Investigation of array layout of tidal stream turbines on energy extraction efficiency

<p>The aim of this work is to analyse the potential impacts of tidal energy extraction on the marine environment. We wanted to put them in the broader context of the possibly greater and global ecological threat of climate change. Here, we present how very large (hypothetical) tidal stream arrays and a ''business as usual'' future climate scenario can change the hydrodynamics of a seasonally stratified shelf sea, and consequently modify ecosystem habitats and animals&#8217; behaviour.</p><p>The Scottish Shelf Model, an unstructured grid three-dimensional ocean model, has been used to reproduce the present and the future state of the NW European continental shelf. While the marine biogeochemical model ERSEM (European Regional Seas Ecosystem Model) has been used to describe the corresponding biogeochemical conditions. Four scenarios have been modelled: present conditions and projected future climate in 2050, each with and without very large scale tidal stream arrays in Scottish Waters (UK). This allows us to evaluate the potential effect of climate change and large scale energy extraction on the hydrodynamics and biogeochemistry. We found that climate change and tidal energy extraction both act in the same direction, in terms of increasing stratification due to warming and reduced mixing, however, the effect of climate change is ten times larger. Additionally, the ecological costs and benefits of these contrasting pressures on mobile predator and prey marine species are evaluated using ecological statistical models.</p>

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Food Input and Energy Extraction Efficiency in Carassius auratus

Nature ◽

10.1038/198707a0 ◽

1963 ◽

Vol 198 (4881) ◽

pp. 707-707 ◽

Cited By ~ 15

Author(s):

P. M. C. DAVIES

Keyword(s):

Carassius Auratus ◽

Extraction Efficiency ◽

Energy Extraction ◽

Food Input

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Implementation of Tidal Stream Turbines and Tidal Barrage Structures in DG-SWEM

Volume 10: Ocean Renewable Energy ◽

10.1115/omae2019-95767 ◽

2019 ◽

Cited By ~ 3

Author(s):

Andrea M. Schnabl ◽

Tulio Marcondes Moreira ◽

Dylan Wood ◽

Ethan J. Kubatko ◽

Guy T. Houlsby ◽

...

Keyword(s):

Numerical Models ◽

Shallow Water Equation ◽

Tidal Energy ◽

Head Loss ◽

Equation Model ◽

Energy Extraction ◽

Tidal Hydrodynamics ◽

Low Head ◽

Tidal Stream ◽

Two Sides

Abstract There are two approaches to extracting power from tides — either turbines are placed in areas of strong flows or turbines are placed in barrages enabling the two sides of the barrage to be closed off and a head to build up across the barrage. Both of these energy extraction approaches will have a significant back effect on the flow, and it is vital that this is correctly modelled in any numerical simulation of tidal hydrodynamics. This paper presents the inclusion of both tidal stream turbines and tidal barrages in the depth-averaged shallow water equation model DG-SWEM. We represent the head loss due to tidal stream turbines as a line discontinuity — thus we consider the turbines, and the energy lost in local wake-mixing behind the turbines, to be a sub-grid scale processes. Our code allows the inclusion of turbine power and thrust coefficients which are dependent on Froude number, turbine blockage, and velocity, but can be obtained from analytical or numerical models as well as experimental data. The barrage model modifies the existing culvert model within the code, replacing the original cross-barrier pipe equations. At the location of this boundary, velocities through sluice gates are calculated according to the orifice equation. For simulating the turbines, a Hill Chart for low head bulb turbines provided by Andritz Hydro is used. We demonstrate the implementations on both idealised geometries where it is straightforward to compare against other models and numerical simulations of real candidate sites for tidal energy in Malaysia and the Bristol Channel.

