Wave energy is one of the most abundant renewable clean energy sources,and has been widely studied because of its advantages of continuity and low seasonal variation.However,its low capture efficiency and narrow captu...Wave energy is one of the most abundant renewable clean energy sources,and has been widely studied because of its advantages of continuity and low seasonal variation.However,its low capture efficiency and narrow capture frequency bandwidth are still technical bottlenecks that restrict the commercial application of wave energy converters(WECs).In recent years,using a nonlinear stiffness mechanism(NSM)for passive control has provided a new way to solve these technical bottlenecks.This literature review focuses on the research performed on the use of nonlinear mechanisms in wave energy device utilization,including the conceptual design of a mechanism,hydrodynamic models,dynamic characteristics,response mechanisms,and some examples of experimental verification.Finally,future research directions are discussed and recommended.展开更多
Electric field is the energy foundation of the electrolysis process and the source of the multiphysical fields in a magnesium electrolysis cell. In this study, a three-dimensional numerical model was developed and use...Electric field is the energy foundation of the electrolysis process and the source of the multiphysical fields in a magnesium electrolysis cell. In this study, a three-dimensional numerical model was developed and used to calculate electric field at the steady state through the finite element analysis. Based on the simulation of the electric field, the operational and structural parameters, such as the current intensity, anode thickness, cathode thickness, and anode-cathode distance （ACD）, were investigated to obtain the minimum cell voltage. The optimization is to obtain the minimum resistance voltage which has a significant effect on the energy consumption in the magnesium electrolysis process. The results indicate that the effect of the current intensity on the voltage could be ignored and the effect of the ACD is obvious. Moreover, there is a linear decrease between the voltage and the thicknesses of the anode and cathode; and the anodecathode working height also has a significant effect on the voltage.展开更多
Thermal energy is at the heart of the whole energy chain providing a main linkage between the primary and secondary energy sources. Thermal energy storage （TES） has a pivotal role to play in the energy chain and hen...Thermal energy is at the heart of the whole energy chain providing a main linkage between the primary and secondary energy sources. Thermal energy storage （TES） has a pivotal role to play in the energy chain and hence in future low carbon economy. However, a competitive TES technology requires a number of scientific and technological challenges to be addressed including TES materials, TES components and devices, and integration of TES devices with energy networks and associated dynamic optimization. This paper provides a perspective of TES technology with a focus on TES materials challenges using molten salts based phase change materials for medium and high temperature applications. Two key challenges for the molten salt based TES materials are chemical incompatibility and low thermal conductivity. The use of composite materials provides an avenue to meeting the challenges. Such composite materials consist of a phase change material, a structural supporting material, and a thermal conductivity enhancement material. The properties of the supporting material could determine the dispersion of the thermal con- ductivity enhancement material in the salt. A right combination of the salt, the structural supporting material, and the thermal conductivity enhancement material could give a hierarchical structure that is able to encapsulate the molten salt and give a substantial enhancement in the thermal conductivity. Understanding of the structure-property relationships for the composite is essential for the formulation design and fabrication of the composite materials. Linking materials properties to the system level performance is recommended as a key future direction of research.展开更多
Due to the inference of the uneven shallow water seabed and the surrounding islands,the wind-generated waves around or in a reef lagoon are rather complicated,and critical to the safety of floating structures deployed...Due to the inference of the uneven shallow water seabed and the surrounding islands,the wind-generated waves around or in a reef lagoon are rather complicated,and critical to the safety of floating structures deployed near islands or inside a lagoon.This paper aims to find a feasible analysis tool for the wave simulations near islands and reefs.The proposed three methods of grid techniques of WAVEWATCH III(WW3)are assessed by using on-site measured data which was collected and accumulated for about 5 years since August 2014 by a wave observation system deployed inside and outside a reef lagoon in South China Sea.In the assessments,the wave statistics including the correlation coefficients,root mean square errors,and their variances are used to quantify the precisions of the simulation results of the significant wave heights,mean wave periods,and peak wave directions at two sites.Among the three methods,the Multi-scale Zone and Multi-scale grid Technique(MZMGT)established on unstructured triangular grids exhibits better results in terms of the accuracy and CPU cost.In addition,the bimodal feature of wave spectra was observed at both sites of the reef lagoon in different typhoon events.The wave characteristics inside the reef lagoon and open sea are also analyzed.展开更多
