Grid Goes down; Multiple Inverters; Combine SPS into transfer switch

[SoftwareDude]

Hi everyone, I am new here. I live out here in Texas where the winter storm knocked out my power for a couple of days. I have been, and am very, interested in putting solar up. I've been doing my homework but I cannot find the answer to a particular question that I have and was hoping someone here could help me.

Root of my question: If my grid-tied system goes down, how can I keep (some of) the power (legally) going to my house WITHOUT batteries. (Keep reading)

I know why grid-tied string inverters shut down when the grid goes down so there is no need to discuss that. However, I do know that some inverters, like the SMA Sunny Boy, have an SPS (Secure Power Supply) that allows 2000 watts of energy to be routed to an outlet in the event that the grid goes down. So here is my 2nd question...

Question: Assume I have 5x SMA Sunny Boy Inverters and I am in full sun with > 2000 watts going to each inverter. Now the grid goes down. Can I wire up my 5x inverters into an AC combiner box such that the output of the combiner box is a 240v plug @ 10,000 watts of power? If this is the case then I should be able to now plug this 240v cable into my transfer switch and be running on solar power when the grid is down. Much like a generator except I am using the SPS`. They would all be in the same phase with the same voltage turned on/off at the same time by the same mechanism. Is it possible and legal to create a setup like this?

Thanks everyone!

[solarix]

Simple answer - NO. The SunnyBoys do not sync the SPS output like it does when in grid-tie mode and there is no way to synchronize the five SPS outputs. Best you can do is divide your loads up and have five separate transfer switches.

[SunEagle]

I agree with solarix. Most inverters will not sync up and provide the same frequency and voltage that a grid will so connecting them to the same panel is not going to work. Each of the inverters should be able to provide power to a separate load as long as the sun doesn't change in strength and the AC load can handle slight fluctuations. Remember the secure power supply is still dependent on the proper amount of sunlight hitting the panel.

[bcroe]

Actually managing real time use of solar generated power remains a frustrating
problem, which makes net metering so attractive. The power back up of choice
here, after many decades, remains a gen set, sized to needs and best fuel choice.
Bruce Roe

[reader2580]

The Enphase IQ8 microinverter is supposed to provide power even if the grid goes down. Enphase has not yet released the IQ8 and I wouldn't trust anything I hear about it until it is actually released. There are some rumors now that it might require a battery to supply power when the grid is down. The IQ8 is now a full two years late based on the original release date Enphase gave. Obviously, no solar system produces power at night without batteries.

I would expect that most Texas generator and solar contractors are booked up for most of 2021 already. Backup generators will be backordered for months as suppliers don't make enough to handle a surge of orders that is tens or hundreds of thousands in a short period.

[solardreamer]

Hi everyone, I am new here. I live out here in Texas where the winter storm knocked out my power for a couple of days. I have been, and am very, interested in putting solar up. I've been doing my homework but I cannot find the answer to a particular question that I have and was hoping someone here could help me.

Root of my question: If my grid-tied system goes down, how can I keep (some of) the power (legally) going to my house WITHOUT batteries. (Keep reading)

I know why grid-tied string inverters shut down when the grid goes down so there is no need to discuss that. However, I do know that some inverters, like the SMA Sunny Boy, have an SPS (Secure Power Supply) that allows 2000 watts of energy to be routed to an outlet in the event that the grid goes down. So here is my 2nd question...

Question: Assume I have 5x SMA Sunny Boy Inverters and I am in full sun with > 2000 watts going to each inverter. Now the grid goes down. Can I wire up my 5x inverters into an AC combiner box such that the output of the combiner box is a 240v plug @ 10,000 watts of power? If this is the case then I should be able to now plug this 240v cable into my transfer switch and be running on solar power when the grid is down. Much like a generator except I am using the SPS`. They would all be in the same phase with the same voltage turned on/off at the same time by the same mechanism. Is it possible and legal to create a setup like this?

Thanks everyone!

As others have pointed out it's not possible to parallel SPS as it doesn't sync its output waveform. If a single SPS power is not enough for you then you may consider SolarCity/Delta H6 which can provide more power without battery. However, keep in mind, solar is an unreliable and intermittent power source so your loads may not like potentially frequent power cycling as clouds/birds pass by. For reliable on-demand emergency backup power, you should always have a generator even if you have solar/battery system.

