Direct Power and Virtual Net Metering Possible together?

[Ken9research]

... When the grid goes down the grid is disconnected to protect the linemen...

Thank you again for your valuable insight.

Are you talking about the magenta line? The disconnect separates the grid from the inverter? It does so automatically by PG&E protocol? In other words, is there already some common built-in equipment at one end or the other of the magenta line? "To protect linemen" seems reasonable.

This is exactly one of the capabilities I'm trying to understand. I was thinking that if it's NOT automatic, being that a sub panel for distribution is normally not part of common configuration and the inverter+battery might be safe enough when the grid goes down, then a manual disconnect switch (magenta color again) would be necessary.
diagram.jpg
My understanding, given some clarification, is as follows, referring to diagram:

Three rectangles. One is the grid. Two is the hybrid inverter with connected big battery. Three is the sub panel that distributes to homes. Charging station is nice but adds complexity and can be left out for now.

When the grid is up, the inverter is fully connected. Solar power can flow from the inverter to the grid when the sun is shining. When the sun goes down, nothing happens in the inverter (correct me if wrong) while the grid powers the homes. The grid, in fact, is always powering the homes even when the sun is shining. Remember that NEMV only allows financial benefits because solar power adds to grid power. The big battery (green) might gain some energy, while some homes have PowerWall (smaller green) always adding energy. EV charging is only done inside private garages.

When the grid goes down, assuming there's an automatic disconnect at the magenta line, solar power gets stored in the big battery at a much higher rate. Somebody will have to manually throw the main switch (magenta) to power the sub panel — unless some equipment can make this automatic but NOT fancy expensive micro-grid technology? Or can some switch simultaneously disconnect from grid AND flip to subpanel? Power then comes from the inverter at day and from the big battery at night, going to special sets of circuit breakers at each building. This is where my confusion continues...

The question then becomes how easy or tricky each building manages power from two different sources. This, combined with the cost of trenching cables to each building (green lines), is the reason for the brainstorming.

If such equipment is possible, we homeowners then look at rough prelim costs. However, if such infrastructure costs totally break the deal, then we settle for NEMV only, scratch the sub panel rectangle, and maybe look at adjacent charging stations as the only direct solar benefits in times of blackout.

Having only NEMV ain't bad, but not having any direct solar power during a blackout kinda sucks. Might suck enough to ruin consensus on getting solar altogether.

[Ampster]

Your diagram helps. It all depends on what happens at the buildings when the grid is down. There has to be no connection of the power from the green lines to the house panel so the grid wont be backfed from there. The simple solution which I suggested also worked as a current limit. That was is to have a single 20 Amp circuit feed a receptacle at each home. That receptacle would not be connected in any way to any other grid fed receptacle in the home. That simple solution would require some form of power cable of providing 233 kWs of power to all those homes.

If it is within the realm of possibility that you could find a reliable source of backup power of that scale then that cost and the cost and disruption from trenching has to be weighed against the benefit. Even that amount power would not be enough to charge a Powerwall.

Therefore before we begin thinking about the type of inverters and switches it might be useful to start with loads to see what kind of power would be required. For example let's assume that each home is served by a 100 Amp service panel. It is not likely that all 97 homes are going to draw that much power but any system would have to be designed to do that. The math works out to be over 2 megaWatts.

EDIT: After rereading your post I realized i didn't address some issues or answer some question. I will do that in the context of the load issues above as a separate post..

[Ken9research]

Thanks again. The single feed 20A might be one notch further down in complexity, yes. PowerWalls would only be charged by grid and maybe only sit in garage for homes with EV. Those household's emergency needs would be per their own design within the home.

I realize that it may seem like I'm trying to create a micro-grid at the same time not wanting the futuristic Micro-grid technology. But such endeavor is the nature of research (and brainstorming here).

Here's a diagram to illustrate what I'm thinking:

Keep in mind that I don't know what equipment is available. I'm hoping to find somewhat common or modified-common equipment. Definitely need creativity. I speculate...

