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Utilizing ocean wave energy as a renewable energy source has become the object of rapid research. Energy conversion technology continues to evolve to seek more efficient, cheaper forms of investment, operation, and maintenance and are environmentally friendly. The converter type and PTO hold the key to the efficiency of the whole system. This literature review paper examines various general concepts and innovations of wave activated body converters and commonly used and innovative power take-off systems with a focus on controlling efforts in maximizing the generated power, challenges and efforts to develop a PTO control system as well as various research conducted by various parties.

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The production efficiency and optimal control of wave energy converter (WEC) array are mainly based on array layout, thus it is crucial to establish a reliable mathematical model for the WEC array layout optimization. So far, a lot of research has been done on the modeling and methods of WEC array layout optimization. However, the existing reviews are either incomplete in the classification of modeling methods, or incomplete in a collection of optimization methods, especially lacking detailed evaluation. This paper aims to comprehensively summarize various WEC models and related approaches for WEC array layout optimization. Note that over 80 related pieces of literature have been carefully analyzed and summarized, and they are divided into three categories: meta-heuristic-based, machine learning-based, and mathematics-based methods. In particular, the advantages/disadvantages, variables, evaluation indices, parameters, complexity, and objective functions are thoroughly discussed. Finally, potential research directions and recommendations are proposed in future in-depth research for both researchers and engineers.

For generating electricity, direct-drive wave energy converters (WECs) with linear permanent magnet generators (LPMGs) have advantages in terms of efficiency, simplicity, and force-to-weight ratio over WEC with rotary generators. However, the converter’s work under approaching-real wave conditions should be investigated. This paper studies the performance of a pico-scale WEC with two different LPMGs under unidirectional long-crested random waves. Different significant wave heights (using data in the Southern Ocean of Yogyakarta, Indonesia) and peak frequencies are tested. The JONSWAP energy spectrum is used to extract the wave elevations, while the MSS toolbox in MATLAB Simulink is employed to solve the floater’s dynamic responses. Next, the translator movements are extracted and combined with the flux distribution from FEMM simulation and analytical calculation, and the output powers are obtained. An experiment is conducted to test the output under constant speed. The results show for both designs, different tested significant wave height values produce higher output powers than peak frequency variation, but there is no specific trend on them. Meanwhile, the peak frequency is inversely proportional to the output power. Elimination of the non-facing events results in increasing output power under both parameters’ variation, with higher significant wave height resulting in a bigger increase. The semi iron-cored LPMG produces lower power loss and higher efficiency.

The levellised cost of energy of wave energy converters (WECs) is not competitive with fossil fuel-powered stations yet. To improve the feasibility of wave energy, it is necessary to develop effective control strategies that maximise energy absorption in mild sea states, whilst limiting motions in high waves. Due to their model-based nature, state-of-the-art control schemes struggle to deal with model uncertainties, adapt to changes in the system dynamics with time, and provide real-time centralised control for large arrays of WECs. Here, an alternative solution is introduced to address these challenges, applying deep reinforcement learning (DRL) to the control of WECs for the first time. A DRL agent is initialised from data collected in multiple sea states under linear model predictive control in a linear simulation environment. The agent outperforms model predictive control for high wave heights and periods, but suffers close to the resonant period of the WEC. The computational cost at deployment time of DRL is also much lower by diverting the computational effort from deployment time to training. This provides confidence in the application of DRL to large arrays of WECs, enabling economies of scale. Additionally, model-free reinforcement learning can autonomously adapt to changes in the system dynamics, enabling fault-tolerant control.

In this paper, a new type of ocean wave energy converter designated as the Articulated Tower - Ocean Wave Energy Converter (AT-OWEC) is introduced, especially for operation in Indonesian waters. The working principle is converting the rotational pitching motion of AT as the main structure when induced by wave excitation into translational motion of an arm to propel a double action piston pump (DAPP) which drive the water jet to move a turbine and hence generate electricity. At this stage the work is concentrated in the evaluation of the AT dynamic behavior under regular wave excitation. The formulation of the AT rotational pitch motion in 1-DOF is described, and is followed by the modelling utilizing analytical and numerical models. A case study is conducted on 3 variations of AT size to be operated in three different water depths d, namely 10.0 m, 15.0 m and 20.0 m. The variants are made of steel sized, Variant #1 Dh = 2.0 m, Hh = 3.5 m, t = 10.0 mm, Variant #2 Dh = 3.0 m, Hh = 4.5 m, t = 25.0 mm, and Variant #3 Dh = 4.0 m, Hh = 5.5 m, t = 30.0 mm. The results of the analysis show the largest RAO pitch motion occur in the case of Variant #1 when operated in the water depth d = 10.0 m reaching 49.24 deg/m, while the lowest one occurs in the case of this variant when operated in d = 20.0 m with the intensity of only 16.06 deg/m. Nonetheless, AT of Variant #3 is found to be more potential to harvest the greater wave energy in conjunction with the peculiar characteristic of the Indonesia sea wave frequency range.

