Numerical Investigations on the Effects of Inertia on the Startup Dynamics of a Multibladed Savonius Wind Turbine

Taimoor Asim (), Ityona Amber, Dharminder Singh and Muhammad Salman Siddiqui
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Taimoor Asim: School of Computing, Engineering and Technology, Robert Gordon University, Aberdeen AB10 7GJ, UK
Ityona Amber: School of Computing, Engineering and Technology, Robert Gordon University, Aberdeen AB10 7GJ, UK
Dharminder Singh: Department of Mechanical Engineering, Glasgow Caledonian University, Glasgow G4 0BA, UK
Muhammad Salman Siddiqui: Faculty of Science and Technology, Norwegian University of Life Sciences, 1430 Ås, Norway

Energies, 2025, vol. 18, issue 7, 1-14

Abstract: The startup dynamics of wind turbines have a direct impact on their cut-in speed and thus their capacity factor, considering highly transient winds in urban environments. Due to the complex nature of the startup dynamics, the published research on it is severely lacking. Unless the startup dynamics and cut-in speed of a wind turbine are known, it is difficult to evaluate its capacity factor and levelized cost of energy (LCoE) for commercial viability. In this study, a Savonius vertical-axis wind turbine (VAWT) has been considered and its startup dynamics evaluated using numerical techniques. Moreover, the effects of turbine inertia, arising from bearing frictional losses, generator load, etc., on the startup dynamics have been studied. Advanced computational fluid dynamics (CFD)-based solvers have been utilized for this purpose. The flow-induced rotation of the turbine blades has been modeled using a six degree of freedom (6DoF) approach. Turbine inertia has been modeled using the mass moment of inertia of the turbine rotor and systematically increased to mimic the additional inertia and losses due to bearings and the generator. The results indicate that inertia has a significant impact on the startup dynamics of the VAWT. It was observed that as the turbine inertia increased, it took longer for the turbine to reach its steady or peak operational speed. Increasing the inertia by 10%, 20% and 30% increased the time taken by the turbine to reach its peak rotational speed by 13.3%, 16.7% and 23.2%, respectively. An interesting observation from the results obtained is that an increase in turbine inertia does not change the peak rotational speed. For the Savonius rotor considered, the peak rotational speed remained 122 rpm, and its tip speed ratio (TSR) remained 0.6 while increasing the turbine inertia.

Keywords: Savonius rotor; vertical-axis wind turbine (VAWT); computational fluid dynamics (CFD); startup dynamics; six degree of freedom (6DoF); turbine inertia (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2025
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