When the grid goes down, a switch gets flipped at the canopy and power starts coming from solar or solar battery into the building's electrical closet. The line goes into an adapter switch (fill in the blank) that, with a manual lever action, disconnects from the meter while at the same time connecting to the incoming solar line. The connection here is accessible only by physical key. It's also in front of the meter, not "behind it" or touching PG&E.

Let's say all 77 homes have bimodal inverter (if necessary) for such connection and all tap into, say, 154 kWh of the big battery sitting at solar canopy. This means 2 kWh per home max for the entire night, which can power a 500W refrigerator each home for four hours. Just turn off circuit breakers for everything else. If some have PowerWall, then more energy to other homes — maybe double or triple the 2kWh to get through the night. Sunshine next day brings more power. Buying into such emergency power by 77 households might easily pay for this low-tech switchgear. Chances are that not all 77 will utilized it. Is my math roughly okay?

Then if more fine-tuned accounting is necessary for financial purposes, add some type of in-line metering (fill in the blank) on the solar cable. It can be manually inspected and read by eyeball at the end of the billing cycle to catch the few households that's responsible for draining the main solar battery too quickly. Private agreements signed upon issuance of the physical keys can stipulate a steep ramp up on cost of the emergency solar kWh. It's not grid kWh. It's private.

So the question is, what kind of adapter switch can perform such a manual lever action at the individual meter? What kind of in-line metering? Can it all be kosher with PG&E? Would PG&E even care?
At Meter.jpg

[Ampster]

Are you talking about the magenta line? The disconnect separates the grid from the inverter? It does so automatically by PG&E protocol? In other words, is there already some common built-in equipment at one end or the other of the magenta line?

Yes that is built into most grid tie capable inverters. A grid tie only inverter just disconnects and the house goes dark when the grid goes down. A hybrid inverter is like a switch with two legs, One leg receives and sends power to and from the grid. The other leg only connects the inverter to the load and power goes from the inverter to the load. The hybrid inverter converts the DC from the batteries or the solar panels to AC to run the loads. In that mode it also manages the DC power depending on the load. In a high load situation it might use all the available solar and some of the batteries to serve the load. If the load is less it will use the solar to charge the battery and serve the load. If the battery is full then it will modulate the solar to serve the load. This is an important concept and it is one reason a hybrid inverter is more expensive that a grid tie only inverter.

This is exactly one of the capabilities I'm trying to understand. I was thinking that if it's NOT automatic, being that a sub panel for distribution is normally not part of common configuration and the inverter+battery might be safe enough when the grid goes down, then a manual disconnect switch (magenta color again) would be necessary.

It could be manual or automatic

.........
When the grid is up, the inverter is fully connected. Solar power can flow from the inverter to the grid when the sun is shining. When the sun goes down, nothing happens in the inverter (correct me if wrong) while the grid powers the homes. The grid, in fact, is always powering the homes even when the sun is shining. Remember that NEMV only allows financial benefits because solar power adds to grid power. The big battery (green) might gain some energy, while some homes have PowerWall (smaller green) always adding energy. EV charging is only done inside private garages.

If the grid goes down, assuming there's an automatic disconnect at the magenta line, solar power gets stored in the big battery at a much higher rate. Somebody will have to manually throw the main switch (magenta) to power the sub panel — unless some equipment can make this automatic but NOT fancy expensive micro-grid technology? Or can some switch simultaneously disconnect from grid AND flip to subpanel? Power then comes from the inverter at day and from the big battery at night, going to special sets of circuit breakers at each building. This is where my confusion continues...

Yes an automatic switch could disconnect from the grid and energize the sub panel. What is important, as explained in my earlier post is that the special set of circuit breakers could not be connected to the grid or any of the house panels. That would create a back feed to the grid via the dead grid connection on the right side of your diagram.

The question then becomes how easy or tricky each building manages power from two different sources. This, combined with the cost of trenching cables to each building (green lines), is the reason for the brainstorming.

