The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
K Kusakana - One of the best experts on this subject based on the ideXlab platform.
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micro hydrokinetic river system modelling and analysis as compared to wind system for remote rural electrification
Electric Power Systems Research, 2015Co-Authors: S P Koko, K Kusakana, H J VermaakAbstract:Abstract Micro-hydrokinetic river (MHR) system is one of the promising technologies to be used for remote rural electrification. In rural areas with access to both wind and flowing water resources, wind generation is selected as a first electrification priority. The potential benefit of generating electricity using flowing water resource is unnoticed. Hence, this paper presents the modelling and performance analysis of a MHR system as compared to wind generation system using MATLAB/Simulink software. These performances are compared to generate the same amount of electrical power. A permanent magnet synchronous generator (PMSG) has been chosen or used to investigate the behaviour of each system under variable speeds. The developed model includes horizontal turbine model, drive train model and PMSG model. The simulation results illustrate the ability of a hydrokinetic turbine driven PMSG to generate electricity markedly better and cheaper than a wind driven PMSG within South Africa. Hence, the MHR system presents a cheap electrification opportunity for poor rural households.
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feasibility analysis of river off grid hydrokinetic systems with pumped hydro storage in rural applications
Energy Conversion and Management, 2015Co-Authors: K KusakanaAbstract:Abstract Hydrokinetic power generation is currently gaining interest as a cost effective way of supplying isolated areas where reasonable water resource is available. However the seasonal characteristic of the water resource as well as the intermittent fluctuating load demand prevents this power generation system from being entirely reliable without appropriate energy storage system. Few researchers have recently analyzed the use of hydrokinetic systems as standalone or combined with other energy source, however the authors of these researches did not explore other means of storing energy except for traditional battery storage systems. In this study, the most conventional and established storage technology, pumped hydro storage, is proposed to be used in conjunction with a standalone hydrokinetic system in off-grid power supply. The techno-economic feasibility of such combination is analyzed and compared to the option where batteries are considered as storage system. The operation principle of the system is presented; the mathematical model and simulation model are also developed. Simulations are performed using two different types of loads in rural South Africa as case studies to demonstrate the technical cost advantages as well as the cost effectiveness of the proposed supply option. The results reveal that the novel micro-pumped hydro storage based hydrokinetic system is a cost-effective, reliable and environmentally friendly solution to achieve 100% energy autonomy in remote and isolated communities.
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techno economic analysis of off grid hydrokinetic based hybrid energy systems for onshore remote area in south africa
Energy, 2014Co-Authors: K KusakanaAbstract:Hydrokinetic power generation is a relatively recent type of hydropower that generates electricity from kinetic energy of flowing water making the conversion process more competitive compared to traditional micro-hydropower. Few authors have already analyzed the use of standalone hydrokinetic systems for rural electrification, however, there is no available literatures investigating the possibility of using this technology in combination with other renewable energy sources or diesel generator. Therefore, the aim of this paper is to investigate the potential use of hydrokinetic-based hybrid systems for low cost and sustainable electrical energy supply to isolated load in rural South Africa where adequate water resource is available. Different hybrid system configurations are modeled and simulated using the Hybrid Optimization Model for Electric Renewable (HOMER) and the results are analyzed to select the best supply option based on the net present cost and the cost of energy produced. The simulation results from two different case studies show that hybrid systems with hydrokinetic modules incorporated in their architectures have lower net present costs as well as lower costs of energy compared to all other supply options where the hydrokinetic modules are not included.
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hydrokinetic power generation for rural electricity supply case of south africa
Renewable Energy, 2013Co-Authors: K Kusakana, H J VermaakAbstract:Abstract This study investigates the possibility of using and developing hydrokinetic power to supply reliable, affordable and sustainable electricity to rural, remote and isolated loads in rural South Africa where reasonable water resource is available. Simulations are performed using the Hybrid Optimization Model for Electric Renewable (HOMER) and the results are compared to those from other supply options such as standalone Photovoltaic system (PV), wind, diesel generator (DG) and grid extension. Finally the paper points out some major challenges that are facing the development of this technology in South Africa.
R P Saini - One of the best experts on this subject based on the ideXlab platform.
