Optimal sizing of hybrid PV and wind energy system with backup of redox flow battery to postpone grid expansion investments

In this study, economical options to meet the load demand of Hormoz Island as a green Island in future years, located in Iran, are investigated. For this purpose, construction of a new undersea transmission line (UTL) and design of a grid-connected hybrid renewable energy system (RES) are selected as two possible options. Therefore, the optimization problem is modeled as a minimization of cost function including the investment, replacement, operation, and maintenance costs of components, carbon tax, and cost of purchased power from the upstream network as well as the cost of loss of load. It is notable that the grid-connected hybrid RES consists of photovoltaic (PV) and wind energy systems with consideration of redox flow battery storage. The optimization problem is simulated for a 20 year planning horizon subject to technical and geographical constraints of RES. To simulate the problem, the annual hour-based data of wind, solar radiation, and load demand of Hormoz Island are used. Also, wind energy potential of the region is used for the selection of the best turbine for this island. Moreover, an imperialist competitive algorithm and an improved particle swarm optimization algorithm are applied to find the best size and design of the hybrid RES and also the best time to use the RES and the new UTL. Three different scenarios for optimum hybrid RES designing are determined to consider the effects of using the hybrid system to postpone the grid expansion investments. Two of these scenarios have 20 year planning horizon, and one of them optimizes the system for a special year with a specific predicted load demand. The obtained results revealed that the wind/PV/vanadium redox flow battery hybrid system is the best configuration, where the new UTL will be constructed in 2020 with zero load energy shortage.