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3D Modeled Energy Assets Found in Latest Firmware

wjgjr

Active Member
May 11, 2020
1,305
1,037
Silver Spring, MD
Hi,

I'm looking to do a similar setup and to have a tesla roof and 2 powerwalls installed...I intend to use a standby natural gas generator as a grid replacement during a prolonged outage during the winter... The idea is I can run the house during the day and charge the PW on the SBG then turn off the generator at night and run the house off the PW...if the sun comes out and the snow comes off the roof I can run the house off solar and charge the PW during the day...

the more I read about the way tesla operates is if the grid goes out during even a sunny day is shuts the panels off and you run only off batteries? That seams not only dumb (assuming your PV is sized to properly support the home load during the day) but an ineffective use of the panels... If the grid goes out the ATS should disconnect from the grid and the PV system and PWs should create their own grid and should power anything its connected to. Can you share drawings of how your setup is installed please?
For me the entire purpose of PV and PW and a SBG is to be up and running in any season in any grid utility outage situation. SolArk inverters with other battery suppliers can do just that.

The behavior of solar + PW is not quite what you described, and it does make sense once you work through the options. When there is an outage, the solar array cannot generate more than can be consumed. (This is also true when the grid is up, but the grid is effectively an infinite sink for purposes of residential solar power generation.) In an outage, the solar can be used either to run the home or to charge the PWs. If the PWs are full and the home load is less than the incoming solar, this will quickly become dangerous. So, one of two things happens. For older installs, the solar is shutoff completely, and the PWs run the home. For some newer installs, the systems are capable of curtailing the solar to match the home load. In the former case, this behavior only persists until the PWs are drained to a level where solar can resume. (In my case, it shuts off around 97-98% and comes back in the 92-95% range - it likely checks about every 5 minutes to see if the PWs have room for more energy.) In the latter case, the PWs should generally remain in that 97-98% range.

In either case, your system will attempt to maintain near-full batteries whenever possible (solar generation exceeds home load) but will curtail or cycle off the solar as a safety measure whenever the PWs get too full. All you lose out on in an outage is the benefits of net metering/load shifting since the grid is not available for that purpose.
 

Sunnyboy

Member
Apr 6, 2021
11
0
New York
The behavior of solar + PW is not quite what you described, and it does make sense once you work through the options. When there is an outage, the solar array cannot generate more than can be consumed. (This is also true when the grid is up, but the grid is effectively an infinite sink for purposes of residential solar power generation.) In an outage, the solar can be used either to run the home or to charge the PWs. If the PWs are full and the home load is less than the incoming solar, this will quickly become dangerous. So, one of two things happens. For older installs, the solar is shutoff completely, and the PWs run the home. For some newer installs, the systems are capable of curtailing the solar to match the home load. In the former case, this behavior only persists until the PWs are drained to a level where solar can resume. (In my case, it shuts off around 97-98% and comes back in the 92-95% range - it likely checks about every 5 minutes to see if the PWs have room for more energy.) In the latter case, the PWs should generally remain in that 97-98% range.

In either case, your system will attempt to maintain near-full batteries whenever possible (solar generation exceeds home load) but will curtail or cycle off the solar as a safety measure whenever the PWs get too full. All you lose out on in an outage is the benefits of net metering/load shifting since the grid is not available for that purpose.
So what you are saying is that the newer installs load shed/generation shed (generation = load) and can power the house off of PV and then use the batteries at night? I'd like to see how this works so that I can install this system.How does tesla accomplish this?
 

jjrandorin

Moderator, Model 3, Tesla Energy Forums
Nov 28, 2018
10,409
11,754
Riverside Co. CA
So what you are saying is that the newer installs load shed/generation shed (generation = load) and can power the house off of PV and then use the batteries at night? I'd like to see how this works so that I can install this system.How does tesla accomplish this?

I dont quite understand what you are saying / asking.

