In this study,a novel irreversible cyclic model of a capacitive mixing blue heat engine mainly consisting of super capacitors,charging and discharging circuits,a heat source,as well as two water sources with given sal...In this study,a novel irreversible cyclic model of a capacitive mixing blue heat engine mainly consisting of super capacitors,charging and discharging circuits,a heat source,as well as two water sources with given salt concentrations is established for harvesting salinity gradient energy and waste heat.Additionally,the effects of the charging voltage and ratio of the minimum to maximum surface electric charge density on the thermodynamic efficiency and power output of the cycle are discussed.The maximum power output of the cycle is calculated.The optimized ranges of efficiency and power output as well as the temperatures of two isothermal processes are determined.It is established that during the isoelectric quantity process,there is not only an increase in thermal voltage owing to the temperature difference,but also an increase in concentration voltage owing to the salinity gradient.Consequently,the blue heat engine can obtain higher energy conversion efficiency than a conventional heat engine.When the temperature ratio of the heat source to the heat sink is 1.233,the maximum efficiency can reach approximately36%.The results obtained can promote the application of capacitive mixing technology in real life,reducing the consumption of fossil fuels.展开更多
Power spectrum and cross-wavelet transform analysis was adopted to study the time-frequency characteristics and multiscale correlations between runoff,tidal range and salinity in the Changjiang Estuary based on the ru...Power spectrum and cross-wavelet transform analysis was adopted to study the time-frequency characteristics and multiscale correlations between runoff,tidal range and salinity in the Changjiang Estuary based on the runoff data collected at the Datong Station,the tidal range measured at the Baozhen Station,and the salinity at the Baogang Station from 2008 to 2009.The variations of the salinity showed significant periodicity at scales of 2-3,7-8,14-15 and 26-30 d.The correlation between the salinity and the runoff and the tidal range were found to be significantly related to shock at scales of 5-7,14-15,26-30 d and 0.5 a.The correlation between the runoff and the salinity was mainly in the same phase,while the correlation between the tidal range and the salinity was in the antiphase.Different frequency bands were related to different degrees,and their relevance increased as the resonance frequency decreased.In addition,changes of the seasonal runoff were obvious.Specifically,a point of discontinuity was reached in early June with a cycle of 7-8 d,which coincided with the periodicity of plum rains in the Changjiang-Huaihe region.High-frequency changes （8-16 d period） of the salinity corresponded to the time domain in January-April 2008,February-April 2009 and October-December 2009 and exhibited an approximately 0.5 a （184 d） long frequency oscillation.Short-period changes were found to be stronger than long-period changes.Cross-wavelet transforms for the salinity,the runoff and the tidal range revealed local features in the time domain,while the significant levels of different periodic oscillations were observed in the frequency domain.The correlation characteristics of the salinity and the runoff were significant in the 80-90 d frequency domain,indicating that the major impact of the runoff on the salinity was reflected in seasonal changes.The tidal range on the small scale of 14-15 and 30-32 d was more obvious than the runoff.展开更多
The development of novel materials with ion-selective nanochannels has introduced a new technology for harvesting salinity gradient(blue)energy,namely nanopore power generators(NPGs).In this study,we perform a compreh...The development of novel materials with ion-selective nanochannels has introduced a new technology for harvesting salinity gradient(blue)energy,namely nanopore power generators(NPGs).In this study,we perform a comprehensive analysis of the practical performance of NPG in both coupon-size and module-scale operations.We show that although NPG membrane coupons can theoretically generate ultrahigh power density under ideal conditions,the resulting power density in practical operations at a coupon scale can hardly reach 10 W·m^(-2) due to concentration polarization effects.For module-scale NPG operation,we estimate both the power density and specific extractable energy(i.e.,extractable energy normalized by the total volume of the working solutions),and elucidate the impact of operating conditions on these two metrics based on the interplay between concentration polarization and extent of mixing of the high-and low-concentration solutions.Further,we develop a modeling framework to assess the viability of an NPG system.Our results demonstrate that,for NPG systems working with seawater and river water,the gross specific extractable energy by the NPG system is very low(~0.1 kW?h?m?3)and is further compromised by the parasitic energy consumptions in the system(notably,pumping of the seawater and river water solutions and their pretreatment).Overall,NPG systems produce very low net specific extractable energy(<0.025 kW?h?m?3)and net power density(<0.1 W?m?2).Our study highlights the significant practical limitations in NPG operations,casting doubt on the viability of NPG as a technology for blue energy harvesting.展开更多
