Feasibility assessment of electromechanical batteries for electric vehicles

We have assessed the current feasibility of substituting multi-shell composite flywheel motor-generators (electromechanical batteries) for electrochemical batteries in electric vehicles. We present two conceptual designs using the latest materials and technology. Feasibility was evaluated in terms of performance predictions based upon consistent and optimistic analytical models of components for these conceptual designs. We review various approaches for performance improvement. The most challenging issues are capital cost and energy storage performance. Energy storage per unit cost favors the electrochemical battery. The power density, specific power, efficiency, and turn-around efficiency can be higher for the electrochemical battery than for projected electrochemical batteries of the future. We conclude that for electric vehicles, electromechanical batteries may be best suited for a hybrid application with electrochemical batteries. This combines the high specific power, power density, and turn-around efficiency possible with the electrochemical battery with the low cost of the electrochemical battery.