Wave Farm Research Articles

Predicting coastal impacts by wave farms: A comparison of wave-averaged and wave-resolving models

Wave energy converters (WECs) will have to be arranged into arrays of many devices to extract commercially viable amounts of energy. To understand the potential coastal impacts of WEC arrays, most research to date has relied on wave-averaged models given their computational efficiency. However, it is unknown how accurate wave-averaged model predictions are given a lack of validation data and their inherent simplifications of various hydrodynamic processes (e.g., diffraction). This paper compares the predictions of coastal wave farm impacts from a coupled wave-averaged and flow model (Delft3D-SNL-SWAN), to a wave-resolving wave-flow model (SWASH) that intrinsically accounts for more of the relevant physics. Model predictions were compared using an idealized coastal bathymetry over a range of wave conditions and wave farm geometries. Both models predicted the largest impacts (changes to the nearshore hydrodynamics) for large and dense wave farms located close to the shore (1 km) and the smallest impacts for the small and widely spaced farm at a greater offshore distance (3 km). However, the wave-resolving model generally predicted somewhat larger impacts (i.e., changes to the nearshore wave heights, mean velocities and mean water levels). We also found that coupling the wave-averaged model to a flow model resulted in more realistic downstream predictions than the stand-alone wave-averaged model.

Effect of resonance and wave reflection in semi-enclosed moonpool on performance enhancement of point absorber arrays

This paper presents a novel means to enhance the energy generation of the wave energy converters (WECs) array by deploying it in a semi-enclosed moonpool. The resonance phenomenon in a moonpool and the wave reflection from the wall of the moonpool result in an amplification of wave amplitude thus increase the energy generation of the wave farm. The wave diffraction and radiation analyses, based on the boundary element method are used to assess the performance of the array. An array of five-point absorbers in a semi-enclosed moonpool is considered and the energy generation, interaction effect and wave climate surrounding the wave farm are investigated. The results show that the width of the moonpool opening affects the performance of the WEC array. The wave climate surrounding the moonpool platform is studied to assess the effectiveness of the moonpool platform as a floating breakwater. The results show that the proposed integrated wave farm and floating breakwater system (moonpool platform) could generate a substantial amount of wave energy and at the same time is effective in attenuating the wave forces. The characteristics of the WECs reveal that the energy generation bandwidth could be increased by deploying the WECs in the semi-enclosed moonpool.

Experimental and theoretical analysis of detonation products state on bubble dynamics and energy distribution in underwater explosion

The initial states and pressure of detonation products in a bubble have a great impact on bubble pulsation in underwater explosions; particularly, the initial accelerated expansion of a bubble can determine the energy distribution. The energy output and distribution of explosives were obtained on the basis of the underwater explosion experiment in this paper. To study the process of bubble pulsation and energy output, we proposed a gas equation of state (EOS) combining the pvk form, Jones–Wilkins–Lee (JWL) EOS, and the initial states of a bubble to take the effects of the initial bubble pressure and detonation products state transformation into account; furthermore, the bubble radius, velocity, and acceleration vs time were obtained through the Rayleigh–Plesset equation under our experimental condition. The differences of bubble behaviors were compared by adopting the JWL EOS and a polytropic EOS with k = 3. The results showed that the initial bubble pressure and detonation products state transformation influence the accelerating expansion and the subsequent bubble oscillation, respectively. Subsequently, comparisons of the energy output and distribution for different gas EOSs showed that the initial shock wave energy for the JWL EOS was underestimated in accelerating expansion, and the bubble energy was overestimated using the polytropic EOS for k = 3; the obtained energy output and distribution had a better agreement with experimental data when adopting the improved gas EOS. In addition, the energy distribution was determined before the detonation products turned to the explosion gas state in initial expansion based on the relationship of the accelerating expansion characteristics and the initial shock wave energy generation. The research has a great significance to reveal the mechanism of bubble pulsation in underwater explosions.

Layout optimisation of offshore wave energy converters using a novel multi-swarm cooperative algorithm with backtracking strategy: A case study from coasts of Australia

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 techniques 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.

