目的探讨重庆市大气细颗粒物(PM2.5)中的多环芳烃(polycyclic aromatic hydrocarbons,PAHs)暴露对男性精子DNA的损害效应。方法研究对象来源于2013、2014年重庆市大学生男性生殖健康研究队列(male reproductive health in Chongqing col...目的探讨重庆市大气细颗粒物(PM2.5)中的多环芳烃(polycyclic aromatic hydrocarbons,PAHs)暴露对男性精子DNA的损害效应。方法研究对象来源于2013、2014年重庆市大学生男性生殖健康研究队列(male reproductive health in Chongqing college students,MARHCS),检测采样期间大气PM2.5中的低环PAHs(2~4环)和高环PAHs(5~6环)各组分的含量;采用单细胞凝胶电泳实验检测精子DNA损伤;采用混合效应模型探讨PAHs各组分的暴露程度与男性大学生精子DNA损伤水平之间的关联。结果2013年大气细颗粒物中的PAHs组分以低环PAHs为主,其中菲、芴、芘的占比最高,而2014年大气细颗粒物中则以高环PAHs为主,如茚并[1,2,3-cd]芘、苯并[g,h,i]苝、苯并[a]芘等。在2014年,男性大学生的精子DNA损伤指标如彗星尾长、尾矩和Olive尾矩较2013年明显增加(P<0.05)。混合效应模型结果显示:低环PAHs中的荧蒽、苊烯、芘和总低环PAHs与精子DNA损伤指标中的彗星尾长和尾矩呈负相关。高环PAHs中的苯并[k]荧蒽、苯并[b]荧蒽和二苯并[a,h]蒽与精子DNA损伤指标中的彗星尾长呈正相关[β(95%CI):108.987(43.754~203.820)、158.700(65.957~303.272)、185.708(67.350~387.775),校正P均<0.05];与彗星尾矩呈正相关[β(95%CI):449.204(260.066~737.695)、683.108(374.515~1192.387)、683.108(374.515~1192.387),校正P均<0.05]。结论重庆市大气细颗粒物中的高环PAHs组分暴露,可能导致精子DNA损伤效应增加。展开更多
In conventional parabolic trough collectors(PTCs),sunlight is concentrated at the bottom of the absorber tube,resulting in a significant circumferential temperature gradient across the absorber tube,heat loss and ther...In conventional parabolic trough collectors(PTCs),sunlight is concentrated at the bottom of the absorber tube,resulting in a significant circumferential temperature gradient across the absorber tube,heat loss and thermal deformation,which affects the safety and thermal performance of PTCs.In this study,a new receiver with homogenizer and spiral(RHS) is proposed,achieving the optical and thermal synergy to ameliorate the thermal deformation of the absorber tube and enhance thermal efficiency.A plane structure homogenizer is designed to improve uniformity of the concentrated solar flux of absorber tube through second reflection.In combination with the spiral,it improves the optical-thermal efficiency of the PTC by enhancing heat exchange between the fluid and the backlight side of the absorber tube.The performance of the collector is numerically studied by building a three-dimensional coupled light-thermal-structure model.The results show that the thermal deformation of the RHS is reduced by more than 96% and the optical-thermal efficiency is improved by 1.2%-0.63% compared with conventional receivers(CRs) under the same inlet temperature conditions.The proposed receiver is validated to be effective in reducing thermal deformation and improving optical-thermal efficiency.展开更多
In a typical parabolic trough collector(PTC), sunlight is concentrated at the bottom of the absorber tube. This concentrated solar flux leads to uneven heat distribution, resulting in high local temperatures and signi...In a typical parabolic trough collector(PTC), sunlight is concentrated at the bottom of the absorber tube. This concentrated solar flux leads to uneven heat distribution, resulting in high local temperatures and significant thermal stress on the absorber tube.These limitations have restricted the application of PTCs in solar thermochemistry and other fields and have impacted their safe operation. In this study, a new PTC with dual planar mirrors(DPMS) is proposed to homogenize the circumferential solar flux distribution of the absorber tube. A design method and single-objective optimization of the new PTC with a DPMS are proposed,and an uncertainty analysis of the operational and structural parameters is performed. A coupled light-heat-structure numerical model was developed to study the heat transfer performance and structural mechanical properties. The thermodynamic properties of the PTC with DPMS under different boundary conditions were analyzed. The results show that the circumferential temperature difference of the new PTC is within 2.6 K, and the circumferential thermal deformation is within 0.9 mm under typical working conditions(the inlet velocity of the heat transfer fluid is 3 m/s, inlet temperature is 573.15 K, and the direct normal irradiance is 1000 W/m^(2)). Compared with conventional PTCs, the circumferential temperature difference is reduced by 74%–90%, and the maximum thermal deformation along the y-axis is reduced by more than 95% under all working conditions(1–5 m/s, 373.5–675.15 K, 200–1000 W/m^(2)). The new PTC maintains the uniformity of the circumferential solar flux distribution for different operating parameters(sun incident angle of 0°–3°) and installation errors(±3 mm), is suitable for solar energy applications in various fields, and has the potential for large-scale applications.展开更多
