A tunable selective emitter with hollow zigzag SiO_(2) metamaterials, which are deposited on Si_(3) N_(4) and Ag film, is proposed and numerically investigated for achieving excellent radiative cooling effects. The av...A tunable selective emitter with hollow zigzag SiO_(2) metamaterials, which are deposited on Si_(3) N_(4) and Ag film, is proposed and numerically investigated for achieving excellent radiative cooling effects. The average emissivity reaches a high value of 98.7% in the atmospheric window and possesses a high reflectivity of 92.0% in the solar spectrum. To reveal the enhanced absorptivity, the confined electric field distribution is investigated, and it can be well explained by moth eye effects. Moreover, tunable emissivity can also be initiated with different incident angles and it stays above 83% when the incident angle is less than 80°, embodying the excellent cooling performance in the atmospheric transparency window.Its net cooling power achieves 100.6 W·m^(-2), with a temperature drop of 13°, and the cooling behavior can persist in the presence of non-radiative heat exchange conditions. Therefore, high and tunable selective emitters based on our designed structure could provide a new route to realizing high-performance radiative cooling. This work is also of great significance for saving energy and environmental protection.展开更多
Personal daytime radiative cooling(PDRC)materials have high sunlight reflection and high selective emis-sivity to outer space in the main atmospheric window,demonstrating huge potential in energy-saving for sustainabl...Personal daytime radiative cooling(PDRC)materials have high sunlight reflection and high selective emis-sivity to outer space in the main atmospheric window,demonstrating huge potential in energy-saving for sustainable development.Recently,polymer-based membranes for radiative cooling have been widely re-ported,due to their easy processing,low cost,and unique optical performance.However,the desired high sunlight reflectance of PDRC materials is easily dampened by environmental aging,high temperature,and ultraviolet(UV)irradiation,resulting in reduced cooling performance for most polymers,adverse to large-scale practical applications.In this work,we demonstrate a novel polyimide nanofiber(PINF)membrane with a fluorine-containing structure via typical electrospinning technology.The resultant PINF membrane exhibits high sunlight reflectance,UV resistance,and excellent thermal stability,rendering anti-aging day-time radiative cooling.The sunlight reflectance of PINF membranes could maintain constant in the aging test for continuous 720 h under outdoor solar irradiation,exhibiting durable and long-term personal day-time radiative cooling performance.展开更多
Radiative cooling without energy consumption and environmental pollution holds great promise as the next-generation cooling technology.To date,daytime radiative cooling performance is still slightly low,especially in ...Radiative cooling without energy consumption and environmental pollution holds great promise as the next-generation cooling technology.To date,daytime radiative cooling performance is still slightly low,especially in humid areas.In this work,we demonstrated that nanoporous polyethylene(Nano PE)film can improve solar reflectivity from 96%to 99%,thus boosting radiative cooling performance.Moreover,the experimental results in humid areas indicate that Nano PE films can improve radiative cooling performance by∼76%in a clear day and 120%in a day with few clouds.Additionally,compared with ordinary PE films,thin Nano PE films have significantly higher weather fastness and mechanical strength.More importantly,nano PE films can scatter part of visible light,thus suppressing the generation of light pollution in practical applications.Lastly,the modeling results reveal that with Nano PE films,more than 95%of China’s areas can achieve daytime cooling performance.Our work can boost the development of radiative cooling technology with a very low cost.展开更多
Passive daytime radiative cooling(PDRC) is useful for thermal management because it allows an object to emit terrestrial heat into space without the use of additional energy.To produce sub-ambient temperatures under d...Passive daytime radiative cooling(PDRC) is useful for thermal management because it allows an object to emit terrestrial heat into space without the use of additional energy.To produce sub-ambient temperatures under direct sunlight,PDRC materials are designed to reduce their absorption of solar energy and to enhance their long-wavelength infrared(LWIR) emissivity.In recent years,many photonic structures and polymer composites have been studied to improve the cooling system of buildings.However,in cold weather(i.e. during winter in cold climates),buildings need to be kept warm rather than cooled due to heat loss.To overcome this limitation,temperature-responsive radiative cooling is a promising alternative.In the present study,adaptive radiative cooling(ARC) film fabricated from a polydimethylsiloxane/hollow SiO_(2) microsphere/thermochromic pigment composite was investigated.We found that the ARC film absorbed solar radiation under cold conditions while exhibiting radiative cooling at ambient temperatures above 40℃.Thus,in outdoor experiments,the ARC film achieved sub-ambient temperatures and had a theoretical cooling power of 63.2 W/m~2 in hot weather.We also demonstrated that radiative cooling with an energy harvesting system could be used to improve the energy management of buildings,with the thermoelectric module continuously generating output power using the ARC film.Therefore,we believe that our proposed ARC film can be employed for efficient thermal management of buildings and all-season energy harvesting in the near future.展开更多
