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This article substantiates the relevance of adopting hybrid transport systems. The circuit designs are chosen, and an algorithm of controlling the multifunctional energy converter for a hybrid transport system is developed. The performance of the system is analyzed using a multiconvector hybrid circuit with two energy storage units (a capacitor-design capacitive storage and an electrochemical storage battery). The multifunctional energy converter is modeled in the MATLAB/Simulink suite. The model is appropriate for the rational management of energy in transport systems in their various operational modes, which confirms the expediency of configuring and choosing circuit designs when creating a converter for a hybrid transport system.

In 2019 a Scientific Research & Demonstration Platform was deployed near islands and reefs in South China Sea by a joint research group of 7 institutes and universities in China. It is a simplified small model of a two-module semi-submersible-type VLFS. The test on site has continued for more than one and half years since then for long-term observations to validate the developed key technologies for design and behavior predictions of floating structures deployed near islands and reefs. An integrated information system was set up to continuously collect and inspect the data of the encountered waves, structure responses, connector forces, mooring line forces, anti-corrosion status of the platform, the performance efficiencies of a floating breakwater nearby and a wave energy converter attached on the breakwater. In this paper, the status of the on-site measurements and validations of the key technologies are briefly described.

The sorts of converters are characterized into six ages as per the qualities and improvement process. This characterization reviews all DC/DC converters and classifies new models. Since 2001, the DC/DC converter has been fabricated and this order has perceived in everywhere throughout the world. Presently it is anything but difficult to sort and apportion DC/DC converters and evaluate their specialized highlights. DC/DC converters are basic in assortment of uses including power supplies, for example, individual/smart phones, telephones, office equipment's, rocket control frameworks, and media transmission equipment's, and also heavenly bodies where input/yield voltage ranges cover. PWM age is viewed as the more essential in the Converter plan and a few multicarrier strategies have been produced to diminish the mutilation in level converters in light of the established with triangular transporters [1] . A DC/DC converter is an electronic circuit which changes over a wellspring of direct present (DC) starting with one voltage level then onto the next. It is a class of energy converter.

With the continuous development of society and economy, people’s demand for electric energy is increasing. The low-carbon and energy-saving technologies of renewable energy especially wave energy have become the focus of current researches. Considering the increasingly serious energy problems, a wave energy converter (WEC) is proposed based on Halbach permanent magnetic array, which increases the output performance. The equivalent magnetic circuit model of the WEC is established. The static magnetic field modeling and structural parameters optimal permanent of the WEC are performed on this theoretical. Theoretical studies have found that the optimal permanent magnet thickness ratios for Halbach permanent magnet array structures is 0.6, and the ratio of permanent magnet to coil radial ratio is 0.7. The coil winding form and rectifying circuit of the WEC were designed. The WEC equivalent magnetic circuit model was verified by COMSOL Multiphysics finite element software, and the open circuit voltages of WEC was obtained. If the WEC moves at a speed of 0.1 m/s, the coil voltage can reach about 113 V after simulation. According to the testing requirements of the WEC, a test platform was built. The Halbach permanent magnet array structures greatly enhances the wave energy collection of WEC.

The hydraulic power take-off (HPTO) is considered as the most promising method to convert wave power to electrical power. This paper presents an experimental assessment of the power conversion of a wave energy converter using HPTO. Based on the experimental results, a modification of accumulator pre-charged pressure and a control strategy were proposed to improve the system performance. System design, the working principle and mathematical model of all components were described. The proposed method was verified based on both simulation and experimental tests. The results showed that the system always works at an optimal condition under different input wave conditions.

The direct-drive Permanent Magnet Linear Generator (PMLG)-based Ocean Wave Energy Converter (OWEC) generates variable AC voltage, which cannot be directly utilized by the load. This paper presents ...

Since the input power of the real waves varies continuously and periodically, how to stabilise the operation and generation during wave energy utilisation has become an inevitable and significant topic. This study focuses on the wave energy converter of a hydraulic power take-off (HPTO) connected to a pendulum and studies the influences of the key components, i.e. the high-pressure accumulator, oil tank and flow control valve, on the operational stability of HPTO by simulations and experiments. Parameters of the high-pressure accumulator are analysed and optimised. The dynamic performance of the HPTO with or without the oil tank is also investigated. Besides, the functions of the flow control valve in the cases of excessive input power and load shedding are given. Results show that the key components play very important roles in the operational stability of HPTO. Reasonable configurations of the high-pressure accumulator and oil tank are significant to improve the quality of output power and stability. Appropriate actions of the flow control valve are beneficial to protection and stability. Therefore, these key components should be considered preferentially during the design of HPTO.

