Off-grid backup power using hybrid inverters?

[Not Aerosmith]

I already have (3) 5 KW Fronius grid-tie inverters with 57 solar panels that have been working flawlessly for almost 4 years. However, I live where power outages are several times a week. I want to add an ATS and backup power, but using a solar inverter with batteries not gasoline generator.

My intentions are to buy hybrid inverters not off-grid inverters. My reasoning is that hybrid inverters could replace the grid-tie inverters if it ever becomes necessary (redundancy), whereas off-grid inverters can't sell back to the grid. Over 2/3 of the power generated is stored on the grid to be used as needed when solar is not available. Most hybrid inverters only provide backup power for a critical load panel not whole house.

The new SunGoldPower IP6048 and MPP Solar LVX6048-WP indicate they can provide power for the whole house with up to 9 hybrid panels in parallel. Each hybrid inverter needs 10 KW of batteries. If this is only backup power, I can grow the system by adding a hybrid inverter with 2 batteries in stages as I feel more comfortable with them. From what I have read and seen the first shipment of MPP Solar hybrid solar inverters had lots of issues and the verdict is still out on the newly release SunGoldPower IP 6048.

I'm afraid to interface a grid-tie system that works with new technology that seems to have too many issues and could destroy what is working. I prefer to keep the two systems separate, until the new hybrid technology seem stable and reliable without so many issues. If I use an automatic transfer switch (ATS), they are separate systems. When the ATS switched to the hybrid panels, there is no grid power, so the internal ATS in the hybrid inverter will isolate the grid.

Have anyone else actually converted an existing grid-tie system by adding hybrid inverters, batteries and ATS? Do I have a viable solution for what I'm trying to do or not? I'm an engineer, but solar is not my expertise. Are there better whole house hybrid inverters than the one I listed?

 

[BentleyJ]

Since you didn't mention AC coupling (Grid Tie & Hybrid Inverters working together) in your post, Its possible you are either not aware of this configuration or have perhaps prematurely discounted it as being unreliable. MANY of us, including myself, on this forum started with Grid-Tie systems and added battery back up later using AC coupling with suitable UL1741 compliant inverters. The advantage of AC coupling is not having to make any wiring changes to the present grid-tie systems.
With AC coupling a UL1741 inverter with batteries is installed and your existing grid-tie inverters are connected to the LOAD side of the new inverter. The new inverter becomes a grid-forming inverter that supplies the frequency to keep the grid-tie inverters operating in an outage.
In addition the new hybrid battery inverter performs 2 other critical functions. 1) It has an internal transfer switch that disconnects from the grid in an outage thus eliminating the need for an external ATS (although an external ATS can be used with some inverters) 2) It uses excess grid-tie production to charge the batteries. When the batteries are full and no grid is present to absorb the excess, it will use frequency shifting to curtail the output of the grid-tie inverters.
Based on your system size you may need to stack more than one new inverter.
Check out Schneider XW Pro, Outback Mojave, Sol-Ark 15K(has a 200A transfer switch) and SMA.
With these more expensive and more sophisticated inverters it is also possible to do combination systems that are part DC coupled and part AC coupled.

 

[Ampster]

That is a great explanation of the benefits of AC coupling to take a previously installed GT system and leverage it. The concept is to add a hybrid invverter and batteries to get battery backup and still get value out of a GT system which previously would not function when the grid went down.

 

[Not Aerosmith]

Since you didn't mention AC coupling (Grid Tie & Hybrid Inverters working together) in your post, Its possible you are either not aware of this configuration or have perhaps prematurely discounted it as being unreliable. MANY of us, including myself, on this forum started with Grid-Tie systems and added battery back up later using AC coupling with suitable UL1741 compliant inverters. The advantage of AC coupling is not having to make any wiring changes to the present grid-tie systems.
With AC coupling a UL1741 inverter with batteries is installed and your existing grid-tie inverters are connected to the LOAD side of the new inverter. The new inverter becomes a grid-forming inverter that supplies the frequency to keep the grid-tie inverters operating in an outage.
In addition the new hybrid battery inverter performs 2 other critical functions. 1) It has an internal transfer switch that disconnects from the grid in an outage thus eliminating the need for an external ATS (although an external ATS can be used with some inverters) 2) It uses excess grid-tie production to charge the batteries. When the batteries are full and no grid is present to absorb the excess, it will use frequency shifting to curtail the output of the grid-tie inverters.
Based on your system size you may need to stack more than one new inverter.
Check out Schneider XW Pro, Outback Mojave, Sol-Ark 15K(has a 200A transfer switch) and SMA.
With these more expensive and more sophisticated inverters it is also possible to do combination systems that are part DC coupled and part AC coupled.

