Integrating wave energy converters(WECs)with offshore platforms offers numerous advantages,such as reducing wave loads,supplying energy to the platform,and cost-sharing in construction.This paper reports an experiment...Integrating wave energy converters(WECs)with offshore platforms offers numerous advantages,such as reducing wave loads,supplying energy to the platform,and cost-sharing in construction.This paper reports an experimental investigation focusing on the hydrodynamic characteristics of a proposed modular floating structure system integrated with WEC-type floating artificial reefs.The proposed system comprises several serially arranged hexagonal floating structures,anchored by tension legs,and integrated with outermost WEC-type floating artificial reefs.A simplified wave energy converter utilizing the relative pitch motion between adjacent modules for energy conversion was constructed in the scale model test.The effects of chain-type modular expansion on the multi-body motion response,mooring tension response,and WEC performance of the system have been thoroughly investigated.The experimental results indicate that increasing the number of hexagonal modules can notably reduce the system’s surge response,particularly under survival sea conditions.The connection of the outermost reef modules slightly increases the tension leg load of the adjacent module,whereas the tension leg load remains relatively consistent across the inner hexagonal modules.Furthermore,through a comparison of the dynamic responses of the hexagonal module connected and unconnected outermost reefs,the good performance in terms of energy conversion and wave attenuation of the WECtype floating artificial reef modules was effectively validated.The main results from this work can provide useful references for engineering applications involving modular floating structures integrated with WECs.展开更多
This paper provides a systematic analysis of the large scale PMsG(permanent magnet synchronous generator)-based WECS(wind energy conversion system)torsional vibration problem under MPPT(maximum power point tracking)co...This paper provides a systematic analysis of the large scale PMsG(permanent magnet synchronous generator)-based WECS(wind energy conversion system)torsional vibration problem under MPPT(maximum power point tracking)control and constant power control.This is from the perspective of SSo(sub-synchronous oscillation),SSH(sub-syn-chronous harmonics)and forced torsional vibration.The cause of SsO is the negative total system damping,weak-ened by the constant power control.The system is susceptible to inducing SSH in the grid current and voltage in the under-damped condition.To effectively suppress the torsional vibration of PMSG-based WECS,a stiffness compensa-tion control strategy based on adaptive damping is proposed.The results show that SSo,SSH and the forced torsional vibration can be suppressed at the source using the proposed suppression strategy.展开更多
Sub-surface crack networks in areas of altered microstructure are a common cause for bearing failures.Due to its appearance under light microscopy,the damage pattern is referred to as White Etching Cracks(WEC).The roo...Sub-surface crack networks in areas of altered microstructure are a common cause for bearing failures.Due to its appearance under light microscopy,the damage pattern is referred to as White Etching Cracks(WEC).The root causes leading to the formation of WEC are still under debate.Nevertheless,it has already been shown that atomic hydrogen can have an accelerating effect on the formation and propagation of WEC.In addition to hydrogen pre-charging,hydrogen can be released and absorbed during rolling/sliding due to the decomposing of the lubricant and water.The current work focuses on the analysis of the hydrogen content of cylindrical roller thrust bearings after testing in a FE8 type test rig using two different lubricants.Within the framework of this work,two different hydrogen analysis methods were used and assessed regarding their applicability.The results show that the so-called Hydrogen Collecting Analysis(HCA)is more suitable to investigate the correlation between lubricant chemistry and hydrogen content in the test bearings than the Local Hydrogen Analysis(LHA).The measurements with the HCA show a continuously increasing freely movable and diffusible hydrogen content under tribological conditions,which leads to the formation of WEC.Comparative tests with an oil without hydrogen showed that the tendency of the system to fail as a result of WEC can be reduced by using a lubricant without hydride compounds.展开更多
1 Introduction With the continuous increase in global population,the demand for energy is upgrading at an unprecedented rate.At present,fossil fuels dominate the global energy landscape,but their limitations lay the g...1 Introduction With the continuous increase in global population,the demand for energy is upgrading at an unprecedented rate.At present,fossil fuels dominate the global energy landscape,but their limitations lay the groundwork for the upcoming global energy crisis[1].The non renewable nature of fossil fuels,coupled with increasing energy consumption,poses a significant threat to the long-term energy security of the world.In addition,the combustion of fossil fuels releases a large amount of air pollutants such as carbon dioxide and sulfur dioxide,leading to serious environmental pollution and climate change.These environmental issues have far-reaching impacts,including rising sea levels,extreme weather events,and loss of biodiversity[2–4].展开更多
