is it Ok to use on grid solar inverter with out net-meter/exporting electricity to the utility grid

[Muhammad Ahmed]

Dear experts, i want to install a 5 kVA ongrid inverter in a factory for lights that runs 24/7 but i donot want to export electricity to the grid .

Topology that i wish to use is shown as a hand made diagram that you can find in attachment with this message. Currently the lights are running on utility supply which is coming from Distribution Board (DB). Before DB there is Sub Main Panel Boards, Main Panel Boards, ATS panels and tranformer of factory and all other load is running on the system. After the installation of solar system, solar inverter will share its output on the common bus bar of lights distribution board as shown in the diagram. Blended power from solar and utility will be used to run the load. i would like to ask if ordinary On-grid inverters like inverters of Voltronics,  Solis, Chint, SAJ power, etc are Ok to use or is there some special inverter that has to be used ? I have read termnology somewhere "REVERSE FEED STOP". Is this some kind of device or it is type of inverter used to prevent supplying back to the grid ? Need your guidance as i am worried and dont want to land in a difficult situation. TIA

M.Ahmed

[Youda]

Hi @Muhammad Ahmed

yes, you can use so call "Grid Tie" mode that's available on some inverters. InfiniSolar 5K and 10K 3P can do this for sure, but both of these are a bit pricey.
You have to configure InfiniSolar to Grid Tie or Grid Tie with battery and then put the loads behind the inverter. In the settings you have to disable "feed to grid" option. It will blend the PV + grid together while trying not to feed the grid.

As a cheaper option, there are some grid-tie inverters with limiter available on the ebay. These are super-cheap and you can put more of them on a single phase in order to scale the power. The enclosed CT clamp is used to limit the feed-in to the grid.

Just beware that technically there's nothing like OnGrid, Grid-Tie or Hybrid inverter that can 100% guarantee that there will be zero feed-in to the grid. All these inverters are just trying to chase the zero. Therefore, there might be some occasional feed-in spikes, despite the hardware you will use. As a counter-measure it's a good practice to put some other load between the grid meter and the inverter. In that case, all the spikes will be consumed by that load. Other way to avoid feed-in is calibrate the inverter in a way that the system always pulls at least 50-100W from the grid, even if it's super-sunny.

 

 

 

[GreenFields]

I am assuming this will be an authorised installation, not an illegal connection to the grid.

[Elbow]

On 2019/12/04 at 6:20 PM, Youda said:

Other way to avoid feed-in is calibrate the inverter in a way that the system always pulls at least 50-100W from the grid, even if it's super-sunny.

Which you can obviously only do if you have at least that much load on the "essentials" side of the hybrid inverter.

 

[KLEVA]

@Muhammad Ahmed - As mentioned above, most decent invertors have a setting that will prevent feed-back to Grid. If you want to mix the solar with Grid on the input, then a Hybrid Invertor wont do that, but that is the only true way to prevent a small, or sudden feed-back. I don't see an issue with a extremely small feedback personally, there is no way you are going to supply the country with a 5kW invertor and take away the municipalities money... Lastly, from your description of the DB layout, even if there is a small feedback, it will get used by everything else on the phase before it could even think of feeding back to the municipal supply (I highly doubt that you are using only 1 phase for lighting only). You may be overcomplicating the installation and thinking?

[Youda]

On 2019/12/07 at 9:55 AM, Elbow said:

Which you can obviously only do if you have at least that much load on the "essentials" side of the hybrid inverter.

 

Not exactly, I would say:

Well, if you have some 24x7 loads on the essentials side, that would make the calibration easier.

But even if you have zero essentials loads, you still can calibrate to pull roughly 50W from the grid, as this is the typical "idle consumption" of a Chinese hybrid inverter. This idle consumption would be normally satisfied from the PV+battery, with the calibration it will be satisfied from the grid instead.

Just keep in mind that all these possibilities are limited by the hardware model. For example, there's a lot of parameters that you can tweak on InfiniSolar when running in Grid-Tie with Backup mode. But there's significantly less you can configure on a GoodWe inverter.