Currently, difficulties such as the depletion of fossil fuel resources and the associated environmental pollution have driven the rise of other energy systems based on green energy sources. In this research, modeling and a viability study of grid-connected and islanded photovoltaic (PV) power systems for supplying the residential load in Mekelle City, Ethiopia, were carried out considering the country’s emerging utility tariff plan for 2021 and beyond. The technical viability of the proposed supply option was analyzed using PVGIS, PVWatts and HOMER Pro tool, while the economic and environmental optimization aspects were carried out using HOMER Pro. Sensitivity analyses and output comparisons among the three renewable energy simulation tools are presented. The results showed that under the consideration of an incremental electricity tariff plan (up to 2021), the analyzed cost of energy of the grid/PV system is around 12% lower than the utility grid tariff. Moreover, we also found that by taking the continuous global solar PV cost reduction into account, the cost of energy of the modeled islanded operation of solar PV power units totally broke the grid tariff in Ethiopia after 2029 based on the tariff for 2021 and well before with the expected escalation of the grid tariff on an annual basis. The technical performance of the system realized through PVGIS and PVWatts was almost comparable to the HOMER Pro outputs. Thus, this investigation will offer a clear direction to the concerned target groups and policy developers in the evolution of PV power supply options throughout the technically viable locations in the country.

Ethiopia is well endowed with solar energy resources with daily average radiation ranging from 4.5 to 7.5 kWh/m2/day. The significant electricity consumption of the country is reliant on hydropower. This dependence on hydropower makes the country susceptible to weather and climate changes, such as droughts, which can lead to reduced water levels in hydropower reservoir and reduced electricity generation. The application of solar floating photovoltaic (FPV) in the existing hydro reservoir would provide solar electric power to support hydropower generation especially during dry periods, and decrease evaporation losses. This implementation also has the cascading effect of increasing the solar power generation from the PV system by reducing the panel temperature through efficiency gain while saving the land requirement for installing the same PV system. Especially for countries like Ethiopia where agriculture is the key source of economy, optimal usage of land is very important. Thus, in this research, a techno-economic comparative analysis of 4MW Grid-tied FPV and ground-mounted PV system on Gilgel gibe I reservoir in Ethiopia for supplying the auxiliary load of the generation plant is done. The results showed that the proposed FPV system has 6.9% more electricity generating capacity than land-mounted PV system and saves 74,400m3 of water from evaporation annually. The FPV plant will also save the land cost burden, and results the levelized cost of energy (COE) 0.043$/kWh, which is 15.7 % less than land-mounted PV systems. In another way, the proposed FPV system indicated a positive impact on the environment by reducing 993 tons of greenhouse gas emission annually. Thus this research results will offer a clear directions for the concerned stockholders to implement FPV technology on the Ethiopian hydro reservoirs.

The authors wish to make the following corrections to their paper