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A Brief Review of Wave Energy
... Ocean wave energy and wave energy converters 1 Among these renewable energy sources, the potential of wave energy is giant [7]. The potential worldwide wave energy resource is estimated to be 2 TW, according to the report of Thorpe [8]. Theoretically, the global gross wave energy resource including all contributions (P gross ), gross resource excluding the areas where P≤ 5 kW/m (P) and ice-covered areas are shown in Table 1.1 [9]. ...
... Because of this, some novel mooring line configurations were developed. In [312], two hybrid mooring systems: (i) synthetic cable with a floater attached (CON1); (ii) 'S' type mooring line (with a floater and clump weight installed) 8 -182 -moored to a buoy were tested (CON2), and the results were compared with catenary mooring system. It was shown that CON1 has the lowest maximum tension, while the lowest dynamic tension was seen in CON2. ...
... The average energy flux or wave power, P w , is calculated by multiplying the energy term, E, by wave propagation speed, V g = L 2T . In this formula, T is the wave period and L is the wavelength [125]. ...
... The dispersion relationship which describes the connection between the wave period and the wavelength, L = gT 2 2π , is combined with Equation (3) and results in [125]: ...
With recent advancements in technology, energy storage for gadgets and sensors has become a challenging task. Among several alternatives, the triboelectric nanogenerators (TENG) have been recognized as one of the most reliable methods to cure conventional battery innovation’s inadequacies. A TENG transfers mechanical energy from the surrounding environment into power. Natural energy resources can empower TENGs to create a clean and conveyed energy network, which can finally facilitate the development of different remote gadgets. In this review paper, TENGs targeting various environmental energy resources are systematically summarized. First, a brief introduction is given to the ocean waves’ principles, as well as the conventional energy harvesting devices. Next, different TENG systems are discussed in details. Furthermore, hybridization of TENGs with other energy innovations such as solar cells, electromagnetic generators, piezoelectric nanogenerators and magnetic intensity are investigated as an efficient technique to improve their performance. Advantages and disadvantages of different TENG structures are explored. A high level overview is provided on the connection of TENGs with structural health monitoring, artificial intelligence and the path forward.
... Wave energy, as a promising renewable energy source, has gained attention in the global energy market due to its large power density and round-the-clock availability compared to solar and wind energy [1][2][3]. Various types of wave energy converters (WECs) were invented by research communities and companies, such as oscillating water columns, oscillating bodies, and overtopping devices [4]. Although some of them have shown technical feasibility, none has been fully commercialized. ...
A wave energy converter (WEC) comprises many components with distinct functions. The whole WEC system is complicated, as each component is also a complex subsystem. It is challenging to properly model and couple these subsystems to achieve a global simulation of the whole system. This study proposes an FMI-based co-simulation framework to tackle this challenge. Through the use of a co-simulation technique requiring minimal programming effort, a suite of numerical solvers serving for modelling various WEC components is coupled to create a comprehensive system model for a single WEC unit. The modules of the Ansys software, Aqwa and Rigid Dynamics, are employed to model hydrodynamic loads and motion responses. Simulink is utilized to model the power takeoff (PTO) system and then integrate all models into a global simulation. The capability and accuracy of the FMI-based co-simulation framework are validated against an experimental heave decay test and verified by cross-comparing a numerical model built in SESAM. Furthermore, the framework is expanded to encompass the modelling of a large-scale wave park that includes multiple WEC units. Based on a novel WEC concept called NoviOcean, two study cases of a single unit and an 18-unit wave park are investigated. Buoy motions and power performance under several regular and irregular sea states are analysed. The hydrodynamic interactions between the units are evaluated quantitatively regarding the power performance. It is found that the interactions improve the power performance, with a maximum increase of up to 36%.
... Wave energy is accepted as a concentrated form of wind energy which is generated by solar energy [4]. The amount of energy transferred and, hence, the size of the resulting waves depends on wind speed, the length of time for which the wind blows and the distance over which it blows (the ''fetch'') [5]. The wind-wave interactions is extensively explained by Mastanbroek [6]. ...
With the advance of technology, the need for energy increases every day. The ever increasing
demand for energy and also the serious level of environmental issues force energy research towards environmentally friendly renewable energy sources. The main sources of renewable energy are listed as solar, wind and wave energy. Among those, the solar and wind are already being utilized with some capacity. The only potentially good source left to explore is the wave energy. The presented work provides details on potential of wave energy and importance of control application in energy extraction from waves. The presented work focuses on modelling, simulation and control of a typical heaving wave energy converter. In this study, the heaving wave energy converter is modelled and simulation studies have been performed for phase and latching control. It has been shown that phase control performs better than latching control in all regular sea states. It has been also shown that latching control becomes a difficult control approach especially in irregular waves. For comparison of phase and latching controls only the regular waves are used. The phase control itself is also tested with the irregular waves. The results of the simulation studies are also presented in plots showing comparative study on the performance of phase and the latching control techniques.
... Additionally, significant contributions are found in the works authored by [1,[3][4][5][6]. Valuable insights into contemporary advancements in the field are also available in a report commissioned by the UK Department of Energy in 1999 [7], as well as the conclusive 2003 report by the European Thematic Network on Wave Energy [8], supported by the European Commission. Concise reviews can be found in [9][10][11][12][13]. ...
An oscillating water column (OWC) is designed for the extraction and conversion of wave energy into usable electrical power, rather than being a standalone renewable energy source. This review paper presents a comprehensive analysis of the mathematical modeling approaches employed in OWC systems, aiming to provide an in-depth understanding of the underlying principles and challenges associated with this innovative technology. A prominent classification within the realm of wave energy devices comprises OWC systems, which exhibit either fixed or floating configurations. OWC devices constitute a significant proportion of the wave energy converter prototypes currently operational offshore. Within an OWC system, a hollow structure, either permanently fixed or floating, extends below the water’s surface, creating an enclosed chamber where air is captured over the submerged inner free surface. This comprehensive study offers a thorough assessment of OWC technology in conjunction with air turbines. Additionally, the investigation delves into theoretical, computational, and experimental modeling techniques employed for analyzing OWC converters. Moreover, this review scrutinizes theoretical, computational, and experimental modeling methodologies, providing a holistic understanding of OWC converters. Ultimately, this work contributes a thorough assessment of OWC technology’s current state, accentuating its potential for efficient wave energy extraction and suggesting future research avenues.
... The concept of collecting and using ocean energy was not a new as the (WEC) wave transducer was used in 1799 and was patented [4], and the first practical form of using wave energy was by Y Masuda when he used ocean waves to power navigation buoys [5]. Ocean wave energy has the second largest potential among all ocean renewable energy sources [6] [7], and despite differing opinions, some studies have determined the amount that can be exploited as 10 -20% of the total potential. [8] 2. Technology OWC: ...
The phenomenon of climate change resulting from the increase of global warming has become one of the main problems facing the world. Where researchers and specialists have worked for many years to find a solution that reduces this phenomenon and limits its risks. It is likely that clean energy is an alternative to fossil fuel sources, which are the main source of global warming. One of the clean energy sources is ocean wave energy, which is a huge and untapped energy source, despite the possibility of extracting large energy from waves. This paper focuses on the study of deep-sea turbines and their results. A study was conducted on the capture chamber. Where this paper presents an experimental model of a water tank with certain dimensions in the university laboratories to describe the dynamic behavior of the capture chamber. The Froude number scale was used to model the dimensions and depth of the water as well as the wave properties. Through experimental work and its results show, and it was found that the power generated by the motion of the wave strength is related to the height and frequency of the wave.
