Micropower From Tidal Turbines

2013 ◽  
Author(s):  
Brian L. Polagye ◽  
Robert J. Cavagnaro ◽  
Adam L. Niblick
Keyword(s):  
Tidal Current ◽  
Cross Flow ◽  
Open Water ◽  
Turbine Rotor ◽  
Power Performance ◽  
Tidal Turbines ◽  
Performance Curves ◽  
Laboratory Flume ◽  
Optimal Efficiency ◽  
Utility Scale

In addition to utility-scale power generation (e.g., rated capacities greater than 106 W), there are also possibilities for tidal current generation at the micro-scale (e.g., rated capacities less than 102 W) that could provide power to autonomous oceanographic instrumentation. This paper presents performance characteristics of a high-solidity, helical, cross-flow turbine rotor for a tidal current micropower system. Studies are conducted on a 1/4-scale turbine in a laboratory flume and a full-scale turbine prototype using open-water tows. Results suggest this type of turbine rotor can achieve efficiencies as high as 25% and can smoothly self-start at water velocities less than 0.5 m/s. The sharp peak around optimal efficiency displayed by the power performance curves suggests a need for generator control in a micropower system using this type of rotor.

Experimental study of the duct-effects of the tidal current turbines in multi-row-staggered layout

2020 ◽  
Author(s):  
Yaling Chen ◽  
Binliang Lin ◽  
Jinxi Guo
Keyword(s):  
Tidal Current ◽  
Turbine Rotor ◽  
Power Performance ◽  
Tidal Current Energy ◽  
Tidal Turbines ◽  
Initial Stage ◽  
Tidal Turbine ◽  
Wake Zone ◽  
The Stability ◽  
Current Energy

<p>Tidal turbine array was optimized to increase the power production in order to improve the commercial competitivity of tidal current energy with other forms of energy generation. Due to duct-effects, the power performance of turbines in the staggered layout was better than that of the aligned layout. However, shear layer with enhanced turbulence occurred between the duct zone and isolated wake zone downstream, which had influence on the performance stability and increased the fatigue failure of tidal turbines. The study conducted a series of laboratory experiments to investigate the duct-effects of tidal turbines located in multi-row array with staggered layout. The turbine rotor was represented by porous disc. The flow thrust and time-varying velocity were measured using micro strain gauge and acoustic doppler velometer, respectively. Results showed that the flow was accelerated between turbines with the increment around 20% behind the first row, while the duct-effects were weakened as distance increased downstream. The shear-induced turbulence was enlarged by the duct-effect when it diffused mainly towards individual wake zone at the initial stage. As the turbulence filled the whole individual wake zones, it diffused rapidly to lateral sides and jointed together, and the turbulence intensity across the array wake was significantly higher than that of the free flow. Correspondingly, the performance of turbine rotor located downstream was improved limitedly by the duct-effects, and the stability was reduced clearly. It indicated that the advantage of the duct-effect induced in the staggered layout was limited in the near wake as the lateral interval between two turbine centres was 2 times of rotor diameter.</p><p>Keywords<strong>:</strong> Turbine rotor array; Staggered layout; Duct-effects; Turbine performance; Shear-induced turbulence</p>

scholarly journals Passive flow control mechanisms with bioinspired flexible blades in cross-flow tidal turbines

2021 ◽  
Vol 62 (5) ◽  
Author(s):  
Stefan Hoerner ◽  
Shokoofeh Abbaszadeh ◽  
Olivier Cleynen ◽  
Cyrille Bonamy ◽  
Thierry Maître ◽  
...  
Keyword(s):  
Turbine Blades ◽  
Cross Flow ◽  
Tidal Energy ◽  
Control Mechanisms ◽  
Passive Flow Control ◽  
Turbine Efficiency ◽  
Tidal Turbines ◽  
Passive Flow ◽  
Axial Turbines ◽  
The Cost

Abstract State-of-the-art technologies for wind and tidal energy exploitation focus mostly on axial turbines. However, cross-flow hydrokinetic tidal turbines possess interesting features, such as higher area-based power density in array installations and shallow water, as well as a generally simpler design. Up to now, the highly unsteady flow conditions and cyclic blade stall have hindered deployment at large scales because of the resulting low single-turbine efficiency and fatigue failure challenges. Concepts exist which overcome these drawbacks by actively controlling the flow, at the cost of increased mechatronical complexity. Here, we propose a bioinspired approach with hyperflexible turbine blades. The rotor naturally adapts to the flow through deformation, reducing flow separation and stall in a passive manner. This results in higher efficiency and increased turbine lifetime through decreased structural loads, without compromising on the simplicity of the design. Graphic abstract

scholarly journals Cross-Flow Tidal Turbines with Highly Flexible Blades—Experimental Flow Field Investigations at Strong Fluid–Structure Interactions

