# 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  
To ensure the model provides an accurate solution to achieve a specific ratio of self-sufficiency, an equation about demand would be added as in (8). \[REQN_{t}\leq\text{REQ}_{t}\ \ \ \ \ \forall t\in T \tag{8}\]  
where \(REQN_{t}\) is a decision variable representing the actual energy demand, which needs to be satisfied with RE during the time period \(t\). Each \(REQN_{t}\) must be less than or equal to REQ\({}_{t}\) which is the (real) energy demand at the subject B&B during planning period \(t\). The analysis of the energy flow at different self-sufficiency ratios is performed to understand how RE generation and storage can satisfy demand in the week of July (Figure 4). The energy flow on Wednesday as the central day of the week at self-sufficiency 90% can be described as follows:  
* In the first time period, \(t=9\) and REQ\({}_{9}=23\) kWh, the model allocates the power grid to satisfy the demand as \(REQN_{9}=0\) and there is no saving energy in the battery from the previous time period, \(I_{8}=0\). * In the second and third time period, \(t=10\) and \(t=11\), the model allocates solar and wind energy to satisfy all demand in these periods, as \(REQN_{10}=29\) kWh and \(REQN_{11}=71\) kWh. However, there is some surplus energy that would be saved in the battery, \(I_{10}=71\) kWh and \(I_{11}=46\) kWh. * In the fourth time period, \(t=12\), and REQ\({}_{12}=46\) kWh, the model allocates energy saved in the battery from the previous time period to satisfy demand as \(REQN_{12}=0\), \(I_{11}=46\) kWh, and \(I_{12}=0\). On the other hand, at 100% self-sufficiency, the model would allocate solar and wind in daytime hours to generate much more energy than required. The energy generation is not only used to satisfy demand at that period but also to save for the next period. For example, in the third time period, \(t=11\) and REQ\({}_{t=11}=71\) kWh, the model would allocate \(E_{t=11}=179\) kWh and \(I_{t=11}=95\) kWh. As a result, the volume of energy stored in the battery increases significantly since the model decides to generate more than twice as much energy at 90% self-sufficiency (Figure 4b). Considering different ratios of self-sufficiency, Figure 5 presents the annual costs from 50% to 100% sufficiency with a difference of 10%. As a variety of self-sufficiency is evaluated, the annual costs also consider the costs of the power grid and emissions. The annual costs increase depending on the ratio of self-sufficiency as follows: USD 11,044, USD 12,360, USD 15,019, USD 15,084, USD 15,797, and USD 21,499 for self-sufficiency ratios of 50%, 60%, 70%, 80%, 90%, and 100%, respectively (Figure 5a). There is a tradeoff between the annual costs and the sustainability performance that needs to be analyzed. Since increasing ratios affect costs differently, 50% self-sufficiency can be used as a baseline. For example, if the B&B chooses to be 90% self-sufficient instead of 50%, the annual costs would increase by 42.6%. Emission costs, on the other hand, decrease by 80.0% as the power grid supplies less electricity, from 25,108 kWh to 5022 kWh per year. Figure 4: Energy generation and storage in a July week: (**a**) 90% self-sufficiency; (**b**) 100% self-sufficiency. Figure 5: Results at different ratios of self-sufficiency: (**a**) annual costs; (**b**) tradeoff between the annual and the emission costs. Figure 5b summarizes the tradeoff between the annual and emission costs when different ratios are considered. The annual costs would increase by 11.8%, 35.7%, 36.2%, 42.6%, and 94.0% (black bars) if the ratio of self-sufficiency increases to 60%, 70%, 80%, 90%, and 100%, respectively. However, the B&B achieves a 20% to 100% reduction in emission costs (green bars) when increasing the ratio. Therefore, B&B owners can choose the most suitable energy transition tradeoff based on the self-sufficiency ratio as the target to be achieved.