Ocean Energy Utilization Research Articles

RIME-CNN-BiLSTM: A novel optimized hybrid enhanced model for significant wave height prediction in the Gulf of Mexico

Accurate prediction of SWH in the ocean is critical to the development of ocean energy technologies. However, existing forecasting models have limitations in accuracy and reliability, which directly affect the efficiency of ocean energy utilization. To address this problem, this paper proposes a new ocean SWH prediction model, RIME-CNN-BiLSTM, for predicting 1, 6, 12, and 24 h SWH at three buoy observing stations in the Gulf of Mexico. The model combines the RIME algorithm, CNN, and BiLSTM to comprehensively capture multiple parameters that affect wave heights, such as sea breeze, waves, barometric pressure, and temperature. The parameters of the CNN-BiLSTM model are optimized by the RIME algorithm, which significantly improves the prediction accuracy and generalization ability. Compared with the traditional model, RIME-CNN-BiLSTM captures the nonlinear features more accurately, has better prediction ability for outliers, and shows stronger generalization performance in different sea areas of the Gulf of Mexico. In terms of predicting the wave height in the next 24 h, the improvements are 7.065%, 3.646% and 5.186%, respectively. The results show that the RIME-CNN-BiLSTM model performs well in all prediction time periods, significantly outperforms other benchmark models, and is able to accurately capture nonlinear features and effectively predict outliers.

Human Resource Competency Development to Support the Development of Blue Economy-Based Marine Energy

The utilization of ocean energy based on the blue economy has become a primary focus in efforts to achieve sustainability in the maritime sector. The development of this sector requires high-quality human resources to address complex challenges. Therefore, this research aims to identify the need for human resource competencies to support the development of ocean energy based on the blue economy. This study adopts a mixed-methods approach (qualitative and quantitative) with a survey of stakeholders in the ocean energy sector. The survey will be conducted to gather data on the competencies required by personnel in various fields such as technology services, management, and law. The collected data will be analyzed using factor analysis techniques to identify the most important competencies. The targeted outcome is to provide employees as future generations with additional knowledge insight into relevant blue economy aspects aligning with the needs and challenges they will face in the future. We hope that the results of this research will provide valuable information for those involved in human resource development in the ocean energy service sector. This information can be utilized to develop training and staff development programs tailored to the specific needs.

A vortex-induced vibration device based on MG-TENG and research of its application in ocean current energy harvesting

In recent years, with the extensive research on the application of triboelectric nanogenerators (TENGs) by scholars all over the world, the development of TENGs in harvesting and utilization of ocean energy has attracted more and more attention according to the advantages of TENGs in low-frequency energy harvesting. As a kind of ocean energy, the development and utilization of ocean current energy is of great significance to the diversification of energy sources, the promotion of sustainable energy development, the protection of ecological environment and the response to climate change. In this work, a novel device based on the combination of vortex-induced vibration (VIV) and multi-grating TENG (MG-TENG) is proposed for energy harvesting in low-speed ocean currents. The device consists of an up and down moving float driving the TENG to convert kinetic energy into electrical energy. The result shows that the system has a maximum average output power of nearly 20 μW under the condition of 8 grating TENG. This work demonstrates the ability of devices based on the combination of VIV and MG-TENG to drive low-power electronic components, demonstrating future applications for sensing, positioning, and more.

Research on Multi -mode Power Generation Devices based on Wave Energy

This paper mainly studies a multi-mode power generation device based on wave energy, which is mainly composed of power generation device, energy storage device, monitoring device, through the use of electromagnetic machinery, piezoelectric ceramics, hydraulic system in a variety of ways to generate electricity, and then the energy storage device stable output, is a kind of power generation system will be converted into electrical energy device, to achieve high efficiency conversion of wave energy. Each part of the project is innovative and practical, which has high application value in ocean power generation. Compared with some traditional power generation devices, this device uses a new type of energy, ocean wave energy, which is a pollution-free, clean and renewable new energy. Wave energy has high flow density, huge reserves and wide distribution, which is the main direction of the development of ocean energy utilization in the future. It will make positive contributions to Marine construction, economic development and infrastructure construction of countries and regions along the Belt and Road.

