The comprehensive optimization of thermodynamic and economic performances is significant for the engineering application of ocean thermal energy conversion(OTEC).Motivated by this,this paper develops a thermo-economic...The comprehensive optimization of thermodynamic and economic performances is significant for the engineering application of ocean thermal energy conversion(OTEC).Motivated by this,this paper develops a thermo-economic OTEC model and conducts a sensitivity analysis of the OTEC system concerning its thermodynamic and economic performances.Specifically,the impact of warm-seawater temperature and cold-seawater pumping depth on the net thermal efficiency and the total investment cost are investigated.The results indicate that,an increase in warm-seawater temperature and cold-seawater pumping depth can improve the net thermal efficiency and a higher installed capacity is beneficial to the system economics.Building on these,a design optimization method with considering the on-design and off-design conditions is proposed in this paper,and the dynamic variation of warm-seawater temperature are considered in this method.In multi-objective optimization procedure,with the objective functions being the average net thermal efficiency and unit power cost within the operational cycle,the non-dominated sorting genetic algorithm Ⅱ(NSGA-Ⅱ) is employed to maximize the net thermal efficiency and minimize the unit power investment cost,resulting in the Pareto front.The net thermal efficiencies of OTEC systems using ammonia and R245fa as working fluids are 4.13% and 3.8%,respectively.This represents an improvement of 19.4% and 57.0%,respectively,compared to traditional optimization methods that do not account for off-design conditions.展开更多
Ocean thermal energy conversion(OTEC)is a renewable energy source that uses differences in ocean water temperature between warm surface and cold depth to generate electricity.It is an essential link in the carbon neut...Ocean thermal energy conversion(OTEC)is a renewable energy source that uses differences in ocean water temperature between warm surface and cold depth to generate electricity.It is an essential link in the carbon neutrality chain and one of the rising sectors of the ocean energy.This paper provides an overview of studies on closed thermodynamic cycles and the numerous difficulties that OTEC technology faces.A description of the thermodynamic cycles incorporating mixed or pure working fluids,as well as the implications of different working fluids on cycle efficiency were also studied.Changes in condensing and evaporating temperatures induced by variations in heat resources affect the efficiency of cycles with pure working fluids.Several strategies,such as intermediate extraction regeneration and heat recovery of ammonia-depleted solution can increase the thermal efficiency with mixed working fluids.In addition,the impact of the ejector on the cycle’s performance is examined.Finally,the efficiency-improving strate-gies are described and summarized.Thermodynamic efficiency can increase using suitable working fluids and taking steps to maximize the rate of ocean thermal energy.To establish which approach is the most effective,different methods have been evaluated and compared under identical operating conditions.展开更多
Ocean thermal energy conversion(OTEC)is a process of generating electricity by exploiting the temperature difference between warm surface seawater and cold deep seawater.Due to the high static and dynamic pressures th...Ocean thermal energy conversion(OTEC)is a process of generating electricity by exploiting the temperature difference between warm surface seawater and cold deep seawater.Due to the high static and dynamic pressures that are caused by seawater circulation,the stiffened panel that constitutes a seawater tank may undergo a reduction in ultimate strength.The current paper investigates the design of stiffening systems for OTEC seawater tanks by examining the effects of stiffening parameters such as stiffener sizes and span-over-bay ratio for the applied combined loadings of lateral and transverse pressure by fluid motion and axial compression due to global bending moment.The ultimate strength calculation was conducted by using the non-linear finite element method via the commercial software known as ABAQUS.The stress and deformation distribution due to pressure loads was computed in the first step and then brought to the second step,in which the axial compression was applied.The effects of pressure on the ultimate strength of the stiffener were investigated for representative stiffened panels,and the significance of the stiffener parameters was assessed by using the sensitivity analysis method.As a result,the ultimate strength was reduced by approximately 1.5%for the span-over-bay ratio of 3 and by 7%for the span-over-bay ratio of 6.展开更多
The tremendous amount of wasted heat from solar radiation and industry dissipation has motivated the development of thermoelectric concepts that directly convert heat into electricity.The main challenge in practical a...The tremendous amount of wasted heat from solar radiation and industry dissipation has motivated the development of thermoelectric concepts that directly convert heat into electricity.The main challenge in practical applications for thermoelectrics is the high cost from both materials and manufacturing.Recently,breakthrough progresses in ionic thermoelectrics open up new possibilities to charge energy storage devices when submitted to a temperature gradient.The charging voltage is internally from the ionic Seebeck effect of the electrolyte between two electrodes.Hence electrolytes with high thermoelectric figure of merit are classified as ionic thermoelectric materials.Most ionic thermoelectric materials are composed of abundant elements,and they can generate hundreds of times larger thermal voltage than that of electronic materials.This emerging thermoelectric category brings new hope to fabricate low cost and large area heat-to-energy conversion devices,and triggers a renewed interest for ionic thermodiffusion.In this review,we summarize the state of the art in the new field of ionic thermoelectrics,from the driving force of the ionic thermodiffusion to material and application developments.We present a general map of ionic thermoelectric materials,discuss the unique characters of each type of the reported electrolytes,and propose potential optimization and future topics of ionic thermoelectrics.展开更多
