Ocean Wave Power Research Articles

Ocean wave measurement and wave energy calculation using overtopping power plant scheme

Indonesian seas have not been used as a source of electricity yet. One of the potential and abundant sources of energy from the sea is ocean waves. This study describes the measurement of the wave characteristics and calculates its spatial and temporal energy in Pari Island which can be utilized as electrical energy using overtopping ocean wave power plants scheme. The energy that can be harvested from ocean waves is calculated by wave energy converter using the Wave Dragon WEC. This converter is the terminator type. Sea waves on the Pari Island are classified as the smooth sea with 0.16-0.51 meters significant wave height and 2–4 seconds period. The calculated WEC can produce energy up to 28 Mega Joules and power up to 6 Mega Watts. Based on this calculation, Wave Dragon which is an overtopping WEC is able to meet the electricity needs on Pari Island with two options, The first one is using 35 units of WD 1 on the Pari Island Coast with a 500 m distance from the settlement, or the second one is using 6 units of WD 2 which is located in the northeast region of Pari Island waters with 18 Km distance from the settlement of Pari Island.

Doubling the efficiency of ocean wave power with doubly coiled-up acoustic metamaterial

Ocean wave is a potential renewable energy source with stability and abundance. However, its high initial investment requires high energy harvesting efficiency, limiting its application. In this research, the ocean wave is directly amplified by adopting the structure of the acoustic metamaterial. SHOWPAM—A System of High-efficiency Ocean Wave Power with Acoustic Metamaterial – is designed to achieve this amplification. The mathematical analogy between acoustic wave and water surface wave is found. Also, an effective physical property of the solid obstacle, such as a wall, as a medium of water surface wave is investigated. Coiling-up-space metamaterial structure is simplified to a six-variable system and optimized for maximum water surface wave amplitude using COMSOL Multiphysics. Then, SHOWPAM is constructed based on the simulation result, consisting of a central cavity, energy harvester, and optimized metamaterial on both sides of the cavity. A control model was identical to SHOWPAM but didn’t have metamaterial. Both models are tested in the wave generating pool, and power generation of each model was measured. SHOWPAM showed 225% average power compared to the control model, proving the capability of metamaterial structure to enhance ocean wave power.

A Flexible Chain Proposal for Winch-Based Point Absorbers

Ocean wave power is a promising renewable energy source. It has, however, been difficult to find a cost-effective solution to convert wave energy into electricity. The harsh marine environment and the fact that wave power is delivered with large forces at low speed make design of durable mechanical structures and efficient energy conversion challenging. The dimensioning forces strongly depend on the wave power concept, the wave energy converter (WEC) implementation, and the actual power take-off (PTO) system. A WEC with a winch as a power take-off system, i.e., a winch-based point absorber (WBPA), could potentially enable a low levelized cost of energy (LCOE) if a low-cost, durable and efficient winch that can deal with peak loads can be developed. A key challenge for realizing such a winch is to find a force transmitting solution that can deal with these peak loads and that can handle up to 80 million cycles during its life. In this article, we propose a design solution for a force transmitting chain with elastomer bearings connecting the links of the chain. With this solution no sliding is present, and the angular motion is realized as elastic shear deformations in the elastomer bearings when the chain is wound onto the winch drum. The elastomer bearings were designed for low shear stiffness and high compression stiffness, and the links were designed primarily to minimize the number of joints in the chain. Thereby, the maximum allowed relative angle between the links when rolled up over the drum should be as large as possible within practical limits. Finite element-based topological optimization was performed with the aim to increase the link strength to weight ratio. A test rig for a first proof of concept testing has been developed, and preliminary test results indicate that this chain concept with elastomer bearings can be a potential solution for a durable chain and should be analyzed and tested further for fatigue and sea operations.

Performance of Generator Pneumatic for Power Plant of Ocean Wave

Pneumatic mechanism has been used in the electrical fields, industrial fields, automotive fields, mechanical fields and so on. The principle of pneumatic work is up and down the piston due to the pressure happen in this system. This mechanism can be applied for ocean wave power generation by use wave water. In the previous study, pneumatic mechanism has been used for mini generator of wave power plant [1]. Component of generator for power plant of ocean wave consist on shaft, tube, magnet neodymium, buoys, lamp LED and wire. In this paper we will focus on the varying of dimensions and position of valve and number of buoys. The results show that position valve of tube piston with double exhaust valve can be work well to give output (Voltage) compare the single exhaust valve. The output of position of tube piston with double exhaust valve is 3.2 Volt with 5 buoys and 2 parallel tube piston.

