## 4 Results of the Optimizations
### Distributed Generation Solution Integrated with the Central Solar System
Table 14 shows the total annual energy magnitudes obtained for the optimizations of the distributed generation solution integrated with the central solar system. The trends of each item are similar to the ones observed in previous Table 11. The most important differences are the noticeable increase of the thermal production from the ST panels, and the greater amount of wasted thermal energy. They both are due to the presence of a large ST field, the production of which allows a great fraction of the thermal demand to be satisfied by renewable energy, but cannot be usefully exploited during all the year, even adopting the optimal operation strategy. In the pure and 30% economic optimizations, the solar field covers about 50% of the thermal demand and a small central thermal storage is adopted. It is operated with a daily/weekly charging/discharging cycles. \begin{table}
\begin{tabular}{c c c c c} \hline \hline  & **Environmental** & **70\% Env.** & **30\% Env.** & **Economic** \\ \cline{2-5}  & **Opt.** & **Opt.** & **Opt.** & **Opt.** \\ \hline CHP natural gas cost (k\(\xi\)/y) & 86 & 741 & 1059 & 1339 \\ BOI natural gas cost (k\(\xi\)/y) & 1 & 10 & 9 & 33 \\ Buoght electricity cost (k\(\xi\)/y) & 1482 & 451 & 221 & 32 \\ Sold electricity income (k\(\xi\)/y) & 30 & 125 & 234 & 373 \\ Photovolatic cost (k\(\xi\)/y) & 75 & 53 & 55 & 66 \\ Operating cost (k\(\xi\)/y) & 1464 & 1025 & 1000 & 965 \\ Maintenance cost (k\(\xi\)/y) & 10 & 63 & 88 & 113 \\ Total investment cost [k\(\xi\)] & 22,314 & 8248 & 6368 & 5359 \\ Annual investment cost (k\(\xi\)/y) & 1760 & 705 & 569 & 453 \\
**Total annual cost (k\(\xi\)/y)** & **3233** & **1792** & **1657** & **1531** \\
**Reduction wrt conv. solution** & **-22.32\%** & **31.64\%** & **36.89\%** & **41.61\%** \\ Electricity emissions (t/y) & 3104 & 945 & 463 & 67 \\ Sold electricity emissions (t/y) & 190 & 461 & 856 & 1385 \\ Natural gas emissions (t/y) & 388 & 3362 & 4748 & 6268 \\
**Total annual emissions (t/y)** & **3301** & **3846** & **4392** & **4950** \\
**Reduction wrt conv. solution** & **49.20\%** & **40.80\%** & **32.41\%** & **23.81\%** \\ \hline \hline \end{tabular}
\end{table} 
Table 13: Total economic and environmental results of the optimizations—distributed generation solutions integrated with central solar unit. \begin{table}
\begin{tabular}{c c c c c} \hline  & **Environmental** & **70\% Env.** & **30\% Env.** & **Economic** \\ \cline{2-5}  & **Opt.** & **Opt.** & **Opt.** & **Opt.** \\ \hline ICE electricity & 693 & 5957 & 8482 & 10,956 \\ MGT electricity & 0 & 0 & 0 & 0 \\ PV panels electricity & 239 & 239 & 239 & 239 \\ Bought electricity & 8718 & 2656 & 1302 & 188 \\ Electric user demand & 6968 & 6968 & 6968 & 6968 \\ CC electricity & 209 & 137 & 121 & 162 \\ HP electricity & 1938 & 453 & 529 & 363 \\ Sold electricity & 534 & 1294 & 2404 & 3889 \\ ICE thermal energy & 1024 & 8547 & 12,284 & 15,979 \\ MGT thermal energy & 0 & 0 & 0 & 0 \\ BOI thermal energy & 11 & 161 & 146 & 529 \\ HP thermal energy & 3991 & 675 & 866 & 497 \\ ST panels thermal energy & 20,931 & 17,880 & 14,651 & 6191 \\ Thermal user demand & 17,319 & 17,319 & 17,319 & 17,319 \\ ABS thermal energy & 0 & 2316 & 2336 & 2341 \\ Wasted thermal energy & 7850 & 6918 & 8018 & 2571 \\ CC cooling energy & 626 & 410 & 364 & 487 \\ ABS cooling energy & 0 & 1521 & 1522 & 1549 \\ HP cooling energy & 2122 & 820 & 872 & 717 \\ Cooling user demand & 2748 & 2748 & 2748 & 2748 \\ Wasted cooling energy & 0 & 3 & 10 & 4 \\ \hline \end{tabular}
\end{table} 
Table 14: Total optimal annual energy magnitudes (MWh)—distributed generation solutions integrated with the central solar system. Figure 11: Pareto front of the optimal distributed generation solutions integrated with central solar system. During summer, when the solar field is producing a lot of thermal energy, the thermal storage is full, but the users do not require thermal energy, therefore, the heat produced by the solar field is wasted.