This article presents a methodology to find out a suitable ocean wave energy converter (OWEC) device for Indian coastal region. A comprehensive literature survey of all the existing OWEC devices is...

CECO is a wave energy converter (WEC) of the oscillating body type equipped with an inclined PTO system and being developed at the Faculty of Engineering of the University of Porto. In the last years, several research studies have been performed to assess and to improve the performance of this WEC, using both physical model tests and numerical simulations. The main objective of this paper is reviewing the most significant findings of past research works, so as to provide a detailed overview about the present status of knowledge, but also presenting recent outcomes on the development of CECO and the next research steps. It discusses the influence of the PTO slope angle and damping on the efficiency of CECO harvesting wave energy and describes its energy conversion stages. Furthermore, the intra-annual variability of the wave resource (i.e., on a monthly basis) is considered in the analysis of the influence of the PTO inclination and local water depth at the deployment site on CECO captured energy and captured energy efficiency, along the North Atlantic coast of the Iberian Peninsula. The results have shown significant differences between the summer and winter months and also highlighted the fact that the initial geometry of this WEC is more suitable for the less energetic wave climates, characteristic of the southern locations of the case study area and of shallow waters. The conclusions obtained supported the design of an enhanced version of CECO, prepared for the more energetic stretches of the study area, which presents a hydrodynamic efficiency of more than twice the original one, for the target wave conditions.

Since the hydraulic power take-off (PTO) is a widely-utilized transmission device for oscillating-body wave energy converters, its parameter configurations need to be optimized with an accurate dynamic model. To accurately describe the cylinder friction force, the motor loss and the accumulator working patterns, this paper establishes a novel nonlinear state space model for a hydraulic PTO. The model contains a stiction-involved Stribeck curve for the hydraulic cylinder, an improved Jeong's theory for the hydraulic motor and a pressure-bound-related formula for the high-pressure accumulator. The proposed model is simulated in irregular waves and verified via the comparison with the WEC models based on Yang's theory [1]. Furthermore, the research focuses on obtaining optimal PTO parameter configurations with the suitable piston area and resistance, according to the generating ability, energy conversion efficiency and pressure stability. The results show that the piston area has a more significant impact on the generating ability and pressure stability than the resistance but the same influence on the energy conversion efficiency. In general, a small piston area and a minor resistance are the superior configurations at the fixed capacity.

Energy resource classification systems are useful assessment tools that support energy planning and project development, e.g., siting and feasibility studies. They typically establish standard classes of power, a measure of the opportunity for energy resource capture. In this study, we develop wave energy resource classification systems for the US based on wave power (J, kW/m) and its distribution with peak period ( T p , s ). These metrics are calculated for 70,386 sites from partitioned bulk wave parameters generated from a validated 30-year WaveWatch III model hindcast. As the operating resonant period bandwidth of a wave energy converter (WEC) technology is an important design characteristic, the dominant period band containing the largest energy content is identified among three peak period band classes. These classification systems, comprised of four power classes and three peak period band classes, are based on the total wave power or the partitioned wave power in the dominant peak period band. They discriminate distinct trends in wave energy resource among five regions within the US, and provide useful information for energy planners, project developers, and technology designers. They also establish a framework for investigating the feasibility of a compatible wave climate (design load) conditions and WEC technology classification system to reduce design and manufacturing costs.

We consider the hydrodynamics of wave energy converter (WEC) arrays consisting of periodically repeated single bodies or sub-arrays. Of special interest is the array gain due to wave interactions as a function of the spatial configuration of the array. For simplicity, we assume identical WECs oscillating in heave only, although the results should extend to general motions. We find that array gains can be as high as $O(10)$ compared to the same WECs operating in isolation. We show that prominent decreases in array gain are associated with Laue resonances, involving the incident and scattered wave modes, for which we obtain an explicit condition. We also show theoretically that Bragg resonances can result in large decreases in gain with as few as two rows of strong absorbers. For general WEC geometries, we develop a multiple-scattering method of wave–body interactions applicable to generally spaced periodic arrays. For arrays of truncated vertical cylinders, we perform numerical investigations confirming our theoretical predictions for Laue and Bragg resonances. For a special class of multiple-row rectangular WEC arrays, our numerical results show that motion-trapped Rayleigh–Bloch waves can exist and be excited by an incident wave, resulting in sharp, narrow-banded spikes in the array gain.