... AVE energy is known to be a renewable energy resource with worldwide capacity similar to wind [1][2]. Potential for multi-MW capacity for grid supply has been demonstrated at many sites but, despite a range of demonstrator sites and devices [3][4][5], there is to date negligible commercial-scale generation of electricity from ©2023 European Wave and Tidal Energy Conference. ...
Wave energy is well known to be a renewable energy resource with worldwide capacity similar to wind. However there is to date negligible generation of electricity from wave. Many devices have been proposed without convergence on a particular design as there has been for wind. We are here concerned with a multi-float attenuator type M4 which has been widely tested in wave basins and modelled by linear diffraction/radiation methods. Potential of MW capacity for grid supply has been demonstrated at many sites. To advance development, small scale ocean tests are being planned for Albany, Western Australia where summer wind-wave conditions in King George Sound will excite the device giving principal absorption with mean periods in the range 2 - 3.5 seconds (or peak periods of 2.5 – 4.5 s). The aim is to learn about most aspects of ocean deployment from wave climate and environment planning to realistic electricity generation, albeit at kW scale. In this paper the emphasis is on the specification of electrical drive train (power take off) which requires the input of torque time variation for the wave conditions on the site, as described by a scatter diagram. First a linear time domain wave multi-float model (Fortran) is set up for the particular 121 configuration, shown in Fig. 1. Such models have been used and validated against wave basin tests for similar configurations. This is then converted into state-space form in Matlab. This is highly efficient and suited for real time PTO control in Simulink. Fig. 2 shows the main components of the electrical drive train, including the gearbox, generator, super-capacitors, power electronic converters and resistor bank to dissipate electricity. Bespoke Matlab models will be run for the wave conditions in the scatter diagram to check that components are suitably rated for normal sea-states, and are safely protected through electrical power-limiting control in high sea states. Simulated electrical generator results will be shown for typical sea states, with some power-limiting. Instrumentation will be specified. Only uni-directional waves are considered in this paper. Ultimately the efficacy of the system will be demonstrated in ocean conditions.
... The global wave energy resources are abundant, with a total available amount of 2 TW [6]. China has a vast coastline and abundant wave energy resources, with a theoretical storage capacity of about 7 × 10 8 kW, with huge development potential [7,8]. ...
A wave energy resource characterization for China’s Guangdong Coast is carried out utilizing 1-year (2020) wave data from four buoy sites. The wave heights, wave periods, wave directions, and effective wave height occurrence were analyzed using statistical methods. The wave energy spectrum methodology is used to calculate the wave power density. The wave energy level frequency and effective storage of wave energy are presented. The seasons and month variation indices are used to assess the wave power stability. The contribution of sea conditions to wave power is examined. The results indicate that the waters off Guangdong are rich in wave-related energy resources. The average wave energy density is (8.55–13.1) kW/m, and the maximum wave energy density is (94.6–624.2) kW/m. The effective reserves in winter are the largest at 1.0 × 10⁶ kW·h/m. The biggest share of wave energy is found in the sea state, with significant wave heights of 0.5–1.0 m and significant wave periods of 5–6 s. Typhoons contribute very little to yearly wave energy, yet they are significant when evaluating the dependability and durability of ocean wave energy converters.
... Wave power can be a useful predictor of shoreline change (e.g., beaches: Davidson et al., 2013;marshes: Leonardi et al., 2016), with higher wave heights and longer wave periods leading to larger wave power. Wave power is also used to assess feasibility of renewable energy generation (Ozkan and Mayo, 2019;Thorpe, 1999 Winds are also given in meteorological convention, meaning positive v values are coming from the north and positive u values are coming from the east. Wave power was then calculated using the WAVEWATCH III estimates of significant wave height and peak wave period for this location. ...
Progress in better understanding and modeling Earth surface systems requires an ongoing integration of data and numerical models. Advances are currently hampered by technical barriers that inhibit finding, accessing, and executing modeling software with related datasets. We propose a design framework for ‘Data Components’: software packages that provide access to particular research datasets or types of data. Because they use a standard interface based on the Basic Model Interface (BMI), Data Components can function as plug-and-play components within modeling frameworks to facilitate seamless data-model integration. To illustrate the design and potential applications of Data Components and their advantages, we present several case studies in Earth surface processes analysis and modeling. The results demonstrate that the Data Component design provides a consistent and efficient way to access heterogeneous datasets from multiple sources, and to seamlessly integrate them with various models. This design supports the creation of open data-model integration workflows that can be discovered, accessed, and reproduced through online data sharing platforms, which promotes data reuse and improves research transparency and reproducibility.
... In the observation data stage, people use ocean ship reports and buoy data to calculate the size of the global coastal wave power density. Thorpe [1] analyzed the WPD around the UK through observation data. Lenee-Bluhm et al. [2] used NDBC (National Data Buoy Center) and CDIP (Coastal Data Information Program) data to analyze the wave energy resources in the Pacific Ocean in the northwest of the United States. ...
Based on the third-generation wave model WAVEWATCH-III (WW3), this paper analyzes the changing trend of wave power density (WPD) in the South China Sea, which can provide necessary references for the development and utilization of wave energy resources in the future. In this study, multi-platform cross-calibrated (CCMP) wind data was used to drive WW3 to calculate the WPD of the South China Sea. The Mann-Kendall (MK) algorithm can be used to determine the mutation of WPD, and the accuracy of the CCMP wind was verified. Next, the time distribution of WPD is analyzed for the whole sea area and dominant sea area of the South China Sea, and on this basis, the dominant sea area for the development of wave energy resources in the South China Sea was studied. The results are as follows: (1) Extreme weather has a significant impact on the change of WPD in the South China Sea, and this change is likely due to the effect of extreme weather on sea temperature. (2) Dongsha Islands has the highest annual WPD value and has the greatest impact on the overall trend change of the South China Sea. (3) Integrated wave energy exploitability and safety and technology perspectives, the waters around Taiwan Strait are more suitable as the primary site for energy conversion.
... Most sea waves are generated from the action of the winds, causing swells when they act on the water for long distances [13]. When the wind stops, the waves keep going, losing energy along the way until reaching the shore. ...
Decarbonization of ports is a major goal to reduce their global carbon footprint. The port of Hvide Sande is located on the coast of the North Sea in Denmark and it has the potential to utilize various renewable energy sources. Wind and solar thermal parks are already installed there. Wave energy is an alternative to solar and wind energies and its advantage is the spatial concentration, predictability, and persistence. Heat to the town is provided by Hvide Sande Fjernvarme. In this work, it is investigated if the heat demand could be fully covered by renewable energies. Power profiles for each renewable energy resource were calculated using 30 years of re-analysis environmental data. Long, mid, and short term time series of power supply has been statistically and quantitatively examined. Considering the heat demand of Hvide Sande, the lowest frequency of zero occurrence in power generation can be ensured by the combination of wind, solar energy and wave. The article also estimated the capacity for Lithium-ion batteries. The optimal size of the battery is found by the bisection method. Finally, different combinations of renewable energy and demand as well as batteries are evaluated. The lowest zero occurrences in power production is met by the mix of three renewable energies. Also, the mix of three renewable energies significantly reduces the value of energy, required from the battery.