Design of Ocean Current Blade Turbine 100 kW using Hydrodynamics Simulation Approach

National electricity consumed continues to rise by up to 6.4 % per year, which are not comparable with the availability of fossil fuels as a primary energy coal-fired power plant in Indonesia. Utilization of ocean energy in particular flow energy has performed as one of the primary energy options. Tides are responsible for the renewable energy of ocean currents. Changes in flow velocity of ocean water due to the ups and downs of ocean water can be used as the primary energy to drive turbines and generate electricity. This study investigates the ocean current power plant in Indonesia that relates to the characteristics of the ocean current. The data used for this research belonged to R&D Center Marine Geology (PPPGL) from ocean current data in the Toyapakeh, Pantar, Larantuka, Molo, Boleng and Gam strait. This study looked at both the technical and socioeconomic aspects of the six locations mentioned above. Larantuka strait had the greatest potential for ocean currents in the strait. The turbine was designed using Computational Fluid Dynamics (CFD), with a capacity of 100 kW for the Horizontal Axis turbine. The findings demonstrated that the turbine design could produce electrical energy at low ocean current speeds (cut-in speed) of 0.3 m/s, and that the rotor power generated at ocean current speeds of 2.2 m/s approached the design capacity of 100 kW.

Sustainable Seawater Desalination and Energy Management: Mechanisms, Strategies, and the Way Forward.

Solar-driven desalination systems have been recognized as an effective technology to address the water crisis. Recently, evaporators prepared based on advanced manufacturing technologies have emerged as a promising tool in enhancing ocean energy utilization. In this review, we discussed the thermal conversion, energy flow, salt deposition mechanisms, and design strategies for solar-driven desalination systems, and explored how to improve the desalination performance and energy use efficiency of the systems through advanced manufacturing technologies. In future perspectives, we determined the feasibility of coupling solar-driven solar desalination systems with multi-stage energy utilization systems and emerging artificial intelligence technologies, for which conclusions are given and new directions for future desalination system development are envisioned. Finally, exciting opportunities and challenges in the face of basic research and practical implementation are discussed, providing promising solutions and blueprints for green and novel desalination technologies while achieving sustainable development.

Study of vortex rope based on flow energy dissipation and vortex identification

Vortex rope causes instabilities in hydro-turbines and marine turbines. It is an important issue in the utilization of ocean energy. The flow energy dissipation (FED) is one of instability problems of turbines. The FED of vortex rope can be evaluated by the entropy production rate (EPR) according to the second law of thermodynamics. The EPR will provide a visualization of the energy change and make a better understanding of the vortex rope. In this study, a swirl generator is studied by analyzing FED and vortical flow pattern with embedded Large Eddy Simulation. By comparing Liutex method with FED's sub items, it is found that the vortex rope will not produce large energy loss. The high FED is mainly produced at the vortex rope boundary where the vortex rope interacts most strongly with the surrounding fluid. Voigt line-shape function is used to quantitatively describe the vortex rope and partition the draft tube. Transition region represents the region where the interaction mainly occurred. Transition region accounts for a higher proportion than other regions. This study provides an effective way in understanding the mechanism of FED in vortex rope and can be used to eliminate vortex rope in hydro-turbines and marine turbines.

An electrochemical system for salinity gradient energy harvesting

Salinity gradient energy, which is abundant along the coastline in ocean, is a kind of chemical energy existing the solutions of different concentrations mixing. The pressure retarded osmosis, reverse electrodialysis and accumulator mixing technology are currently the most common approaches to harvest salinity gradient energy. Here we report an electrochemical device using active carbon as anode and manganese phosphate as cathode for salinity gradient energy harvesting, which shows an energy density of 5.31 J g−1, indicating a potential application in the field of ocean energy utilization.

Ocean Energy Development under the Background of Carbon Emissions Peak and Carbon Neutrality in China

The ocean energy resources are abundant in China. The technical potential in Chinese coastal area is more than 70 GW. Thus, the utilization of ocean energy resources is very important for the energy saving and the mitigation of climate change. The Renewable Energy Law implemented since 2010 and the special fund program for ocean energy established in 2011 has advanced great progress of ocean energy technology research, development and demonstration in recent years in China. The ocean energy technologies in China have achieved rapid development under the support of the Ministry of Finance, the Ministry of Natural Resources, the Ministry of Science and Technology and so on. The accumulated capacity of ocean energy is in the international advanced level, but the ocean energy industry is still in early stage. The carbon emissions peak and carbon neutrality strategy put forward in China requires the transition to green energy and electricity, which also provides crucial opportunity for the development of the utilization of ocean energy resources in China. The paper introduces the status of ocean energy technology and industry in China firstly. Then the problems in the development of ocean energy are analysed. The potential of utilization of ocean energy is estimated to support the carbon emission reduction. Finally, the vision and main tasks are given.