With the global ambition of moving towards carbon neutrality,this sets to increase significantly with most of the energy sources from renewables.As a result,cost-effective and resource efficient energy conversion and ...With the global ambition of moving towards carbon neutrality,this sets to increase significantly with most of the energy sources from renewables.As a result,cost-effective and resource efficient energy conversion and storage will have a great role to play in energy decarbonization.This review focuses on the most recent developments of one of the most promising energy conversion and storage technologies-the calcium-looping.It includes the basics and barriers of calcium-looping beyond CO_(2) capture and storage(CCS)and technological solutions to address the associated challenges from material to system.Specifically,this paper discusses the flexibility of calcium-looping in the context of CO_(2) capture,combined with the use of H_(2)-rich fuel gas conversion and thermochemical heat storage.To take advantage of calcium-looping based energy integrated utilization of CCS(EIUCCS)in carbon neutral power generation,multiple-scale process innovations will be required,starting from the material level and extending to the system level.展开更多
This paper proposes a hybrid ocean energy sys-tem to form a virtual power plant(VPP)for participating in electricity markets in order to promote the renewable ocean energy utilization and accommodation.In the proposed...This paper proposes a hybrid ocean energy sys-tem to form a virtual power plant(VPP)for participating in electricity markets in order to promote the renewable ocean energy utilization and accommodation.In the proposed system,solar thermal energy is integrated with the closed-cycle ocean thermal energy conversion(OTEC)to boost the temperature differences between the surface and deep seawater for efficiency and flexibility improvements,and the thermodynamic effects of seawater mass flow rates on the output of solar-boosted OTEC(SOTEC)are exploited for deploying SOTEC as a renewable dispatchable unit.An optimal tidal-storage operation model is also developed to make use of subsea pumped storage(SPS)with hydrostatic pressures at ocean depths for mitigating the intermittent tidal range energy in order to make the arbitrage in the electricity market.Furthermore,a two-stage coordinated scheduling strategy is presented to optimally control seawater mass flow rates of SOTEC and hydraulic reversible pump-turbines of SPS for enhancing the daily VPP profit.Comparative studies have been investigated to confirm the superiority of the developed methodology in various renewable ocean energy and electricity market price scenarios.展开更多
基金supported by National Key R&D Program of China(No.2019YFB1504301).
文摘The comprehensive optimization of thermodynamic and economic performances is significant for the engineering application of ocean thermal energy conversion(OTEC).Motivated by this,this paper develops a thermo-economic OTEC model and conducts a sensitivity analysis of the OTEC system concerning its thermodynamic and economic performances.Specifically,the impact of warm-seawater temperature and cold-seawater pumping depth on the net thermal efficiency and the total investment cost are investigated.The results indicate that,an increase in warm-seawater temperature and cold-seawater pumping depth can improve the net thermal efficiency and a higher installed capacity is beneficial to the system economics.Building on these,a design optimization method with considering the on-design and off-design conditions is proposed in this paper,and the dynamic variation of warm-seawater temperature are considered in this method.In multi-objective optimization procedure,with the objective functions being the average net thermal efficiency and unit power cost within the operational cycle,the non-dominated sorting genetic algorithm Ⅱ(NSGA-Ⅱ) is employed to maximize the net thermal efficiency and minimize the unit power investment cost,resulting in the Pareto front.The net thermal efficiencies of OTEC systems using ammonia and R245fa as working fluids are 4.13% and 3.8%,respectively.This represents an improvement of 19.4% and 57.0%,respectively,compared to traditional optimization methods that do not account for off-design conditions.
文摘Ocean thermal energy conversion(OTEC)is a renewable energy source that uses differences in ocean water temperature between warm surface and cold depth to generate electricity.It is an essential link in the carbon neutrality chain and one of the rising sectors of the ocean energy.This paper provides an overview of studies on closed thermodynamic cycles and the numerous difficulties that OTEC technology faces.A description of the thermodynamic cycles incorporating mixed or pure working fluids,as well as the implications of different working fluids on cycle efficiency were also studied.Changes in condensing and evaporating temperatures induced by variations in heat resources affect the efficiency of cycles with pure working fluids.Several strategies,such as intermediate extraction regeneration and heat recovery of ammonia-depleted solution can increase the thermal efficiency with mixed working fluids.In addition,the impact of the ejector on the cycle’s performance is examined.Finally,the efficiency-improving strate-gies are described and summarized.Thermodynamic efficiency can increase using suitable working fluids and taking steps to maximize the rate of ocean thermal energy.To establish which approach is the most effective,different methods have been evaluated and compared under identical operating conditions.
