on grid, but want off grid capability?

[SunEagle]

so let me ask you this, if grid is out, i could in theory hook up a generator in place of the grid and the GT solar array would kick in?

Unfortunately a generator will not simulate the grid functions to allow your inverter to work.

[mudhole]

Ya, I guess I wasnt thinking about the excess power created by the GT, it now makes perfect sense. I guess for my situation, the hybrid inverter would be the "best" way to go if I wanted that functionality.

[PVAndy]

One Tesla Powerwall would satisfy your needs It also requires a Tesla Gateway

[Ampster]

One Tesla Powerwall would satisfy your needs It also requires a Tesla Gateway

Lots of users have installed Powerwalls to leverage their GT systems and provide backup. It uses the AC coupling to do that and the Tesla Gateway functions as an ATS but there is no provision for a generator. I had two Powerwalls on order but concluded I only needed the inverter capacity of one but wanted the battery capacity of three. I went with a hybrid and DIY battery pack. As far as I can tell I have the same functionality in my grid interactive mode. I am not sure how mudhole defines "off grid capability". Some Powerwall users have reported that since the Powerwall was designed to be grid interactive it does not function well as an off grid inverter, The lack of generator input is one of those functions that it does not have.

[littleharbor2]

Tesla was supposed to come out with a off grid version but for whatever reason decided to not bring it out. The off grid version was supposed to have lower input voltage inherent to off grid systems. The version they currently market has a high DC input voltage more inline with Grid Tie systems.

[Ampster]

Tesla was supposed to come out with a off grid version but for whatever reason decided to not bring it out. The off grid version was supposed to have lower input voltage inherent to off grid systems. The version they currently market has a high DC input voltage more inline with Grid Tie systems.

I do not know what the internal DC voltage is because the battery and inverter are all in the same package. I would not be surprised if it was higher than 48 volts because they are used to dealing with higher voltage in the cars. The Gateway is separate and that is what manages the AC coupling. They do not have separate inputs for solar or generators so all they can do is AC couple, That does make them a useful addition to an modern GT system for someone who wants battery backup. A dealer I know in Southern California is no longer doing just solar installs. He has enough business backlog that he can pick only solar and Powerwalls. The same can be said for Tesla, they now only do solar with Powerwalls.

[solarix]

No, No, No, you can not run a GT inverter on anything except the grid. The inverter not only needs an AC waveform to synchronize to - it also needs a close to infinite load to dump the solar power into. It will not run on a generator, it will not run on itself. However, SMA does make an "Island" inverter that is designed to create a little grid that the GT inverter can work off of, but it needs big batteries to absorb any or all of the power the GT inverter is producing.

[PVAndy]

No, No, No, you can not run a GT inverter on anything except the grid. The inverter not only needs an AC waveform to synchronize to - it also needs a close to infinite load to dump the solar power into. It will not run on a generator, it will not run on itself. However, SMA does make an "Island" inverter that is designed to create a little grid that the GT inverter can work off of, but it needs big batteries to absorb any or all of the power the GT inverter is producing.

Are you saying that you can't use a Powerwall with a grid interactive SMA inverter/ That is not the case. When the Powerwall forms the microgrid and enables the SMA inverter, any solar power not used by the premise loads charges the battery. If the battery is fully charged the Powerwall changes the microgrid frequency and trips the inverter

Andy

[peakbagger]

No, No, No, you can not run a GT inverter on anything except the grid. The inverter not only needs an AC waveform to synchronize to - it also needs a close to infinite load to dump the solar power into. It will not run on a generator, it will not run on itself. However, SMA does make an "Island" inverter that is designed to create a little grid that the GT inverter can work off of, but it needs big batteries to absorb any or all of the power the GT inverter is producing.

I have a Sunny Island setup and three other grid tied arrays, when I switch to off grid operation, the other grid tied inverters, (two Fronius and 4 Enphase 215s) wait 5 minutes and start producing into the microgrid.. I had enough house loads running that I was not net surplus but with their frequency shifting approach I have no doubt the other inverters will shut down. There are two very large forklift batteries in the loop so no problem with absorbing excess power.

[nerdralph]

I just had another idea, is there just a way to trick my grid tie sunnyboy to not shut down due to grid being down? and then hook up UPS between whatever I want to run?

Yes. Switch the main breaker off to disconnect from the grid. Then connect your UPS (or genset) to the main panel.

[Ampster]

Yes. Switch the main breaker off to disconnect from the grid. Then connect your UPS (or genset) to the main panel.

That will definitely power loads, but most likely will not pass the test a typical GT inverter goes through to verify it is seeing a real grid or a hybrid inverter that is designed and configured for AC coupling. Have you actually done that without smoke being released from the UPS? Since a GT inverter is designed to output all of the solar to the grid, what is your experience with a genset or UPS being able to absorb all that energy?

[Ampster]

No, No, No, you can not run a GT inverter on anything except the grid. .......

I respect your opinion but the Powerwall was designed to AC couple with GT inverters and does it for hundreds of thousand users. My Outback Skybox is AC coupled with 6kW of micros. I believe AC coupling is the exception to your statement but many users will think, incorrectly, that it is as simple as giving the GT inverter a 60 Hz signal. They ignore the physics and serious things can happen.

[nerdralph]

That will definitely power loads, but most likely will not pass the test a typical GT inverter goes through to verify it is seeing a real grid or a hybrid inverter that is designed and configured for AC coupling. Have you actually done that without smoke being released from the UPS? Since a GT inverter is designed to output all of the solar to the grid, what is your experience with a genset or UPS being able to absorb all that energy?

Grid-tie inverters have an upper voltage safety limit beyond which it cuts back on the power from the array by increasing the MPPT voltage. With my Solis 240V inverter the specs state the maximum output is 264V.

[Ampster]

Grid-tie inverters have an upper voltage safety limit beyond which it cuts back on the power from the array by increasing the MPPT voltage. With my Solis 240V inverter the specs state the maximum output is 264V.

GT inverters complying with UL 1751SA also have frequency Watt modulation. I do not know of any gensets of UPSs that are designed to do that like hybrid inverters do with AC coupling.

So, back to my question about your experience hooking up a UPS or Genset to a GT inverter? How long did it take before the smoke came out? Are you trying to imply that the voltage limit of a GT inverter will prevent it or the Genset from damage? A lot of things can happen between 240 volts and 263 volts and a lot of Amps can flow. Are you ignoring the important fact that a GT inverter is only limited by the solar generation which has no relationship to the load. In the case of the grid, which presents an infinite load that is not an issue. A genset or UPS has no mechanism to buffer the output of the GT inverter.

[bcroe]

Grid-tie inverters have an upper voltage safety limit beyond which it cuts back on the power from the array by increasing the MPPT voltage. With my Solis 240V inverter the specs state the maximum output is 264V.

Yes 264V seems to be the standard cutoff. Was it supposed to protect against
some of the illegal type connections mentioned above? Maybe, the GT inverter
certainly is not going to much change the line voltage. It will be, regardless.

So someone said lets put an upper voltage cutoff in, but what? Line here should
not exceed 120/240VAC, so a 264V limit should be OK. EXCEPT, the PoCo likes
to run as high as they can, voltage here was running 127/254VAC. That voltage
can be expected to rise slightly as the GT pushes power out. Add here a long
run of adequate but somewhat lossy feed, pick up another 9V. That puts things
pretty much at 264V, though there is no danger to anything.

My GTs were capable of 277VAC operation, I bumped up the monitor to that limit
to stay operational. In the long term, I got the PoCo to lower their voltage, and I
installed a much bigger feed to eliminate most of the 9V increase. Bruce Roe