Updated: Nov 12
Years after years more and more states are changing their net metering policies. Nowadays (2020) getting net-metering for industrial rooftop solar power plants is not possible in many states of India, even if you have someone in a government office.
And for the residence solar projects, sometimes it takes more than three months to get net-metering done for their plant. And even the charges of Net-metering are very high in some parts of Maharashtra.
In this blog, we cover the complete guide on the use of grid-tied solar power plant without net metering. , we cover the use of a grid-tie inverter off the gird.
Can a grid-tie inverter be used off-grid?
A grid-tie inverter can be used off-grid, with the help of ZED Advance. Grid-tie inverter requires reference voltage to generate electricity. The generator set can be used as a reference voltage for a grid-tie inverter to make it [grid tie inverter] work without gird power.
With ZED Advance any make of grid-tie inverter can be used off-gird. Zero Export device can eliminate the requirement of synchronization of grid power with a grid-tie inverter of a grid-tie solar power plant.
ZED Advance is used to protect the generator from solar surplus power. Learn more about how to protect the generator from solar surplus power.
An ON-Grid solar system without net metering
On gird, the solar system requires net metering to measure the total imported power from the state electricity grid and total power exported by the solar power plant. With ZED Advance any On-grid solar power plant can be sync (connected) with state gird without net metering.
Grid-tie inverter without net metering
With ZED Advance any make of grid-tie inverter can be commissioned without net metering. Also, there will is no requirement of approval from the state electricity grid for the use of ZED Advance with Grid tie inverter.
With ZED Advance any make of grid-tie inverter can be converter into a grid-tie inverter that does not feed into the grid you also call it grid-tie inverter no back feed or grid-tie inverter without grid
This type of system is also known as grid-tie inverter without export or grid-tie inverter without power
Here are the in-depth details on On-grid Solar power plant without net-metering
What is an On-Grid solar power plant?
There are several types of solar power plants, and each type consists, some common things, like solar panels, solar inverter, mounting structure, AC/DC Cables and installation accessories like PVC conduits, cable lugs and glands etc.
What will be the plant called in depends upon the type of equipment, connection and inverter it has.
If the plant is in sync with grid power, then it will require an On-grid solar inverter, which is also called a string inverter and the plant will be called On-grid type solar power plant.
The on-grid solar inverter requires a reference power source to generate power in synchronization with the reference power. And the reference power source can be grid power or power from a Generator (DG SET). But considering a Generator (DG SET) as a reference power source, could be a big headache, Learn more.
For the first one-minute solar inverter (string inverter) study this reference power (during this time the whole load is on the reference power source) and generate power in synchronization of reference power. If the power generation from the solar power plant is less than the power required, the reference power source will serve the remaining required power. And If the generated power is surplus (i.e, power generation > power required), then this surplus power will be feedback to the reference power source.
As long as sunlight is available, the main source of power is the On-grid solar power plant and when the sunlight is not available, the reference power source (Grid power) will become the main source of power.
Net meter is required to estimate how much power is exported and how much is imported. A On-grid solar power plant can work without Net meter.
What happens, when you connect a solar power plant (grid-tied) with a grid without net metering?
The answer is very simple, Your electricity bills will start rising in place of reducing. but how?
An ordinary electricity meter only measures the amount of power flow through it, irrespective of either you are importing or exporting the power. So all the surplus power your solar power plant generates will be added to your electricity bill.
For example, Your home consumes 600 units in a month and you install a 5kW of grid-tie [grid connected] solar power plant without net metering which generates 600 units of power in a month.
So, will you get an electricity bill of 0 units?
The answer to this question is No. Instead, you will get a higher electricity bill.
Your new electricity bill could be higher than 720 units but, why?
PV power plant generates electricity only in daylight, so 600 units of power generated by Grid-tie PV plant can be used for day time load only.
Also for most of the home during the night, the load requirement is usually 1.5 times higher than the day time load.
