Spar

Abstract: This work presents a comprehensive dynamic–response analysis of three offshore floating wind turbine concepts. Models were composed of one 5 MW turbine supported on land and three 5 MW turbines located offshore on a tension leg platform, a spar buoy and a barge. A loads and stability analysis adhering to the procedures of international design standards was performed for each model using the fully coupled time domain aero-hydro-servo-elastic simulation tool FAST with AeroDyn and HydroDyn. The concepts are compared based on the calculated ultimate loads, fatigue loads and instabilities. The loads in the barge-supported turbine are the highest found for the three floating concepts. The differences in the loads between the tension leg platform–supported turbine and spar buoy–supported turbine are not significant, except for the loads in the tower, which are greater in the spar system. Instabilities in all systems also must be resolved. The results of this analysis will help resolve the fundamental design trade-offs between the floating-system concepts. Copyright © 2011 John Wiley & Sons, Ltd.

Abstract: SUMMARY This paper investigates the use of single and multiple tuned mass dampers (TMDs) for passive control of edgewise vibrations of nacelle/tower and spar of spar-type floating wind turbines (S-FOWTs). Uncontrolled and controlled mathematical models of the S-FOWT are developed by using Euler-Lagrangian energy formulations. In these models, the aerodynamic properties of the blade, variable mass and stiffness, gravity, the interactions among the blades, nacelle, spar and mooring system, the hydrodynamic effects, the restoring moment, and the buoyancy force are considered. The vibrations of the blades, nacelle, tower, and spar are coupled in all degrees of freedom and in all inertial, dissipative, and elastic components. In the controlled model, several set of horizontal TMDs are placed in the spar at various depths and the coupling of these TMDs with the nacelle and spar motions is considered. The control effectiveness is evaluated by the reduction of the root-mean-square and maximum response. The control feasibility is examined by using the spar sinking and the TMD maximum strokes. The investigations using nonlinear time–domain simulation show that a single TMD can reduce up to 40% of the nacelle sway displacement and the spar roll, and that the reduction observed with multiple TMDs is 50%. The influence of the spar TMD is more significant than that of the nacelle TMD. The spar TMDs are less effective when their positions are lower. In all the cases studied, good heave performance of the S-FOWT is maintained. Copyright © 2014 John Wiley & Sons, Ltd.

Abstract: The species–area relationship (SPAR) was the central paradigm for the emerging science of reserve design in the 1970s and early 1980s. The apparent consistency of the SPAR for natural areas suggested that it could be used to predict the number of species that would be maintained within the isolated confines of a nature reserve. This proposed use of the SPAR led to heated debates about how best to partition space among reserves. However, by the end of the 1980s, the SPAR was no longer a central issue in reserve design. There was too much uncertainty about the underlying causes of the SPAR to trust that it would hold for reserves. The SPAR was also inappropriate for the design of single-species reserves and thus did not answer the traditional needs of wildlife managers. Ecologists subsequently focused their reserve-design efforts on the management of individual populations to reduce the probability of extinction and the loss of genetic variation. Nevertheless, because the SPAR does not require detailed knowledge of the requirements of individual species, it is still used to estimate local species richness and to predict the effects of habitat loss and fragmentation on biodiversity. These applications of the SPAR may be especially useful in the design of marine reserves, which often differ in purpose from conventional terrestrial reserves and may require fundamentally different approaches.