Thank you for an excellent response.

I considered Sol-Ark when I originally installed the system some 4 years ago. I ruled them out, because their system is based on a critical load panel not whole house. It seemed to me that the hybrid system with batteries would double the cost for only a critical load panel. I assumed that there would be hundreds of thousands grid-tie systems and that someone in a few years will come out with a device to convert them into a whole house hybrid system. I decided to install a more affordable grid-tie inverters system with a 7 year payback and wait on a hybrid inverter that can modify an existing system into a whole house hybrid solution.

The more expensive and more sophisticated inverters that you listed, I have not seen a schematic where they provide a whole house solution especially using existing grid-tie inverters. I agree that it is possible with frequency shifting to control their output and there is a YouTube video where this was done using a Schneider inverter, but it was a manual transfer for when the grid is down.

There is a GE inverter that is really promising, but it test market is in Australia and not split phase 120/240. Morningstar is developing a system, but it is not an all in one solution and need several expensive Schneider components to make it work . The Schneider component provides an automatic battery transfers solution and the Morningstar requires a manual transfer of the solar panels to charge the battery and it limits the solar panel production. Fronius is starting to offer a hybrid solution, but it test market is mainly in Europe. Some other big names are developing new systems, but usually only new installations and not modifying existing grid-tie systems.

SunGoldPower Blue Power IP6048 hybrid inverter have a schematic that looks promising and I have attached it. However, it is not in their installation manual and there very limited information on how it works. I'm concern about trying it. It is clear that it works when the grid is down and can provide battery backup. It is not clear that I can sell back to the grid when the grid is up. If not, in my case it does more harm than good, since I normally store 2/3 of my production on the grid to use later. It is not clear on how it controls the existing grid-tie inverters to limit their voltage and production to the actual demand needed versus maximizing production as they are design to do. I know that it can be done. I'm just not aware of any successful installations of the IP6048 or the LVX6048-WP modifying an existing system.

 

[BentleyJ]

Sounds like you have researched the market fairly well. I will leave you with a couple of additional comments that may be of some help.
1) Any hybrid inverter can be used as a whole house solution but it does require a Line Side utility tap between the meter and your main panel for AC Input to the inverter and then the inverter AC Output is used to power the entire main panel. I'm using a Schneider XW+ that powers our main 200A panel via a backfed 60A 2 pole breaker. I have also installed a maintenance bypass transfer switch such that if the inverter fails I can feed power from the meter directly into the main breaker on the main panel while the inverter can be completely isolated by turning off both the input and output breakers.
This is a new product from Siemens designed specifically for a Line Side Tap. https://connectder.com/

2) Perhaps the Franklin Whole House back up system would be of interest. I believe it is a bi-directional battery/inverter so only needs one 2 pole breaker for each unit. https://www.franklinwh.com/

 

[schmism]

most existing grid tie only systems are high voltage series arrays (up to and including 600v dc) Most hybrid inverters do not support this high a PV string voltage.
Each hybrid inverter needs its OWN string of PV panels. So if you run several inverters in parallel then you'll need to re-wire the existing PV to support the correct string voltage as well as ensuring each inverter has its own string of panels.
Only one battery bank can be used to supply all hybrid inverters if they are sharing load/in parallel.

 

[yaq]

Merci pour une excellente réponse.