... Various WECs have different mechanisms and technologies for converting mechanical energy into electricity. These technologies have been reviewed by many authors [1][2][3][4][5]. ...
Facing the exhaustion of fossil energy and in the context of sustainable development, strong incentives are pushing for the development of renewable energies. Nuclear energy and fossil fuels like petroleum, coal, and natural gas provide most of the energy produced today. As a result, greenhouse gases are released and climate change becomes irreversible. Furthermore, radioactive waste disposal causes severe radiation pollution in nuclear power. Alternatives such as marine energy are more sustainable and predictable. It has none of the detrimental effects of fossil and nuclear energies and is significant in terms of environmental sustainability by defending the coastline from erosion. Here, we study the Palm Beach-Azur region near Algiers on the Mediterranean Sea. The study aims to use wave energy converters (WEC) to generate clean energy and reduce coastline erosion. The results of this study show that in the presence of wave energy converters, the wave height decreased by 0.3 m, and sediment deposition increased by 0.8 m. Thus, sand deposit prediction demonstrates that the presence of WEC decreases marine erosion and contributes to an accumulation of sediments on the coast. Moreover, this confirms that WECs can serve a dual role of extracting marine energy by converting it into electrical energy and as a defence against marine erosion. Therefore, WECs justify their efficiency both in energy production and economic and environmental profitability due to coastal protection.
... It is pointed out that solar photovoltaic panels and wind turbines can only generate electricity up to 30% of the time, while wave energy converters (WECs) can absorb energy up to 90% of the time (Drew et al., 2009;Sheng, 2019). On the other hand, the wave energy resource is giant which is estimated at 2 TW (Thorpe, 1999). Furthermore, the energy density of ocean waves is the greatest among wind and solar and wave energy loss is small during wave transmission (Clément et al., 2002). ...
A series of 1:40 model tests are carried out to study the dynamic responses of a point absorber moored by three taut nylon ropes under irregular wave conditions. The experimental results are applied to calibrate a numerical model, and then the calibrated numerical model is applied to study the influence of pretension, mooring axial stiffness, current velocity and tidal range on extreme mooring tension under head sea wave conditions. Both the global maximum method and the average conditional exceedance rate method are applied to study extreme mooring tension based on fifty 3-h fully coupled analyses. The nonlinear strain-tension curve is used in numerical simulations to consider the material non-linearities of nylon rope. To discuss the influence of axial stiffness on extreme mooring tension, nonlinear strain-tension curves of a worked rope and a new rope are studied. The numerical simulations under three current profiles are conducted to study the influence of current velocity on extreme mooring tension. It is found that the influence of axial stiffness and current velocity on extreme mooring tension is significant, and the influence of current velocity on extreme mooring tension reduces with the increase of mooring pretension.
... The gap between the market for renewable energy and the consumption of fossil fuels may soon be closed if we consider recent improvements in the renewable energy sector. The global market for alternative energy sources increased from 85 GW in 2004 to 560 GW in 2013 (excluding hydropower) [2][3][4]. With an increase from 48 to 318 GW, the wind industry took the lead in the sector. ...
Ocean energy is one potential renewable energy alternative to fossil fuels that has a more significant power generation due to its better predictability and availability. In order to harness this source, wave energy converters (WECs) have been devised and used over the past several years to generate as much energy and power as is feasible. While it is possible to install these devices in both nearshore and offshore areas, nearshore sites are more appropriate places since more severe weather occurs offshore. Determining the optimal location might be challenging when dealing with sites along the coast since they often have varying capacities for energy production. Constructing wave farms requires determining the appropriate location for WECs, which may lead us to its correct and optimum design. The WEC size, shape, and layout are factors that must be considered for installing these devices. Therefore, this review aims to explain the methodologies, advancements, and effective hydrodynamic parameters that may be used to discover the optimal configuration of WECs in nearshore locations using evolutionary algorithms (EAs).
... Interest in renewable energy sources as alternative forms of energy supply is increasing since their operation is clean and everlasting, compared to the conventional energy resources like natural gas, oil, and coal. Ocean wave energy has the second-largest potential among all ocean renewable energy sources [1]. Due to the high energy density, up to 10 times higher than solar and wind energy [2], ocean wave energy on the US coast has the potential to supply up to 64 percent (2,640 TWh/year) of the US electrical needs [3]. ...
Ocean waves are sustainable, clean, and contain a tremendous amount of energy. However, waves are typically irregular and complex, making energy harnessing difficult and inefficient in the absence of sophisticated surface measurements. Existing wave energy converters rely on static power take-off technologies, but active power take-off (PTO) control can improve energy extraction. The optimization of the PTO damping is crucial to maximizing the absorbed power. The goal of this research is to use deep reinforcement learning to actively control the PTO damping coefficient to optimize power over a specified time horizon with only one causal surface wave measurement. Deep reinforcement learning (DRL) is a subset of machine learning that combines reinforcement and deep learning and employs artificial feed-forward neural networks. The learner algorithm (agent) interacts with the environment to learn the best policy based on the actions taken and the states that result from those actions. In this research, the Twin Delayed Deep Deterministic Policy Gradient (TD3) algorithm is used, which has two hidden layers of 256 widths each and is integrated with the PTO system of a single-body point absorber device. The damping coefficient has been chosen to be the action space, and the velocity and position of the floating buoy to be the state space. A reward function is created to guide the agent through the learning process. A positive reward function is set to be the function of power absorbed by the PTO system to encourage expected behavior patterns and increase the likelihood of similar behavior being repeated. Based on the history of the time dynamics and limited knowledge of the future state based on the current wave detection sensor capabilities, the agent learns the optimal damping coefficient and helps to maximize the absorbed power.
... Onshore or fixed OWCs have been around for many years [216,219,691,774]. One of the first commercial examples of this technology was constructed in Toftestallen, Norway in 1985 [489]. ...
... Onshore or fixed OWCs have been around for many years [216,219,691,774]. One of the first commercial examples of this technology was constructed in Toftestallen, Norway in 1985 [489]. ...
... Onshore or fixed OWCs have been around for many years [216,219,691,774]. One of the first commercial examples of this technology was constructed in Toftestallen, Norway in 1985 [489]. ...
... Equations (1) and (2) were used in this paper to assess and characterize wave energy in the studying area. These equations evaluate Wave Power Density (P) expressed in kilowatts per meter of wave crest width (kW/m), indicating the wave power dependence Sustainability 2022, 14, 4687 4 of 23 on two variables: H s as significant wave height (meters) and T e as energy wave period (seconds) [41][42][43]. Wave power density may be also denoted as wave energy flux or wave energy potential [44]. ...
