## 3 Results and Discussion
### Hourly Energy Balance for the Selected Integrated System
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Parameter** & **Unit** & **Value** \\ \hline Maximum Electric Power & (kW\({}_{\text{el}}\)) & 101.4 \\ Maximum Thermal Power & (kW\({}_{\text{th}}\)) & 249.5 \\ Electric Production & (MW\({}_{\text{el}}\)) & 820.8 \\ Thermal Production & (MW\({}_{\text{th}}\)) & 357.4 \\ Electric Self-consumption & (\%) & 94.9 \\ Electric Surplus & (\%) & 59.0 \\ Electric Integration & (\%) & 5.1 \\ Thermal Self-consumption & (\%) & 90.2 \\ Thermal Surplus & (\%) & 0.0 \\ Thermal Integration & (\%) & 9.8 \\ Global Electric Efficiency & (\%) & 13.4 \\ Energy Utilisation Factor & (\%) & 19.3 \\ Equivalent Operating hours & (h) & 8095 \\ Natural gas consumption & (Sm\({}^{3}\)) & 4512.6 \\ Natural gas saving & (Sm\({}^{3}\)) & 41,386.0 \\ Initial investment & (k\(\xi\)) & 636.8 \\ Net present value & (k\(\xi\)) & 1617.5 \\ Payback period & (years) & 4.90 \\ Reduced CO\({}_{2}\) emissions & (t\({}_{\text{CO2}}\)) & 253.8 \\ Reduced GHG emissions & (t\({}_{\text{CO2,eq}}\)) & 309.9 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Optimised integrated geothermal CHP systems. Figure 13: Hourly thermal and electric balance of the integrated energy system unit in July (**a**,**c**) and October (**b**,**d**) typical days. Mixed strategy. As already observed, the thermal surplus is absent, whereas the electricity injected into the grid is about 315 MWhel. The natural gas consumption reduces to 4512.6 Sm3 and corresponds to 9.8% of the quantity that should be used to satisfy the total thermal request of the commercial centre, adopting a traditional gas-fired boiler. The significant fossil fuel saving, and the noticeable rate of electric self-consumption, have a positive influence on the environmental impact of the integrated energy system. For this purpose, the standard and LCA (life cycle assessment) methodologies have been used [122; 123] to evaluate the carbon dioxide (CO2) and greenhouse gas (GHG) emissions, expressed as tons of CO2 (tC02) and tons of CO2 equivalent (tC02,eq), respectively. According to the standard approach, the emission factor for the electricity generation in Italy is equal to 0.343 tC02/MWh based on the national energy mix with both renewable and non-renewable sources, whereas the emission factor for the natural gas combustion is 0.202 tC02/MWh. The corresponding factors are equal to 0.424 tC02,eq/MWh and 0.240 tC02,eq/MWh when the LCA method is considered [122; 123]. The investigation highlights that geothermal exploitation in the suggested CHP system assures an annual decrease in the CO2 and GHG emissions larger than 250 tC02 and 300 tC02,eq, respectively, compared to the traditional methods to fulfil the user's energy request (electricity from the grid and thermal energy from a gas-fired boiler) and demonstrates that the integrated apparatus with the mixed operating strategy guarantees proper energy, economic and environmental performance. The proposed CHP geothermal system, developed for a commercial centre, can be easily extended and adapted to other applications (e.g., industries, dwellings, smart communities) owing to the high flexibility and the possibility to adopt different operating strategies depending on the user's energy requests. In this way, the distributed exploitation of renewable sources and local small-scale energy production can drive a faster and softer transition from fossil fuels and traditional technologies towards cleaner and more sustainable energy solutions.