J'ai pensé à Sol-Ark lorsque j'ai installé le système il y a environ 4 ans. Je les ai écartés, car leur système est basé sur un panneau de charge critique et non sur toute la maison. Il me semblait que le système hybride avec batteries doublerait le coût pour seulement un panneau de charge critique. J'ai supposé qu'il y aurait des centaines de milliers de systèmes de connexion au réseau et que quelqu'un dans quelques années sortirait un appareil pour les convertir en un système hybride pour toute la maison. J'ai décidé d'installer un système d'onduleurs réseau plus abordable avec une période de récupération de 7 ans et d'attendre un onduleur hybride capable de transformer un système existant en une solution hybride pour toute la maison.

Les onduleurs les plus chers et les plus sophistiqués que vous avez énumérés, je n'ai pas vu de schéma où ils fournissent une solution pour toute la maison, en particulier en utilisant les onduleurs réseau existants. Je suis d'accord qu'il est possible avec le décalage de fréquence de contrôler leur sortie et il y a une vidéo YouTube où cela a été fait à l'aide d'un onduleur Schneider, mais c'était un transfert manuel lorsque le réseau est en panne.

Il existe un onduleur GE qui est vraiment prometteur, mais son marché de test est en Australie et non en phase divisée 120/240. Morningstar développe un système, mais ce n'est pas une solution tout-en-un et nécessite plusieurs composants Schneider coûteux pour le faire fonctionner. Le composant Schneider fournit une solution de transferts automatiques de batterie et le Morningstar nécessite un transfert manuel des panneaux solaires pour charger la batterie et cela limite la production de panneaux solaires. Fronius commence à proposer une solution hybride, mais son marché test se situe principalement en Europe. Certains autres grands noms développent de nouveaux systèmes, mais généralement uniquement de nouvelles installations et ne modifient pas les systèmes de raccordement au réseau existants.

L'onduleur hybride SunGoldPower Blue Power IP6048 a un schéma qui semble prometteur et je l'ai joint. Cependant, ce n'est pas dans leur manuel d'installation et il y a très peu d'informations sur son fonctionnement. J'ai peur de l'essayer. Il est clair qu'il fonctionne lorsque le réseau est en panne et peut fournir une batterie de secours. Il n'est pas clair que je puisse revendre au réseau lorsque le réseau est en place. Sinon, dans mon cas ça fait plus de mal que de bien, puisque je stocke normalement 2/3 de ma production sur le réseau pour l'utiliser plus tard. On ne sait pas comment il contrôle les onduleurs réseau existants pour limiter leur tension et leur production à la demande réelle nécessaire par rapport à la maximisation de la production comme ils sont conçus pour le faire. Je sais que cela peut être fait. Je ne suis tout simplement pas au courant d'installations réussies de l'IP6048 ou du LVX6048-WP modifiant un système existant.

 

[yaq]

:

Thank you for an excellent response.

I considered Sol-Ark when I originally installed the system some 4 years ago. I ruled them out, because their system is based on a critical load panel not whole house. It seemed to me that the hybrid system with batteries would double the cost for only a critical load panel. I assumed that there would be hundreds of thousands grid-tie systems and that someone in a few years will come out with a device to convert them into a whole house hybrid system. I decided to install a more affordable grid-tie inverters system with a 7 year payback and wait on a hybrid inverter that can modify an existing system into a whole house hybrid solution.

The more expensive and more sophisticated inverters that you listed, I have not seen a schematic where they provide a whole house solution especially using existing grid-tie inverters. I agree that it is possible with frequency shifting to control their output and there is a YouTube video where this was done using a Schneider inverter, but it was a manual transfer for when the grid is down.

There is a GE inverter that is really promising, but it test market is in Australia and not split phase 120/240. Morningstar is developing a system, but it is not an all in one solution and need several expensive Schneider components to make it work . The Schneider component provides an automatic battery transfers solution and the Morningstar requires a manual transfer of the solar panels to charge the battery and it limits the solar panel production. Fronius is starting to offer a hybrid solution, but it test market is mainly in Europe. Some other big names are developing new systems, but usually only new installations and not modifying existing grid-tie systems.

