Tag Archives: Current

Technological Cost-Reduction Pathways for Axial-Flow Turbines in the Marine Hydrokinetic Environment


Daniel L. Laird, Erick L. Johnson, Margaret E. Ochs, and Blake Boren – Sandia National Laboratories Technical Report, September 2013

Abstract

This report considers and prioritizes potential technical cost‐reduction pathways for axial‐flow turbines designed for tidal, river, and ocean current resources. This report focuses on technical research and development cost‐reduction pathways related to the device technology rather than environmental monitoring or permitting opportunities. Three sources of information were utilized to understand current cost drivers and develop a list of potential cost‐reduction pathways: a literature review of technical work related to axial‐flow turbines, the U.S. Department of Energy Reference Model effort, and informal webinars and other targeted interactions with industry developers. Data from these various information sources were aggregated and prioritized with respect to potential impact on the lifetime levelized cost of energy. The four most promising cost‐reduction pathways include structural design optimization; improved deployment, maintenance, and recovery; system simplicity and reliability; and array optimization.

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A new method for failure modes and effects analysis and its application in a hydrokinetic turbine system


Liang Xie – Missouri University of Science and Technology, Masters Thesis, 2013

Abstract

The traditional failure modes and effects analysis (FMEA) is a conceptual design methodology for dealing with potential failures. FMEA uses the risk priority number (RPN), which is the product of three ranked factors to prioritize risks of different failure modes. The three factors are occurrence, severity, and detection. However, the RPN may not be able to provide consistent evaluation of risks for the following reasons: the RPN has a high degree of subjectivity, it is difficult to compare different RPNs, and possible failures may be overlooked in the traditional FMEA method. Continue reading

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Synergy of multiple cylinders in flow induced motion for hydrokinetic energy harvesting


Eun Soo Kim – University of Michigan, Doctoral Dissertation, 2013

Abstract

Vortex Induced Vibrations for Aquatic Clean Energy (VIVACE) Converter is a converter of marine hydro-kinetic energy invented in the Marine Renewable Energy Lab (MRELab) and patented by the University of Michigan. It harnesses hydrokinetic energy from ocean/tidal/river currents. In its simplest form the VIVACE Converter is a single circular cylinder on springs with a power take-off system. Using passive turbulence control, VIVACE maximizes and utilizes flow induced motion in the form of vortex induced vibration or interference/proximity/wake/soft/hard galloping. MRELab has achieved back-to-back vortex induced vibration and galloping for a single cylinder with passive turbulence control thus more than doubling the range of synchronization of flow induced motion (FIM). Continue reading

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Hydrodynamic optimization and design of marine current turbines and propellers


Menéndez Arán, David Hernán – Masters thesis, University of Texas, 2013

Abstract

This thesis addresses the optimization and design of turbine and propeller blades through the use of a lifting line model. An existing turbine optimization methodology has been modified to include viscous terms, non-linear terms, and a hub model. The method is also adapted to the optimization of propellers. Two types of trailing wake geometries are considered: one based on helical wakes which are aligned at the blade (using the so-called “moderately loaded propeller” assumption), and a second one based on a full wake alignment model in order to represent more accurately the wake geometry and its effect on the efficiency of the rotor. Continue reading

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Transmision Shaft Design for Hydrokinetic Turbine with Reliability Consideration


Gouthan Pusapati – Missouri University of Science and Technology, 2013

Abstract

Hydrokinetic energy, a relatively new kind of renewable energy, can be generated from flowing water in rivers or oceans. Hydrokinetic turbines (HKTs) are a major system for hydrokinetic energy, and the reliability of the HKTs is critical for both their lifecycle cost and safety. The objective of this work is to apply advanced methodologies of reliability analysis and reliability-based design to the transmission shaft design for a horizontal-axis, non-submerged HKT. The deterministic shaft design is performed first by considering failure modes of strength and deflection using distortion energy, maximum shear and deflection theories. Then the reliability analysis of the shaft designed is performed by using Sampling Approach to Extreme Values of Stochastic Process method (SAEVSP). Finally reliability-based design is applied to the transmission shaft design, which results in the minimal shaft diameter that satisfies the reliability requirement for a given period of operation time. Since the time-dependent river velocity process is involved, the time-dependent reliability method is used in the reliability-based design. The methodology for the shaft design in this work can be extended to the design of other components in the HKT system.

