Field test of a coaxial dual rotor vertical axis turbine

Abstract

Tidal current technology offers one of the most promising sources of marine power. Vertical axis turbines have some unique advantages over other types of machine, but there are a number of problems that hinder their development, notably their poor self-starting performance and high cost. In order to address these issues, a coaxial dual rotor vertical axis turbine with 60° shift angle has been developed and field tests have been carried out in Dalian China to evaluate the performance of the prototype. According to the test results, the range of the prototype’s tip speed ratio was from 1.5 to 3.4 with an optimum of 1.8. The capacity factors during the tidal cycle (about 6.5 h in the test site) of the flood tide and ebb tide were 23.9% and 17%. The system efficiency can reach about 28% when the current velocity is about 1.5 m/s. The side wall effect and velocimeter deviation are also analyzed. The main range of self-starting current velocity of the prototype is from 1.1 to 1.3 m/s. The probability that the turbine started spontaneously at current velocity below 1.4 m/s is 96%. The results show that the coaxial dual rotor turbine performs well on energy efficiency and self-starting performance without significant cost implications.