3 phase solar system with battery back up

ligwyd

Hi there,

Have a property that is supplied with 208Y/ 120V power.

Goal is to build a solar system for the customer that can sell back to the grid when solar production exceeds local loads and is backed up with battery to run only critical loads if grid goes down.

Just beginning the search for the appropriate equip......

Appreciate any discussion that might get the ball rolling.

BB.

Depending on the size/rating of the system, and what the expectations are (need battery back failover or could the customer live with a diesel Genset and, up to, 5 minute genset startup--As an example).

For a larger system, need to get a power engineer with lots of experience involved--Here is a thread where getting the right engineer was able to address (most/all) of the ongoing problems of large 3 phase off grid Genset/inverter system:

https://forum.solar-electric.com/discussion/17986/is-the-system-set-up-right/p1

-Bill

ligwyd

Thanks Bill. On a side note, have you ever heard of installing a 240 split phase hybrid inverter with a 3 phase 208Y/ 120V grid power supply present?

Alternatively I guess Fronius (Symo) or Solar Edge has smaller 3 phase inverters (15K ish).......

Appreciate the dialogue.....

BB.

In general, you have to use 2-3 "boost" transformers to change from 208 to 240 VAC... Transformers have their own losses (upwards of 5%, and losses even with zero Wattage loading).

In our region (California), as far as I know, smaller 3 phase installations are Wye Connected 120/208 power (smaller office parks and such). Larger installations can/are 120/240 VAC (typically Delta?).

If you try using 208 to 240 VAC single phase on a 3 phase utility connection, there is a requirement that the phases be no more than 10 kWatts of unbalanced loading... Presumably, that would also apply to Grid Tied system too (that is just an old memory based on our local utility requirements--Yours in Western Canada(?) may be different).

So, if you need 240 VAC and want to connect a "smaller" solar GT Inverter single phase--You may be able to get the utility to accept this.

Also, for 3 phase power systems, I believe that anything that feeds power back into the utility network needs to shut down if there is a "lost phase"... So even a single phase inverter may need a a phase fault detector/shutdown "device".

If you are native 120/208 3 phase power, for GT Inverters, getting a compatible 3 phase inverter(s) setup for over 10 kWatt of solar (my guess).

If this is more of a 120/240 VAC single phase backup system--A smaller system may be possible/practicable... I would wonder if solar is "useful" for a full GT/Battery backup system vs a diesel backup genset for "relatively rare" power failures (in California, backup gensets are getting to be pretty difficult to get permits for (pollution, CO2, going "green electric" rules, etc.).

For Kelowna BC Canada, fixed array facing south, 50 degree tilt (from horizontal):

https://pvwatts.nrel.gov/pvwatts.php


Typically, less than 3 hours a day of sun (let alone if you are in a river valley with lots of mountain/tree shading), solar gets a little iffy for a cost-effective installation.

Also, in some regions of the USA, GT Solar is becoming less than "welcomed" by utilities/state public utility rules (no Net Metering, no solar "generation" for GT systems).

May or may not be an issue for you yet, or in the near future (sometimes grandfathering will let existing GT Installations continue, but no new installations).

-Bill

ligwyd

Pic attached of service transformer 208Y/120V.

Also attached two pics of grid Tied inverter ID plates.

I notice this inverter says: 380V Nominal Output Voltage. Schneider says this inverter is a 4 wire grounded WYE un-grounded Delta.

Not the right 3 phase voltage......

Just grinding away learning the hard way.

Appreciate any feedback.