Optimization and Energy Management of Hybrid Photovoltaic-Diesel-Battery System to Pump and Desalinate Water at Isolated Regions

This research work aims to provide detailed feasibility, a techno-economic evaluation, and energy management of stand-alone hybrid photovoltaic-diesel-battery (PV/DG/B) system. The proposed system can be applied to supply a specific load that is far away from the utility grid (UG) connection, and it is located in Minya city, Egypt, as a real case study. The daily required desalinated water is 250 m
³
. The total brackish water demands are 350-500 m
³
and 250-300 m
³
of water in summer and winter seasons, respectively. Two different sizes of reverse osmosis (RO) units; RO-250 and RO-500, two energy control dispatch strategies; load following (LF) and cycle charging (CC); two sizes of DG; 5 kW and 10 kW are considered in the case study. The cost of energy, renewable fraction, environmental impact, and breakeven grid extension distance are the main criteria that have been considered to determine the optimal size of PV/DG/B to supply the load demand. HOMER
^®
software is used to perform the simulation and optimization. For this case study, the minimum cost of energy and the minimum total present cost are 0.074 $/kWh and 207676 $, respectively. This is achieved by using a RO-500 unit and a LF dispatch control strategy. The related sizes to the best option of PV/DG/B are 120 kW PV array, 10 kW DG, 64 batteries, and 50 kW converter. A comparison with grid extension and installing stand-alone diesel generation is also carried out. The results of comparison have confirmed that the grid connection is better than all considered options using the RO-250 unit. However, for the RO-500 unit, all options of hybrid PV/DG/B are more economically feasible compared with grid connection, and the best cost-effective option is the one including LF strategy with 10 kW DG. Stand-alone diesel generator produces 119110 kg/year and 117677 kg/year of CO2 respectively for RO-250 and RO-500.