## 4 Results of the Optimizations
### Distributed Generation Solution  
The distributed generation solution is obtained by adding the DHN to the isolated solution (Figure 7). The thermal energy produced in a production unit can be used directly either by the user of the site, or by other users, exchanging the heat through the DHN. This solution gives the opportunity to create a central production unit where all energy is produced and sent to the users through the DHN. The electric energy, if not used directly to the user has to be sent to the electric network. However, the isolated solution would still be adopted if it were more convenient, based on economic, or environmental evaluations. Table 9 shows the optimal configurations obtained for the distributed cogeneration solution. As previously introduced, the Pareto front of the bi-objective optimization has been identified by means of the \(\varepsilon\)-constraint method, by fixing the pollution levels at the 30%, 60% and 90% of the difference between the two environmental objectives of the economic and environmental optimal solutions. \begin{table}
\begin{tabular}{l c c c c c} \hline \hline  & \multicolumn{2}{c}{**Economic Optimization**} & \multicolumn{2}{c}{**Environmental Optimization**} \\ \cline{2-6}  & \multicolumn{1}{c}{\begin{tabular}{c} **Isolated** \\ **Solution** \\ **without TS** \\ \end{tabular} } & \multicolumn{1}{c}{\begin{tabular}{c} **Isolated** \\ **Solution** \\ **without TS** \\ \end{tabular} } & \multicolumn{1}{c}{\
\begin{tabular}{c} **Isolated** \\ **Solution** \\ **without TS** \\ \end{tabular} } & \multicolumn{1}{c}{
\begin{tabular}{c} **Isolated** \\ **Solution** \\ **without TS** \\ \end{tabular} } \\ \hline ICE electricity & 0 & 11,563 & 12,455 & 4599 & 4591 \\ MGT electricity & 0 & 0 & 0 & 331 & 175 \\ PV panels electricity & 0 & 239 & 239 & 48 & 0 \\ Bought electricity & 7884 & 173 & 166 & 7150 & 7395 \\ Electric user demand & 6968 & 6968 & 6968 & 6968 & 6968 \\ CC electricity & 916 & 137 & 191 & 398 & 394 \\ HP electricity & 0 & 1042 & 628 & 3337 & 3399 \\ Sold electricity & 0 & 3828 & 5073 & 1426 & 1,4012 \\ ICE thermal energy & 0 & 16,906 & 18,133 & 6603 & 6628 \\ MGT thermal energy & 0 & 0 & 0 & 566 & 299 \\ BOI thermal energy & 17,357 & 1064 & 787 & 205 & 36 \\ HP thermal energy & 0 & 2103 & 946 & 9279 & 9419 \\ ST panels thermal energy & 0 & 0 & 0 & 1108 & 1387 \\ Thermal user demand & 17,319 & 17,319 & 17,319 & 17,319 & 17,319 \\ ABS thermal energy & 0 & 1733 & 1604 & 290 & 131 \\ Wasted thermal energy & 0 & 1022 & 399 & 152 & 92 \\ CC cooling energy & 2748 & 410 & 574 & 1194 & 1182 \\ ABS cooling energy & 0 & 1127 & 1055 & 163 & 79 \\ HP cooling energy & 0 & 1213 & 1121 & 1392 & 1488 \\ Cooling energy demand & 2748 & 2748 & 2748 & 2748 & 2748 \\ Wasted cooling energy & 0 & 2 & 1 & 0 & 0 \\ \hline \hline \end{tabular}
\end{table} 
Table 8: Total optimal annual energy magnitudes (MWh)—isolated solutions. \begin{table}
\begin{tabular}{l c c c c c} \hline \hline  & **Environmental Opt.** & **90\% Env. Opt.** & **60\% Env. Opt.** & **30\% Env. Opt.** & **Economic Opt.** \\ \hline DHN pipes (n\({}^{\circ}\)) & 18 & 13 & 9 & 7 & 7 \\ ICE (kW) & 1920 & 2190 & 2290 & 2590 & 28,403,900 \\ MGT (kW) & 3900 & 0 & 0 & 0 & 0 \\ BOI (kW) & 502 & 0 & 0 & 0 & 0 \\ ABS (kW) & 3570 & 0 & 0 & 595 & 770 \\ HP (kW) & 3570 & 2590 & 2380 & 1715 & 1050 \\ CC (kW) & 1593 & 1682 & 1759 & 1620 & 1656 \\ PV panels (kW\({}_{p}\)) & 0 & 0 & 134 & 225 & 225 \\ ST panels (m\({}^{2}\)) & 1800 & 1800 & 734 & 0 & 0 \\ TS (kWh) & 36,000 & 6316 & 8553 & 12,337 & 15,017 \\ CS (kWh) & 36,000 & 0 & 0 & 0 & 0 \\ \hline \hline \end{tabular}
\end{table} 
Table 9: Optimal configurations of the distributed generation solution. From a general overview of Table 9, it can be noted that the DHN is convenient either from an economic or environmental point of view, while the MGTs, the CSs and the BOIs are actually never adopted, with the exception of the Environmental optimum.