SunGoldPower Blue Power IP6048 hybrid inverter have a schematic that looks promising and I have attached it. However, it is not in their installation manual and there very limited information on how it works. I'm concern about trying it. It is clear that it works when the grid is down and can provide battery backup. It is not clear that I can sell back to the grid when the grid is up. If not, in my case it does more harm than good, since I normally store 2/3 of my production on the grid to use later. It is not clear on how it controls the existing grid-tie inverters to limit their voltage and production to the actual demand needed versus maximizing production as they are design to do. I know that it can be done. I'm just not aware of any successful installations of the IP6048 or the LVX6048-WP modifying an existing system.

"Hi, Does anyone have an off grid workshop? What 3 phase inverters are you using? I have 3 Victron Multiplus 24/5000 inverters but I'm wondering if there is a better way to configure things (I haven't even unpacked them yet so I can resell them without any problems). "

:
Next3 from Studer

15kW three phase

COV PV 900V!!!

but in 48V (~ 40 - 68V)

2MPPT 2+2

All in one, with grid input, a generator, etc.

In my opinion, this is the top of the line in terms of multimode inverter technology.

One device!

It is worth the price if we calculate that with the same power and modalities we need 5 devices like Victron or SMA.

The robustness of Studer is not to be boasted anymore, their specialty has always been the installations "at the end of the world"!

There are also American versions.

If you have an existing inverter(s) you can connect it/them to the "generators, etc." input.

 

[wattmatters]

Have anyone else actually converted an existing grid-tie system by adding hybrid inverters, batteries and ATS?

There are tens of thousands of Tesla Powerwall 2s (+Gateway) in operation in Australia which do just this. It's just an AC coupled storage system, and you can build similar with a suitable inverter which can form its own grid and take control of grid following inverters such as your Fronius units (using grid frequency control).

Else you can replace one of your Fronius inverters for a Fronius Hybrid and add a battery to it.

 

[Not Aerosmith]

most existing grid tie only systems are high voltage series arrays (up to and including 600v dc) Most hybrid inverters do not support this high a PV string voltage.
Each hybrid inverter needs its OWN string of PV panels. So if you run several inverters in parallel then you'll need to re-wire the existing PV to support the correct string voltage as well as ensuring each inverter has its own string of panels.
Only one battery bank can be used to supply all hybrid inverters if they are sharing load/in parallel.

Your are right most hybrid inverters were low voltages with only a few at 450 volts. My operating voltage is 420 volts and my grid-tie inverters were rated to 600 volts, so I felt uncomfortable with most hybrid inverters last year. This year new inverters have increased their voltage to 550-600 volts, so I´m now feel more comfortable in adding a new hybrid inverter.

 

[Not Aerosmith]

There are tens of thousands of Tesla Powerwall 2s (+Gateway) in operation in Australia which do just this. It's just an AC coupled storage system, and you can build similar with a suitable inverter which can form its own grid and take control of grid following inverters such as your Fronius units (using grid frequency control).

Else you can replace one of your Fronius inverters for a Fronius Hybrid and add a battery to it.

Everything that you said is true. Unfortunately, Panama where I live ... use the same split phase 120/240 volts as the USA. Australia and Europe inverters are not designed for the USA market. Yes, Fronius has a new Hybrid invereter but not release yet for the USA market. My supplier/installer of my existing system is a Fronius authorized dealer, and he knows that I trying to upgrade my existing system to work when the power is down in Panama. So far, he has been unable to offer a whole house solution at a reasonable cost.

 

[Not Aerosmith]

:


"Hi, Does anyone have an off grid workshop? What 3 phase inverters are you using? I have 3 Victron Multiplus 24/5000 inverters but I'm wondering if there is a better way to configure things (I haven't even unpacked them yet so I can resell them without any problems). "

:
Next3 from Studer

15kW three phase

COV PV 900V!!!

but in 48V (~ 40 - 68V)

2MPPT 2+2

All in one, with grid input, a generator, etc.

In my opinion, this is the top of the line in terms of multimode inverter technology.

One device!

It is worth the price if we calculate that with the same power and modalities we need 5 devices like Victron or SMA.

