# Making Optimal Location-Sizing Decisions for Deploying Hybrid Renewable Energy at B&Bs
## 5 Results and Discussion
### Analysis of the Base Case
#### 5.1.2 Different Self-Sufficiency Ratios in the Base Case
Figure 5 also presents that a slight increase from 90% to 100% self-sufficiency would lead to a huge jump in the annual costs, from USD 15,797 to USD 21,499 (more than 35%). In fact, the MIP model decides on the fixed power generation capacity that ensures an uninterrupted supply for a whole year. However, as described in Figure 4, the model would behave completely differently depending on the self-sufficiency to cope with time differences between energy generation and consumption. These considerations lead to significant differences in battery capacity, energy generation, and costs when comparing 90% to 100% self-sufficiency, as summarized in Table 5. As solar energy increases in terms of the annual volume and percentage of energy sources, more capacity is required to store energy. At 100% self-sufficiency, the storage capacity reaches 126 kWh, more than double the capacity at 90% self-sufficiency (51 kWh). It is obvious that the battery costs also increase significantly, from USD 2689 to USD 6643. According to Table 5, the MIP model decides to generate more energy (50,217 kWh) than is required in either ratio. However, annual energy generation is less at 90% than 100% self-sufficiency (80,509 kWh vs. 116,942 kWh). As a result, the volume of the unused energy at 90% self-sufficiency is approximately 45% of the unused energy at 100% self-sufficiency. All these findings further reveal how a slight increase in self-sufficiency from 90% to 100% leads to significant changes in the annual costs (excluding the power grid costs and emission costs). Due to more affordable investments, incorporating the power grid into the RE system through a certain ratio of self-sufficiency would allow B&Bs to have better access to the energy transition. However, they still need to consider the emissions tradeoff that results from this integration. To highlight the role of the power grid, Figure 6 displays the satisfaction of energy demand by incorporating the power grid into the RE system at a self-sufficiency of 70% and 90%. As seen in both figures, the energy demands are significantly higher in the summer months than winter months. However, given a specific power generation capacity to produce RE, there will certainly be times in which that capacity is fully utilized, and there will also be times in which some capacity is not used. Consequently, it is important to minimize this unused capacity as appropriately as possible. When there is an option to acquire electricity from the power grid, this electricity would have the effect of smothering the remaining power demand to be satisfied by RE. The green bars in Figure 6a,b demonstrate such a smothering effect for the remaining power demand satisfied by RE, and that it is much more smooth at a self-sufficiency of 70% (Figure 6a) than 90% (Figure 6b). In summary, allowing a certain demand to be satisfied by the power grid would utilize RE capacity more evenly and reduce unused capacity, which in turn improves investment utilization. \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multirow{2}{*}{**Self-Sufficiency Ratio**} & \multirow{2}{*}{**Battery Capacity**} & \multicolumn{3}{c}{**Annual Energy Generation (kWh/Year)**} & \multicolumn{3}{c}{**Annual Costs (USD /Year)**} \\ \cline{3-10}  & & **Solar** & **Wind** & **Total** & **Solar** & **Wind** & **Battery** & **Total** \\ \hline
90\% & 51 & 46,854 & 33,655 & 80,509 & 5622 & 6731 & 2689 & 15,042 \\
100\% & 126 & 106,655 & 10,287 & 116,942 & 12,799 & 2057 & 6643 & 21,499 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Comparison of self-sufficiency 90% vs. 100%: battery capacity, energy generation, costs. Figure 7 summarizes all the details of the battery installation in the RE system. It is noticeable that the battery is required when the self-sufficiency is between 80% and 100%, and no battery when the self-sufficiency is between 50% and 70% (Figure 7a). Taking July as an example, solar and wind energy is only available during daytime hours, as wind speed is low at night until early morning.