Design and research on the simulation platform of Oscillating Flapping-Wing Wave Energy Converter based on AMESim

It is a stochastic dynamic process for conversion of wave energy, which includes the coupling of multiphysics. Energy conversion efficiency and stable output are important objectives. In order to explore the mechanism of wave energy efficient conversion, a wave energy generation scheme of oscillating-flapping wing was proposed. Taking the conversion system of wave power generation device as the research object, the mechanical-hydraulic-circuit simulation platform of the system is established by the software AMESim. The proposed scheme is tested and verified. The results show that the wave energy conversion system can effectively convert wave energy, realize the stable output of electric energy and store it in the battery pack, which provides a theoretical basis for the development of wave energy generation converter of oscillating-flapping wing.

Analysis of linkage type sea wave power plant design through motion study and 3D printed modelling

Sustainable energy generation is becoming increasingly important because of the expected limitations in current energy resources and for reducing pollution. Wave energy generation has seen significant developments in recent years. This research has produced a linkage-type PLTGL design that utilizes ocean waves to raise and lower the float lever and move the linkage mechanism which then causes a back and forth movement of the rack gear which will rotate the pinion and cause the dynamo drive shaft to rotate. Using ocean wave data in the waters of Tanjung Berikat, Bangka Tengah, and with the help of the SolidWorks application, this design is then simulated to determine the resulting movement and rotation. The rotation generated through the simulation can reach 532 Rpm with the assumption that it does not involve friction forces and material loads that exist in the PLTGL design. This design was made in 3D using the CR-10 V3 type 3D printing machine which produced a model with a scale of 25% of the original design. The model is used as a discussion material for designers to improve the design.

Analysis of ocean wave power plant buoy system at Kelong

The potential of sea waves, located precisely in the Berakit area, can be used as electrical energy on a small scale. Kelong is a floating house situated on the coast, which anglers (fishermen) use to catch fish. In the Bintan area, there are two types of kelong, namely floating kelong and cacak (permanent) kelong. Floating kelong, as the name implies, is a kelong that can be moved anywhere. During the fish season, the kelong are offered to the middle of the sea, but if the west wind season or not during the fish season, the kelong will be brought ashore. On the other hand, kelong cacak are usually not far from the beach or coast and cannot be moved and operated at night by using a lamp to catch cuttlefish or anchovies. This research was conducted on Kelong Cacak and Floating Kelong (pontoon) located in Berakit, Disability Telok Sebong, Kabubapen Bintan. The power generation system was built using the buoy method. Based on the research results, the wave power plant can be driven by sea waves with an average height of 6 cm and produces a voltage and continuously the voltage is not always stable. The maximum peak output voltage is up to 15 Volt DC; after knowing the test results, the power plant can supply as a charger for the battery in the kelong cacak of 0.8839 Volt DC with an average battery voltage of 10.052 Volt DC and total voltage charging is 0.37 Volt DC, with average battery voltage 11.4902 Volt DC on Floating Kelong (Pontoon).

Research on the dynamic characteristics of the acquisition mechanism of the oscillating flapping wing wave energy power generation device based on the bond graph

Taking the acquisition mechanism of the oscillating flapping-wing wave energy power generation device as the research object, the design of the acquisition mechanism, the bond graph model of the acquisition mechanism and the dynamic characteristics are studied. According to the working principle of the acquisition mechanism of the oscillating flapping wing wave energy power generation device, the bond graph model and the state space equation of the acquisition mechanism are established. Based on the bond graph theory, the AMESim software is used for simulation analysis to verify the correctness of the bond graph model of the acquisition mechanism. The research results show that the designed oscillating flapping wing wave energy generation device acquisition mechanism responds quickly and stably, and the bond graph model basically matches the real system. The research process provides an effective reference for the development of the acquisition mechanism of the oscillating flapping wing wave energy power generation device.