That is an emerging capability. It is clearly available in complex microgrid systems but if you look at the possible loads that I talked about in my earlier post you are looking at from 230 kiloWatts of load management for a single 20 Amp circuit to each home or 2 megaWatts of load management to power each 100 Amp service panel in the homes. I don't think it would be the load management switchgear or the trenching that would be the big ticket. It would be the source of power to provide just 230 kWatts of Power. Even if that were just peak power for a short time you can pick any number say 50kWs and multiply that by 24 hours and your are still talking about a lot of kWhrs of capacity in a battery. The solar on the canopys might might provide six hours of that but batteries and/or generators would have to carry the rest.

Here are some metrics that you can use and try them out against others. As things scale up you can expect to have the unit costs go down.

The important first step might be to get a hard number on the canopy costs with just grid tie solar. I will see if I can find the 4 year old proposal from Sunworks for carport solar panels for the city of Hermosa Beach. Off the top of my head I was surprised that the cost was less than $3.00 per kW installed as just a grid tie system. The size of the project was about 100kW. I am sure the contractor for Kaiser could give you a ballpark figure.
Battery costs are about $1.00 per Watt hour or $1,000 per kWhr. The important thing to remember is the capacity of the battery is measured in kWhrs, whereas the output of inverters is in kW. Hybrid inverters capable of delivering 6kWs are about $6,000 plus installation. Combination battery/inverters like the Powerwall are all over the board depending on kW peak and kWhr capacity of the battery. You would have to search the net for Generators if you even want to go that route. given the size of some of the loads you may want to give Tesla a call about their Powerpacks which are the equivalent of ten or twenty Powerwalls. They may even be intrigued with your concept as they have been with some Island installations. They are in your neighborhood.
I don't have any metric for trenching, cable and all the other periferal items needed for installation including engineering and plans.

Having only NEMV ain't bad, but not having any direct solar power during a blackout kinda sucks. Might suck enough to ruin consensus on getting solar altogether.

As I have said before you are doing the right thing for your HOA by just researching the possibilities. In a sense you are at the leading edge and I think over the next few year we will see more projects like you are speculating about. Timing is everything and you just don't want to be at the bleeding edge of emerging technology. Actually the technology is tried and proven, it is the application to campus like settings that is emerging.

[Ken9research]

At Meter.jpg

[Mike90250]

UL certified inter-tie equipment cannot be modified and retain it's cert. I've even seen quad outlet boxes with an extra hole drilled, fail inspection, because it was modified.

Any micro grid scheme, where there is shared energy storage, will fail from user abuse. Putting the batteries and inverter in each persons garage, turns THEM into their own gatekeeper.

[Ampster]

Mike has important feedback. The intertie and grid disconnect parts of this design need to be understood in order to shape the possible alternatives. I thought I ha responded to the latest diagram bu can't find my post so I will have to respond later. I have a busy day tomorrow so it might be later.

[Ken9research]

UL certified inter-tie equipment cannot be modified and retain it's cert. I've even seen quad outlet boxes with an extra hole drilled, fail inspection, because it was modified.

Any micro grid scheme, where there is shared energy storage, will fail from user abuse. Putting the batteries and inverter in each persons garage, turns THEM into their own gatekeeper.

Well, this sucks. Of all my open questions, hypothetical examples, reaching ideas and so many words, somebody with a “moderator” title had to come in and pick on what's probably an inaccurate phrase to shut down the entire brainstorming flow. Go ahead and dig in. Keep telling me that that's the biggest mistake.

Nothing constructive. Any "micro-grid" is doomed. So many words from a "moderator."

[Ampster]

Well, this sucks..................

Nothing constructive. Any "micro-grid" is doomed. So many words from a "moderator."

No worries. If the batteries in the garages are Tesla Powerwalls they will be installed per codes. I am not sure what modifications Mike is actually talking about since this is a design concept. A project of this size will have engineers and licensed contractors involved when it goes to the building department for a permit.
I still have to understand and respond to your latest diagram and am dashing this off while having coffee before my first appointment.

