Search

This paper provides an overview of the global wave resource for energy exploration. The most popular metrics and estimators for wave energy resource characterization have been compiled and classified by levels of energy exploration. A review of existing prospective wave energy resource assessments worldwide is also given, and those studies have been collated and classified by continent. Finally, information about forty existing open sea wave energy test sites worldwide and their characteristics is depicted and displayed on a newly created global map. It has been found that wave power density is still the most consensual metric used for wave energy resource assessment purposes among researchers. Nonetheless, to accomplish a comprehensive wave resource assessment for exploitation, the computation of other metrics at the practicable, technical, and socio-economic levels has also been performed at both spatial and temporal domains. Overall, regions in latitudes between 40° and 60° of both hemispheres are those where the highest wave power density is concentrated. Some areas where the most significant wave power density occurs are in offshore regions of southern Australia, New Zealand, South Africa, Chile, the British Isles, Iceland, and Greenland. However, Europe has been the continent where most research efforts have been done targeting wave energy characterisation for exploitation. [ABSTRACT FROM AUTHOR]

Highlights: The basic information of triboelectric nanogenerator (TENG), the power conversion process, and key points of the marine energy harvesting TENGs was introduced in detail. An in-depth introduction and analysis of relevant research with the marine energy harvesting were conducted through gradient classification. This review not only provided a deeper summary of the latest research progress, discoveries, and challenges, but also made a rational outlook on solutions to related issues and future development directions. The large-scale use of ample marine energy will be one of the most important ways for human to achieve sustainable development through carbon neutral development plans. As a burgeoning technological method for electromechanical conversion, triboelectric nanogenerator (TENG) has significant advantages in marine energy for its low weight, cost-effectiveness, and high efficiency in low-frequency range. It can realize the efficient and economical harvesting of low-frequency blue energy by constructing the floating marine energy harvesting TENG. This paper firstly introduces the power transfer process and structural composition of TENG for marine energy harvesting in detail. In addition, the latest research works of TENG on marine energy harvesting in basic research and structural design are systematically reviewed by category. Finally, the advanced research progress in the power take-off types and engineering study of TENG with the marine energy are comprehensively generalized. Importantly, the challenges and problems faced by TENG in marine energy and in situ electrochemical application are summarized and the corresponding prospects and suggestions are proposed for the subsequent development direction and prospects to look forward to promoting the commercialization process of this field. [ABSTRACT FROM AUTHOR]

The potential energy associated with tides presents a sustainable energy resource that remains largely untapped. Uncertainties on the economic case of tidal range power plants are a known obstacle. Research on tidal range structures suggests energy yield may be maximized through operation strategy optimization, and that impacts can be mitigated through design optimization. While instructive, these perspectives alone are insufficient to support the feasibility of individual projects. We integrate operation optimization and hydrodynamic impact analyses within a cost evaluation framework for tidal range structures focusing on capital costs (CAPEX) and levelized cost of energy (LCOE). Once benchmarked against 11 historic proposal cost projections, we perform a redesign of 18 tidal power plants to deliver a comprehensive comparative basis across a diverse range of sites in the UK. Tidal power plant operation is simulated in regional shallow-water equation models, acknowledging tide variability. The cost evaluation framework demonstrates the impact of geospatial variations on key cost components. The redesign process indicates transformative implications in that equivalent and lower LCOE values can be achieved for designs at a substantially lower CAPEX. Given how the latter hinder development, we show how tidal range schemes could be far more economically feasible than commonly perceived. [ABSTRACT FROM AUTHOR]

Testing and research centres for offshore renewable energy, exemplified by facilities like BIMEP (Biscay Marine Energy Platform) on the Basque coast of Spain, play a crucial role in driving the energy transition. This study utilises pre-existing data at the facility site, such as high-resolution bathymetry and granulometric information from sediment samples, to conduct a comprehensive geological analysis including both sedimentary and rocky seabed. A litho-structural analysis is presented, including a lithological prediction for the continental shelf, the recognition of the main structures, such as NW-trending folds and predominantly NE-SW oriented fractures, and a detailed fracture analysis. Sedimentary seabeds are analysed through a Seabed Sediment Map, illustrating a granulometry-based NE-SW oriented banded distribution. Bedforms are also studied, they are asymmetric and mainly oriented NE-SW. The Seabed Sediment Map and the bedform analysis reveal the effect of an SE-directed bottom current as the main mechanism controlling sediment mobility. This current matches with the predominant swell from the NW and with the direction of the most energetic waves in the area. This approach could serve as a methodological example, offering a cost-effective means for the preliminary geological characterisation of offshore energy sites, and is crucial for establishing a baseline ('zero state') before the deployment. This baseline is essential for evaluating and mitigating the impact of new infrastructure on sediment dynamics, which subsequently affects the overall functioning and health of the marine ecosystem. [ABSTRACT FROM AUTHOR]

