Design of Grid Tied Systew with Off-Grid Option?

[FS2020]

I want to install a solar PV system that is grid connected, but that can go off the grid. Below is a schematic of a conceptual design -- not the actual components. I am seeking advice on how do to this design and what components to use.
Thanks!
Frank S.
Grid-Tie_and_Off-Grid_Design.jpg

[Sunking]

No need to redesign the wheel as hybrid systems are offered and on the market under Outback XW series.

With that said would be fairly foolish to use battery backup for emergency power. Best option is just a Emergency Generator and ATS. If you go the hybrid route still requires a generator. The hybrid inverters are much more expensive, still require a generator, and very expensive batteries to replace every few years.

[FS2020]

Batteries, foolish? There are pros and cons to everything. I live in a densely populated suburb. If the grid goes down, when I fire up a generator, it will announce to the neighborhood that I have electricity and gasoline. I'm fine with sharing, if it's my decision.

[Sunking]

Batteries, foolish? There are pros and cons to everything. I live in a densely populated suburb. If the grid goes down, when I fire up a generator, it will announce to the neighborhood that I have electricity and gasoline. I'm fine with sharing, if it's my decision.

Like I said with battery hybrid system still requires a generator and the lights will give you away.

[FS2020]

I don’t agree. A large enough battery bank, supplemented with a large enough solar PV system, is more than adequate to run basic necessities. It may not be as economical as using a generator, but this is not an entirely economic decision. And I can turn off my lights.
Frank, MSME

[FS2020]

In any case, I was asking for advice about the design and components to use. I make no claims to be experienced with this kind of design, that's why I asked. I'll follow up your advice to look into Outback hybrid systems. But I was hoping to use microinverters at the panels to avoid long runs of heavy DC cables, for safety reasons.
Frank, MSME, and 28 years at DOE.

[Sunking]

But I was hoping to use microinverters at the panels to avoid long runs of heavy DC cables, for safety reasons. Frank, MSME, and 28 years at DOE.

Well that ends your battery option all together. Dereck, MSEE, PE 33 Years in Power Plant Generation Design/Build, Transmission, and Alternative Energy. I actually built the stuff and got rich doing it in the private sector. Did you get rich in the public sector? Enough to afford thousands of dollars of batteries every few years? I didn't.

You are right, you could put up a large enough panel and battery to do without a generator. If you used it every day would cost you around 10 times more than the POCO would charge you for the rest of your life. Use it for emergencies only will cost you thousands of times more than a generator and fuel. Batteries setting around doing nothing still need replaced every 5 years like working batteries. If you use 10 Kwh/day requires a around $10,000 of batteries replaced every 5 years. Or about $1000 worth of batteries for every Kwh you want in a day from batteries. To have that much battery requires your buddies permission over at the Employment Prevention Agency with permit fees and annual inspections by your local FD.

With a Hybrid system works like a hybrid vehicle. You use a smaller battery to keep cost down for short distances, and an on board generator to recharge the batteries and take over the load for the long haul stuff. Repeat cycle.

[Shockah]

In any case, I was asking for advice about the design and components to use. I make no claims to be experienced with this kind of design, that's why I asked. I'll follow up your advice to look into Outback hybrid systems. But I was hoping to use microinverters at the panels to avoid long runs of heavy DC cables, for safety reasons.
Frank, MSME, and 28 years at DOE.

Now that you've shared your credentials and made it clear that you've set out to do this at any cost,

I have to ask, do you want the on-grid/off-grid switch to be automatic, or manual?

[FS2020]

Well that ends your battery option all together. Dereck, MSEE, PE 33 Years in Power Plant Generation Design/Build, Transmission, and Alternative Energy. I actually built the stuff and got rich doing it in the private sector. Did you get rich in the public sector? Enough to afford thousands of dollars of batteries every few years? I didn't.

You are right, you could put up a large enough panel and battery to do without a generator. If you used it every day would cost you around 10 times more than the POCO would charge you for the rest of your life. Use it for emergencies only will cost you thousands of times more than a generator and fuel. Batteries setting around doing nothing still need replaced every 5 years like working batteries. If you use 10 Kwh/day requires a around $10,000 of batteries replaced every 5 years. Or about $1000 worth of batteries for every Kwh you want in a day from batteries. To have that much battery requires your buddies permission over at the Employment Prevention Agency with permit fees and annual inspections by your local FD.

With a Hybrid system works like a hybrid vehicle. You use a smaller battery to keep cost down for short distances, and an on board generator to recharge the batteries and take over the load for the long haul stuff. Repeat cycle.

