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Microgrids: breaking down the buzzword

Illustration depicting microgrid with campus-configuration

This is a basic representation of campus microgrids on an Air Force installation. Each campus has separate energy resources and both campuses are controlled by a master controller to island them from the main grid and direct power within or between them. (U.S. Air Force photo illustration by Jeff Pendleton)

TYNDALL AIR FORCE BASE, Fla. -- The Air Force Civil Engineer Center is partnering with installations around the world in locations like Joint Base Pearl Harbor-Hickam, Hawaii, and Otis Air National Guard Base, Massachusetts, to test and determine the future of microgrids as a powerful tool in the energy assurance toolbox. 

The term microgrid is a “buzzword” that is commonly used and just as commonly misunderstood. 

This article, the first in a series on microgrids, will define them and their key components. Future articles will include information on the Air Force’s current microgrid projects, the Air Force’s direction for microgrids, and what they mean for installations in the future.

The Air Force’s perspective on what a microgrid is and is not, is an important first step that ensures a common understanding of the term.

Across industry and the federal government, the Department of Energy’s microgrid definition in their initiative report has been widely adopted. As stated in the report, “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.”

Tarone Watley, AFCEC subject matter expert on energy surety, explains the practical components of microgrids and what this means for the Air Force. “A microgrid should contain four primary components,” says Watley. “It must have energy resources, either conventional or renewable, multiple energy loads, controllers to direct the power and optionally, storage.”

Energy resources include sources powered by either fossil fuel or renewables, and can be of any scale appropriate to the loads required to support the microgrid. In many cases, it may be appropriate to have a mix of backup diesel generators in conjunction with certain types of renewable sources to provide the greatest resiliency to the mission being supported by the microgrid.

The way a microgrid is configured and the loads it will support are determined by the criticality, size and complexity of the base’s tenant missions.

For the Air Force, Watley says microgrids will likely be either a campus microgrid supporting two or more buildings on an installation or a whole-installation microgrid configured for the entire base.

“Right now, microgrids are mostly being demonstrated with campus configurations,” says Watley. “Furthermore, bases may see multiple campus configurations on their installations that address different, but similarly critical, missions in the near future.”

The controls that grid-connect or island a microgrid can be low-tech, using a series of manual devices for activation and directing power to the loads within it, or can be “smart,” using automated software algorithms from a computer system. An even more complex controller can be found inside next-generation microgrids, where the controller leverages artificial intelligence to direct all microgrid functions.

The primary differences between these three controller options are the time required to bring the microgrid online and restore power, and the amount of human-in-the-loop interactions. Each element is extremely important to the responsiveness and effectiveness of the microgrid and affects potential mission impact.

The final, optional, component of a microgrid is storage. Adding energy storage to a microgrid can help minimize grid downtime and create a buffer that helps the microgrid ride though power fluctuations or loss of intermittent resources. According to the Energy Storage Association, the main purpose of storage is to “balance power supply and demand instantaneously – within milliseconds.”

“Storage stiffens the microgrid against sudden changes such as loss of a large load or a solar or wind renewable resource,” Watley said.

These systems are commonly electrochemical (batteries), mechanical (fly-wheels) or thermal systems.

“Providing our warfighters with reliable, resilient energy is a key component of mission assurance,” said Maj Josh Aldred, deputy director of AFCEC’s Energy Directorate. “AFCEC is committed to providing installations the support they need to determine where innovations such as microgrids can complement and enhance their plan for energy assurance.”

Equally important to understanding the basic components of a microgrid is understanding what a microgrid isn’t.

“In the larger conversation about energy assurance, microgrids are not an all-encompassing solution,” Watley said. “They are simply one tool that can get installations closer to energy assurance.”

If you have questions about microgrid design or implementation, experts at the Air Force Civil Engineer Center are readily available to assist you. These experts in power and energy routinely solve implementation problems while ensuring compliance with Air Force energy and cybersecurity directives. Contact them through the Reachback Center, available through CE DASH or at 888-232-3721.

Editor’s note: This is the first in a series of articles published on microgrids. The connecting and over-arching theme of these articles is to illustrate how the Air Force intends to use microgrids to provide mission assurance through energy assurance in support of the warfighter.