The complexity and variability of ocean waves make wave energy harvesting very challenging. Previous research has indicated that wave energy was mainly generated and transferred by wind, but the detailed correlation between wind and wave energy has not been discovered. Wave energy in the Gulf of Mexico (GoM) has high variability with distinct seasonal behavior. However, the underlying reasons for this unique behavior have not been discussed and discovered yet. In this paper, a computer animation-based dynamic visualization method was created to conduct exploratory and explanatory analyses of 36 years of meteorological data in the GoM from the WaveWatch III system to identify preliminary patterns and underlying reasons for the unique behavior of wave energy in the GoM. These preliminary patterns and underlying reasons were further analyzed using Energy Events and Breaks concepts. During both high and low levels wave energy periods, the detailed correlation between wave energy and the wind was analyzed and determined. High level wave power in the GoM was mainly generated by the local inland wind from northern weather patterns, while low level wave power was mainly generated by swells from the Caribbean and the Atlantic oceans, which entered the GoM through the two narrow pathways, the Straits of Yucatan and the Florida Straits. The results from this paper will also be able to help the design, placement, and operation of future wave energy converters to improve their efficiency in harvesting wave energy in the GoM.
... Various studies have shown that wave energy has the potential to meet a significant proportion of UK electricity demand (e.g. Thorpe, 1992;Thorpe 1999;DTI, 2004). At present the wave energy industry is in its infancy, with a small number of devices at the commercial demonstration stage and many more at earlier stages of development. ...
The use of satellite altimeter data for spatial mapping of the wave resource is examined.
A new algorithm for estimating wave period from altimeter data is developed and
validated, which enables estimates of wave energy converter (WEC) power to be
derived. Maps of the long-term mean WEC power from altimeter data are of a higher
spatial resolution than is available from global wave model data. They can be used for
identifying promising wave energy locations along particular stretches of coastline,
before a detailed study using nearshore models is undertaken.
The accuracy of estimates of WEC power from wave model data is considered. Without
calibration estimates of the mean WEC power from model data can be biased of the
order of 10-20%. The calibration of wave model data is complicated by non-linear
dependence of model parameters on multiple factors, and seasonal and interannual
changes in biases. After calibration the accuracy in the estimate of the historic power
production at a site is of the order of 5%, but the changing biases make it difficult to
specify the accuracy more precisely.
The accuracy of predictions of the future energy yield from a WEC is limited by the
accuracy of the historic data and the variability in the resource. The variability in 5, 10
and 20 year mean power levels is studied for an area in the north of Scotland, and
shown to be greater than if annual power anomalies were uncorrelated noise. The
sensitivity of WEC power production to climate change is also examined, and it is
shown that the change in wave climate over the life time of a wave farm is likely to be
small in comparison to the natural level of variability. It is shown that despite the
uncertainty related to variability in the wave climate, improvements in the accuracy of
historic data will improve the accuracy of predictions of future WEC yield.
The topic of extreme wave analysis is also considered. A comparison of estimators for
the generalised Pareto distribution (GPD) is presented. It is recommended that the
Likelihood-Moment estimator should be used in preference to other estimators for the
GPD. The use of seasonal models for extremes is also considered. In contrast to
assertions made in previous studies, it is demonstrated that non-seasonal models have a
lower bias and variance than models which analyse the data in separate seasons.
... Amongst all the inexhaustible resources, ocean wave energy, known as wave energy, is abundant in terms of generating capacity. The global wave power energy resource has been estimated to be 2TW (or 17500 TWh/year) [2]- [4]. ...
... Among different types of renewable energy resources such as solar, wind, tidal, and geothermal, ocean wave energy is considered the cleanest, safest, most stable and most predictable renewable energy [70]. Furthermore, wave energy has the highest power density compared to solar and wind energy sources [90], up to 60 kW per meter of wavefront length with a very low impact on aquatic life [88]. However, while the wave energy industries have grown slowly, specialists believe that this technology is decades behind other types of renewables, with large investments of funding and research required for it to reach a commercially viable level [5]. ...
Wave energy technologies have the potential to play a significant role in the supply of renewable energy worldwide. One of the most promising designs for wave energy converters (WECs) are fully submerged buoys. In this paper, we explore the optimisation of WEC arrays consisting of three-tether buoys.
Such arrays can be optimised for total energy output by adjusting the relative positions of buoys in a wave farm. As there are complex hydrodynamic interactions among WECs, the evaluation of each parameter setting is computationally expensive and thus limits the feasible number of full model evaluations that can be made. Furthermore, these WEC interactions make up a non-convex, multi-modal (with multiple local-optima), continuous and constrained optimisation problem. This problem is challenging to solve using optimisation methods. To tackle the challenge of optimising the positions of WECs in a wave farm, we propose a novel multi-swarm cooperative co-evolution algorithm which consists of three meta-heuristics: the multi verse optimiser (MVO) algorithm, the equilibrium optimisation (EO) method, and the moth flame optimisation (MFO) approach with a backtracking strategy, we introduce a fast, effective new surrogate model to speed up the process of optimisation.
To assess the effectiveness of our proposed approach, 11 state-of-the-art bio-inspired algorithms and three recent hybrid heuristic ideas were compared in six real wave situations located on the coasts of Australia, with two wave farm sizes (four and nine WECs).
The experimental study presented in this paper shows that our hybrid cooperative framework exhibited the best performance in terms of the quality of obtained solutions, computational efficiency, and convergence speed compared with other 14 state-of-the-art meta-heuristics. Furthermore, we found that the power output of the best-found 9-buoy arrangements were higher than that of perpendicular layouts at at 4.15%, 3.29%, 3.62%, 9.2%, 5.74%, and 2.43% for the Perth, Adelaide, Sydney, Tasmania, Brisbane, and Darwin wave sites, respectively. Our investigations reveal that the best-found arrangement at the Tasmania wave site was able to absorb the highest level of wave power relative to the other locations.
... As the "native" energy in the ocean, wave energy is more desirable for powering the MIoT due to its extensive availability and high density (order of magnitude higher compared to solar or wind). 6 Currently, the most demonstrated commercial ocean wave energy converters are based on the traditional electromagnetic generators (EMGs). 7,8 Although the EMG wave energy converters operate efficiently in their design sea states, 9−12 they share the common disadvantage of low efficiency under low frequency conditions. ...
... The breakwater system has evolved significantly; one of the wave-absorbing mechanisms is the perforated and hollow breakwater. The hollow breakwater's varied model is supposed to minimize wave reflection and propagation in addition to reducing wave reflection, due to its capacity to capture and reduce incident wave energy (Wu & Hsiao, 2013;Thorpe, 1999;Brooke, 2003). ...
The wavelength, the wave height, and the depth of the water under which the waves travel are critical criteria for describing water waves. According to previous research, the depth and period of the waves have a significant effect on the propagation and reflection coefficients. The hollow breakwater's varied model is supposed to minimize wave reflection and propagation in addition to reducing wave reflection, due to its capacity to capture and reduce incident wave energy.
