A review of available solutions for enhancing aerodynamic performance in Darrieus vertical-axis wind turbines: A comparative discussion

Darrieus vertical-axis wind turbines (VAWTs) face challenges related to startup performance, relatively lower power output, and significant cyclic torque fluctuation amplitude. Despite numerous proposed solutions, these issues remain unresolved, hindering the full realization of VAWT potential. This study critically evaluates the effectiveness of existing solutions in addressing these challenges, aiming to identify solution strengths, weaknesses, and associated research gaps. To this aim, the solutions are categorized into five groups: turbine configuration modification, blade shape modification, passive and active techniques, and flow augmentation. The performance desirability of the solutions is then evaluated based on defined criteria reflecting their ability to address the aerodynamic challenges. Additionally, different practical aspects of the solutions are considered to assess their applicability in real-world situations. The findings reveal that while some designs show promise in addressing specific challenges, they often introduce new issues of poor off-design performance and practicality concerns such as increased complexity, maintenance requirements, and cost. This highlights a trade-off between practicality and performance desirability, reflected in the relatively low Technology Readiness Levels (TRLs) of the available solutions. This finding emphasizes the need to investigate the root causes of existing challenges, which are tied to the complex aerodynamics inherent in VAWT systems. The insights and recommendations provided aim to guide future Darrieus VAWT development by balancing between performance improvements and practical feasibility.