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Marine current energy resource assessment and design of a marine current turbine for Fiji


Jai N. Goundar and M. Rafiuddin Ahmed – Renewable Energy, July 2013

Abstract

Pacific Island Countries (PICs) have a huge potential for renewable energy to cater for their energy needs. Marine current energy is a reliable and clean energy source. Many marine current streams are available in Fiji’s waters and large amount of marine current energy can be extracted using turbines. Horizontal axis marine current turbine (HAMCT) can be used to extract marine current energy to electrical energy for commercial use. For designing a HAMCT, marine current resource assessment needs to done. A potential site was identified and resource assessment was done for 3 months. Continue reading

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Filed under Component Development, Resource Characterization

Numerical Simulation of Fully Passive Flapping Foil Power Generation


John Young, Muhammad A. Ashraf, Joseph C. S. Lai, and Max F. Platzer – AIAA Journal, 2013

A fully passive flapping foil turbine was simulated using a two-dimensional Navier–Stokes solver with two-way fluid-structure interaction at a Reynolds number based on freestream flow Re=1100 and 1.1×106 with a NACA 0012 foil. Both pitch angle and angle-of-attack control methodologies were investigated. Efficiencies of up to 30% based on the Betz criterion were found using pitch control, which is commensurate with values reported in the literature for prescribed motion studies. Nonsinusoidal foil pitching motions were found to be superior to sinusoidal motions. Efficiencies exceeding 41% were found using angle-of-attack control, and nonsinusoidal angle-of-attack profiles were found to be superior. The key to improving the efficiency of energy extraction from the flow is to control the timing of the formation and location of the leading-edge vortex at crucial times during the flapping cycle and the interaction of the vortex with the trailing edge. Simulations using Reynolds-averaged Navier–Stokes turbulence modeling suggest that the performance is maintained or only slightly reduced at Re=1.1×106.

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Numerical Simulation of a Straight-Bladed Vertical-Axis Water Turbine Operating in a 2 m/s Current


Marco Raciti Castelli and Ernesto Benini – Applied Mechanics and Materials, June 2013

Abstract

The present work proposes a full campaign of simulation of a Darrieus-type Vertical-Axis Water Turbine (VAWaterT) operating in an open flow-field. After describing the computational model and the relative validation procedure, a complete campaign of simulations based on full RANS unsteady calculations is presented for a three-bladed rotor architecture, characterized by a NACA 0025 blade profile. Flow field characteristics are investigated for several values of tip speed ratio and for a constant unperturbed free-stream water velocity of 2 m/s. Finally, the torque coefficient generated from the three blades is determined for each simulated angular velocity, allowing the calculation of the rotor power-curve. Keywords: Vertical-Axis Water Turbine, hydrokinetic technology, CFD, NACA 0025.

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Power measurement of hydrokinetic turbines with free-surface and blockage effect


Amir Hossein Birjandi, Eric Louis Bibeau, Vijay Chatoorgoon, and Anurag Kumar – Ocean Engineering, September 2013

Abstract

Vertical hydrokinetic turbines in an array that extends from one side of a channel or river to the other side of it experience a fixed blockage effect as a result of the adjacent turbines and a variable free-surface effect due to water level changes above turbines. For tidal applications, the water level above turbine blades changes continuously throughout the day; for river applications, the water level changes on a seasonal basis. In this study, a vertical turbine operating in an array of turbines with one diameter lateral distance between two adjacent turbines is modeled. The model turbine is tested in a water tunnel at various water levels. Results show that the water level reduction improves the power coefficient of the turbine when the turbine is fully submerged—the power coefficient increases due to the free-surface effect, with trends in agreement with the one-dimensional actuator-disc flow theory. However, the power coefficient decreases significantly when the turbine is only partially submerged. In this particular condition, the entrained air into the water by turbine blades separates the water from the blade surface. A high-speed camera visualizes the flow separation while a transducer measures the instantaneous torque of the turbine.

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Performance of Combined Water Turbine with Semielliptic Section of the Savonius Rotor


Kaprawi Sahim, Dyos Santoso, and Agus Radentan – International Journal of Rotating Machinery, May 2013

Abstract

The Darrieus turbine is a suitable power generation in free stream flow because it is simple in construction, but it has the disadvantage of its small starting torque. The Savonius turbine has a high starting torque but the efficiency is smaller than that of Darrieus turbine. To improve the starting torque of Darrieus turbine, the Savonius buckets are introduced into the Darrieus turbine and the combined turbine is called Darrieus-Savonius turbine. In this study, three semielliptic sections of aspect ratio 0.8 were used for Savonius bucket while the Darrieus blade used three wings of airfoil NACA 0015. The Darrieus-Savonius turbine’s performances were studied experimentally in an irrigation canal of South Sumatera, Indonesia. The results show that the distance of Savonius buckets from the shaft centre influences performance of combined turbine, and the attachment angle of Savonius rotor made important variation of turbine performance.

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