Photon enhanced thermionic emission (PETE) is a new concept in solar energy conversion, combining thermal and photovoltaic carrier excitations with thermionic emission. A solar-power-driven thermionic energy converter operates by illuminating the solar light condensed by a large-scale Fresnel lens to convert heat energy into electrical energy. By enhancing the efficiency of converting solar radiation into the emitter internal energy, the output power and efficiency of the thermionic energy converter can be greatly improved. In this study, using numerical simulations, the effects of emitter temperature and output characteristics on a thermionic energy converter were investigated. The results showed that the higher rate of the heating power represented the higher temperature of an emitter, as well as output current density, and efficiency. In addition, by reducing the diameter of a collector and thermal conductivity of insulation materials, or increasing the diameter of emitter, the temperature of emitter, output current density, and efficiency could be notably improved. It is also worth mentioning that the main factor that affected the emitter temperature in the process of heat transfer was heat conduction between solids. In conclusion, adequate illumination, reasonable size of collector and emitter, as well as appropriate insulation measurements could efficiently improve the output characteristics of thermionic energy converter.

Distinct from conventional energy‐harvesting (EH) technologies, such as the use of photovoltaic, piezoelectric, and thermoelectric effects, betavoltaic energy conversion can consistently generate uniform electric power, independent of environmental variations, and provide a constant output of high DC voltage, even under conditions of ultra‐low‐power EH. It can also dramatically reduce the energy loss incurred in the processes of voltage boosting and regulation. This study realized betavoltaic cells comprised of p‐i‐n junctions based on silicon carbide, fabricated through a customized semiconductor recipe, and a Ni foil plated with a Ni‐63 radioisotope. The betavoltaic energy converter (BEC) includes an array of 16 parallel‐connected betavoltaic cells. Experimental results demonstrate that the series and parallel connections of two BECs result in an open‐circuit voltage Voc of 3.06 V with a short‐circuit current Isc of 48.5 nA, and a Voc of 1.50 V with an Isc of 92.6 nA, respectively. The capacitor charging efficiency in terms of the current generated from the two series‐connected BECs was measured to be approximately 90.7%.

The wave energy resource along the Northern Spanish coast is determined, for a period of 33 years (1979–2012) based on hindcast results of WAVEWATCH III for the Atlantic ocean area, coupled with the SWAN model for the coastal areas, and using surface winds from ECMWF's ERA- Interim data base. Results are validated with buoy data, in order to evaluate the model's accuracy. Statistical analysis of the wave parameters and wave power results are presented. The analysis was carried out for a coarse grid, on the North of Spain, and for three local areas with a finer mesh: Northwest Galicia, the area between Cape San Adrian and Cape Ortegal and Santander. The case studies include a more realistic perspective of the amount of energy that can be extracted with a wave energy converter, by adopting examples of a large and a small device. A seasonal variability evaluation is done for the nested areas through the analyzes of the seasonal average wave power resource for the different locations, throughout the 33 year hindcast, and the joint distributions of significant wave height and peak period for the number of occurrences and wave power.

To maximize energy conversion, real-time control of a wave energy converter (WEC) requires knowledge of the present and future excitation force ( $F_{\rm{ex}}$ ) acting on the device, which is a nonmeasurable quantity. The problem of estimation and forecasting of $F_{\rm{ex}}$ becomes more challenging when arrays of WECs are considered, due to the hydrodynamic interactions in the array. In this paper, a global $F_{\rm{ex}}$ estimator for a complete WEC array is developed and compared to a set of independent estimators, which utilize information local only to each device. A significant question is whether the array of measurements is sufficient to compensate for the greater complexity of the wave field, compared to the isolated body case. The paper shows that the global estimator is always more accurate than the independent estimator, improving up to $\text{45}\%$ the estimation accuracy of the independent estimator. Regarding prediction, two different $F_{\rm{ex}}$ forecasters for a WEC array are compared: a global forecaster, utilizing $F_{\rm{ex}}$ estimates from the full set of array devices, and an independent forecaster, utilizing only a local $F_{\rm{ex}}$ estimate. We demonstrate that the global forecaster achieves more accurate results, not only compared to the independent forecaster, but also compared to the isolated body case.