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A Two-stage Energy Extraction Circuit for Energy Harvesting in Non-Sinusoidal Excited Environments

Proceedings ◽

10.3390/proceedings2130700 ◽

2018 ◽

Vol 2 (13) ◽

pp. 700 ◽

Cited By ~ 1

Author(s):

Philipp Dorsch ◽

Toni Bartsch ◽

Florian Hubert ◽

Heinrich Milosiu ◽

Stefan J. Rupitsch

Keyword(s):

Energy Harvester ◽

Extraction Efficiency ◽

Tracking System ◽

Electrical Energy ◽

Use Case ◽

Energy Extraction ◽

Two Stage ◽

Asset Tracking ◽

Piezoelectric Energy ◽

Radio Signals

We present a two-stage energy extraction circuit for a piezoelectric energy harvester, powering an asset-tracking system. Exploiting non-sinusoidal accelerations generated by many logistic transport devices, e.g., pushcarts, forklifts, assembly belts or cars, we are able to harvest sufficient electrical energy to transmit radio signals, which will allow to track the object when it is moving. By using the proposed energy extraction circuit, the energy extraction efficiency could be improved by at least 30% compared to a single-stage solution for sinusoidal excitations. In the practical use-case, the two-stage energy extraction network performs more than four times better compared to the single staged on.

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The revived Penrose process can power the central engine in active galactic nuclei

Symposium - International Astronomical Union ◽

10.1017/s0074180900153057 ◽

1986 ◽

Vol 119 ◽

pp. 395-398

Author(s):

Sanjay M. Wagh ◽

N. Dadhich

Keyword(s):

Magnetic Field ◽

Active Galactic Nuclei ◽

Extraction Efficiency ◽

Galactic Nuclei ◽

High Energy ◽

Energy Extraction ◽

Central Engine ◽

Penrose Process ◽

The Magnetic Field ◽

Very High

Using the fact that the efficiency of the revived (Wagh et al 1985) Penrose process of energy extraction from black holes immersed in electromagnetic fields can be very high (Parthasarathy et al, 1986) we show that this process can comfortably power the ‘central engine’ in Active Galactic Nuclei. The microphysical Penrose process energized particles will be ultrarelativistic in the asymptotic frame. Hence the kinematical analysis of escaping photons by Piran and Shaham (1977) will be a good approximation to the kinematics of these particles. From this analysis one expects the energized particles to emerge within an angle∼ 40° above and below the equatorial plane. These energetic particles, which are collimated in the funnel of an accretion disk and further on by the magnetic field, then, form supersonic, relativistic, bilateral jets. The relativistic Y factor for such jets can be expected to be ∼ 2 since these ultrarelativistic particles will effectively mimick radiation in ‘dragging’ the matter already injected inside the funnel. Various implications of high energy extraction efficiency are illustrated.

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Study on Performance Enhancement of a Flapping Foil Energy Harvester Using Circulation Control

Journal of Fluids Engineering ◽

10.1115/1.4050055 ◽

2021 ◽

Vol 143 (7) ◽

Author(s):

Fangrui Shi ◽

Xiaojing Sun

Keyword(s):

Extraction Efficiency ◽

Performance Enhancement ◽

Net Energy ◽

Circulation Control ◽

Energy Extraction ◽

Injection Port ◽

Flapping Foil ◽

Momentum Coefficient ◽

Reduced Frequency ◽

Wide Range

Abstract Oscillating motion, an effective way to harvest energy, has gradually become a hotspot in bionic motion research in recent years. Means of improving the energy-extraction efficiency of a flapping foil harvester have long been a focus of researchers. This paper proposes a new flapping foil harvester with circulation control and explores the effects of different parameters on its energy-extraction capacity to improve efficiency and achieve lowest cost. Setting the injection ports on the upper and lower surfaces near the trailing edge of the foil and implementing injection control during motion, the effects of the location of the injection port, pitching amplitude, momentum coefficient, reduced frequency, and jet mode on the circulation control flapping foil are systematically investigated under the condition of a Reynolds number of 13,800. The results show that circulation control can enhance the energy-extraction efficiency of a flapping foil across a wide range of parameters, in which the location of the injection port and momentum coefficient have the most obvious influence on efficiency, followed by pitching amplitude and reduced frequency. In addition, the jet mode is a crucial factor affecting net efficiency. Relative to the constant mode, the triangular mode of circulation control has the lowest energy consumption, and the net energy-extraction efficiency reaches up to 38.77% under a reduced frequency of 0.12, which is 22.24% higher than that of the plain flapping foil.

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