Comparative energy performance analysis of four wind turbines with counter-rotating rotors in steady-state regime

Abstract

In the worldwide effort to decarbonize the electricity generation, increasing the energy performance of renewable energy conversion systems is a continuing global concern and challenge for stakeholders. In this context, the paper presents the results of a comparative study on energy performance of four counter-rotating wind turbines of different types. In this regard, the authors propose a new reconfigurable structure of a counter-rotating wind system, able of operating in four distinct cases: with traditional electric generator (with fixed stator) or counter-rotating generator, with monomobile (torque adding) or bimobile (speed adding) speed increaser. These functional cases are obtained by the appropriate command of two intermittent clutches. A generalized algorithm for kinematic and static analytical modeling of the reconfigurable wind system in steady-state regime is proposed in the first part. Also, a new approach for optimizing the main design parameters, such as the ratio of wind rotor diameters, is detailed. The numerical simulations of the obtained closed-form model, for optimized value set of design parameters and various wind speed values, showed a slight energy advantage of using counter-rotating generators and monomobile transmissions, but accompanied by drawback of increased complexity. The main results of the paper, i.e. the new reconfigurable wind system concept and its analytical steady-state model of speeds, torques and efficiency, are useful for researchers and practitioner interested in developing optimized counter-rotating wind turbines.