Flexible profile vertical axis turbine concept

The installation of tidal turbines for exploitation of the significant tidal and ocean current energy resources represents an important opportunity for generating renewable energy and further development of the technology. The reliability of the entire s ystem plays a central role in the design, construction and installation of competitive tidal turbines that can be used for commercial applications. Concepts and technology currently in use or pilot tested by the tidal community is in general still inad equate for full-scale commercial applications. To summarize design work, testing and verify the expected behavior and the dynamics of the newly developed tidal turbine concept, this PHD will review functional principles, design, tests and develop mathema tical models in order to predict and study functionality aspects and optimize the hydrodynamic performance and establish a basis for the future designs, test and optimization. The focus of this PhD project is further to develop a novel method capable of analyzing fatigue life prediction so that system errors can be prevented. Previous tests of a full-scale pilot of this novel turbine concept with flexible profiles in a controlled river environment, showed up to 37% turbine efficiency at a near to consta nt rpm independent of incoming current velocities.

To date, full-scale vertical axis turbine concepts have not been used for hydrodynamic applications, and all test concepts have fixed static wing profiles. A novel vertical axis turbine has been designed, with flexible double cambered profiles and pivot a nd spring arrangements that enable a passive pitching action and profile flopping motions, similar to movements in aquatic creatures. A full-scale pilot turbine has been tested in a controlled river environment in Norway, demonstrating self-starting capac ity at low water speeds, high efficiency (up to 37%), and reduced torque vibration resulting in good mechanical fatigue characteristics. The most critical R&D challenges for the development of this type of turbine include design and profile and turbine te sting that can be based on in-silico analytical tools to assess accurately turbine performance and dynamic forces. This is important in particular with respect to addressing rotational rippling effects and mechanical fatigue in all constructional elements . The study will therefor evaluate several theoretical analytical models and concluded and developed an accurate model to be used for calculating hydrodynamic performance and instant forces as a function of the azimuth angel. Hydrodynamic performance of Darrieus type vertical axis turbines depends on their solidity, tip speed ratio, and profile. For the tested flexible profile vertical axis pilot turbine, increasing incoming water flow (0.79, 1.18, 1.55 m/s) was correlated with a slight increase in th e turbine RPM (3.7, 4.2, 4.7) and a decrease in the TSR (2.21, 1.68, 1.4) and efficiency (37, 25, 20%). These aspect versus the spring loaded pivoting flexible profile feature should be described and analysed. Concept field developments for river and ti dal application will be described and cost estimated in the study The results of this project are expected to facilitate commercialization of this turbine for river, tidal, and ocean current applications.