A mooring system has been designed for the position keeping of a two-module semi-submersible platform which is connected by hinge-type connectors.Under the excitation of ocean waves,the relative motion between the two...A mooring system has been designed for the position keeping of a two-module semi-submersible platform which is connected by hinge-type connectors.Under the excitation of ocean waves,the relative motion between the two modules can be significant.It is therefore no longer adequate to model the platform as a single rigid body in the analysis of the performance of the mooring system.In this study,an analysis method has been developed based on the three-dimensional frequency domain hydroelasticity theory in conjunction with the time domain quasi-static analysis method of mooring actions,which takes into account of the coupling effect of the platform motion and mooring tension.The proposed method is verified by comparing the numerical results with the measured data obtained from the on-site measurements.The comparison shows a good agreement,and demonstrates the feasibility and effectiveness of the proposed method for the analysis of the module responses and mooring tensions of multi-module floating platforms.展开更多
The characteristics of the waves around a lagoon entrance in South China Sea were observed during the past one and half years based on the wave measurements.The measured results show that the monsoon plays an importan...The characteristics of the waves around a lagoon entrance in South China Sea were observed during the past one and half years based on the wave measurements.The measured results show that the monsoon plays an important role.In summer,waves mostly come from the southeast,among which the wave components of non-dimensional periods larger than 0.2 are fetch-trapped waves.In winter the waves may be divided into two groups,the fetch-trapped waves and the waves from the open sea.The skewness of the directional distribution functions is within+8 around zero.The power relationship between the direction spread and kurtosis is also investigated.Besides,it is found that the waves with the significant wave heights greater than 1.5 m are caused by typhoons or cold air.The frequency components of wave energy driven by cold air appear in the high frequency range at first,and change to the lower frequency range afterwards.The waves driven by typhoon mostly come from the open sea.展开更多
基金Project(2011AA06A107)supported by the National High Technology Research and Development Program of ChinaProject(2014M551348)supported by China Postdoctoral Science FoundationProject(51504098)supported by the National Natural Science Foundation of China
基金financial supports from the National Natural Science Foundation of China (No. 51801078)the Natural Science Foundation of Jiangsu Province, China (No. BK20180986)。
基金the State Key Laboratory of Coastal and Offshore Engineering of China(No.LP2019)the 2020 Research Program of Sanya Yazhou Bay Science and Technology City of China(No.SKJC-2020-01-006)+1 种基金the Hainan Provincial Natural Science Foundation of China(No.520QN290)the High-tech Ship Research Projects Sponsored by MIIT of China(No.[2019]357)。
文摘Wave energy is one of the most abundant renewable clean energy sources,and has been widely studied because of its advantages of continuity and low seasonal variation.However,its low capture efficiency and narrow capture frequency bandwidth are still technical bottlenecks that restrict the commercial application of wave energy converters(WECs).In recent years,using a nonlinear stiffness mechanism(NSM)for passive control has provided a new way to solve these technical bottlenecks.This literature review focuses on the research performed on the use of nonlinear mechanisms in wave energy device utilization,including the conceptual design of a mechanism,hydrodynamic models,dynamic characteristics,response mechanisms,and some examples of experimental verification.Finally,future research directions are discussed and recommended.
基金Acknowledgements We thank the financial support provided by the National Natural Science Foundation of China （Grant Nos. 21206038 and 51504099）, the Specialized Research Fund for the Doctoral Program of Higher Education （New Teachers） （Grant No. 20120074120014）, and the Fundamental Research Funds for the Central Universities.
文摘Electric field is the energy foundation of the electrolysis process and the source of the multiphysical fields in a magnesium electrolysis cell. In this study, a three-dimensional numerical model was developed and used to calculate electric field at the steady state through the finite element analysis. Based on the simulation of the electric field, the operational and structural parameters, such as the current intensity, anode thickness, cathode thickness, and anode-cathode distance （ACD）, were investigated to obtain the minimum cell voltage. The optimization is to obtain the minimum resistance voltage which has a significant effect on the energy consumption in the magnesium electrolysis process. The results indicate that the effect of the current intensity on the voltage could be ignored and the effect of the ACD is obvious. Moreover, there is a linear decrease between the voltage and the thicknesses of the anode and cathode; and the anodecathode working height also has a significant effect on the voltage.