PEMILIHAN TIPE PEMBANGKIT LISTRIK TENAGA GELOMBANG LAUT TIPE PELAMPUNG DI PANTAI SALUBOMBA KABUPATEN DONGGALA

Indonesia is a country that has an area of sea three times larger than the land area. In line with the rapid development, the need for electricity is also increasing. So that Indonesia has great potential to produce alternative and environmentally friendly energy, namely Sea Wave Energy. Its continuous nature is available all the time. Many potential coastal areas in Indonesia, however, have not been utilized optimally.
 The purpose of this study is to see the potential of Wave Energy for electricity. For this reason, research was carried out at a location in the Central Sulawesi area, precisely in Salubomba, Central Banawa District, Donggala Regency. In this study a potential study was conducted on 3 types of PLTGL, namely Buoy, OWC, and Pasut Dam, where one will be chosen that meets the wave criteria requirements on the Beach. From the results of research, PLTGL that fulfills the requirements is the type of buoy.
 Data collection begins with secondary data, namely wind data from Mutiara Station. Then proceed with calculating wave forecasting using the SMB (Sverdrup Munk-Bretschneider) method. The results of this study, Salubomba beach has the potential to be built by the Buoy Type Wave Power Plant, a significant wave height of 0.52 - 3.37 meters with a ruptured depth of 3.95 meters.

Multiobjective Economic Optimal Dispatch for the Island Isolated Microgrid under Uncertainty Based on Interval Optimization

In order to analyse the impact of renewable generation and load uncertainties on the economic operation optimization of the island microgrid, a multiobjective economic optimal dispatch model under uncertainty based on interval optimization is proposed in this paper. The mathematical model of distributed generation and the prediction model of wind speed and wave generation are established. The uncertainties of renewable generation and load are described by the interval mathematical method. On this basis, the interval multiobjective optimal dispatch model is presented. For the “battery disgusting” users on the island, the battery cost is regarded as a separate optimization objective, and a multiobjective optimization objective function to minimize the economic cost, battery cost, and pollution emission of the island microgrid is discussed. An island microgrid, composed of wind turbine, photovoltaic, wave energy generation, diesel generator, and energy storage system, is chosen as a case study. The NSGA-II algorithm is applied to solve the multiobjective optimal problem. The results for deterministic forecast data and load are analysed, and the optimal operation scheme is obtained by the improved multiobjective grey target decision-making method. The influence of renewable generation fluctuations ±10%, ±20%, and ±30% and the load fluctuations ±10% and ±20% on island microgrid operation optimization is discussed in detail, respectively. The relevant research results can provide a reference for formulating the operating scheme of the island microgrid.

Mooring Stability Study for Novel Wave Energy Converter Based on Regular Wave

The mooring system not only plays a vital role in keeping wave energy generators floating stably, but also affects the success of engineering design. Combining wave force theory and the hydrological data obtained from the field measurements of a certain sea area in the Bohai Sea, the Stokes second-order wave theory was adopted to design the mooring system of a new type of power-generating device. At the same time, the study uses the Aqwa software to gather the dynamic data of a power-generating device in a real test, and then makes models and carries out regular wave tests so as to verify the viability of the mooring system and the stability of the whole power-generating device. All of this work will provide a theoretical basis for the manufacture of an engineering prototype and its reliable supply of power.

A Combined Method of Improved Grey BP Neural Network and MEEMD-ARIMA for Day-Ahead Wave Energy Forecast

Since wave fluctuates continuously, the forecast of the wave energy is very important for the operation of power systems integrated with large-scale wave energy generation. A combined model of day-ahead wave energy forecast based on improved grey BP neural network (BPNN) and modified ensemble empirical mode decomposition (MEEMD) -autoregressive integrated moving average (ARIMA) is proposed in this paper. Firstly, the wave is decomposed into wind waves and swells by wave theories. Secondly, the correlation between wind wave and wind speed is analyzed with improved grey BPNN, and the average height of wind waves can be forecasted based on the historical wind speed data. Thirdly, the MEEMD-ARIMA model is utilized to forecast the average wave height of swells. Thus, combining the wind wave and the swell, the average wave height of the integrated wave can be obtained. Finally, a conversion model from wave elements to wave energy for Archimedes wave swing (AWS) is introduced. A case study using the measured wind and wave data from a real ocean is illustrated, and the effectiveness of the proposed wave energy forecast model is validated.