Ocean energy, e.g., waves, tidal current, and thermal and salinity gradient, can be used to produce electricity. These marine-based renewable energy technologies are at relatively early stages of development and potentially deployed at various sea conditions. In the past, numerous studies were undertaken to explore the feasibility of harvesting of the marine energy in Malaysia; however, those studies were limited to a specific location (i.e., the east coast of Peninsular Malaysia and East Malaysia) and the consideration of sea level rise effect was not studied. This study assessed the potential of tidal and wave energy resources in Malaysia's waters with the effect of projected sea level rise and was undertaken through numerical modeling using MIKE 21 software. The research outcomes were tidal and wave energy contours for Malaysia's waters with an inclusion of the sea level rise projection for 2060 and 2100, as well as a potential site determined for tidal and wave energy harvesting. The simulation results highlight the significant potential of tidal and wave energy in specific locations around Malaysia and its coastal regions, as well as in the South China Sea's offshore regions. By incorporating sea level rise projections into tidal and wave simulations, we revealed a notable increase in tidal and wave power. [ABSTRACT FROM AUTHOR]

Wave energy holds significant promise as a renewable energy source due to the consistent and predictable nature of ocean waves. However, optimizing wave energy devices is essential for achieving competitive viability in the energy market. This paper presents the application of a nonlinear model predictive controller (MPC) to enhance the energy extraction of a heaving point absorber. The wave energy converter (WEC) model accounts for the nonlinear dynamics and static Froude–Krylov forces, which are essential in accurately representing the system's behavior. The nonlinear MPC is tested under irregular wave conditions within the power production region, where constraints on displacement and the power take-off (PTO) force are enforced to ensure the WEC's safety while maximizing energy absorption. A comparison is made with a linear MPC, which uses a linear approximation of the Froude–Krylov forces. The study comprehensively compares power performance and computational costs between the linear and nonlinear MPC approaches. Both MPC variants determine the optimal PTO force to maximize energy absorption, utilizing (1) a linear WEC model (LMPC) for state predictions and (2) a nonlinear model (NLMPC) incorporating exact Froude–Krylov forces. Additionally, the study analyzes four controller configurations, varying the MPC prediction horizon and re-optimization time. The results indicate that, in general, the NLMPC achieves higher energy absorption than the LMPC. The nonlinear model also better adheres to system constraints, with the linear model showing some displacement violations. This paper further discusses the computational load and power generation implications of adjusting the prediction horizon and re-optimization time parameters in the NLMPC. [ABSTRACT FROM AUTHOR]

Recent research revealed the potential of tidal energy in the central coastal region of the Colombian Pacific. Buenaventura City, located in the Valle del Cauca department in Colombia, has an important opportunity to develop tidal power technologies near its marine coastal areas. This research implemented a 3D hydrodynamic model for simulating the hydrodynamics of the Buenaventura Bay to provide data as input for evaluating the hydraulics of a tidal barrage without sluicing through CFD modeling. According to the results, the velocities across the gates during Syzygy (April 2021) showed impressive velocities between 9 and 11 m/s, which suggest a high possibility of producing electricity through tidal turbines. The mean behavior of velocities in the gates pointed to values of 3 and 5 m/s in most of the cases. The results during the Stoa condition were interesting because flow velocities higher than 1 m/s were not expected. This is promising because the plant might produce electricity even during the Stoa condition. For the first time, the results of this research suggest that there exists a high possibility of implementing tidal barrage plants in Buenaventura City, Colombia. [ABSTRACT FROM AUTHOR]

Offshore energy generation is one of the fastest-growing U.S. marine sectors, ranging from expanding deployment of offshore wind to rapid development and testing of technologies for energy conversion from waves, tides, ocean currents, and gradients in temperature, salinity, and pressure. Generating energy from the offshore environment creates expanded opportunities to improve upon the collection of ocean and coastal-derived data and information that will support economic and maritime growth, the management of resources, and solutions to address societal and climate issues. Despite its many promises and challenges, barriers remain for widespread implementation of offshore energy generation technologies that address the nation’s energy needs and climate change. A town hall was convened to present a vision of the changing ocean-scape through the lens of marine renewable technologies and to explore innovative solutions that these technologies might offer to support the New Blue Economy. [ABSTRACT FROM AUTHOR]

