## 5 Methodology Validation
### Comparison between Scenarios  
The comparison between the different scenarios considered variables, such as installed capacity, estimated initial cost, needed area per scenario, austerity days, and loads interruption. The comparison is summarized in Table 11.  
From the comparison, it could be observed that CHP MG has the minor initial cost, the needed area is the least, and could be maintained in islanding mode operation without zero interruption for critical loads. However, this case does not contemplate the cost for operation. This cost depends on the use of the machine, the fuel consumption, and the fuel cost. Suppose that the CHP operates 24/7 at nominal value, the estimated cost per year is USD 191,000. This value is considering that CHP is operating with natural gas and the cost of fuel is USD 0.26 per gallon, as well as that the fuel flow for the CHP selected is 5.3 kg/s. However, the CHP operated with propane gas, the estimated cost per year is USD 734,000.  
Three of the proposed scenarios could be operated in islanding mode, however only scenario number two: PV and battery system does not require additional investment after initial cost. This scenario required a major area to be installed and presents interruption for the critical loads.  
The scenario number four is cheaper than scenario number two, besides the fact that the area required to install the MG is around fifty percent of the area required for scenario number two. However, scenario number four does not consider the fuel cost per CHP in the initial cost, similar to the above case, the estimated cost per year for CHP of 420 kW and assuming that the fuel flow is around 2.78 kg/s, and the cost per gallon on natural gas is USD 0.26, the estimates fuel cost per year is USD 102,000. This value is considering that the CHP is always operating at nominal power. It is important to mention that the CHP produces and additional energy that could be used for refrigeration, for example the library. In addition, scenario number four has less load interruptions that scenario number two does not have.  
Considering the use of propane gas, a comparison is made between the scenarios with the initial cost and a projection of the fuel cost for scenarios number 2 and 4 in 10 years. This information is summarized in Table 12 and Figure 20. From the comparison, despite scenario number 3 having a lower initial cost, when carrying out the fuel cost projection, the most profitable in 10 years is scenario number 4.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Scenario** & **PV** & **PV + Bat** & **CHP** & **PV + Bat + CHP** \\ \hline M & ode & Grid connected & Islanding & Islanding & Islanding \\ \hline Installed capacity [MW] & 1.4 & 3+3.94 & 0.8 & 1.4 + 1.5 + 0.4 \\ \hline Initial Cost [Million USD] & 2.4 & 5+4.7 & 1.7 & 2.4 + 1.7 + 0.8 \\ \hline Need Area [m\({}^{2}\)] & 10,000 & 21,000+1,600 & 9 & 10,000 + 625 + 12 \\ \hline Austerity Days & No & Yes & No & Yes \\ \hline \multirow{2}{*}{Load Interruption} & State & N/A & Yes & No & Yes \\ \cline{2-5}  & Average per day [hours] & N/A & 2.75 & 0 & 1.48 \\ \hline \hline \end{tabular}
\end{table}
Table 11: Comparison between scenarios.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Scenario** & **Initial Investment** & **Fuel Investment in 10 Years** & **Total** \\  & **[Millions USD]** & **[Millions USD]** & **[Millions USD]** \\ \hline PV & 2.4 & 0 & 2.4 \\ \hline PV + BAT & 9.7 & 0 & 9.7 \\ \hline CHP & 1.7 & 7.3 & 9 \\ \hline PV + BAT + CHP & 4.9 & 3 & 7.9 \\ \hline \hline \end{tabular}
\end{table}
Table 12: Comparison between Scenarios.