Lignite provides energy security and contributes economically.However,it also causes dirty outcomes in terms of climate aspect.In addition to the energy and climate dimensions of the Sustainable Development Goals,ther...Lignite provides energy security and contributes economically.However,it also causes dirty outcomes in terms of climate aspect.In addition to the energy and climate dimensions of the Sustainable Development Goals,there is also a water issue:lignite is usually found submerged below the local groundwater tables.Mining lignite could be exploited to achieve drinkable and agriculturally usable water.In today’s literature,while the impact of lignite production on global warming and emissions are already highly discussed,the water management side of the issue is regularly omitted.However,considering the complex interlink between these three areas(the Water-Energy-Climate(WEC)nexus)is necessary within policy coherence,which is mostly ignored even though it is one of the development targets.Here in this framework,Turkiye,which aims to reduce its heavy dependency on energy imports,is worth studying because almost all of its coal,the country’s largest fossil resource,is lignite.Therefore,this study examines the WEC nexus related to lignite production and combustion and seeks policy coherence between their outputs in the context of Turkiye’s historical steps to climate change mitigation,specifically oriented with the Paris Agreement.This story expands from the absence of specific development policy objectives to the practicalities of politics and economics.展开更多
Installing annular wave-energy converters(WECs)on the columns of floating wind platforms in the form of a coaxial-cylinder provides a convenient means of integration.Extant coaxial-cylinder-type wind-wave hybrid syste...Installing annular wave-energy converters(WECs)on the columns of floating wind platforms in the form of a coaxial-cylinder provides a convenient means of integration.Extant coaxial-cylinder-type wind-wave hybrid systems are mostly based on single-column platforms such as spars(single coaxial-cylinder hybrid system'hereafter).Systems based on multiple-column platforms such as semi-submersible platforms('multiple coaxial-cylinder hybrid systems'hereafter)are rarely seen or studied,despite their superiority in wave-power absorption due to the use of multiple WECs as well as in dynamic stability.This paper proposes a novel WindFloat-annular-WEC hybrid system,based on our study investigating its dynamic and power features,and optimizing the geometry and power take-off of the WECs.Our results show that the dynamic and power features of a multiple coaxial-cylinder hybrid system are different from those of a single coaxial-cylinder hybrid system,so the same optimization parameters cannot be directly applied.Flatter annular WECs absorb slightly more power in a wider wave-period range,but their geometry is confined by limitations in installation and structural strength.The overall effect of an oblique incident wave is greater intensity in the motions of the hybrid system in yaw and the direction perpendicular to propagation,although the difference is small and maybe negligible.展开更多
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 energ...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.展开更多
基金financially supported by the National Natural Science Foundation of China(Grant No.52161041)the Natural Science Foundation of Hainan Province(Grant No.520RC552).
文摘Integrating wave energy converters(WECs)with offshore platforms offers numerous advantages,such as reducing wave loads,supplying energy to the platform,and cost-sharing in construction.This paper reports an experimental investigation focusing on the hydrodynamic characteristics of a proposed modular floating structure system integrated with WEC-type floating artificial reefs.The proposed system comprises several serially arranged hexagonal floating structures,anchored by tension legs,and integrated with outermost WEC-type floating artificial reefs.A simplified wave energy converter utilizing the relative pitch motion between adjacent modules for energy conversion was constructed in the scale model test.The effects of chain-type modular expansion on the multi-body motion response,mooring tension response,and WEC performance of the system have been thoroughly investigated.The experimental results indicate that increasing the number of hexagonal modules can notably reduce the system’s surge response,particularly under survival sea conditions.The connection of the outermost reef modules slightly increases the tension leg load of the adjacent module,whereas the tension leg load remains relatively consistent across the inner hexagonal modules.Furthermore,through a comparison of the dynamic responses of the hexagonal module connected and unconnected outermost reefs,the good performance in terms of energy conversion and wave attenuation of the WECtype floating artificial reef modules was effectively validated.The main results from this work can provide useful references for engineering applications involving modular floating structures integrated with WECs.
基金supported by Shaanxi Provincial Department of Education Project(17JK0691)。
文摘This paper provides a systematic analysis of the large scale PMsG(permanent magnet synchronous generator)-based WECS(wind energy conversion system)torsional vibration problem under MPPT(maximum power point tracking)control and constant power control.This is from the perspective of SSo(sub-synchronous oscillation),SSH(sub-syn-chronous harmonics)and forced torsional vibration.The cause of SsO is the negative total system damping,weak-ened by the constant power control.The system is susceptible to inducing SSH in the grid current and voltage in the under-damped condition.To effectively suppress the torsional vibration of PMSG-based WECS,a stiffness compensa-tion control strategy based on adaptive damping is proposed.The results show that SSo,SSH and the forced torsional vibration can be suppressed at the source using the proposed suppression strategy.