Energy harvesting from Vortex-Induced Vibration (VIV) presents a promising avenue for renewable energy generation by harnessing the kinetic energy of fluid flows through innovative technologies. Despite the increasing interest in VIV energy harvesting, there is a need for a systematic evaluation of the existing literature to understand the research trends, key contributors and emerging areas of focus. A bibliometric analysis offers a quantitative approach to address this gap, providing valuable insights into the evolution and dynamics of research on energy harvesting from VIV. The analysis employs VOSviewer software to analyze publication data retrieved from Scopus, focusing on publication trends, top authors, subject area, top citation, popular keywords, co-authorship countries’ collaboration and network mapping based on citation by country. By examining publication patterns, citation counts and collaboration networks, this study aims to uncover underlying patterns and identify critical factors driving research in this field. The bibliometric analysis reveals a significant upward trend in research activity, with a notable increase in publications from recent years, indicating growing interest and recognition of VIV energy harvesting. In conclusion, this bibliometric analysis provides valuable insights into the research trends, key contributors and collaborative networks in energy harvesting from VIV. The findings guide for both academic and industrial , facilitating informed decision-making and driving progress toward sustainable energy solutions. This study also lays the groundwork for future research directions and interdisciplinary collaborations aimed at maximizing the potential of VIV energy harvesting for renewable energy generation.

Ocean energy, e.g., waves, tidal current, and thermal and salinity gradient, can be used to produce electricity. These marine-based renewable energy technologies are at relatively early stages of development and potentially deployed at various sea conditions. In the past, numerous studies were undertaken to explore the feasibility of harvesting of the marine energy in Malaysia; however, those studies were limited to a specific location (i.e., the east coast of Peninsular Malaysia and East Malaysia) and the consideration of sea level rise effect was not studied. This study assessed the potential of tidal and wave energy resources in Malaysia’s waters with the effect of projected sea level rise and was undertaken through numerical modeling using MIKE 21 software. The research outcomes were tidal and wave energy contours for Malaysia’s waters with an inclusion of the sea level rise projection for 2060 and 2100, as well as a potential site determined for tidal and wave energy harvesting. The simulation results highlight the significant potential of tidal and wave energy in specific locations around Malaysia and its coastal regions, as well as in the South China Sea’s offshore regions. By incorporating sea level rise projections into tidal and wave simulations, we revealed a notable increase in tidal and wave power.

Numerous offshore wave energy converter (WEC) designs have been invented; however, none has achieved full commercialization so far. The primary obstacle impeding WEC commercialization is the elevated levelized cost of energy (LCOE). Consequently, there exists a pressing need to innovate and swiftly diminish the LCOE. A critical challenge faced by WECs is their susceptibility to extreme wave loads during storms. Promising concepts must demonstrate robust design features to ensure resilience in adverse conditions, while maintaining efficiency in harnessing power under normal sea states. It is anticipated that the initial commercial endeavors will concentrate on near-shore WEC technologies due to the cost advantages associated with proximity to the coastline, facilitating more affordable power transmission and maintenance. In response, this manuscript proposes a pioneering near-shore WEC concept designed with a survivability mode that is engineered to mitigate wave loads during severe sea conditions. Moreover, prior investigations have highlighted favorable resonance properties of this novel concept, enhancing wave power extraction during recurrent energetic sea states. This study employs numerical and physical modelling techniques to evaluate wave loads on the proposed WEC. The results indicate a remarkable 65% reduction in wave loads on the moving floater of the WEC during a range of sea states under the implemented survivability mode. [ABSTRACT FROM AUTHOR]

Ocean energy sources are a promising source of energy. However, simulating a hydrokinetic farm with multiple units requires significant computational resources, while physical experimentation on site is expensive. Therefore, the scientific challenge is to develop analytical and experimental tools that consider real aspects of areas with generation potential in a controlled laboratory environment. This paper presents a theoretical and experimental tool for analysing the interconnection of a hydrokinetic energy farm comprising 20 generation units. The test bench is a Power Hardware in the Loop type, consisting of one physical prototype generator to scale and 19 discrete averaged models operating in real-time. The system allows generators to interact through an amplifier, emulating the impact of power injection in a small electrical network. This is based on the variability of the marine resource, specifically the current velocities in the Cozumel-Mexico channel. Unlike other publications, the most significant contribution of this work is a complete feasible emulation of a marine current plant interconnected to an electrical grid, where the objective is to have a global analysis of the operation of each generation unit and the impact of the interconnection as a whole, considering that such information is of utmost importance for the execution of future projects of power generation from the sea. [ABSTRACT FROM AUTHOR]