盐差能广泛存在于江河入海口处,蕴藏量巨大.通过反向电渗析法可将盐差能直接转化为电能,因其利用过程简单无污染,近年来受到广泛关注.二维材料的出现为盐差能发电带来新的契机,规则的纳米孔道与丰富的官能团使得其对外输出功率超过了可...盐差能广泛存在于江河入海口处,蕴藏量巨大.通过反向电渗析法可将盐差能直接转化为电能,因其利用过程简单无污染,近年来受到广泛关注.二维材料的出现为盐差能发电带来新的契机,规则的纳米孔道与丰富的官能团使得其对外输出功率超过了可商业化功率5 W m^(-2);但目前大多研究中盐差能性能测试膜面积仅为3×10^(4)μm^(2),且当测试面积增加时,功率会大幅下降.本文通过简单的真空抽滤法构筑氧化石墨烯与二硫化钼(GOMoS_(2))的2D-2D多层级结构,该结构使得离子选择性膜在较大的面积下仍能保持有序的层状结构,实现高通量高选择性的离子输运,最终输出较高的发电功率.同时,2D-2D结构有效地控制了二维材料膜入水溶胀的问题,提供丰富的表面孔洞与多级层间距,有利于离子的快速选择性运输.大面积膜(面积为3.14 mm^(2),为传统研究的100倍)渗透能测试结果表明,GO-MoS_(2)复合膜的渗透电压与渗透电流都表现优异,在100倍浓度梯度下可获得0.57 W m^(-2)的功率,相较于纯GO薄膜提高了92.7%.2D-2D多层级结构为构筑大面积且制备简单的高效离子选择性薄膜提供了新思路,可为二维材料在盐差能发电乃至海水淡化、气体分离、生物医学等领域的工业化应用提供参考.展开更多
We studied the effect of salinity on nail-hold- ing power in wood construction. In saline solution, the holding power of nails was less than in purified water. With the increase of salt concentration, the surface and ...We studied the effect of salinity on nail-hold- ing power in wood construction. In saline solution, the holding power of nails was less than in purified water. With the increase of salt concentration, the surface and side nail- holding power of the wood specimens both declined, but the differences between salinity treatments were not sig- nificant. However, compared to the surface and side nail- holding power, the power on the edge was generally less and the difference was not obvious in different salt con- centrations. In the same salt concentration, with the extension of the processing cycle, the performance of holding power of nails showed a downward trend, expect the temporary rise in the middle.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.51876181)。
文摘In this study,a novel irreversible cyclic model of a capacitive mixing blue heat engine mainly consisting of super capacitors,charging and discharging circuits,a heat source,as well as two water sources with given salt concentrations is established for harvesting salinity gradient energy and waste heat.Additionally,the effects of the charging voltage and ratio of the minimum to maximum surface electric charge density on the thermodynamic efficiency and power output of the cycle are discussed.The maximum power output of the cycle is calculated.The optimized ranges of efficiency and power output as well as the temperatures of two isothermal processes are determined.It is established that during the isoelectric quantity process,there is not only an increase in thermal voltage owing to the temperature difference,but also an increase in concentration voltage owing to the salinity gradient.Consequently,the blue heat engine can obtain higher energy conversion efficiency than a conventional heat engine.When the temperature ratio of the heat source to the heat sink is 1.233,the maximum efficiency can reach approximately36%.The results obtained can promote the application of capacitive mixing technology in real life,reducing the consumption of fossil fuels.
基金The Public Science and Technology Research Funds Projects of Ocean under contract Nos 200905001,200905010 and 201005019the Research Programs of the Science and Technology Commission of Shanghai of China under contract No.09DZ1201200Young Scientist Foundation of the State Oceanic Administration of China under contract No.2008234
文摘Power spectrum and cross-wavelet transform analysis was adopted to study the time-frequency characteristics and multiscale correlations between runoff,tidal range and salinity in the Changjiang Estuary based on the runoff data collected at the Datong Station,the tidal range measured at the Baozhen Station,and the salinity at the Baogang Station from 2008 to 2009.The variations of the salinity showed significant periodicity at scales of 2-3,7-8,14-15 and 26-30 d.The correlation between the salinity and the runoff and the tidal range were found to be significantly related to shock at scales of 5-7,14-15,26-30 d and 0.5 a.The correlation between the runoff and the salinity was mainly in the same phase,while the correlation between the tidal range and the salinity was in the antiphase.Different frequency bands were related to different degrees,and their relevance increased as the resonance frequency decreased.In addition,changes of the seasonal runoff were obvious.Specifically,a point of discontinuity was reached in early June with a cycle of 7-8 d,which coincided with the periodicity of plum rains in the Changjiang-Huaihe region.High-frequency changes （8-16 d period） of the salinity corresponded to the time domain in January-April 2008,February-April 2009 and October-December 2009 and exhibited an approximately 0.5 a （184 d） long frequency oscillation.Short-period changes were found to be stronger than long-period changes.Cross-wavelet transforms for the salinity,the runoff and the tidal range revealed local features in the time domain,while the significant levels of different periodic oscillations were observed in the frequency domain.The correlation characteristics of the salinity and the runoff were significant in the 80-90 d frequency domain,indicating that the major impact of the runoff on the salinity was reflected in seasonal changes.The tidal range on the small scale of 14-15 and 30-32 d was more obvious than the runoff.
