutated inverters will not work with a generator or battery powered inverter. Reason being that they will try to push all available generated power to the grid. To do so they will increase voltage. If the "grid" is made by small generator and the demand is less than the PV generation they will increase voltage to about (262 V) and shutdown.....

In other words they would work only if the battery or another type of storage (in example electric hot water tank) would be able to absorb all generated power.

I was looking at batteries to provide some backup but them danged things really add to the cost and complexity of a system. It seems that trying to use batteries puts you back to using a large inverter to converted from the battery DC to AC.

Later,
Dan

 

[Redneck in training]

You can store energy as in example hot water in the winter or chilled water in the summer. The complicated part is the controller that would control the load (storage ) such a way that you would store only enough energy not to have an excess. That is what I am thinking about. I could install large no pressure tank in the garage and use excess generated energy to heat it in the winter and chill it in the summer. That could be interesting retirement project.

 

[aczlan]

That could be an option if we go with a water mass storage tank, just put in bungs to install several hot water heater heating elements and figure how to tell the system that if the voltage gets above (say) 124 volts per leg, turn on the heating elements. That could then be used to heat the mass storage tank and provide domestic hot water...

Aaron Z

 

[aczlan]

Perhaps something like Single Phase Monitor | Phase Monitor | ICM Controls could control a relay to either charge a battery bank or heat water when the line voltage is over a certain voltage.

Aaron Z

 

[Redneck in training]

power usage monitor that communicate with an electric meter - Google Search

Connected Home Manager, Energy Monitor | GE Nucleus

http://www.ekmmetering.com/?gclid=CIqk7Mmd9bUCFU566wodLk0A9Q

Google smart meter

 

[dave1949]

You don't want to over-think setting up a grid-tied solar system to be tricked into functioning when the grid power is out. It won't do anything during the night time hours which is 50% of the time on a yearly average, and if your power is out because it is stormy, you may not have that much sun to work with anyways.

If you must have power overnight, then you will need a generator in any case. Or, install an off-grid system with enough battery capacity. That will cost more than a generator, needs a dedicated battery area that doesn't get too hot or cold, and requires some maintenance. The hybrid grid-tied/off-grid systems with some minimal battery capacity are also expensive.

There is a KISS element to it.