Marine Renewable Energy Seascape

Energy production based on fossil fuel reserves is largely responsible for carbon emissions, and hence global warming. The planet needs concerted action to reduce fossil fuel usage and to implement carbon mitigation measures. Ocean energy has huge potential, but there are major interdisciplinary problems to be overcome regarding technology, cost reduction, investment, environmental impact, governance, and so forth. This article briefly reviews ocean energy production from offshore wind, tidal stream, ocean current, tidal range, wave, thermal, salinity gradients, and biomass sources. Future areas of research and development are outlined that could make exploitation of the marine renewable energy （MRE） seascape a viable proposition; these areas include energy storage, advanced materials, robotics, and informatics. The article concludes with a sustainability perspective on the MRE seascape encompassing ethics, leg- islation, the regulatory environment, governance and consenting, economic, social, and environmental constraints. A new generation of engineers is needed with the ingenuity and spirit of adventure to meet the global challenge posed by MRE.

Optimization of Wind-Marine Hybrid Power System Configuration Based on Genetic Algorithm

Multi-energy power systems can use energy generated from various sources to improve power generation reliability.This paper presents a cost-power generation model of a wind-tide-wave energy hybrid power system for use on a remote island,where the configuration is optimized using a genetic algorithm.A mixed integer programming model is used and a novel object function,including cost and power generation,is proposed to solve the boundary problem caused by existence of two goals.Using this model,the final optimized result is found to have a good fit with local resources.

Enhancing the Performance of the Marine and Tidal Current Converters Using DC-DC Boost Converter

Due to the highly demand on the renewable energy sources as a free and a clean power resource, extracting energy from unsteady flow using marine and tidal current turbines has a distinct focusing nowadays. For their resource characteristic, extracting energy from marine/tidal current needs a simple and robust converter, which could overcome the drawbacks of the mechanical system such as gearbox and enhance conversion system stability. In this paper a new AC-DC-AC conversion system has been proposed. The new conversion system contains a middle stage DC-DC boost converter, which boost the generated rectified DC voltage higher enough that can enable the PWM inverter to generate the required voltage with the synchronized frequency. In order to investigate the efficient performance of the proposed conversion system especially at low current speed compared to the conventional one, different operating conditions have been studied. Moreover, the effect of including boost converter on the THD （total harmonic distortion） has also been checked. The new conversion system presents its capability to enhance and improve system performance not only with low current speed but also with high current speed.

Preface for Special Issue on“Key Mechanical Problems of Marine Energy Development Equipment”

There are abundant energy reserves such as oil,natural gas,hydrate,and wind energy in the ocean.Countries around the globe are competing to advance their marine energy development technologies.The exploitation of marine resources relies on cutting-edge industrial equipment.After decades of R&D endeavors,China has obtained most of the key technologies for the design,production,testing,and field application of marine energy development equipment(Xie and Zeng,2021).

Numerical Investigation of Flow Motion and Performance of A Horizontal Axis Tidal Turbine Subjected to A Steady Current

Horizontal axis tidal turbines have attracted more and more attentions nowadays, because of their convenience and low expense in construction and high efficiency in extracting tidal energy. The present study numerically investigates the flow motion and performance of a horizontal axis tidal turbine with a supporting vertical cylinder under steady current. In the numerical model, the continuous equation and incompressible Reynolds-averaged Navier-Stokes equations are solved, and the volume of fluid method is employed to track free surface motion. The RNG k-ε model is adopted to calculate turbulence transport while the fractional area/volume obstacle representation method is used to describe turbine characteristics and movement. The effects of installation elevation of tidal turbine and inlet velocity on the water elevation, and current velocity, rotating speed and resultant force on turbine are discussed. Based on the comparison of the numerical results, a better understanding of flow structure around horizontal axis tidal turbine and turbine performance is achieved.

A bibliometric review on the implications of renewable offshore marine energy development on marine species

The growing global demand for sustainable and environmentally friendly energy has stimulated the rapid adoption of renewable offshore energy.However,infrastructure needed for green energy production ironically impacts upon marine species and biodiversity.Consequently,this positional review paper seeks to comprehensively synthesise the prevailing body of knowledge on the impact of offshore energy development on a broad range of marine species.An interpretivist philosophical stance and inductive reasoning was adopted using scientometric analysis to conduct a rich synthesis of extant literature.From an operational perspective,the Scopus database was utilised to search for key terms on the phenomena under investigation and using the VoS Viewer software for the identification of trends using scientometric maps.The analysis reveals that research in this area of science has increased significantly over the last decade but private sector involvement is conspicuous by its absence.Primary concerns among the research community include the impact of energy development on the abundance of species,pollution and biodiversity behaviour and migration.At present,researchers have extensively focused on the impact of offshore wind farms on fish and marine mammals.However,the literature reveals no significant long-term impact upon energy development on most marine species albeit,short-term interference has raised concerns(from sound,disruption of navigation and foraging patterns,and damage of habitat).To minimise short term disruption,researchers have recommended the use of acoustic deterrence during construction,enforcement of protected areas and continued research.

Which variables are essential for renewable energies?

Essential Variables are defined as a minimal set of variables that explain the state of the system.They are crucial for predicting its developments,and support metrics that measure its evolution.The variables should be relevant to meet requirements of stakeholders and be technically and economically feasible for systematic observation.A definition of Essential Renewable Energies Variables is proposed linked with their identification in several domains in renewable energy using a bottom-up and userdriven approach,and spanning over several years of documented interaction with stakeholders.Lists of variables are proposed in hydropower,solar,wind,and marine energies.It does not comprise the variables relating to social and economic aspects supporting decision making in investment nor those relating to civil engineering that are needed to erect a plant or farm.

EMCO-based Optimal Layout Design of Hybrid Wind-wave Energy Converters Array

Marine renewable energy,combining wave energy converters(WECs)and floating wind turbines(FWTs)into hybrid wave-wind energy converters(HWWECs),garners significant global interest.HWWECs offer potential cost reductions,increased power generation,and enhanced system stability.The absorption power of high wind energy sites is primarily influenced by the complex hydrodynamic interactions among floating bodies,which are closely related to the location and wind-wave environment of high wind energy sites.To delve into the positive interactions among HWWECs,this paper proposes a HWWEC array optimization strategy based on the artificial ecosystem opti-mization-manta ray foraging optimization coordinated optimizer(EMCO).In EMCO,the decomposition operator of artificial ecosystem optimization(AEO)and the flipping-dipper foraging operator of manta ray foraging optimization coordinated(MRFO)cooperate dynamically to effectively balance local exploitation and global exploration.To validate the effectiveness of EMCO,experiments were conducted in scenarios with 3,5,8,and 20 HWWECs,and compared with five typical algorithms.Experimental results demonstrate the existence of multiple optimal solutions for HWWEC arrays.EMCO achieves maximum total absorp-tion power and exhibits good stability.Notably,EMCO en-hances the q-factor values of HWWECs across four scales:1.0478,1.0586,1.0612,and 0.9965,respectively.