Optimization of an Off-grid hybrid PV-Wind-Diesel system with different battery technologies - Sensitivity Analysis

Abstract:
The rapid advancement of technology has resulted in very wide services especially in the mobile telecommunications. However most of the base stations locate in remote areas and far from the utility grid. This paper presents a solution to power these stations through renewable energies at minimal cost. The approach to this big challenge is presented here, where the storage system (batteries) plays the central role in such systems. This paper shows the modelling and optimization of an off-grid system consisting of photovoltaics and wind as energy sources, batteries to store the excess generated energy and a diesel generator as a back-up system. Combination of three different battery technologies as storage system is investigated: lead-acid, Li-ion and redox-flow batteries. To control both the power flow among the system components and the battery charging and discharging processes, an energy management system (EMS) is needed. It calculates the batteries state of charge in every time step and decides which battery technology is active (is being charged or discharged) as well as when the diesel generator has to be started. The chief objective is to operate each battery in a way that minimises the ageing for all batteries. The main constraint that has to be satisfied is that the load should always be supplied with electricity. The suggested system is optimized to cover the load of a telecommunication base station using Genetic Algorithm. The system performance over 20 years is evaluated and the total costs are determined. The optimization has been also done for a site in Quneitra- Syria which has very good solar radiation that allows for the comparison between two countries, as the weather data in the two coun-tries differ greatly (different weather data). Furthermore, sensitivity analyses are done for different battery prices, interest rates and cost of carbon emissions.