# Investigation of Nanogrids for Improved Navy Installation Energy Resilience
## 3 Methodology
### Step 3: Analyze Threats to Base Energy Security
#### 3.3.1 Step 3.1: Reference Baseline Threats  
An analysis of threats is important for the base energy manager to ensure that the microgrid and associated nanogrids are resilient against a variety of potential threats. Currently DOD and NAVFAC consider island mode as a primary threat from an energy resilience standpoint. Island mode, where the base is cutoff from outside electrical energy for 14 days, serves as the baseline threat scenario in subsequent steps of this methodology. In addition to island mode, we advocate for inclusion a variety of additional internal and external threats of specific interest to military installations that are subsequently discussed. While we believe this is a reasonable minimum list of threats to consider, specific locations and specific global and regional threat protection postures may require additional threats to be included in subsequent methodology steps where they serve as initiating events. The following internal threats are the minimum set that we recommend a base energy manager use:  
Loss of Generator(s): This threat is the loss of one or more generators simultaneously. Simultaneous failure (a common cause event) can happen due to contaminated diesel fuel being delivered to all generator fuel bunkers or incorrect maintenance being performed on all generators, for instance. Loss of PV Array(s): Similar to the loss of generators threat, PV array maintenance could have been mismanaged or there could be a design flaw across all installed PV panels or controllers. Other ways a loss of PV array can occur is dirt or avian organic material on the PV modules, shading, or incorrect incidence angle among others [42]. Maintenance Personnel Insider Threat: The DOD defines insider threat as \"the threat that an insider will use her or their authorized access, wittingly or unwittingly, to do harm to the security of the United States\" [43]. All militaries face a similar insider threat that can compromise national security mission success. Two incidents of insider threats at United States military bases include include Fort Hood in 2009 where an lone Army officer shot and killed 13 people and in 2013 when an Navy contractor shot and killed 12 civilian employees [43]. It is understood that military installations are not a perfectly safe sanctuary and therefore it must be taken into consideration that, for instance, damaging PV arrays or transformers with a gun, or generators by draining engine oil would be a potential occurrence [43]. This type of deliberate attack is likely to occur against critical loads that are most valuable to mission success. The following external threats are the minimum set that we recommend a base energy manager use:  
Natural Disasters: Site-specific natural disasters must be included in potential external threats. Such threats could include flooding, earthquake, tsunami, tornadoes, etc. We specifically focus on fire and severe storms in this article, and provide more detail below on the fire threat. Similar detail can be developed for each potential natural disaster based on site-specific considerations. A 2013 study showed that the Northern California and Monterey Peninsula (where the military base we work at is located) has an estimated 31-40% chance that given a single source of ignition, a fire will grow to 100 plus acres in size [44]. This is the second highest ranking category for fire growth within the United States. Given the severity and likelihood of this natural disaster or ignition occurring by an attacker not only in the American west but globally anywhere that a wild-land urban interface exists [45], we advocate this threat be included. Indeed, the 2020 fire year saw three major fires within 30 miles of the military bases in the greater Monterey Peninsula area [46]. Explosion from Terrorists: Since 1997 the Joint Chiefs of Staff implemented the Combating Terrorism Readiness Initiative Fund which has allocated approximately $80 million to U.S. and overseas installations for Anti-Terrorism Force Protection improvements [47].