Assessment of Tidal Current Resources: Case Studies of Estuarine and Coastal Sites

2007 ◽  
Vol 18 (2) ◽  
pp. 233-249
Author(s):  
Jack Hardisty
Keyword(s):  
Shallow Water ◽  
Accurate Determination ◽  
Axial Flow ◽  
Sensitivity Analyses ◽  
Energy Output ◽  
Small Scale ◽  
Stream Power ◽  
Industry Standards ◽  
Tidal Stream ◽  
Scale Design

The potential for tidal stream power in North Western European waters is large and a number of axial flow, vertical rotor and oscillating hydroplane schemes are approaching full scale design and construction. The accurate determination of the available or potential fluid power is being addressed by, in particular, the regulatory bodies as they move towards the establishment of industry standards and the identification and designation of licensing areas. A generic formulation is developed here which utilises Admiralty tidal diamond data and the arithmetic summation of harmonics due to the lunar semi-diurnal, the solar semi-diurnal and (for shallow water and estuarine sites) the lunar quarter diurnal components. Numerical and sensitivity analyses show that the long term potential power is sensitive to the amplitudes of the harmonics but insensitive to the frequencies and phase differences. The results are applied to estuarine sites off Immingham and at Hull Roads in the Humber and to a shallow water, coastal site off Weston-super-Mare in the Bristol Channel. The results indicate that the shore side energy output from a small scale, meso-generation, 100 m2 capture area device with 60% efficiency varies from about 600 MWha–1 in the Bristol Channel to about 900 MWha–1 in the Humber where the ebb dominated tide flows for longer durations and at slightly higher speeds.

Diffusion Experiments with a Global Discontinuous Galerkin Shallow-Water Model

2009 ◽  
Vol 137 (10) ◽  
pp. 3339-3350 ◽  
Author(s):  
Ramachandran D. Nair
Keyword(s):  
Shallow Water ◽  
Discontinuous Galerkin ◽  
Water Model ◽  
Order System ◽  
Small Scale ◽  
Shallow Water Model ◽  
First Order ◽  
Advection Diffusion Equation ◽  
Diffusion Scheme ◽  
Cubed Sphere

Abstract A second-order diffusion scheme is developed for the discontinuous Galerkin (DG) global shallow-water model. The shallow-water equations are discretized on the cubed sphere tiled with quadrilateral elements relying on a nonorthogonal curvilinear coordinate system. In the viscous shallow-water model the diffusion terms (viscous fluxes) are approximated with two different approaches: 1) the element-wise localized discretization without considering the interelement contributions and 2) the discretization based on the local discontinuous Galerkin (LDG) method. In the LDG formulation the advection–diffusion equation is solved as a first-order system. All of the curvature terms resulting from the cubed-sphere geometry are incorporated into the first-order system. The effectiveness of each diffusion scheme is studied using the standard shallow-water test cases. The approach of element-wise localized discretization of the diffusion term is easy to implement but found to be less effective, and with relatively high diffusion coefficients, it can adversely affect the solution. The shallow-water tests show that the LDG scheme converges monotonically and that the rate of convergence is dependent on the coefficient of diffusion. Also the LDG scheme successfully eliminates small-scale noise, and the simulated results are smooth and comparable to the reference solution.

Fluttering Amplitude Amplification by Utilizing Flapping Moment in Flutter-Driven Triboelectric Nanogenerator

2021 ◽  
Author(s):  
Yi Zhang ◽  
Ka Chung Chan ◽  
Sau Chung Fu ◽  
Christopher Yu Hang Chao
Keyword(s):  
Flow Velocity ◽  
High Speed ◽  
Aerodynamic Force ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Open Circuit ◽  
Energy Output ◽  
Small Scale ◽  
Triboelectric Nanogenerator ◽  
Peak Value

