Jai N. Goundar

Design and Optimization of a Ducted Marine Current Savonius Turbine for Gun-barrel Passage, Fiji

Marine current energy is a reliable and clean source of energy. Many marine current turbines have been designed and developed over the years. Placement of an appropriately designed duct or shroud around the turbine significantly improves the turbine performance. In the present work, a Ducted Savonius Turbine (DST) is designed and optimized and its performance analysis carried out. The components of ducted Savonius turbines are simple and easily available and can be manufactured in developing countries like Fiji. A scaled-down model of 1/20 of a DST was fabricated and tested in a water stream at a velocity of 0.6 m/s and the results were used to validate the results from a commercial Computational Fluid Dynamics (CFD) code ANSYS-CFX. Finally, a full-scale DST was modeled to study the flow characteristics in the turbine and the performance characteristics. The maximum efficiency of the turbine is around 50% at the tip speed ratio (TSR) of 3.5 and the maximum shaft power obtained is 10 kW at the rated speed of 1.15 m/s and around 65 kW at a free-stream velocity of 2.15 m/s. The stress distribution on the ducted turbine was also obtained.

Design of a Ducted Cross Flow Turbine for Fiji

Marine current energy is clean and reliable energy source. It can be alternative energy source to produce electricity if tapped with a suitable marine current energy converter. Pacific Island countries (PIC) like Fiji can reduce the amount of Fossil fuel used. However for most energy converters designed perform well at marine current velocities above 2m/s and it needs to be installed at depths of 20 – 40m also installation and the maintenance cost of such devise will be quite high if it needs to be installed in Fiji. Therefore a ducted cross flow turbine was designed, which can give desired output at minimum installation and maintenance cost. A dusted cross flow turbine has been design taking into account for its operating condition. The turbine was modelled and analyzed in commercial; Computational Fluid dynamic (CFD) code ANSYS-CFX. The code was first validated and with experiment results and finally performance analysis of full scale turbine was carried out. The designed turbine can have maximum efficiency of 56% producing rated power of 21kW; it produces 0.77kW at cut in speed of 0.65m/s.

Design of a Gorlov Turbine for Marine Current Energy Extraction

As fossil fuels near depletion and their detrimental side effects become prominent on ecosystems, the world searches renewable sources of energy. Marine current energy is an emerging and promising renewable energy resource. Marine current energy can be alternative energy source for electricity production. Many marine current converters are designed to tap marine current energy; however, Gorlov turbine proves to have minimum manufacturing and maintenance cost, hence giving desired power output. A 0.3m diameter and 0.6m long 3 bladed Gorlov turbine was designed, fabricated and test to analyse its performance. The turbine produces average power 15 W and proves to be quite efficient for marine current energy extraction.

Design and Performance Testing of a Ducted Savonius Turbine for Marine Current Energy Extraction

Marine current energy is a reliable and clean source of energy. Several marine current turbines have been developed over the years, most of the turbines perform well at velocities over 2 m/s and need to be installed at depths of 20–40 m. Placing an appropriately designed duct or shroud around the turbine significantly improves the turbine’s performance. Ducted Savonius turbines can operate at low depths, since large clearance is not required because turbulent flow has little effect on the performance of the Savonius rotor. Ducted Savonius turbine has simple components and can be easily fabricated in Pacific Island Countries (PIC) and other places that do not have advanced manufacturing industries. A ducted Savonius turbine was designed for a location in Fiji, to operate at a rated marine current speed of 1.15 m/s and cut in speed of 0.2 m/s. The model of ducted Savonius turbine, scaled down to 1/20, was fabricated and tested in a water stream with a velocity of 0.6 m/s and was validated with commercial Computational Fluid Dynamics (CFD) code ANSYS-CFX. Finally, a full scale numerical model was constructed to study the flow characteristics and compute the performance. The area ratio of the duct of 2.5:1 (inlet to turbine section) shows significant increase in kinetic energy and an improved turbine performance. The maximum efficiency of the turbine is around 50% at a tip speed ratio (TSR) of 3.5 and the maximum power produced is 10 kW at the rated speed of 1.15 m/s and 63.4 kW at a free-stream velocity of 2.15 m/s.© 2013 ASME

Optimization of Hydrofoils for Horizontal Axis Marine Current Turbines Using Genetic Algorithm

As fossil fuels near depletion and their detrimental side effects become prominent on ecosystems, the world is searching for renewable sources of energy. Tidal energy is an emerging and promising renewable energy resource. Tidal turbines can extract energy from the flowing water in a similar way as wind turbines extract energy from the wind. The upside with tidal turbines is that the density of water is approximately 800 times greater than that of air and a tidal turbine harnessing the same amount of power as a wind turbine can be considerably smaller in size. At the heart of the horizontal axis marine current turbines are carefully designed hydrofoil sections. While there is a growing need to have hydrofoils that provide good hydrodynamic and structural performances, the hydrofoils also have to avoid cavitation for safe operation. This study uses a genetic algorithm optimization code to develop hydrofoils which have the desired qualities mentioned above. The hydrofoil problem is parameterized using a composite Bezier curve with two Bezier segments and 11 control points. Appropriate curvature conditions are implemented and geometric constraints are enforced to maintain the hydrofoil thickness between 16 to 18%. XFOIL is used as the flow solver in this study. The hydrofoils are optimized at Reynolds number of 2 million and for angles between 4 to 10 degrees. The best foil from the results, named USPT4 is tested for performance with the CFD code ANSYS CFX. The CFX results are validated with experimental results in a wind tunnel at the same Reynolds number. The hydrofoil’s performance is also compared with a commonly used NACA foil.Copyright

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.Copyright