Characteristics of electric performance and key factors of a hybrid piezo/triboelectric generator for wave energy harvesting

Since the ocean energy field has a wide variety range of frequencies and amplitude, applying energy harvesters such as a piezoelectric generator (PEG) with a triboelectric generator (TEG) has been required for maximum result. Generally, energy harvesters can perform well due to the feature mechanism generation and the surface modification. However, few studies explain the relationship between characteristics of power generation with the device’s key factors. This study proposed/developed a TEG into a multi-layered model, combined it with a PEG to form a PEG-TEG hybrid harvester, and demonstrated the improvement of the output voltage by modifying the key factors (i.e., acceleration amplitude, vibration amplitude, initial distance). We found that our hybrid harvester with the multi-layered TEG can improve the electrical energy output in linear terms under a comparatively small device. Furthermore, the key factors have much influence to generate electrical energy instead of compression force, suggesting that a small force is enough to produce a good result. Our result also showed that this linear improvement is possible due to the increase of vibration amplitude, indicating that amplitude adjustment is important, but it is not directly related to a good electrical performance for initial distance. Finally, the complementary relationship between devices was investigated, and it shows good compatibility. The study could be an essential finding and understanding for PEG-TEG hybrid energy harvesters to produce more efficient and sustainable harvesters in the ocean energy utilization.

Research on wave and tidal current law prediction and coupling mechanism applied to ocean energy utilization

The energy efficiency of integrated wave and current turbine is closely related to the velocity and direction of wave force and tidal current force.To study the blade motion of the wave-tidal current integrated variable-pitch turbine, raise the capacity efficiency of the turbine, take Fishing grounds of Changjiang estuary Port as an example,based on the tidal current and wave features data in recent two years,time series prediction model was established to predict the changes of wave and tidal current in the next 24 hours respectively, and the prediction accuracy is up to 93%. The wave theory applicable to Fishing grounds of Changjiang estuary Port was confirmed as the second-order strokes wave theory, the wave-tidal current coupling equivalent velocity vector was deduced, which is related to the tidal current velocity, flow direction, average wave direction, average wave period and significant wave height. The predicted wave-current coupling velocity vector is obtained after the predicted 24 hours wave-current data was substituted into it, which can provide a method and basis for the design of marine energy turbine’s variable angle law in the future, and can be applied to the development of new energy and the prediction of Marine environment.

Multi-Energy System Based on Ocean Thermal Energy Conversion

The ocean thermal energy is abundant. The global total is about 40 billion kW. The ocean thermal energy conversion (OTEC) is clean and renewable, the power generation is stable, and the energy storage has high capacity. Active exploitation of ocean thermal energy resources is of great significance to realize the strategy of maritime power. In view of the efficiency limit of a traditional OTEC, authors propose an approach of a multi-energy complementary OTEC system that they can improve the efficiency of this system. The approach sets parameters at the system level and integrates solar energy, wind energy, energy storage and OTEC. For example, a 1MW integrated power generation system is designed and simulated by means of computer aided design and of conducting a model-based simulation, respectively. The efficiency of the complementary OTEC system with solar heating can reach 13.12%. In this article, the basic principle and working process of the approach are analyzed, and the system efficiency is calculated. The results show that, in comparison to the traditional OTEC, the complementary system of OTEC can improve the ratio of power generation output efficiency, stability and ocean energy utilization.

Optimal offering strategy of virtual power plant with hybrid renewable ocean energy portfolio

This paper proposes a hybrid ocean energy system to form a virtual power plant (VPP) for participating in electricity markets in order to promote the renewable ocean energy utilization and accommodation. In the proposed system, solar thermal energy is integrated with the closed-cycle ocean thermal energy conversion (OTEC) to boost the temperature difference between surface and deep seawater for efficiency and flexibility improvements, and the thermodynamic effects of seawater mass flow rates on the output of solar-boosted OTEC (SOTEC) are exploited for deploying SOTEC as a renewable dispatchable unit. An optimal tidal-storage operation model is also developed to make use of the subsea pumped storage (SPS) with hydrostatic pressures at ocean depth for mitigating the intermittent tidal range energy in order to make the arbitrage in the electricity market. Furthermore, a two-stage coordinated scheduling strategy is presented to optimally control seawater mass flow rates of SOTEC and hydraulic reversible pump-turbines of SPS for enhancing the daily VPP profit. Comparative studies have been investigated to confirm the superiority of the developed methodology in various renewable ocean energy and electricity market price scenarios.