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performance analysis of a single stage modified savonius hydrokinetic turbine having twisted blades
Renewable Energy, 2017Co-Authors: Anuj Kumar, R P SainiAbstract:Abstract Savonius hydrokinetic turbine is one of the prominent vertical axis turbines for tapping hydro potential available in flowing streams in rivers or canals. In spite of their simple design, Savonius turbines have the problem of poor performance. This study aims to enhance the performance of turbine through modification in the blade shape. Under the present study, geometrical parameters namely blade arc angle and blade shape factor are considered to modify the blade shape of Savonius hydrokinetic turbine. A commercial unsteady Reynolds-Averaged Navier-Stokes (URANS) solver in conjunction with realizable k-e turbulence model has been used for numerical analysis. Using CFD analysis, blade arc angle and blade shape factor are optimized on the basis of coefficient of power. Fluid flow distributions found around the rotor has also been analyzed and discussed. Based on the present investigation, the maximum power coefficient value of 0.426 is obtained for blade arc angle of 150° and blade shape factor of 0.6 corresponding to TSR value of 0.9 at flow velocity of 2 m/s.
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performance analysis of a savonius hydrokinetic turbine having twisted blades
Renewable Energy, 2017Co-Authors: Anuj Kumar, R P SainiAbstract:Abstract In the quest for renewable energy sources, kinetic energy available in small water streams, river streams or human-made canals may provide new avenue which can be harnessed by using hydrokinetic turbines. Savonius hydrokinetic turbine is vertical axis turbine having drag based rotor and suitable for a lower flow velocity of the water stream. In order to enhance the efficiency of the turbine, this paper aims to analyze the performance of twisted blade Savonius hydrokinetic turbine. Using CFD analysis, an attempt has been made to optimize blade twist angle of Savonius hydrokinetic turbine. The simulation of a twisted Savonius hydrokinetic turbine having two blades has been carried out to investigate the performance. Commercial unsteady Reynolds-Averaged Navier-Stokes (URANS) solver in conjunction with realizable k-e turbulence model has been used for numerical analysis. Fluid flow distributions around the rotor have been analyzed and discussed. It has been found that Savonius hydrokinetic turbine having a twist angle of 12.5° yields a maximum coefficient of power as 0.39 corresponding to a TSR value of 0.9 for a given water velocity of 2 m/s.
H J Vermaak - One of the best experts on this subject based on the ideXlab platform.
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micro hydrokinetic river system modelling and analysis as compared to wind system for remote rural electrification
Electric Power Systems Research, 2015Co-Authors: S P Koko, K Kusakana, H J VermaakAbstract:Abstract Micro-hydrokinetic river (MHR) system is one of the promising technologies to be used for remote rural electrification. In rural areas with access to both wind and flowing water resources, wind generation is selected as a first electrification priority. The potential benefit of generating electricity using flowing water resource is unnoticed. Hence, this paper presents the modelling and performance analysis of a MHR system as compared to wind generation system using MATLAB/Simulink software. These performances are compared to generate the same amount of electrical power. A permanent magnet synchronous generator (PMSG) has been chosen or used to investigate the behaviour of each system under variable speeds. The developed model includes horizontal turbine model, drive train model and PMSG model. The simulation results illustrate the ability of a hydrokinetic turbine driven PMSG to generate electricity markedly better and cheaper than a wind driven PMSG within South Africa. Hence, the MHR system presents a cheap electrification opportunity for poor rural households.
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hydrokinetic power generation for rural electricity supply case of south africa
Renewable Energy, 2013Co-Authors: K Kusakana, H J VermaakAbstract:Abstract This study investigates the possibility of using and developing hydrokinetic power to supply reliable, affordable and sustainable electricity to rural, remote and isolated loads in rural South Africa where reasonable water resource is available. Simulations are performed using the Hybrid Optimization Model for Electric Renewable (HOMER) and the results are compared to those from other supply options such as standalone Photovoltaic system (PV), wind, diesel generator (DG) and grid extension. Finally the paper points out some major challenges that are facing the development of this technology in South Africa.
Anuj Kumar - One of the best experts on this subject based on the ideXlab platform.
