Microgrids generate and store electricity in small geographic areas. While they can create power anytime, they are designed to generate electricity locally if the main grid is down. If there is an outage, they detach from the grid. That’s important. Then they use solar, wind, diesel, natural gas, fuel cells, battery storage, whatever they got to create power. These grids are specifically designed to operate for days in a general outage. Rooftop solar on a house generally can’t do this. However, 5,000 houses and businesses in an area linked together in a microgrid can.
Microgrids can be especially useful in emergencies because they continue to provide power to crucial areas like hospitals, fire, law enforcement, water pumps, and more.
Also, microgrids can be built faster and cheaper than, say, burying PG&E main transmission lines, which would cost tens of billions and take well over a decade, assuming money was available, which it isn’t. With a microgrid, an area doesn’t much care if the main power is down for a few days.
From Popular Science:
The system is basically a small power grid that can either work in parallel with the greater grid or isolate itself in what’s called “islanding.” A microgrid has its own internal power source—often solar panels, diesel generators, or some combination thereof—that it can use to keep a community functioning during a blackout. Because of its local scale, a microgrid doesn’t need a vast system of overhead lines to deliver power and could therefore keep safely functioning when a central grid turns off due to fire hazards.
California already has several microgrids, which have been successfully tested. They performed well during unexpected outages and are cost-effective. One reason is they can use their own power when prices are high, saving money. Microgrids also provide resilience to their area.
These demonstration microgrids are delivering a reported utility bill savings of 20 percent to 60 percent, primarily in avoided demand charges, and some have successfully islanded during power outages.
State regulators believe microgrids, or localized grids that can operate apart from or in concert with the traditional power grid, offer solutions to some of the challenges facing grid operators, including integrating distributed energy resources.