Fooling a grid-tie inverter to provide power without grid.

[robby]

Sol-Ark appears to use switch for GTI control which I explained previously so it's different from typical hybrid inverters that use frequency shift to turn off GTI. Assuming you properly configure the AC coupling settings in Sol-Ark then you don't need to worry about excess GTI power when batteries are full. Basically, Sol-Ark monitors the battery bank SOC and when it's near full it will turn off GTI via the built-in switch to GTI and continue to power loads from the battery bank. When SOC is low enough then the GTI switch will turn on again. I personally like the switch method of GTI control so I don't have to worry about potential problems with frequency shifted power with the devices/appliances I have now or purchase in the future. In general, few electronic devices/appliances are designed and tested to work properly with power frequency outside of the normal grid frequency range.

This now makes sense to me. But i wonder why they say you can use it as a Grid Tie Inverter without batteries and add them later?

 

[solar8484]

This now makes sense to me. But i wonder why they say you can use it as a Grid Tie Inverter without batteries and add them later?

That depends on the specific inverter. Some newer hybrid inverters can effectively switch between grid-tied and off-grid mode so when they detect there is grid it operates in grid-tied mode (i.e. current source pumping out as much power as possible) but when there is no grid the inverter switches over to off-grid mode (i.e. voltage source pumping out only as much power as demanded) that is capable of running only with solar power input. Sunny Boy SPS is one example. It's nice conceptually but solar is an intermittent energy source so it's not so practical if you need some fixed minimum power to run your loads consistently. Just imagine what happens to your loads with variable clouds and passing birds. So, given the appropriate inverter, you can run it with only solar but practically you also need a more consistent energy source in the system like batteries.

If you are talking about Sol-Ark specifically, I think it just means you can use it as GTI connected to the grid without batteries which is true for all GTI. I don't know if Sol-Ark can run in off-grid mode with only DC coupled solar input.

 

[robby]

That depends on the specific inverter. Some newer hybrid inverters can effectively switch between grid-tied and off-grid mode so when they detect there is grid it operates in grid-tied mode (i.e. current source pumping out as much power as possible) but when there is no grid the inverter switches over to off-grid mode (i.e. voltage source pumping out only as much power as demanded) that is capable of running only with solar power input. Sunny Boy SPS is one example. It's nice conceptually but solar is an intermittent energy source so it's not so practical if you need some fixed minimum power to run your loads consistently. Just imagine what happens to your loads with variable clouds and passing birds. So, given the appropriate inverter, you can run it with only solar but practically you also need a more consistent energy source in the system like batteries.

If you are talking about Sol-Ark specifically, I think it just means you can use it as GTI connected to the grid without batteries which is true for all GTI. I don't know if Sol-Ark can run in off-grid mode with only DC coupled solar input.

I think they carry it one step further and can utilize the GTI and the Batteries. I have seen videos showing house consumption at something like 7KW and you see 5KW being pulled from the PV and the other 2KW coming from the batteries. I was really hoping to achieve this same kind of setup with SMA products, even bought a 5KW Sunny Boy and had to return it. The setup became so complicated and expensive that I got completely turned off. Finding Sol-Ark was wonderfull, they had really built a Hybrid system based on what someone in my position would be looking for.

 

[solar8484]

I think they carry it one step further and can utilize the GTI and the Batteries. I have seen videos showing house consumption at something like 7KW and you see 5KW being pulled from the PV and the other 2KW coming from the batteries. I was really hoping to achieve this same kind of setup with SMA products, even bought a 5KW Sunny Boy and had to return it. The setup became so complicated and expensive that I got completely turned off. Finding Sol-Ark was wonderfull, they had really built a Hybrid system based on what someone in my position would be looking for.

Why couldn't you do that with Sunny Boy? Seems likely it could be adding a solar charge controller for the DC coupled solar panels. However, I agree that Sol-Ark is more convenient with more integrated components.

 

[robby]

Why couldn't you do that with Sunny Boy? Seems likely it could be adding a solar charge controller for the DC coupled solar panels. However, I agree that Sol-Ark is more convenient with more integrated components.

Because SMA and their installers have a specific way that they want it to be installed if you want to get warranty service and I also presume it's needed for passing inspection. They call it a Flexible power solution and in the case of the USA you would need at least one Sunny Boy and Two Sunny islands plus a $1200 Enwitec Autotransfer switch box with all sorts of breakers in it. In my case I need One Sunny Boy UK version and One Sunny Island 8.0H UK version plus the Ewtitec and two Victron 100A Autotranformers. Any way you slice it the system cost and complexity are mind blowing.

Here are the Approved SMA instructions:
https://zerohomebills.com/wp-conten...-Manual-on-zerohomebills.com-by-solaranna.pdf

I see a simpler solution to this, but it does not matter as I need the warranty and Inspection pass.

 

[solar8484]

Because SMA and their installers have a specific way that they want it to be installed if you want to get warranty service and I also presume it's needed for passing inspection. They call it a Flexible power solution and in the case of the USA you would need at least one Sunny Boy and Two Sunny islands plus a $1200 Enwitec Autotransfer switch box with all sorts of breakers in it. In my case I need One Sunny Boy UK version and One Sunny Island 8.0H UK version plus the Ewtitec and two Victron 100A Autotranformers. Any way you slice it the system cost and complexity are mind blowing.

Here are the Approved SMA instructions:
https://zerohomebills.com/wp-conten...-Manual-on-zerohomebills.com-by-solaranna.pdf

I see a simpler solution to this, but it does not matter as I need the warranty and Inspection pass.

That looks over-engineered. You made the right decision to return the Sunny Boy.

 

[robby]

That looks over-engineered. You made the right decision to return the Sunny Boy.

I think SMA has fallen behind the times. I think they still have some of the best equipment but they do not have an all in one Hybrid solution. I guess that up to a year or two ago there was not really a big enough market of people who wanted PV with batteries, but there was a market for battery backup alone. I guess they thought they could just put the two solutions together and call it a day for a Hybrid solution. Fast forward to 2021 and everyone else has a much more compact Hybrid inverter that does what their more elaborate and expensive system does. SMA really needs to get up to speed because battery prices are dropping so fast that it makes Hybrids very attractive to consumers.

On a side note it's going to become even more insane as more Hybrid and Electric vehicles get scraped and those used battery modules drop in price even further. If solid State batteries do materialize it gets even more interesting.

 

[prolecs]

This is mostly too complex for me to handle. I was looking for some way to use an old inverter and panels, off grid, for hot water heating, either pool or HWS. The number of PV panels could be set/switched to suit fixed size element, or disconnected when up to temperature. But how to trick the inverter SIMPLY??