[SunEagle]

Well, this sucks. Of all my open questions, hypothetical examples, reaching ideas and so many words, somebody with a “moderator” title had to come in and pick on what's probably an inaccurate phrase to shut down the entire brainstorming flow. Go ahead and dig in. Keep telling me that that's the biggest mistake.

Nothing constructive. Any "micro-grid" is doomed. So many words from a "moderator."

If you can control the "customers" so they do not abuse their share of the battery system then you have a chance a home based "micro-grid" will work. But I have little faith for most people when it comes to sharing and IMO unless you have someone in charge and responsible to meter out the assets a home grown system will fail.

I just don't think a socialistic approach is possible in today's environment. People are just greedy.

[Ken9research]

If you can control the "customers" so they do not abuse their share of the battery system then you have a chance a home based "micro-grid" will work. But I have little faith for most people when it comes to sharing and IMO unless you have someone in charge and responsible to meter out the assets a home grown system will fail.

I just don't think a socialistic approach is possible in today's environment. People are just greedy.

That's why I was reaching for equipment ideas. Without knowing what's possible, even a home-grown tyrannical system will fail. Don't even have to assume socialistic.

[J.P.M.]

Well, this sucks. Of all my open questions, hypothetical examples, reaching ideas and so many words, somebody with a “moderator” title had to come in and pick on what's probably an inaccurate phrase to shut down the entire brainstorming flow. Go ahead and dig in. Keep telling me that that's the biggest mistake.

Nothing constructive. Any "micro-grid" is doomed. So many words from a "moderator."

I often add "Take what you want of the above. Scrap the rest." to the bottom of my posts.
I'd also wonder how much brain goes into any brainstorming that can be shut down by expressing an opinion.
If you disagree with Mike's or anyone's opinion as offered, I'd suggest you go back to your search for someone knowledge about NEMV, or simply consider what Mike writes.
I've found that not everyone who tells me what I don't like or what may run counter to what I want to hear is my enemy or is trying to hurt me.

[Ken9research]

I often add "Take what you want of the above. Scrap the rest." to the bottom of my posts.
I'd also wonder how much brain goes into any brainstorming that can be shut down by expressing an opinion.
If you disagree with Mike's or anyone's opinion as offered, I'd suggest you go back to your search for someone knowledge about NEMV, or simply consider what Mike writes.
I've found that not everyone who tells me what I don't like or what may run counter to what I want to hear is my enemy or is trying to hurt me.

Apparently you don't understand brainstorming. Hint: it's not taking everything in willy nilly. If I had the glorious title of "moderator" I would soften my first words when diving into a discussion. Seems you enjoy the stuffiness of an ol' boys club.

[Ken9research]

Mike has important feedback. The intertie and grid disconnect parts of this design need to be understood in order to shape the possible alternatives. I thought I ha responded to the latest diagram bu can't find my post so I will have to respond later. I have a busy day tomorrow so it might be later.

Just wanted to thank you for originally describing this discussion as "brainstorming" because that's the highest form of discussion. I was only asking for equipment ideas. Some may have, some may not. Silence could be golden. Some may only ofter negativism. Some only want to talk politics. Some just want to argue.

Maybe I've squeezed the turnip here enough.

[J.P.M.]

Apparently you don't understand brainstorming. Hint: it's not taking everything in willy nilly. If I had the glorious title of "moderator" I would soften my first words when diving into a discussion. Seems you enjoy the stuffiness of an ol' boys club.

No, To use your word, I think old boys' network sucks.
As for brainstorming, I'd guess there's a better than 50/50 chance I did more of it before you were born than you've done your entire live up to this point.

But I do enjoy spirited, honest discussions between individuals who aren't so thin skinned and unsure of themselves that they confuse honest opinions and perhaps difficult realities with attitude and rancor.

Enjoy stewing in your attitude.