Wave energy has the potential to play an important role in the UK's electricity mix in the coming years and it is important to understand the interactions of wave energy converters with the environment before considering them viable alternatives for other technologies. The aim of this study was to identify the environmental impacts of the deployment of the Oyster wave energy converter to the EMEC test site at Orkney, UK over its lifetime across three general categories: resource use, human health and ecological consequences. A full life cycle assessment was performed on two different models of the Oyster wave energy converter: Oyster 1 and Oyster 800. It was found that the latter is a fitting upgrade for its predecessor as it has lower environmental impacts in all categories; however, the high infrastructural needs of the Oyster technology makes its environmental performance worse than most other wave energy converters. Key sustainability indicators for energy converters include carbon footprint and energy payback period, and these were found to be 79 and 57 gCO2 eq/kWh and 45 and 42 months for the Oyster 1 and Oyster 800, respectively. Although these are significantly higher than most estimates for other types of renewable energy converter, the carbon impacts are still significantly lower than for conventional fossil-fuelled power generation.

Vortex-induced oscillations offer a potential means to harness hydrokinetic energy even at low current speeds. In this study, we consider a novel converter where a cylinder undergoes angular oscillations with respect to a pivot point, in contrast to most previous configurations, where the cylinder undergoes flow-induced oscillations transversely to the incident free stream. We formulate a theoretical model to deal with the coupling of the hydrodynamics and the structural dynamics, and we numerically solve the resulting nonlinear equation of cylinder motion in order to assess the performance of the energy converter. The hydrodynamical model utilizes a novel approach where the fluid forces acting on the oscillating cylinder are split into components acting along and normal to the instantaneous relative velocity between the moving cylinder and the free stream. Contour plots illustrate the effects of the main design parameters (in dimensionless form) on the angular response of the cylinder and the energy efficiency of the converter. Peak efficiencies of approximately 20% can be attained by optimal selection of the main design parameters. Guidelines on the sizing of actual converters are discussed.

This paper aims to investigate electric dynamics and improve electric power generation of an isolated wave energy converter that uses a linear permanent magnet generator as the power take-off system, excited by regular or irregular waves. This is of significant concern when considering actual operating conditions of an offshore wave energy converter, where the device will encounter different sea states and its electric load needs to be tuned on a sea-state-to-sea-state basis. To that end, a fully coupled fluid-mechanical-electric-magnetic-electronic mathematical model and an optimization routine are developed. This proposed time-domain wave-to-wire model is used to simulate the hydrodynamic and electric response of a wave energy converter connected to specific electric loads and also used in an optimization routine that searches optimal resistive load value for a wave energy converter under specific sea states. Sample results are presented for a point-absorber type wave energy converter, showing that the electric power generation of a device under irregular waves can be significantly improved. Keywords: wave energy converter, wave power system, wave-to-wire model, linear permanent magnet generator, electric load optimization., Comment: Accepted by Energy

In this paper a system for experiments on redox flow batteries is presented, giving the operator the possibility of dealing independently with advantages and challenges of this innovative energy converter, in particular with regard to testing new, in this case recycled, materials. The recycling aspect is included due to the permanent requirement of reducing cost of especially as far as bipolar plates is concerned. In addition the hole recycling discussion, it is necessary to use the material recycling in different stages of system development and evaluation. Included in the tests was the development of a four-part series of experiments, in the framework of which the operators will treat intensely the cell structure, its characterization as well as testing of the electrolytes and the challenge of the crossover.

School of Engineering of the University of Plymouth Hydraulic Engineering research area of the University of Santiago de Compostela

The influence of the central platform on hydrodynamic performance of a wave energy converter (WEC) has remained elusive. To approach this dearth of relevant theoretical research, this paper presents a semi-submerged multi-buoy WEC and the results of the numerical analysis at different dimension parameters of the central platform of the WEC. The WEC consists of three oscillating buoys hinged with a central platform through multiple actuating arms. Numerical analysis revealed that there exists a relationship between the hydrodynamic performance of device and the geometry of the central platform. At the given wave condition, different central platform size would obviously affect the hydrodynamic performance and wave energy capture width ratio of the semi-submerged multi-buoy WEC. Additionally, appropriately increasing central platform draft would help to improve the wave energy capture capability of the oscillating buoys.

