The development of a techno-economic model for the assessment of the cost of flywheel energy storage systems for utility-scale stationary applications

Abstract Flywheel energy storage systems are increasingly being considered as a promising alternative to electro-chemical batteries for short-duration utility applications. There is a scarcity of research that evaluates the techno-economic performance of flywheels for large-scale applications. Evaluating the capital cost, levelized cost of storage, and scale factor is crucial to make an informed decision in future development and deployment of the technology. This study, therefore, focuses on developing a bottom-up techno-economic model to design system components and to evaluate the total investment cost and levelized cost of storage of flywheels with a capacity of 20 MW/5 MWh for frequency regulation. Two rotor configurations were considered: composite rotor flywheel and steel rotor flywheel. The total investment costs of the composite rotor and steel rotor flywheel storage systems are $25.88 million and $18.28 million, respectively. The corresponding levelized costs of storage are $189.94/MWh and $146.41/MWh. The model results are highly sensitive to the cost of the rotor material, discount rate, factor of safety, number of cycles per year, and tensile strength of the rotor material. The ranges obtained in the uncertainty analysis for the levelized cost of storage are $122.08-$253.52/MWh and $108.63-$187.64/MWh for the composite rotor and steel rotor flywheel storage systems, respectively.