Grid Connected Hybrid Solar and Diesel Generator Set: A Cost Optimization with HOMER

Extensive increases in electricity cost added to the numerous power outages encountered in developing countries has led to the deployment of hybrid energy supplies that mainly ensure continuity of power supply while attempting a reduction of electricity generation cost. This paper, specifically deals with the cost optimization of electricity generation from a grid connected hybrid solar and diesel generator. An electrical audit was first conducted on a selected building: the Electrical Block of Accra Technical University. The load estimate led to a total energy of 234 kWh for all electrical gadgets with the exception of the air-condition systems. The estimate was used to design the hybrid system with HOMER software that resulted in a total capacity of 115 kW and a levelized cost of electricity of 0.472 $/kWh taking into consideration no power outage in the year. Furthermore, the proposed hybrid system was made of a grid connected solar system that supplies the full load with the exception of the air-condition systems while the National Grid is used to cover the rest. In situation of power outages, the Generator Set takes over the National grid while the solar is still connected to the Grid. This mechanism was simulated and the cost of electricity in absence of the grid was estimated at 1.496 $/kWh. A general cost of electricity taking into consideration 90% ON period of the grid against 10% Off period of the grid per year, was estimated to 0.574 $/kWh. Besides, the proposed system produced savings in emission of carbon dioxide, 26.42 kg/year, sulfur dioxide, 115 kg/year and Nitrogen oxides, 56 kg/year. Finally, the system yielded a very good payback period of 10.43 years with regard to a lifetime of 25 years