## 4 Results of the Optimizations
### Complete Distributed Generation Solution  
The complete distributed generation solutions include also the DCN into the superstructure and corresponds to the most general superstructure presented in Section 2 (see Figure 1). Table 15 shows the optimal configuration of the four optimizations performed: economic, environmental and the two intermediate optimizations, obtained by constraining the environmental objective function. The optimal configurations and the trends are very similar to the ones obtained in the previous paragraph, where the DCN was not included in the superstructure. Also in this case, the first two optimizations (economic and 30% optimizations) subdivide the whole system in two sub-DHN: sites 1-6, and sites 7-9 connected to the central unit. The last two optimizations (pure and 70%environmental optimizations) provide a DHN which connects all sites to each other. The DCN is adopted and always connects site 2 to sites 5 and 6, and site 9 to 7. Starting from the 70% environmental optimization, also site 1 is connected to site 6. Compared with the previous optimizations (see Table 12) the size of the CC decreases noticeable, because of the presence of the DCN. The introduction of DCN does not affect significantly the economic and environmental performance of the system. In fact, an improvement of only a few percentage points is obtained for the annual cost and for the annual emissions (see Table 16), in comparison with the case considered in the previous paragraph. Focusing on the economic optimization, the operation costs decrease by about 60 k\(\epsilon\). The annual investment cost increases by 10 k\(\epsilon\), due to the adoption of the three pipes of the DCN. Thus, the total annual cost decreases by about 50 k\(\epsilon\). The environmental optimization leads to a slight improvement of the total annual emissions (10 tons). From Figure 15, it can be easily inferred that the complete distributed generation solutions dominates all the other solutions analysed for this case study. The economic optimal solution allows us to obtain a reduction by about 43% of the annual cost and by about 25% of the annual emissions (see Table 16), compared with the conventional solution. The environmental optimal solution allows a reduction of about 50% to be obtained, compare with the conventional solution, but the total annual cost increases. The corresponding performance of the 70% environmental solution, which has been identified as the best compromise among the complete distributed solutions, are a reduction of about 32% for the annual cost and of about 41% for the annual emissions. \begin{table}
\begin{tabular}{c c c c c} \hline \hline  & **Environmental** & **70\% Env.** & **30\% Env.** & **Economic** \\ \cline{2-5}  & **Optimization** & **Opt.** & **Opt.** & **Optimization** \\ \hline DHN pipes (n°) & 14 & 8 & 7 & 7 \\ DCN pipes (n°) & 7 & 4 & 3 & 3 \\ Central pipe size (kW) & 7500 & 4980 & 4118 & 1922 \\ ICE (kW) & 4920 & 1840 & 2270 & 2380 \\ MGT (kW) & 0 & 0 & 0 & 0 \\ BOI (kW) & 12 & 1954 & 1406 & 1252 \\ ABS (kW) & 3570 & 1435 & 1190 & 1120 \\ HP (kW) & 3570 & 1890 & 1680 & 1680 \\ CC (kW) & 778 & 250 & 174 & 306 \\ PV panels (kW\(p\)) & 225 & 225 & 225 & 225 \\ ST panels (m\({}^{2}\)) & 0 & 0 & 0 & 0 \\ TS (kWh) & 0 & 0 & 2176 & 4939 \\ CS (kWh) & 0 & 0 & 0 & 0 \\ Central ICE & 0 & 0 & 0 & 0 \\ Central BOI & 0 & 0 & 0 & 0 \\ ST field (m\({}^{2}\)) & 22,736 & 21,764 & 17,664 & 8710 \\ Central TS (kWh) & 400,000 & 169,926 & 30,980 & 20,366 \\ \hline \hline \end{tabular}
\end{table} 
Table 15: Optimal configurations of the complete distributed generation solutions. A comparison among the annual energy magnitudes of the economic optimizations for the complete distributed generation and for the distributed generation integrated with the central solar system (Tables 14 and 17) shows some differences, which highlight the effect of the DCN in the economic optimal solutions.