India Solar, Wind, Biomass, Biofuels – EAI

Grid-connected Captive Solar Plants

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A grid-tied solar power system (also referred to as grid-intertied, or on-grid or utility-interactive (UI)) produces solar electricity that is fed directly into the utility grid, hence the term grid-tied, as the system is tied, literally, to the grid. In US and Europe, in a grid tied system any surplus power generated is sold back to the power utilities. When the sun is not shining one can buy power back from the utilities. This is done using net metering; a method of metering the energy consumed and produced using a renewable energy generator.

In India, net metering system is currently not available (as of Apr 2011) and thus the surplus power generated from renewable energy sources cannot be sold to the utilities. The benefit of a grid-tied system is that they can reduce the dependence on utility.

There are two general types of electrical designs for PV power systems; systems that interact with the utility power grid and have no battery backup capability; and systems that interact and include battery backup as well.


Grid-connected or utility-interactive PV systems are designed to operate in parallel with and interconnected with the electric utility grid. The primary component in grid-connected PV systems is the inverter, or power conditioning unit (PCU).

The PCU converts the DC power produced by the PV array into AC power consistent with the voltage and power quality requirements of the utility grid, and automatically stops supplying power to the grid when the utility grid is not energized. A bi-directional interface is made between the PV system AC output circuits and the electric utility network, typically at an on-site distribution panel or service entrance. This allows the AC power produced by the PV system to either supply on-site electrical loads, or to back feed the grid when the PV system output is greater than the on-site load demand.

At night and during other periods when the electrical loads are greater than the PV system output, the balance of power required by the loads is received from the electric utility. This safety feature is required in all grid-connected PV systems, and ensures that the PV system will not continue to operate and feed back onto the utility grid when the grid is down for service or repair.


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