A Dynamic Stochastic Hybrid Model to Represent Significant Wave Height and Wave Period for Marine Energy Representation

This paper presents a methodology to represent ocean wave power generation based on real data observation for significant wave height (SWH or H s ) and wave period (WP or T). This technique is based on a hybrid model, which considers Fourier series and stochastic differential equations, allowing a continuous time representation of the random changes in the parameters associated with wave power generation ( H s and T). The methodology is explained, including estimation methods and a validation procedure. The data series generated by the models erre used to create simulated wave power output applying a transformed matrix and a theoretical model. The results validate the utilization of this technique, when the objective is to obtain a robust dynamic representation of a random process, oriented to linear studies.

The renewable wave energy resource in coastal regions of the Florida peninsula

Recently there has been a global effort to increase the utilization of renewable energy resources. In this study, we use observed data to estimate the ocean wave power available in coastal Florida. We find that average values ranging from 2.073 to 6.939 kW/m are available annually. It is shown that these values vary spatially; regions in the Atlantic Ocean have more available wave power than those in the Gulf of Mexico. Average annual wave power also varies temporally, likely due to meteorological events, indicating that changes in the climate may have significant impacts on available wave power.Available wave power is estimated using a spectral wave power equation, which requires sparsely available spectral wave density data. Wave power is more commonly estimated using a standard wave equation, which simplifies the required parameters to wave heights and wave periods. Here, we use both equations in order to assess the impact of this simplification. We find that the estimated wave power values calculated using the two equations differ considerably; using the simplified equation underestimates available wave power by an average of 17%. The degree of underestimation varies spatially, thus we recommend using the spectral wave power equation for ocean wave power assessment whenever possible.

Simulated Analysis and Review of Ocean Wave Power Generators

With the exponential rise in human population, the need for energy is becoming a real challenge to many countries around the world. Shortages in fossil sources of energy and its rising prices are beginning to cause many socio-economic problems and unrest in many parts of the world. This brings the need and importance of finding alternative and reliable sources of power. In recent years, the power of ocean waves began to attract attention. In this article, a design of the Wave Power Generator device is presented. This design is introduced to improve the efficiency. The proposed design is compared with an existing device that exploits the sea waves, converting the its energy to electrical power. This study aims to show that the instrument would achieve a higher efficiency by generating a greater total of electricity with the appropriate design and focus. The study is simulated using MATLAB. Results of the study show the electricity energy generated improved up to 80% in contrast to the present instrument. The results of this work could lead the way towards more active implementations of wave power generators and the use of sustainable energy resources.

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.

Improving low-frequency piezoelectric energy harvesting performance with novel X-structured harvesters

Vibration energy harvesting systems via an X-structure coupled with piezoelectric patches of special arrangements are investigated in this study. Two piezoelectric harvesters are specially installed on the X-shaped structure to explore potential benefits that the X-shaped structure could provide, and each piezoelectric pad has two layers composed of a polyvinyl chloride base patch and a micro-fibre composite patch. The theoretical analysis and experiment results indicate that the energy harvesting performance of the proposed novel arrangements of the piezoelectric harvesters can be enhanced especially in low-frequency range (below 10 Hz), compared with conventional cantilevered piezoelectric harvesters. More and higher energy harvesting peaks can be created and the effective harvesting frequency band can be obviously enlarged by expanding it to low-frequency range with the proposed methods. The X-structure-based generators can enable piezoelectric materials to harvest power from low-frequency vibration sources due to its advantages in designable equivalent nonlinear stiffness, which can be easily tuned by adjusting the key structural parameters. The design and results would provide an innovative solution and insight for smart piezoelectric materials to improve the energy harvesting efficiency in the low-frequency range including small-scale ocean wave power harvesting, human motion power and animal kinetic power harvesting, etc.

