An Integrated Model of the Kite and Tether Dynamics of a Marine Hydrokinetic Energy Harvesting System

Author(s):  
Miguel Alvarez ◽  
Debapriya Bhattacharjee ◽  
Chris Vermillion ◽  
Hosam K. Fathy
Author(s):  
Varun Lobo ◽  
Arindam Banerjee ◽  
Nyuykighan Mainsah ◽  
Jonathan Kimball

A Vortex Induced Vibration (VIV) based hydrokinetic energy system is discussed in this paper. Vibrations induced on a body (facing an external flow) due to the periodic irregularities in the flow caused by boundary layer separation are called as VIV. This separation of the boundary layer from the surface causes vortex formation in the wake region of the cylinder. The lift-force or the transverse oscillation of the vibrating cylinder depends upon the strength and modes of the vortex formed. The VIV energy harvesting system is based on the idea of maximizing rather than spoiling vortex shedding and was discovered in 2004 at the University of Michigan by Bernitsas and Raghavan. The vibrating bodies will in turn be used to harness energy using an efficient power-take-off system. In this paper, we discuss the hydrodynamic design of such a VIV based energy harvesting system using computational fluid dynamics. A fluid structure interaction calculation is performed to determine the forces on the surface of a bluff body due to separation of vortices from the surface. The hydrodynamic forces that act on such a system depend on the cylinder diameter, flow velocity, modes of vortex shedding and arrangement of cylinder(s). A detailed computational study on the effect of different design parameters listed above are first carried on a single cylinder arrangement; this is followed by a more detailed analysis that is extended to multiple cylinders. For a two-cylinder arrangement, the positions in which the cylinders are placed are also found to play an important role, as the vortex shed from one cylinder may be used to enhance the forces of lift on another cylinder present in its wake. Furthermore, the design of a VIV generator requires optimal damping and low mass ratio to enable high energy conversion via an efficient power take-off mechanism. The working and design considerations of the energy converter is outlined starting with a set of basic definitions pertaining to this technology. A tubular linear interior permanent magnet generator (TL-IPM) connected to a power converter is used; a linear generator was chosen to minimize mechanical components, such as gears or cams in the system.


Energy ◽  
2020 ◽  
Vol 202 ◽  
pp. 117749 ◽  
Author(s):  
V. Tamimi ◽  
M.J. Esfehani ◽  
M. Zeinoddini ◽  
S.T.O. Naeeni ◽  
J. Wu ◽  
...  

Author(s):  
Alexander M. Pankonien ◽  
Zoubeida Ounaies

This study focuses on a hydrokinetic energy harvesting system concept using piezoelectric materials. The Piezoelectric Active Kelp (PAK) system will consist of chemically inert piezoelectric polymers or piezoelectric ceramics manufactured into long flexible ribbons. The PAK system will convert the natural mechanical motions seen in kelp forests due to oceanic wave action, into electricity. As the periodic ocean currents, resulting from waves, pass over the PAK system, they cause the structure to oscillate back and forth. The piezoelectric materials will convert this mechanical motion directly into electrical power via the inverse piezoelectric effect. Large numbers of piezo-kelp ribbons would be mounted like forests on the ocean floor, producing a constant stream of smart grid power. PAK forest systems would also provide an artificial marine habitat while meeting the world’s demand for inexpensive and sustainable energy. Contrary to most forms of hydrokinetic energy harvesting system, the PAK system has no fast-moving parts or turbines and will be made of environmentally inert materials. The amount of power harvested by the PAK system depends upon the flow conditions, device configuration and size, and its piezoelectric material properties. Assuming specific flow conditions and fluid-structure interaction, this study will determine the optimal piezoelectric material to use, along with physical dimensions and layup configuration, to maximize the volumetric power density of the PAK system. The power generated by three common piezoelectric energy harvesting configurations: the unimorph, a homogeneous bimorph and a heterogeneous bimorph, will be compared for both a piezopolymer and a piezoceramic. Additionally, an appropriate figure-of-merit is also identified, based on the piezoelectric coefficient product (d31· g31) to compare the power production capabilities across materials.


Author(s):  
Lukas Sigrist ◽  
Andres Gomez ◽  
Matthias Leubin ◽  
Jan Beutel ◽  
Lothar Thiele

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