## 7 Conclusions  
Rural electrification in the remote regions of Ethiopia through grid extension is not economically feasible because of the dispersed population, difficult geographic terrain and low load demand in the existing conditions. On the other hand, delivering electricity from SHS and diesel generators only for lighting for a short period of time will not bring the expected economic development. Having these controversies in mind, in this study, in addition to lighting loads, sewing machines, flourmills, water pumps, and refrigerators for preserving fishery products were considered in the load estimation of Kibran Gabriel island.  
Based on the estimated load demand and the environmental conditions of the island, stand-alone diesel, PV/battery, PV/wind/battery, PV/diesel/battery, and PV/wind/diesel/battery systems were considered in the analysis. The following concluding remarks are drawn.  
* Of all the minigrid systems considered in this study, the PV/diesel/battery system, having a size of 25 kW of PV, 10 kW of DG, and 40 batteries of 1 kWh each is the optimal minigrid system, with LCOE of USD 0.175/kWh, NPC of USD 119,139, and RF of 86.4%. Relatively, it is the lowest cost system among the considered configurations.
* Compared to the base case stand-alone diesel system (LCOE of USD 0.346/kWh, NPC of USD 235,734), the optimal PV/diesel/battery system will reduce pollutant emissions by 33,102 kg/yr.
* In addition to PV/diesel/battery system, the PV/battery, PV/wind/battery, and PV/wind/diesel/battery systems are economically feasible compared to the stand-alone diesel system. However, the initial investment cost of the stand-alone diesel system is relatively the lowest.
* According to the BGED analysis, grid-extension to the island within the specified project lifetime is extremely costly compared to all the proposed options considered in this study.
* Once the optimal configuration is determined, the optimal minigrid sensitivity for the variations of GHI, diesel price, and load consumption was considered in the sensi  
Figure 19: Total fuel usage and LCOE related to load variations.  
tivity analysis. The new optimization results due to the variations of the sensitivity parameters were modified to LCOE of USD 0.179/kWh, NPC of USD 151,468 and RF of 69.1%. These optimization results showed that the system will operate reasonably well with the variations of GHI, diesel price, and load consumption. However, the impacts of renewable energy resources on the reliability and quality of power, and refining the estimated loads for practical implementation will be the subjects of future works.  
Conceptualization, C.-C.K. and T.M.B.; methodology, T.M.B. and C.-C.K.; formal analysis, T.M.B. and C.-H.W.; resources, C.-H.W., C.-C.K. and T.M.B.; writing--original draft preparation, T.M.B.; writing--review and editing, C.-H.W. and C.-C.K.; supervision, C.-C.K. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
Not applicable.  
The freely available data can be accessed through the indicated references whereas the remaining parts can be obtained from the corresponding author upon the reasonable request.  
Supports for this research from Ministry of Science and Technology of the Republic of China, and Bahir Dar Energy Center are gratefully acknowledged.  
The authors declare no conflict of interest.