scholarly journals Eco-Engineering of Seawalls—An Opportunity for Enhanced Climate Resilience From Increased Topographic Complexity

2021 ◽  
Vol 8 ◽  
Author(s):  
Md Salauddin ◽  
John J. O’Sullivan ◽  
Soroush Abolfathi ◽  
Jonathan M. Pearson
Keyword(s):  
Wave Energy ◽  
Reference Conditions ◽  
Small Scale ◽  
Test Case ◽  
Reference Case ◽  
Wave Overtopping ◽  
Wave Energy Dissipation ◽  
Climate Resilience ◽  
Impulsive Wave ◽  
Wave Conditions

In the context of “green” approaches to coastal engineering, the term “eco-engineering” has emerged in recent years to describe the incorporation of ecological concepts (including artificially water-filled depressions and surface textured tiles on seawalls and drilled holes in sea structures) into the conventional design process for marine infrastructures. Limited studies have evaluated the potential increase in wave energy dissipation resulting from the increased hydraulic roughness of ecologically modified sea defences which could reduce wave overtopping and consequent coastal flood risks, while increasing biodiversity. This paper presents results of small-scale laboratory investigations of wave overtopping on artificially roughened seawalls. Impulsive and non-impulsive wave conditions with two deep-water wave steepness values (=0.015 and 0.06) are evaluated to simulate both swell and storm conditions in a two-dimensional wave flume with an impermeable 1:20 foreshore slope. Measurements from a plain vertical seawall are taken as the reference case. The seawall was subsequently modified to include 10 further test configurations where hydraulic effects, reflective of “eco-engineering” interventions, were simulated by progressively increasing seawall roughness with surface protrusions across three length scales and three surface densities. Measurements at the plain vertical seawall compared favorably to empirical predictions from the EurOtop II Design Manual and served as a validation of the experimental approach. Results from physical model experiments showed that increasing the length and/or density of surface protrusions reduced overtopping on seawalls. Benchmarking of test results from experiments with modified seawalls to reference conditions showed that the mean overtopping rate was reduced by up to 100% (test case where protrusion density and length were maximum) under impulsive wave conditions. Results of this study highlight the potential for eco-engineering interventions on seawalls to mitigate extreme wave overtopping hazards by dissipating additional wave energy through increased surface roughness on the structure.

scholarly journals EFFECTIVENESS OF ECO-RETROFITS IN REDUCING WAVE OVERTOPPING ON SEAWALLS

2020 ◽  
pp. 13
Author(s):  
John O'Sullivan ◽  
Md Salauddin ◽  
Soroush Abolfathi ◽  
Jonathan Pearson
Keyword(s):  
Green Infrastructure ◽  
Wave Attenuation ◽  
Reference Conditions ◽  
Ecological Engineering ◽  
Physical Modelling ◽  
Small Scale ◽  
Rock Pools ◽  
Wave Overtopping ◽  
Engineering Measures ◽  
Living Shoreline

Terms such as 'nature-based', 'living shoreline', 'green infrastructure' and 'ecological engineering' are increasingly being used to reflect biomimicry-based engineering measures in coastal defences. Innovative interventions for nature-based sea defences have included the retrofitting of man-made water filled depressions or 'vertipools' to existing seawalls (Hall et al., 2019; Naylor et al., 2017) and the addition of artificial drill-cored rock pools to intertidal breakwaters (Evans et al., 2016). Through their capacity to retain water, such measures serve to enhance biodiversity in the built environment (Browne and Chapman, 2014). Evans et al. (2016) for example, experimentally demonstrated that the introduction of artificial rock pools to an intertidal granite breakwater enhanced the levels of species richness compared to those observed on plain surfaces of the breakwater. Notwithstanding these biological benefits, the impetus for incorporation of ecologically friendly measures to existing defences remains low (Salauddin et al., 2020a). This situation could potentially change should it be shown that the addition of 'green' measures to sea defences could enhance wave attenuation and reduce wave overtopping as well as wave pressures on the coastal defence structures. This paper describes small-scale physical modelling investigations of seawalls and explores reductions in wave overtopping that could be realised by retrofitting sea defences with 'green' features (such as 'vertipools'). Surface protrusions of varying scale and density are used in the physical modelling to mimic 'green' features and the results from measurements of overtopping are benchmarked to reference conditions determined from tests on a plain seawall.

scholarly journals Extreme wave overtopping at ecologically modified sea defences

