scholarly journals Incorporation of a Non-Constant Thrust Force Coefficient to Assess Tidal-Stream Energy

Energies ◽  
2019 ◽  
Vol 12 (21) ◽  
pp. 4151 ◽  
Author(s):  
Lilia Flores Mateos ◽  
Michael Hartnett
Keyword(s):  
Near Field ◽  
Regional Scale ◽  
Resource Assessment ◽  
Operating Conditions ◽  
Force Coefficient ◽  
Thrust Coefficient ◽  
Power Extraction ◽  
Energy Assessment ◽  
Tidal Stream ◽  
Tidal Stream Energy

A novel method for modelling tidal-stream energy capture at the regional scale is used to evaluate the performance of two marine turbine arrays configured as a fence and a partial fence. These configurations were used to study bounded and unbounded flow scenarios, respectively. The method implemented uses turbine operating conditions (TOC) and the parametrisation of changes produced by power extraction within the turbine near-field to compute a non-constant thrust coefficient, and it is referred to as a momentum sink TOC. Additionally, the effects of using a shock-capture capability to evaluate the resource are studied by comparing the performance of a gradually varying flow (GVF) and a rapidly varying flow (RVF) solver. Tidal-stream energy assessment of bounded flow scenarios through a full fence configuration is better performed using a GVF solver, because the head drop is more accurately simulated; however, the solver underestimates velocity reductions due to power extraction. On the other hand, assessment of unbounded flow scenarios through a partial fence was better performed by the RVF solver. This scheme approximated the head drop and velocity reduction more accurately, thus suggesting that resource assessment with realistic turbine configurations requires the correct solution of the discontinuities produced in the tidal-stream by power extraction.

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.

scholarly journals Resource assessment for future generations of tidal-stream energy arrays

Energy ◽  
2015 ◽  
Vol 83 ◽  
pp. 403-415 ◽  
Author(s):  
M. Lewis ◽  
S.P. Neill ◽  
P.E. Robins ◽  
M.R. Hashemi
Keyword(s):  
Resource Assessment ◽  
Future Generations ◽  
Tidal Stream ◽  
Tidal Stream Energy

A numerical tidal stream energy assessment study for Baía de Todos os Santos, Brazil

2017 ◽  
Vol 107 ◽  
pp. 271-287 ◽  
Author(s):  
Martinho Marta-Almeida ◽  
Mauro Cirano ◽  
Carlos Guedes Soares ◽  
Guilherme C. Lessa
Keyword(s):  
Energy Assessment ◽  
Assessment Study ◽  
Tidal Stream ◽  
Tidal Stream Energy

scholarly journals Tidal stream energy resource assessment of the Anglesey Skerries

2013 ◽  
Vol 3-4 ◽  
pp. e98-e111 ◽  
Author(s):  
Sena Serhadlıoğlu ◽  
Thomas A.A. Adcock ◽  
Guy T. Houlsby ◽  
Scott Draper ◽  
Alistair G.L. Borthwick
Keyword(s):  
Energy Resource ◽  
Resource Assessment ◽  
Tidal Stream ◽  
Tidal Stream Energy

scholarly journals A theoretical and numerical approach for selecting miniaturized antenna topologies on magneto-dielectric substrates

2015 ◽  
Vol 7 (3-4) ◽  
pp. 369-377 ◽  
Author(s):  
Alex Pacini ◽  
Alessandra Costanzo ◽  
Diego Masotti
Keyword(s):  
Near Field ◽  
Dielectric Materials ◽  
Numerical Approach ◽  
Operating Conditions ◽  
Microwave Range ◽  
Dielectric Substrates ◽  
Full Wave ◽  
Miniaturized Antenna ◽  
Wavelength Radiation ◽  
Definition Of

An increasing interest is arising in developing miniaturized antennas in the microwave range. However, even when the adopted antennas dimensions are small compared with the wavelength, radiation performances have to be preserved to keep the system-operating conditions. For this purpose, magneto-dielectric materials are currently exploited as promising substrates, which allows us to reduce antenna dimensions by exploiting both relative permittivity and permeability. In this paper, we address generic antennas in resonant conditions and we develop a general theoretical approach, not based on simplified equivalent models, to establish topologies most suitable for exploiting high permeability and/or high-permittivity substrates, for miniaturization purposes. A novel definition of the region pertaining to the antenna near-field and of the associated field strength is proposed. It is then showed that radiation efficiency and bandwidth can be preserved only by a selected combinations of antenna topologies and substrate characteristics. Indeed, by the proposed independent approach, we confirm that non-dispersive magneto-dielectric materials with relative permeability greater than unit, can be efficiently adopted only by antennas that are mainly represented by equivalent magnetic sources. Conversely, if equivalent electric sources are involved, the antenna performances are significantly degraded. The theoretical results are validated by full-wave numerical simulations of reference topologies.

scholarly journals Dual-Mode Power Operation for Grid-Connected PV Systems with Adaptive DC-link Controller

2021 ◽  
Author(s):  
Mostafa Ahmed ◽  
Ibrahim Harbi ◽  
Ralph Kennel ◽  
Mohamed Abdelrahem
Keyword(s):  
Power Generation ◽  
Voltage Regulation ◽  
Operating Conditions ◽  
Switching Frequency ◽  
Atmospheric Conditions ◽  
Voltage Profile ◽  
Dual Mode ◽  
Power Extraction ◽  
Pv Systems ◽  
Power Operation

AbstractPhotovoltaic (PV) power systems are integrated with high penetration levels into the grid. This in turn encourages several modifications for grid codes to sustain grid stability and resilience. Recently, constant power management and regulation is a very common approach, which is used to limit the PV power production. Thus, this article proposes dual-mode power generation algorithm for grid-connected PV systems. The developed system considers the two-stage PV configuration for implementation, where the dual-mode power generation technique is executed within the DC–DC conversion (boost) stage. Most of the techniques adopted for dual-mode power operation employ the conventional perturb and observe method, which is known with unsatisfactory performance at fast-changing atmospheric conditions. Considering this issue, this study suggests a modified maximum power point tracker for power extraction. Furthermore, a new adaptive DC-link controller is developed to improve the DC-link voltage profile at different operating conditions. The adaptive DC-link controller is compared with the traditional PI controller for voltage regulation. The inverter control is accomplished using finite-set model predictive control with two control objectives, namely reference current tracking and switching frequency minimization. The overall control methodology is evaluated at different atmospheric and operating conditions using MATLAB/Simulink software.

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