Nova Scotia’s marine renewable energy (MRE) sector can contribute to provincial goals for carbon neutrality. With this, tidal energy has been an interest to industry stakeholders for over two decades, yet general momentum for the industry has shifted. Previous tidal energy projects and recent studies suggest there needs to be a shift in focus towards scalable tidal energy (i.e., small-scale) development in the province. This research explores the considerations of developing tidal energy in Southwest Nova Scotia with an emphasis on small-scale tidal devices. Using a comprehensive literature review and in-depth semi-structured interviews with stakeholders from different sectors of Nova Scotia’s MRE energy industry, key issues and challenges were explored. Results underline four main themes that affect industry potential, which include cost and financing, technology, policy, and energy distribution. These results support a discussion around the value of small-scale technology, regulatory pathways, industry collaboration, and using global best practices to accelerate tidal energy industry goals in Nova Scotia.

Energy and water systems are deeply interdependent yet organized and managed into separate sectors. Although technological innovations emerge at the intersection of energy and water, these sectors largely operate independently, despite their mutual importance. This persistent challenge is structural, as the sectors are organized and managed as separate systems. More can be done to integrate these sectors for mutual benefit and resilience. This paper provides an overview and a useful categorization of six research areas that bridge the water and energy sectors: integrated planning, integrated operations, data and analytics, policy and economics, hydropower and marine energy, and resilience. The authors lead the IEEE Power & Energy Society Task Force on Water-Power Systems (WPS), which represents an international and rapidly growing collaboration across both energy and water sectors to find common areas of cooperation and innovation. Through the collective efforts of this Task Force, a comprehensive roadmap on water power systems integration was issued in 2023. The paper presents evidence that coordinated efforts in data analytics, policy, and economic interventions can significantly advance hydropower, marine energy, and energy storage technologies, ultimately enhancing the resilience and efficiency of both water and power infrastructures.

Abstract Due to the rapid development of today's industry, it not only greatly accelerates the consumption of energy, but also causes serious pollution to the environment. Therefore, reducing energy waste and recovering energy has become an important research direction today. This paper introduces the future development trend of renewable energy, discusses the progress of recovery of nonpolluting energy such as marine, bioenergy and thermal energy, and analyzes the efficiency and social benefits of various types of energy recovery. Energy recovery methods for natural gas pipelines are briefly analyzed, and current research advances in energy pressure recovery devices are provided, leading to a summary of methods to improve the efficiency of fluid energy recovery. Finally, it is concluded that although the current energy sources are diversified, the most valued energy sources at present and in the future should be solar energy and ocean, which are infinitely recyclable. This paper will benefit researchers to further understand and study the various aspects of energy recovery.

Battiau-Queney, Y.; Ventalon, S.; Abraham, R.; Sipka, V.; Cohen, O., and Marin, D., 2024. Bedforms and sedimentary features related to water-depth variations in a sandy tidal-flat environment. Journal of Coastal Research, 40(1), 80–103. Charlotte (North Carolina), ISSN 0749-0208. This study highlighted the variability of a wide sandy macrotidal coastal system on short timescales. Changes in water depth and exposure length were the main drivers of this variability. In the study area, the coastal system consists of three units: a lower ridge-and-runnel beach, a 1000-m-wide tidal flat, and a sandy backshore. This research is based on sedimentary features that can record physical forces, especially the bedforms at the beach surface, and their relationship with beach gradient, exposure length, and changing water depth, according to tidal, weather, and marine conditions. It also demonstrated the ability of scanning electron microscope analysis of quartz grain microtextures to indicate the level of marine and eolian energy in the coastal system. The widespread wave and current sand ripples on the tidal flat showed great variability in time and space. A minimum water depth of 0.30 to 0.50 m was required for their development. The role of wind-induced waves and the frequent interference of tidal, wave, and wind forcing mechanisms are emphasized. The development of some complex sand ripples extended over a complete lunar tidal cycle. Wind-generated sand ripples were observed only on the backshore. Their absence on the tidal flat, despite the high level of eolian energy attested by quartz microtextures, and the poor development of dunes on the backshore are explained by factors impeding eolian sand transport at the beach surface such as extreme fetch segmentation and possible shell armoring of the beach surface during dry periods. This study demonstrated the short-term variability of the beach morphology as opposed to the long-term stability of the coastal system as a whole, in which the ultradissipative tidal flat, characterized by limited sand supply, low wave energy, and high but inefficient wind energy, plays a key role. [ABSTRACT FROM AUTHOR]

