Overview of wave and tidal current energy research in the South Pacific

The South Pacific region spreads over tens of millions of square kilometers of ocean with immense potential for ocean energy such as wave energy, tidal current energy and ocean thermal energy. The land-mass for the countries in this region is very small compared to the total area; for example, for a country Kiribati, this area is more than 4000. Moreover, the geographical layout of the region with scattered islands and unavailability of power grid requires tailor-made solutions. In this scenario, waves and tidal currents have a very strong potential for becoming a sustainable source of power. At some of the locations with good waves, long term measurements are performed with a plan to extract energy. Some of the remote islands have severe shortage of water and it is planned to obtain desalinated water using wave-powered desalination systems. There are hundreds of small islands and a large number of reef openings, passages and sea-connected rivers where there are strong bi-directional currents. ADCP measurements are completed at some of the locations and some more are in progress/in the pipeline. The ongoing work includes development of new wave energy conversion devices such as an innovative concept of a rectangular OWC designed to direct the bi-directional flow onto the blades of a Savonius rotor, and the rotors driven by the orbital motion in waves. The other work involves design of blade sections and blades for tidal current turbines as well as computational study of cross-flow turbines for tidal current power generation

Quantum Hall Droplets on Disc and Effective Wess-Zumino-Witten Action for Edge States

We algebraically analysis the quantum Hall effect of a system of particles living on the disc ${\bf B}^1$ in the presence of an uniform magnetic field $B$. For this, we identify the non-compact disc with the coset space $SU(1,1)/U(1)$. This allows us to use the geometric quantization in order to get the wavefunctions as the Wigner ${\cal D}$-functions satisfying a suitable constraint. We show that the corresponding Hamiltonian coincides with the Maass Laplacian. Restricting to the lowest Landau level, we introduce the noncommutative geometry through the star product. Also we discuss the state density behavior as well as the excitation potential of the quantum Hall droplet. We show that the edge excitations are described by an effective Wess-Zumino-Witten action for a strong magnetic field and discuss their nature. We finally show that LLL wavefunctions are intelligent states.Comment: 18 pages, clarifications and misprints corrected, version published in IJGMM

Design and Optimization of a Horizontal Axis Marine Current Turbine

As fossil fuels near depletion and their detrimental side effects become prominent on ecosystems, the world searches for renewable sources of energy. Marine current energy is an emerging and promising renewable energy resource. At the heart of the horizontal axis marine current turbines (HAMCT) are carefully designed hydrofoil sections and optimized blade twist and chord distribution. While there is growing needs to have hydrofoils that provide good hydrodynamic and structural performance, the hydrofoils also have to avoid cavitation due to high suction pressures. This study focuses on designing efficient hydrofoils - HM05XX series; this series has very good hydrodynamic properties and also these sections are thick enough to provide structural strength to the blades. The HM05XX series hydrofoils were used to design and optimize HAMCT. The designed HAMCT has rated operating speed of 1.5 m/s, cut in speed of 0.5 m/s and cut-off speed of 3 m/s. The turbine was optimized using HARP-Opt (Horizontal axis rotor optimization) code that utilizes a multiple objective genetic algorithm and blade-element momentum (BEM) theory flow model to design horizontal-axis wind and hydrokinetic turbine rotors

Experimental Study of Wave Forces on an Offshore Wind Turbine Tower Model

study of a tapered wind turbine tower is performed using particle image velocimetry and numerical methods. A 1.5 MW wind turbine base was studied and re-designed. A scaled model of a simple tapered tower base was studied in a wave channel using Particle Image Velocimetry (PIV) to understand the flow phenomena at the tower base. Theoretical and experimental results were found using Morrison equations. The diffraction parameter shows that the linear wave theory is not valid for inertial co-efficient calculations. A direct value of 2.0 resulted for the inertial coefficient values while a lower drag influence was noted at coefficient of drag = 0.315. The turbine’s horizontal force profile is improved in this study to yield a 69% reduction in overturning moment by redesigning the turbines submerged tower

The Study of Optical and Electrical Properties of Nanostructured Silicon Carbide Thin Films Grown by Pulsed-Laser Deposition

In this paper, nanostructured silicon carbide (SiC) thin films are deposited onto glass substrate using pulsed laser deposition technique. Electrical and optical characterizations such as conductivity, resistivity, transmission, Seeback effect, absorption, absorption coefficient, energy band gap, and extinction coefficient as a function of photon energy, and the effect of thin films thickness on transmission are carried out to characterize the prepared samples. Results showed that the prepared SiC thin film is an n-type semiconductor with an indirect bandgap of ~3 eV, 448 nm cutoff wavelength, 3.4395 × 104 cm−1 absorption coefficient and 0.154 extinction coefficient. The surface morphology of the SiC thin films is studied using scanning electron microscope at a substrate temperature of 400 °C and it is found that the grain size of the prepared SiC thin film is about 30 nm. As such, the nano thin films optical and structural characteristics enable the films to be used as gases sensors in many optoelectronic devices such as the environment and ultraviolet photodiode