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performance analysis of a single stage modified savonius hydrokinetic turbine having twisted blades
Renewable Energy, 2017Co-Authors: Anuj Kumar, R P SainiAbstract:Abstract Savonius hydrokinetic turbine is one of the prominent vertical axis turbines for tapping hydro potential available in flowing streams in rivers or canals. In spite of their simple design, Savonius turbines have the problem of poor performance. This study aims to enhance the performance of turbine through modification in the blade shape. Under the present study, geometrical parameters namely blade arc angle and blade shape factor are considered to modify the blade shape of Savonius hydrokinetic turbine. A commercial unsteady Reynolds-Averaged Navier-Stokes (URANS) solver in conjunction with realizable k-e turbulence model has been used for numerical analysis. Using CFD analysis, blade arc angle and blade shape factor are optimized on the basis of coefficient of power. Fluid flow distributions found around the rotor has also been analyzed and discussed. Based on the present investigation, the maximum power coefficient value of 0.426 is obtained for blade arc angle of 150° and blade shape factor of 0.6 corresponding to TSR value of 0.9 at flow velocity of 2 m/s.
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performance analysis of a savonius hydrokinetic turbine having twisted blades
Renewable Energy, 2017Co-Authors: Anuj Kumar, R P SainiAbstract:Abstract In the quest for renewable energy sources, kinetic energy available in small water streams, river streams or human-made canals may provide new avenue which can be harnessed by using hydrokinetic turbines. Savonius hydrokinetic turbine is vertical axis turbine having drag based rotor and suitable for a lower flow velocity of the water stream. In order to enhance the efficiency of the turbine, this paper aims to analyze the performance of twisted blade Savonius hydrokinetic turbine. Using CFD analysis, an attempt has been made to optimize blade twist angle of Savonius hydrokinetic turbine. The simulation of a twisted Savonius hydrokinetic turbine having two blades has been carried out to investigate the performance. Commercial unsteady Reynolds-Averaged Navier-Stokes (URANS) solver in conjunction with realizable k-e turbulence model has been used for numerical analysis. Fluid flow distributions around the rotor have been analyzed and discussed. It has been found that Savonius hydrokinetic turbine having a twist angle of 12.5° yields a maximum coefficient of power as 0.39 corresponding to a TSR value of 0.9 for a given water velocity of 2 m/s.
Michael M Bernitsas - One of the best experts on this subject based on the ideXlab platform.
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performance prediction of horizontal hydrokinetic energy converter using multiple cylinder synergy in flow induced motion
Applied Energy, 2016Co-Authors: Eun Soo Kim, Michael M BernitsasAbstract:Abstract Horizontal hydrokinetic energy can be harnessed using Steady Lift Technology (SLT) like turbines or Alternating Lift Technology (ALT) like the VIVACE Converter. Tidal/current turbines with low mechanical losses typically achieve about 30% peak power efficiency, which is equivalent to 50.6% power efficiency over the Betz limit at flow speed nearly 3.0 m/s. The majority of flows worldwide are slower than 1.0–1.5 m/s. Turbines also require large in-flow spacing resulting in farms of low power-to-volume density. Alternating-lift overcomes these challenges. The purpose of this study is to show that the ALT Converter is a three-dimensional energy absorber that efficiently works in river/ocean currents as slow as 1.0–1.5 m/s a range of velocities presently inaccessible to watermills and turbines. This novel converter utilizes flow-induced motions (FIM), which are potentially destructive phenomena for structures, enhances them, and converts hydrokinetic energy to electricity. It was invented in the Marine Renewable Energy Lab (MRELab) and patented through the University of Michigan. MRELab has been studying the effect of passive turbulence control (PTC) to enhance FIMs and to expand their synchronization range for energy harnessing. This study shows that multiple cylinders in proximity can synergistically work and harness more energy than the same number of a single cylinder in isolation. Estimation based on experiments, shows that a 4 PTC-cylinder Converter can achieve 88.6% peak efficiency of the Betz limit at flow speed slower than 1.0 m/s and power-to-volume density of 875 W/m 3 at 1.45 m/s. Thus, the Converter can efficiently harness energy from rivers and ocean current as slow as 0.8–1.5 m/s, with no upper limit in flow velocity.
