NREL Wind Turbine Design Codes Certified

Through a joint effort by the NREL and Germanischer Lloyd (GL) of Hamburg, Germany, the world's foremost certifying body for wind turbines, both codes were approved for calculating onshore wind turbine loads for design and certification.

Although many U.S. wind turbine manufacturers have relied on these design codes to estimate the design loads of their turbines in the past, until recently the codes were not accepted by certifying agencies in Europe. To have turbines certified, manufacturers had to re-evaluate designs using European codes or hire European consultants, a process that increased the time and cost of certifying turbines.

The FAST code (for Fatigue, Aerodynamics, Structures, and Turbulence) is a comprehensive aeroelastic simulator capable of predicting both the extreme and fatigue loads of two- and three-bladed horizontal-axis wind turbines.

ADAMS (Automatic Dynamic Analysis of Mechanical Systems), developed by MSC Software, is a general-purpose, multibody-dynamics code with unlimited degrees of freedom that also is used to model robots, satellites, and cars. ADAMS is slower than FAST, but more versatile. FAST is limited to most standard types of horizontal-axis wind turbines; ADAMS with AeroDyn can model almost any kind of horizontal-axis wind turbine. Both require the AeroDyn subroutine library to model aerodynamics.

To gain acceptance of the codes, NREL and GL ran a comparison between FAST, ADAMS, GL's DHAT, and Garrad Hassan's GH Bladed, a widely accepted European code. The latter two codes are similar in design philosophy to FAST. NREL and GL modeled two turbines. To exercise different features of the codes, they chose different types of turbines. The project started with simple comparisons and grew in complexity as the participants gained confidence that all the codes were using the same properties for the models. Results of the comparison will be published in an NREL technical paper and presented by Marshall Buhl, a senior engineer at NREL, at the 2006 American Society of Mechanical Engineers' Wind Energy Symposium in Reno, Nev.

In its report, GL stated that the comparison showed good agreement between the codes. GL granted NREL a certificate for FAST and ADAMS stating that the codes can be considered suitable programs for the calculation of onshore wind turbine loads for design and certification.

For more information about the FAST and ADAMS design codes visit NREL's National Wind Technology Center's Web site at the following link.