Theoretical Developments and Practical Aspects of Dynamic Systems in Wind Energy Applications

Abstract

The availability of offshore wind resources in coastal regions along with a high concentration of load centers in these areas makes offshore wind energy an attractive opportunity. Infrastructure costs and operation and maintenance costs for offshore wind technology, however, are significant obstacles that need to be overcome to make offshore wind a viable option. Vertical-axis wind turbines (VAWTs) are potentially ideal candidates for large offshore wind energy applications, and may provide a means to significantly reduce life-cycle costs associated with offshore wind energy. This has motivated the development of a flexible and extensible modular analysis framework for investigating VAWT designs. The Offshore Wind Energy Simulation toolkit contains a modular analysis framework that provides a general interface to external modules such as aerodynamics, hydrodynamics/platform dynamics, and generator/drive-train modeling software.

Theoretical developments in dynamic systems are also presented in this work. Implicit time integration methods are investigated for their applicability to Gyric systems (flexible systems undergoing general rotational motion). An energy conserving integration method for conventional flexible systems are considered and proven to be energy preserving for Gyric systems. A new, efficient procedure for developing linearized representation of discrete dynamic systems is also presented. Two existing approaches for developing linear representations are combined to arrive at a new, more efficient linearization procedure that overcomes the pitfalls of the individual approaches alone. Furthermore, aeroelastic stability is a known issue for large, flexible structures under aerodynamic loads, and aeroelastic analysis was considered in the development of wind energy design tools. Finally, an investigation of the structural dynamics of offshore VAWT structure is conducted. A fundamental understanding of a resonance in VAWT configurations is sought, and the effects of support conditions on dynamic response of VAWT configurations is explored.