For the efficient use of solar and fuels and to improve the supply-demand matching performance in combined heat and power(CHP)systems,this paper proposes a hybrid solar/methanol energy system integrating solar/exhaust...For the efficient use of solar and fuels and to improve the supply-demand matching performance in combined heat and power(CHP)systems,this paper proposes a hybrid solar/methanol energy system integrating solar/exhaust thermochemical and thermal energy storage.The proposed system includes parabolic trough solar collectors(PTSC),a thermochemical reactor,an internal combustion engine(ICE),and hybrid storage of thermal and chemical energy,which uses solar energy and methanol fuel as input and outputs power and heat.With methanol thermochemical decomposition reaction,mid-and-low temperature solar heat and exhaust heat are upgraded to chemical energy for efficient power generation.The thermal energy storage(TES)stores surplus thermal energy,acting as a backup source to produce heat without emitting CO_(2).Due to the energy storage,time-varying solar energy can be used steadily and efficiently;considerable supply-demand mismatches can be avoided,and the operational flexibility is improved.Under the design condition,the overall energy efficiency,exergy efficiency,and net solar-to-electric efficiency achieve 72.09%,37.65%,and 24.63%,respectively.The fuel saving rate(FSR)and the CO_(2) emission reduction(ER_(CO_(2)))achieve 32.97%and 25.33%,respectively.The research findings provide a promising approach for the efficient and flexible use of solar energy and fuels for combined heat and power.展开更多
Multi-energy hybrid energy systems are a promising option to mitigate fluctuations in the renewable energy supply and are crucial in achieving carbon neutrality.Solar-fuel thermochemical hybrid utilization upgrades so...Multi-energy hybrid energy systems are a promising option to mitigate fluctuations in the renewable energy supply and are crucial in achieving carbon neutrality.Solar-fuel thermochemical hybrid utilization upgrades solar energy to fuel chemical energy,thereby achieving the efficient utilization of solar energy,reducing CO_(2)emission,and improving operation stability.For hybrid solar-fuel thermochemical CCHP systems,conventional integration optimization methods and operation modes do not account for the instability of solar energy,thermochemical conversion,and solar fuel storage.To improve the utilization efficiency of solar energy and fuel and achieve favorable economic and environmental performance,a new operation strategy and the optimization of a mid-and-low temperature solar-fuel thermochemical hybrid CCHP system are proposed herein.The system operation modes for various supply-demand scenarios of solar energy input and thermal-power outputs are analyzed,and a new operation strategy that accounts for the effect of solar energy is proposed,which is superior to conventional CCHP system strategies that primarily focus on the balance between system outputs and user loads.To alleviate the challenges of source-load fluctuations and supply-demand mismatches,a multi-objective optimization model is established to optimize the system integration configurations,with objective functions of system energy ratio,cost savings ratio,and CO_(2)emission savings ratio,as well as decision variables of power unit capacity,solar collector area,and syngas storage capacity.The optimization design of the system configuration and the operation strategy improve the performance of the hybrid system.The results show that the system annual energy ratio,cost saving ratio,and CO_(2)emission saving ratio are 52.72%,11.61%,and 36.27%,respectively,whereas the monthly CO_(2)emission reduction rate is 27.3%–47.6%compared with those of reference systems.These promising results will provide useful guidance for the integrated design and operational regulation of hybrid solar-fuel thermochemical systems.展开更多
