No abstract

Flywheel Energy Storage Systems (FESS) present an environment-friendly solution for storing and utilizing solar energy; however, voltage and current frequent fluctuations in solar module photovoltaic (PV) systems limit the efficiency of the FESS. In this paper, a method is proposed for the duty cycle selection of the bi-directional converter of the FESS. The converter's function is to regulate and maintain the harnessed solar energy input to the FESS. The solar module system is first modeled to determine its maximum power point (MPP) voltage and current output. The developed model is then validated experimentally by field-testing the power and energy output. The solar module model has an average percent difference of 12% compared to the field-testing results. Moreover, the FESS and the bi-directional converter are separately modeled and then integrated to determine the FESS power output, efficiency, and flywheel rotational speed. The resulting FESS efficiency is 80% which is 14% higher than the efficiencies of FESS for off-grid PV applications available in literature. The developed duty cycle selection of the bi-directional converter will aid towards the development of commercial FESS for off-grid systems.