... Compared with other renewable energy sources, e.g., solar and wind energy, wave energy has the highest energy density (Falnes, 2007) and in addition to providing sustained and stable energy, it was pointed out that wave energy converters (WECs) can capture energy up to 90% of the time, while, only 20%~30% percent is available for wind and solar power devices (Pelc and Fujita, 2002;Drew et al., 2009;Guedes Soares et al., 2012). It was estimated that the potential wave energy resource around the world is about 2 TW (Thorpe, 1999), where, Europe is characterized by substantial wave energy, which is about 320 GW accounts 16% of worldwide wave energy resource (Rusu and Soares, 2009;Iglesias et al., 2009). For example, the total practical wave resource of UK in the offshore area is estimated as 70 TWh/year, and 5.7 TWh/year for nearshore regions, while the wave power can be practically and economically extracted is between 32 and 42 TWh/ year (Richard, 2012). ...
Model tests have been conducted to study the performance of slack, catenary and hybrid mooring systems for a point absorber in survival sea states. The snap loads can be found in mooring tension time series of all the tested mooring configurations. The classical Weibull distribution is applied to model the extreme dynamic mooring tensions. In addition to the Weibull distribution, the Bayesian inference method with a new Markov chain Monte Carlo sampling procedure is proposed to study the short term extreme mooring tensions based on model test results. Before applying this method to analyse extreme mooring tension, its accuracy is validated. The probability densities as well as short term extreme dynamic tension estimated by a mixture of Gamma and Generalised Pareto Distributions models are compared with the two-parameter Weibull model results. In the end, an extensive discussion of about the mixture of Gamma components, peak definitions, threshold and Markov chain Monte Carlo iteration on Bayesian inference is carried out. It is validated that the mixture model proposed in this paper shows good performance in predicting the extreme mooring tensions even when the snap loads occur, while the Weibull distribution fails to give accuracy predictions.
Uruguay has established itself as a successful example of energy transition in the electricity system, meeting 97% of its electricity demand with renewable sources during typical years. However, the decarbonization of the transport and industry sectors remains a major challenge. To address this, the country has developed an ambitious roadmap for green hydrogen production, taking advantage of its vast offshore wind potential, estimated at approximately 275 GW. In this context, the present study quantitatively assesses the feasibility of two hybrid energy platform configurations integrating offshore wind turbines and wave energy converters (WECs) along the Uruguayan Atlantic coast, using advanced simulation software to calculate the annual energy generated and the respective weighted capacity factor. Configuration 1, consisting of a star-shaped platform with a single turbine and three WECs, had a capacity factor of 44.07%, while configuration 2, consisting of a triangular platform with two turbines and three WECs, had a capacity factor of 35.89%.
Ocean wave energy is a widely available and largely unexploited renewable energy source. Generation equipment needs to operate reliably and withstand rough seas, so power shedding in high sea states is as important as maximum power extraction in low sea states for minimum levelized cost of energy. Wave resources fluctuate and are represented by statistical distributions, so both sizing of the powertrain components and power maximising control need to be optimized over multiple simulations. Computationally efficient models are required include the wave frequency dynamics with a period of a few seconds, over a run duration of an hour. This paper develops a new pseudo-steady-state model of the permanent magnet synchronous machine (PMSM) for system codesign and real-time platform control. For use under load-shedding control, the model needs to include field-weakening operation and winding temperature estimation and losses. Dynamic equations for the generator and current control are replaced by an analytical solution giving a factor of 15-40 times speed up in solution time.
With the continuous growth in energy demand, the search for renewable and
environmentally friendly sources becomes crucial for sustainable development. This
study aims to evaluate the feasibility of energy generation through oceanic dams,
applying the volumetric budget methodology to assess its effectiveness. The methodology is applied specifically to the Bacanga Dam, and the study compares the relationship between construction costs and installed capacity for various energy sources. At the conclusion of the study, it was possible to affirm that the methodology demonstrates a high level of accuracy in estimating macro-item costs. However, costs associated with the construction of tidal power plants remain high, with lower cost-to-capacity ratios compared to other renewable sources. Nevertheless, the reliability and environmental impact of construction distinguish tidal power plants from other sources in the Brazilian energy matrix.
This paper provides an overview of the recent advancements in magnetic structured triboelectric nanogenerators (MSTENGs) and their potential for energy harvesting and sensing in coastal bridge infrastructure. This paper begins with a brief discussion on the fundamental physics modes of triboelectric nanogenerators (TENGs), triboelectric series, and factors affecting TENG power generation and transmission, providing a foundation for the subsequent sections. The review focuses on the different types of MSTENGs and their applications in coastal infrastructure. Specifically, it covers magnetic spherical TENG networks, magnet-assisted TENGs, MSTENGs for bridges, and magnetic multilayer structures based on TENGs. The advantages and limitations of each type of MSTENG are discussed in detail, highlighting their respective suitability for different coastal bridge infrastructure applications. In addition, the paper addresses the challenges and provides insights into the future of MSTENGs. These include the need for improved durability and sustainability of MSTENGs in harsh coastal environments, increasing their power-output levels to fulfill high energy needs, and the requirement for collaborative efforts between academia, industry, and government institutions to optimize MSTENG performance.
Interactions between wave energy converters (WECs) can significantly affect the overall energy-harnessing performance of a wave park. Although large-size wave parks with many WEC units are commonly considered in practical applications, it is challenging to simulate such parks due to huge computational costs. This paper presents a numerical model that uses the boundary element method (BEM) to simulate wave parks. Each wave energy converter (WEC) was modelled as a comprehensive system, including WEC buoys, power take-off, and mooring systems, with hydrodynamic interactions included. Two classical layouts for arranging 16 units were simulated using this numerical model. The energy-harnessing performance of these array layouts was analyzed for both regular waves and a selection of irregular sea state conditions with different wave directions, wave heights, wave periods and water depths. For each layout, three WEC separation distances were studied. An increase of up to 16% in the power performance of the WEC under regular waves was observed, which highlights the importance of interaction effects.
Progress in better understanding and modeling Earth surface systems requires an ongoing integration of data and numerical models. Advances are currently hampered by technical barriers that inhibit finding, accessing, and executing modeling software with related datasets. We propose a design framework for Data Components, which are software packages that provide access to particular research datasets or types of data. Because they use a standard interface based on the Basic Model Interface (BMI), Data Components can function as plug-and-play components within modeling frameworks to facilitate seamless data–model integration. To illustrate the design and potential applications of Data Components and their advantages, we present several case studies in Earth surface processes analysis and modeling. The results demonstrate that the Data Component design provides a consistent and efficient way to access heterogeneous datasets from multiple sources and to seamlessly integrate them with various models. This design supports the creation of open data–model integration workflows that can be discovered, accessed, and reproduced through online data sharing platforms, which promotes data reuse and improves research transparency and reproducibility.
In our country, which is defined as rich in renewable energy resources, these are important; to be able to use the existing renewable energy sources in the most efficient way and minimize foreign dependency at the point of energy source. The topic of this case is to be able to select the most appropriate renewable energy source for Türkiye by using multi-criteria decision methods, to be able to determine the eligibility criteria to compare six sorts of renewable energy sources which are solar, wind, geothermal, hydroelectric, biomass, wave and by collecting the correct data related to these criteria, to create a study case by applying CRITIC, WASPAS methods on these data and immediately afterward to analyze the results of application to be able to provide an ease of evaluation for energy investments which will be in the future. At the end of our calculations, wave energy was determined as the energy source with the highest WASPAS score (0.413). Wind energy (0.327) and geothermal energy (0.313) ranked second and third, respectively. Hydro Energy (0.286), solar energy (0.286), and biomass energy (0.257) are energy sources with lower WASPAS scores. However, the ranking of results may vary according to other factors. If other sources are taken into account, the results may be different. Because Every country and every region has different energy needs and resources. Therefore, decision-makers should consider multiple criteria to select the most suitable renewable energy sources according to their conditions, considering these factors .