The demand for highly porous yet transparent aerogels with mechanical flexibility and solar-thermal dual-regulation for energy-saving windows is significant but challenging.Herein,a delaminated aerogel film(DAF)is fab...The demand for highly porous yet transparent aerogels with mechanical flexibility and solar-thermal dual-regulation for energy-saving windows is significant but challenging.Herein,a delaminated aerogel film(DAF)is fabricated through filtration-induced delaminated gelation and ambient drying.The delaminated gelation process involves the assembly of fluorinated cellulose nanofiber(FCNF)at the solid-liquid interface between the filter and the filtrate during filtration,resulting in the formation of lamellar FCNF hydrogels with strong intra-plane and weak interlayer hydrogen bonding.By exchanging the solvents from water to hexane,the hydrogen bonding in the FCNF hydrogel is further enhanced,enabling the formation of the DAF with intra-layer mesopores upon ambient drying.The resulting aerogel film is lightweight and ultra-flexible,which pos-sesses desirable properties of high visible-light transmittance(91.0%),low thermal conductivity(33 mW m^(-1) K^(-1)),and high atmospheric-window emissivity(90.1%).Furthermore,the DAF exhibits reduced surface energy and exceptional hydrophobicity due to the presence of fluorine-containing groups,enhancing its durability and UV resistance.Consequently,the DAF has demonstrated its potential as solar-thermal regulatory cooling window materials capable of simultaneously providing indoor lighting,thermal insulation,and daytime radiative cooling under direct sunlight.Significantly,the enclosed space protected by the DAF exhibits a temperature reduction of 2.6℃ compared to that shielded by conventional architectural glass.展开更多
Global warming has become one of the major environmental problems facing mankind in the 21st century,The existing refrigeration technology of buildings,like air conditioning,consumes a lot of energy.Passive daytime ra...Global warming has become one of the major environmental problems facing mankind in the 21st century,The existing refrigeration technology of buildings,like air conditioning,consumes a lot of energy.Passive daytime radiative cooling technology works without consuming energy.nor emitting carbon dioxide and other greenhouse gases.This review summarizes the development of daytime passive radiative cooling technologyfrom the basic principles,structure and materials of radiative coolers;analyses and evaluates the various existing radiative coolers.The core of radiative cooling lies in the combination of multi-scale micro/nano structures.The cooler reflects sunlight thus preventing the building from being heated up;while allows the building toradiate its own heat out thus being cooled down;meanwhile maintains the temperature difference by the heat insulation effect ofthe porous structure in theflm.The common challenges and potential solutions for the commercialization of radiative cooling technologies are analyzed,which may promote the applications of the technology in the near future.展开更多
Passive daytime radiative cooling(PDRC)is an innovative and sustainable cooling technology that holds immense potential for addressing the energy crisis.Despite the numerous reports on radiative coolers,the design of ...Passive daytime radiative cooling(PDRC)is an innovative and sustainable cooling technology that holds immense potential for addressing the energy crisis.Despite the numerous reports on radiative coolers,the design of a straightforward,efficient,and readily producible system remains a challenge.Herein,we present the development of a hierarchical aligned porous poly(vinylidene fluoride)(HAP-PVDF)film through a freeze-thaw-promoted nonsolvent-induced phase separation strategy.This film features oriented microporous arrays in conjunction with random nanopores,enabling efficient radiative cooling performance under direct sunlight conditions.The incorporation of both micro-and nano-pores in the HAP-PVDF film results in a remarkable solar reflectance of 97%and a sufficiently high infrared thermal emissivity of 96%,facilitating sub-environmental cooling at 18.3℃ on sunny days and 13.1℃ on cloudy days.Additionally,the HAP-PVDF film also exhibits exceptional flexibility and hydrophobicity.Theoretical calculations further confirm a radiative cooling power of 94.8 W·m^(-2)under a solar intensity of 1000W·m^(-2),demonstrating a performance comparable to the majority of reported radiative coolers.展开更多
基金supported by the Natural Science Foundation of Henan Educational Committee (Grant No. 21A140026)。
文摘A tunable selective emitter with hollow zigzag SiO_(2) metamaterials, which are deposited on Si_(3) N_(4) and Ag film, is proposed and numerically investigated for achieving excellent radiative cooling effects. The average emissivity reaches a high value of 98.7% in the atmospheric window and possesses a high reflectivity of 92.0% in the solar spectrum. To reveal the enhanced absorptivity, the confined electric field distribution is investigated, and it can be well explained by moth eye effects. Moreover, tunable emissivity can also be initiated with different incident angles and it stays above 83% when the incident angle is less than 80°, embodying the excellent cooling performance in the atmospheric transparency window.Its net cooling power achieves 100.6 W·m^(-2), with a temperature drop of 13°, and the cooling behavior can persist in the presence of non-radiative heat exchange conditions. Therefore, high and tunable selective emitters based on our designed structure could provide a new route to realizing high-performance radiative cooling. This work is also of great significance for saving energy and environmental protection.
