Novel cyclic blade pitching mechanism for wind and tidal energy turbine applications

Jubilee Prasad Rao, Francisco J. Diez

Research output: Contribution to journalArticlepeer-review

1 Scopus citations


A vertical axis drag-based turbine is proposed that allows for an improved performance by feathering its blades during recovery strokes to eliminate adverse blade forces. The turbine blades resemble flat plates and pitch by 90 between the two turbine strokes using a novel dual-cam mechanism. This passive mechanism orients the blades vertically during the drive stroke for maximum effective area and horizontally for minimum effective area during the recovery stroke. This allows maximizing the positive drive stroke force and minimizing the recovery stroke losses, in turn maximizing the net energy capture and the turbine performance. It is called the cyclic pitch turbine, and a mathematical model is developed that predicts the turbine performance. It shows that the turbine is self-starting for all orientations and has a higher and more uniform static torque coefficient than the popular Savonius turbine. The dynamic analysis also indicates a higher performance, and the predicted values for torque and power coefficients match very closely with those from water channel and wind tunnel experiments on a prototype. Results of testing several blade shapes indicate that airfoil section blades with long and narrow continuous shapes that have less area towards the blade’s tip result in higher performance.

Original languageEnglish (US)
Article number3328
Issue number12
StatePublished - Dec 1 2018

All Science Journal Classification (ASJC) codes

  • Control and Optimization
  • Energy (miscellaneous)
  • Engineering (miscellaneous)
  • Energy Engineering and Power Technology
  • Electrical and Electronic Engineering
  • Fuel Technology
  • Renewable Energy, Sustainability and the Environment


  • Cyclic blade pitching
  • Drag-based wind turbines
  • Mathematical modeling
  • Power performance testing
  • Recovery stroke drag
  • Vertical axis wind turbines
  • Wind tunnels


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