Proton Exchange Membrane Fuel Cell (PEMFC) has become a promising power source with wide applications to many electronic and electrical devices. However, even if it is a competitive energy converter, PEMFC still suffers from its limited lifespan. Prognostics appear to be a good solution to helping take actions to extend its lifetime. Considering both advantage and disadvantage of model-based and data-driven based prognostic methods, this study proposes a hybrid prognostic method for PEMFC based on a data-driven method, least square support vector machine (LSSVM) and a model-based method, regularized particle filter (RPF). The main contributions of the proposed method include: 1) It can provide not only an estimated value but also an uncertainty characterization of RUL with a probability distribution; 2) It has a better capability to capture the nonlinearities in degradation data and a lower reliance on PEMFC degradation model; 3) The RPF method improves the standard particle filter algorithm by reducing the degeneration phenomenon and loss of diversity among the particles. Effectiveness of the proposed method is verified based on PEMFC dataset provided by FCLAB Research Federation. The results indicate that the proposed hybrid method can effectively combine both advantages of data-driven and model-based methods, providing a higher accuracy of RUL prediction for PEMFC.

The analysis of electromechanical energy converters based on metal-thin film ferroelectric (with a large specific capacitance)-nanogap-moving electrode structures was performed. It was shown that the density of the energy being converted and its absolute value increase with the decreasing gap value between the surfaces of the ferroelectric and the metallic moving electrode up to nanometer values. The effects limiting the growth of this energy were established, and the limiting value of the energy density transformed in the nanogap of these structures was determined to be about 1.6 &times, 1010 J/m3, which is 4 orders of magnitude higher than the energy density in inductive converters. The experimental verification of this model based on the data for micromotors fabricated on these structures is given.

Autonomous underwater vehicle (AUV) docking and wave energy converters (WECs) have been investigated thoroughly over past decades. Separate development of these technologies in the past few years by the authors are being brought together to propose an underwater docking system for a WEC-based mobile station. This paper presents the concept of WEC-based offshore AUV residency and reports the development of the proposed system. A finite-horizon model predictive control approach is presented to demonstrate the feasibility of “rendezvous” style docking of a box-type AUV to a simulated WEC experiencing sinusoidal vertical oscillations. It is found that the AUV tends to approach the dock when its oscillatory velocity approaches zero.

This paper proposes a tubular permanent magnet linear generator (TPMLG) for a wave energy converter. The proposed TPMLG is built with an array of permanent magnets and independent coils. Advantages and disadvantages of the proposed device are determined with experimental and simulated results. A lumped parameter method is applied to analyze the amplitude of induced voltage and magnetic field mathematically. A finite element analysis is employed in the simulation software to obtain the dynamical behavior of these variables. The translator is tested at three different speeds. A prototype is built to confirm the theoretical analysis and simulations. Simulation and experimental results confirm the mathematical relationship between speed and the induced voltage.

CuNbO3 is a promising semiconductor for photovoltaic and photo-electro-chemical conversion. To evaluate its potential, it is necessary to analyze the optical properties and quantify the main features when this material is used as an energy converter. To achieve this aim, first the optical properties are obtained using first-principles. The results, based on the split into contributions, show that the light absorption comes mainly from the p(O)-d(Nb) transitions of the NbO6 octahedra. Later the absorption coefficients are used as criteria to evaluate photo-voltages, photocurrents and efficiencies of the solar conversion, and the effect of using total and partial solar spectrum ranges. Furthermore, we show that the efficiencies and photocurrents could be increased significantly using a multi-gap approach. Furthermore some voltage loss effects are analyzed.

Efficient design of wave energy converters requires an accurate understanding of expected loads and responses during the deployment lifetime of a device. A study has been conducted to better understand best-practices for prediction of design responses in a wave energy converter. A case-study was performed in which a simplified wave energy converter was analyzed to predict several important device design responses. The application and performance of a full long-term analysis, in which numerical simulations were used to predict the device response for a large number of distinct sea states, was studied. Environmental characterization and selection of sea states for this analysis at the intended deployment site were performed using principle-components analysis. The full long-term analysis applied here was shown to be stable when implemented with a relatively low number of sea states and convergent with an increasing number of sea states. As the number of sea states utilized in the analysis was increased, predicted response levels did not change appreciably. However, uncertainty in the response levels was reduced as more sea states were utilized.

The potential of wave power as an alternative energy resource is being studied to address problems associated with fossil fuel exhaustion and environmental pollution. In this paper, to improve the power generation efficiency of a floating-type wave-energy converter that has an activating body, the effects of the positions of a connecting bridge and different connecting methods between a main body and the activating body of the wave-energy converter were studied. In order to research the activating body’s motion characteristics that are caused by the changes of connecting bridge’s position and connecting methods; hinged or fixed connector, the wave-energy converter was modeled and simulated by using a commercial software. The moment and angular velocity of the axis of power generation were measured from the results of simulations and then the power outputs were calculated based on the moment and angular velocity. The outputs, which were analyzed under several regular wave conditions, were compared to each other.

