scholarly journals Experimental Assessment of Flow, Performance, and Loads for Tidal Turbines in a Closely-Spaced Array

Energies ◽  
2020 ◽  
Vol 13 (8) ◽  
pp. 1977 ◽  
Author(s):  
Donald R. Noble ◽  
Samuel Draycott ◽  
Anup Nambiar ◽  
Brian G. Sellar ◽  
Jeffrey Steynor ◽  
...  
Keyword(s):  
Numerical Models ◽  
Ocean Energy ◽  
Complex Flow ◽  
Flow Measurements ◽  
Power Extraction ◽  
Tidal Turbines ◽  
Tidal Stream ◽  
Flow Through ◽  
And Performance ◽  
Structural Loading

Tidal stream turbines are subject to complex flow conditions, particularly when installed in staggered array configurations where the downstream turbines are affected by the wake and/or bypass flow of upstream turbines. This work presents, for the first time, methods for and results from the physical testing of three 1/15 scale instrumented turbines configured in a closely-spaced staggered array, and demonstrates experimentally that increased power extraction can be achieved through reduced array separation. A comprehensive set of flow measurements was taken during several weeks testing in the FloWave Ocean Energy Research Facility, with different configurations of turbines installed in the tank in a current of 0.8 m/s, to understand the effect that the front turbines have on flow through the array and on the inflow to the centrally placed rearmost turbine. Loads on the turbine structure, rotor, and blade roots were measured along with the rotational speed of the rotor to assess concurrently in real-time the effects of flow and array geometry on structural loading and performance. Operating in this closely-spaced array was found to improve the power delivered by the rear turbine by 5.7–10.4% with a corresponding increase in the thrust loading on the rotor of 4.8–7.3% around the peak power operating point. The experimental methods developed and results arising from this work will also be useful for further scale-testing elsewhere, validating numerical models, and for understanding the performance and loading of full-scale tidal stream turbines in arrays.

Design of a Tidal Turbine Array for the Bohai Strait, China

2018 ◽  
Author(s):  
Lei Chen ◽  
Paul A. J. Bonar ◽  
Thomas A. A. Adcock
Keyword(s):  
Design Strategies ◽  
Stream Power ◽  
Tidal Turbines ◽  
Actuator Disc ◽  
Tidal Turbine ◽  
Tidal Stream ◽  
Flow Through ◽  
Turbine Arrays ◽  
Theoretical Results ◽  
Bohai Strait

In this paper, we consider array design strategies to maximise the power available to turbines placed in the Bohai Strait, which is considered to be one of China’s most promising candidate sites for tidal stream power. The discontinuous Galerkin version of the open-source hydrodynamic model ADCIRC is used to simulate flow through the strait and tidal turbines are introduced using a sub-grid scale actuator disc model. New design algorithms based on key theoretical results are used to build large arrays, which are then compared in terms of both the collective power output and the power produced per turbine. The results of the analysis are used to draw general conclusions about the optimal design of tidal turbine arrays.

scholarly journals Hybrid Neural Fuzzy Design-Based Rotational Speed Control of a Tidal Stream Generator Plant

2018 ◽  
Vol 10 (10) ◽  
pp. 3746 ◽  
Author(s):  
Khaoula Ghefiri ◽  
Izaskun Garrido ◽  
Soufiene Bouallègue ◽  
Joseph Haggège ◽  
Aitor Garrido
Keyword(s):  
Control Strategies ◽  
Reference Tracking ◽  
Power Extraction ◽  
Research Areas ◽  
Tidal Turbines ◽  
Control Scheme ◽  
Tidal Turbine ◽  
Tidal Stream ◽  
Rotational Speed Control ◽  
Neural Fuzzy

Artificial Intelligence techniques have shown outstanding results for solving many tasks in a wide variety of research areas. Its excellent capabilities for the purpose of robust pattern recognition which make them suitable for many complex renewable energy systems. In this context, the Simulation of Tidal Turbine in a Digital Environment seeks to make the tidal turbines competitive by driving up the extracted power associated with an adequate control. An increment in power extraction can only be archived by improved understanding of the behaviors of key components of the turbine power-train (blades, pitch-control, bearings, seals, gearboxes, generators and power-electronics). Whilst many of these components are used in wind turbines, the loading regime for a tidal turbine is quite different. This article presents a novel hybrid Neural Fuzzy design to control turbine power-trains with the objective of accurately deriving and improving the generated power. In addition, the proposed control scheme constitutes a basis for optimizing the turbine control approaches to maximize the output power production. Two study cases based on two realistic tidal sites are presented to test these control strategies. The simulation results prove the effectiveness of the investigated schemes, which present an improved power extraction capability and an effective reference tracking against disturbance.

scholarly journals INVESTIGATION OF THE ENERGY POTENTIAL FROM TIDAL STREAM CURRENTS IN INDONESIA

2017 ◽  
pp. 10 ◽  
Author(s):  
Kadir Orhan ◽  
Roberto Mayerle ◽  
Rangaswami Narayanan ◽  
Wahyu Pandoe
Keyword(s):  
Numerical Models ◽  
Three Dimensional ◽  
Stream Power ◽  
Energy Potential ◽  
Density Maximum ◽  
Indonesian Seas ◽  
Tidal Turbines ◽  
Tidal Stream ◽  
Power Densities ◽  
Tidal Stream Power

