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Implementing a Military Microgrid

Microgrids can increase installation resilience, incorporate renewables, and address other net zero objectives that closely align with basic military energy goals and needs.  

By Justin Day, P.E.   


 

 Construction workers complete electrical connections on phase 2 of a solar microgrid project at Fort Hunter Liggett, Calif., March 12, 2013. USACE photo by John Prettyman 

Everything, even energy infrastructure, must adapt to changing conditions. Military installations and large installation-like assets, such as university campuses and large industrial plants are utilities, are required to respond no matter what and need a power system up to the task. Continuously providing reliable electricity can be a challenge. Through a combination of distributed generation, energy storage, and intelligent controls, self-sustaining microgrids offer a resilient power system for military installations. In addition to providing energy assurance, microgrids are a proven solution that can incorporate renewables, increase efficiencies, and meet other net zero goals.

In a military microgrid, a base can island itself from the larger grid to provide and manage all its own power. The ability to self-generate power while disconnected from the grid is not new. Non-military installations, especially those containing critical infrastructure, have successfully implemented systems capable of islanding before the term microgrid was ever created. These applications can serve as examples for the military, since they share many of the same goals of resiliency, energy independence, and mission-critical availability.

 

BALANCING TRADEOFFS

When an installation islands from the grid, it changes the topology of the local power system. These changes come with tradeoffs—such as reduced sensitivity and selectivity of protective devices as well as constraining local generation assets—that must be considered to ensure resiliency when implementing a microgrid.

Resiliency depends on many factors. These include knowing what actions are necessary to island an installation while maintaining mission-critical availability. Because microgrids have low inertia, it is imperative that they control and operate quickly. Depending on the available distributed energy resources (DER), a microgrid controller may need to operate at subcycle speeds in order to reliably balance load with available generation. When determining response timeline requirements, it also is important to consider any delays or lags that may be associated with communications protocols responsible for sending or receiving commands.

Power system modeling analysis plays a critical role in selecting the appropriate strategy that works best for the project and an iterative process. It is important to use validated models during this stage and not just theoretical models. Modeling lets the microgrid designer to demonstrate system responses to certain catastrophic events that are prohibitive to field test.

Because a military microgrid must be able to adapt to changing conditions and withstand and recover rapidly from disruptions, it is beneficial to review scenarios and system recovery times that can be demonstrated using robust modeling. Modeling also allows system users to get the equivalent of years’ worth of operational data in a very short time period. When compared to expenses of field testing or the effects of mis-operation, modeling could be the most cost-effective way to mitigate power disruption risks.

Changes to local system topology can impact the sensitivity and selectivity of protective devices as well. In some instances, this can lead to a loss of relay coordination, which means that some electric services may be unprotected. When an installation is islanded from the bulk electric grid, the local DER heavily influence the fault current values and paths. Sometimes the power electronics associated with renewable forms of generation are oversized so that they can contribute enough fault current to maintain sufficient levels required for tripping and coordination. However, this approach should be avoided because it leads to excess cost and inefficiencies in design. In order to maintain protection in both islanded and grid-connected modes of operation, it is crucial that an installation implement adaptive relay protection.

Adaptive relay protection can be simple or complex depending on the microgrid’s configuration and intended operation. Many digital relays have the capability to operate on selectable time versus current curves. This allows the system integrator to use different settings within the same protective device based on grid connected or islanded operation. Traditional installation infrastructure is designed for unidirectional power flow. Microgrid topologies may require bidirectional power flow; additional directional protection may need to be installed to supplement existing protection schemes. Approaches that include hardware-in-the-loop testing ensure the actual devices intended for use are tested in a controlled environment and are preconfigured to integrate with the system before they get to the field. This demonstrates that the system is protected in all modes of operation under multiple scenarios.

A microgrid topology can be designed to support multiple islands within the same microgrid to increase resiliency. 

SELF-SUSTAINING AND COST EFFECTIVE

Military operations are not the only organizations that regard a continuous supply of power as a necessity. A university in California recently installed a microgrid to prevent power supply disruptions from affecting its research. One of the key hurdles the university had to overcome was balancing electricity loads and available generation. By selecting a microgrid controller that was able to operate at subcycle speeds, it was able to effectively and efficiently shed load based on their priorities and available DERs. The school was also able to shift its energy usage by having predefined set points for thermostats and other necessary facilities. Keeping the temperature higher allowed for reducing the amount of cooling energy needed or lighting demands. The campus community can now proactively conserve power, making it easier to manage their energy supply when islanded.

Scattered across the campus were a series of renewable resources and associated energy storage. This added another layer to their resiliency, allowing the university to self-sustain when disconnected from the grid.


When an installation islands from the grid, it changes the topology of the local power system. These changes come with tradeoffs—such as reduced sensitivity and selectivity of protective devices as well as constraining local generation assets—that must be considered to ensure resiliency when implementing a microgrid.


 

Microgrids are a proven way to facilitate renewable integration to meet operational needs as well as clean-energy goals. In some instances, system users can bias their usage of assets to maximize renewable generation when available. By analyzing strategies to reduce electrical demand and maximizing the efficiency of any existing resources, the university was able to progress towards making net zero a reality. As it found, energy conservation and asset analysis are good starting points for any installation’s journey towards net zero. These goals also have the benefit of being easily achievable and require little effort compared to other net zero tasks.

 

MISSION-CRITICAL AVAILABILITY

Reliable power is critical to the pulp and paper industry. Paper production runs 24/7. Process disruptions can cost millions. When the process stops, the wasted product must be cleared before the process can begin again. This leads to costly time and production losses. In one paper mill in the southern United States, the plant operations team determined that there were mission-critical processes that had to remain online even when there was a loss of grid power. To mitigate the effects of these disruptions, the mill upgraded its existing facilities to operate like a microgrid. Instead of developing a microgrid, though, the paper mill was able to enhance its existing infrastructure to incorporate a microgrid control architecture. It was able to increase resiliency by rethinking how it was operating combined heat power assets. Similarly, many military microgrid applications simply require updating or modifying existing infrastructure and do not require large project budgets.

The paper mill had a good relationship with the local utility and was able to achieve benefits with a microgrid-like operation by interacting with the grid instead of islanding during disruptions. That resiliency and reliability allowed it to act as a dynamic resource, providing ancillary services to the grid, including easing congestion, reducing peak demand, and being able to respond during grid emergencies. Realizing that personnel cannot always be pulled from mission-critical tasks to operate the mill’s microgrid, the paper mill worked to design a solution that was simple to control, operate, and maintain.

 

AN ADAPTABLE SOLUTION

Energy has a multitude of security dimensions. There are many risks and costs associated with relying on fossil fuels for power generation, including logistical and operational challenges. Although most of a microgrid’s purposes are security-related, they can also help installations meet net zero goals, including increased renewable penetration, maximized generation asset efficiency, and optimized operating costs.

Self-sustaining energy islands that can stay on during grid-wide blackouts are valuable to military installations that cannot allow power outages to keep them from performing their missions. To tailor a solution that best meets an installation’s unique needs, military microgrids can draw upon varied examples and lessons learned in other industries.

Even though each installation has a unique set of assets and possible scenarios, a microgrid can be a simple and economical solution for bases needing to increase their resilience while addressing energy objectives. 

   


 

Justin Day, P.E., is Senior Marketing Program Manager; 509-339-2752, or This email address is being protected from spambots. You need JavaScript enabled to view it.