The absorption heat transformer is widely used to utilize low-temperature waste heat in the field of distributed energy,industrial processing,and long-distance indoor heating,because it can upgrade energy level and de...The absorption heat transformer is widely used to utilize low-temperature waste heat in the field of distributed energy,industrial processing,and long-distance indoor heating,because it can upgrade energy level and deliver heat to heated medium.In this work,an experimental system of a vertical single-stage LiBr/H2O absorption heat transformer was established to study its performance in the case of producing high-temperature water or low-pressure steam generation under different heating water flow rates.The useful output heat,coefficient of performance,exergy coefficient of performance,and gross temperature lift of the single-stage heat transformer have all been tested.The results show that the absorber cannot directly generate low-pressure steam under the condition of counter-flow heat exchange but can obtain more useful output heat.The largest useful output heat is 20.3 kW,which is higher than that in the case of parallel-flow heat exchange.The generation of low-pressure steam has certain requirements on the mode of heat transfer.The largest internal gross temperature lift of 28.1℃corresponds to the smallest coefficient of performance of 0.22 when the heating water flow rate is 2.1 m3/h.The performance of the single-stage absorption heat transformer can be improved to some extent by increasing the heating water flow rate.展开更多
Hydrogen production via a two-step thermochemical cycle based on solar energy has attracted increasing attention.However,the severe irreversible loss causes the low efficiency.To make sense of the irreversibility,an i...Hydrogen production via a two-step thermochemical cycle based on solar energy has attracted increasing attention.However,the severe irreversible loss causes the low efficiency.To make sense of the irreversibility,an in-depth thermodynamic model for the solar driven two-step thermochemical cycles is proposed.Different from previous literatures solely focusing on the energy loss and irreversibility of devices,this work decouples a complex energy conversion process in three sub-processes,i.e.,reaction,heat transfer and re-radiation,acquiring the cause of irreversible loss.The results from the case study indicate that the main irreversibility caused by inert sweeping gas for decreasing the reduction reaction temperature dominates the cycle efficiency.Decreasing reduction reaction temperature without severe energy penalty of inert sweeping gas is important to reducing this irreversible loss.A favorable performance is achieved by decreasing re-oxidation rate,increasing hydrolysis conversion rate and achieving a thermochemical cycle with a lower equilibrium temperature of reduction reaction at atmosphere pressure.The research clarifies the essence of process irrrversibility in solar thermichemical cycles,and the findings point out the potential to develop efficient solar driven two-step thermochemical cycles for hydrogen production.展开更多
Chemical looping hydrogen production is of interest because of its ability to simultaneously produce hydrogen and capture CO_(2) at the same time.Achieving an energy balance is crucial in chemical-looping hydrogen pro...Chemical looping hydrogen production is of interest because of its ability to simultaneously produce hydrogen and capture CO_(2) at the same time.Achieving an energy balance is crucial in chemical-looping hydrogen production systems.Decreasing the external heat duty can effectively reduce carbon capture and energy conversion efficiency.In this study,two auto-thermal chemical looping H_(2) generation systems are proposed.An adiabatic counter current moving bed chemical looping H_(2) generation system using CH_(4) as fuel and Fe_(2)O_(3) and Al_(2)O_(3) (inert carriers)as oxygen carriers(OC)is proposed to analyse the energy balance and exergy balance of the systems.A parametric analysis was conducted to investigate the influence of the reaction ratio and temperature on the product outcomes,leading to the determination of optimal operating conditions.Subsequently,the impact of hydrogen production efficiency and reduction reactor outlet stream ratio and inert component proportion in the oxygen carrier on the system's thermal balance was analysed under these optimal conditions,culminating in the identification of key parameters for the two auto-thermal systems.Energy balance and exergy balance analyses were employed to compare the energy efficiency and irreversible losses of the autothermal and reference systems.The results demonstrated that the autothermal system enhanced the energy efficiency by 2.5%and the CO_(2)capture rate by 11%(percentage points)compared with the reference system.展开更多