I think I'm in the wrong forum. I'm sure you are smarter and richer than I am. But I didn't come here to be insulted for not being as smart as you. I came asking for advice.
I have my areas of expertise, solar is not one of them. But I don't insult people who ask me for advice about my area of expertise.
Goodbye

[Shockah]

I think I'm in the wrong forum. I'm sure you are smarter and richer than I am. But I didn't come here to be insulted for not being as smart as you. I came asking for advice.
I have my areas of expertise, solar is not one of them. But I don't insult people who ask me for advice about my area of expertise.
Goodbye

I thought you received great advice, just for asking.

I'm still curious if you wanted the switching done manually or automatically.

[Shockah]

Well that ends your battery option all together. Dereck, MSEE, PE 33 Years in Power Plant Generation Design/Build, Transmission, and Alternative Energy. I actually built the stuff and got rich doing it in the private sector. Did you get rich in the public sector? Enough to afford thousands of dollars of batteries every few years? I didn't.

You are right, you could put up a large enough panel and battery to do without a generator. If you used it every day would cost you around 10 times more than the POCO would charge you for the rest of your life. Use it for emergencies only will cost you thousands of times more than a generator and fuel. Batteries setting around doing nothing still need replaced every 5 years like working batteries. If you use 10 Kwh/day requires a around $10,000 of batteries replaced every 5 years. Or about $1000 worth of batteries for every Kwh you want in a day from batteries. To have that much battery requires your buddies permission over at the Employment Prevention Agency with permit fees and annual inspections by your local FD.

With a Hybrid system works like a hybrid vehicle. You use a smaller battery to keep cost down for short distances, and an on board generator to recharge the batteries and take over the load for the long haul stuff. Repeat cycle.

If you read between the lines, Frank, the advice is golden.

Frankly, Dereck's advice could save you thousand$ of dollar$ in less than 15 minutes... even better than GEICO

[FS2020]

I'm sure Dereck's advice is golden under the extreme scenario he created. But Dereck does not have enough info (and did not ask) about what I'm trying to do, i.e., the small electricity loads I'm trying to support in a grid down scenario.
But that's OK, I'm now getting excellent advice from my "buddies over at the Employment Prevention Agency"
Frank, the Foolish Civil Servant

[inetdog]

I'm sure Dereck's advice is golden under the extreme scenario he created. But Dereck does not have enough info (and did not ask) about what I'm trying to do, i.e., the small electricity loads I'm trying to support in a grid down scenario.
But that's OK, I'm now getting excellent advice from my "buddies over at the Employment Prevention Agency"
Frank, the Foolish Civil Servant

Stick around awhile, Frank.
Pay no attention to the man behind the curtain.

Given that you want to do it and that we have already given most of the reasons not to, there is definitely room for discussion and advice.

Two ways to go to allow you to make use of your panels when the grid is down are:

1. Use a combination of SMA Sunny Boy grid tie inverters for your primary supply and a Sunny Island stand alone inverter connected to its own sub-array of panels and with batteries. Not cheap, but well engineered and reliable.

2. Get a suitable hybrid inverter from Xantrex. Choose a model with "sell back" capability for use when on grid, in addition to the standalone operating mode.
Or go all the way and set it up for "generator support" (search for that thread in this forum) to have maximum off-grid flexibility and sustainability.

3. Going purely PV and battery with no generator component in the design will probably double the price, but if you want to go that way, it will be your choice.

[Shockah]

I've often pondered the same thought... that is why I asked if you preferred manual or automatic.

I often wonder what can I do with Roof-Top PV panels when the grid is down... I'm not thinking for a few hours, but for a few weeks when the next hurricane or earthquake strikes our tiny island.

Sure a generator will suffice, until the gas tank empties... and I'm not a fan of standing in long lines at an overpriced pump.

This illustrates my thought on how it could be done. Micro inverters would require a switch at EACH input, vs just one switch at string inverter.

frank2.jpg

As for Batteries, I'm thinking just enough amp-hours to keep the perishables from rotting, modems on (if available) and a few lights. And yes, Dereck, that is a foolish amount of economic waste having those batteries sitting there waiting on a natural disaster.... really no way around that expense if you wanna be over-prepared.... kind of like an expensive comfort insurance policy?

[inetdog]

Sure a generator will suffice, until the gas tank empties... and I'm not a fan of standing in long lines at an overpriced pump.

Which does not work since the station does not have a generator.....