NREL airfoil families for HAWTs [report]

J L Tangler, D M Somers
1995 unpublished
The development of special-purpose airfoils for horizontal-axis wind turbines (HA WT�) began in 1984 as a joint effort between the National Renewable Energy Laboratory (NREL), formerly the Solar Energy Research Institute (SERI), and Airfoils, Incorporated. Since that time seven airfoil families have been designed for various size rotors using the Eppler Airfoil Design and Analysis Code. A general performance requirement of the new airfoil families is that they exhibit a maximum 1ift coefficient
more » ... um 1ift coefficient ( '1,rnaJ which is relatively insensitive to roughness effects. The airfoil families address the needs of stall -regulated, variable-pitch, and variable-rpm wind turbines. For stall-regulated rotors, bett er peak-power control is achieved through the design of tip airfoils that restrain the maximum 1ift coefficient. Restrained maximum 1ift coefficient all ows the use of more swept disc area for a given generator size. Also, for stall-regulated rotors, tip airfoils with high thickness are used to accommodate overspeed control devices. For variable-pitch and variable-rpm rotors, tip airfoils having a high maximum lift coefficient lend themselves to lightweight blades with low solidity. Tip airfoils having low thickness result in less drag for blades having full -span pitch control Annual energy improvements from the NREL airfoil families are projected to be 23% to 35% for stall regulated turbines, 8% to 20% for variable-pitch turbines, and 8% to 10% for variable-rpm turbines. The improvement for stall-regulated turbines has been verified in field tests.
doi:10.2172/10106095 fatcat:myoizuexcbcy5f73a65oabyniu