Optimal hybrid energy storage for wind energy integration

Wind energy integration into the electric grid has been traditionally seen as a challenge due to its intermittent and variable nature. Power demand also fluctuates making the integration more difficult. Energy storage systems (ESS) are widely accepted as a viable but costly solution to balance between renewable power generation and power load. Various energy storage technologies, such as Li-ion, lead-acid batteries or flywheels, are in use for renewable energy integration. These technologies have different energy and power capacity costs, as well as different round-trip efficiencies. However, up-to-date a combination of different energy storage technologies taking into account their round-trip efficiencies has not been considered at the utility scale. In this paper, we propose how to design a hybrid energy storage for integration of wind power into systems with limited or no connectivity to the power grid. Moreover, we give a control strategy to operate such hybrid ESS taking into account all relevant system parameters. Our simulation results show that hybrid systems substantially outperform single-technology systems of the same capital cost allowing for more efficient use of renewable energy and better balance between power demand and generation.