The effect of axial distance on dual rotor wind turbine's performance

Dual-rotor wind turbine (DRWT) is the development of wind turbine design with the addition of rotors placed on the same shaft. The addition of rotors causes the turbine to improve its performance. Experimental research was conducted to determine the performance that can be achieved by the DRWT type using the wind tunnel module. The test was carried out on three variations of the axial distance ratio of 0.08; 0.12; and 0.16. Comparing with a singlerotor wind turbine (SRWT), the DRWT type gives better performance. The DRWT type can rotate at a lower tip speed ratio than SRWT type. The power generated by the DRWT type is increasing up to 100% at tip speed ratio of 0.08 in all axial distance ratio while SRWT type can not rotate at tip speed ratio of 0.8. The DRWT type with a ratio of 0.12 is able to reach the highest coefficient of power which is 0.35 at tip speed ratio of 1.2. There was an increment of 53.7% in mechanical power from the SRWT type under the same conditions. Furthermore, the numerical method was used to know the flow phenomenon in the two rotors. The wake flow behind the first rotor causes backflow that give a loss to DRWT's performance but still has enough energy that can be extracted by the second rotor and converted to mechanical power. Greater energy conversion will reduce wasted wind energy.