基金The authors would like to thank the ResearchAssociation for Drive Technology (FVA) for thefunding and support from the research work throughthe research project FVA 707 IV
文摘Sub-surface crack networks in areas of altered microstructure are a common cause for bearing failures.Due to its appearance under light microscopy,the damage pattern is referred to as White Etching Cracks(WEC).The root causes leading to the formation of WEC are still under debate.Nevertheless,it has already been shown that atomic hydrogen can have an accelerating effect on the formation and propagation of WEC.In addition to hydrogen pre-charging,hydrogen can be released and absorbed during rolling/sliding due to the decomposing of the lubricant and water.The current work focuses on the analysis of the hydrogen content of cylindrical roller thrust bearings after testing in a FE8 type test rig using two different lubricants.Within the framework of this work,two different hydrogen analysis methods were used and assessed regarding their applicability.The results show that the so-called Hydrogen Collecting Analysis(HCA)is more suitable to investigate the correlation between lubricant chemistry and hydrogen content in the test bearings than the Local Hydrogen Analysis(LHA).The measurements with the HCA show a continuously increasing freely movable and diffusible hydrogen content under tribological conditions,which leads to the formation of WEC.Comparative tests with an oil without hydrogen showed that the tendency of the system to fail as a result of WEC can be reduced by using a lubricant without hydride compounds.
基金supported by Yunnan Provincial Basic Research Project(202401AT070344)National Natural Science Foundation of China(62263014).
文摘1 Introduction With the continuous increase in global population,the demand for energy is upgrading at an unprecedented rate.At present,fossil fuels dominate the global energy landscape,but their limitations lay the groundwork for the upcoming global energy crisis[1].The non renewable nature of fossil fuels,coupled with increasing energy consumption,poses a significant threat to the long-term energy security of the world.In addition,the combustion of fossil fuels releases a large amount of air pollutants such as carbon dioxide and sulfur dioxide,leading to serious environmental pollution and climate change.These environmental issues have far-reaching impacts,including rising sea levels,extreme weather events,and loss of biodiversity[2–4].
文摘Lignite provides energy security and contributes economically.However,it also causes dirty outcomes in terms of climate aspect.In addition to the energy and climate dimensions of the Sustainable Development Goals,there is also a water issue:lignite is usually found submerged below the local groundwater tables.Mining lignite could be exploited to achieve drinkable and agriculturally usable water.In today’s literature,while the impact of lignite production on global warming and emissions are already highly discussed,the water management side of the issue is regularly omitted.However,considering the complex interlink between these three areas(the Water-Energy-Climate(WEC)nexus)is necessary within policy coherence,which is mostly ignored even though it is one of the development targets.Here in this framework,Turkiye,which aims to reduce its heavy dependency on energy imports,is worth studying because almost all of its coal,the country’s largest fossil resource,is lignite.Therefore,this study examines the WEC nexus related to lignite production and combustion and seeks policy coherence between their outputs in the context of Turkiye’s historical steps to climate change mitigation,specifically oriented with the Paris Agreement.This story expands from the absence of specific development policy objectives to the practicalities of politics and economics.
基金supported by the National Natural Science Foundation of China(Nos.52201322,52222109,and 52071096)the Guangdong Basic and Applied Basic Research Foundation(Nos.2022B1515020036 and 2023A1515012144)the Natural Science Foundation of Guangzhou City(No.202201010055),China.
文摘Installing annular wave-energy converters(WECs)on the columns of floating wind platforms in the form of a coaxial-cylinder provides a convenient means of integration.Extant coaxial-cylinder-type wind-wave hybrid systems are mostly based on single-column platforms such as spars(single coaxial-cylinder hybrid system'hereafter).Systems based on multiple-column platforms such as semi-submersible platforms('multiple coaxial-cylinder hybrid systems'hereafter)are rarely seen or studied,despite their superiority in wave-power absorption due to the use of multiple WECs as well as in dynamic stability.This paper proposes a novel WindFloat-annular-WEC hybrid system,based on our study investigating its dynamic and power features,and optimizing the geometry and power take-off of the WECs.Our results show that the dynamic and power features of a multiple coaxial-cylinder hybrid system are different from those of a single coaxial-cylinder hybrid system,so the same optimization parameters cannot be directly applied.Flatter annular WECs absorb slightly more power in a wider wave-period range,but their geometry is confined by limitations in installation and structural strength.The overall effect of an oblique incident wave is greater intensity in the motions of the hybrid system in yaw and the direction perpendicular to propagation,although the difference is small and maybe negligible.
文摘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.
