Hudson Beare, Classroom 4
Friday, March 6, 2015 - 13:00 to 14:00
Speaker: Dr. Krish P. Thiagarajan
Correll Presidential Chair in Energy & Professor of Mechanical Engineering University of Maine, Orono, ME, USA
Title: Marine energy development in deep water using floating technology
Marine energy technology has taken the logical and conventional route: land or coast-based to bottom-founded offshore to floating types. In this process, some parts of the industry are customizing technology from the deepwater oil and gas industry, while other parts are focusing on migrating land-based technology. When considering floating energy converters, the designer should evaluate all the fundamental considerations, such as weight, stability and mooring, as well as inspection and maintenance.
The first part of the talk will summarize some recent work on floating technology for marine energy at UMaine, including wave, wind and tidal energy converters.
Wave energy: Our work supported a small business in Maine to develop a floating angled flap wave energy converter concept.
Tidal energy: University of Maine has been investigating second-generation tidal device technologies – both floating and bottom-fixed – that can make use of higher velocity fields in the water column.
Wind energy: Two important projects in this area are:
With funding from NSF, we are designing and constructing a multi-directional wind wave basin facility.
With the support of another Maine small business, we are studying adequacy of fatigue guidelines for mooring lines of floating offshore wind turbine structures.
The second part of the talk will discuss the nonlinear decay motion of a floating wind turbine platform. The motion is modeled using a one degree-of-freedom nonlinear oscillation equation about a mean offset angle. Attention is paid to the turbine thrust coefficient and its variability with respect to oncoming flow speed, which in turn is affected by the structure pitch motion. The equation of motion reveals that the mean offset position has an important role in the stiffness, damping, and consequently the natural period of pitch motion. The paper discusses a simple thrust model for an offshore wind turbine (OWT) based on rudiments of blade element theory. Model tests conducted on three generic floating wind turbine systems in 2011 found that for spar and semisubmersible type structures, resonant pitch motion was damped due to wind in storm sea conditions. Using the simplified thrust coefficient formulation, the increase in platform pitch damping due to wind is formulated and good agreement with the experiments are observed.
Krish Thiagarajan joined the University of Maine in 2011, as the Correll Presidential Chair in Energy. Concurrently he is a Professor of Mechanical Engineering. His research spans design and analysis of energy generating systems located offshore in the deep oceans. In particular, his area of research is dynamics and global performance of floating offshore systems for oil and gas, as well as renewable energy production.
Professor Thiagarajan received his PhD in Naval Architecture and Marine Engineering from the University of Michigan in 1993. Until recently, he served as Professor of Mechanical engineering at the University of Western Australia in Perth. From 2007 – 10, he also served as leader of the Offshore and Subsea Facilities research program within the Western Australian Energy Research Alliance based in Perth. He has over 100 journal and conference publications, and is an associate editor of Elsevier’s journal of Applied Ocean Research and ASME’s Journal of Offshore Mechanics and Arctic Engineering.
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