Wave Energy Power Research Articles

A Comparative Analysis of Self‐Rectifying Turbines for the Mutriku Oscillating Water Column Energy Plant

Oscillating Water Column (OWC) based devices are arising as one of the most promising technologies for wave energy harnessing. However, the most widely used turbine comprising its power take‐off (PTO) module, the Wells turbine, presents some drawbacks that require special attention. Notwithstanding different control strategies are being followed to overcome these issues; the use of other self‐rectifying turbines could directly achieve this goal at the expense of some extra construction, maintenance, and operation costs. However, these newly developed turbines in turn show diverse behaviours that should be compared for each case. This paper aims to analyse this comparison for the Mutriku wave energy power plant.

An overview of the Brazilian continental shelf wave energy potential

Wave energy studies have received high attention in the last few years due the increasing exploitation of alternative energies, as a result of the urgency in reducing the consumption of fossil fuels. However, a characterization of this resource has extreme importance due its elevated temporal and spatial variability. Parallel to this development on the renewable energy field, there is a wide range of studies of Wave Energy Converters (WEC’s) which has brought with them a number of important analysis that contribute to the development of these technologies. The viability of the implementation of wave energy farms highly depends on the wave energy power of the intended location. In this way, this study explores the evaluation and characterization of the wave energy potential on the Brazilian coast. Numerical simulations were carried out in order to determine, amongst other factors, Significant Wave Height (Hs) and Wave Power Rate (Pw), of the studied region. The two-dimensional spectral model TOMAWAC was used to conduct the simulations, which were calibrated and validated using wave data measured by buoys along the Brazilian coast. The surface boundary was forced using wind velocity data, and the oceanic boundaries were forced by Hs, Peak Period (Tp), and Peak Direction (Dp) data, both provided by Era-Interim project. A 5 year wave hindcast was developed, and the annual averages were analyzed in different locations over all the Brazilian continental shelf, aiming to explore the potential implementation of WEC farms. In near shore areas the mean Pw reached values of 15 kW m−1, while offshore values reached from 18 to 20 kW m−1 being most frequent in the South-Southeastern Brazilian Shelf (SSBS). A great variability of the wave power was also identified when comparing the SSBS and the North-Northeastern Brazilian Shelf (NNBS), which demonstrate that the Pw tends to increase at higher latitudes. The results of this study could be used to seek specific areas which demonstrate available wave power for conversion in electric power.

Stochastic risk-sensitive market integration for renewable energy: Application to ocean wave power plants

With the expected increase of intermittent renewable energy resources on the electric power grid, short-term reserve markets can prove to be a critical reliability asset. This paper introduces and tests a potential market structure that includes a short-term reserve market for renewable resources where the realized energy is drawn within the bounds of the hourly capacity offered. The study presents a risk-aware stochastic model that determines, based on the day-ahead offer derived using a classic newsvendor formula, the best intraday offers for a renewable energy power plant. The stochastic approach takes into account the uncertainties of energy production and market prices. The proposed risk-sensitive model aims to maximize the renewable power plant’s revenues and minimize potential risks of loss in a multi-product multi-timescale market setup. To demonstrate the effectiveness of the proposed formulation, we study the case of a hypothetical 750-kW wave power plant coupled with energy storage. The study shows that the risk of profit loss is not uniformly distributed across the risk-aversion factor space. We also find that the introduction of the short-term reserve market results in a wider range of conditional value at risk while inducing 5% profit increase and a lower profit reduction across the risk range. In addition, the study reveals that the short-term reserve market is profitable for both the system operator and the wave energy power plant considered.

A Review of Wave Energy Extraction Technology

The current research on the utilization of wave energy has not formed a globally recognized technologically optimal wave energy power generation technology. The various types of wave energy power generation devices have different power generation principles and structural forms. Wave energy has the characteristics of wide distribution and high energy density, but it is also the most unstable type of ocean energy. Compared with other energy sources, wave energy has the characteristics of high energy density, and it is technically easy to realize the miniaturization of equipment, which contributes to the development of ocean resources. This article will mainly introduce current mainstream wave energy technologies, and explore their working principles and analyse their development trends.

