Advise sought for large off grid PV system; 480 volt 3-phase [RE-wrenches]

[larry crutcher]

RE-Wrenches,

I am designing an off grid PV system and am looking for input and 
recommendations from experienced installers. Although I have years of 
building battery based systems, this is a big one. The customer has been 
running 60kW diesel generators 24/7 for about 2 decades. They want a PV 
system with batteries that will allow the generators to be shut down 
during the winter and low load periods. Summer loads can be above 
500kWhs per day but winter drops to less than 100kWhs which I can do 
with PV's.

Power details: The site has 480 volt, 3-phase Y distribution and 6 
transformers. There are only two 480 volt distribution circuits leaving 
the generator building. I have failed to locate power equipment that 
will produce 480 volt 3 phase for off grid use. Telecom equipment does 
not look suitable. I have found inverters to produce 60 kW @ 208 volt 3 
phase (Exeltech) and a 75 kva step up transformer for 480Y. I don’t like 
the transformer idea. The generator must be available at any time to 
take over loads. I am thinking of transfer switching @ 480 volts. I 
really would like automation for generators, battery charging, and 
transfer switches.

One generator is scheduled for rebuild and it will have auto-start added 
to it. The site has room for several large ground mount arrays of PV. 
Wind power does not look viable, < 5 m/s @ 30 meters. I am in a desert 
location that has very high ambient temperatures above 115°. A building 
for the batteries and inverters will be climate controlled to 80° F. 

So, how would you propose a solution for this type of site? Do you know 
where I can get 480 3-phase inverters?

Next post I'll ask about batteries, BIG batteries. No, even bigger!

Larry Crutcher
Starlight Solar


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