Research on Key Technologies of Wave Energy Power Generation System

Most of the surface of the earth is occupied by oceans, and huge energy is stored in the oceans. Among marine energy sources, wave energy, tidal energy, tidal current energy, etc. are included. As a widely distributed, high energy density, pollution-free and environmentally friendly renewable energy source, ocean wave energy attaches great importance to ocean energy in most countries in the world. Compared with wind power and photoelectricity, the utilization of ocean energy with wider distribution and greater energy density is still lagging behind. Ocean wave energy power generation mainly refers to the use of corresponding technical equipment to convert the powerful kinetic energy of ocean waves into electrical energy. In view of the current tight supply of traditional energy, it can effectively relieve the problem, promote the development of marine resources and improve the environment. Therefore, this paper studies the wave power generation technology. First, the article analyzes the system principle of using wave energy to generate electricity, introduces several commonly used wave energy conversion devices, and then studies its power generation technology from the aspect of control strategy, so as to maximize the energy conversion power in the wave energy generation process. It will maximize the conversion of wave energy to electrical energy.

Preface

It is our great pleasure to welcome all of you to 2020 7th International Conference on Coastal and Ocean Engineering (ICCOE 2020) April 22-24, 2020, Singapore. ICCOE 2020 is dedicated to issues related to Coastal and Ocean Engineering.Due to the COVID-19 pandemic, the conference committees made a decision to hold an online conference instead to ensure every participant’s personal safety.CCOE 2020 is highlighted with four keynote speakers: Prof. Gordon Huang (University of Regina, Canada); Prof. Chou Loke Ming (National University of Singapore, Singapore); Prof. Koh Hock Lye (Sunway University, Malaysia); Associate Professor Edmond Yat-Man Lo (Nanyang Technological University, Singapore).The Conference had one poster session and four oral sub-sessions on different topics: Environmental Science and Engineering, Innovation and Economic Development, Ocean Engineering, Marine Science and Ship Engineering.It was a great opportunity for students, researchers and engineers to interact with the experts and specialists to get advice or consultation on technical matters, dissemination and marketing strategies.This volume of the proceedings presents a selection of papers submitted to the conference. They are organised in nine chapters under the topics of: Utilization of Ocean Space, Marine Resource Exploitation, Utilization of Ocean Energy, Ship Engineering, Marine Dynamics, Architectural Design, Fire Safety Engineering, Environmental Science and Technology, and Economic Innovation. All papers were subjected to peer-review by conference committee members and international reviewers. The papers were selected based on high quality and relevance to the conference theme.We express our sincere appreciation to the organizing committee and the volunteers who had dedicated their time, effort and help in planning, promoting, and organizing the conference.Prof. Chou Loke MingNational University of Singapore, Singapore2020-04-29

Numerical investigations of the energy performance and pressure fluctuations for a waterjet pump in a non-uniform inflow

As a way of exploitation and utilization of ocean energy, the waterjet pump is used in a wide range of high-speed marine vessels over 30 knot. This paper aims to investigate the mechanism of the energy loss and pressure fluctuations caused by the non-uniform inflow for a waterjet pump. Unsteady internal flows inside the waterjet pump are simulated using the Reynolds-averaged Navier-Stokes equations with the SST k-ω turbulence model. The predicted pump head and efficiency are in reasonable accordance with the experimental data. The inflow non-uniformity would decrease the hydraulic head, efficiency and increase the axial force fluctuations in the impeller, causing large pulsations in the unsteady energy performance. Based on analyses of the energy loss, the turbulent kinetic energy production and the diffusion of the Reynolds stress are major sources of the energy loss in the waterjet pump. The non-uniform inflow induces a dramatic energy loss in the intake duct and diffuser with an apparent flow separation observed near the trailing edge of the diffuser blade. Due to the inflow non-uniformity, the pressure fluctuates violently at the impeller rotating frequency (fn) in the intake duct, impeller and near the diffuser inlet, but a dominant frequency of 2fn is generated by the unsteady flow separation near the diffuser outlet.

Hybridized nanogenerator based on honeycomb-like three electrodes for efficient ocean wave energy harvesting

