scholarly journals Bardsey – an island in a strong tidal stream: Underestimating coastal tides due to unresolved topography

2020 ◽  
Author(s):  
J. A. Mattias Green ◽  
David T. Pugh
Keyword(s):  
Satellite Altimetry ◽  
Energy Resource ◽  
Tidal Energy ◽  
Small Scale ◽  
Phase Lag ◽  
Altimetry Data ◽  
Wake Effect ◽  
Tidal Dissipation ◽  
North West ◽  
Tidal Stream

Abstract. Bardsey Island is located at the western end of the Llŷn Peninsula in north-west Wales Separated from the mainland by a channel some 3 km wide, it is surrounded by reversing tidal streams of up to 4 ms−1 at spring tides. These local hydrodynamic details and their consequences are unresolved by satellite altimetry, nor are they represented in regional tidal models. Here we look at the effects of the island in the strong tidal stream in terms of the formation and shedding of eddies, and the budgets for tidal energy dissipation. We show, using local observation and a satellite altimetry constrained product, that the island has a large impact on the tidal stream, and that even the latest altimetry database seriously under-represents the tidal stream due to the island not being resolved. The effect of the island leads to an underestimate of the current speed in the altimetry data in the channel of up to a factor of three, depending on tidal state, and the average tidal energy resource is underestimated by a factor 6. The observed tidal amplitudes are higher at the mainland than at the island, and there is a detectable phase lag in the tide across the island – this effect is not seen in the altimetry data. The underestimate of the tide in the altimetry data has consequences for tidal dissipation and wake effect computation and show that local observations are key to correctly estimate tidal energetics around small-scale coastal topography.

scholarly journals Bardsey – an island in a strong tidal stream: underestimating coastal tides due to unresolved topography

Ocean Science ◽  
2020 ◽  
Vol 16 (6) ◽  
pp. 1337-1345
Author(s):  
J. A. Mattias Green ◽  
David T. Pugh
Keyword(s):  
Satellite Altimetry ◽  
Energy Resource ◽  
Tidal Energy ◽  
Small Scale ◽  
Phase Lag ◽  
Wake Effect ◽  
Tidal Dissipation ◽  
Tidal Energetics ◽  
Tidal Stream ◽  
Tidal Streams

Abstract. Bardsey Island is located at the western end of the Llŷn Peninsula in northwestern Wales. Separated from the mainland by a channel that is some 3 km wide, it is surrounded by reversing tidal streams of up to 4 m s−1 during spring tides. These local hydrodynamic details and their consequences are unresolved by satellite altimetry and are not represented in regional tidal models. Here we look at the effects of the island on the strong tidal stream in terms of the budgets for tidal energy dissipation and the formation and shedding of eddies. We show, using local observations and a satellite-altimetry-constrained product (TPXO9), that the island has a large impact on the tidal stream and that even in this latest altimetry-constrained product the derived tidal stream is under-represented due to the island not being resolved. The effect of the island leads to an underestimate of the current speed in the TPXO9 data in the channel of up to a factor of 2.5, depending on the timing in the spring–neap cycle, and the average tidal energy resource is underestimated by a factor up to 14. The observed tidal amplitudes are higher at the mainland than at the island, and there is a detectable phase lag in the tide across the island; this effect is not seen in the TPXO9 data. The underestimate of the tide in the TPXO9 data has consequences for tidal dissipation and wake effect computation and shows that local observations are key to correctly estimating tidal energetics around small-scale coastal topography.

scholarly journals Effect of waves on the tidal energy resource at a planned tidal stream array

2015 ◽  
Vol 75 ◽  
pp. 626-639 ◽  
Author(s):  
M. Reza Hashemi ◽  
Simon P. Neill ◽  
Peter E. Robins ◽  
Alan G. Davies ◽  
Matt J. Lewis
Keyword(s):  
Energy Resource ◽  
Tidal Energy ◽  
Tidal Stream

scholarly journals The Tidal Stream Energy Resource of the Fromveur Strait—A Review