In our country, which is defined as rich in terms of renewable energy resources, these are important that; to be able to be used the existing renewable energy sources in the most efficient way as regional, minimize foreign dependency at the point of energy source. The topic of this case is to be able to select the most appropriate renewable energy source for Türkiye by using multi-criteria decision methods, to be able to determine the eligiblity criterias in an effort to compare for six sorts of renewable energy sources which are solar, wind, geothermal, hidroelectric, biomass, wave and by collecting the correct datas related to these criterias, to create a study case by applying CRITIC, WASPAS methods on these datas and immediately afterwards to analyze the results of application in order to be able to provide an ease of evaluation for energy investments which will be in the future. At the end of our calculations, wave energy was determined as the energy source with the highest WASPAS score (0.434). Wind energy (0.374) and geothermal energy (0.354) ranked as second and third, respectively. HydroEnergy (0.330), solar energy (0.328) and biomass energy (0.297) are energy sources with lower WASPAS scores. However, the ranking of results may vary according to other factors. If other sources are taken into account, the results may be different. Because Every country, every region has different energy needs and resources. Therefore, decision makers should consider multiple criteria to select the most suitable renewable energy sources according to their conditions, by taking these factors into account.
The use of wave energy by converting it into electricity depends on the efficiency of wave energy converters, which are negatively affected by marine factors. Many design flaws can be eliminated at the stage of design and testing of devices by using its numerical models based on the application of the hydrodynamic theory of propagation and interaction of waves with marine structures. The use of the modern computational methods of hydrodynamics to determine the influence of some design factors of wave energy converters incorporated into a submerged breakwater is considered in the paper. The results of numerical studies showed that if a submerged breakwater is located in the wave stream and with a transducer installed on its crest, there is a change in flow velocities and pressure in the transducer chamber, which affects the efficiency of energy extraction. Additional advantages arise as a result of the introduction of a complex structure with coastal protection and power supply functions. The obtained calculation results visualize the qualitative indicator of the influence of the design factors of the converter. Additional conclusions can be obtained by processing the numerical results. As a result of numerical experiments conducted with using REEF3D CFD computer system, the measures for selecting the parameters of the converters were proposed based on mathematical modeling of specific structures. The research related to the determination of the mechanisms of wave energy transformation when interacting with coastal protection elements focused on increasing the efficiency of the convertor by locating in deeper water, which includes detailed testing, investigations and improvement of various types of constructions, is carried out on the computing and laboratory base of Institute of Hydromechanics.
With a model-based control strategy, the effectiveness of the associated control action depends on the availability of a
representative
control-oriented model. In the case of floating offshore wave energy converters (WECs), the device response depends upon the interaction between mooring system, any mechanical parts, and the hydrodynamics of the floating body. This study proposes an approach to synthesise WEC controllers under the effect of mooring forces building a representative data-based linear model able to include any relevant dynamics. Moreover, the procedure is tested on the moored pendulum wave energy converter (PeWEC) by means of a high-fidelity mooring solver, OrcaFlex (OF). In particular, the control action is computed with and without knowledge of the mooring influence, in order to analyse and elucidate the effect of the station-keeping system on the harvested energy. The performance assessment of the device is achieved by evaluating device power on the resource scatter characterising Pantelleria, Italy. The results show the relevance of the mooring dynamics on the device response and final set of control parameters and, hence, a significant influence of the station-keeping system on control synthesis and extracted mechanical power.
3D printer is a cutting-edge process that manufactures a product directly from a CAD file using a layer-based manufacturing strategy. Fused deposition modeling (FDM) is a 3D printing process that uses a flexible extruder and a heated nozzle to create components. Various process parameters drastically impact the mechanical properties and component weight of printed objects. As a result, improving the mechanical features of printed components requires examining the impacts of input elements and anticipating results by using relevant process settings. The impact of process factors such layer height, print speed, shell count, and fill density on the compressive strength and part weight of products printed from polylactic acid (PLA) via FDM were investigated in this work. The studies employed an L16 Taguchi orthogonal array experimental design to alter the input parameters at various levels. The investigation indicated that shell count and infill density are the most significant factors influencing the compressive strength of PLA components. Printing speed has a negligible impact on printed component part weight, while layer height, shell count, and infill density have a substantial impact.KeywordsFused deposition modelingCompressive strengthPart weightPolylactic acid
Wave energy has been studied by many scholars throughout history as an alternative renewable energy source, with traditional wave energy conversion devices utilizing hydraulic systems and electromagnetic power generation technology being used to a great extent. The emerging triboelectric nanogenerators (TENG) offers a novel technology for harvesting electrical energy from wave energy. In this study, a prototype TENG based on the Archimedes Wave Swing (AWS-TENG) is proposed. By investigating structural properties and wave energy theory, the physical model of AWS-TENG was developed. Furthermore, in order to better understand its electrical dynamic characteristics, a V-Q-X equation analysis of the TENG in vertical separation mode was carried out in finite element software. In addition, the experimental tests were carried out on the system. The experimental results show that AWS-TENG achieves a power density output of 7.2 mW/m2 at 4.5 Hz, which is sufficient for fast capacitor charging and application circuits. This novel TENG design offers a unique way to capture wave energy.KeywordsAWSTriboelectric nanogeneratorWave energyElectric field forceHydrodynamic performanceWave energy converters
The energy crisis experienced in the 1970s showed that meeting the energy requirements mostly from fossil fuels could adversely affect our lives. While the energy requirements are mostly met from fossil fuels, their harmful effects on the environment are also becoming more evident by each day. As a result, different energy sources were started to be researched to diversify the supply of energy and to prevent the pollution of the environment. Waves are a promising and abundant source of renewable energy that was started to be studied during the days of the energy crisis. Many different types of wave energy converters have been designed so far, which are at different levels of development. Designing a wave energy converter that will satisfy many requirements in a very harsh environment is a complex process. Many factors should be analyzed, such as the geometry and the size of the float, the type of the power take-off system and its dynamics, the mooring system, and the environmental conditions. Thus, the wave energy converters are briefly introduced and the analyses that are carried out during the design process are explained.KeywordsWave energyLevelized cost of energyRenewable energy
The exploitation of clean and renewable wave energy has attracted fully concern in the world wide. In this work, a high-output array of liquid-solid tubular triboelectric nanogenerator (LST-TENG) based on the contact electrification between PTFE and water was proposed. The low-frequency wave motion was simulated to systematically analyze the impacts of several factors on the electrical performance of LST-TENG to provide guidance for the fabrication of the PTFE tube and the electrode arrangement for the achievement of high wave energy transition. An increase in the length/diameter of the tube, distance and width of the electrodes made a positive impact on the output performance of LST-TENG unit. A typical LST-TENG here should be an optimum water-to-cylinder volume ratio, as well it is better to wrap electrodes from the end, especially for short electrodes. Moreover, the influences of the motion characteristics including the angle, frequency and amplitude of oscillation was also considered. To achieve high peak output, we compared the output performance of series-wound and parallel LST-TENG arrays to find that parallel connection showed linear rise with the number of units is a feasible approach to get peak output voltage exceed 500 V, which extended the potential application of the LST-TENG arrays. At the optimal operating condition, the power density achieved 228 mW/m³. This study provided the assessment of the power quality of LST-TENG and considering the diverse motion of the TENG units integrated into the blocks, which is expected to be the reference for the optimization of LST-TENG in the future.