基金supported by a Focused Deployment Project of Chinese Academy of Sciences(KGZD-EW-302-1)Key Technologies R&D Program of China(No.2012BAA03B03)UK EPSRC under grants EP/F060955/1 and EP/L014211/1
文摘Thermal energy is at the heart of the whole energy chain providing a main linkage between the primary and secondary energy sources. Thermal energy storage （TES） has a pivotal role to play in the energy chain and hence in future low carbon economy. However, a competitive TES technology requires a number of scientific and technological challenges to be addressed including TES materials, TES components and devices, and integration of TES devices with energy networks and associated dynamic optimization. This paper provides a perspective of TES technology with a focus on TES materials challenges using molten salts based phase change materials for medium and high temperature applications. Two key challenges for the molten salt based TES materials are chemical incompatibility and low thermal conductivity. The use of composite materials provides an avenue to meeting the challenges. Such composite materials consist of a phase change material, a structural supporting material, and a thermal conductivity enhancement material. The properties of the supporting material could determine the dispersion of the thermal con- ductivity enhancement material in the salt. A right combination of the salt, the structural supporting material, and the thermal conductivity enhancement material could give a hierarchical structure that is able to encapsulate the molten salt and give a substantial enhancement in the thermal conductivity. Understanding of the structure-property relationships for the composite is essential for the formulation design and fabrication of the composite materials. Linking materials properties to the system level performance is recommended as a key future direction of research.
基金supported by the Ministry of Industry and Information Technology(Grant Nos.[2016]22,[2019]357)supported by the Ministry of Science and Technology(Grant No.2013CB36100)+3 种基金the National Key Research and Development Programof China(Grant No.2017YFB0202701)the Jiangsu Province Science Foundation for Youths(Grant No.BK20190151)the Natural Science Foundation of Hunan Province(Grant No.2019JJ50633)the Southern Marine Science and Engineering Guangdong Laboratory(Zhanjiang)(Grant No.ZJW-2019-08).
文摘Due to the inference of the uneven shallow water seabed and the surrounding islands,the wind-generated waves around or in a reef lagoon are rather complicated,and critical to the safety of floating structures deployed near islands or inside a lagoon.This paper aims to find a feasible analysis tool for the wave simulations near islands and reefs.The proposed three methods of grid techniques of WAVEWATCH III(WW3)are assessed by using on-site measured data which was collected and accumulated for about 5 years since August 2014 by a wave observation system deployed inside and outside a reef lagoon in South China Sea.In the assessments,the wave statistics including the correlation coefficients,root mean square errors,and their variances are used to quantify the precisions of the simulation results of the significant wave heights,mean wave periods,and peak wave directions at two sites.Among the three methods,the Multi-scale Zone and Multi-scale grid Technique(MZMGT)established on unstructured triangular grids exhibits better results in terms of the accuracy and CPU cost.In addition,the bimodal feature of wave spectra was observed at both sites of the reef lagoon in different typhoon events.The wave characteristics inside the reef lagoon and open sea are also analyzed.
基金supported by the National Key Research and Development Program of China(Grant No.2017YFB0202701)the Ministryof Industry and Information Technology(Grant Nos.[2016J22,[2019J357)+2 种基金supported by the State Key Fundamental Research Program(Grant No.2013CB036100)the Jiangsu Province Science Foundation for Youths(Grant No.BK20190151)the Fund of Southern Marine Science and Engineering Guangdong Laboratory(Zhanjiang)(Grant No.ZJW-2019-02).
文摘A mooring system has been designed for the position keeping of a two-module semi-submersible platform which is connected by hinge-type connectors.Under the excitation of ocean waves,the relative motion between the two modules can be significant.It is therefore no longer adequate to model the platform as a single rigid body in the analysis of the performance of the mooring system.In this study,an analysis method has been developed based on the three-dimensional frequency domain hydroelasticity theory in conjunction with the time domain quasi-static analysis method of mooring actions,which takes into account of the coupling effect of the platform motion and mooring tension.The proposed method is verified by comparing the numerical results with the measured data obtained from the on-site measurements.The comparison shows a good agreement,and demonstrates the feasibility and effectiveness of the proposed method for the analysis of the module responses and mooring tensions of multi-module floating platforms.
基金supported by the Ministry of Industry and Information Technology(Grant Nos.[2016]22,[2019]357)supported by the Fund of Southern Marine Science and Engineering Guangdong Laboratory(Zhanjiang)(Grant Nos.ZJW-2019-02,ZJW-2019-08)the Jiangsu Province Science Foundation for Youths(Grant No.351510008K0708LA00).
文摘The characteristics of the waves around a lagoon entrance in South China Sea were observed during the past one and half years based on the wave measurements.The measured results show that the monsoon plays an important role.In summer,waves mostly come from the southeast,among which the wave components of non-dimensional periods larger than 0.2 are fetch-trapped waves.In winter the waves may be divided into two groups,the fetch-trapped waves and the waves from the open sea.The skewness of the directional distribution functions is within+8 around zero.The power relationship between the direction spread and kurtosis is also investigated.Besides,it is found that the waves with the significant wave heights greater than 1.5 m are caused by typhoons or cold air.The frequency components of wave energy driven by cold air appear in the high frequency range at first,and change to the lower frequency range afterwards.The waves driven by typhoon mostly come from the open sea.