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computational and experimental assessment of turbulence stimulation on flow induced motion of circular cylinder
ASME 2015 34th International Conference on Ocean Offshore and Arctic Engineering OMAE 2015, 2015Co-Authors: Omer Kemal Kinaci, Sami Lakka, Hai Sun, Michael M BernitsasAbstract:In the Marine Renewable Energy Laboratory (MRELab) of the University of Michigan, Flow Induced Motion (FIM) is studied as a means to convert marine hydrokinetic energy to electricity using the VIVACE energy harvester [1–4]. Turbulence stimulation in the form of sand-strips, referred to as Passive Turbulence Control (PTC), were added to oscillating cylinders in 2008 [5]. PTC enabled VIVACE to harness hydrokinetic energy from currents/tides over the entire range of FIM including VIV and galloping. In 2011, the MRELab produced experimentally the PTC-to-FIM Map defining the induced cylinder motion based on the location of PTC [6]. In 2013, the robustness of the map was tested and dominant zones were identified [7]. Even though the PTC-to-FIM Map has become a powerful tool in inducing specific motions of circular cylinders, several parameters remain unexplored. Experiments, though the ultimate verification tool, are time consuming and hard to provide all needed information. A computational tool that could predict the FIM of a cylinder correctly would be invaluable to study the full parametric design space. A major side-benefit of PTC was the fact that PTC enabled computational fluid dynamic (CFD) simulations to generate results in good agreement with experiments by forcing the location of the separation point [8]. This valuable tool, along with experiments, is used in this paper to investigate PTC design parameters such as width and thickness and their impact on flow features with the intent of maximizing FIM and, thus, hydrokinetic energy conversion.Copyright © 2015 by ASME
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viv and galloping of single circular cylinder with surface roughness at 3 0 104 re 1 2 105
Ocean Engineering, 2011Co-Authors: Che Chun Chang, Ajith R Kumar, Michael M BernitsasAbstract:Abstract Passive Turbulence Control (PTC) in the form of selectively distributed surface roughness is used to alter Flow Induced Motion (FIM) of a circular cylinder in a steady flow. The objective is to enhance FIM's synchronization range and amplitude, thus maximizing conversion of hydrokinetic energy into mechanical energy by oscillator in vortex-induced vibration and/or galloping. Through additional viscous damping, mechanical energy is converted to electrical harnessing clean and renewable energy from ocean/river currents. High Reynolds numbers ( Re ) are required to reach the high-lift TrSL3 (Transition-Shear-Layer-3) flow regime. PTC trips flow separation and energizes the boundary layer, thus inducing higher vorticity and consequently lift. Roughness location, surface coverage, and size are studied using systematic model tests with broad-field laser visualization at 3.0×10 4 Re 5 in the low-turbulence free-surface water-channel of the Marine Renewable Energy Laboratory of the University of Michigan. Test results show that 16° roughness coverage is effective in the range (10°–80°) inducing reduced vortex-induced vibration (VIV), enhanced VIV, or galloping. Range of synchronization may increase or decrease, galloping amplitude of oscillation reaches three diameters; wake structures change dramatically reaching up to ten vortices per cycle. Conversion of hydrokinetic energy to mechanical is enhanced strongly with proper PTC.
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virtual damper spring system for viv experiments and hydrokinetic energy conversion
Ocean Engineering, 2011Co-Authors: N Xiros, Michael M BernitsasAbstract:Abstract A device/system V CK is built to replace the physical damper/springs of the VIVACE Converter with virtual elements. VIVACE harnesses hydrokinetic energy of currents by converting mechanical energy of cylinders in Vortex Induced Vibrations (VIV) into electricity. V CK enables conducting high number of model tests rapidly as damping/springs are set by software rather than hardware. V CK consists of a cylinder, a belt–pulley transmission, a motor/generator, and a controller. The controller provides a damper–spring force feedback using displacement/velocity measurements, thus introducing no artificial force–displacement phase lag, which biases energy conversion. Damping is nonlinear, particularly away from the system natural frequency, and affects modeling near the VIV synchronization ends. System identification (SI) in air reveals nonlinear viscous damping, static and dynamic friction. Hysteresis, occurring in the zero velocity limit, is modeled by a nonlinear dynamic damping model Linear Autoregression with Nonlinear Static model (LARNOS). SI performed in air is verified using monochromatic excitation in air and VIV tests in water using physical damper and springs. A resistor bank added to the device provides an integrated V CK /Power Take-Off (PTO) system. VIV testing is performed in the Low Turbulence Free Surface Water Channel of the University of Michigan at 40,000 Re
