Fabrication, Integration and Initial Testing of a SMART Rotor

Abstract

EDUCING ultimate and oscillating (or fatigue) loads on the wind turbine rotor can lead to reductions in loads on other turbine components such as the drive train, gearbox, and generator. This, in turn, is expected to reduce maintenance costs and may allow a given turbine to user longer blades to capture more energy. In both cases, the ultimate impact is reduced cost of wind energy. With the ever increasing size of wind turbine blades and the corresponding increase in non-uniform loads along the span of those blades, the need for more sophisticated load control techniques has produced great interest in the use of aerodynamic control devices (with associated sensors and control systems) distributed along each blade to provide feedback load control (often referred to in popular terms as „smart structures‟ or „smart rotor control‟). A recent review of concepts and feasibility and an inventory of design options for such systems have been performed by Barlas and van Kuik at Delft University of Technology (TUDelft) 1 . Active load control utilizing trailing edge flaps or deformable trailing edge geometries (referred to here as Active Aerodynamic Load Control or AALC) is receiving significant attention, because of the direct lift control capability of such devices and recent advances in smart material actuator technology. Researchers at TUDelft 2-3 , Riso/Danish Technical University Laboratory for Sustainable Energy (Riso/DTU) 4-10 and Sandia National Laboratories (SNL) 11-17 have been very active in this area over the past few years. The SNL work has focused on performing extensive simulations of AALC on several turbine configurations and has analyzed the simulation results to estimate the fatigue damage reduction on the rotor and gearbox and the costof-energy benefits of integrating trailing edge technology into the tip region of the turbine blades. These simulation results show the potential for significant impacts on fatigue damage and cost of energy, but experimental data is badly needed to confirm the simulation-based analyses. To the best of our knowledge, no research group has yet built and field tested a rotor with a full smart blade set. SNL has built a set of blades for its 100 kW test turbine in order to test AALC concepts. The main thrusts of this effort are to develop and validate a highly accurate structural dynamics model of the operating rotor, to work through the implementation details involved with developing appropriate control algorithms for such a rotor, and to obtain experimental verification of simulation runs; we are not attempting to design the optimal rotor for integration of AALC control capability or to develop the optimal control strategy. The design of the blade set is covered briefly in this paper and the reader is directed to a previous AIAA paper 18 for additional information. The fabrication, integration, and test results to date for this smart blade set are the subjects of this paper.