Particle engineering has opened the floodgates to material science in both fundamental and application field. However, covalent interactions have not yet been adequately designed in the particle engineering for functi...Particle engineering has opened the floodgates to material science in both fundamental and application field. However, covalent interactions have not yet been adequately designed in the particle engineering for functional colloidal photonic crystals(CPCs). Herein, we achieved covalent coupling between carboxylrich poly(styrene-acrylic acid)(P(St-AA)) monodispersed colloidal particles and amine-rich carbon dots(CDs) based on an feasible and universal particle engineering strategy. The designed CDs-grafted P(St-AA)monodispersed colloidal particles initiate a hydrogen bond-driven assembly mode and ensure the construction of large-scale crack-free CPCs. Moreover, the CDs equipped with selective broad-band absorption capacity could improve the saturation of structural colors for high-visibility CPCs. Furthermore, an injectable photonic hydrogel(IPH) is developed to design CPC supraball hydrogel via integrating the CDsgrafted P(St-AA) CPC supraballs with supramolecular hydrogel. Combining superior flexibility, sufficient self-healing capacity of supramolecular hydrogel with visual optical information of our CPC supraballs, a cyclically reversible coding and decoding system was developed. Meanwhile, we firstly demonstrated the novel strategy of 3D supraballs-based passive cooling. The designed 3D CPC supraball hydrogel presents nearly full observation angle reflections behavior and excellent water evaporation capacity and achieves3.6 ℃ temperature drops, showing the application advantages in 3D thermal management. This work not only provides a new insight for manipulating optical properties of CPCs, but also demonstrates an easyto-perform platform, as well as indicates the direction for the promising application of CPCs.展开更多
This paper will present several passive-cooling technologies and design features that can be adopted to reduce building heat gain without the need of excess energy consumption. A typical residential unit will be selec...This paper will present several passive-cooling technologies and design features that can be adopted to reduce building heat gain without the need of excess energy consumption. A typical residential unit will be selected as case study and a three basic passive cooling strategies were selected to enhance the building envelop, as well as using appropriate shading devices and green roofing system that prove to be a good environment quality improver. IES energy simulation software will be used to evaluate the performance of the building. The study revealed a number of significant findings in reducing the energy consumption and enhancing the tenants＇ thermal comfort. American Society of Heating Refrigerating and Airconditioning Engineer （ASHRAE） standards specially via improving the performance of building envelop because it is the interface between internal and external environment. Moreover, improving the building envelope has recorded that overall energy and chiller energy consumption can be reduced up to 10.8% and 21.6% respectively, Therefore, it is anticipated that further reductions can be achieved via applying more passive cooling strategies. Finally, it could argue that the results of this paper will not only be applicable to Bahrain but also many countries that have similar climatic and environmental context.展开更多
<div style="text-align:justify;"> With rising health risks escalating from temperatures in the Global South, the shortage of essential indoor cooling is frequently seen as a dimension of energy poverty...<div style="text-align:justify;"> With rising health risks escalating from temperatures in the Global South, the shortage of essential indoor cooling is frequently seen as a dimension of energy poverty and human wellbeing. As a result, this study assessed ventilation and passive cooling in Jakande, Lagos Housing estate to design social housing that integrates proper cross ventilation and cooling. A total of 1215 housing units in the estate were used for the sampling frame. Based on the survey, the authors proposed an analytical housing design equipped with urban greenery that allows for free air movement with minimal thermal discomfort. The design methodology aids continuous cooling within the housing envelope and also improves aesthetics and landscaping within the environment. </div>展开更多
