Optimal hybrid pumped hydro-battery storage scheme for off-grid renewable energy systems

Abstract

The development of energy storage systems paves the way towards a high integration of renewable energy sources in the electricity generation sector. Considering above, this paper introduces a new energy management strategy to efficiently coordinate a hybrid energy storage system based on pumped hydro storage (long term bulk storage) with batteries (short term, more flexible). For the purpose of this analysis, hourly time series of irradiation, wind speed, temperature and real measured load (characteristic for farmstead) covering one year were gathered for the selected site in Algeria. The optimal size of the system is determined based on a multi-objective optimization using a grey wolf optimizer implemented in MATLAB software. The results indicate that the hybrid storage system enables achieving higher reliability at lower cost in comparison to a system with single storage technology. The use of hybrid storage also reduces the curtailment of renewable generation. Further findings reveal that the cost of an optimal energy supply system with 97.5% reliability is 0.162 €/kWh, 0.207 €/kWh and 1.462 €/kWh for hybrid storage, battery and pumped storage, respectively. However, sensitivity analysis shows that the optimal hybrid storage configuration is less resilient when changes in irradiation/temperature/load are considered. This indicates that special actions (upscale of installed power) must be undertaken to avoid lower performance of hybrid storage systems. In summary, the hybrid storage system seems to be better sized for consideration in optimized solar/wind conditions, but by avoiding oversizing they are less resilient to future potential changes in renewable energy availability.