基金National Natural Science Foundation of China(No.52073053)Young Elite Scientists Sponsorship Program by CAST(No.2021QNRC001)+2 种基金Shanghai Rising-Star Program(No.21QA1400300)Innovation Program of Shanghai Municipal Education Commission(No.2021–01–07–00–03-E00108)Fundamental Research Funds for the Central Universities(No.JUSRP123014).
文摘Personal daytime radiative cooling(PDRC)materials have high sunlight reflection and high selective emis-sivity to outer space in the main atmospheric window,demonstrating huge potential in energy-saving for sustainable development.Recently,polymer-based membranes for radiative cooling have been widely re-ported,due to their easy processing,low cost,and unique optical performance.However,the desired high sunlight reflectance of PDRC materials is easily dampened by environmental aging,high temperature,and ultraviolet(UV)irradiation,resulting in reduced cooling performance for most polymers,adverse to large-scale practical applications.In this work,we demonstrate a novel polyimide nanofiber(PINF)membrane with a fluorine-containing structure via typical electrospinning technology.The resultant PINF membrane exhibits high sunlight reflectance,UV resistance,and excellent thermal stability,rendering anti-aging day-time radiative cooling.The sunlight reflectance of PINF membranes could maintain constant in the aging test for continuous 720 h under outdoor solar irradiation,exhibiting durable and long-term personal day-time radiative cooling performance.
基金This work was supported by National Engineering Laboratory for Digital Construction and Evaluation Technology of Urban Rail Tran-sit(No.2021HJ01)Tianjin University Innovation Project(No.2020YJSB087).
文摘Radiative cooling without energy consumption and environmental pollution holds great promise as the next-generation cooling technology.To date,daytime radiative cooling performance is still slightly low,especially in humid areas.In this work,we demonstrated that nanoporous polyethylene(Nano PE)film can improve solar reflectivity from 96%to 99%,thus boosting radiative cooling performance.Moreover,the experimental results in humid areas indicate that Nano PE films can improve radiative cooling performance by∼76%in a clear day and 120%in a day with few clouds.Additionally,compared with ordinary PE films,thin Nano PE films have significantly higher weather fastness and mechanical strength.More importantly,nano PE films can scatter part of visible light,thus suppressing the generation of light pollution in practical applications.Lastly,the modeling results reveal that with Nano PE films,more than 95%of China’s areas can achieve daytime cooling performance.Our work can boost the development of radiative cooling technology with a very low cost.
基金supported by the Industrial-linked Low-carbon Process Conversion Core Technology Development Program (RS2022-00155175)the Materials/Parts Technology Development Program (20022507) funded by the Ministry of Trade, Industry & Energy (MOTIE, Republic of Korea)the Korea Research Institute of Chemical Technology (KRICT) core project (SS2221-20)。
文摘Passive daytime radiative cooling(PDRC) is useful for thermal management because it allows an object to emit terrestrial heat into space without the use of additional energy.To produce sub-ambient temperatures under direct sunlight,PDRC materials are designed to reduce their absorption of solar energy and to enhance their long-wavelength infrared(LWIR) emissivity.In recent years,many photonic structures and polymer composites have been studied to improve the cooling system of buildings.However,in cold weather(i.e. during winter in cold climates),buildings need to be kept warm rather than cooled due to heat loss.To overcome this limitation,temperature-responsive radiative cooling is a promising alternative.In the present study,adaptive radiative cooling(ARC) film fabricated from a polydimethylsiloxane/hollow SiO_(2) microsphere/thermochromic pigment composite was investigated.We found that the ARC film absorbed solar radiation under cold conditions while exhibiting radiative cooling at ambient temperatures above 40℃.Thus,in outdoor experiments,the ARC film achieved sub-ambient temperatures and had a theoretical cooling power of 63.2 W/m~2 in hot weather.We also demonstrated that radiative cooling with an energy harvesting system could be used to improve the energy management of buildings,with the thermoelectric module continuously generating output power using the ARC film.Therefore,we believe that our proposed ARC film can be employed for efficient thermal management of buildings and all-season energy harvesting in the near future.