The applicability of Sea-wave Slot-cone Generator breakwater as a system of energy converter in the southern coasts of Iran is investigated. Several efficient factors simultaneously have been considered, including the period and the significant height of wave, the effective depth, and the hydraulic efficiency. The field data used in this study are those derived from the stationary buoys. Findings reveal that Asaluyeh and Shahid-Beheshti ports are the only places, which might satisfy the required needs. The percentage of hydraulic efficiency achieved, however, is less than what is suggested in the literature as the minimum acceptable level. In other words, the use of Sea-wave Slot-cone Generator breakwater is not financially affordable in the southern coasts of Iran.

The information of the wave loads on a wave energy device in operational waves is required for designing an efficient wave energy system with high survivability. It is also required as a reference for numerical modeling. In this paper, a novel system, which integrates an oscillating wave energy converter with a pile-restrained floating breakwater, is experimentally investigated in a 2-D wave flume. The measurements of the wave pressure on the wet-surface of the device are made as the function of the power take-off (PTO) damping force. It is shown that the wave pressure is significantly affected by the PTO system, in particular, at the edges, and the wave pressure varies under different wave conditions. From the results, conclusions can be drawn on how the PTO damping force and wave conditions affect the loads on the device, which is of engineering concern for constructing safe and reliable devices.

In the present paper, the development of a model scale Wave Energy Converter (WEC) and an experimental WEC test rig are presented, and results of numerical simulations and experimental measurements are shown. The presented point absorber WEC is coupled to a generic power take-off (PTO) and is restricted to pure heave motion in regular waves. Experiments were carried out at the Universidad Austral de Chile (UACh) Wave Tank and results from responses and efficiencies were compared with data from the BEM (boundary element method) code WAMIT. Numerical and experimental results showed good agreement. Finally, results were extrapolated and superposed with typical wave energy spectra found in different Chilean regions, providing a first performance estimation for a wave energy converter in Chile. Results are discussed and compared with an existing technology and give an insight of the potential for wave energy technologies in Chile. Further investigation is proposed for an analysis in irregular waves and the use of a more advanced PTO (power take-off) in the future.

The article describes the high temperature winding wires, highly coercive permanent magnets, and electrical steels for high temperature starter-generators.

In this paper, the non-linear effects of viscosity on the performance of a Wave Energy Converter (WEC) system are analysed. A standard linear Model Predictive Control (MPC) is used to show the negative effects that the unaccounted non-linear viscosity force in the hydrodynamic system has on the power absorption. A non-linear MPC (NLMPC) is then implemented, where the non-linear viscosity effects are included in the optimisation. A linear drag coefficient estimate of the non-linear viscosity is then included in the linear MPC; creating a Linear Viscous Model Predictive Control. When constraints are incorporated, it is shown that a single choice of the linear viscous drag coefficient for use within the linear MPC can provide comparable results to the non-linear MPC approach, over a wide range of sea states.

Summary A compact buoy-array-type wave energy converter called multi-heaving-buoys (MHB) is introduced in this study. The hydrodynamic performance of MHB under regular wave conditions was first investigated experimentally in a wave tank located in Ocean University of China. It was found that a limited number of heaving buoys had little effect on the wave fields around the device. The small period of the incident waves caused an intense interaction between the waves and the buoys. The phase difference between the buoys in different rows was determined by the distance between the buoys. It was found that the response amplitude operator of the buoys varied from 0.6 to 1.2. Correspondingly, the range of the averaged relative velocity of the heaving buoys was 0.6–1.3. The upper limit of the acceleration of the buoys' motion was 0.2 times that of gravity. All of the experimental results provide valuable information for the future design of the hydraulic pressure power take-off systems. Copyright © 2017 John Wiley & Sons, Ltd.

In this paper, we propose a novel wave energy converter (hereinafter called Wave Loong®) consisting of two rafts hinged at each raft end and one pendulum hung at the joint of the rafts. A mathematical model based on the linear wave theory with the consideration of three bodies hinged together and various connection conditions between any two of the three bodies is presented to investigate the performance of the converter. The effect of damping coefficient, raft length, pendulum length, pendulum radius of gyration, pendulum mass and wavelength on capture width ratio is analysed, and the mechanisms underlying wave energy capture are explored. The comparison of capture width ratios for the converter with and without a pendulum is made to demonstrate that the performance of the Wave Loong® is much better than a conventional raft-type WEC in terms of capture width ratio and wavelength bandwidth. The comparison of capture width ratios for the WECs with various connection conditions between any two of a fore raft, aft raft and pendulum is also made to evaluate which kind of connection condition is superior.