Ocean wave energy is one of the most abundant energy sources in the world. There is a wide variety of wave energy conversion systems that have been designed and developed, resulting from the different ways of ocean wave energy absorption and also depending on the location characteristics. This paper reviews and analyses the concepts of hydraulic power take-off (PTO) system used in various types of wave energy conversion systems so that it can be a useful reference to researchers, engineers and inventors. This paper also reviews the control mechanisms of the hydraulic PTO system in order to optimise the energy harvested from the ocean waves. Finally, the benefits and challenges of the hydraulic PTO system are discussed in this paper.

Wave energy's path towards commercialization requires maximizing reliability, survivability, an improvement in energy harvested from the wave and efficiency of the wave to wire conversion. In this sense, control strategies directly impact the survivability and safe operation of the device, as well as the ability to harness the energy from the wave. For example, tuning the device's natural frequency to the incoming wave allows resonance mode operation and amplifies the velocity, which has a quadratic proportionality to the extracted energy. In this article, a review of the main control strategies applied in wave energy conversion is presented along their corresponding power takeoff (PTO) systems.

Passive loading is a suboptimal method of control for wave energy converters (WECs) that usually consists of tuning the power take-o� (PTO) damping of the WEC to either the energy or the peak frequency of the local wave spectrum. Such approach results in a good solution for waves characterized by one-peak narrowband spectra. Nonetheless, real ocean waves are non-stationary by nature, and sea wave pro�les with di�erent spectral distribution occur in a speci�c location over time. Thus, the average energy absorption of passively controlled WECs tends to be low. In this paper, we propose a real-time passive control (PC) based on the Hilbert-Huang transform (HHT), where the PTO damping is time-varying and tuned to the instantaneous frequency of the wave excitation force. The instantaneous frequency is calculated by using the HHT, an analysis method for nonlinear and non-stationary signals that relies on the local characteristic time-scale of the signal. A performance comparison (in terms of energy absorption) of the proposed solution with the passive loading method is presented for a heaving system, in a variety of wave spectra. It is shown that a performance improvement of up to 21%, or 65%, is obtained for the proposed PC scheme, when it is compared to passive loading tuned to the energy, or the peak frequency of the spectrum, respectively. Real ocean waves o� the west
coast of Ireland are adopted in the simulations.

An oscillating buoy wave energy converter (WEC) integrated to an existing box-type breakwater is introduced in this study. The buoy is installed on the existing breakwater and designed to be much smaller than the breakwater in scale, aiming to reduce the construction cost of the WEC. The oscillating buoy works as a heave-type WEC in front of the breakwater towards the incident waves. A power take-off (PTO) system is installed on the topside of the breakwater to harvest the kinetic energy (in heave mode) of the floating buoy. The hydrodynamic performance of this system is studied analytically based on linear potential-flow theory. Effects of the geometrical parameters on the reflection and transmission coefficients and the capture width ratio (CWR) of the system are investigated. Results show that the maximum efficiency of the energy extraction can reach 80% or even higher. Compared with the isolated box-type breakwater, the reflection coefficient can be effectively decreased by using this oscillating buoy WEC, with unchanged transmission coefficient. Thus, the possibility of capturing the wave energy with the oscillating buoy WEC integrated into breakwaters is shown.

This paper highlights the need to optimise the performance of the complete wave to wire system, instead of designing the individual subsystems. In this work a point absorber wave energy converter operating in heave mode separately, coupled to a Linear Permanent Magnet Generator (LPMG); where the results are obtained in simulation. The PTO force is controlled by a machine side back-to-back voltage source converter (VSC), which is connected to a constant DC-link voltage. Model Predictive Control (MPC) is then used to maximise the absorbed electrical power with the resistive losses of the PTO included; this is compared with classical control methods. The optimal force produced from the MPC incorporates legitimate physical and electrical constraints of the WEC and LPMG -the importance of including such constraints within the optimisation is shown. Field weakening and a uni-directional power flow constraint are then incorporated to help prevent poor grid power quality when fluctuations in the DC-link occur. It is assumed that the constrained optimal control approach produces the highest possible electrical power available. This means that it is now possible to clearly see the effect of physical design choices on the performance on a level playing field.