Mejora de la Potencia Obtenida en Plantas de Generación Undimotriz basadas en Columna de Agua Oscilante

<div data-canvas-width="1023.1990468800007">Las centrales de aprovechamiento de la energía proveniente de las olas, y particularmente los dispositivos de columna de agua oscilante, resultan una alternativa factible para reducir la dependencia de los combustibles fósiles y frenar el creciente problema del calentamiento global. Así, los nuevos esquemas de control pueden jugar un papel importante a la hora de aportar mejoras de rendimiento y competir de igual a igual desde un punto de vista comercial con las fuentes de energía tradicionales. En este sentido, el presente artículo propone un nuevo método de control basado en el seguimiento de la curva de máxima potencia, mediante el establecimiento de los valores óptimos de los coeficientes de flujo y de par que permiten maximizar la potencia generada en cada instante. El esquema de control ha sido implementado sobre un modelo completo desde la ola hasta la red de potencia a fin de demostrar la viabilidad del método propuesto y la bondad de sus resultados.</div>

Variable speed control in wells turbine-based oscillating water column devices: optimum rotational speed

The effects of climate change and global warming reveal the need to find alternative sources of clean energy. In this sense, wave energy power plants, and in particular Oscillating Water Column (OWC) devices, offer a huge potential of energy harnessing. Nevertheless, the conversion systems have not reached a commercially mature stage yet so as to compete with conventional power plants. At this point, the use of new control methods over the existing technology arises as a doable way to improve the efficiency of the system. Due to the non-uniform response that the turbine shows to the rotational speed variation, the speed control of the turbo-generator may offer a feasible solution for efficiency improvement during the energy conversion. In this context, a novel speed control approach for OWC systems is presented in this paper, demonstrating its goodness and affording promising results when particularized to the Mutriku’s wave power plant.

Research on Efficiency of a Wave Energy Conversion System

The oceans are rich in wave energy that is green energy, and the wave energy are now being used to generate electricity on a massive scale. It can also be used as a single generator for beacon, buoy or underwater vehicle. Micro small wave energy power generation device is a kind of wave energy power generation devices, main characteristic is mobility is good, and can be directly assembled on various kinds of equipment for the power supply, with good prospects for development. The research object of the paper is a new adaptive reversing wave energy generating device belongs to micro-sized wave energy generating device. Using the upper and lower absorber blade groups, the low speed and large torque wave energy can be converted into electric energy which can be used for load and lithium battery charging.

Fast Energy Storage Systems Comparison in Terms of Energy Efficiency for a Specific Application

One of the key parameters to properly and accurately assess an energy storage system is the energy efficiency, which has a direct impact on the system performance and an indirect impact in its cost. In this paper, a methodology for comparing double-layer capacitors (EDLC) and kinetic energy storage systems (KESS) in terms of energy efficiency is proposed. This methodology, based on accurate loss models, takes real operating cycles into account, so a realistic result is obtained for each particular case. An accurate study of the losses of both technologies is accomplished during the paper, getting a complete model for EDLCs and KESSs, and obtaining efficiency maps for the whole range of operation points. Some conclusions about the convenience to use one or the other alternative and the best way to operate them are presented. In addition, a specific study case related to a wave energy power generation plant has been carried out in this paper, defining a methodology to select the energy storage requirements, calculating the round-trip efficiency and getting some recommendations related to the most appropriate operation strategy to take the most advantage of the energy storage system.

