## 4 Results and Discussion
### Optimization Results
\begin{table}
\begin{tabular}{c c c c c} \hline \hline  & **Traditional Energy System (Baseline)** & **Conventional Micro-Grid** & **Multi-Good Micro-Grid** & **Integrated Multi-Energy System** \\ \hline PV panels [kW] & - & 320 & 1312 & 321 \\ \hline Battery storage [kWh] & - & 1621 & 6257 & 1563 \\ \hline Diesel gensets [kW] & 181 & 19 & 159 & 42 \\ \hline Solar collectors [kW] & - & - & - & 1703 \\ \hline Hot-water tanks [kWh] & - & - & - & 8533 \\ \hline LPG boilers [kW] & 1417 & 1417 & - & 1 \\ \hline Electric heaters [kW] & - & - & 1467 & 229 \\ \hline Total investment cost [MUSD] & 0.18 & 1.68 & 6.24 & 2.56 \\ \hline Total O\&M cost [MUSD] & 11.55 & 8.31 & 2.74 & 1.53 \\ \hline Net Present Cost [MUSD] & 11.73 & 9.98 & 8.98 & 4.09 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Summary of installed nominal capacities, total investment, and operations and maintenance (O&M) costs for different energy conversion and storage technologies in the four proposed scenarios. Figure 6c: the electricity production of the multi-good micro-grid far exceeds the purely electric load, as a relevant excess needs to be redirected to electric heaters in order to also satisfy thermal loads. Conversely, the excess electricity conveyed to thermal loads in the integrated multi-energy system scenario represents only a negligible fraction of the total electricity production, i.e., that needed to compensate losses from the storage tanks. The integrated multi-energy system is the configuration allowing for the lowest LCOE, notwithstanding the need to have thermal energy conversion technologies spatially bound to the site of consumption and the subsequent impossibility to exploit economies of scale. This is a result of the combined presence of a second renewable energy conversion technology (solar collectors) and, moreover, of an additional and more cost-effective energy storage option, i.e., hot-water tanks. Figure 7 shows the thermal energy dispatch for representative users within each thermal user class, in the integrated multi-energy system. It is noteworthy how the adoption of solar collectors and hot-water tanks, integrated with the electric resistances, as technology to satisfy the DHW needs, made the thermal side of the system almost energy independent: the proposed system is capable of satisfying the totality of the thermal demand on its own, as it emerges from the low installed capacity of the LPG boilers in Table 3.  
This is a consequence of the fact that PV generation follows the same production pattern of solar collectors, bound to the daily solar irradiance profile. If other renewable sources, with a different daily production profile (such as wind), were exploitable, they could potentially further benefit from the presence of thermal storage, which could also be electrically charged and used during morning and evening peaks. Figure 7 represents the thermal dispatch strategy of the configuration scenario for the integrated multi-energy system, and shows in barred blue the output from the storage tank, fed by both electric resistance and solar collectors, and subject to thermal dispersion towards the environment, as can be deducted from the downward slope of the state of charge during the night. The resistance and the solar collector output energy are plotted in the background, and when they are not satisfying the loads, they are charging the tank, or curtailed. Curtailment is not plotted to avoid an overcrowded plot.