An unstructured, low-Mach, balanced-force, volume of fluid methodology is coupled to an implicit, six-DOF overset formulation for the simulation of wave-based renewable energy devices. We propose an overlapping unstructured mesh construct that affords a wave energy converter (WEC) geometry to move freely about a background domain. A control volume finite element (CVFEM) numerical discretization, which includes novel residual-based stabilization, is developed. Credibility of this simulation tool is established by code verification, which demonstrate design-order numerics on linear and quadratic conformal and overset meshes, and model validation. A CVFEM balanced-force method is applied to a static bubble configuration using conformal and mixed topology overset meshes, while an obstructed dam break case is used to establish the viability of the proposed numerical construct. A validation hierarchy that focuses on falling and rising spheres in quiescent flow showcases the stability of the overset and six-DOF coupling approach. Finally, a buoy validation case is presented that demonstrates the efficacy of the parallel, implicit overset approach for this challenging multiphase flow regime by including both low- and high-displacement configurations along with a large wave displacement numerical benchmark with and without mooring.
A detailed review of the works carried out in connection with wave energy extraction devices are presented in this chapter. Although, there are a few methods of extracting the energy from waves, the emphasis is laid on Oscillating water column (OWC) devices due to its’ more attractive, simple, and proven technology. The classification of the OWC devices based on location, its principle and the different options for its installation is made. If one works out the cost-benefit ratio, it is rather not encouraging to plan for a device to extract energy. Hence, the possibilities of merging OWC with breakwaters would be more viable and cost-effective too. Here again, one should consider the purpose of the breakwater as it may be either for development harbor or coastal protection. With this background, the different options of multi-purposed wave energy devices and, in specific, the conceptual design of integrating the breakwater and OWC are presented in this chapter.
3.1 MODELLING OF WAVE ENERGY CONVERTER DYNAMICS Currently, several WECs exist with different absorption mechanisms and subsystems. Hence, a general formulation to describe the dynamics of all possible devices is a non- trivial task. This section provides practical, condensed information, and derivations for the dynamics of oscillating bodies, as this category comprises most WECs, and relevant literature is recommended for more technical information. The approaches described here can be extended to the analysis of other WECs systems and examples of these are given throughout the book.
3.2 PRINCIPLES AND BOUNDS OF WAVE POWER ABSORPTION Understanding the principles and limits in WEC power absorption is crucial for efficient PTO system design. To avoid losing generality, this section treats the PTO system (a complex and multi-functional sub-system of WEC as detailed in Section 3.3) as a generic feedback control system that generates a PTO control force modifying the power absorption performance of the WEC system.
3.3 CONTROL SYSTEM AND POWER TAKE-OFF DESIGN
The PTO system is the core of a WEC, and has multiple functions: 1) most obviously, it converts the mechanical power of the WEC mechanism into electricity; 2) it enhances the hydrodynamic efficiency of the WEC and thus maximises its power absorption in varying sea states; and 3) it ensures safe operation of the WEC in the harsh sea environment.
The subject of this thesis is a theoretical investigation, supported by experiments and computer simulations, of two concepts for small but highly productive off-shore wave energy converters (WECs), namely FROG and PS FROG. These were conceived with the aim of reducing the high structural costs associated with previous proposals. PS FROG was invented in the course of this project, to circumvent engineering problems inherent in FROG. Whilst at first sight the two devices appear very different, it is shown that their respective equations of motion may be reduced to a similar form. Both devices float freely, lightly restrained by compliant moorings and work by maintaining a vigorous, quasi-resonant oscillation, strongly coupled with the wave-force, which is reacted against the inertia of an accelerating internal mass.FROG is a heaving, vertically axi-symmetric buoy of diameter 15 - 20m, thus it is an omni-directional (source-like) point absorber. PS FROG is a pitching and surging vertical flap, of roughly 20m width, aligned to face the incident waves. It is therefore, a directional(dipole-like) point absorber, which gives it twice the ideal power capture width of FROG.
Hydrodynamic coefficients are obtained for both devices and their equations of motion solved, so that estimates of mean annual power capture can be produced, for the standard South Uist wave climate. In addition, experimental power generation tests on 1/60th scale FROG models, are shown to give excellent agreement with theoretical predictions. Problems with the practical implementation of FROG are discussed and the resulting evolution of the PS FROG concept described.PS FROG is finally demonstrated to be clearly superior to FROG and its estimated cost of electricity produced, of under 4p per unit (at 1988 prices, assuming a 5% discount rate and 20 year life) appears highly competitive for an off-shore WEC .
The SEA-Lanchester wave energy research group has been working on the development of the SEA-Clam wave energy converter since 1978 as part of the United Kingdom research programme. This floating device, designed to extract the energy from sea waves and convert it to electricity, has been shown to be an operationally viable device at a 10 MW rating as part of a 2 GW station. In a recent assessment the SEA-Clam was deemed to be the leading device with a potential for further development and early exploitation. This paper describes the concept of the device, its design development and the extensive model performance testing at 1/50th and 1/11th scale in indoor tanks and the natural environment of Scotland's Loch Ness. The paper also illustrates the cost viability of small devices to supplement or replace diesel generated electricity for island or coastal communities and outlines the present development programme to design construct and test a 650 kW rated prototype within the next three and a half years, thus providing a shop window for the world wide development of wave energy. (A)
Based on a re-evaluation of available experimental data on breaking waves, a relationship between the breaker height - breaking depth ratio, the incident wave steepness and the beach slope is found. This relationship, when combined with experimental observations of breaker travel, permits an estimate of the maximum breaking wave height a coastal structure might experience given a design wave period and design depth at the structure site. Revised criteria for breaker classification are presented.
A method of determining the hydrodynamic coefficients of a floating wave-energy absorber is outlined, and the coefficients of a Salter's duck are measured experimentally. A complex-conjugate synthesizer, derived from these coefficients, is used both theoretically and experimentally to predict and to measure the efficiency of a duck in unidirectional monochromatic waves. The synthesis produces a higher efficiency over a greater bandwidth than has been achieved before. The reason for the improvement in efficiency is explained, and conclusions are drawn about the implications of complex-conjugate control for predicting practical engineering constraints on the design of a full-sized wave-energy absorber.
The report represents the first attempt that has been made to quantify Ireland's wave power resource. While it has long been recognized that wave power levels off the west coast of this country are among the highest in the world, very limited measurements have so far been made and the state of knowledge of the wave climate is poor. The results of the work undertaken by Dr. Mollison show that the resource is large compared with present needs in Ireland. This indicates that wave power could make a greater relative contribution to the Irish energy system than would be the case for other countries. (Copyright (c) by National Board for Science and Technology, 1982.)