Application of metaheuristic algorithm to identify priority parameters for the selection of feasible location having optimum wave energy potential

The advances in technology and demand for luxury have induced increase in energy demand. However, the conventional energy resources due to its cost and impact on environment are becoming infeasible solution to satisfy the demand. As a result, alternative sources of energy such as solar, hydro, and sustainable energy resources are used to substitute the fossil fuels and satisfy the marginal demand for energy. Wave energy has a potential to satisfy the present energy demand. However, the expensive conversion procedures are one of the major deterrents which presented wider utilization of the resource. One of the reasons of costly conversion procedure is subjective- and experience-based selection of location and infeasible selection of parameters to identify a location from where maximum resources can be utilized under maximum expenditure. That is why, selection features by objective and unbiased method can reduce the cost of conversion and maximize the resource utilization. In this aspect, a new concept of “optimization techniques as multicriteria decision-making” was used to identify the major features in an objective and unbiased manner and compared with the results from analytical hierarchy process multicriteria decision-making method technique. While comparing the significance of the parameters wind speed, wave height, wind duration, water depth, fetch, and marine engineer, academicians and stakeholder criteria were used. The most significant parameters were evaluated with respect to the optimal as well as uncertain scenarios. The result shows that wind speed is the most significant parameter under normal and positive extreme scenario, respectively. The wind speed, water depth, and wave height are the most significant parameters with respect to optimization techniques such as differential evolution and genetic algorithms criteria for this normal and for the uncertain scenario. The index also provided a heuristic and cognitive optimal value to way from a suitability of utilization efficiency of wave energy power. Both models were able to fit the data well, with R2 values of 0.99127 and 0.97964 for the linear regression model and the polynomial neural network model, respectively. It was also found that the test data set had a mean absolute error of 0.07742 for the polynomial neural network model, while it was 0.06987 for the regression model.

A comparative analysis of wave power in the nearshore by WAM estimates and in-situ (AWAC) measurements. The case study of Varkiza, Athens, Greece

The wave energy potential in the Mediterranean has been estimated using numerical models. However, the veracity of these estimates in the nearshore, where wave energy harnessing is likely to take place, remains largely unknown. This paper compares measured wave data (AWAC/ADCP) with estimates of the third-generation spectral WAve Model (WAM), in Varkiza, Athens, a typical south facing nearshore Greek locale. Overall, good agreement in the mean wave power (Pmean) was found, but WAM overestimated the peak Pmax and had an overall error of ∼19° when estimating the mean wave direction (Mdir). The results are suggestive that WAM could act as a screening tool to identify nearshore wave energy hotspots and avoid areas with extreme sea states. Nonetheless, in-situ wave measurements are required to determine the wave energy power potential and the direction of wave propagation so as to select the appropriate conversion technology that better fits local conditions. Finally, it is suggested that existing wave energy technology should be, redesigned, downscaled and optimized to suit the milder Mediterranean wave regime, thus enacting wave energy development in Greece.

Influence of installation deviation on dynamic performance of synchronous magnetic coupling

To improve dynamic characteristics of synchronous magnetic coupling, this paper mainly analyzed the influence of the installation deviation on the synchronous magnetic coupling’s dynamic performance used in the horizontal axis wave energy power generation device. Dynamic characteristics equations based on Lagrange equation are built in the paper to analyze the dynamic characteristic of synchronous magnetic coupling. The radial deviation, the angle deviation and the center-of-mass deviation are considered in the equation. The influence of those installation deviations on the synchronous magnetic coupling performance is analyzed based on the mathematical model. The results show that the rise time, the overshoot, the peak time, the adjusting time and the oscillation of the synchronous magnetic coupling are almost not affected by those installation deviations.

Towards a cost-based design of heaving point absorbers

The need for increasing the share of sea resources in the global renewable energy market requires a specialized design of wave energy converters and Power Take-Off units that, in turn, may be capable of maximising power production and minimizing extraction costs. In this respect, as optimization of wave energy converter performances, by properly tuning relevant hydrodynamic parameters and controlling the motion in waves, reveals a basic issue to reduce energy production charges, a new cost-based design procedure for heaving point absorber type devices is developed, with the main aim of accounting for wave climate at deployment site, reliable device operational profiles and design restraint criteria for both floating buoy and Power Take-Off unit. The newly proposed cost-based procedure is applied to detect the optimum configuration of heaving point absorber devices at several candidate deployment sites. Finally, the incidence of wave climate and available energy resources, on detecting the optimum device configuration and assessing relevant energy production costs, is investigated and fully discussed.