Air pressure forecasting for the Mutriku oscillating‐water‐column wave power plant: Review and case study

The high variability and unpredictability of renewable energy resources require optimization of the energy extraction, by operating at the best efficiency point, which can be achieved through optimal control strategies. In particular, wave forecasting models can be valuable for control strategies in wave energy converter devices. This work intends to exploit the short-term wave forecasting potential on an oscillating water column equipped with the innovative biradial turbine. A Least Squares Support Vector Machine (LS-SVM) algorithm was developed to predict the air chamber pressure and compare it to the real signal. Regressive linear algorithms were executed for reference. The experimental data was obtained at the Mutriku wave power plant in the Basque Country, Spain. Results have shown LS-SVM prediction errors varying from 9% to 25%, for horizons ranging from 1 to 3 s in the future. There is no need for extensive training data sets for which computational effort is higher. However, best results were obtained for models with a relatively small number of LS-SVM features. Regressive models have shown slightly better performance (8–22%) at a significantly lower computational cost. Ultimately, these research findings may play an essential role in model predictive control strategies for the wave power plant.

Energy‐maximising moment‐based constrained optimal control of ocean wave energy farms

Successful commercialisation of wave energy technology inherently incorporates the concept of an array of wave energy converters (WECs). These devices, which constantly interact via hydrodynamic effects, require optimised control that can guarantee maximum energy extraction from incoming ocean waves while ensuring, at the same time, that any physical limitations associated with device and actuator systems are being consistently respected. This paper presents a moment-based energy-maximising optimal control framework for WECs arrays subject to state and input constraints. The authors develop a framework under which the objective function (and system variables) can be mapped to a finite-dimensional tractable quadratic program (QP), which can be efficiently solved using state-of-the-art solvers. Moreover, the authors show that this QP is always concave, i.e. existence and uniqueness of a globally optimal solution is guaranteed under this moment-based framework. The performance of the proposed strategy is demonstrated through a case study, where (state and input constrained) energy-maximisation for a WEC farm composed of CorPower-like WEC devices is considered.

A use case of exclusive economic zone of Pakistan for wave power potential estimation

The demand for energy is constantly rising in developing countries. Ocean waves with continuous energy flux can contribute to universal energy production. The wave energy has its advantages of renewable, non-polluting and large storage, however, the technological solution to extract energy from oceans is still at early stages. In this paper, a strategy is devised to estimate wave power potential for a developing country. Pakistan is considered as a use case on the basis of less renewable energy share and facing energy crises. In this study, wave energy potential is estimated for power generation by excluding the sensitive areas from the exclusive economic zone. The year long significant wave height and mean wave period data set is used for the purpose. A GIS based multi-criteria overlay analysis model is implemented using different restriction and weighted factors such as ocean bathymetry, distance to ports and shoreline. The results show that average wave power is peaked at 9.15 kW/m in the summer season and 85% of Pakistan economic zone is suitable for wave farm development. The wave energy potential assessment is coupled by extractable power estimation that is worked out by assessing the performance of commercial wave energy converters in regional context.

A new framework and tool for ecological risk assessment of wave energy converters projects

Marine renewable energy has considerable potential for enhancing the diversity of renewable sources, to reduce our reliance on fossil fuels and combat climate change. While the technological development of wave energy converters is progressing rapidly, their environmental impacts are still largely unknown, which is a barrier that could hinder their deployment. This research contributes to the state-of-the-art by introducing a framework for quantifying and analysing the ecological risks of three technologies (oscillating water columns, oscillating wave surge converters, and wave turbines). Based on a literature review, expert consultation process, and the development of a web tool, the potential pressures and the ecosystem elements that might be affected during the life cycle of a generic wave farm (an array of wave energy converters) are investigated. The main pressures are found to be physical disturbance, physical loss, hydrological change, and noise. The ecosystem elements sustaining the largest number of pressures and, therefore, at higher ecological risk are fish and cephalopods species, and benthic and pelagic habitats. The ecological risk assessment framework is operationalized into a free-access web tool (https://aztidata.es/wec-era/) for the interactive assessment and visualisation of the pressures and ecological risks. The tool is intended to be used by managers, decision makers, scientists or promoters during the Strategic Environmental Assessment and Environmental Impact Assessment of wave energy projects. The novel approach presented in this work is more sophisticated than previous risk assessment matrices, enabling to better capture the complexity of the interactions between a wave farm and the environment.