A PV + powerwall installation has a tesla gateway that manages power flow. Solar will power the home and fill the batteries when there is excess solar (or you can direct all solar to fill the batteries if there is not excess solar), and at night, the home can run off the batteries (provided there is enough storage (batteries) installed to cover the home load.

Also, when you say "so I can install this system", I may be making an incorrect assumption, but you mean "so I can pay a certified installer or tesla to install this system", right? Cause you are not going to self install powerwalls. I mentioned this only because the screen name you picked is of an inverter brand.
 
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Sunnyboy

Member
Apr 6, 2021
11
0
New York
I dont quite understand what you are saying / asking.

A PV + powerwall installation has a tesla gateway that manages power flow. Solar will power the home and fill the batteries when there is excess solar (or you can direct all solar to fill the batteries if there is not excess solar), and at night, the home can run off the batteries (provided there is enough storage (batteries) installed to cover the home load.

Also, when you say "so I can install this system", I may be making an incorrect assumption, but you mean "so I can pay a certified installer or tesla to install this system", right? Cause you are not going to self install powerwalls. I mentioned this only because the screen name you picked is of an inverter brand.
yes...I should have said so I can have this system installed. I am not DIY solar+batteries+ generator. My screen name is just a coincidence. I did not know that was an inverter name..it's actually a nick name my dad used to call me.

My question is how the system performs in a grid outage. I want the system designed in a way that during a grid outage i can disconnect from the grid and the solar and or generator handles the home load during the day and I can shut off the generator at night and run off batteries.
 

jjrandorin

Moderator, Model 3, Tesla Energy Forums
Nov 28, 2018
10,409
11,754
Riverside Co. CA
yes...I should have said so I can have this system installed. I am not DIY solar+batteries+ generator. My screen name is just a coincidence. I did not know that was an inverter name..it's actually a nick name my dad used to call me.

My question is how the system performs in a grid outage. I want the system designed in a way that during a grid outage i can disconnect from the grid and the solar and or generator handles the home load during the day and I can shut off the generator at night and run off batteries.

The solar + PV never sees the generator the generator will not be charging the batteries) but other than that stipulation, thats how it works. I dont have a generator, but my understanding (which can be corroborated by @h2ofun and @jhn_ among those who have both here), but the generator ends up being a "backup for the backup".

If you have both, in a grid outage situation, the PV powers the home / fills the batteries. When there is no PV ( at night) the home runs on batteries. If the batteries run out before the morning, you can switch to generator power. If the batteries dont run out before morning, then the PV will start filling the batteries again.

The situation you described earlier, was a specific circumstance where:

1. There is a grid outage (no grid)
2. PV is filling batteries / running home
3. batteries get full during the day.

In that specific instance, since there is no where for the power to go (no grid) the "system" (tesla gateway + powerwalls) will shut off the PV and run the home off batteries until the batteries are drained enough to accept more PV (solar). In order to not "waste" that PV that would be generated, but is not because it has no place to go, one can increase home loads if they find themselves in this very specific situation by doing things like washing clothes, charging EVs etc.

In the above (specific) situation, the home is still being powered by batteries when there is no grid. Its just that IF there is no grid, and IF the batteries are full during PV generation time, the PV will be turned off by the batteries / gateway until such time as the batteries can accept more charge. It appears like you maybe thought "the system" would turn off meaning the home wouldnt be powered by batteries either in the above specific case.

If you have a generator, it does not get involved at all in the above, you only would turn it on IF there was a grid outage (no grid) and IF the batteries could no longer power the home, which would be in the evening, after the home load had depleted the battery storage before the sun came back up again (or there was no sun during the day).
 

jhn_

Member
Jan 21, 2021
232
240
Northeast United States
Just corroborating since I was mentioned. We have generator and Powerwalls and it works just the way @wjgjr and @jjrandorin explained so well. Generator is backup to the backup and only kicks in if grid is down and Powerwalls run out. No charging Powerwalls from the generator as the way the circuit is designed with the TEG2, the Powerwalls don’t even know the generator exists. The generator hangs off the load side of the panel not the generation side.