The power take-off systems consisted in wave energy converters are studied in this
paper. Wave energy converters are systems that are designed to produce electricity by
capturing the power of ocean surface waves. Research activities on producing electricity
from environmentally friendly and sustainable sources have been in progress since the days
of Energy Crisis. Ocean waves are one of such energy sources. Many different types of
wave energy converters were designed so far. The power of waves is converted into
electricity by the power take-off system of the wave energy converter. High pressure oil
hydraulic systems, air turbines, hydraulic turbines and linear generators are frequently
used types of power take-off mechanisms. Each type of system has its advantages and
disadvantages. The decision on which type of power take-off system to be used in a wave
energy converter mainly depends on the method of capturing the power of waves.

Ocean waves are a huge, largely untapped energy resource, and the potential for extracting energy from waves is considerable. Research in this area is driven by the need to meet renewable energy targets, but is relatively immature compared to other renewable energy technologies. This review introduces the general status of wave energy and evaluates the device types that represent current wave energy converter (WEC) technology, particularly focusing on work being undertaken within the United Kingdom. The possible power take-off systems are identified, followed by a consideration of some of the control strategies to enhance the efficiency of point absorber-type WECs. There is a lack of convergence on the best method of extracting energy from the waves and, although previous innovation has generally focused on the concept and design of the primary interface, questions arise concerning how best to optimize the powertrain. This article concludes with some suggestions of future developments.

Ocean waves contain one of the world's largest untapped and predictable renewable energy sources that can be used to fulfil the energy demand in the present energy crises situation. There are many devices that have been proposed and prototyped in different countries all around the world to harness wave energy based on different power take-off (PTO) systems. The aim of this article is to review the power take-off (PTO) systems of the wave energy converters (WEC). The review starts with a brief introduction and background of wave energy. Following this, a novel classification of WEC systems is introduced. Then, the WECs based on the different working methods of their power take off systems are briefly reviewed. This includes an analysis and comparison of advantages and challenges of the power take off systems. Aspects of current international research and development activities and networks for wave energy is also discussed. The current market of wave energy technologies is also assessed, showing that the mechanical direct drive system is the most popular. Hybrid PTO systems are seen as an important development for the future.

The dynamic performance of the wave energy converter (WEC) rotor with different geometric parameters such as depth of submergence and beak angle has been assessed by considering the linear potential flow theory using WAMIT solver and along with the computational fluid dynamics (CFD). The effect of viscous damping is incorporated by conducting numerical free decay test using CFD. The hydrodynamic coefficients obtained from the WAMIT, viscous damping from the CFD and estimated PTO damping are used to solve the equation of motion to obtain the final pitch response, mean optimal power and capture width. The viscous damping is almost 0.9 to 4.6 times when compared to the actual damping. It is observed that by neglecting the viscous damping the pitch response and power are overestimated when compared to the without viscous damping. The performance of the pitch WEC rotor in the Jeju western coast at the Chagwido is analyzed using Joint North Sea Wave Project (JONSWAP) spectrum and square-root of average extracted power is obtained. The performance of WEC rotor with depth of submergence 2.8 m and beak angle 60° found to be good compared to the other rotors.

This study presents the results of the Fuzzy Logic based control application for a heaving wave energyconverter operating in realistic sea-state conditions. It has been shown in literature that the powercapture performance of a heaving wave energy converter depends on meeting the resonance conditionwith the incident wave frequency. In regular sea wave conditions, the task of setting the control pa-rameters is a well-known easy task where the wave frequency is known. However, in irregular seaconditions, the wave frequency needed for control settings is not clearly defined. One of the approachesproposed in literature is to use of the dominant wave frequency that can be estimated by a model usingthe Discrete Fourier Transform approach. The presented model utilises the estimated wave frequency inFuzzy Logic controller for determination of Power Take-Off control settings. This approach combineswidely used fast tuning technique with a new slow tuning method. As a part of the study, the developedrealistic simulation model and proposed Fuzzy Logic based controller are used to combine the fast andslow tuning techniques to form a novel hybrid control technique. The simulation results for this newcontrol technique in realistic sea conditions are presented.