基金part of the OTEC research activity"Preliminary Design of a 5 MW OTEC plant:Study case in the North Bali"research grand DIPA-124.01.1.690505/2023 conducted by the Marine Renewable Energy Conversion Technology research group,Research Center for Hydrodynamics Technology,National Research and Innovation Agency(BRIN)。
文摘Ocean thermal energy conversion(OTEC)is a process of generating electricity by exploiting the temperature difference between warm surface seawater and cold deep seawater.Due to the high static and dynamic pressures that are caused by seawater circulation,the stiffened panel that constitutes a seawater tank may undergo a reduction in ultimate strength.The current paper investigates the design of stiffening systems for OTEC seawater tanks by examining the effects of stiffening parameters such as stiffener sizes and span-over-bay ratio for the applied combined loadings of lateral and transverse pressure by fluid motion and axial compression due to global bending moment.The ultimate strength calculation was conducted by using the non-linear finite element method via the commercial software known as ABAQUS.The stress and deformation distribution due to pressure loads was computed in the first step and then brought to the second step,in which the axial compression was applied.The effects of pressure on the ultimate strength of the stiffener were investigated for representative stiffened panels,and the significance of the stiffener parameters was assessed by using the sensitivity analysis method.As a result,the ultimate strength was reduced by approximately 1.5%for the span-over-bay ratio of 3 and by 7%for the span-over-bay ratio of 6.
基金support by the French National Research Agency through grant ANR-19-CE300012by the European Research Council(ERC)through grant No.772725。
文摘The tremendous amount of wasted heat from solar radiation and industry dissipation has motivated the development of thermoelectric concepts that directly convert heat into electricity.The main challenge in practical applications for thermoelectrics is the high cost from both materials and manufacturing.Recently,breakthrough progresses in ionic thermoelectrics open up new possibilities to charge energy storage devices when submitted to a temperature gradient.The charging voltage is internally from the ionic Seebeck effect of the electrolyte between two electrodes.Hence electrolytes with high thermoelectric figure of merit are classified as ionic thermoelectric materials.Most ionic thermoelectric materials are composed of abundant elements,and they can generate hundreds of times larger thermal voltage than that of electronic materials.This emerging thermoelectric category brings new hope to fabricate low cost and large area heat-to-energy conversion devices,and triggers a renewed interest for ionic thermodiffusion.In this review,we summarize the state of the art in the new field of ionic thermoelectrics,from the driving force of the ionic thermodiffusion to material and application developments.We present a general map of ionic thermoelectric materials,discuss the unique characters of each type of the reported electrolytes,and propose potential optimization and future topics of ionic thermoelectrics.
基金supported by the National Science Fund for Distinguished Young Scholars[51925604]the National Natural Science Foundation of China[52176210,51820105010]+1 种基金the Bureau of International Cooperation of Chinese Academy of Sciences[182211KYSB20170029]the Cooperation Foundation of Dalian National Laboratory for Clean Energy[DNL202017].
文摘With the global ambition of moving towards carbon neutrality,this sets to increase significantly with most of the energy sources from renewables.As a result,cost-effective and resource efficient energy conversion and storage will have a great role to play in energy decarbonization.This review focuses on the most recent developments of one of the most promising energy conversion and storage technologies-the calcium-looping.It includes the basics and barriers of calcium-looping beyond CO_(2) capture and storage(CCS)and technological solutions to address the associated challenges from material to system.Specifically,this paper discusses the flexibility of calcium-looping in the context of CO_(2) capture,combined with the use of H_(2)-rich fuel gas conversion and thermochemical heat storage.To take advantage of calcium-looping based energy integrated utilization of CCS(EIUCCS)in carbon neutral power generation,multiple-scale process innovations will be required,starting from the material level and extending to the system level.
基金the Sino-US International Science and Technology Cooperation Project(No.2019YFE0114700)the National Natural Science Foundation of China(No.51877072)the State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources(No.LAPS20005)。
文摘This paper proposes a hybrid ocean energy sys-tem to form a virtual power plant(VPP)for participating in electricity markets in order to promote the renewable ocean energy utilization and accommodation.In the proposed system,solar thermal energy is integrated with the closed-cycle ocean thermal energy conversion(OTEC)to boost the temperature differences between the surface and deep seawater for efficiency and flexibility improvements,and the thermodynamic effects of seawater mass flow rates on the output of solar-boosted OTEC(SOTEC)are exploited for deploying SOTEC as a renewable dispatchable unit.An optimal tidal-storage operation model is also developed to make use of subsea pumped storage(SPS)with hydrostatic pressures at ocean depths for mitigating the intermittent tidal range energy in order to make the arbitrage in the electricity market.Furthermore,a two-stage coordinated scheduling strategy is presented to optimally control seawater mass flow rates of SOTEC and hydraulic reversible pump-turbines of SPS for enhancing the daily VPP profit.Comparative studies have been investigated to confirm the superiority of the developed methodology in various renewable ocean energy and electricity market price scenarios.
