Liquefied natural gas(LNG)is regarded as one of the cleanest fossil fuel and has experienced significant developments in recent years.The liquefaction process of natural gas is energy-intensive,while the regasificatio...Liquefied natural gas(LNG)is regarded as one of the cleanest fossil fuel and has experienced significant developments in recent years.The liquefaction process of natural gas is energy-intensive,while the regasification of LNG gives out a huge amount of waste energy since plenty of high grade cold energy(-160℃)from LNG is released to sea water directly in most cases,and also sometimes LNG is burned for regasification.On the other hand,liquid air energy storage(LAES)is an emerging energy storage technology for applications such as peak load shifting of power grids,which generates 30%-40%of compression heat(-200℃).Such heat could lead to energy waste if not recovered and used.The recovery of the compression heat is technically feasible but requires additional capital investment,which may not always be economically attractive.Therefore,we propose a power plant for recovering the waste cryogenic energy from LNG regasification and compression heat from the LAES.The challenge for such a power plant is the wide working temperature range between the low-temperature exergy source(-160℃)and heat source(-200℃).Nitrogen and argon are proposed as the working fluids to address the challenge.Thermodynamic analyses are carried out and the results show that the power plant could achieve a thermal efficiency of 27%and 19%and an exergy efficiency of 40%and 28%for nitrogen and argon,respectively.Here,with the nitrogen as working fluid undergoes a complete Brayton Cycle,while the argon based power plant goes through a combined Brayton and Rankine Cycle.Besides,the economic analysis shows that the payback period of this proposed system is only 2.2 years,utilizing the excess heat from a 5 MW/40 MWh LAES system.The findings suggest that the waste energy based power plant could be co-located with the LNG terminal and LAES plant,providing additional power output and reducing energy waste.展开更多
To address global challenge of climate changes,renewable energy has been fully developed in recent years.However,renewable energy is usually intermittent which makes it challenging for application.Liquid air energy st...To address global challenge of climate changes,renewable energy has been fully developed in recent years.However,renewable energy is usually intermittent which makes it challenging for application.Liquid air energy storage can effectively store intermittent energy with promising prospects.Liquid air is a mixture composed of N_(2),O_(2) and Ar with different evaporation temperatures.It is assumed to form temperature and concentration stratification during storage and thus causes safety challenge.To address this issue,molecular dynamics(MD)simulation method is used to study the temperature and concentration distribution characteristics in liquid air.The results show that the system temperature remains constant at 94 K with no temperature stratification during storage.However,the concentration of liquid air changes along vertical direction(z axis):the oxygen concentration remains stable around 21%as z is 0-60Å,rises to 22.1%as z is from 60 to 70Åand drops to 0%as z is above 80Å.The thin and short stratification phenomenon occurs at the gas-liquid interface region.In addition,a higher heat flux leads to a higher evaporation rate and a larger oxygen concentration.As the heat flux increases from 0.0 to 2.4 W/m^(2),evaporation rate rises from 0.13 to 0.2%and the oxygen concentration at the liquid-gas interface reaches 22.3%.Thus,concentration stratification exists during liquid air storage and should be treated carefully.This paper provides an insight into the temperature and concentration distribution of liquid air during storage and is significant for safety improvement and development of liquid air energy storage.展开更多
基金partial support of UK EPSRC under grants EP/V012053/1,EP/S032622/1,EP/P004709/1,EP/P003605/1 and EP/N032888/1the British Council under 2020-RLWK12-10478 and 2019-RLWK11-10724。
文摘Liquefied natural gas(LNG)is regarded as one of the cleanest fossil fuel and has experienced significant developments in recent years.The liquefaction process of natural gas is energy-intensive,while the regasification of LNG gives out a huge amount of waste energy since plenty of high grade cold energy(-160℃)from LNG is released to sea water directly in most cases,and also sometimes LNG is burned for regasification.On the other hand,liquid air energy storage(LAES)is an emerging energy storage technology for applications such as peak load shifting of power grids,which generates 30%-40%of compression heat(-200℃).Such heat could lead to energy waste if not recovered and used.The recovery of the compression heat is technically feasible but requires additional capital investment,which may not always be economically attractive.Therefore,we propose a power plant for recovering the waste cryogenic energy from LNG regasification and compression heat from the LAES.The challenge for such a power plant is the wide working temperature range between the low-temperature exergy source(-160℃)and heat source(-200℃).Nitrogen and argon are proposed as the working fluids to address the challenge.Thermodynamic analyses are carried out and the results show that the power plant could achieve a thermal efficiency of 27%and 19%and an exergy efficiency of 40%and 28%for nitrogen and argon,respectively.Here,with the nitrogen as working fluid undergoes a complete Brayton Cycle,while the argon based power plant goes through a combined Brayton and Rankine Cycle.Besides,the economic analysis shows that the payback period of this proposed system is only 2.2 years,utilizing the excess heat from a 5 MW/40 MWh LAES system.The findings suggest that the waste energy based power plant could be co-located with the LNG terminal and LAES plant,providing additional power output and reducing energy waste.
基金The authors are grateful for the support from Hundred Talents Program of Hebei Province(Grant No.E2020050008).
文摘To address global challenge of climate changes,renewable energy has been fully developed in recent years.However,renewable energy is usually intermittent which makes it challenging for application.Liquid air energy storage can effectively store intermittent energy with promising prospects.Liquid air is a mixture composed of N_(2),O_(2) and Ar with different evaporation temperatures.It is assumed to form temperature and concentration stratification during storage and thus causes safety challenge.To address this issue,molecular dynamics(MD)simulation method is used to study the temperature and concentration distribution characteristics in liquid air.The results show that the system temperature remains constant at 94 K with no temperature stratification during storage.However,the concentration of liquid air changes along vertical direction(z axis):the oxygen concentration remains stable around 21%as z is 0-60Å,rises to 22.1%as z is from 60 to 70Åand drops to 0%as z is above 80Å.The thin and short stratification phenomenon occurs at the gas-liquid interface region.In addition,a higher heat flux leads to a higher evaporation rate and a larger oxygen concentration.As the heat flux increases from 0.0 to 2.4 W/m^(2),evaporation rate rises from 0.13 to 0.2%and the oxygen concentration at the liquid-gas interface reaches 22.3%.Thus,concentration stratification exists during liquid air storage and should be treated carefully.This paper provides an insight into the temperature and concentration distribution of liquid air during storage and is significant for safety improvement and development of liquid air energy storage.