基金financial support from the Center for Enhanced Nanofluidic Transport (CENT),an Energy Frontier Research Center funded by the US Department of Energy,Office of Science,Basic Energy Sciences through Award No.DESC0019112
文摘The development of novel materials with ion-selective nanochannels has introduced a new technology for harvesting salinity gradient(blue)energy,namely nanopore power generators(NPGs).In this study,we perform a comprehensive analysis of the practical performance of NPG in both coupon-size and module-scale operations.We show that although NPG membrane coupons can theoretically generate ultrahigh power density under ideal conditions,the resulting power density in practical operations at a coupon scale can hardly reach 10 W·m^(-2) due to concentration polarization effects.For module-scale NPG operation,we estimate both the power density and specific extractable energy(i.e.,extractable energy normalized by the total volume of the working solutions),and elucidate the impact of operating conditions on these two metrics based on the interplay between concentration polarization and extent of mixing of the high-and low-concentration solutions.Further,we develop a modeling framework to assess the viability of an NPG system.Our results demonstrate that,for NPG systems working with seawater and river water,the gross specific extractable energy by the NPG system is very low(~0.1 kW?h?m?3)and is further compromised by the parasitic energy consumptions in the system(notably,pumping of the seawater and river water solutions and their pretreatment).Overall,NPG systems produce very low net specific extractable energy(<0.025 kW?h?m?3)and net power density(<0.1 W?m?2).Our study highlights the significant practical limitations in NPG operations,casting doubt on the viability of NPG as a technology for blue energy harvesting.
文摘盐差能广泛存在于江河入海口处,蕴藏量巨大.通过反向电渗析法可将盐差能直接转化为电能,因其利用过程简单无污染,近年来受到广泛关注.二维材料的出现为盐差能发电带来新的契机,规则的纳米孔道与丰富的官能团使得其对外输出功率超过了可商业化功率5 W m^(-2);但目前大多研究中盐差能性能测试膜面积仅为3×10^(4)μm^(2),且当测试面积增加时,功率会大幅下降.本文通过简单的真空抽滤法构筑氧化石墨烯与二硫化钼(GOMoS_(2))的2D-2D多层级结构,该结构使得离子选择性膜在较大的面积下仍能保持有序的层状结构,实现高通量高选择性的离子输运,最终输出较高的发电功率.同时,2D-2D结构有效地控制了二维材料膜入水溶胀的问题,提供丰富的表面孔洞与多级层间距,有利于离子的快速选择性运输.大面积膜(面积为3.14 mm^(2),为传统研究的100倍)渗透能测试结果表明,GO-MoS_(2)复合膜的渗透电压与渗透电流都表现优异,在100倍浓度梯度下可获得0.57 W m^(-2)的功率,相较于纯GO薄膜提高了92.7%.2D-2D多层级结构为构筑大面积且制备简单的高效离子选择性薄膜提供了新思路,可为二维材料在盐差能发电乃至海水淡化、气体分离、生物医学等领域的工业化应用提供参考.
基金financially supported by the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD)Jiangsu Overseas Research&Training Program for University Prominent Young&Middle-aged Teachers and Presidents
文摘We studied the effect of salinity on nail-hold- ing power in wood construction. In saline solution, the holding power of nails was less than in purified water. With the increase of salt concentration, the surface and side nail- holding power of the wood specimens both declined, but the differences between salinity treatments were not sig- nificant. However, compared to the surface and side nail- holding power, the power on the edge was generally less and the difference was not obvious in different salt con- centrations. In the same salt concentration, with the extension of the processing cycle, the performance of holding power of nails showed a downward trend, expect the temporary rise in the middle.