2020 ◽  
Author(s):  
Md Salauddin ◽  
John O'Sullivan ◽  
Soroush Abolfathi ◽  
Jonathan Pearson
Keyword(s):  
Coastal Areas ◽  
Random Wave ◽  
Breaking Wave ◽  
Coastal Zones ◽  
Coastal Structures ◽  
Development Fund ◽  
Wave Overtopping ◽  
Ecological Features ◽  
Impulsive Wave ◽  
Wave Conditions

<p>Damage to coastal structures and surrounding properties from wave overtopping in extreme events is expected to be exacerbated in future years as global sea levels continue to rise and the frequency of extreme meteorological events and storm surges increases.  Approaches for protecting our coastal areas have traditionally relied on the development and ongoing maintenance of ‘hard’ defences.  However, the longer-term sustainability of coastal flood management that is underpinned by such defences is increasingly being questioned both in terms of dealing with climate change and in the environmental/ ecological consequences and associated losses of biodiversity that comes with these structural defence lines in coastal areas.</p><p>The term 'nature-based' has emerged in recent years to describe biomimicry-based engineered interventions in coastal defences. For example, the addition of artificial water-filled depressions on coastal structures e.g. ‘vertipools’ on seawalls and the use of ‘drill-cored rock pools in intertidal breakwaters that enhance biodiversity and species richness on sea defence surfaces and in adjacent coastal zones. While the ecological benefits of such interventions are increasingly being investigated, the additional roughness they bring to sea defences and the role of this roughness in wave energy dissipation and in the mitigation of wave overtopping remains less well studied.</p><p>Here we investigate the wave overtopping characteristics of artificially roughened seawalls in a suite of laboratory experiments conducted in a two-dimensional wave flume at the University of Warwick, UK.  An impermeable sloping foreshore with a uniform slope of 1 in 20 was constructed in front of a vertical seawall. The seawall was subsequently modified by including 10 no. different test combinations of surface protrusions of varying scale and surface density, replicating ‘green’ measures suitable for retrofitting to existing seawalls.  Wave overtopping was measured for each test.  All tests comprised approximately 1000 JONSWAP pseudo-random wave sequences. Both impulsive and non-impulsive wave conditions were considered in experiments with two constant deep-water wave steepness values of 2% and 5%.</p><p>Results from benchmark (plain seawalls) experiments showed an overall good agreement with predictions from new overtopping manual, EurOtop II, the European empirical design guidance for wave overtopping of sea defences and related structures.  However, test results for the ecologically modified sea defences under impulsive (breaking) wave conditions showed significant reductions (up to factor 4) in overtopping compared to predictions from EurOtop codes.  Reductions in overtopping for artificially roughened defences under non-impulsive wave conditions were less conclusive.  Overall, results indicate that there can be a dual benefit in retrofitting sea defences with ecological features, the first being enhanced biodiversity in the coastal zone and the second being reduced flood risk in coastal areas from reductions in overtopping, particularly for breaking wave conditions.</p><p>The work in this paper is being undertaken as part of the Interreg funded Ecostructure project (www.ecostructureproject.eu), part-funded by the European Regional Development Fund through the Ireland Wales Cooperation Programme 2014-2020.</p>

scholarly journals A broadbanded pressure differential wave energy converter based on dielectric elastomer generators

2021 ◽  
Author(s):  
Michele Righi ◽  
Giacomo Moretti ◽  
David Forehand ◽  
Lorenzo Agostini ◽  
Rocco Vertechy ◽  
...  
Keyword(s):  
Wave Energy ◽  
Large Deformations ◽  
Dielectric Elastomer ◽  
Wave Energy Converter ◽  
Pressure Differential ◽  
Design Stage ◽  
Small Scale ◽  
Energy Converter ◽  
Wide Range ◽  
The Waves

AbstractDielectric elastomer generators (DEGs) are a promising option for the implementation of affordable and reliable sea wave energy converters (WECs), as they show considerable promise in replacing expensive and inefficient power take-off systems with cheap direct-drive generators. This paper introduces a concept of a pressure differential wave energy converter, equipped with a DEG power take-off operating in direct contact with sea water. The device consists of a closed submerged air chamber, with a fluid-directing duct and a deformable DEG power take-off mounted on its top surface. The DEG is cyclically deformed by wave-induced pressure, thus acting both as the power take-off and as a deformable interface with the waves. This layout allows the partial balancing of the stiffness due to the DEG’s elasticity with the negative hydrostatic stiffness contribution associated with the displacement of the water column on top of the DEG. This feature makes it possible to design devices in which the DEG exhibits large deformations over a wide range of excitation frequencies, potentially achieving large power capture in a wide range of sea states. We propose a modelling approach for the system that relies on potential-flow theory and electroelasticity theory. This model makes it possible to predict the system dynamic response in different operational conditions and it is computationally efficient to perform iterative and repeated simulations, which are required at the design stage of a new WEC. We performed tests on a small-scale prototype in a wave tank with the aim of investigating the fluid–structure interaction between the DEG membrane and the waves in dynamical conditions and validating the numerical model. The experimental results proved that the device exhibits large deformations of the DEG power take-off over a broad range of monochromatic and panchromatic sea states. The proposed model demonstrates good agreement with the experimental data, hence proving its suitability and effectiveness as a design and prediction tool.