Energy harvesting from Vortex-Induced Vibration (VIV) presents a promising avenue for renewable energy generation by harnessing the kinetic energy of fluid flows through innovative technologies. Despite the increasing interest in VIV energy harvesting, there is a need for a systematic evaluation of the existing literature to understand the research trends, key contributors and emerging areas of focus. A bibliometric analysis offers a quantitative approach to address this gap, providing valuable insights into the evolution and dynamics of research on energy harvesting from VIV. The analysis employs VOSviewer software to analyze publication data retrieved from Scopus, focusing on publication trends, top authors, subject area, top citation, popular keywords, co-authorship countries' collaboration and network mapping based on citation by country. By examining publication patterns, citation counts and collaboration networks, this study aims to uncover underlying patterns and identify critical factors driving research in this field. The bibliometric analysis reveals a significant upward trend in research activity, with a notable increase in publications from recent years, indicating growing interest and recognition of VIV energy harvesting. In conclusion, this bibliometric analysis provides valuable insights into the research trends, key contributors and collaborative networks in energy harvesting from VIV. The findings guide for both academic and industrial , facilitating informed decision-making and driving progress toward sustainable energy solutions. This study also lays the groundwork for future research directions and interdisciplinary collaborations aimed at maximizing the potential of VIV energy harvesting for renewable energy generation. [ABSTRACT FROM AUTHOR]

Recent research revealed the potential of tidal energy in the central coastal region of the Colombian Pacific. Buenaventura City, located in the Valle del Cauca department in Colombia, has an important opportunity to develop tidal power technologies near its marine coastal areas. This research implemented a 3D hydrodynamic model for simulating the hydrodynamics of the Buenaventura Bay to provide data as input for evaluating the hydraulics of a tidal barrage without sluicing through CFD modeling. According to the results, the velocities across the gates during Syzygy (April 2021) showed impressive velocities between 9 and 11 m/s, which suggest a high possibility of producing electricity through tidal turbines. The mean behavior of velocities in the gates pointed to values of 3 and 5 m/s in most of the cases. The results during the Stoa condition were interesting because flow velocities higher than 1 m/s were not expected. This is promising because the plant might produce electricity even during the Stoa condition. For the first time, the results of this research suggest that there exists a high possibility of implementing tidal barrage plants in Buenaventura City, Colombia.

Tidal stream energy is a predictable renewable energy source; however, environmental consent of developments remains a key barrier to the expansion of this industry. Uncertainty around collision risk, i.e., the risk of animals colliding with a tidal device, remains a major barrier to consent. Collision risk models are used in environmental impact assessments. Common collision risk models, like the Encounter Rate and Band Models, have limitations in accommodating new device designs and flexibility. To address this, a simulation-based approach was developed. To provide confidence in its use, it is important that the simulation-based approach is compared against the Band model and the Encounter rate model, which have been regularly used in the UK. Here, we compared collision risk estimates from the three models under the same exact conditions and one alternative condition. The results of the main scenario (where all conditions were the same) showed that the three models produced comparable results with <6% difference across all models. However, for the alternative scenario, the simulation-based approach produced a result three times higher compared to other models, which could not account for a vertical approach angle. These findings provide confidence in the simulation-based approach whilst also outlining the importance of selecting an appropriate collision risk model, tailored to the specific assessment scenario. Improved understanding and application of such models hold the key to more accurate risk evaluations in environmental impact assessments, thus facilitating the sustainable development of the tidal energy industry. [ABSTRACT FROM AUTHOR]

Marine current energy converters such as tidal and riverine turbines have the potential to provide reliable, clean power. The risk of collision of fishes with marine energy turbines is not yet well understood, in part due to the challenges associated with observing fish at turbine sites. Turbidity and light availability can limit the effectiveness of optical sensors like video cameras, motivating the use of acoustic cameras for this task. However, challenges persist in collecting and interpreting data acquired from acoustic cameras. Given the limited number of turbine deployments to date, it is prudent to draw on the application of acoustic cameras to monitor fish in other scenarios. This article synthesizes their use for other fisheries applications to inform best practices and set realistic expectations for the results of acoustic camera monitoring at turbine sites. We discuss six key tasks performed with acoustic cameras: detecting objects, identifying objects as fish, counting fish, measuring fish, classifying fish taxonomically and analysing fish behavior. Specific challenges to monitoring fish at turbine sites are discussed. This article is intended to serve as a reference for researchers, regulators and marine energy developers on effective use of acoustic cameras to monitor fish at turbine sites. The studies detailed in this article provide evidence that, in some scenarios, acoustic cameras can be used to inform the risk of fish collision with marine energy turbines but doing so requires careful study design and data processing. [ABSTRACT FROM AUTHOR]