文摘目的探讨重庆市大气细颗粒物(PM2.5)中的多环芳烃(polycyclic aromatic hydrocarbons,PAHs)暴露对男性精子DNA的损害效应。方法研究对象来源于2013、2014年重庆市大学生男性生殖健康研究队列(male reproductive health in Chongqing college students,MARHCS),检测采样期间大气PM2.5中的低环PAHs(2~4环)和高环PAHs(5~6环)各组分的含量;采用单细胞凝胶电泳实验检测精子DNA损伤;采用混合效应模型探讨PAHs各组分的暴露程度与男性大学生精子DNA损伤水平之间的关联。结果2013年大气细颗粒物中的PAHs组分以低环PAHs为主,其中菲、芴、芘的占比最高,而2014年大气细颗粒物中则以高环PAHs为主,如茚并[1,2,3-cd]芘、苯并[g,h,i]苝、苯并[a]芘等。在2014年,男性大学生的精子DNA损伤指标如彗星尾长、尾矩和Olive尾矩较2013年明显增加(P<0.05)。混合效应模型结果显示:低环PAHs中的荧蒽、苊烯、芘和总低环PAHs与精子DNA损伤指标中的彗星尾长和尾矩呈负相关。高环PAHs中的苯并[k]荧蒽、苯并[b]荧蒽和二苯并[a,h]蒽与精子DNA损伤指标中的彗星尾长呈正相关[β(95%CI):108.987(43.754~203.820)、158.700(65.957~303.272)、185.708(67.350~387.775),校正P均<0.05];与彗星尾矩呈正相关[β(95%CI):449.204(260.066~737.695)、683.108(374.515~1192.387)、683.108(374.515~1192.387),校正P均<0.05]。结论重庆市大气细颗粒物中的高环PAHs组分暴露,可能导致精子DNA损伤效应增加。
基金supported by the Distinguish Young Scholars of the National Natural Science Foundation of China (No.52225601)the Major Program of the National Natural Science Foundation of China (No.52090061)。
文摘In conventional parabolic trough collectors(PTCs),sunlight is concentrated at the bottom of the absorber tube,resulting in a significant circumferential temperature gradient across the absorber tube,heat loss and thermal deformation,which affects the safety and thermal performance of PTCs.In this study,a new receiver with homogenizer and spiral(RHS) is proposed,achieving the optical and thermal synergy to ameliorate the thermal deformation of the absorber tube and enhance thermal efficiency.A plane structure homogenizer is designed to improve uniformity of the concentrated solar flux of absorber tube through second reflection.In combination with the spiral,it improves the optical-thermal efficiency of the PTC by enhancing heat exchange between the fluid and the backlight side of the absorber tube.The performance of the collector is numerically studied by building a three-dimensional coupled light-thermal-structure model.The results show that the thermal deformation of the RHS is reduced by more than 96% and the optical-thermal efficiency is improved by 1.2%-0.63% compared with conventional receivers(CRs) under the same inlet temperature conditions.The proposed receiver is validated to be effective in reducing thermal deformation and improving optical-thermal efficiency.
基金supported by the Distinguish Young Scholars of the National Natural Science Foundation of China(Grant No. 52225601)the Major Program of the National Natural Science Foundation of China(Grant No.52090061)。
文摘In a typical parabolic trough collector(PTC), sunlight is concentrated at the bottom of the absorber tube. This concentrated solar flux leads to uneven heat distribution, resulting in high local temperatures and significant thermal stress on the absorber tube.These limitations have restricted the application of PTCs in solar thermochemistry and other fields and have impacted their safe operation. In this study, a new PTC with dual planar mirrors(DPMS) is proposed to homogenize the circumferential solar flux distribution of the absorber tube. A design method and single-objective optimization of the new PTC with a DPMS are proposed,and an uncertainty analysis of the operational and structural parameters is performed. A coupled light-heat-structure numerical model was developed to study the heat transfer performance and structural mechanical properties. The thermodynamic properties of the PTC with DPMS under different boundary conditions were analyzed. The results show that the circumferential temperature difference of the new PTC is within 2.6 K, and the circumferential thermal deformation is within 0.9 mm under typical working conditions(the inlet velocity of the heat transfer fluid is 3 m/s, inlet temperature is 573.15 K, and the direct normal irradiance is 1000 W/m^(2)). Compared with conventional PTCs, the circumferential temperature difference is reduced by 74%–90%, and the maximum thermal deformation along the y-axis is reduced by more than 95% under all working conditions(1–5 m/s, 373.5–675.15 K, 200–1000 W/m^(2)). The new PTC maintains the uniformity of the circumferential solar flux distribution for different operating parameters(sun incident angle of 0°–3°) and installation errors(±3 mm), is suitable for solar energy applications in various fields, and has the potential for large-scale applications.