The data for the spectra of fully developed seas obtained for wind speeds from 20 to 40 knots as measured by anemometers on two weather ships are used to test the similarity hypothesis and the idea that, when plotted in a certain dimensionless way, the power spectra for all fully developed seas should be of the same shape as proposed by Kitaigorodskii (1961). Over the important range of frequencies that define the total variance of the spectrum within a few percent, the transformed plots yield a non-dimensional spectral form that is nearly the same over this entire range of wind speeds within the present accuracies of the data. However, since slight variations of the wind speed have large effects on the location of this non-dimensional spectral form, inaccuracies in the determination of the wind speed at sea allow for some latitude in the final choice of the form of the spectrum. Also since the winds used to obtain the non-dimensional form were measured at a height greater than ten meters, the problem of relating the spectral form to a standard anemometer height arises. The variability introduced by this factor needs to be considered. The results, when errors in the wind speed, the sampling variability of the data, and the anemometer heights are considered, suggest a spectral form that is a compromise between the various proposed spectra and that has features similar to many of them.
The energy crises of the 'seventies threatened the standard of living of the developed countries and led to vigorous research into a variety of possible replacements for fossil fuel—particularly for oil. Sea waves were one of the more novel of the renewable resources which were taken seriously.
Recent work on wave power devices has encouraged interest in the processes whereby waves lose energy and change direction in shoaling water, and especially in detailed calculations of their effects.1,2 Here one of the most comprehensive sets of measurements available is examined, for four sites in depths of 15 to 100 m off South Uist in the Hebrides. The mean directional spectrum is recalculated for each site, and a proper allowance found for refraction which raises the estimates of net energy flux in intermediate depths by up to 10%. Indeed, the pattern of losses between 100 m and 23 m depths fits well with that expected from bottom friction. The estimated friction coefficient is quite high, as might be expected in view of the very rough sea bottom in the area.3
Wave Energy: the Department of Energy's R&D Programme 1974-1983 ETSU Report Number R-26Strategic Review of the Renewable Energy TechnologiesBackground Papers Relevant to the
1.
"Wave Energy: the Department of Energy's R&D Programme 1974-1983", P. G. Davies
(ed), ETSU Report Number R-26, March 1985.
2.
"Strategic Review of the Renewable Energy Technologies", ETSU Report Number
R-13, November 1982.
3.
"Background Papers Relevant to the 1986 Appraisal of UK Energy Research, Development
and Demonstration", ETSU Report Number R-43, February 1987.
Heaving Point Absorbers Reacting Against an Internal Mass
- M J French
- R H Bracewell
French, M. J. and Bracewell, R. H., "Heaving Point Absorbers Reacting Against an Internal
Mass", IUTAM Symposium on Hydrodynamics of Ocean Energy Utilization, Lisbon, 811 July 1985.
Latest Developments in Wave Energy at Lancaster
- M J French
French, M. J., "Latest Developments in Wave Energy at Lancaster", I. Mech. E. Seminar on
Wave Energy, 28 November 1991.
The Economic Viability of the Circular Clam for Offshore Wave Energy Utilisation
- A M Peatfield
Peatfield, A. M., "The Economic Viability of the Circular Clam for Offshore Wave Energy
Utilisation", I. Mech. E. Seminar on Wave Energy, 28 November 1991.
Small Scale Low Cost Wave Power Devices-Phase 1
- T J Whittaker
Whittaker, T. J. et al, "Small Scale Low Cost Wave Power Devices-Phase 1", ETSU
Report Number WV 1675-P1, 1987.
Islay Shoreline Wave Energy Device-Phase 2
- T J Whittaker
Whittaker, T. J. et al, "Islay Shoreline Wave Energy Device-Phase 2", ETSU Report
Number WV 1680, 1991.
Islay Shoreline Wave Energy Device-Phase 3 The Queen's University of Belfast, "The UK's Shoreline and Nearshore Wave Energy Resource
- T J Whittaker
Whittaker, T. J. et al, "Islay Shoreline Wave Energy Device-Phase 3", ETSU Report WV
1682, 1992.
12.
The Queen's University of Belfast, "The UK's Shoreline and Nearshore Wave Energy
Resource", ETSU Report WV 1683, 1992.
The Hydrodynamics of Solo Ducks
- D Skyner
Skyner, D., "The Hydrodynamics of Solo Ducks", the Solar Energy Society Conference on
Wave Energy Devices, Coventry, 30 November 1989.
- T W Thorpe
- J E M Marrow
Thorpe, T. W. and Marrow, J. E. M., "The Wave Energy Review-Progress Report
Number 1", December 1989.
The Wave Energy Review-Progress Report Number
- T W Thorpe
- J E M Marrow
Thorpe, T. W. and Marrow, J. E. M., "The Wave Energy Review-Progress Report
Number 2", June 1990.
- T W Thorpe
Thorpe, T. W., "Wave Energy Review-Interim Report", ETSU Report Number
R-60, October 1990.
Wave Prediction in Deep Water and at the Coastline
- H N Southgate
Southgate, H. N., "Wave Prediction in Deep Water and at the Coastline", Report Number
SR 114, Hydraulics Research Wallingford, Oxfordshire, UK, August 1987.
Ray Methods for Combined Refraction and Diffraction Problems
- H N Southgate
Southgate, H. N., "Ray Methods for Combined Refraction and Diffraction Problems",
Report Number IT 214, Hydraulics Research, Wallingford, Oxon. UK, 1981.
Average Annual Wave Power at South Uist
- J Crabb
Crabb, J., "Average Annual Wave Power at South Uist", Report to Wave Energy Steering
Committee, WESC(82) DA150 and DA150A, 1982.
Consultant's 1983 Report-Volumes 2A and 2B, Supporting Information and Methodology
- Palmer Rendel
Rendel, Palmer and Tritton, "Consultant's 1983 Report-Volumes 2A and 2B, Supporting
Information and Methodology", ETSU Report Number WV 1570, Parts 17 and 18, June
1983.
Selected Wave Records and One-Dimensional Spectra for South Uist
- J Crabb
Crabb, J., "Selected Wave Records and One-Dimensional Spectra for South Uist", Inst.
Ocean. Studies, ETSU Report Number ETSU WV 1516 Part 1, January 1978.
Some Calculations from the Met
- A J B Winter
Winter A. J. B., "Some Calculations from the Met. Office Model", Report to Wave Energy
Steering Committee, WESC(79) DA84, July 1979.
The European Wave Power Resource
- D Mollison
Mollison, D., "The European Wave Power Resource", Proc. Conf. on Wave Energy
Devices, Coventry, UK, 30 November 1989.
Assessing the Shoreline Wave Power ResourceModification of Wave Height Due to Bottom Friction, Percolation and Refraction
- D C L Mollison
- R O Reid
Mollison, D., "Assessing the Shoreline Wave Power Resource", Proc. Euromechanics
Colloquium 243 on Energy from the Waves, Univ. of Bristol, UK, 26-28 September 1988.
33.
Bretschneider, C. L. and Reid, R. O., "Modification of Wave Height Due to Bottom
Friction, Percolation and Refraction", Tech. Memo. Number 45, US Army Corps. of
Engineers, October 1954.