Abstract Flutter-driven triboelectric nanogenerator (FTENG) is one of the most promising methods to harvest small-scale wind energy. Wind causes self-fluttering motion of a flag in the FTENG to generate electricity by contact electrification. A lot of studies have been conducted to enhance the energy output by increasing the surface charge density of the flag, but only a few researches tried to increase the converting efficiency by enlarging the flapping motion. In this study, we show that by simply replacing the rigid flagpole in the FTENG with a flexible flagpole, the energy conversion efficiency is augmented and the energy output is enhanced. It is found that when the flag flutters, the flagpole also undergoes aerodynamic force. The lift force generated from the fluttering flag applies a periodic rotational moment on the flagpole, and causes the flagpole to vibrate. The vibration of the flagpole, in turn amplifies the flutter of the flag. Both the fluttering dynamics of the flags with rigid and flexible flagpoles have been recorded by a high-speed camera. When the flag was held by a flexible flagpole, the fluttering amplitude and the contact area between the flag and electrode plates were increased. The energy enhancement increased as the flow velocity increased and the enhancement can be 113 times when the wind velocity is 10 m/s. The thickness of the flagpole was investigated. An optimal output of open-circuit voltage reaching 1128 V (peak-to-peak value) or 312.40 V (RMS value), and short-circuit current reaching 127.67 μA (peak-to-peak value) or 31.99 μA (RMS value) at 12.21 m/s flow velocity was achieved. This research presents a simple design to enhance the output performance of an FTENG by amplifying the fluttering amplitude. Based on the performance obtained in this study, the improved FTENG has the potential to apply in a smart city for driving electronic devices as a power source for IoT applications.

1-D Model Analysis of Tesla Turbine for Small Scale Organic Rankine Cycle (ORC) System

2017 ◽  
Author(s):  
Jian Song ◽  
Chun-wei Gu
Keyword(s):  
Large Scale ◽  
Low Cost ◽  
Organic Rankine Cycle ◽  
Axial Flow ◽  
Rankine Cycle ◽  
Expansion Ratio ◽  
Working Fluid ◽  
Small Scale ◽  
Low Grade ◽  
D Model

Energy shortage and environmental deterioration are two crucial issues that the developing world has to face. In order to solve these problems, conversion of low grade energy is attracting broad attention. Among all of the existing technologies, Organic Rankine Cycle (ORC) has been proven to be one of the most effective methods for the utilization of low grade heat sources. Turbine is a key component in ORC system and it plays an important role in system performance. Traditional turbine expanders, the axial flow turbine and the radial inflow turbine are typically selected in large scale ORC systems. However, in small and micro scale systems, traditional turbine expanders are not suitable due to large flow loss and high rotation speed. In this case, Tesla turbine allows a low-cost and reliable design for the organic expander that could be an attractive option for small scale ORC systems. A 1-D model of Tesla turbine is presented in this paper, which mainly focuses on the flow characteristics and the momentum transfer. This study improves the 1-D model, taking the nozzle limit expansion ratio into consideration, which is related to the installation angle of the nozzle and the specific heat ratio of the working fluid. The improved model is used to analyze Tesla turbine performance and predict turbine efficiency. Thermodynamic analysis is conducted for a small scale ORC system. The simulation results reveal that the ORC system can generate a considerable net power output. Therefore, Tesla turbine can be regarded as a potential choice to be applied in small scale ORC systems.

Mapping shallow water bubbling reefs – a method comparison between topobathymetric lidar and multibeam echosounder

2021 ◽  
Author(s):  
Mikkel Skovgaard Andersen ◽  
Lars Øbro Hansen ◽  
Zyad Al-Hamdani ◽  
Signe Schilling Hansen ◽  
Manfred Niederwieser ◽  
...  
Keyword(s):  
Shallow Water ◽  
Habitat Type ◽  
High Energy ◽  
Survey Method ◽  
Sidescan Sonar ◽  
Small Scale ◽  
Lidar Data ◽  
Multibeam Echosounder ◽  
Full Coverage ◽  
Spatial Coverage