Energies ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 797
Author(s):  
Stefan Hoerner ◽  
Iring Kösters ◽  
Laure Vignal ◽  
Olivier Cleynen ◽  
Shokoofeh Abbaszadeh ◽  
...  
Keyword(s):  
Flow Field ◽  
High Speed ◽  
Cross Flow ◽  
Speed Ratio ◽  
Fluid Structure Interactions ◽  
Dimensional Parameter ◽  
Fluid Structure ◽  
Passive Flow Control ◽  
Tidal Turbines ◽  
Tidal Turbine

Oscillating hydrofoils were installed in a water tunnel as a surrogate model for a hydrokinetic cross-flow tidal turbine, enabling the study of the effect of flexible blades on the performance of those devices with high ecological potential. The study focuses on a single tip-speed ratio (equal to 2), the key non-dimensional parameter describing the operating point, and solidity (equal to 1.5), quantifying the robustness of the turbine shape. Both parameters are standard values for cross-flow tidal turbines. Those lead to highly dynamic characteristics in the flow field dominated by dynamic stall. The flow field is investigated at the blade level using high-speed particle image velocimetry measurements. Strong fluid–structure interactions lead to significant structural deformations and highly modified flow fields. The flexibility of the blades is shown to significantly reduce the duration of the periodic stall regime; this observation is achieved through systematic comparison of the flow field, with a quantitative evaluation of the degree of chaotic changes in the wake. In this manner, the study provides insights into the mechanisms of the passive flow control achieved through blade flexibility in cross-flow turbines.

scholarly journals Increasing Gas–Solids Mass Transfer in Fluidized Beds by Application of Confined Fluidization—A Feasibility Study

2019 ◽  
Vol 9 (4) ◽  
pp. 634 ◽  
Author(s):  
Jesper Aronsson ◽  
David Pallarès ◽  
Magnus Rydén ◽  
Anders Lyngfelt
Keyword(s):  
Mass Transfer ◽  
Fluidized Bed ◽  
Fluidized Beds ◽  
Cross Flow ◽  
Active Role ◽  
High Density ◽  
Low Density ◽  
Olivine Sand ◽  
Bed Material ◽  
Utility Scale

Fluidized bed applications where the bed material plays an active role in chemical reactions, e.g. chemical looping combustion, have seen an increase in interest over the past decade. When these processes are to be scaled up to industrial or utility scale mass transfer between the gas and solids phases can become a limitation for conversion. Confined fluidized beds were conceptualized for other purposes in the 1960’s but are yet to be applied to these recent technologies. Here it is investigated if they can prove useful to increase mass transfer but also if they are feasible from other perspectives such as pressure drop increase and solids throughflow. Four spherical packing solids, 6.35–25.4 mm in diameter at two different densities, were tested. For mass transfer experiments the fluidizing air was humidified and the water adsorption rate onto silica gel particles acting as fluidizing solids was measured. Olivine sand was used in further experiments measuring segregation of solids and packing, and maximum vertical crossflow of solids. It was found that mass transfer increased by a factor of 1.9–3.8 with packing solids as compared to a non-packed reference. With high-density packing, fluidizing solids voidage inside the packing was found to be up to 58% higher than in a conventional fluidized bed. Low density packing material favoured its flotsam segregation and with it higher fluidization velocities yield better mixing between packing and fluidizing solids. Maximum vertical cross-flow was found to be significantly higher with low density packing that fluidized, than with stationary high-density packing. Conclusively, the prospect of using confined fluidized beds for improving mass transfer looks promising from both performance and practical standpoints.

Behavior of Adult American Shad (Alosa sapidissima) Homing to the Connecticut River from Long Island Sound

1973 ◽  
Vol 30 (12) ◽  
pp. 1847-1860 ◽  
Author(s):  
Julian J. Dodson ◽  
William C. Leggett
Keyword(s):  
Tidal Current ◽  
Open Water ◽  
American Shad ◽  
Behavior Patterns ◽  
Connecticut River ◽  
Directed Movement ◽  
Alosa Sapidissima ◽  
Preferred Direction ◽  
Tidal Current Velocity ◽  
Ultrasonic Tracking

The migratory behavior of American shad (Alosa sapidissima) approaching their natal river during the final saltwater stage of the spawning migration was studied using ultrasonic tracking and conventional tagging procedures. Initial displacement of most sonic-tagged shad released without displacement adjacent to and 10 km west of the Connecticut River was not in the direction of the home river. These fish, however, homed successfully to the Connecticut River as did dart-tagged shad released in the same areas.Shad exhibited two major behavior patterns; countercurrent orientation in response to the reversing tidal current and adjustment of swimming speed to changes in tidal velocity. Countercurrent orientation was equally significant during daylight and darkness, whereas the adjustment of swimming speeds to tidal current velocity was more significant during daylight than darkness.Shad tracked to the west exhibited a westerly bias inherent in the basic open water behavior patterns. Shad exhibited a greater degree of directed movement when oriented against the ebb tide and adjusted their swimming speeds to exceed the ebb tide velocity and to approximately equal the flood tide velocity. Shad tracked to the east exhibited the same major behavior patterns but with the opposite directional bias.A hypothesis is presented suggesting that the location of the home river is achieved by means of a nonrandom search. Environmental clues indicative of the Connecticut River act to establish a preferred direction of displacement while the actual unidirectional displacement is achieved by reference to the rate and direction of tidal currents.