Tesla has docs on this. I just cannot find them online at the moment other than this high level overview on their website.
 
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h2ofun

Active Member
Aug 11, 2020
2,937
564
auburn, ca
The solar + PV never sees the generator the generator will not be charging the batteries) but other than that stipulation, thats how it works. I dont have a generator, but my understanding (which can be corroborated by @h2ofun and @jhn_ among those who have both here), but the generator ends up being a "backup for the backup".

If you have both, in a grid outage situation, the PV powers the home / fills the batteries. When there is no PV ( at night) the home runs on batteries. If the batteries run out before the morning, you can switch to generator power. If the batteries dont run out before morning, then the PV will start filling the batteries again.

The situation you described earlier, was a specific circumstance where:

1. There is a grid outage (no grid)
2. PV is filling batteries / running home
3. batteries get full during the day.

In that specific instance, since there is no where for the power to go (no grid) the "system" (tesla gateway + powerwalls) will shut off the PV and run the home off batteries until the batteries are drained enough to accept more PV (solar). In order to not "waste" that PV that would be generated, but is not because it has no place to go, one can increase home loads if they find themselves in this very specific situation by doing things like washing clothes, charging EVs etc.

In the above (specific) situation, the home is still being powered by batteries when there is no grid. Its just that IF there is no grid, and IF the batteries are full during PV generation time, the PV will be turned off by the batteries / gateway until such time as the batteries can accept more charge. It appears like you maybe thought "the system" would turn off meaning the home wouldnt be powered by batteries either in the above specific case.

If you have a generator, it does not get involved at all in the above, you only would turn it on IF there was a grid outage (no grid) and IF the batteries could no longer power the home, which would be in the evening, after the home load had depleted the battery storage before the sun came back up again (or there was no sun during the day).
Yep, thats the way my generator backup backup works
 
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Sunnyboy

Member
Apr 6, 2021
11
0
New York
Thanks all for the explanation. I think I understand how this works now. the PWs shut off of the PV if there's no grid to go to (grid outage) and the batteries are full and the generator does not charge the batteries. This is by design through the tesla gateway. I'm learning the terminology and how all these systems work together. Thanks for bearing with me.
The part about turning on load to trick the PV to come back on is news to me. Thats how I thought it worked in the first place - or I think it SHOULD work. Regardless of grid status if there is sufficient solar generation, the house would draw power from the panels first. If there was more demand than the PV could supply and the grid was available it would pull the remaining requirement from the grid and work together...In a grid outage if there was more demand than the PV could supply the batteries and PV would handle the load together. Basically creating a micro grid on your property using the PV and the PW to supply power. I thought that's how it worked but it seems to not be designed that way. Is there a law tesla is abiding by preventing the batteries being charged by a generator? do the batteries get charged by the grid at all? is this simply a limitation of how these system integrate or by how they are installed?
 

jhn_

Member
Jan 21, 2021
232
240
Northeast United States
Is there a law tesla is abiding by preventing the batteries being charged by a generator? do the batteries get charged by the grid at all? is this simply a limitation of how these system integrate or by how they are installed?
I think it is just a design decision on Tesla’s part to keep the installs simple and also reduce potential maintenance in the future by not integrating the generator into the TEG2. It may also not be in their interest of selling more Powerwalls or promoting clean energy. There is no technical reason an input to the TEG2 couldn’t take an input feed from a generator like it does from the PV inverter. Once these things come off warranty in a few years I’m sure someone will try hooking up a generator to the TEGs PV input.

In the United States Tesla doesn’t allow Powerwalls to charge from the grid, this seems to be so they don’t get negative attention from people taking the federal tax credit for the batteries but then using them from non-PV input. That is not allowed in the tax code. There is a bit of an exception built in... storm watch mode when an algorithm decides that there is a chance of a Power outage in your area. This can be toggled on or off.
 