Flexible multibody dynamics modelling of point-absorber wave energy converters

Abstract As an inexhaustible and environmentally-friendly energy resource, ocean wave power, which is extracted from ocean waves through WECs (wave energy converters), is highly valued by coastal countries. Compared to other types of WECs, point-absorber WECs, the main body of which can be fixed on a platform (e.g. ship), save on installation costs and therefore have concentrated significant interest among researchers and technology developers. In the development of point-absorber WECs, it is crucial to develop a reliable structural model to accurately predict the structural dynamic responses of WECs subjected to wave loadings. In this work, a FMBD (flexible multibody dynamics) model, which is a combination of MBD (multibody dynamics) and FEA (finite element analysis), has been developed for point-absorber WECs. The FMBD model has been applied to the structural modelling of the NOTC (National Ocean Technology Centre) 10 kW multiple-point-absorber WEC. The floater arm tip displacement and velocity obtained from the FMBD model are validated against the values obtained from an analytical model, which is also developed in this work. The results from the FMBD model show reasonable agreement with those from the analytical model, with a relative difference of 10.1% at the maximum value of the floater arm tip displacement. The FMBD model is further used to calculate the stress distributions, fatigue life, deformations, modal frequencies and modal shapes of the structure. The results indicate that WECs are prone to experience fatigue failure, with the shortest fatigue life (2 years) observed in the floater arm. The FMBD model developed in this work is demonstrated to be capable of accurately modelling point-absorber WECs, providing valuable information for designers to further optimise the structure and assess the reliability of WECs.

Towards innovative district energy management: a case study with stochastic renewable generators

The conversion of ocean wave power into sustainable electrical power represents a major opportunity to Nations endowed with such a kind of resource. At the present time the most of the technological innovations aiming at converting such resources are at early stage of development, with only a handful of devices close to be at the commercial demonstration stage. The Seaspoon device, thought as a large energy harvester, catches the kinetic energy of ocean waves with promising conversion efficiency, and robust technology, according to specific “wave-motion climate†. University of Genoa developed and patented a prototype to be deployed in medium average energy content seas (i.e. Mediterranean or Eastern Asia seas). This paper presents the installation phases of the first real scale prototype installed in the gulf of Genova and the monitoring of its performances. A brief description of the Seaspoon WEC is presented together with the monitoring equipment and procedures.In this research a thermoeconomic analysis of its integration in a real polygenerative district is also investigated. The impact of such this kind of stochastic renewable generator in the Savona Campus Smart Polygeneration Microgrid (SPM) is evaluated. The SPM plant is made up by (i) two auxiliary boilers (500kWth each), (ii) four micro gas turbines (30kWe, 2x65kWe and 100kWe), (iii) an internal combustion engine fed by natural gas (20kWe), (iv) an absorption chiller (100 kWf) and (v) PV panels for a total power installed of 100 kWe. Generators are “distributed†around the campus and they are coupled to electrical and thermal storages. Since the system is constituted by co-generative prime movers it can supply both electrical and thermal energy of the campus and the integration of storage is really important in order to follow both the requests, pursuing the best management strategy. The analysis of this smart-grid is performed exploiting a software developed by the Author's research group, which allows for the thermo-economic optimization of poly-generative energy systems. A model of the real plant was built and it was implemented in the software. The off-design curves of the real devices installed in the campus were used in order to increase the reliability of the simulation results. The grid was simulated considering the time dependent nature of the demands throughout the whole year. The model was used to simulate the smart grid behavior during the whole year, and find the best operational strategy. A time-dependent thermo-economic hierarchical approach has been used, considering the time-dependent electrical, thermal and cooling load demands during the year as problem constraints. The results are presented and discussed in depth and show the strong interaction between fossil and renewable resources, particularly the impact of unpredictable and randomized generators like the WECs ones. A dedicated model of the Seaspoon was implemented and exploited in the code.