Pumped‐storage power generation system based on wave energy

Ocean wave energy is a new type of pollution-free renewable energy, and there are many kinds of wave energy utilising equipments designed recently. The magnitude of wave energy has the characteristics of time variation, so that the output of most wave power generation devices may not be directly integrated into the grid. In order to simplify the structure of the wave energy power generation system, reduce the design and manufacturing costs and improve the stability of the output to satisfy the grid-connection control requirements of wave energy power generation, a wave energy conversion device is designed, which is convenient to maintenance and replacement, and a pumped-storage power generation system based on this device is proposed. In this study, the design of wave energy pumped-storage power generation system is explained in detail. The working condition of the device under different sea conditions is simulated, and the operating characteristics and reasonable parameters of the system are deduced. Theoretical analysis and simulation results can provide theoretical basis for the design of wave energy pumped-storage power generation device and provide reference for engineering application.

Ocean Energy Comprehensive Utilization System of Water‐electricity Cogeneration

Ocean energy is one of the renewable energy sources. Ocean thermal energy is the most abundant in marine energy, so it has a good development prospect. At present, the main way to use ocean energy is power generation. However, it has disadvantages: low efficiency and high energy consumption. In view of the above shortcomings, this study puts forward a new type of ocean energy comprehensive utilisation system of water–electricity cogeneration. The system is based on the ocean thermal energy conversion: wave energy power generation and solar pond are integrated in the system. The basic principle and working process were analysed, and the energy consumption and the product of the system were calculated. As shown in the calculation results, it is effective to reduce energy consumption and improve the system efficiency. The research of this study has valuable reference for the development of ocean energy in the future.

Structural Design and Hydrodynamics Analysis of Wave Energy Converter for Falculty of Engineering, Rmu

Due to the continuous fluctuation of the prices of oil and the environmental impact on the economy, a renewable energy becomes debatable issue. The generation of electricity by harnessing the power of sea wave has been the most prominent research into renewable energy for over decades. Various researches have used various power take off mechanisms systems for converting wave power into electrical power such as the pelamis, oscillating water column, Archimedes wave swing etc. In this research, linear generator power take of method is used to convert the motion of wave at its interaction with the devices into electricity since this method offers a great power output at a minimum wave energy power than other methods. Feasibility studies to ascertain the exact location for mooring of the components were conducted using google search. The analysis of a hybrid quantitative and qualitative method is applied. In this aspect, statistical analysis of sea wave data and the consumption of electrical gadget of the faculty engineering of Regional Maritime University were analysed in order to design a suitable wave energy converter. Hydrodynamic analysis of wave energy converter was determined in order to establish the velocity of sea wave, for due to the incident wave, the energy from sea wave and the electrical power generated by the generator as a result of sea wave energy.

Impact of climate change on wave energy resource: The case of Menorca (Spain)

The aim of this paper was to analyse how changes in wave patterns, due to the effect of climate change, can affect wave energy power and yield around Menorca (NW Mediterranean Sea). The present and future wave energy conditions were derived from recently developed high-resolution wave projections in the NW Mediterranean. These wave projections were forced by surface wind fields obtained, respectively, by 5 different combinations of global and regional circulation models (GCMs and RCMs) for the A1B scenario. The results showed that the projected future spatial and directional distributions of wave energy are very similar to those of the present conditions. The multi-model ensemble average illustrated a slight general decrease in the annual and seasonal wave power (except for summer). However, the inter-model variability is large since two models showed opposite trends to the other 3 in most cases. Such inter-model variability is lower(higher) for winter(autumn). Another result is the reduction of the temporal variability in the future, considering both the multi-model mean and each single model projection. Such a decrease is consistent with the future seasonal redistribution of energy throughout the year. This would entail an increase in the efficiency of wave energy converters deployed in this area due to the more regular temporal distribution of the energy.