基金financially supported by the Distinguish Young Scholars of the National Natural Science Foundation of China(No.52225601)the National Natural Science Foundation of China(Grant No.52006214)。
文摘For the efficient use of solar and fuels and to improve the supply-demand matching performance in combined heat and power(CHP)systems,this paper proposes a hybrid solar/methanol energy system integrating solar/exhaust thermochemical and thermal energy storage.The proposed system includes parabolic trough solar collectors(PTSC),a thermochemical reactor,an internal combustion engine(ICE),and hybrid storage of thermal and chemical energy,which uses solar energy and methanol fuel as input and outputs power and heat.With methanol thermochemical decomposition reaction,mid-and-low temperature solar heat and exhaust heat are upgraded to chemical energy for efficient power generation.The thermal energy storage(TES)stores surplus thermal energy,acting as a backup source to produce heat without emitting CO_(2).Due to the energy storage,time-varying solar energy can be used steadily and efficiently;considerable supply-demand mismatches can be avoided,and the operational flexibility is improved.Under the design condition,the overall energy efficiency,exergy efficiency,and net solar-to-electric efficiency achieve 72.09%,37.65%,and 24.63%,respectively.The fuel saving rate(FSR)and the CO_(2) emission reduction(ER_(CO_(2)))achieve 32.97%and 25.33%,respectively.The research findings provide a promising approach for the efficient and flexible use of solar energy and fuels for combined heat and power.
基金supported by the National Natural Science Foundation of China (Grant No.52006214)the Basic Science Center Program for Ordered Energy Conversion of the National Natural Science Foundation of China (Grant No.51888103)the Key Laboratory of Efficient Utilization of Low and Medium Grade Energy,Tianjin University。
文摘Multi-energy hybrid energy systems are a promising option to mitigate fluctuations in the renewable energy supply and are crucial in achieving carbon neutrality.Solar-fuel thermochemical hybrid utilization upgrades solar energy to fuel chemical energy,thereby achieving the efficient utilization of solar energy,reducing CO_(2)emission,and improving operation stability.For hybrid solar-fuel thermochemical CCHP systems,conventional integration optimization methods and operation modes do not account for the instability of solar energy,thermochemical conversion,and solar fuel storage.To improve the utilization efficiency of solar energy and fuel and achieve favorable economic and environmental performance,a new operation strategy and the optimization of a mid-and-low temperature solar-fuel thermochemical hybrid CCHP system are proposed herein.The system operation modes for various supply-demand scenarios of solar energy input and thermal-power outputs are analyzed,and a new operation strategy that accounts for the effect of solar energy is proposed,which is superior to conventional CCHP system strategies that primarily focus on the balance between system outputs and user loads.To alleviate the challenges of source-load fluctuations and supply-demand mismatches,a multi-objective optimization model is established to optimize the system integration configurations,with objective functions of system energy ratio,cost savings ratio,and CO_(2)emission savings ratio,as well as decision variables of power unit capacity,solar collector area,and syngas storage capacity.The optimization design of the system configuration and the operation strategy improve the performance of the hybrid system.The results show that the system annual energy ratio,cost saving ratio,and CO_(2)emission saving ratio are 52.72%,11.61%,and 36.27%,respectively,whereas the monthly CO_(2)emission reduction rate is 27.3%–47.6%compared with those of reference systems.These promising results will provide useful guidance for the integrated design and operational regulation of hybrid solar-fuel thermochemical systems.