In this paper, an advanced methodology developed for the assessment of tidal stream resources is applied to several straits between Indian Ocean and inner Indonesian seas. Due to the high current velocities up to 3-4 m/s, the straits are particularly promising for the efficient generation of electric power. Tidal stream power potentials are evaluated on the basis of calibrated and validated high-resolution, three-dimensional numerical models. It was found that the straits under investigation have tremendous potential for the development of renewable energy production. Suitable locations for the installation of the turbines are identified in all the straits, and sites have been ranked based on the level of power density. Maximum power densities are observed in the Bali Strait, exceeding around 10kw/m2. Horizontal axis tidal turbines with a cut-in velocity of 1m/s are considered in the estimations. The highest total extractable power resulted equal to about 1,260MW in the Strait of Alas. Preliminary assessments showed that the power production at the straits under investigation is likely to exceed previous predictions reaching around 5,000MW.

scholarly journals Micro Axial Turbine Hill Charts: Affinity Laws, Experiments and CFD Simulations for Different Diameters

Energies ◽  
2019 ◽  
Vol 12 (15) ◽  
pp. 2908 ◽  
Author(s):  
Mariana Simão ◽  
Helena M. Ramos
Keyword(s):  
Water Supply ◽  
Numerical Models ◽  
Water Supply Systems ◽  
Hydraulic Systems ◽  
Flow Measurements ◽  
Axial Turbine ◽  
Mean Values ◽  
Power Extraction ◽  
Different Diameters ◽  
Supply Systems

Water supply systems are one of the main hydraulic systems with significant potential for the installation of micro-hydropower devices. Although there are already some mini-hydropower applications in water supply systems, it is still a huge potential that continues to be under-exploited. The arrangement based on an axial turbine, such as an inline tubular propeller, with different diameters and rotational speeds suitable to exploit the existing potential in the water sector, is fully tested. The turbine with the nominal diameter of 85 mm was analysed through experimental campaigns and numerical models for a large range of heads and flow measurements to access its performance. A good correlation between the physical model and the numerical results were obtained, with mean values of deviation less than 5% regarding flow, mechanical power and efficiency. These results were extrapolated to other similar turbine with 170 mm, using affinity laws to investigate the power extraction performance. Both geometries were also numerically investigated using computational fluid dynamics (CFD) models and comparisons were made between the affinity model and experimental results. The results identified differences when compared with the classical affinity curves. Therefore, new formulations based on affinity equations were proposed for the analyzed axial turbine with different diameters without imposing a constant turbine efficiency since actually it does not keep constant as CFD calibrated model proved. Compared to experimental test efficiencies for different rotational speeds, the new proposed affinity laws provided a maximum error of 12% for both diameters.

On LES Methods Applied to Seal Geometries

2012 ◽  
Author(s):  
James Tyacke ◽  
Richard Jefferson-Loveday ◽  
Paul Tucker
Keyword(s):  
Maximum Error ◽  
Labyrinth Seal ◽  
Navier Stokes ◽  
Final Solution ◽  
Complex Flow ◽  
Eddy Simulation ◽  
Wide Range ◽  
Large Eddy ◽  
Rans Models ◽  
Flow Through

Nine Large Eddy Simulation (LES) methods are used to simulate flow through two labyrinth seal geometries and are compared with a wide range of Reynolds-Averaged Navier-Stokes (RANS) solutions. These involve one-equation, two-equation and Reynolds Stress RANS models. Also applied are linear and nonlinear pure LES models, hybrid RANS-Numerical-LES (RANS-NLES) and Numerical-LES (NLES). RANS is found to have a maximum error and a scatter of 20%. A similar level of scatter is also found among the same turbulence model implemented in different codes. In a design context, this makes RANS unusable as a final solution. Results show that LES and RANS-NLES is capable of accurately predicting flow behaviour of two seals with a scatter of less than 5%. The complex flow physics gives rise to both laminar and turbulent zones making most LES models inappropriate. Nonetheless, this is found to have minimal tangible results impact. In accord with experimental observations, the ability of LES to find multiple solutions due to solution non-uniqueness is also observed.

scholarly journals Hydropower, Geothermal, and Ocean Energy

MRS Bulletin ◽  
2008 ◽  
Vol 33 (4) ◽  
pp. 389-395 ◽  
Author(s):  
Ralph E.H. Sims
Keyword(s):  
Renewable Energy ◽  
Large Scale ◽  
New Technologies ◽  
Materials Science ◽  
Development Stage ◽  
Design Development ◽  
Ocean Energy ◽  
Improve Design ◽  
And Performance ◽  
Improve Reliability

AbstractSome forms of renewable energy have long contributed to electricity generation, whereas others are just emerging. For example, large-scale hydropower is a mature technology generating about 16% of global electricity, and many smaller scale systems are also being installed worldwide. Future opportunities to improve the technology are limited but include upgrading of existing plants to gain greater performance efficiencies and reduced maintenance. Geothermal energy, widely used for power generation and direct heat applications, is also mature, but new technologies could improve plant designs, extend their lifetimes, and improve reliability. By contrast, ocean energy is an emerging renewable energy technology. Design, development, and testing of a myriad of devices remain mainly in the research and development stage, with many opportunities for materials science to improve design and performance, reduce costly maintenance procedures, and extend plant operating lifetimes under the harsh marine environment.