scholarly journals Using a Groundwater Adjusted Water Balance Approach and Copulas to Evaluate Spatial Patterns and Dependence Structures in Remote Sensing Derived Evapotranspiration Products

2021 ◽  
Vol 13 (5) ◽  
pp. 853
Author(s):  
Mohsen Soltani ◽  
Julian Koch ◽  
Simon Stisen
Keyword(s):  
Remote Sensing ◽  
Water Balance ◽  
Spatial Pattern ◽  
Spatial Patterns ◽  
Principal Component ◽  
Small Scale ◽  
Dependence Structure ◽  
Test Case ◽  
Catchment Scale ◽  
Balance Approach

This study aims to improve the standard water balance evapotranspiration (WB ET) estimate, which is typically used as benchmark data for catchment-scale ET estimation, by accounting for net intercatchment groundwater flow in the ET calculation. Using the modified WB ET approach, we examine errors and shortcomings associated with the long-term annual mean (2002–2014) spatial patterns of three remote-sensing (RS) MODIS-based ET products from MODIS16, PML_V2, and TSEB algorithms at 1 km spatial resolution over Denmark, as a test case for small-scale, energy-limited regions. Our results indicate that the novel approach of adding groundwater net in water balance ET calculation results in a more trustworthy ET spatial pattern. This is especially relevant for smaller catchments where groundwater net can be a significant component of the catchment water balance. Nevertheless, large discrepancies are observed both amongst RS ET datasets and compared to modified water balance ET spatial pattern at the national scale; however, catchment-scale analysis highlights that difference in RS ET and WB ET decreases with increasing catchment size and that 90%, 87%, and 93% of all catchments have ∆ET < ±150 mm/year for MODIS16, PML_V2, and TSEB, respectively. In addition, Copula approach captures a nonlinear structure of the joint relationship with multiple densities amongst the RS/WB ET products, showing a complex dependence structure (correlation); however, among the three RS ET datasets, MODIS16 ET shows a closer spatial pattern to the modified WB ET, as identified by a principal component analysis also. This study will help improve the water balance approach by the addition of groundwater net in the ET estimation and contribute to better understand the true correlations amongst RS/WB ET products especially over energy-limited environments.

scholarly journals The Role of Biophilic Agents in Building a Green Resilient City; the Case of Birmingham, UK

2021 ◽  
Vol 13 (9) ◽  
pp. 5033
Author(s):  
Linda Novosadová ◽  
Wim van der Knaap
Keyword(s):  
Urban Planning ◽  
Urban Governance ◽  
Small Scale ◽  
Climate Resilience ◽  
Natural Land ◽  
Negative Impacts ◽  
Community Projects ◽  
Business As Usual ◽  
The City

The present research offers an exploration into the biophilic approach and the role of its agents in urban planning in questions of building a green, resilient urban environment. Biophilia, the innate need of humans to connect with nature, coined by Edgar O. Wilson in 1984, is a concept that has been used in urban governance through institutions, agents’ behaviours, activities and systems to make the environment nature-inclusive. Therefore, it leads to green, resilient environments and to making cities more sustainable. Due to an increasing population, space within and around cities keeps on being urbanised, replacing natural land cover with concrete surfaces. These changes to land use influence and stress the environment, its components, and consequently impact the overall resilience of the space. To understand the interactions and address the adverse impacts these changes might have, it is necessary to identify and define the environment’s components: the institutions, systems, and agents. This paper exemplifies the biophilic approach through a case study in the city of Birmingham, United Kingdom and its biophilic agents. Using the categorisation of agents, the data obtained through in-situ interviews with local professionals provided details on the agent fabric and their dynamics with the other two environments’ components within the climate resilience framework. The qualitative analysis demonstrates the ways biophilic agents act upon and interact within the environment in the realm of urban planning and influence building a climate-resilient city. Their activities range from small-scale community projects for improving their neighbourhood to public administration programs focusing on regenerating and regreening the city. From individuals advocating for and educating on biophilic approach, to private organisations challenging the business-as-usual regulations, it appeared that in Birmingham the biophilic approach has found its representatives in every agent category. Overall, the activities they perform in the environment define their role in building resilience. Nonetheless, the role of biophilic agents appears to be one of the major challengers to the urban design’s status quo and the business-as-usual of urban governance. Researching the environment, focused on agents and their behaviour and activities based on nature as inspiration in addressing climate change on a city level, is an opposite approach to searching and addressing the negative impacts of human activity on the environment. This focus can provide visibility of the local human activities that enhance resilience, while these are becoming a valuable input to city governance and planning, with the potential of scaling it up to other cities and on to regional, national, and global levels.