The robustness of Studer is not to be boasted anymore, their specialty has always been the installations "at the end of the world"!

There are also American versions.

If you have an existing inverter(s) you can connect it/them to the "generators, etc." input.

My system is a residential application in Panama, which use split phase 120/240 volts single phase not 3 phase. I was not aware that Studer is 900 volts, which is good information to know when trying to find the right hybrid inverter.

 

[Ampster]

This year new inverters have increased their voltage to 550-600 volts, so I´m now feel more comfortable in adding a new hybrid inverter.

Outback has a couple of hybrids that can handle 600 volt solar strings. They still use nominal 48 Volt batteries.

 

[Not Aerosmith]

Sounds like you have researched the market fairly well. I will leave you with a couple of additional comments that may be of some help.
1) Any hybrid inverter can be used as a whole house solution but it does require a Line Side utility tap between the meter and your main panel for AC Input to the inverter and then the inverter AC Output is used to power the entire main panel. I'm using a Schneider XW+ that powers our main 200A panel via a backfed 60A 2 pole breaker. I have also installed a maintenance bypass transfer switch such that if the inverter fails I can feed power from the meter directly into the main breaker on the main panel while the inverter can be completely isolated by turning off both the input and output breakers.
This is a new product from Siemens designed specifically for a Line Side Tap. https://connectder.com/

2) Perhaps the Franklin Whole House back up system would be of interest. I believe it is a bi-directional battery/inverter so only needs one 2 pole breaker for each unit. https://www.franklinwh.com

 

[Sanwizard]

Thank you for an excellent response.

I considered Sol-Ark when I originally installed the system some 4 years ago. I ruled them out, because their system is based on a critical load panel not whole house. It seemed to me that the hybrid system with batteries would double the cost for only a critical load panel. I assumed that there would be hundreds of thousands grid-tie systems and that someone in a few years will come out with a device to convert them into a whole house hybrid system. I decided to install a more affordable grid-tie inverters system with a 7 year payback and wait on a hybrid inverter that can modify an existing system into a whole house hybrid solution.

The more expensive and more sophisticated inverters that you listed, I have not seen a schematic where they provide a whole house solution especially using existing grid-tie inverters. I agree that it is possible with frequency shifting to control their output and there is a YouTube video where this was done using a Schneider inverter, but it was a manual transfer for when the grid is down.

There is a GE inverter that is really promising, but it test market is in Australia and not split phase 120/240. Morningstar is developing a system, but it is not an all in one solution and need several expensive Schneider components to make it work . The Schneider component provides an automatic battery transfers solution and the Morningstar requires a manual transfer of the solar panels to charge the battery and it limits the solar panel production. Fronius is starting to offer a hybrid solution, but it test market is mainly in Europe. Some other big names are developing new systems, but usually only new installations and not modifying existing grid-tie systems.

SunGoldPower Blue Power IP6048 hybrid inverter have a schematic that looks promising and I have attached it. However, it is not in their installation manual and there very limited information on how it works. I'm concern about trying it. It is clear that it works when the grid is down and can provide battery backup. It is not clear that I can sell back to the grid when the grid is up. If not, in my case it does more harm than good, since I normally store 2/3 of my production on the grid to use later. It is not clear on how it controls the existing grid-tie inverters to limit their voltage and production to the actual demand needed versus maximizing production as they are design to do. I know that it can be done. I'm just not aware of any successful installations of the IP6048 or the LVX6048-WP modifying an existing system.

VERY interesting topic! I am struggling with the same concepts. I already own two LVX7048WP's and 70KW of DIY LiFePo4, and am searching for a schematic to connect to the two existing grid tied SMA inverters. Sharing the existing PV is another quandry.

 

[PuraVidaPrepping]

I am in Costa Rica, same power system as Panama, same frequent interruptions! I've installed many of the Sol-Arks (or equivalent Deye based inverters) to run the whole panel, not just critical load. This does depend what your peak load would be, particularly in an outage where the inverter has to cover the total load.
New units from Sol-Ark (15k) and GSL 12k can handle 12,000 Watts off grid from single inverter, and each have 3 PV inputs, 500vdc PV input (550 volt max VOC), integrated transfer and AC coupling functionality. If your whole panel peak load stays under 12,000 Watts, it seems like one unit could do all this for you.

