A comparative study based on a techno-environmental-economic analysis of some hybrid grid-connected systems operating under electricity blackouts: A case study in Cameroon

Hybrid grid-connected systems appear as promising concept to tackle the problem of electricity blackouts in many localities around the world. In this paper four different options of backup systems connected to the grid under severe electricity blackouts are studied and compared for household energy supply in developing countries. The far north region of Cameroon has been chosen as case study. A double objective optimization based on firefly algorithm has been performed for the optimal sizing of the proposed systems. The system reliability, the investment cost, the renewable energy penetration and the carbon dioxide emissions are the main comparative indexes considered. The optimal configuration of each system corresponding to the loss of power supply probability of 0% is determined by simulation based on the proposed operational strategies. For an energy demand of 46418.100 kWh/year and a project lifetime of 24 years, the optimal levelized cost of energy is 0.220 $/kWh for the Photovoltaic/battery/grid-connected system, 0.338 $/kWh for the Photovoltaic/diesel/grid-connected system, 0.407 $/kWh for the diesel/grid-connected system, and 0.389 $/kWh for the diesel/battery/grid-connected system. For a short term investment (less than 7 years), the diesel/grid-connected system is economically the best option, but for a long term investment (7 years and above), the Photovoltaic/battery/grid-connected appears as the best option. Moreover, for a long term investment (from a project lifetime of 11 years and above), the Photovoltaic/battery/grid-connected system (76320 $ of total investment in 11 years) could be competitive to the only grid energy supply without electricity blackouts (76590 $ of total investment in 11 years). The annual average percentage of the renewable energy penetration is 64.84 % for the Photovoltaic/battery option, 44.59 % for the PV/diesel option, 0 % for the diesel and the diesel/battery options. The direct carbon dioxide emissions is 0 kg/year for the Photovoltaic/battery option, 9790 kg/year for the Photovoltaic/diesel option, 13797 kg/year for the diesel and the diesel/battery options. However when including the manufacturing emissions the results are 657729 kg/year for the Photovoltaic/battery option, 13610 kg/year for the Photovoltaic/diesel option, 16538 kg/year for the diesel option, and 606091 kg/year for the diesel/battery option. The sensitivity analysis revealed that the studied systems are more attractive when increasing the project lifetime and reducing the fuel price, the discount rate and the capital cost of the backup system components. All the obtained results are very useful for decision making.