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Sunnyboy

Member
Apr 6, 2021
11
0
New York
I think it is just a design decision on Tesla’s part to keep the installs simple and also reduce potential maintenance in the future by not integrating the generator into the TEG2. It may also not be in their interest of selling more Powerwalls or promoting clean energy. There is no technical reason an input to the TEG2 couldn’t take an input feed from a generator like it does from the PV inverter. Once these things come off warranty in a few years I’m sure someone will try hooking up a generator to the TEGs PV input.

In the United States Tesla doesn’t allow Powerwalls to charge from the grid, this seems to be so they don’t get negative attention from people taking the federal tax credit for the batteries but then using them from non-PV input. That is not allowed in the tax code. There is a bit of an exception built in... storm watch mode when an algorithm decides that there is a chance of a Power outage in your area. This can be toggled on or off.
OK so what you're saying is it sounds like charging batteries from the grid is a function of the funding of the solar project...if you take the tax incentives you cant but if you pay outright the full amount you can?....and that they will honor that an enable that on your system?
 

MorrisonHiker

S 100D 2021.32.20
Mar 8, 2015
10,157
9,676
Colorado
OK so what you're saying is it sounds like charging batteries from the grid is a function of the funding of the solar project...if you take the tax incentives you cant but if you pay outright the full amount you can?....and that they will honor that an enable that on your system?
By default in the United States, Tesla programs the Powerwalls so that they can only be charged via the grid if Storm Watch has been enabled and activated. Some customers in the United States have been able to get Tesla to change those settings but I believe it required cooperation or documentation from the customer's utility company.

Customers in other countries, such as the UK are able to charge their Powerwalls from the grid by default.
 

jjrandorin

Moderator, Model 3, Tesla Energy Forums
Nov 28, 2018
10,409
11,754
Riverside Co. CA
OK so what you're saying is it sounds like charging batteries from the grid is a function of the funding of the solar project...if you take the tax incentives you cant but if you pay outright the full amount you can?....and that they will honor that an enable that on your system?
Like @MorrisonHiker said, basically if you are in the US, no you will not be grid charging whenever you want to if you have solar and tesla batteries. Other battery systems may be different.
 

jhn_

Member
Jan 21, 2021
232
240
Northeast United States
OK so what you're saying is it sounds like charging batteries from the grid is a function of the funding of the solar project...if you take the tax incentives you cant but if you pay outright the full amount you can?....and that they will honor that an enable that on your system?
No. Tesla only sells Powerwalls one way in the US, presumably to keep things simple and say all their equipment is covered by the federal tax credits. Grid charging is disabled. It is allowed in other countries.
 

jjrandorin

Moderator, Model 3, Tesla Energy Forums
Nov 28, 2018
10,409
11,754
Riverside Co. CA
No one should ever "advise" anyone to do anything like that, unless they are willing to take responsibility for that person messing up their setup, so I will not be mentioning that "workaround", nor quoting the thread where the person says its possible. I am not willing to go down that road or advise others to do so.

Given the above, I feel comfortable with stating whats possible or not with 'normal' means. feel free to PM people and give them whatever information / help /support on it you want to provide, though.
 
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h2ofun

Active Member
Aug 11, 2020
2,937
564
auburn, ca
No one should ever "advise" anyone to do anything like that, unless they are willing to take responsibility for that person messing up their setup, so I will not be mentioning that "workaround", nor quoting the thread where the person says its possible. I am not willing to go down that road or advise others to do so.

