Microgrids: What are they anyway?

It's not necessarily about size, it's about function

What are Microgrids?

The first thing you need to know about microgrids is that they’re not so micro at all.

Or at least they don’t have to be.

As microgrids have become more widespread in the United States and around the world in recent years, you might have started to think about what they mean to you. But if you’ve ever tried to take a deep dive into the topic, you might have discovered that a single definition of the term is difficult to find.

To wit, there’s this, from CIGRÉ (h/t Microgrids at Berkeley Lab):

Microgrids are electricity distribution systems containing loads and distributed energy resources, (such as distributed generators, storage devices, or controllable loads) that can be operated in a controlled, coordinated way either while connected to the main power network or while islanded.

And this, from the U.S. Dept. of Energy’s Microgrid Exchange Group:

A microgrid is a group of interconnected loads and distributed energy resources within clearly defined electrical boundaries that acts as a single controllable entity with respect to the grid. A microgrid can connect and disconnect from the grid to enable it to operate in both grid-connected or island-mode.

And, much more succinctly, this from Energy.gov: “A microgrid is a local energy grid with control capability, which means it can disconnect from the traditional grid and operate autonomously.”

Renewables such as wind power can be one of the sources for microgrids.

If you’re new to the topic and were reading all of that closely, there’s a decent chance you got bogged down in all the technical talk about distribution systems and interconnected loads. Don’t worry about it—that’s aimed more at specialists.

On the other hand, what you probably understood better were the island metaphors. And that’s critical, because while the term microgrid lead you to believe it’s all about size, the key here is actually autonomy. The Microgrid Institute, which begins its definition by calling a microgrid “a small energy system,” follows that up with this: “Microgrids are defined by their function, not their size.”

So what is that function? Essentially, a microgrid serves as an independent backup to the main grid, or macrogrid, by using the various resources (and they’re sometimes widely varying) at its disposal. That’s all it is. To put it another way, a microgrid generally works within the larger grid, but it can also disconnect and work autonomously as a locally controlled alternative.

Whether it’s because of an emergency, or because of its remote location, a community might need autonomy with its energy supply at certain times. And a microgrid, which is by definition locally controlled, provides that independence.

Microgrids are defined by what they do, not by their size.

Consider, for example, the potential benefits a microgrid can provide for a place like Alabama, which experiences severe weather regularly. In 2011, after a historic round of powerful tornadoes, some parts of the state went without electricity for a week or more. In a situation like that, a microgrid can break off from the main grid and provide an invaluable service to a community. Not only would Alabamians have electricity, but so would emergency-response workers.

“The key to understanding the importance of microgrids was driven home for us here in Alabama after the April 2011 tornadoes” says Daniel Tait, CEO of Energy Alabama. “Modern life is built on energy. Without its uninterrupted supply, especially for long periods of time, things begin to break down. Flexibility and resiliency is the name of the game.”

But that’s not all microgrids can do for a community. According to Berkeley Lab, microgrids can improve efficiency, relieve grid congestion, and provide a more reliable supply of energy, all at reduced cost to consumers. And according to Energy.gov, they can also cut costs, build energy independence and offer more flexibility. Those first two are ideas that everyone can get excited about, and more flexibility means potentially using renewable sources like solar and wind, in addition to whatever powers the macrogrid.

The remote Isle of Eigg derives most of its electricity from a microgrid.

So what does a microgrid-powered community look like? The answer, it turns out, is as varied as all those definitions from before. There’s Mesa Del Sol, a mixed commercial-residential development in New Mexico that harnesses solar power from a photovoltaic system mounted to a parking-lot canopy. Then there’s the Fort Collins Zero Energy District (AKA FortZED) in Colorado, a project aimed at creating as much energy locally as the area uses.

And there’s the remote Isle of Eigg in Scotland’s Inner Hebrides, which demonstrates the concept of islanding in literal fashion. Previously dependent on diesel generators, the 90 residents of the Isle constructed a microgrid that blends various renewables into a community-wide system. Completed in 2008, the microgrid uses hydro, wind, and photovoltaics to produce a reliable electrical supply 24 hours a day.

All of those projects are localized, and the Isle of Eigg is obviously smaller than the others. But the idea here is big, and with all the benefits microgrids can bring to a community, you might see one in your area sooner than you think.

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