Grid edge

The grid edge is the far end of the electricity grid, where homes, shops and small businesses take power, and where rooftop solar panels, home batteries and electric car chargers are now connected. The grid was built to send power one way, from large power plants to users. At the edge, some users now also send power back.

Here is what changes. A house with rooftop solar uses its own power at noon, and may send the extra back into the street's lines. A neighbourhood with many such houses can send so much power back that the local transformer becomes overloaded or the voltage rises too high. In the evening, the same houses charge their cars, and demand jumps. The grid operator now has to deal with thousands of small, changing sources and loads, not a few large plants.

The local power company, called a distribution company or discom, owns the lines and transformers at the edge. These were sized for the demand expected in an area, not for power coming back. In India, a rooftop solar owner can be credited for power sent to the grid under net metering rules set by state regulators. Without local sensors, a discom often does not know that a transformer is overloaded until it burns out. So the edge needs readings from meters and from the transformers themselves.

Take, for example, a housing society in Pune with rooftop panels on every building. At noon, it sends power into the grid. At 8 pm, when the sun is down and the residents charge their cars, it draws heavy power. Consider a home battery that charges when power is cheap and supplies the home at peak hours. Imagine a thousand such batteries controlled together as one source; see virtual power plants.

Managing the edge needs smart meters, transformer monitoring, smart electrical panels and grid control software. It also depends on converting between DC and AC. The whole picture appears in a home as its own grid.

How is it different from grid balancing? Grid balancing is the task of keeping supply and demand equal across the whole grid. The grid edge is the place, at the user's end, where that task is becoming harder.