# Investigation of Nanogrids for Improved Navy Installation Energy Resilience
## 4 Case Study
### Step 1: Collect System Information
#### 4.1.4 Step 1.4: Size Potential DER Configurations for Specific Critical Loads  
It is apparent from Table 1 that appropriate sizing of DERs is needed to accommodate the various critical loads. Each proposed nanogrid within the microgrid will have an associated DER that favors the average normal load and withstands the maximum critical load. Table 3 lists the summary of each nanogrid configuration.  
Generator power output values and fuel consumption are derived from the specification sheets from companies such as Cummins and GENERAC [59; 60; 61; 62]. Fuel storage for each generator is calculated from fuel consumption in gallons per hour and provisioned for 7 days with expected refuel to endure the mission duration of 14 days (this is a common tactic to reduce stored on-site fuel at both civilian and military facilities [63]). PV array area is determined by simulating PV power output from the solar irradiance data based on each nanogrid solely relying on PV generation and ESS storage. However, many bases have limited land available for large PV installations. While not widely implemented yet at military bases, civilian facilities have begun placing solar canopies over parking lots both to increase solar generation area and also to shade cars from the sun. Thus, the total available area for PV often may not meet the goal of supporting critical loads entirely off of PV and ESS. In this case study, we assume approximately 6000 m\({}^{2}\) is available for PV. This is close to reaching the goal of both the diesel generator and the PV and ESS independently supporting the critical load on each nanogrid.  
Iterations are done on each nanogrid until the generation capacity is able to accommodate the maximum and average critical loads with no load shedding. The simulation model of the nanogrid uses hourly time steps in order to determine the mission impact, load shedding, and system response for each scenario through deterministic methods [32]. Load shedding in our simulation is a vital factor in determining the constraints of the system and facility behavior. Energy demands not met result in required load shedding which influences mission impact [22]. Load shedding can impact the critical loads which can in turn impact national security [64]. Ensuring nanogrid DERs are sized appropriately ensures we are meeting the active power balance equation \(P_{load}=P_{generated}+P_{battery}\) at a steady state with all load demands being met [22].  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**MDI Score** & **Load** & **Load Type** \\ \hline
14 & 1 & Small Office \\
14 & 2 & Small Office \\
53 & 3 & Medium Office \\
84 & 4 & Large Office \\
89 & 5 & Warehouse \\ \hline \hline \end{tabular}
\end{table}
Table 2: MDI Scores for Individual Loads. Information from USCG Office of Civil Engineering, and NASA are used to calculate the case study MDI scores. In the case study, all MDI scores are represented on a 0-100 scale and all loads shown are considered critical.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Load** & **1 and 2** & **3** & **4** & **5** & **Microgrid** \\ \hline Mission Impact & 14 & 53 & 84 & 89 & - \\ Maximum Critical Load (kW) & 5.8 & 71.3 & 524.9 & 31 & - \\ GEN Power Output (kW) & 20 & 80 & 300 & 60 & 300 \\ GEN Fuel Storage (gal) & 1385 & 2147 & 3696 & 1512 & 8740 \\ Battery Capacity (kW\({}^{\text{th}}\)hr) & 384 & 5384 & 30,769 & 538 & 37,075 \\ Battery Output (kW) & 40 & 300 & 1000 & 70 & 1410 \\ PV Array Area (m\({}^{2}\)) & 50 & 500 & 5360 & 160 & 6070 \\ \hline \hline \end{tabular}
\end{table}
Table 3: Nanogrid DER Sizing Data. Sizing of generator power output is derived from specification sheets from generator datasheets [59; 60; 61; 62]. Fuel storage for each generator is calculated for a 7 day period based on fuel consumption rate. PV array size is determined by simulating PV power output from solar irradiance data based on each nanogrid relying solely on PV generation and ESS storage.