Wave Energy Hyperbaric Device for Electricity Production

2007 ◽  
Author(s):  
Segen F. Estefen ◽  
Paulo Roberto da Costa ◽  
Eliab Ricarte ◽  
Marcelo M. Pinheiro
Keyword(s):  
Power Generation ◽  
Wave Energy ◽  
Experimental Results ◽  
Electricity Production ◽  
Scale Model ◽  
Small Scale ◽  
Regular Waves ◽  
Hyperbaric Chamber ◽  
Small Scale Model

Wave energy is a renewable and non-polluting source and its use is being studied in different countries. The paper presents an overview on the harnessing of energy from waves and the activities associated with setting up a plant for extracting energy from waves in Port of Pecem, on the coast of Ceara State, Brazil. The technology employed is based on storing water under pressure in a hyperbaric chamber, from which a controlled jet of water drives a standard turbine. The wave resource at the proposed location is presented in terms of statistics data obtained from previous monitoring. The device components are described and small scale model tested under regular waves representatives of the installation region. Based on the experimental results values of prescribed pressures are identified in order to optimize the power generation.

scholarly journals Optimizing the Power Take Off of a Wave Energy Converter With Regard to the Wave Climate

2005 ◽  
Vol 128 (1) ◽  
pp. 56-64 ◽  
Author(s):  
Gaelle Duclos ◽  
Aurelien Babarit ◽  
Alain H. Clément
Keyword(s):  
Wave Energy ◽  
Simple Wave ◽  
Wave Climate ◽  
Wave Energy Converter ◽  
Optimal Parameters ◽  
Energy Converter ◽  
Wave Energy Converters ◽  
Classical Wave ◽  
Project Site ◽  
Wave Conditions

Considered as a source of renewable energy, wave is a resource featuring high variability at all time scales. Furthermore wave climate also changes significantly from place to place. Wave energy converters are very often tuned to suit the more frequent significant wave period at the project site. In this paper we show that optimizing the device necessitates accounting for all possible wave conditions weighted by their annual occurrence frequency, as generally given by the classical wave climate scatter diagrams. A generic and very simple wave energy converter is considered here. It is shown how the optimal parameters can be different considering whether all wave conditions are accounted for or not, whether the device is controlled or not, whether the productive motion is limited or not. We also show how they depend on the area where the device is to be deployed, by applying the same method to three sites with very different wave climate.

scholarly journals Increase of power and efficiency of the 900 MW supercritical power plant through incorporation of the ORC

2013 ◽  
Vol 34 (4) ◽  
pp. 51-71 ◽  
Author(s):  
Paweł Ziółkowski ◽  
Dariusz Mikielewicz ◽  
Jarosław Mikielewicz
Keyword(s):  
Power Plant ◽  
Heat Source ◽  
Steam Turbine ◽  
Hybrid System ◽  
Heat Recovery ◽  
Reference Conditions ◽  
Hot Water ◽  
Operational Parameters ◽  
Reference Case ◽  
Unit Power

Abstract The objective of the paper is to analyse thermodynamical and operational parameters of the supercritical power plant with reference conditions as well as following the introduction of the hybrid system incorporating ORC. In ORC the upper heat source is a stream of hot water from the system of heat recovery having temperature of 90 °C, which is additionally aided by heat from the bleeds of the steam turbine. Thermodynamical analysis of the supercritical plant with and without incorporation of ORC was accomplished using computational flow mechanics numerical codes. Investigated were six working fluids such as propane, isobutane, pentane, ethanol, R236ea and R245fa. In the course of calculations determined were primarily the increase of the unit power and efficiency for the reference case and that with the ORC.

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