In this paper, a novel robust model predictive controller (R-MPC) for wave energy converters (WECs) is proposed. The controller combines a constrained function-based predictive controller that is responsible for ensuring maximum power extraction and a local model that compensates for system parametric uncertainties and model mismatches. Laguerre polynomials have been deployed to alleviate the computational burden usually associated with the standard MPC techniques. The computer simulation results show that the R-MPC strategy has produced satisfactory and computationally efficient performance with respect to maximizing the captured power, increasing the power conversion efficiency, and enhancing the power take-off (PTO) utilization.

Control design is of central importance in the optimization of power generation from ocean wave energy converters (WECs). The problem is made challenging by the fact that the resource is vibratory and stochastic, with a low quality factor. It has recently been shown that when constrained to causality, the optimal feedback controller for a WEC is solvable in closed-form as a sign-indefinite LQG problem, for the case in which the WEC exhibits linear dynamics and quadratic power transmission dissipation. However, most WECs exhibit stroke limits, which must be explicitly accounted for in control design to avoid end-stop collisions. This is important because such collisions lead to damage, and also because the introduction of unmodeled stroke limits can actually destabilize the otherwise-optimal closed loop. We illustrate a control design technique to address this issue, which consists of two design steps. In the first step, LMI techniques are used to optimize the mean power harvested from waves with a known power spectral density, subject to several competing objectives. In the second step, the controller is augmented via a nonlinear passivity-based outer-loop design which guarantees to prevent stroke saturation while also guaranteeing to preserve closed-loop stability. The technique is illustrated using a model of a simple heaving point absorber, and verified in simulation.

In this paper, a point absorber wave energy converter combined with offshore wind turbine is proposed. In the system, the wave energy is captured and converted into hydraulic energy by a piston pump module, which is combined with a wind turbine floating platform, and then the hydraulic energy is converted into electricity energy by a variable displacement hydraulic motor and induction generator. In order to smooth and stabilize the captured wave energy, a hydraulic accumulator is applied to store and release the excess energy. In order to meet the demand power a fuzzy controller is designed to adjust the displacement of hydraulic motor and controlled the output power. Simulation under irregular wave condition has been carried out to verify the validity of the mathematical model and the effectiveness of the controller strategy. The results show that the wave energy converter system could deliver the required electricity power precisely as the motor output torque is controlled. The accumulator could damp out all the fluctuations in output power, so the wave energy would become a dispatchable power source.

Recent research has shown that when constrained to causality, the optimal feedback controller for an ocean wave energy converter (WEC) subjected to stochastic waves can be solved as a non-standard Linear Quadratic-Gaussian (LQG) optimal control problem. In this paper, we present a relaxation to the modeling assumptions that must be made to apply this theory. Specifically, we propose a technique that uses the principle of Gaussian Closure to accommodate nonlinear WEC dynamics in the synthesis of the optimal feedback law. The technique is approximate, in the sense that it arrives at a computationally efficient control synthesis technique through a Gaussian approximation of the stationary stochastic response of the system. This approach allows for a wide range of nonlinear dynamical models to be considered, and also accommodates many complex loss mechanisms in the power transmission system. The technique is demonstrated through simulation examples pertaining to a flap-type WEC with a hydraulic power train.

This study investigates the performance of a piston-type porous wave energy converter (PTPWEC), which consists of a solid wall, a vertical porous plate, a transmission bar, a rigid block constrained by rollers, a spring, and a damper. The PTPWEC is subjected to dynamic external loading by wave actions. To simulate this dynamic system, a mathematical model is used with a single-degree-of- freedom (SDOF) system. Linear wave theory governs the entire fluid domain, which is divided into two regions by the vertical porous plate. Darcy's law is applied to flow through the porous plate. Finally, this investigation employs an eigenfunction expansion to yield a solution. A series of numerical experiments are conducted to determine the hydrodynamic added mass, radiation damping, converter response, and instantaneous mechanical power obtained from the wave.