[Ampster]

The only inverter I know of that can provide power without batteries is that SPS example. Batteries are needed in a hybrid inverter for the hybrid to AC couple with and control GT inverter when grid is down.

[peakbagger]

A solar city H6 requires a no longer available Tesla battery to work off grid correctly.

[SoftwareDude]

Thanks for all of the feedback so far everyone.

[solardreamer]

H6 running without battery

https://www.youtube.com/watch?v=o2vMl7fnfRg&list=WL&index=24

[Ampster]

H6 running without battery

I have seen that video. Anything is possible on Youtube. It is an interesting science experiment and I am surprised it has only received 100 views considering how many schemes go viral on Youtube. It is not sustainable because the H6 is a dead end inverter with no support. That video does nothing to address the complexities of powering an electrical device with solar. I have reach that conclusion after many hours of watching Youtube videos.

[khanh dam]

SunnyBoy seems to be discontinuing support for their SPS technology. They no longer sell optimizers or RSM that work with it. Rumor has it that Tigo RSM still work, but have not tried it personally. Which means if you really 100% want that feature you better build a pergola and therefore not need to use optimizers or RSM because that is the only sure fire way it will work.

[SoftwareDude]

Thanks for the responses everyone. Here is something that is a little bit confusing to me.

What is the difference between:
A) 5x split phase 240v AC output inverters wired into a combiner box then out to the load.
B) 5x 240v AC output SPS' wired into a combiner box then out to the load.

I can't find a good reason why A would work but B would not work. Thoughts?

[oregon_phil]

SunnyBoy seems to be discontinuing support for their SPS technology. They no longer sell optimizers or RSM that work with it. Rumor has it that Tigo RSM still work, but have not tried it personally. Which means if you really 100% want that feature you better build a pergola and therefore not need to use optimizers or RSM because that is the only sure fire way it will work.

The key phrase from SMA is "secure power supply will not work with SunSpec Rapid Shutdown devices". SMA now only promotes SunSpec Rapid Shutdown devices on their website. I have verified TS4-R-O modules do work with SPS, but they have been obsoleted by Tigo. The newer TS4-A modules are rumored not to work with SPS. There was a guy on this forum a couple years ago that used TS4-F rapid shutdown modules with SPS successfully that required a work around to power the RSS transmitter when the power was down.

It seems like a lot of work for TIGO to keep validating whether or not their modules work with SMA SPS functionality so I would expect TIGO to stop this work for new inverters.

Thanks for the responses everyone. Here is something that is a little bit confusing to me.

What is the difference between:
A) 5x split phase 240v AC output inverters wired into a combiner box then out to the load.
B) 5x 240v AC output SPS' wired into a combiner box then out to the load.

I can't find a good reason why A would work but B would not work. Thoughts?

SoftwareDude, can you explain your reasoning behind your last statement? Choices aren't always If A then B. Why do you think scenario A would work?

[SoftwareDude]

The key phrase from SMA is "secure power supply will not work with SunSpec Rapid Shutdown devices". SMA now only promotes SunSpec Rapid Shutdown devices on their website. I have verified TS4-R-O modules do work with SPS, but they have been obsoleted by Tigo. The newer TS4-A modules are rumored not to work with SPS. There was a guy on this forum a couple years ago that used TS4-F rapid shutdown modules with SPS successfully that required a work around to power the RSS transmitter when the power was down.

It seems like a lot of work for TIGO to keep validating whether or not their modules work with SMA SPS functionality so I would expect TIGO to stop this work for new inverters.



SoftwareDude, can you explain your reasoning behind your last statement? Choices aren't always If A then B. Why do you think scenario A would work?

Sure. It really just comes back to my original question about running multiple SPS power supplies in parallel.

Let's say that I have 5 inverters that have Secure Power Supplies (SPS) on each one of them. Let's say that all 5 of these SPS' are all split phase 240v. The SPS' will not be active (hot) until the grid goes down due to inverter shutting off power to grid and routing power to the SPS. So when the grid goes down, all 5 of the SPS' will go hot and start pushing 240v. At that same time that the grid goes down, and the inverters route power to their respective SPS, what is preventing me from running all 5 SPS' into a combiner box (in parallel) and outputting 240v to let's say a transfer switch?

Thanks again.