So the day time power consumption for a month is 240 units whereas for night time same is 360 units out of total 600 units in a month. [240+360= 600]
[You can find out the same by using simple algebra Y + 1.5Y = 600]
Now, from the total power generated by gird connected Solar power plant, 240 units will be consumed by the home load and 360 units of power will be exported back to the grid.
And energy meter will add these exported units with the total night time power consumed.
360 [exported units] + 360 [Total night time power consumption] = 720 Units.
And that how you will get an increased electricity bill.
Even if your day time and night loads are the same still you will get no benefits from the solar power plant.
Let’s take one more situation when your total power consumption [600 units] are for day time only. In other words, you are only consuming power in the day time and your nighttime power consumption is zero.
Still, the load and the power generation [from PV plant] both vary throughout days.
This will leads to some sort of power exported to the grid and which will again affect your electricity bills.
On the other hand, Net-meter counts the amount of power imported from the grid and from total imported power it will subtract the amount of power exported to the grid.
But you don’t need to worry about these issues, solar power plants can work without net-metering. The purpose of net-metering is to measure the units consume and unit exported, only.
There is a device called ZED Advance which enables plant owner to limit the power generation of the plant.
This means this device will control the (output) power generation of the solar inverter (string inverter) as per the load. Or in other words, it will keep the generating power of the solar power plant below the load so that no surplus power can be generated.
[Curious about ZED Advance? Click here to learn more]
How solar power plant without net metering works?
To understand the same refer to the below two diagrams showing typical circuits.
The first diagram shows the typical circuit of a solar power plant having no net-metering
The second diagram shows the typical circuit Diagram of a solar power plant having no net-metering along with DG synchronization.
In both diagrams, you will see that how the ZED advance connects with the solar power plant having no net metering.
In addition to ZED Advance, you will also require 10 C x 1.5 Sqmm cable with suitable rating of current transformer (one for each phase) and 3 C x 1.5 Sqmm cable for load feedback to ZED and CAT-6 LAN cable for connection of ZED Advance with inverters as well as Local network.
ZED Advance analyze the load feedback and set the inverter output accordingly. So that no excess power can be generated. And that how solar power plant without net-metering works.
The best thing about this type of solar power plants is that you don’t need any approval from any government department because you are not exporting any surplus power to the grid. Your plant can start producing power from day one of its commissions because you don’t need to wait for the net-metering work.
If your plant size is like 1MW and some part of it is commissioned (let says 200 or 500kW) with the help of this device you can start your commissioned plant. And you will get the benefits of the commissioned plant before the whole plant gets commissioned.
This device (ZED Advance) can also work like a DG synchronizer. So, if you have DG SET and you want to sync your solar power plant with DG SET in case of power failure. You can run (sync) your DG SET with your solar power plant with the help of this device.
[Curious about how to syn DG SET with PV plant? Click here to learn more]
One more cool thing about this device is that it also provides Remote monitoring of the PV plant and the subscription charges are included in the price of this device. So, you don’t need any data logger for the monitoring of your plant. You can also connect your weather sensors like Pyranometers, temperature sensor, humidity sensor, wind speed and direction sensor, rainfall sensor, UV index and solar radiation simultaneously. All the data can be centralized, organized and display at our web portal through a LAN network.
Again, if you have DG SET and you want to monitor the load on DG SET during power failure and the time duration of power failure. With this device, it is again possible.
Our Zero Export Device (or Export limiter) is compatible with most of the popular makes of inverters like ABB, SMA, Hitachi, Consul Neowatt, Huawei, Solar Edge, Kaco, Delta, Solis, Kirloskar, polycab, Sungrow, Growatt, Fronius, REFU Sol, Schneider, Zever solar and many more.
One single device can control and monitor different makes of solar inverters. So, if you have different makes of solar inverters (for example SMA & ABB) at one site (for one plant), you don’t need to buy two different makes of Zero Export Device [ ZED Advance].