This paper investigates a 15-slot tubular permanent-magnet linear motor (TPMLM) for a free-piston energy converter. In order to meet the performance requirements of the system, the mass of mover is strictly limited. Under this condition, three permanent-magnet (PM) mover structures of TPMLM are analyzed and compared. Then, the quasi-halbach PM mover structure is selected and further optimized. Finally, the mechanical strength of the motor with two support materials is analyzed, and the feasible mechanical scheme is given.

In this paper, a method for implementing model predictive control for vibration energy harvesting systems with the goal of maximizing generated energy is presented. This is generally a nonconvex problem, which can be computationally expensive and converging to a global minimum cannot be guaranteed. We introduce a dual-domain method to relax the nonconvex primal problem into a convex dual optimization problem, which can be performed in real time. Based on previous work, we determine when the duality gap is zero and, by extension, whether the global optimal primal solution is found. We demonstrate the algorithm on a single, buoy-type wave energy converter with energy storage constraints and power take-off force constraints.

Wave energy is an attractive source of renewable energy. In regions with a cold climate, for example, in the Baltic Sea, a good understanding of ice loads is vital for developing a reliable...

OBREC is the acronym that stands for Overtopping Breakwater for Energy Conversion. It is a multifunctional device aimed to produce energy from the waves, while keeping the harbour area protected from flooding. In this paper, the inclusions of a berm to reduce wave reflection, the shape of the sloping plate to maximise wave overtopping and the reservoir width and the crown wall shape to maximise wave energy capture while keeping the harbour safety were analysed to optimize the hydraulic and structural performances of the device. Several configurations were numerically investigated by means of a 2DV RANS-VOF code to extend the results already obtained during previous experimental campaigns. The wave reflection coefficient, the average wave overtopping flows and the wave loadings along the structure are computed, compared with existing formulae and discussed with reference to the OBREC prototype installed in the Port of Naples.

The Tupperwave device is a wave energy converter based on the Oscillating Water Column (OWC) concept. Unlike conventional OWC devices, which are opened to the atmosphere, the Tupperwave device works in closed-circuit and uses non-return valves and accumulator chambers to create a smooth unidirectional flow across a unidirectional turbine. The EU-funded OceanEraNet project called Tupperwave was undertaken by a consortium of academic and industrial partners, aimed at designing and modelling the Tupperwave device. The device was numerically modelled using two different methods. It was also physically modelled at the laboratory scale. The various modelling methods are discussed and compared. An analysis of the dependence of the device efficiency on the valves and turbine aerodynamic damping is carried out, using both physical and numerical approaches.

The exploitation of sea wave represents an important frontier for the energy sustainability in the next future. Despite the proposal of several techniques and solutions, commercial devices are not available. In this context, the Department of Engineering is investigating an innovative solution based on linear energy generators. This machine can be adopted as the main component in a wave energy converter, that is the device for the energy extraction of sea wave. Starting from an existing prototype, the paper examines the replacement of the iron stator with a non-magnetic material, in order to solve several common problems of linear generators, such as the cogging force. Results are reported, considering the no-load voltages and the cogging force produced by the generator in both cases.

Unidad de excelencia María de Maeztu MdM-2015-0552 Current narrative on biofuels is backed up by a large number of studies published in the scientific literature that address second-generation bioethanol only through a single topic approach, nonetheless in the vast majority of cases transition to this energy carrier is evaluated as a generally 'promising' technology. This paper presents a first attempt in proposing an integrated evaluation of the actual benefits expected from bioethanol in the transport sector, by applying the Multi-Scale Integrated Analysis of Societal and Ecosystem Metabolism (MuSIASEM) to the prospective realization of a local system of bio-refinery in Campania Region (Southern Italy). MuSIASEM is a multi-criteria analysis enabling to deal with the complexity of a territorial energy system. Since the unavoidable intrinsic uncertainty, the study does not focus on predictions, but adopts a strategy of Quantitative Story-Telling about some relevant results underlying the limits and critical issues about the energy converter fabric, the economic profitability, environmental constraints and the questionable concept of marginal land. The findings suggest concluding toward falsification of key points in the current narrative: (i) the system is not an efficient solar energy converter; (ii) it fails to realize many of the expectations for a renewable energy carrier producer; (iii) the contribution to decarbonization strategies is not as high as desired and other environmental impacts could not be neglected; (iv) the very large land requirement is hardly compatible with conversion of truly marginal land in Campania region; (v) compared to alternate land uses it does not seem an actually promising strategy to regain value from rural economy.

