Size optimization of a hybrid PV/wind/diesel/battery power system for reverse osmosis desalination

This study was to find the optimal configuration for an independent renewable energy system for reverse osmosis (RO) desalination. The objective was to find the lowest levelized cost of energy (LCOE), with power reliability as the constraint. A genetic algorithm was used to solve the nonlinear integer programming program. A site with brackish groundwater in Arizona, USA was selected. The capacity of the RO system was 18.93 m(3)/d (5,000 gal/d), requiring a constant power consumption of 3.95 kW. Two scenarios were considered in terms of diesel generator (DG) allowed running time. The results showed that the optimal configuration was a hybrid photovoltaic/wind/diesel/battery system with 0.56 USD/kWh and the corresponding levelized cost of water 3.84 USD/m(3), when the DG can run in any hour every day. The optimal solution was a hybrid wind/photovoltaic/battery system with 0.69 USD/kWh and 4.48 USD/m(3), when the DG can run between 9 am and 9 pm every day for noise control. Both the two LCOWs were about half of the 7.9 USD/m(3) currently paid by residents that live in the area. Sensitivity analyses showed the LCOE was fairly insensitive to photovoltaic panel tilt angle over a range for both the two configurations.