基金The authors are grateful for the financial support from the National Natural Science Foundation of China(Grant Nos.52273067,52122303,52233006)the Fundamental Research Funds for the Central Universities(Grant No.2232023A-03)the Shuguang Program of Shanghai Education Development Foundation and Shanghai Municipal Education Commission(23SG29).
文摘The demand for highly porous yet transparent aerogels with mechanical flexibility and solar-thermal dual-regulation for energy-saving windows is significant but challenging.Herein,a delaminated aerogel film(DAF)is fabricated through filtration-induced delaminated gelation and ambient drying.The delaminated gelation process involves the assembly of fluorinated cellulose nanofiber(FCNF)at the solid-liquid interface between the filter and the filtrate during filtration,resulting in the formation of lamellar FCNF hydrogels with strong intra-plane and weak interlayer hydrogen bonding.By exchanging the solvents from water to hexane,the hydrogen bonding in the FCNF hydrogel is further enhanced,enabling the formation of the DAF with intra-layer mesopores upon ambient drying.The resulting aerogel film is lightweight and ultra-flexible,which pos-sesses desirable properties of high visible-light transmittance(91.0%),low thermal conductivity(33 mW m^(-1) K^(-1)),and high atmospheric-window emissivity(90.1%).Furthermore,the DAF exhibits reduced surface energy and exceptional hydrophobicity due to the presence of fluorine-containing groups,enhancing its durability and UV resistance.Consequently,the DAF has demonstrated its potential as solar-thermal regulatory cooling window materials capable of simultaneously providing indoor lighting,thermal insulation,and daytime radiative cooling under direct sunlight.Significantly,the enclosed space protected by the DAF exhibits a temperature reduction of 2.6℃ compared to that shielded by conventional architectural glass.
基金Financial support from the Ministry of Science and Technology,China(grant No.ZK20210004)the Department of Science and Technology of Shandong Province,China(grant No.ZK20200026)the National Natural Science Foundation of China(grant No.52176175),are gratefully acknowledged.
文摘Global warming has become one of the major environmental problems facing mankind in the 21st century,The existing refrigeration technology of buildings,like air conditioning,consumes a lot of energy.Passive daytime radiative cooling technology works without consuming energy.nor emitting carbon dioxide and other greenhouse gases.This review summarizes the development of daytime passive radiative cooling technologyfrom the basic principles,structure and materials of radiative coolers;analyses and evaluates the various existing radiative coolers.The core of radiative cooling lies in the combination of multi-scale micro/nano structures.The cooler reflects sunlight thus preventing the building from being heated up;while allows the building toradiate its own heat out thus being cooled down;meanwhile maintains the temperature difference by the heat insulation effect ofthe porous structure in theflm.The common challenges and potential solutions for the commercialization of radiative cooling technologies are analyzed,which may promote the applications of the technology in the near future.
基金financially supported by the National Natural Science Foundation of China(No.52273067)the Fundamental Research Funds for the Central Universities(No.2232023A-03)the Shuguang Program of Shanghai Education Development Foundation and Shanghai Municipal Education Commission(No.23SG29)。
文摘Passive daytime radiative cooling(PDRC)is an innovative and sustainable cooling technology that holds immense potential for addressing the energy crisis.Despite the numerous reports on radiative coolers,the design of a straightforward,efficient,and readily producible system remains a challenge.Herein,we present the development of a hierarchical aligned porous poly(vinylidene fluoride)(HAP-PVDF)film through a freeze-thaw-promoted nonsolvent-induced phase separation strategy.This film features oriented microporous arrays in conjunction with random nanopores,enabling efficient radiative cooling performance under direct sunlight conditions.The incorporation of both micro-and nano-pores in the HAP-PVDF film results in a remarkable solar reflectance of 97%and a sufficiently high infrared thermal emissivity of 96%,facilitating sub-environmental cooling at 18.3℃ on sunny days and 13.1℃ on cloudy days.Additionally,the HAP-PVDF film also exhibits exceptional flexibility and hydrophobicity.Theoretical calculations further confirm a radiative cooling power of 94.8 W·m^(-2)under a solar intensity of 1000W·m^(-2),demonstrating a performance comparable to the majority of reported radiative coolers.