Ocean energy is one of the most promising clean and renewable natural energy sources, however, owing to traditional energy harvesting technology, the collection and utilization of ocean energy is extremely limited. In this work, a hybridized ocean wave nanogenerator (How-NG) based on honeycomb-like three electrodes has been proposed, which consists of a triboelectric nanogenerator (TENG) and an electromagnetic generator (EMG), where the TENG works in both in-plane sliding mode and vertical contact-separation mode. With innovative design in electrode structure and hybrid of TENG and EMG, the How-NG can harvest two types of wave energy, kinetic energy and potential energy of ocean surface wave. The honeycomb-like three electrode structure is designed to harvest wave energy in multi-angle range for random waves. In addition, by adjusting the weight of the magnet to achieve different resonance parameters, the How-NG could reach a resonant state and more efficient collection of ocean energy. Furthermore, the influence of the working frequency and sliding displacement on the electrical outputs of the TENG unit and EMG unit are investigated systematically. The maximum output energy of TENG and maximum power of EMG can reach 21.7 µJ and 8.23 µW respectively at fixed working frequency of 4.0 Hz and sliding displacement of 3.5 cm. In addition, those two basic units are assembled vertically into a sealed cylinder acrylic shell which is used to drive LEDs by harvesting the water wave energy. This work presents a novel and efficient approach toward large-scale blue energy harvesting from the ocean.

A conceptual model for prioritizing dam sites for tidal energy sources

Ocean energy is abundant in China, and the utilization of ocean energy could improve current energy structure and contribute to energy security. If tidal power is harnessed efficiently, it could help China reach its renewable energy goals. A suitable model for solving the multi-criteria decision-making problem is proposed in this paper. The model incorporates the fuzzy analytic network process (FANP) and the fuzzy goal programming (FGP). The FANP can consider various factors, the interrelationships among the factors, and the impreciseness and vagueness of the problem more thoroughly based on expert opinions. The FGP can help select dam sites to maximize the satisfaction of the system when resources are limited. A case study in an east-coast province in China is presented to demonstrate the practicality of the proposed model.

Impact assessment of marine current turbines on fish behavior using an experimental approach based on the similarity law

Energy from tidal streams is a reliable renewable energy source worth exploiting. With increasing concern over the potential effects of ocean energy utilization on marine environment and organisms, several previous experimental studies have been conducted focusing on fish behavior and their collision risk with hydrokinetic turbines for power generation. This study is aimed at exploring the behavior of marine animals around marine current turbines (MCTs) in the sea environment by conducting a laboratory experiment based on similarity laws for the turbine tip speed and maximum marine animal swimming speed. Three rotation frequencies (0, 5 and 20 rpm) with two releasing areas (upstream and downstream areas) were considered in our experiment. Results showed that fish survival rate was 100 % after 48 h, and only one fish came into contact with the turbine hub and was inactive in front of it when the MCT was in a stationary state during our preliminary test of swimming endurance. Although both the initial releasing area of fish and the rotation speed of MCT have significant effects on fish passage count rate (PCR) via a turbine, there is no interaction between these two factors. PCR was generally higher when fish were put into the tank in the downstream area, irrespective of the turbine rotation. And the returning behavior in the downstream area was more frequently found compared with that in the upstream area, which indicates that the location of MCTs should be considered at the downstream of a channel in practice to reduce the potential risk of fish injury. The ratio of fish passing from the outer side (±3) of the turbine was larger, and a clear U-shaped distribution could be observed. The entering behavior almost disappeared (less than 1.3 %) when MCT rotated with a frequency of 20 rpm. It indicates the design of the rotation frequency of MCT should be more than 20 rpm. However, higher tip speeds and darkness conditions are not considered in our experiment. Based on the laws of similarity proposed in this study, it becomes possible to compare the experimental results with real sea results, to allow explanation and discussion of fish behavior around MCTs, through the parameters of flow velocity, turbine tip speed, and maximum fish swimming speed.

Experiments on the hydrodynamic performance of horizontal axis tidal current turbine and desalination of sea water

Summary Tidal current turbine is the core equipment to convert the tidal current energy. In this paper, the performance of the designed tidal current turbine is tested in the laboratory, then the impeller is used to conduct an experiment on the desalination of sea water. The sea test of the novel equipment has been done in BoHai Sea. The experimental results indicate that the efficiency of the newly developed turbine could reach up to 47.6%; the corresponding tip speed ratio is from 3.5 to 6. Under the condition of big yaw angle, the turbine could still remain high working efficiency. When the tidal current velocity exceeds 1.0 m/s, the pressure may increase to 3.5 Mpa, and under this condition, sea water can be desalinated through reverse osmic membrane. The electrical conductivity of desalinated water is around 540 μS/cm. For the experiment on hydrodynamic performance, the self-starting flow velocity of the turbine is 0.745 m/s, the staring torque is 1 Nm while about 0.97–1.0 m/s self-starting flow velocity and around 10–15 Nm starting torque for the experiment on desalination of sea water. It is believed a good attempt by using tidal current turbine in the desalination of sea water, providing the practice basis on expanding the utilization of ocean energy. Copyright © 2015 John Wiley & Sons, Ltd.