Flume Experiments on Energy Conversion Behavior for Oscillating Buoy Devices Interacting with Different Wave Types

Oscillating buoy device, also known as point absorber, is an important wave energy converter (WEC) for wave energy development and utilization. The previous work primarily focused on the optimization of mechanical design, buoy’s array configuration and the site selection with larger wave energy density in order to improve the wave energy generation performance. In this work, enlightened by the potential availability of Bragg reflection induced by multiple submerged breakwaters in nearshore areas, we investigate the energy conversion behavior of oscillating buoy devices under different wave types (traveling waves, partial and fully standing waves) by flume experiments. The localized partial standing wave field is generated by the Bragg resonance at the incident side of rippled bottoms. Furthermore, the fully standing wave field is generated by the wave reflection of vertical baffle installed in flume. Then the wave power generation performance is discussed under the conditions with the same wave height but different wave types. The experimental measurements show that the energy conversion performance of the oscillating buoy WEC could be improved under the condition of standing waves when compared with traveling waves. This work provides the experimental comparison evidence of wave energy conversion response of oscillating buoy devices between travelling waves and standing (fully or partial) wave conditions.

Compact floating wave energy converter arrays: Inter-device mooring connectivity and performance

Achieving cost reduction in wave energy conversion is seen as essential to enabling the progress of the sector. At utility scale in a wave farm, multiple devices are likely to be deployed in array configurations. Closely spaced, compact wave energy converter (WEC) arrays are a promising option for cost reduction, realising synergies in operation and maintenance tasks and auxiliary installations, whilst achieving economies of scale. Mooring and anchorage systems are known to be a major component of the structural costs, and the use of interconnecting lines between neighbouring devices can reduce the number of anchors and minimise total line length. In this paper, we present the experimental study of different configurations of a five-device array of spar-buoy oscillating-water-column wave energy converters in a wave basin, focusing on the analysis of the power production performance. The study compares the performance of a single isolated device, an array with independently-moored devices and three arrays with inter-body connections, with different levels of connectivity in the mooring arrangement. Results show considerable performance implications linked to the interconnecting of devices, with the interconnected array configurations yielding a 75% increase in the annual energy extracted compared to the baseline (non-interconnected) arrangement. The performance enhancements are primarily attributed to the interconnecting moorings resulting in greater heave motion at higher frequencies for which the phase relationship between the water column and heave motion is more beneficial. Evidence is also presented that positive intra-array effects occur within interconnected arrays when the wavelength is equal to the array spacing.

A layout optimization method based on wave wake preprocessing concept for wave-wind hybrid energy farms

Major investment of renewable energy currently focuses on wind and solar, which are commercially mature. However, there is no large commercial application of wave energy, despite more than four decades of continuous development. Previous research has indicated that wave energy could supply a significant portion of world electricity consumption. Therefore, it is critical to incentivize the utilization of wave energy. The hybrid energy farms, combining wave energy with wind energy, have been considered as one of the most viable solutions to promote mature grid integration of wave energy. However, combining wind and wave requires the identification of adequate locations for both resources and development of layout optimization algorithms capable of handling the complexity of wave wakes. Wave wake analysis has been one of the biggest hurdles for the development of recursive wave farm layout optimization algorithms due to the required extremely time consuming computation processes for each wave wake iteration. This research proposes a new approach by preprocessing the wave wakes beforehand the actual execution of the recursive layout optimization algorithm. This proposed preprocessed wave wake model can be integrated with the different optimization algorithms to identify optimal layouts for hybrid wave-wind farms. The new approach was tested in two selected locations in the Gulf of Mexico with over 36 years (1979–2015) of historical meteorological data. It identifies locations capable of sustaining commercially viable levels of wind and wave energy while simultaneously avoiding risk from extreme oceanic conditions that in the past have damaged or destroyed wave energy converters. Although the two locations have different meteorological conditions, the new approach was able to identify layouts with promising results in both locations. Results indicated that the selected locations could produce very good power output with a wave-wind hybrid energy farm, and most wave and wind energy devices generated capacity factor with values higher than commercial threshold limits.

Optimal Design of Impulse Turbine Prototype of Oscillating Water Column Type Wave Energy Power Generation Device

The Oscillating Water Column Type is currently the most widely used wave energy generation device. The impulse turbine with fixed guide vanes has the advantages of high peak efficiency and excellent aerodynamic performance. Using three-dimensional numerical simulation methods to analyze the impulse turbine, construct and optimize the design of the turbine prototype, and provide suggestions for the subsequent innovation and improvement of the performance and structure of the impulse turbine with fixed guide vanes.