ARS | Publication request: Evaluation of airfoils for small wind turbines

Submitted to: Windpower
Publication Type: Proceedings
Publication Acceptance Date: July 1, 2007
Publication Date: August 1, 2007
Citation: Cagle, D., Mays, A., Vick, B.D., Holman, A. 2007. Evaluation of airfoils for small wind turbines. In: Proceedings of the AWEA Windpower 2007 Conference, June 3-6, 2007, Los Angeles, California. 2007 CD-ROM.

Interpretive Summary: Field testing of a wind-electric water pumping system on a remote well has shown that a submersible pumping system powered by a 1.5 kW wind turbine was not a good choice for livestock watering in the Great Plains due to low volume of water pumped during the summer low wind months. This was attributed to inefficient wind turbine blade designs. Conclusions of the testing indicated that the wind-electric system could be improved if the turbine could perform better in low winds. A new set of blades were made and tested on the wind turbine used in the field trial mentioned above to support these conclusions. The new blades incorporated more advanced design than the ones used in the previous trial. Results from this test have shown that the performance of the system has been greatly improved. The wind turbine performed better in low winds and this has resulted in double the amount of water pumped during the summer months when compared to the previous test. These improvements also imply that the water requirements for 80 head of cattle can be achieved during the low wind months in the Great Plains. It has been shown by implementation of advanced blade manufacturing techniques such as improved airfoil shapes, variable chord distributions, and variable twist distributions that the overall performance of small wind turbines can be improved significantly. Results also show that by using these techniques, the wind-electric water pumping system can effectively compete with a mechanical wind mill of similar rotor diameter.

Technical Abstract: A new set of blades have been designed, fabricated, and tested at the United States Department of Agriculture-Agricultural Research Service-Conservation and Production Research Laboratory in Bushland, Texas in an attempt to improve the overall performance of small (1-10 kilowatt) wind turbines. The new turbine blades feature more advanced NREL S822 and S823 airfoils, a linear chord distribution, and a near Glauert twist distribution. The blades were fabricated using a hand lay-up method in a single mold. The rotor blades were adapted to a 1.5kW wind turbine for performance and reliability testing. These new blades have demonstrated a lower cut-in wind speed as well as higher energy yield and efficiency than that of the original blades on the 1.5kW wind turbine. Peak coefficient of power for the system was 0.30 for the Bergey blades and 0.41 for new blades. The annual water volume pumped was estimated to double with the new airfoils.