This paper presents a wave energy converter which is based on a sliding mass coupled to a linear generator. In order to maximize energy extraction, the stochastic features of the energy source has been included in the mathematical model of the system in order to satisfactorily tackle the problem. The results of several simulations are presented.

In this paper we introduce a pitch wave force predictor for a wave energy converter. The designed predictor is composed of two subsystems. First, we design a virtual sensor in order to provide a real-time estimate of the pitch wave force acting on the converter, from measurements provided by a set of on-board sensors. Then, we build an autoregressive predictor on such a virtual measurement to predict the future value of the wave force over a finite prediction horizon length. Simulation results, performed by applying the proposed algorithm on a first-principles based Simulink model of the considered sea wave energy converter, demonstrate the effectiveness of the proposed approach.

In this study, a series of modules is integrated into a wave-to-wire (W2W) model that links a Boundary Element Method (BEM) solver to a Wave Energy Converter (WEC) motion solver which are in turn coupled to a wave propagation model. The hydrodynamics of the WECs are resolved in the wave structure interaction solver NEMOH, the Power Take-off (PTO) is simulated in the WEC simulation tool WEC-Sim, and the resulting perturbed wave field is coupled to the mild-slope propagation model MILDwave. The W2W model is run for verified for a realistic wave energy project consisting of a WEC farm composed of 10 5-WEC arrays of Oscillating Surging Wave Energy Converters (OSWECs). The investigated WEC farm is modelled for a real wave climate and a sloping bathymetry based on a proposed OSWEC array project off the coast of Bretagne, France. Each WEC array is arranged in a power-maximizing 2-row configuration that also minimizes the inter-array separation distance d x and d y and the arrays are located in a staggered energy maximizing configuration that also decreases the along-shore WEC farm extent. The WEC farm power output and the near and far-field effects are simulated for irregular waves with various significant wave heights wave peak periods and mean wave incidence directions &beta, based on the modelled site wave climatology. The PTO system of each WEC in each farm is modelled as a closed-circuit hydraulic PTO system optimized for each set of incident wave conditions, mimicking the proposed site technology, namely the WaveRoller&reg, OSWEC developed by AW Energy Ltd. The investigation in this study provides a proof of concept of the proposed W2W model in investigating potential commercial WEC projects.

This paper reports the results of laboratory in-water experiments in which artificially marine-fouled circular cylinders were freely vibrating in the wake of a similar fixed upstream cylinder. Cross-flow vibrations at gaps of 3–7 diameters were examined. The marine fouling was simulated by CNC machining of uniformly distributed single-sized pyramids on the surface of the test cylinders. Depending on the spacing ratio, the smooth tandem cylinder demonstrated both Vortex-Induced Vibration (VIV) and galloping types of response. Interestingly, only the VIV-like response was presented by the artificially marine-fouled cylinder. The maximum amplitude of the oscillations and maximum lift force coefficient of the marine-fouled tandem cylinders were, respectively, around one-third and two-thirds of those in the corresponding smooth tandem cylinders. In the case of tandem circular cylinders, the marine fouling showed two contradictory outcomes. It eliminated the galloping and suppressed the VIV-like response, which is beneficial from structural integrity standpoint. From energy performance point of view, the marine fouling negatively affects the energy harvested in a marine hydrokinetic energy converter.

Optimal control strategies represent a widespread solution to increase the extracted energy of a Wave Energy Converter (WEC). The aim is to bring the WEC into resonance enhancing the produced power without compromising its reliability and durability. Most of the control algorithms proposed in literature require for the knowledge of the Wave Excitation Force (WEF) generated from the incoming wave field. In practice, WEFs are unknown, and an estimate must be used. This paper investigates the WEF estimation of a non-linear WEC. A model-based and a model-free approach are proposed. First, a Kalman Filter (KF) is implemented considering the WEC linear model and the WEF modelled as an unknown state to be estimated. Second, a feedforward Neural Network (NN) is applied to map the WEC dynamics to the WEF by training the network through a supervised learning algorithm. Both methods are tested for a wide range of irregular sea-states showing promising results in terms of estimation accuracy. Sensitivity and robustness analyses are performed to investigate the estimation error in presence of un-modelled phenomena, model errors and measurement noise.