Experimental and Simulative Study on Accumulator Function in The Process of Wave Energy Conversion

Abstract In this paper, a floating-buoy wave energy converter using hydrostatic transmission system is studied. The entire work progress of wave energy power generation device is introduced, and the hydraulic transmission principles are emphasized through the simulation to verify the feasibility of design principle of hydraulic transmission system. The mathematical model of the accumulator is established and applied in the AMEsim simulation. The simulation results show that the accumulator plays an important role in the wave power hydraulic transmission system and that the correct configuration of accumulator parameters can improve the rapidity and stability of the system work. Experimental results are compared with the simulation results to validate the correctness of the simulation results. This would provide a valuable reference to the optimal design of wave power generation.

Wave power potential in Malaysian territorial waters

Up until today, Malaysia has used renewable energy technology such as biomass, solar and hydro energy for power generation and co-generation in palm oil industries and also for the generation of electricity, yet, we are still far behind other countries which have started to optimize waves for similar production. Wave power is a renewable energy (RE) transported by ocean waves. It is very eco-friendly and is easily reachable. This paper presents an assessment of wave power potential in Malaysian territorial waters including waters of Sabah and Sarawak. In this research, data from Malaysia Meteorology Department (MetMalaysia) is used and is supported by a satellite imaginary obtained from National Aeronautics and Space Administration (NASA) and Malaysia Remote Sensing Agency (ARSM) within the time range of the year 1992 until 2007. There were two types of analyses conducted which were mask analysis and comparative analysis. Mask analysis of a research area is the analysis conducted to filter restricted and sensitive areas. Meanwhile, comparative analysis is an analysis conducted to determine the most potential area for wave power generation. Four comparative analyses which have been carried out were wave power analysis, comparative analysis of wave energy power with the sea topography, hot-spot area analysis and comparative analysis of wave energy with the wind speed. These four analyses underwent clipping processes using Geographic Information System (GIS) to obtain the final result. At the end of this research, the most suitable area to develop a wave energy converter was found, which is in the waters of Terengganu and Sarawak. Besides that, it was concluded that the average potential energy that can be generated in Malaysian territorial waters is between 2.8kW/m to 8.6kW/m.

A Floating Ocean Energy Conversion Device and Numerical Study on Buoy Shape and Performance

Wave and current energy can be harnessed in the East China Sea and South China Sea; however, both areas are subject to high frequencies of typhoon events. To improve the safety of the ocean energy conversion device, a Floating Ocean Energy Conversion Device (FOECD) with a single mooring system is proposed, which can be towed to avoid severe ocean conditions or for regular maintenance. In this paper, the structure of the FOECD is introduced, and it includes a catamaran platform, an oscillating buoy part, a current turbine blade, hydraulic energy storage and an electrical generation part. The numerical study models the large catamaran platform as a single, large buoy, while the four floating buoys were modeled simply as small buoys. Theoretical models on wave energy power capture and efficiency were established. To improve the suitability of the buoy for use in the FOECD and its power harvesting capability, a numerical simulation of the four buoy geometries was undertaken. The shape profiles examined in this paper are cylindrical, turbinate (V-shaped and U-shaped cone with cylinder), and combined cylinder-hemisphere buoys. Simulation results reveal that the suitability of a turbinate buoy is the best of the four types. Further simulation models were carried out by adjusting the tip radius of the turbinate buoy. Three performance criteria including suitability, power harvesting capability and energy capture efficiency were analyzed. It reveals that the turbinate buoy has almost the same power harvesting capabilities and energy capture efficiency, while its suitability is far better than that of a cylindrical buoy.

Design and experimental research of jack-up wave energy power generation device

In order to solve the problem of energy shortage and focus on the development of wave energy, a jack-up platform is used as the carrier, and a new type of wave energy power generation device is designed. Compared with other power generation devices, this new type of jack-up wave energy power generation device owns the advantage of wind and wave resistance, is continuous, highly efficient, stable, and strongly adaptable. By means of combination of theoretical analysis and physical test, the feasibility of the device implementation of wave power is explored. The results showed that the jack-up wave energy power generation device can normally work in the sea state, which verified the feasibility of the device. This device has achieved wave power efficiency by more than 15% of the technical indicators of the project and the desired effect. In general, the jack-up wave energy power generation device has achieved breakthrough in many aspects, and the overall technology has reached the leading domestic level.