Design of a PV system with variations of hybrid system at Addis Ababa Institute of Technology

Abstract: This paper proposes a renewable power generation system for Addis Ababa Institute of Technology (AAiT). The aim of hybridizing renewable energy sources is that the main load shall be covered by the available solar energy source and other sources shall function as a complement when there is a deficiency in the main source. The aim of the system is to cover outdoor lighting, which is also designed in this report, at the campus of AAiT during night. Due to frequent power outages in Addis Ababa, Ethiopia, the PV system has been designed to provide enough electricity supply to cover most of the offices in the Administration Building at AAiT. The solar potential of the site is based on monthly average data of solar irradiation provided by NASA. The optimum angle to mount the PV modules is determined through simulations based on irradiation on a horizontal surface. The design of outdoor lighting is based on giving a suitable illumination dependent on what the area is used for after sunset. The PV system was dimensioned to supply enough energy to light the campus. Four backups to the PV system were examined to find the optimal solution: battery, diesel generator and the two hybrid systems with battery and diesel generator or grid. The configurations made to find the optimized system were modeled in The Hybrid Optimization Model for Electric Renewables (HOMER) software. The most cost-effective system was determined by finding the Net Present Cost (NPC) and the Cost of Energy (COE) of each setup. A sensitivity analysis was carried out for the two most suitable setups: battery and diesel generator as backup and battery and grid as backup. The variables included in the sensitivity analysis were: PV capital cost, diesel- and conventional electricity price. Based on simulation results, it was found that a PV system with battery and grid as backup would give the most profitable investment. 53% of the energy use required by the setup would come from solar energy, and the remaining 47% from the national grid that produces electricity through hydroelectric power. Thus, the renewable fraction would be 100%. It would also provide the institute with a sustainable power system. The setup has a NPC of $ 32 548 and COE of 0.127 $/kWh. The economic evaluation of the final setup included a study of forecasting the electricity kWh-price in Ethiopia. It was determined that the tariff price would be more than twice as high (233%) at the end of the PV system's lifetime (25 years) to equal today's export tariff which resulted in an annual increase of 3.45%. For a more reliable sensitivity analysis the annual cost of the investment was compared to the estimated costs based on an annual electricity increase of 6.90%. To find the payback time of the investment, simulations were performed in MATLAB. The payback time for the system would be reached within the lifetime of the system if the electricity tariff would increase by 6.90%. It was found that the payback time would occur after 22 years.