<p>Bubbling reefs are submarine structures formed by aggregating carbonate resulting from leaking gases. The reef formations can form pillars rising several meters above the sea floor. They support a high diversity of benthic communities, and in the EU Habitat Directive they are specifically mentioned as a natural habitat type that require conservation.</p><p>Knowledge about the presence, locations and shape of bubbling reefs are usually obtained by geophysical surveying using multibeam echosounder (MBES), sidescan sonar and/or seismic acquisition systems, combined with ground truth verification. However, this traditional survey method is time consuming, especially for full coverage surveys in shallow water. Full coverage surveys are a requirement to capture the bubbling reefs due to their relatively small spatial extent. Besides, traditional geophysical vessel borne surveys have their limitations in shallow water due to low spatial coverage and vessel draft.</p><p>In recent years, airborne topobathymetric (green wavelength) lidar has emerged as a new possible surveying method in shallow water (e.g. Andersen et al., 2017). Compared to vessel borne MBES, full coverage lidar surveys can be conducted within hours instead of days/weeks, while also including full coverage in the shallow water and a seamless transition between land and water. Thus, topobathymetric lidar may be a good choice for carrying out full coverage surveys in large shallow water areas. However, the accuracy and the resolution of the collected dataset are important in these surveys, not least when mapping small scale features such as bubbling reefs.</p><p>In this study, we investigated the potential of mapping bubbling reefs in shallow water (<10 m) using topobathymetric lidar. The main objective was to assess the performance of airborne topobathymetric lidar to detect and resolve small scale objects, i.e. bubbling reefs, by comparison to MBES data. Both MBES and lidar data were acquired in spring 2019 in a designated Natura 2000 area close to Hirsholmene in the northern Kattegat region in Denmark. The comparison of the two datasets included a quantification of the accuracy, and an assessment of the performance for mapping bubbling reefs.</p><p> </p><p>Reference:</p><p>Andersen M.S., Gergely A., Al-Hamdani Z., Steinbacher F., Larsen L.R., Ernstsen V.B. (2017). Processing and performance of topobathymetric lidar data for geomorphometric and morphological classification in a high-energy tidal environment. Hydrology and Earth System Sciences, 21: 43-63, DOI: 10.5194/hess-21-43-2017.</p>

scholarly journals Numerical Investigation of Pipelines Modeling in Small-Scale Concentrated Solar Combined Heat and Power Plants

Energies ◽  
2020 ◽  
Vol 13 (2) ◽  
pp. 429 ◽  
Author(s):  
Roberto Tascioni ◽  
Luca Cioccolanti ◽  
Luca Del Zotto ◽  
Emanuele Habib
Keyword(s):  
Flow Rate ◽  
Power Plants ◽  
Winter Season ◽  
Electric Energy ◽  
Combined Heat And Power ◽  
Heat Transfer Fluid ◽  
Energy Output ◽  
Small Scale ◽  
Longitudinal Model ◽  
Lumped Model

In this paper four different detailed models of pipelines are proposed and compared to assess the thermal losses in small-scale concentrated solar combined heat and power plants. Indeed, previous numerical analyses carried out by some of the authors have revealed the high impact of pipelines on the performance of these plants because of their thermal inertia. Hence, in this work the proposed models are firstly compared to each other for varying temperature increase and mass flow rate. Such comparison shows that the one-dimensional (1D) longitudinal model is in good agreement with the results of the more detailed two-dimensional (2D) model at any temperature gradient for heat transfer fluid velocities higher than 0.1 m/s whilst the lumped model agrees only at velocities higher than 1 m/s. Then, the 1D longitudinal model is implemented in a quasi-steady-state Simulink model of an innovative microscale concentrated solar combined heat and power plant and its performances evaluated. Compared to the results obtained using the Simscape library model of the tube, the performances of the plant show appreciable discrepancies during the winter season. Indeed, whenever the longitudinal thermal gradient of the fluid inside the pipeline is high (as at part-load conditions in winter season), the lumped model becomes inaccurate with more than 20% of deviation of the thermal losses and 30% of the organic Rankine cycle (ORC) electric energy output with respect to the 1D longitudinal model. Therefore, the analysis proves that an hybrid model able to switch from a 1D longitudinal model to a zero-dimensional (0D) model with delay based on the fluid flow rate is recommended to obtain results accurate enough whilst limiting the computational efforts.