Cross Spectral Analysis of CODAR-SeaSonde Echoes from Sea Surface and Ionosphere at Taiwan

It is well known that the primary targets responsible for first-order sea echoes observed by a High-Frequency (HF) radar are the advancing and receding ocean waves with the wavelengths at Bragg scales. However, in light of the fact that the ionospheric sporadic E (Es) and F layers may be present in the viewing range of the HF radar for ocean wave detection, the radar returns reflected from the F and Es layers may significantly contaminate the ocean wave power spectrum. The characteristics of the first-order sea echoes and ionospheric interferences measured by the CODAR-SeaSonde in Taiwan area are analyzed and presented in this article. The coherences and phases of the normalized cross spectra of the sea and ionospheric echoes between different pairs of the receiving channels are calculated, respectively. One of the striking features presented in this report is that the ionospheric echo heights scaled from the ionogram observed by the Chung-Li ionosonde are about 30 km lower than those observed by the DATAN CODAR-SeaSonde. It is also found that the coherences of the sea echoes are generally smaller than those of the ionospheric echoes by about 15% on average, and the phase fluctuations (standard deviations) of the sea echoes are substantially larger than those of the ionospheric layer reflection echoes. In addition, statistics show that the sum of the mean phases of the ionospheric echoes between the three receiving channel pairs is approximately zero, while it is not for the sea echoes. These results seem to suggest that the use of the discrepancies in the characteristics of the coherences and phases between the sea and ionospheric echoes may provide a potential means to be helpful to distinguish the sea and ionospheric echoes in the CODAR-SeaSonde observed cross power spectrum.

Optimization of Spacing for Oscillating Wave Surge Converter Arrays Using Genetic Algorithm

AbstractThe oscillating wave surge converter (OWSC) is a type of ocean wave power device typically consisting of a flap, or arm, hinged at the bottom to allow forward and backward movement by surging waves, and is efficient in generating electricity from waves due to its capability in operating at a wide range of wave spectra. The power generated from the OWSC could be further maximized by arranging the devices in an array at their optimal spacing. This paper addresses the optimization of device configuration within an array by using the genetic algorithm (GA) scheme, for which the spacings between devices are taken as the optimization variables, and the maximum q-factor is chosen as the objective function. The q-factor is a performance assessment parameter that quantifies the average total power produced by an array compared to an individual device. Three array layouts—namely, the single-, double-, and triple-array, each comprising 12 OWSCs—were considered. The pitch response amplitude operator (RAO) of ...

A simplified method to estimate tidal current effects on the ocean wave power resource

Although ocean wave power can be significantly modified by tidal currents, resource assessments at wave energy sites generally ignore this effect, mainly due to the difficulties and high computational cost of developing coupled wave-tide models. Furthermore, validating the prediction of wave-current interaction effects in a coupled model is a challenging task, due to the paucity of observational data. Here, as an alternative to fully coupled numerical models, we present a simplified analytical method, based on linear wave theory, to estimate the influence of tidal currents on the wave power resource. The method estimates the resulting increase (or decrease) in wave height and wavelength for opposing (or following) currents, as well as quantifying the change in wave power. The method is validated by applying it to two energetic locations around the UK shelf – Pentland Firth and Bristol Channel – where wave/current interactions are significant, and for which field data are available. Results demonstrate a good accuracy of the simplified analytical approach, which can thus be used as an efficient tool for making rapid estimates of tidal effects on the wave power resource. Additionally, the method can be used to help better interpret numerical model results, as well as observational data.

Spinal Cord Injuries in Wave-Riding Sports: The Influence of Environmental and Sport-Specific Factors.

Spinal cord injury is a nonfatal, catastrophic consequence of wave-riding sports. With surfing at the core, a multitude of activities have evolved that attempt to harness the power of ocean waves. The unique qualities of each wave-riding sport, in combination with the environmental factors of the ocean, define the risk for potential injuries. As wave-riding sports have become more advanced, athletes continue to push physical barriers. Taller waves are attempted while incorporating aerial maneuvers, all without protective equipment.

Decadal variability of wave power production in the North-East Atlantic and North Sea for the M4 machine

We look at the variability of the power produced by the three-float M4 wave energy converter for locations in the North-East Atlantic and North Sea using the NORA10 hindcast data from 1958−2011. The aim is to investigate whether the produced power is also strongly affected by the climate variability (such as the North Atlantic Oscillations) in the winter, just as the ocean wave power resource as observed in previous studies. In this study, we demonstrate the use of proxy indices in combination with the climate indices to reconstruct a historic practical wave power climate from 1665−2005. We also conduct sensitivity studies to assess the changes in the practical wave power variability in response to perturbing the machine size, the power take-off coefficient, the response bandwidth and the power limit of the power take off. We find that the resultant temporal variation is still dominated by the climate variability. However, the overall variability important for power availability and energy supply economics is smaller than that of the ocean wave power resource because of the finite capture bandwidth of the M4 machine. The statistical methodology presented here is also potentially relevant to other wave energy converters in similar locations.