Given the above, I feel comfortable with stating whats possible or not with 'normal' means. feel free to PM people and give them whatever information / help /support on it you want to provide, though.
totally agree
 
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miimura

Well-Known Member
Aug 21, 2013
6,495
6,259
Los Altos, CA
Thanks all for the explanation. I think I understand how this works now. the PWs shut off of the PV if there's no grid to go to (grid outage) and the batteries are full and the generator does not charge the batteries. This is by design through the tesla gateway. I'm learning the terminology and how all these systems work together. Thanks for bearing with me.
The part about turning on load to trick the PV to come back on is news to me. Thats how I thought it worked in the first place - or I think it SHOULD work. Regardless of grid status if there is sufficient solar generation, the house would draw power from the panels first. If there was more demand than the PV could supply and the grid was available it would pull the remaining requirement from the grid and work together...In a grid outage if there was more demand than the PV could supply the batteries and PV would handle the load together. Basically creating a micro grid on your property using the PV and the PW to supply power. I thought that's how it worked but it seems to not be designed that way. Is there a law tesla is abiding by preventing the batteries being charged by a generator? do the batteries get charged by the grid at all? is this simply a limitation of how these system integrate or by how they are installed?
There is a very good reason why Tesla doesn't allow generator charging the Powerwalls. The entire Powerwall system is inherently a grid tied system. When the grid goes down, the switch in the Gateway opens to isolate the system from the grid and the Powerwalls become the "grid master" and they control the frequency of the islanded micro-grid. As far as the solar grid-tied inverters are concerned, there is still a grid. The solar only needs to be shut down when the batteries get full or there is a chance that the solar production could make the micro-grid unstable. This can happen if you have more than 5kW per Powerwall of solar production. So, when the grid is down and you have a lot of solar production, you can do things like charge your EV to soak up the extra kW or extra kWh so that the batteries don't get overloaded (kW) or too full (kWh).

Now on to the generator. When the grid is down, the Powerwalls are the "grid master". A generator is normally a free-wheeling power source that does not have to synchronize to anything. The possible exception is inverter generators that are designed to be "stackable" so that multiple units can increase their total supply to common loads. So, the inherent reason for Tesla not to allow Powerwalls to interact with a generator is that there is no mechanism for them to synchronize their AC waveform. Other battery inverter systems have separate AC inputs that act as battery chargers and thereby avoid the AC synchronization issue altogether. The Powerwall 2 has no interface to the DC battery pack inside, so it cannot be charged in that manner.

Since Tesla is now making their own inverters, they could make a version that is designed to take generator input, rectified to DC, and then inverted to synchronize to the micro-grid. With some software, they could set up some rules for when the generator should run and they could have a very nice hybrid battery / solar / generator system. I have never heard that such a thing is planned at Tesla.
 

h2ofun

Active Member
Aug 11, 2020
2,937
564
auburn, ca
There is a very good reason why Tesla doesn't allow generator charging the Powerwalls. The entire Powerwall system is inherently a grid tied system. When the grid goes down, the switch in the Gateway opens to isolate the system from the grid and the Powerwalls become the "grid master" and they control the frequency of the islanded micro-grid. As far as the solar grid-tied inverters are concerned, there is still a grid. The solar only needs to be shut down when the batteries get full or there is a chance that the solar production could make the micro-grid unstable. This can happen if you have more than 5kW per Powerwall of solar production. So, when the grid is down and you have a lot of solar production, you can do things like charge your EV to soak up the extra kW or extra kWh so that the batteries don't get overloaded (kW) or too full (kWh).

Now on to the generator. When the grid is down, the Powerwalls are the "grid master". A generator is normally a free-wheeling power source that does not have to synchronize to anything. The possible exception is inverter generators that are designed to be "stackable" so that multiple units can increase their total supply to common loads. So, the inherent reason for Tesla not to allow Powerwalls to interact with a generator is that there is no mechanism for them to synchronize their AC waveform. Other battery inverter systems have separate AC inputs that act as battery chargers and thereby avoid the AC synchronization issue altogether. The Powerwall 2 has no interface to the DC battery pack inside, so it cannot be charged in that manner.

Since Tesla is now making their own inverters, they could make a version that is designed to take generator input, rectified to DC, and then inverted to synchronize to the micro-grid. With some software, they could set up some rules for when the generator should run and they could have a very nice hybrid battery / solar / generator system. I have never heard that such a thing is planned at Tesla.
way to small of a market for them to even think about something like that
 

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