scholarly journals Development of Automatic Solar Tracking System for Small Solar Energy System

2018 ◽  
Vol 7 (3.18) ◽  
pp. 11
Author(s):  
Musse Mohamud Ahmed ◽  
Mohammad Kamrul Hasan ◽  
Mohammad Shafiq
Keyword(s):  
Solar Energy ◽  
High Efficiency ◽  
Tracking System ◽  
Energy System ◽  
Maximum Energy ◽  
Solar Panel ◽  
Energy Output ◽  
Small Scale ◽  
Angular Movement ◽  
Solar Tracking

The main purpose of this paper is to present a novel idea that is based on design and development of an automatic solar tracker system that tracks the Sun's energy for maximum energy output achievement. In this paper, a novel automatic solar tracking system has been developed for small-scale solar energy system. The hardware part and programming part have been concurrently developed in order for the solar tracking system to be possible for it to operate accurately. Arduino Uno R3, Sensor Shield V4 Digital Analog Module, LDR (Light Dependent Resistor), MPU-6050 6DOF 3 Axis Gyroscope has been used for tracking the angular sun movement as shown in Fig. 1. Accelerometer, High-Efficiency Solar Panel, and Tower Pro MG90S Servo Motor have been used for the hardware part. High-level programming language has been embedded in the hardware to operate the tracking system effectively. The tracking system has shown significant improvement of energy delivery to solar panel comparing to the conventional method. All the results will be shown in the full paper. There are three contributions the research presented in this paper which are, i.e. perfect tracking system, the comparison between the static and tracking system and the development of Gyroscope angular movement system which tracks the angular movement of the sun along with another tracking system.  

scholarly journals Hydrodynamic Effects of Tidal-Stream Power Extraction for Varying Turbine Operating Conditions

Energies ◽  
2020 ◽  
Vol 13 (12) ◽  
pp. 3240
Author(s):  
Lilia Flores Mateos ◽  
Michael Hartnett
Keyword(s):  
Thrust Force ◽  
Operating Conditions ◽  
Blockage Ratio ◽  
Stream Power ◽  
Power Extraction ◽  
Tidal Stream ◽  
Electrical Generation ◽  
Hydrodynamic Effects ◽  
Turbine Wake ◽  
Tidal Stream Power

Realistic evaluation of tidal-stream power extraction effects on local hydrodynamics requires the inclusion of the turbine’s operating conditions (TOC). An alternative approach for simulating the turbine’s array energy capture at a regional scale, momentum sink-TOC, is used to assess the impact of power extraction. The method computes a non-constant thrust force calculated based on the turbine’s operating conditions, and it uses the wake induction factor and blockage ratio to characterise the performance of a turbine. Additionally, the momentum sink-TOC relates the changes produced by power extraction, on the velocity and sea surface within the turbine’s near-field extension, to the turbine’s thrust force. The method was implemented in two hydrodynamic models that solved gradually varying flows (GVF) and rapidly varying flows (RVF). The local hydrodynamic effects produced by tidal-stream power extraction for varying the turbine’s operating conditions was investigated in (i) the thrust and power coefficient calculation, (ii) flow rate reduction, and (iii) tidal currents’ velocity and elevation profiles. Finally, for a turbine array that operates at optimal conditions, the potential energy resource was assessed. The maximisation of power extraction for electrical generation requires the use of an optimum turbine wake induction factor and an adequate blockage ratio, so that the power loss due to turbine wake mixing is reduced. On the other hand, the situations where limiting values of these parameters are used should be avoided as they lead to negligible power available. In terms of hydrodynamical models, an RVF solver provided a more accurate evaluation of the turbine’s operating conditions effect on local hydrodynamics. Particularly satisfactory results were obtained for a partial-fence. In the case of a fence configuration, the GVF solver was found to be a computationally economical tool to pre-assess the resource; however, caution should be taken as the solver did not accurately approximate the velocity decrease produced by energy extraction.

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