The effects of inertia on a straight-bladed vertical axis wind turbine

Abstract

The application of vertical axis wind turbines (VAWTs) is gaining increasing attention, particularly in urban areas with highly turbulent wind conditions. The airfoil blade is a critical component of a wind turbine which determines its overall performance. However, Darrieus turbines often suffer from self-starting issues which are closely related to inertia. Since blade inertia is influenced by their material, lightweight materials are typically used for blade manufacture. Nevertheless, experimental study on the blade inertia of VAWTs remain limited. This paper investigates the effects of blade inertia on a straight-bladed VAWT. A two-bladed NACA0018 VAWT with a 700 mm diameter and an aspect ratio of 1 was fabricated and tested in a wind tunnel at an incoming wind speed of 5.61 m/s. To compare the effects of inertia, two different blade coatings—epoxy and thin film were used. The difference in the coating material density resulted in varying blade inertia. The study focused on self-starting behavior, maximum rotational speed, and power output. The coefficient of power (CP) was analyzed across a wide range of tip speed ratios (TSRs) under various load conditions. The results indicate that as inertia increases, the turbine takes longer to reach its maximum rotational speed, exhibiting lower angular acceleration and greater fluctuation in the transient state before stabilizing. Additionally, the VAWT with 2.3 times higher blade inertia exhibited lower maximum rotational speed and power output. In contrast, the turbine with lower blade inertia achieved a 30% higher rotational speed and a 69.75% increase in maximum CP.

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ORCID for Andrew Cruden: orcid.org/0000-0003-3236-2535

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