A new type of efficient wave energy converter, based upon resonant absorption of wave energy, is presented. The resonant frequency of such a device is at all times tuned to the frequency of the wave. This may be realized by incorporating into the oscillating system aa flywheel with adjustable inertial moment. Further, the mechanical load resistance of the device is adjusted to an optimum value, which is equal to the radiation resistance in sinusoidal waves. In wind-generated waves, however, the load resistance should be somewhat larger than the radiation resistance. An analysed example shows that a single, semi-submerged, properly designed tank of diameter 16 m, placed in waves typical of the North Atlantic may produce a useful energy amount of the order of 107 kWh per year. (A)

The potential of electric power generation from marine renewable energy is enormous. Ocean waves are being recognized as a resource to be exploited for the sustainable generation of electrical power. The high load factors resulting from the fluid properties and the predictable resource characteristics make ocean waves particularly attractive for power generation and advantageous when compared to other renewable energies. Regarding this emerging and promising area of research, this paper presents a complete review of wave energy technologies describing, analyzing and fixing many of the concepts behind wave energy conversion. The proposed review will specifically highlights the main wave energy conversion projects around the world at different levels (demonstration stage, in production, and commercialized projects). In particular, mooring will be discussed, as it is a key feature behind massive deployment of wave energy converters. Finally, a discussion will highlight challenges that wave energy converters need to overcome to become commercially competitive in the global energy market.

This review paper summarized the fundamental of triboelectric nanogenerators for generating electrical signals from mechanical agitations, which is the basis of serving as self-powered active sensors.•This review paper summarized the updated research progress of triboelectric-nanogenerator-based self-powered active sensors for different types of mechanical motions, including pressure change, touch, vibration, linear displacement, rotation, tracking of moving objects, as well as some examples of practical applications.•This review paper summarized the updated research progress of triboelectric-nanogenerator-based self-powered active sensors for chemical detection and environmental monitoring.•This review paper gave an insightful perspective for the future research on the triboelectric-nanogenerator-based self-powered active sensors.

Triboelectrification is one of the most common effects in our daily life, but it is usually taken as a negative effect with very limited positive applications. Here, we invented a triboelectric nanogenerator (TENG) based on organic materials that is used to convert mechanical energy into electricity. The TENG is based on the conjunction of triboelectrification and electrostatic induction, and it utilizes the most common materials available in our daily life, such as papers, fabrics, PTFE, PDMS, Al, PVC etc. In this short review, we first introduce the four most fundamental modes of TENG, based which a range of applications have been demonstrated. The area power density reaches 1200 W/m2, volume density reaches 490 kW/m3, and an energy conversion efficiency of ~50-85% has been demonstrated. The TENG can be applied to harvest all kinds of mechanical energy that is available in our daily life, such as human motion, walking, vibration, mechanical triggering, rotation energy, wind, moving automobile, flowing water, rain drop, tide and ocean waves. Therefore, it is a new paradigm for energy harvesting. Furthermore, TENG can be a sensor that directly converts a mechanical triggering into a self-generated electric signal for detection of motion, vibration, mechanical stimuli, physical touching, and biological movement. After a summary of TENG for micro-scale energy harvesting, mega-scale energy harvesting, and self-powered systems, we will present a set of questions that need to be discussed and explored for TENG’s applications. Lastly, since the energy conversion efficiencies for each mode can be different although the materials are the same, depending on the triggering conditions and design geometry. But one common factor that determines the performance of all the TENGs is the charge density on the two surfaces, the saturation value of which may independent of the triggering configurations of the TENG. Therefore, the triboelectric charge density or the relative charge density in reference to a standard material (such as polytetrafluoroethylene (PTFE)), can be taken as a measuring matrix for characterizing the performance of the material for the TENG.

The wave energy is having more and more interest and support as a promising renewable resource to replace part of the energy supply, although it is still immature compared to other renewable technologies. This work presents a complete analysis of the wave energy technology, starting with the characterisation of this global resource in which the most suitable places to be exploited are showed, and the classification of the different types of wave energy converters in according to several features. It is also described in detail each of the stages that are part in the energy conversion, that is, from the capture of the energy from the waves to the extraction of a proper electrical signal to be injected to the grid. Likewise, existing offshore energy transmission alternatives and possible layouts are described.
Keywords
Wave energy;
Wave power;
Wave energy converter;
Power electronics;
Power transmission

