PV Array (microinverter) with Generator

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caribconsult

Senior Member
Location
Añasco, Puerto Rico
Occupation
Retired computer consultant
I understand the OP wasn't in PR....I brought that up only to let you know that things work a bit differently here. Our version of 'modern' might have been outdated 25 years ago in the states.

That was a good explanation of the 'backfeeding the gen and why you can't do it' topic. Thanks for that. I was wondering why someone would even think about doing such a thing? Spinning the motor backwards sounds like something a bunch of 8th graders would try to do to one of their dad's generators just to see what happens! More likely you'd fry something in the gen electronics since it isn't expecting input at the outputs.

I watch with great curiosity the operation of the Tesla system and what it seems to be doing, since there's no grid to unload the excess juice to (in my case) once the PW is charged then it just throttles down the panels with a Hz shift up to where it just equals the demand from the house, if there's sun. If not much sun, it blends the PW output with the PV output to supply the house, switching instantly to 'top off' the PW when there's a burst of sunlight. Wash, rinse, repeat until sundown. Pretty clever and it works silently. We like that part a lot, especially after living on our gen for 4 months after hurricane María 3 years ago. Thanks for your input - you always shed some light on the topic.
 

caribconsult

Senior Member
Location
Añasco, Puerto Rico
Occupation
Retired computer consultant
BTW, several posters inquired about using a gen along with the basic system. I think what they want is something that will kick off the gen if there's no grid, no solar and a low battery, and I'm not sure the gear to do that automatically is available. You'd need at least another circuit somewhere in the PW or gateway to accept the gen output and make it an input like the grid but wired to accommodate gen wave forms and noise and another circuit to trigger the gen's electric start and shutdown. And it would have to automatically ignore the grid once the gen is on and connected or shut the gen down and switch back to the grid if it suddenly came on and you were grid-tied. I'm not sure that stuff is available, but you can do it manually with a switch which transfers the main load directly to the gen and lifts it from the output of the PW/Gate. And shutoff the grid to gateway breaker until the gen is no longer being used. The PW will continue to charge if you have some sun, and when the battery is charged up you can throw the load switch back to 'PW' position and off you go. And shutting off the gen manually is simple enough...close the fuel valve and let it run dry. We rarely have to do this because there's usually grid available but there have been times it's not and we use the gen if there's little sun. Since we're not 100% grid tied, it amounts to throwing one switch and firing up the electric start gen. Doing it manually isn't exactly a stressful ordeal and it keeps you in mind of how your system works. And it's fairly inexpensive for a large handled DPDT-center off switch in a box.
 

jaggedben

Senior Member
Location
Northern California
Occupation
Solar and Energy Storage Installer
You can puy an ordinary ATS between the Powerwalls and the backup loads, that's one way to do it. Generator will not be able to charge the batteries though. AFAIK Tesla does not support a more integrated way to do it. Other battery systems do.
 

caribconsult

Senior Member
Location
Añasco, Puerto Rico
Occupation
Retired computer consultant
I suppose....you could just put the ATS between the output of the PW and the load, so if nothing came out of the PW, meaning no battery, no solar, no grid (if tied) that would switch on the gen and shut it off when something came out of the PW assembly, whether it's a resumption of the grid, or the battery got charged...doesn't matter. Nice simple solution.
 

caribconsult

Senior Member
Location
Añasco, Puerto Rico
Occupation
Retired computer consultant
What is the new PW "RED" unit? How does it stack up against the standard PW2? Is this some limited version that they give only as a reward to referring new customers?
 

caribconsult

Senior Member
Location
Añasco, Puerto Rico
Occupation
Retired computer consultant
What I've noticed is that when the PW is charged and there's still plenty of sunlight, the panels throttle down via a frequency change that lowers the output to match the house demand and that continues until the sun starts to go down, at which point the system blends PW energy with the PV energy that's available and sends it all to the house....it doesn't try to 'force feed' anything, or shut the system down because there's no place to send the excess....there is no excess. Then the system gradually shifts over to full PW operation when there's nothing from the PV array. I think that's a good system.
 

gadfly56

Senior Member
Location
New Jersey
Occupation
Professional Engineer, Fire & Life Safety
What is the new PW "RED" unit? How does it stack up against the standard PW2? Is this some limited version that they give only as a reward to referring new customers?
It looks like it's just "thank you" to folks who made qualifying referrals. Nice if you like that sort of thing, I suppose.
 

gadfly56

Senior Member
Location
New Jersey
Occupation
Professional Engineer, Fire & Life Safety
What I've noticed is that when the PW is charged and there's still plenty of sunlight, the panels throttle down via a frequency change that lowers the output to match the house demand and that continues until the sun starts to go down, at which point the system blends PW energy with the PV energy that's available and sends it all to the house....it doesn't try to 'force feed' anything, or shut the system down because there's no place to send the excess....there is no excess. Then the system gradually shifts over to full PW operation when there's nothing from the PV array. I think that's a good system.
That's the way I'd expect it to work, seamless transition/combination as needed. Now, in an ideal world where money didn't matter, could you put together something with the grid, generator backup, Powerwalls, and PV system to automatically pick what feeds the loads, based on a priority list? Throw in selling back to the utility when the batteries are fully charged and the loads are low, just for fun.
 

gadfly56

Senior Member
Location
New Jersey
Occupation
Professional Engineer, Fire & Life Safety
When Tesla first announced the 'prize for referrals' program, they said you'd receive a regular PW. Is the red one somewhat less powerful? A bargain version? Or just red?
Just red. But hey, Elon and company singed it for you! Could wind up a collector's item. :rolleyes:
 

caribconsult

Senior Member
Location
Añasco, Puerto Rico
Occupation
Retired computer consultant
So it's just more BS marketing? The RED unit is the same as the regular PW2, apparently. I'd recommend Tesla, except for one tiny detail - our installer is worthless at service. They did a nice job installing it but getting them to come out for service means paying for it....they sold it as 'totally guaranteed' but they've apparently changed their mind. And I'm told that similar issues exist with many other Tesla distributors here on the island.

Thanks for the info.
 
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