Design of a horizontal axis wind turbine for Fiji

The demand and cost of electricity has increased for Pacific Island Countries (PICs). The electricity from main grid does not reach rural areas and outer islands of Fiji. They burn fuel for electricity and daily lighting. Therefore, there is a need to look for alternative energy sources. Wind turbine technology has developed over the past years and is suitable for generating electricity by tapping wind energy. However, turbines designed to operate at higher wind speed do not perform well in Fiji, because Fiji’s average wind velocity is around 5-6 m/s. A 10 m, 3-bladed horizontal axis wind turbine is designed to operate at low wind speed, cut in speed of 3 m/s, cut off speed of 10 m/s and rated wind speed of 6 m/s. The blade sections were designed for different locations along the blade. The airfoil at the tip (AF0914) a has maximum thickness of 14% and maximum camber of 9%; the thickness varies linearly to the root, at the root the airfoil (AF0920) has a maximum thickness of 20% and maximum camber of 9%. The aerodynamic characteristics of airfoil AF0914 were obtained using Xfoil and were validated by experimentation, at turbulence intensities (Tu) of 1% and 3%, and a Reynolds number (Re) of 200,000. The aerodynamic characteristics of other airfoils were also obtained at operating Re at the turbulence intensities of 1% and 3%. These airfoils have good characteristics at low wind speed, and were used to design the 10 m diameter 3-bladed HAWT for Fiji. The turbine has a linear chord distribution for easy manufacturing purpose. Twist distribution was optimized using Blade Element Momentum (BEM) theory, and theoretical power and turbine performance were obtained using BEM theory. At the rated wind speed of 6 m/s and a TSR of 6.5, the theoretical efficiency of the rotor is around 46% and maximum power is 4.4 kW. The turbine has good performance at lower wind speeds and is suitable for Fiji’s conditions

Computational studies on the effect of geometric parameters on the performance of a solar chimney power plant

A solar chimney power plant (SCPP) is a renewable-energy power plant that transforms solar energy into electricity. The SCPP consists of three essential elements – solar air collector, chimney tower, and wind turbine(s). The present work is aimed at optimizing the geometry of the major components of the SCPP using a computational fluid dynamics (CFD) software ANSYS-CFX to study and improve the flow characteristics inside the SCPP. The overall chimney height and the collector diameter of the SCPP were kept constant at 10 m and 8 m respectively. The collector inlet opening was varied from 0.05 m to 0.2 m. The collector outlet diameter was also varied from 0.6 m to 1 m. These modified collectors were tested with chimneys of different divergence angles (0�–3�) and also different chimney inlet openings of 0.6 m to 1 m. The diameter of the chimney was also varied from 0.25 m to 0.3 m. Based on the CFX computational results, the best configuration was achieved using the chimney with a divergence angle of 2� and chimney diameter of 0.25 m together with the collector opening of 0.05 m and collector outlet diameter of 1 m. The temperature inside the collector is higher for the lower opening resulting in a higher flow rate and power

Application of UPFC to Improve the LVRT Capability of Wind Turbine Generator

Variable speed wind turbine generators installation has been significantly increased worldwide in the last few years. Voltage sag at the grid side may call for the disconnection of the wind turbine from the grid as under such faults it may not comply with the recent developed grid codes for wind energy conversion systems (WECS). In this paper, a Unified Power Flow Controller (UPFC) is applied to improve the low voltage ride through (LVRT) capability of doubly fed induction generator (DFIG)-based WECS during voltage sag at the grid side. Simulation is carried out using MATLAB/Simulink software. Results show that UPFC can significantly improve the LVRT capability of DFIG-based WECS and hence maintaining wind turbine connection to the grid during certain levels of voltage sag at the grid side

Lane detection system for day vision using altera DE2

The active safety systems used in automotive field are largely exploiting lane detection technique for warning the vehicle drivers to correct any unintended road departure and to reach fully autonomous vehicles. Due to its ability, to be programmed, to perform complex mathematical functions and its characterization of high speed processing, Field Programmable Gate Array (FPGA) could cope with the requirement of lane detection implementation and application. In the present work, lane detection is implemented using FPGA for day vision. This necessitates utilization of image processing techniques like filtering, edge detection and thresholding. The lane detection is performed by firstly capturing the image from a video camera and converted to gray scale. Then, a noise filtering process for gray image is performed using Gaussian and average filter. Methods from first and second order edge detection techniques have been selected for the purpose of lane edge detection. The effect of manually changing the threshold level on image enhancement has been examined. The results showed that raising threshold level would better enhance the image. The type of FPGA device used in the present work is Altera DE2. Firstly, the version DE2 Cyclone II start with (11xxxxxx-xxxx) together with Genx camera has been used. This camera supports both formats NTSC and PAL, while the above version of FPGA backups only NTSC format. The software of lane detection is designed and coded using Verilog language