The solar chimney can generate airflow through the living space of the building to provide cooling. Hence, solar energy represents the best renewable, environmentally friendly source of energy that can be used for hea...The solar chimney can generate airflow through the living space of the building to provide cooling. Hence, solar energy represents the best renewable, environmentally friendly source of energy that can be used for heating and cooling of houses. The present paper reports the numerical study of the performance of the mixed convection in the associated hybrid Photovoltaic/Thermal chimneys integrated into building for natural habitat ventilation. The front side glass plate of the chimneys is heated by a non-uniform daily solar radiation flux. Air is considered to be the cooling fluid. The stream fucntion-vorticity formulation with a finite difference numerical discretization solution scheme has been adopted. The system of algebraic governing equations is solved by Thomas algorithm method. The aim of the present paper is to study and to predict the dynamic fields and particularly of the mass flow rate of the air thermosiphon drawing in the associated hybrid Photovoltaic-Thermal chimneys integrated into a building for passive cooling in the habitats. The effects of the governing parameters, namely Reynolds number (30 ≤ Re ≤ 200), Rayleigh number (103 ≤ Ra≤ 105), the integrated chimney width on the fluid flow and the heat transfer characteristics, are studied in detail. The local Nusselt number, streamlines, isotherms, PV cells electrical efficiency and the outlet velocity at the top of the channels are the results represented versus the above controlling parameters.展开更多
An experimental investigation of passive cooling buildings has been carried out for a typical summer days extended from July to December of Baghdad in Iraq. Six independent chambers were designed and constructed for d...An experimental investigation of passive cooling buildings has been carried out for a typical summer days extended from July to December of Baghdad in Iraq. Six independent chambers were designed and constructed for different roof constructions. Night ventilation has been applied to study the possibility of reducing air temperature in buildings by testing different air changes per hour extended from 5 to 30. Measurements outside chambers including air temperature; relative humidity and solar radiation were achieved, while surface temperature and air temperature inside the chambers were recorded. The results show that the air temperature can be decreased with a range from 3 ℃ to 6 ℃ when using 50 mm polystyrene. This decrease can further be lowered by 2 ℃ to 4 ℃ if night ventilation of change per hours in buildings is allowed. The reduction in air temperature can be reduced to 5 ℃ by combination of external night ventilation and white paint.展开更多
Radiative cooling fabric creates a thermally comfortable environment without energy input,providing a sustainable approach to personal thermal management.However,most currently reported fabrics mainly focus on outdoor...Radiative cooling fabric creates a thermally comfortable environment without energy input,providing a sustainable approach to personal thermal management.However,most currently reported fabrics mainly focus on outdoor cooling,ignoring to achieve simultaneous cooling both indoors and outdoors,thereby weakening the overall cooling performance.Herein,a full-scale structure fabric with selective emission properties is constructed for simultaneous indoor and outdoor cooling.The fabric achieves 94%reflectance performance in the sunlight band(0.3–2.5μm)and 6%in the mid-infrared band(2.5–25μm),effectively minimizing heat absorption and radiation release obstruction.It also demonstrates 81%radiative emission performance in the atmospheric window band(8–13μm)and 25%radiative transmission performance in the mid-infrared band(2.5–25μm),providing 60 and 26 W m−2 net cooling power outdoors and indoors.In practical applications,the fabric achieves excellent indoor and outdoor human cooling,with temperatures 1.4–5.5℃ lower than typical polydimethylsiloxane film.This work proposes a novel design for the advanced radiative cooling fabric,offering significant potential to realize sustainable personal thermal management.展开更多
Passive design responds to local climate and site conditions in order to maximise the comfort and health of building users while minimising energy use. The key to designing a passive building is to take best advantage...Passive design responds to local climate and site conditions in order to maximise the comfort and health of building users while minimising energy use. The key to designing a passive building is to take best advantage of the local climate. Passive cooling refers to any technologies or design features adopted to reduce the temperature of buildings without the need for power consumption. Consequently, the aim of this study is to test the usefulness of applying selected passive cooling strategies to improve thermal performance and to reduce energy consumption of residential buildings in hot arid climate settings, namely Dubai, United Arab Emirates. One case building was selected and eight passive cooling strategies were applied. Energy simulation software namely IES was used to assess the performance of the building. Solar shading performance was also assessed using Sun Cast Analysis, as a part of the IES software. Energy reduction was achieved due to both the harnessing of natural ventilation and the minimising of heat gain in line with applying good shading devices alongside the use of double glazing. Additionally, green roofing proved its potential by acting as an effective roof insulation. The study revealed several significant findings including that the total annual energy consumption of a residential building in Dubai may be reduced by up to 23.6% when a building uses passive cooling strategies.展开更多