Advancing the Wave Energy Industry

An extremely abundant and promising source of energy exists in the world's oceans. Ocean energy exists in the forms of wave, tidal, marine currents, thermal (temperature gradient), and salinity. Among these forms, opportunities and benefits have been identified in the area of ocean wave energy extraction, i.e., using wave energy converters (WECs) to harness the motion of waves and converting that motion into electrical energy. Ocean wave power exhibits several advantageous characteristics including high power density, low variability, and excellent forecastability. The United States is estimated to have 260 TWh of potential wave energy off its coasts, which is approximately 6% of its annual electrical load (comparable to the current traditional hydro power contribution). Ocean waves have well-defined geographical attributes, where the wave power tends to be stronger on the western coasts of land masses and also stronger moving north and south away from the equator. This is due to the global wind cells, primarily the Westerlies, which tend to cause eastwardly moving waves.

A Novel Wind Power Micro-Generator Research on Dielectric Electro Active Polymer

Wind power is emerging as a particularly attractive form of renewable energy. The predomination of Dielectric Electric Active Polymer (DEAP) has been shown to operate in transforming mechanical strain energy to electrical energy as generator mode. Their characteristics make them potentially well suited for wind power takeoff systems. In this article, a novel DEAP micro generator is successfully developed about mechanical-electro energy conversion model. The proposed energy harvesting is based on capacity change induced by the mechanical strain. With the Mooney-Rivlin model, the theoretical modeling of energy harvesting cycle are analyzed. To verify the theoretical analysis, the prototype has been set up on the DEAP wind power micro-generator in this work. Many experiments were performed to verify the usability of the proposed DEAP generator method. These experimental investigations coincide with the energy conversion theory analytical model. The DEAPs have been proved to provide electrical energy with density as high as 1.5J.g-1.This value is much higher compared with the density of piezoelectric polymer (0.3J.g-1). The work will push forward the practical use of wave power for supplying general electrical needs, and supply theoretical foundation for potential applications such as ocean wave power.

Energy conversion of orbital motions in gravitational waves: Simulation and test of the Seaspoon wave energy converter

The conversion of ocean wave power into sustainable electrical power represents a major opportunity to Nations endowed with such a kind of resource. At the present time the most of the technological innovations aiming at converting such resources are at early stage of development, with only a handful of devices close to be at the commercial demonstration stage. The Seaspoon device, thought as a large energy harvester, catches the kinetic energy of ocean waves with promising conversion efficiency, and robust technology, according to specific “wave-motion climate”. University of Genoa aims to develop a prototype to be deployed in medium average energy content seas (i.e. Mediterranean or Eastern Asia seas). This paper presents the first simulation and experimental results carried out on a reduced scale proof-of-concept model tested in the laboratory wave flume.

Design, Modeling and Optimization of an Ocean Wave Power Generation Buoy

Abstract Ocean waves provide an abundant, clean, and renewable source of energy. Existing systems, typically hydraulic turbines powered by high-pressure fluids, are very large in size and costly. Additionally, they require large ocean waves in which to operate. This paper details the design, development, and laboratory prototype testing of a wave power generation system comprising a buoy that houses a set of mechanical devices and a permanent magnetic generator. The buoy, floating on the surface of the ocean, utilizes the vertical movement of ocean waves to pull on a chain anchored to the ocean floor. The linear motion is translated into rotation, which rotates a shaft to move armature coils within the generator to produce an electric current. The amount of energy generated increases with wave height and input frequency. The flywheel inertia, shaft rotation speed, and electrical load are optimized to provide maximize electricity production. The paper addresses the design, analysis, and implementation of mechanical and electrical systems, together with resistive load control, system optimization, and performance analysis. Both simulation and experimental results are provided and compared.