2020 ◽  
Vol 8 (12) ◽  
pp. 1037
Author(s):  
Nicolas Guillou ◽  
Jean-Frédéric Charpentier ◽  
Mohamed Benbouzid
Keyword(s):  
Energy Resource ◽  
Tidal Energy ◽  
Energy Output ◽  
Wake Interactions ◽  
Tidal Stream ◽  
Technical Specifications ◽  
Tidal Stream Energy ◽  
Key Steps ◽  
A Site

Refined assessments of the available tidal stream energy resource are required to optimize turbines design and guarantee successful implementations and operations of devices in the marine environment. Investigations primary focused on identifying areas with maximum current speeds. However, further information may be reached by exhibiting (i) resource temporal variability, (ii) superimposed effects of meteo-oceanographic conditions (including especially wind-generated surface-gravity waves), and (iii) potential environmental impacts of operating turbines at the regional (e.g., changes in sediment transport and surrounding seabed features, effects on marine water quality, etc.) and local (wake-wake interactions and energy output) scales. These aspects are here investigated by reviewing a series of research studies dedicated to the Fromveur Strait off western Brittany, a region with strong potential for tidal array development along the coast of France. Particular attention is dedicated to the exploitation of combined in-situ and remote-sensing observations and numerical simulations. Beyond a site specific characterization of the tidal stream energy resource, this review promotes a series of original approaches and analysis methods for turbines optimization, thus complementing technical specifications to secure the key steps of a tidal energy project and promote the growth of a reliable tidal stream energy exploitation.

scholarly journals Spatio-temporal variability of tidal-stream energy in north-western Europe

2020 ◽  
Vol 378 (2178) ◽  
pp. 20190493 ◽  
Author(s):  
Nicolas Guillou ◽  
Simon P. Neill ◽  
Jérôme Thiébot
Keyword(s):  
Temporal Variability ◽  
Western Europe ◽  
Energy Resource ◽  
Phase Relationship ◽  
Tidal Energy ◽  
The North ◽  
Tidal Stream ◽  
Tidal Stream Energy ◽  
Spatio Temporal ◽  
North Western

Initial selection of tidal stream energy sites is primarily based on identifying areas with the maximum current speeds. However, optimal design and deployment of turbines requires detailed investigations of the temporal variability of the available resource, focusing on areas with reduced variability, and hence the potential for more continuous energy supply. These aspects are investigated here for some of the most promising sites for tidal array development across the north-western European shelf seas: the Alderney Race, the Fromveur Strait, the Pentland Firth and the channels of Orkney. Particular attention was dedicated to asymmetry between the flood and ebb phases of the tidal cycle (due to the phase relationship between M 2 and M 4 constituents), and spring-neap variability of the available resource (due to M 2 and S 2 compound tides). A series of high-resolution models were exploited to (i) produce a detailed harmonic database of these three components, and (ii) characterize, using energy resource metrics, temporal variability of the available power density. There was a clear contrast between the Alderney Race, with reduced temporal variability over semi-diurnal and fortnightly time scales, and sites in western Brittany and North Scotland which, due to increased variability, appeared less attractive for optimal energy conversion. This article is part of the theme issue ‘New insights on tidal dynamics and tidal energy harvesting in the Alderney Race’.

scholarly journals Dispatchability, Energy Security, and Reduced Capital Cost in Tidal-Wind and Tidal-Solar Energy Farms

Energies ◽  
2021 ◽  
Vol 14 (24) ◽  
pp. 8504
Author(s):  
Peter Osman ◽  
Jennifer A. Hayward ◽  
Irene Penesis ◽  
Philip Marsh ◽  
Mark A. Hemer ◽  
...  
Keyword(s):  
Case Studies ◽  
Energy Content ◽  
Capital Expenditure ◽  
Energy Resource ◽  
Tidal Energy ◽  
Solar Pv ◽  
Stream Power ◽  
Low Velocity ◽  
Power Generators ◽  
Tidal Stream