The interactions between marine wildlife and marine energy devices are not well understood, leading to regulatory delays for device deployments and testing. Technologies that enable marine wildlife observations can help to fill data gaps and reduce uncertainties about animal–device interactions. A validation test conducted in Galveston Bay near La Porte, Texas, in December 2022 used a technology package consisting of a tethered balloon system and three independent sensor systems, including three-band visible, eight-band multispectral, and single-band thermal to detect three marine-mammal-shaped surrogates. The field campaign aimed to provide an initial step to evaluating the use of the TBS and the effectiveness of the sensor suite for marine wildlife observations and detection. From 2 December to 7 December 2022, 6 flights were conducted under varying altitudes and environmental conditions resulting in the collection of 5454 images. A subset of the images was classified and analyzed with two collection criteria including Beaufort wind force scale and TBS altitude to assess a range of observations of a surrogate from near-shore to offshore based on pixel count. The results of this validation test demonstrate the potential for using TBSs and imaging sensors for marine wildlife observations and offer valuable information for further development and application of this technology for marine energy and other blue economy sectors. [ABSTRACT FROM AUTHOR]

Due to the rapid development of today's industry, it not only greatly accelerates the consumption of energy, but also causes serious pollution to the environment. Therefore, reducing energy waste and recovering energy has become an important research direction today. This paper introduces the future development trend of renewable energy, discusses the progress of recovery of nonpolluting energy such as marine, bioenergy and thermal energy, and analyzes the efficiency and social benefits of various types of energy recovery. Energy recovery methods for natural gas pipelines are briefly analyzed, and current research advances in energy pressure recovery devices are provided, leading to a summary of methods to improve the efficiency of fluid energy recovery. Finally, it is concluded that although the current energy sources are diversified, the most valued energy sources at present and in the future should be solar energy and ocean, which are infinitely recyclable. This paper will benefit researchers to further understand and study the various aspects of energy recovery. [ABSTRACT FROM AUTHOR]

Marine energy still plays a marginal role in the current global energy scenario, despite the incessant effort by research for more than thirty years in the exploitation of the so-called blue energy. Among the wide range of marine technologies, wave energy harvesting can play a significant role in view of its potential and Oscillating Water Column (OWC) systems, coupled with Wells turbines, can be considered among the most mature wave energy technology. Due to the oscillating nature of the flow rate in this kind of applications, Wells turbines are affected by dynamic stall, which has significant effects in terms of performance, fatigue, noise and structural integrity of the turbine. Actually, during dynamic stall, the Wells turbine experiences evident high frequency torque fluctuations which overlay on the typical hysteresis loop, mainly during flow deceleration. The amplitudes of these fluctuations are damped as the flow rate decreases toward reattachment. Often these fluctuations are not evident because hysteresis loops are usually provided with phase-averaged data, which can significantly smoothen or even conceal them. Indeed, it is difficult to find in the literature high frequency torque measurements able to show these fluctuations. With the aim to better investigate how the stall triggers this phenomenon, a monoplane Wells turbine has been manufactured in 3D printing and tested in the open wind tunnel of the Polytechnic University of Bari, Italy. The interest of the experimental campaign has been mainly focused on the effects of main parameters of the oscillating inlet flow rate (mean flow rate, amplitude and period of the oscillations, modifying the controlling parameters of the inverter driving the squirrel cage blower) on the performance of the machine. The machine has been firstly investigated under steady state inlet flow conditions, then under dynamic stall conditions. As a result, unsteady torque fluctuations occur during the flow deceleration till the flow reattachment. After the stall, the investigated Wells turbine experiences a drastic reduction of the torque coefficient of about 90%. Moreover, the torque coefficient shows a number of peaks during deceleration phases ranging from 2 to 4. Specifically, the case with the maximum period of the flow rate under investigation (i.e., T = 20 s) shows a greater number of peaks (4) than those related to the other cases (3). Moreover, it has been found that this unsteady behavior is due neither to the mass flow rate crossing the turbine, nor to the stagnation pressure drop, nor to the rotational speed control, which is correctly performed keeping the rotational speed within 1% of the target value. Hence, detecting these oscillations can be relevant in the turbine design phase to enhance the structural strength of the turbine. [ABSTRACT FROM AUTHOR]

