Thanks to $5 million grant from the California Energy Commission, San Diego Gas & Electric (SDG&E) is expanding its experimental microgrid at Borrego Springs and tying it in with a utility-scale solar power plant operated by NRG Energy. The number of utility customers connected to the microgrid is expected to increase from 1,000 to 2,800 when the improvements are complete in mid-2016.

IKEA-Brooklyn-NYThe Borrego Springs microgrid is designed to run on renewable energy independently of the regional power grid. While it is connected to the centralized energy grid, it can disconnect and function independently during emergencies. It combines renewable energy with mega-batteries to even out fluctuations in solar energy.

“The microgrid has already kept electricity flowing to the community during several power outages,” SDG&E said in a statement.

At night, the batteries keep the power on to several small but crucial customers such as gasoline stations, grocery stores and “cool zones” where the public can find air conditioning during a power outage. Once the batteries are depleted, diesel generators can take over.

Southern California’s major utilities, the US military and the University of California–San Diego all are experimenting with small, self-sustaining electric grids made possible by advances in energy storage and computer software.

The trend toward microgrids will accelerate as the world transitions away from the old grid model of a large central power plant feeding power to hundreds of thousands of customers over a wide area. The new model is for many smaller renewable energy providers serving local communities but tied in to the central grid at its margins.

Microgrids are just a larger version of the home solar system with battery backup that serves most of the home’s energy needs, feeds excess electricity into the grid when it can, and draws power from the grid when necessary. While some utilities are fighting the trend, distributed renewables are the wave of the future.