The global tidal energy resource for electricity generation is small, and converting tidal kinetic energy to electricity is expensive compared to solar-photovoltaic or land-based wind turbine generators. However, as the renewable energy content in electricity supplies grows, the need to stabilise these supplies increases. This paper describes tidal energy’s potential to reduce intermittency and variability in electricity supplied from solar and wind power farms while lowering the capital expenditure needed to improve dispatchability. The paper provides a model and hypothetical case studies to demonstrate how sharing energy storage between tidal stream power generators and wind or solar power generators can mitigate the level, frequency, and duration of power loss from wind or solar PV farms. The improvements in dispatchability use tidal energy’s innate regularity and take account of tidal asymmetry and extended duration low-velocity neap tides. The case studies are based on a national assessment of Australian tidal energy resources carried out from 2018 to 2021.

Identification of Tidal Energy Resources using Satellite Altimetry Data for Indonesian Seas

2018 ◽  
Author(s):  
Inovasita Alifdini ◽  
Ratu Almira Kismawardhani ◽  
Anindya Wirasatriya ◽  
Denny Nugroho Sugianto ◽  
Omar bin Yaakob ◽  
...  
Keyword(s):  
Satellite Altimetry ◽  
Tidal Energy ◽  
Energy Resources ◽  
Altimetry Data ◽  
Indonesian Seas ◽  
Satellite Altimetry Data

scholarly journals Appraising the extractable tidal energy resource of the UK's western coastal waters

2013 ◽  
Vol 371 (1985) ◽  
pp. 20120181 ◽  
Author(s):  
Nick Yates ◽  
Ian Walkington ◽  
Richard Burrows ◽  
Judith Wolf
Keyword(s):  
Coastal Waters ◽  
Energy Resource ◽  
Tidal Energy ◽  
Pilot Scale ◽  
Water Model ◽  
Two Dimensional ◽  
Tidal Model ◽  
Main Emphasis ◽  
Tidal Stream ◽  
Tidal Streams

A two-dimensional west coast tidal model, built on the ADCIRC platform (an unstructured grid two-dimensional depth-integrated shallow water model), has been developed to examine the scope for reliable and fully predictable electricity generation from UK coastal waters using an ambitious combination of estuary barrages, tidal lagoons and tidal stream generator arrays. The main emphasis has been towards conjunctive operation of major estuary barrages, initially including the presence of pilot-scale tidal stream developments, though ambitious exploitation of extensive tidal streams has also been explored.

Profitability and Efficiency Analyses of Small Scale Rice processing units in Ngoketunjia Division, North West Region, Cameroon.

2014 ◽  
Vol 3 (2) ◽  
pp. 177-182
Author(s):  
Bime M.J ◽  
Fon D.E ◽  
Ngalim S.B ◽  
Ongla J
Keyword(s):  
Value Added ◽  
Primary Data ◽  
Small Scale ◽  
Fixed Cost ◽  
Cost Ratio ◽  
Parboiled Rice ◽  
North West ◽  
Benefit Cost Ratio ◽  
Benefit Cost ◽  
Rice Processing

Rice production and processing over the years has been on an increase with more small holders entering the business. This study on profitability of processing and marketing of small scale rice processors had as objective to analyse the profitability levels of rice processing and marketing by small scale processors, determine the value added to the commodity at each stage  and also identify the constraints faced by these processors. The study used primary data collected using well-structured questionnaire from millers only, miller traders for white/parboiled rice through a multistage sampling technique. Results showed that the net processing income (3,151,201), value added (8,147,456) and efficiency (138) for miller-traders of white rice was highest, followed by miller-traders for parboiled rice and lastly millers only. Results further showed that millers only had Benefit/cost ratio of 0.4 indicating that milling only is not profitable due to small quantities milled, and high fixed cost. Miller-traders for parboiled rice had a benefit/cost ratio of 2.3 implying that their venture is most profitable. Based on the results, it was recommended that millers only should purchase large quantities of paddy to enable them reduce the overhead cost. Also the services of parboilers should reflect in the sales price of parboiled rice so that the parboiling services can be paid for.

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