ETi-ZES: Zero Export System by EnerMAN to Ensure Zero Export from Solar PV plants to Grid

Summary

India ranks fourth in the world in Renewable Energy Installed Capacity globally. With this, it would be relevant to say the use of solar energy for self-consumption would greatly contribute towards greener, cleaner, and cheaper energy, which in turn helps reducing the carbon footprint, decrease in energy cost, or the possibility of re-selling this energy to the national grid when local regulations allow it. Solar panels are directly connected to the grid through inverters; the energy produced is transmitted to the load for self-consumption or is returned to the grid. However, in some regions, the local grid operator does not allow energy injection into the grid which is called a zero export or injection limitation. The injection limitation consists of controlling the amount of energy produced by a photovoltaic (PV) plant injected into the grid. Limiting active power injection may be necessary to relieve the grid and reduce the reinforcement costs that this would imply. Zero export system helps in achieving the goal by not injecting any amount of electrical power into the grid.

Why ZES?

To ensure the electric grid’s stability, the solar plants may require limiting the power injection into the electric grid. In some countries, the injection of electricity is prohibited i.e., it is called zero export. In compliance with the law and to ensure the supply of a reliable electric grid some countries prohibit electric power injection limitations. It helps mitigate the abnormal events in electric grid through the generation of “undesirable” harmonics. By default, excess solar energy is clipped by an injection limiter. A more economical approach would be to include an intelligent energy management system such as ETi-ZES, which helps optimize the amount of energy lost by clipping the right amount of solar-generated power.

Existing solutions to manage zero feed-in

Controlling the energy production of a PV plant by considering climatic variations and consumption while ensuring that the current is not injected into the electric grid proves to be a real challenge. Fortunately, there are solutions to facilitate the energy management of the PV plant. Before installing PV, you can make sure that your installation size best matches the consumption, the aim being not to resell energy to the grid but to optimize your rate of self-consumption. 

ETi-ZES

EnerMAN’s ETi-ZES has a wide range of compatibility with commercially available inverters. It helps:

• Manage the power flow: reduce the solar inverters’ electricity production to ensure that solar production is not exported to the grid.  
• Records the data of equipments connected to it: collecting all data and alarms from multi-function-meters, PV inverters, Weather monitoring stations, etc.

It helps benefit from extended compatibility: the communication protocol supported is Modbus RTU/TCP. A simple logic to help explain how ZES works is as follows:

Step 1. Read the Active Power from the net meter.

Step 2. Check if Active power > Max Set point? If yes, increase the power on the inverter side.

Step 3. Check if Active power < Min Set point? If yes, decrease the power on the inverter side.

Step 4. Check again from step 1.

Minimum set point: it is the minimum required power input from the grid supply.Maximum set point: it is the maximum required power input from the grid supply in case there is enough solar power being produced to cater the load.

Key features of ETi-ZES are:

• It ensures zero export of energy from Solar PV to grid as per DISCOM guidelines to avoid penalties.
• It can be installed on Local workstation/PC/Server and if required data can be shared with cloud server for remote monitoring/ access.
• Real time active power control of Solar Inverter(s) by monitoring on-premises power consumption.

Is Solar Still Beneficial, Even with Zero Exports?

Yes, the real savings come from using the solar electricity generated locally rather than purchasing it from the grid. With grid electricity costing roughly Rs. 4/- to Rs. 5/- per kilowatt hour, reducing this cost by using the locally generated solar power immediately saves money.

Conclusion

The zero-export system maximizes self-consumption and uses most of the solar power generated locally. ETi-ZES helps achieve this goal economically.