The San Juan archipelago lies along the axis of tidal movement between Straits of Juan de Fuca and Strait of Georgia in the Salish Sea. The amplitude of the tidal exchange produces significant tidal currents between the islands, as well as in Rosario Strait to the east and Haro Strait to the west. These currents are of interest as a future source of electrical power generation, given the archipelago's dependence on electricity supply by a subsea cable from the United States mainland. Here, we evaluate the tidal current energy potential in this region through a re-analysis of measurements collected by the National Ocean Service (NOS) and a high-resolution numerical model. Given the considerable variations in water depth and vertical velocity profiles across candidate tidal energy sites, we consider the trade-offs between tidal turbines deployed from a floating platform and those anchored to the seabed. Measurement re-analysis indicates several locations that could support tidal current power generation by MW-scale turbines with an acceptable balance between turbine size, rated power, and capacity factor. Even for relatively large (30 m) turbine diameters, surface-deployed turbines would be expected to produce up to 30 % more electricity than the same turbine deployed near the seabed due to vertical shear, with this difference increasing for smaller diameter turbines. As anticipated for sparse measurements, the regional simulation identifies several locations with power generation potential more than twice as high as locations in the measurement re-analysis. These sites were either not surveyed or excluded due to data quality issues. A benchmark comparison at the measurement locations with the highest power generation potential shows relatively good model fidelity, though time-average power density disagreements of ± 50 % persist throughout the water column. In addition to the case study, we also treat three general considerations for measurement data: (1) the accuracy of energy generation estimates from hub height speed relative to rotor-averaged power density, (2) the feasibility of extrapolating profiles towards the surface and seabed, and (3) trends in energy generation with rotor size and position in the water column. Overall, these results demonstrate that models and measurements can be used in a complementary manner for tidal energy site assessment and that tidal currents could be an important source of electricity generation in the San Juan archipelago. • Locations in the San Juan archipelago could support tidal current power generation. • Turbines near the surface produce 30 % more power than those near the seabed. • Simulations indicate sites with more than 2x generation of those with measurements. • Hub-height speed is a good approximation for rotor-averaged kinetic power density. • Tangent or power law fits can be used to extrapolate measurements, when needed. [ABSTRACT FROM AUTHOR]

Marine energy (ME) has the potential to power businesses in the blue economy. Kelp farms are an emerging maritime market of the blue economy and are predicted to grow, but they are not currently using ME for their power needs. As the number and size of kelp farms increase, more offshore power will be needed onsite for operations, monitoring, and harvesting. ME devices such as tidal current energy converters and wave energy converters (WECs) may be used to supply power for these needs. This article assesses the status of kelp farming in the continental United States, investigates the electricity needs of kelp farms, and examines the feasibility of generating the required electricity from wave and tidal current energy. The United States currently has 165 kelp farms that have either active or pending permits. The farms use electricity for boat operations, kelp drying, environmental monitoring, offshore lighting, and the raising and lowering of lines. Most kelp farms are in protected, nearshore waters that do not have significant wave energy resources. The limited available wave energy could be used to power small devices, but WECs have not yet been developed for that application. Some kelp farms are in locations that feature significant tidal energy resources, but small tidal current energy converters that are compatible with existing farm operations are not yet commercially available. As low-power WECs and tidal current energy converters are developed, kelp farms could be research partners and early adopters of the new technologies, which would encourage their broader use by other blue economy businesses. [ABSTRACT FROM AUTHOR]

The transient acceleration of ocean currents, or internal waves, is hard to detect, because it does not have climate variability or regular manifestation in the sea. This fluctuation affects not only short-term oceanographic processes but also the hydrokinetic generation of power and the structural health of ocean technologies. Identifying and understanding the mechanisms that generate internal waves require long-term data on the kinetic and viscous–turbulent parameters of the water column measured over long intervals. In this sense, this study analyzed current profiles in nearshore waters (8.9 m depths) measured over six months in the Colombian Caribbean Sea and found internal waves due to the manifestation of transient acceleration propagating in two of the three layers of the water column. The analyzed time series of currents and turbulent kinetic profiles evidenced that transient waves occurred during changes in the surface winds. The applied methodology in this research allowed, for the first time in the study area, the detection of transient accelerations (±0.25 m/s2) that modified the hydrokinetic energy of the water column over short-term periods (6–24 h). [ABSTRACT FROM AUTHOR]