Flow Through a Realistic Arterial Geometry With Two Aneurysms: Mixing Characteristics and Residence Times

2001 ◽  
Author(s):  
V. D. Butty ◽  
K. Gudjonsson ◽  
P. Buchel ◽  
V. B. Makhijani ◽  
Y. Ventikos ◽  
...  
Keyword(s):  
Residence Time ◽  
Computational Simulation ◽  
Region Of Interest ◽  
Preliminary Evidence ◽  
Basins Of Attraction ◽  
Complex Flow ◽  
Human Right ◽  
Motion Patterns ◽  
Secondary Motion ◽  
Flow Through

Abstract In the present work, we are presenting computational simulation results for the flow in a human right internal carotid artery, exhibiting two saccular aneurysms close to each other. We utilize computer tomography data in order to extract a realistic geometric description of the region of interest. Aspects of the flow inside the aneurysms are discussed in connection to secondary motion patterns and inflow-outflow regimes. We construct residence time maps that exhibit strong non-uniformity, connected to the existence of fluid entering only the first, only the second, or both aneurysms. Preliminary evidence that the inflow-outflow patterns of the two aneurysms may be leading to particularly complex flow and to chaotic mixing is discussed, based on the apparent properties of both the residence time map iso-contours and the basins of attraction of the two aneurysms. Particular attention is paid in establishing grid independence for the computed results and for this reason a second order spatial discretization scheme is utilized, with resolutions ranging from approximately 110,000 to 1,070,000 tetrahedra.

The Research of Energy Conversion and Heat Transfer in the Ceramic Foams of Solar Energy Converter

2011 ◽  
Author(s):  
Yangbo Deng ◽  
Fengmin Su ◽  
Chunji Yan
Keyword(s):  
Heat Transfer ◽  
Numerical Model ◽  
Solar Radiation ◽  
Solar Energy ◽  
Numerical Models ◽  
Air Flow ◽  
Energy Converter ◽  
Ceramic Foams ◽  
Numerical Studies ◽  
Flow Through

The solar energy converter in Concentrated Solar Power (CSP) system, applies the solid frame structure of the ceramic foams to receive the concentrated solar radiation, convert it into thermal energy, and heat the air flow through the ceramic foams by convection heat transfer. In this paper, first, the pressure drops in the studied ceramic foams were measured under all kinds of flow condition. Based on the experimental results, an empirical numerical model was built for the air flow through ceramic foams. Second, a 3-D numerical model was built, for the receiving and conversion of the solar energy in the ceramic foams of the solar energy converter. Third, applying two aforementioned numerical models, the numerical studies of the thermal performance were carried out, for the solar energy converter filled with the ceramic foams, and results show that the structure parameters of the ceramic foams, the effective reflective area and the solar radiation intensity of the solar concentrator, have direct impacts on the absorptivity and conversion efficiency of the solar energy in the solar energy converter. And the results of the numerical studies are found to be in reasonable agreement with the experimental measurements. This paper will provide a reference for the design and manufacture of the solar energy converter with the ceramic foams.

Hemodynamics in the abdominal aorta: a comparison of in vitro and in vivo measurements

1994 ◽  
Vol 76 (4) ◽  
pp. 1520-1527 ◽  
Author(s):  
J. E. Moore ◽  
S. E. Maier ◽  
D. N. Ku ◽  
P. Boesiger
Keyword(s):  
Abdominal Aorta ◽  
Velocity Profiles ◽  
Flow Reversal ◽  
Infrarenal Aorta ◽  
Complex Flow ◽  
Flow Measurements ◽  
In Vivo Measurements ◽  
Made In

In vivo measurements of blood velocity profiles are difficult to obtain and interpret, since the parameters that govern the normally highly complex flow situation may not be fully quantified or understood at the time of measurement. In vitro flow models have been used often to better understand vascular hemodynamics. The assumptions made in the design of these models limit the applicability of the results. In this study, in vitro flow measurements made in a carefully designed model of the abdominal aorta were compared with in vivo measurements obtained with magnetic resonance imaging. In the suprarenal aorta, the velocity profiles were mostly forward and axisymmetric in both the in vitro and in vivo cases. In the infrarenal aorta, there was extensive flow reversal noted near the posterior wall in both cases. In the aortic bifurcation, two peaks of flow reversal were noted near the lateral posterior walls, and M-shaped velocity profiles were observed in late diastole. The in vitro and in vivo measurements exhibited good qualitative agreement. The in vitro model was accurate in modeling the in vivo hemodynamics of the abdominal aorta. The complex phenomena observed in vivo were explained on the basis of knowledge gained from the in vitro study.

Sign in / Sign up

Export Citation Format

Share Document