Current Velocity in Streams and the Composition of Benthic Algal Mats

1986 ◽  
Vol 43 (6) ◽  
pp. 1156-1162 ◽  
Author(s):  
Michael A. Reiter ◽  
Robert E. Carlson
Keyword(s):  
Current Velocity ◽  
Free Water ◽  
Open Water ◽  
Dry Weight ◽  
Taxonomic Diversity ◽  
Taxonomic Composition ◽  
Water Velocity ◽  
Algal Mats ◽  
Laboratory Flume ◽  
Algal Mat

Water velocity is commonly accepted as a factor in the development of benthic algal mats in streams. Within a stream, two different zones of velocity are observed: the free-water velocity of the open water and the local velocity near the stream substrate. A closed laboratory flume system was used to observe the taxonomic composition of benthic algal mats and corresponding changes in the local velocities under different free-water velocities. As the algal mat developed under each experimental velocity, local velocities diminished and eventually became equal in all sections, while free-water velocities remained different. After a period of maximum taxonomic diversity during the first 2 wk of mat development, taxonomic composition, relative abundance of the taxa, and dry weight biomass became increasingly similar in the three velocity regimes, although the mats appeared different upon casual observation. Differences in composition and morphology in natural algal mats may not result from differences in current velocity, and the idea of a "closed monolayer" algal mat may not be appropriate in all situations.

scholarly journals Wind–Water Experimental Analysis of Small SC-Darrieus Turbine: An Approach for Energy Production in Urban Systems

2021 ◽  
Vol 13 (9) ◽  
pp. 5256
Author(s):  
Eduardo Blanco-Marigorta ◽  
Ahmed Gharib-Yosry ◽  
Aitor Fernández-Jiménez ◽  
Rodolfo Espina-Valdés ◽  
Eduardo Álvarez-Álvarez
Keyword(s):  
Wind Tunnel ◽  
Urban Communities ◽  
Smart Cities ◽  
Water Channel ◽  
Open Water ◽  
Turbine Rotor ◽  
Urban Systems ◽  
Water Current ◽  
Flume Tests ◽  
Compact Size

Smart cities have a significant impact on the future of renewable energies as terms such as sustainability and energy saving steadily become more common. In this regard, both wind and hydrokinetic compact-size turbines can play important roles in urban communities by providing energy to nearby consumption points in an environmentally suitable manner. To evaluate the operation of a Darrieus turbine rotor as a wind or hydro microgenerator, a series of wind tunnel and water current flume tests were performed. Power and characteristic curves were obtained for all test conditions. In the wind tests, all curves seemed to be identical, which means that the turbine rotor works properly under open-field conditions. Two blockage correction equations were applied to the water channel tests that were performed under blockage values ranging from 0.2 to 0.35 to estimate the operational behavior in open water. Finally, it has been demonstrated that, with the condition of maintaining the Reynolds number between experiments in the wind tunnel and water flume, the turbine wind characteristics represents the its operation in open-water conditions.

Numerical Study of Vertical Axis Wind Turbine Rotor Configuration

2013 ◽  
Vol 859 ◽  
pp. 28-32
Author(s):  
Yi Mei ◽  
Jian Jun Qu ◽  
Xiao Ya Liu
Keyword(s):  
Wind Turbine ◽  
Urban Areas ◽  
Numerical Study ◽  
Vertical Axis ◽  
Turbine Rotor ◽  
Radius Ratio ◽  
Speed Ratio ◽  
Wind Condition ◽  
Vertical Axis Wind Turbine ◽  
Power Performance

This paper presents a numerical study of a vertical axis wind rotor configuration. Below constant wind condition 8m/s, rotor power performance was investigated over variable turbine configurations. Illustrated by the simulation, increasing rotor cord to radius ratio or blade numbers will enhance the generation of vortexes and flow separation on blades, leading to the significant degradation of turbine performance. It can be conclude form the numerical analysis, a vertical axis wind turbine with high height to radius ratio applied in urban areas experienced better performance when operating in optimal tip speed ratio, with rotor cord to radius ratio between 0.2 and 0.4 and blade number of 3 or 4.

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