The lagoon is a natural system protected from the sea by a dune barrier creating energy from the movement of rising and falling tides, thus providing a sustainable option for extracting energy from tidal currents. The energy that can be extracted is one of the most potential renewable energy sources. Therefore, the interaction of tidal currents with stratification layers has become important to optimize the efficiency of energy conversion at each depth layer in water masses. We have chosen as a case study, the Oualidia lagoon (Atlantic coast of Morocco). This ecosystem is characterized by hydrodynamics relatively favored by tides and tidal currents which are the main intra-lagoon currents, with a predominance of the semi-diurnal component M2 (period of 12 h 25) with 2.1 to 3.4 m of tidal range. The Multicell Argonaut-XR ADCP is used to measure the current velocity in the Oualidia lagoon at three different stations to study tidal patterns in a vertical layer of water depth. At each station, current velocities were recorded in each 0.5 m layer over a depth of about 5 m. As a result, this study showed that current velocity measurements to be used as renewable energy are found at station 1 located at a depth of 3.5 meters (~layer 5) with a current velocity of 0.771 m/s and a power density value of 235.344 W/m², station 2 located at a depth of 3.5 meters (~layer 5) with a current velocity of 0.4 m/s and a power density value of 32.86 W/m² and station 3 is located at a depth of 3 meters (~layer 6) with a current velocity of 0.527 m/s and a power density value of 75.157 W/m². The variation in current velocities between the different stations is mainly influenced by tides (Flood/ebb), the period of the measurements and the location of the stations. This work presents a model for extracting electrical energy through the use of tidal and current flow variations in such semi-enclosed natural system including lagoons. [ABSTRACT FROM AUTHOR]

With Malaysia being surrounded by water bodies, tidal energy could be used for energy extraction. While several turbine designs and technologies have been used for tidal energy extraction, information on the use of vertical-axis tidal turbines (VATTs) for shallow-water applications is scarce. However, implementing horizontal-axis tidal turbines (HATTs) is not feasible due to Malaysian ocean depths. Hence, examining the wake-flow characteristics of VATTs in a shallow water-working environment in Malaysia is essential. The wake turbulence of the Savonius turbine model was compared with that of a hypothetical ‘actuator' cylinder, a VATT representation. Subsequently, the wake turbulences of a Savonius turbine model in static and dynamic simulations were compared to understand the flow distinction. Compared with that exhibited by the hypothetical actuator cylinder of 2.5 m, the hypothetical actuator cylinder of 5 m exhibits greater velocity deceleration. Additionally, the modelled Savonius turbine exhibits significantly more deceleration than that exhibited by the hypothetical actuator cylinder. Finally, the analysis of the static model of the Savonius turbine shows deceleration that is greater than that of the dynamic model.

Copyright of Constelaciones (2340-177X) is the property of Fundacion Universitaria San Pablo - CEU and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The marine energy (ME) industry historically lacked a standardized data processing toolkit for common tasks such as data ingestion, quality control, and visualization. The marine and hydrokinetic toolkit (MHKiT) solved this issue by providing a public software deployment (open-source and free) toolkit for the ME industry to store and maintain commonly used functionality for wave, tidal, and river energy. This paper demonstrates an initial model verification study in MHKiT. Using Delft3D, a numerical model of the Tanana River Test Site (TRTS) at Nenana, Alaska was created. Field data from the site was collected using an Acoustic Doppler Current Profiler (ADCP) at the proposed Current Energy Converter (CEC) locations. MHKiT is used to process model simulations from Delft3D and compare them to the transect data from the ADCP measurements at TRTS. The ability to use a single tool to process simulation and field data demonstrates the ease at which the ME industry can obtain results and collaborate across specialties, reducing errors and increasing efficiency. [ABSTRACT FROM AUTHOR]

Northern Ireland aims to achieve 1 GW of offshore wind power by 2030 to reduce energy carbon intensity. However, the region faces challenges hindering offshore wind development, including political and geographical constraints. This study investigates these challenges and opportunities, focusing on the technical and innovative aspects of offshore wind deployment in Northern Ireland. Methodologically, the study employs advanced spatial analysis techniques to assess water depths, vessel density, seabed substrate, and wind resource estimation. It also conducts a multi-criteria analysis to integrate various parameters and identify optimal locations for different turbine foundation types. By analyzing the regions 6500 km2 sea area, this research identifies significant depth and spatial constraints due to marine conservation legislation, shipping, and fishing activities. Despite these obstacles, the study unveils promising prospects for offshore wind generation, with potential capacities exceeding 1 GW for fixed-bottom installations and far larger capacities for floating offshore wind projects across multiple areas. Furthermore, the analysis underscores the complexity of offshore wind project development in Northern Ireland, highlighting the necessity for innovative solutions and strategic site selection to navigate environmental, economic, and social challenges effectively. Northern Ireland exhibits notable potential for offshore wind energy development, particularly through the adoption of floating foundations, which are better suited to the region's deep-water conditions. • Potential for fixed-bottom offshore wind generation above 1 GW with significantly larger floating capacity potential. • Severe depth change from shallow to deep creates limited potential for deeper water fixed bottom developments. • Small but diverse regions demonstrates significant constraints, both geological and human created. • Wind resource varies significantly across the region, with near shore and shallow sites having substantially lower capacity factors. [ABSTRACT FROM AUTHOR]