 

[Not Aerosmith]

VERY interesting topic! I am struggling with the same concepts. I already own two LVX7048WP's and 70KW of DIY LiFePo4, and am searching for a schematic to connect to the two existing grid tied SMA inverters. Sharing the existing PV is another quandry.

I Google LVX7048WP and didn't find anything. However, SMA Sunny Boy has a 7000 GT inverter, which are UL1741 listed and can be AC couple. If this is your situation, there are options. You should verify your original SMA specifications about UL1741.

I have a similar situation with 15 KW of existing GT inverters and my solution is to use (2) GSL-H-12KLV-US hybrid inverters.

In your case, you can simply AC couple one SMA to each GSL and it should operate the same as it does now, accept upon loss of power, you have up to 24,000 off grid power between your solar panels and batteries. You will have your total existing 14 KW inverter capacity and a 200A bypass when there is no power outage, which is 99% of the time. Each inverter can handle 12,000 watts 240V 50A, so with two GSL you have more off grid capacity at 24,000 watts. The new GSL hybrid inverters are around $3.2K each plus shipping and customs duty, so (2) GSL have more capacity than one Sol-Ark 15K for about the same cost.

I envy your 70 KW of batteries, I have none.

 

[Sanwizard]

I Google LVX7048WP and didn't find anything. However, SMA Sunny Boy has a 7000 GT inverter, which are UL1741 listed and can be AC couple. If this is your situation, there are options. You should verify your original SMA specifications about UL1741.

I have a similar situation with 15 KW of existing GT inverters and my solution is to use (2) GSL-H-12KLV-US hybrid inverters.

In your case, you can simply AC couple one SMA to each GSL and it should operate the same as it does now, accept upon loss of power, you have up to 24,000 off grid power between your solar panels and batteries. You will have your total existing 14 KW inverter capacity and a 200A bypass when there is no power outage, which is 99% of the time. Each inverter can handle 12,000 watts 240V 50A, so with two GSL you have more off grid capacity at 24,000 watts. The new GSL hybrid inverters are around $3.2K each plus shipping and customs duty, so (2) GSL have more capacity than one Sol-Ark 15K for about the same cost.

I envy your 70 KW of batteries, I have none.

Sorry about the typo. I meant to type LVX6048WP. I appreciate the tip on the GSL inverters.

 

[Not Aerosmith]

I am in Costa Rica, same power system as Panama, same frequent interruptions! I've installed many of the Sol-Arks (or equivalent Deye based inverters) to run the whole panel, not just critical load. This does depend what your peak load would be, particularly in an outage where the inverter has to cover the total load.
New units from Sol-Ark (15k) and GSL 12k can handle 12,000 Watts off grid from single inverter, and each have 3 PV inputs, 500vdc PV input (550 volt max VOC), integrated transfer and AC coupling functionality. If your whole panel peak load stays under 12,000 Watts, it seems like one unit could do all this for you.

My load doesn't stay under 12,000 watts, which is only 240 50A, which is not much for a whole backup. I feel more comfortable with (2) 12 KW GSL hybrid inverters for about the same price as one 15KW SA hybrid inverter. I have also decided to add another 12 KW solar panels to my existing 18.81 KW solar panels for about 30 KW total.

 

[Not Aerosmith]

Sorry about the typo. I meant to type LVX6048WP. I appreciate the tip on the GSL inverters.

You only need one GSL-H-12KLV-US hybrid inverter and simply AC couple both existing GT inverters to it. Your existing GT inverters should function the same through the hybrid inverter as it does now. The 200A bypass should prevent nuisance tripping when there is no power outage. Upon loss of power, you will have your full 12 KW of solar capacity as backup power for the house and to charge your batteries.

With one GSL hybrid inverter, your off-grid capacity is 240V 50A, which is the inverter rating. The 70 KW of batteries will extend how long you have power off-grid, but will not increase the hybrid inverter maximum output of 240V 50A.