Triboelectrification is an effect that is known to each and every one probably ever since the ancient Greek time, but it is usually taken as a negative effect and is avoided in many technologies. We have recently invented a triboelectric nanogenerator (TENG) that is used to convert mechanical energy into electricity by a conjunction of triboelectrification and electrostatic induction. As for this power generation unit, in the inner circuit, a potential is created by the triboelectric effect due to the charge transfer between two thin organic/inorganic films that exhibit opposite tribo-polarity; in the outer circuit, electrons are driven to flow between two electrodes attached on the back sides of the films in order to balance the potential. Since the most useful materials for TENG are organic, it is also named organic nanogenerator, which is the first of using organic materials for harvesting mechanical energy. In this paper, we review the fundamentals of the TENG in the three basic operation modes: vertical contact-separation mode, in-plane sliding mode, and single-electrode mode. Ever since the first report of the TENG in January 2012, the output power density of TENG has been improved for five orders of magnitude within 12 months. The area power density reaches 313 W/m2, volume density reaches 490 kW/m3, and a conversion efficiency of ~60% has been demonstrated. The TENG can be applied to harvest all kind mechanical energy that is available but wasted in our daily life, such as human motion, walking, vibration, mechanical triggering, rotating tire, wind, flowing water and more. Alternatively, TENG can also be used as a self-powered sensor for actively detecting the static and dynamic processes arising from mechanical agitation using the voltage and current output signals of the TENG, respectively, with potential applications for touch pad and smart skin technologies. To enhance the performance of the TENG, besides the vast choices of materials in the triboelectric series, from polymer to metal and to fabric, the morphologies of their surfaces can be modified by physical techniques with the creation of pyramids-, square- or hemisphere-based micro- or nano-patterns, which are effective for enhancing the contact area and possibly the triboelectrification. The surfaces of the materials can be functionalized chemically using various molecules, nanotubes, nanowires or nanoparticles, in order to enhance the triboelectrific effect. The contact materials can be composites, such as embedding nanoparticles in polymer matrix, which may change not only the surface electrification, but also the permittivity of the materials so that they can be effective for electrostatic induction. Therefore, there are numerous ways for enhancing the performance of the TENG from the materials point of view. This gives an excellent opportunity for chemists and materials scientists to do extensive study both in the basic science and in practical applications. We anticipate that a much more enhancement of the output power density will be achieved in the next few years. The TENG is possible not only for self-powered portable electronics, but also as a new energy technology with a potential of contributing to the world energy in the near future.

This paper concerns the design of feedback control systems to maximize power generation of a wave energy converter (WEC) in a random sea. In the literature on WEC control, most of the proposed feedback controllers fall into three categories. Many are static; i.e., they extract power by imposing an equivalent damping or resistive load on the power take-off (PTO) devices. Others are dynamic and are designed to maximize power generation at all frequencies, which results in an anticausal feedback law. Other dynamic control design methods are causal, and are tuned to achieve the anticausal performance at only a single frequency. By contrast, this paper illustrates that the determination of the true optimal causal dynamic controller for a WEC can be found as the solution to a nonstandard linear quadratic Gaussian (LQG) optimal control problem. The theory assumes that the control system must make power generation decisions based only on present and past measurements of the generator voltages and/or velocities. It is shown that unlike optimal anticausal control, optimal causal control requires knowledge of the stationary spectral characteristics of the random sea state. Additionally, it is shown that the efficiency of the generator factors into the feedback synthesis. The theory is illustrated on a linear dynamical model for a buoy-type WEC with significant resonant modes in surge and pitch, and equipped with three spatially-distributed generators.

The economic viability of a wave energy converter depends largely on its power take-off system. Active control of the power take-off is necessary to maximise power capture across a range of sea-states and can also improve survivability. The high force, low speed regime of wave energy conversion makes it a suitable application for high-pressure hydraulics.This paper describes the hydraulic power take-off system employed in the Pelamis wave energy converter. The process of the system's development is presented, including simulation and laboratory tests at 1/7th and fullscale. Results of efficiency measurements are also presented.

This paper investigates semi-analytically the latching control applied to a mechanical oscillator; and numerically three strategies of latching control for a point absorber wave energy converter oscillating in the heave mode only. By solving the equation of motion of a mechanical damped oscillator, it is shown that latching control can magnify the amplitude of the motion whatever the frequency of the excitation force, and how it can improve the efficiency of the system, in term of absorbed energy, for excitation frequencies apart from the natural frequency. Assuming that the excitation force is known in the close future and that the body is locked in position at the current time step, equations of motion of the body are solved numerically in the time domain for different initial conditions (i.e. latching durations). For all these simulations, three criteria—one for each strategy—are tested and the latching time leading to the best result is selected. Time domain simulation results are presented for a heaving buoy in small-amplitude regular and random waves. In regular waves, the same results as for the case of a mechanical oscillator are recovered for the wave energy converter. In random sea, results show that for all the three proposed strategies, efficiency of the wave energy converter is considerably improved in terms of absorbed energy. Numerical study of the period of the controlled system shows that the delay of prediction of the excitation force in the future seems to be bounded by the natural period of the system.