基金The authors gratefully acknowledge the support of the National KeyR&D Program of China(No.2018YFBO905103)the National Natural Science Foundation of China(No.51806213)+1 种基金the Beijing Key Laboratory of Distributed Combined Cooling Heating and Power SystemGuangdong Provincial Key Laboratory of Distributed Energy Systems(No.2017DESO5).
文摘The absorption heat transformer is widely used to utilize low-temperature waste heat in the field of distributed energy,industrial processing,and long-distance indoor heating,because it can upgrade energy level and deliver heat to heated medium.In this work,an experimental system of a vertical single-stage LiBr/H2O absorption heat transformer was established to study its performance in the case of producing high-temperature water or low-pressure steam generation under different heating water flow rates.The useful output heat,coefficient of performance,exergy coefficient of performance,and gross temperature lift of the single-stage heat transformer have all been tested.The results show that the absorber cannot directly generate low-pressure steam under the condition of counter-flow heat exchange but can obtain more useful output heat.The largest useful output heat is 20.3 kW,which is higher than that in the case of parallel-flow heat exchange.The generation of low-pressure steam has certain requirements on the mode of heat transfer.The largest internal gross temperature lift of 28.1℃corresponds to the smallest coefficient of performance of 0.22 when the heating water flow rate is 2.1 m3/h.The performance of the single-stage absorption heat transformer can be improved to some extent by increasing the heating water flow rate.
基金the financial support provided by the National Natural Science Foundation of China(No.52090061)the Basic Science Center Program for Ordered Energy Conversion of the National Natural Science Foundation of China(No.51888103)。
文摘Hydrogen production via a two-step thermochemical cycle based on solar energy has attracted increasing attention.However,the severe irreversible loss causes the low efficiency.To make sense of the irreversibility,an in-depth thermodynamic model for the solar driven two-step thermochemical cycles is proposed.Different from previous literatures solely focusing on the energy loss and irreversibility of devices,this work decouples a complex energy conversion process in three sub-processes,i.e.,reaction,heat transfer and re-radiation,acquiring the cause of irreversible loss.The results from the case study indicate that the main irreversibility caused by inert sweeping gas for decreasing the reduction reaction temperature dominates the cycle efficiency.Decreasing reduction reaction temperature without severe energy penalty of inert sweeping gas is important to reducing this irreversible loss.A favorable performance is achieved by decreasing re-oxidation rate,increasing hydrolysis conversion rate and achieving a thermochemical cycle with a lower equilibrium temperature of reduction reaction at atmosphere pressure.The research clarifies the essence of process irrrversibility in solar thermichemical cycles,and the findings point out the potential to develop efficient solar driven two-step thermochemical cycles for hydrogen production.
基金supported by the Distinguish Young Scholars of the National Natural Science Foundation of China(Grant No.52225601)the Major Program of the National Natural Science Foundation of China(Grant No.52090061)。
文摘Chemical looping hydrogen production is of interest because of its ability to simultaneously produce hydrogen and capture CO_(2) at the same time.Achieving an energy balance is crucial in chemical-looping hydrogen production systems.Decreasing the external heat duty can effectively reduce carbon capture and energy conversion efficiency.In this study,two auto-thermal chemical looping H_(2) generation systems are proposed.An adiabatic counter current moving bed chemical looping H_(2) generation system using CH_(4) as fuel and Fe_(2)O_(3) and Al_(2)O_(3) (inert carriers)as oxygen carriers(OC)is proposed to analyse the energy balance and exergy balance of the systems.A parametric analysis was conducted to investigate the influence of the reaction ratio and temperature on the product outcomes,leading to the determination of optimal operating conditions.Subsequently,the impact of hydrogen production efficiency and reduction reactor outlet stream ratio and inert component proportion in the oxygen carrier on the system's thermal balance was analysed under these optimal conditions,culminating in the identification of key parameters for the two auto-thermal systems.Energy balance and exergy balance analyses were employed to compare the energy efficiency and irreversible losses of the autothermal and reference systems.The results demonstrated that the autothermal system enhanced the energy efficiency by 2.5%and the CO_(2)capture rate by 11%(percentage points)compared with the reference system.
