Nick Fetty | March 10, 2015

The old adage says that “two is better than one” and engineers at Iowa State University are studying whether this is true when it comes to the number of rotors on a wind turbine.

ISU aerospace engineering professor Hui Hu and aerospace engineering associate professor Anupam Sharma are studying ways to improve wind turbine efficiency. On many current models, the round-shape of the base of turbine blades reduces wind harvest by approximately 5 percent. Additionally, turbines that are downstream from others can lose 8 to 40 percent of energy generation.

“To try to solve these problems, we put a small rotor on the turbine,” Hu said in a news release. “And we found that with two rotors on the same tower, you get more energy.”

The research team has developed its dual-rotor turbine prototypes using 3D-modeling and other software applications. Through lab tests and computer simulations, the researchers saw an 18 percent increase in wind energy harvested.

Hu is testing his dual-rotor prototypes in ISU’s Aerodynamic/Atmospheric Boundary Layer Wind and Gust Tunnel to study power outputs, wind loads, and the physics of air flow on the different models. He has been assisted by postdoctoral research associate Wei Tian and doctoral students Zhenyu Wang and Anand Ozbay.

Sharma is focused on aerodynamic design of the dual-rotor models using high-fidelity computational fluid dynamics analysis and large eddy simulation. He has been assisted by doctoral students Aaron Rosenberg and Behnam Moghadassian.

Hu and Sharma were recipients of the Iowa Energy Center’s 2014 Renewable Energy Impact Award which provided them with $116,000 for their research. An additional three-year, $330,000 grant from the National Science Foundation will allow the researchers to continue their studies.