What’s a microgrid, anyway?

by Peter Rosegg | Mar. 20, 2019

Microgrids are normally connected to the utility grid with the ability to take and send electricity.

If you follow energy matters, you’ll probably be hearing a lot about “microgrids.” The Legislature and Public Utilities Commission are considering how microgrids might work as part of the state’s renewable energy efforts.

“A group of interconnected electricity generators and users operating as part of the larger grid normally but able to operate alone under certain circumstances,” is a common definition of a microgrid.

The Schofield Barracks Generating Station is an example of a microgrid.

The new Schofield Barracks Generating Station is an example. Day-to-day, it feeds electricity to the Oahu grid to be shared by all customers. In emergencies, it can be “islanded” to keep military facilities like Schofield and Wheeler Army Air Field operating.

Some key points:

• A microgrid is normally connected to the utility grid, with the ability to take or send from/to grid.
• Size varies, but a microgrid usually includes: users, generation, storage, a controller, and point of common connection to the utility grid within a defined electrical area.
• The kind of generation, conventional or renewable, is not set, unless by local law or regulation.

So a microgrid might make sense in some circumstances. It’s all in the details: Why have a microgrid? Who would it serve? What would be included? How will it affect others?

The Hawaiian Electric Companies are always eager to work with customers to find the best ways to meet their particular needs, including a microgrid, if appropriate. We have some guiding principles:

• Fairness by increasing options: We encourage collaboration to determine and coordinate specific services needed, including design and operation of microgrids, if appropriate.
• Reliability of the main grid: Stability and reliability of the public grid must not be compromised.
• No cost-shift: Microgrids should not increase costs for customers outside the microgrids. Law and regulations need to ensure no cost shifting, along with other policy and technical requirements.
• Safety is paramount. Operating an electric grid is complex. Generally, we recommended microgrid operation be the responsibility of the utility to ensure safety of all customers and crews.

Benefits of a microgrid include increase use of renewable resources and lowers total energy costs.

So what are good reasons to consider a microgrid?

• Improved resilience through enhanced power quality and security;
• Increased use of renewable resources;
• Lower total energy costs.

In Hawaii, microgrids have been discussed for Kalaeloa in West Oahu, the University of Hawaii, Parker Ranch and the Natural Energy Laboratory (NELHA) in Kona. As yet, these have not moved far beyond the discussion stage.

The University of California at San Diego microgrid is often mentioned as a good example. It supplies electricity, heating, and cooling for the 1,100-acre campus with a daily population of 45,000. Its two 13.5-MW gas turbines, 3-MW steam turbine, and 1.2-MW solar-cell installation supply 85 percent of campus electricity needs, 95 percent of heating, and 95 percent of cooling. The microgrid is connected to San Diego Gas & Electric utility through a substation. The system produces 75 percent fewer emissions than a conventional gas power plant.

Peter Rosegg is a senior corporate relations specialist at Hawaiian Electric Company.