Nowadays,the application of renewable energies such as solar energy in the building sector has increased notably considering the adverse impacts of climate change on human life;hence many studies have focused on the a...Nowadays,the application of renewable energies such as solar energy in the building sector has increased notably considering the adverse impacts of climate change on human life;hence many studies have focused on the application of photovoltaic panels in buildings.In the current study,a 3D computational fluid dynamics(CFD)model has been developed to evaluate the performance of a newly designed building-integrated photovoltaic(BIPV)system.Given the negative influence of overheating on the lifespan and performance of PV panels,their passive air cooling has been studied.Further,the potential of rooftop-mounted solar panels in passive ventilation of buildings by generating natural convective currents has been explored.The developed CFD model takes into consideration the effects of radiation,conduction,and buoyancy-driven natural convective currents generated by solar PV panels which are heated due to the exposure to solar radiation heat flux.The results suggest that applying a high surface emissivity for the part of the roof beneath the PV panels intensifies the natural convective currents which in turn provides better cooling for PV panels with higher cooling effects at higher solar heat fluxes.Up to a 34%increase in the convective mass flow rate and a 3 K decrease in the mean temperature of the panels were attained by modifying the emissivity of roof surface.Such a 3 K decrease in the operating temperature of the PV panels can enhance their efficiency and lifespan by about 1.56%and 21%,respectively.Based on the operating conditions and system characteristics,the BIPV system yielded an air change rate(ACH)in the range of 3-13 which was considered to be highly prevalent in providing the required passive ventilation for a wide range of applications.It was also observed that the flow dynamics inside the building were affected by both the amount of solar heat load incident on the solar panels and the emissivity of the roof surface behind the panels.展开更多
Radiative cooling technologies can passively gain lower temperature than that of ambient surroundings without consuming electricity,which has emerged as potential alternatives to traditional cooling methods.However,th...Radiative cooling technologies can passively gain lower temperature than that of ambient surroundings without consuming electricity,which has emerged as potential alternatives to traditional cooling methods.However,the limitations in daytime radiation intensity with a net cooling power of less than 150 W·m^(−2) have hindered progress toward commercial practicality.Here,we report an integrated radiative and evaporative chiller(IREC)based on polyacrylamide hydrogels combined with an upper layer of breathable poly(vinylidene fluoride-co-trifluoroethylene)fibers,which achieves a record high practical average daytime cooling power of 710 W·m^(−2).The breathable fiber layer has an average emissivity of over 76%in the atmospheric window,while reflecting 90%of visible light.This IREC possesses effective daytime radiative cooling while simultaneously ensuring evaporative cooling capability,enhancing daytime passive cooling effectively.As a result,IREC presents the practicability for both personal cooling managements and industrial auxiliary cooling applications.An IREC-based patch can assist in cooling human body by 13℃ low for a long term and biocompatible use,and IREC can maintain the temperature of industrial storage facilities such as oil tanks at room temperature even under strong sunlight irradiation.This work delivers the highest performance daytime passive cooling by simultaneous infrared radiation and water evaporation,and provides a new perspective for developing highly efficient,scalable,and affordable passive cooling strategy.展开更多
Stepwell is one of the unique medieval groundwater resource structures distributed across most of all the states in India.The main purpose of constructing stepped wells was to get access to the groundwater,but was als...Stepwell is one of the unique medieval groundwater resource structures distributed across most of all the states in India.The main purpose of constructing stepped wells was to get access to the groundwater,but was also used for the storage of food,and as a summer shelter in medieval times.In tropical regions such as India,temperature is a major problem that causes thermal distress.Traditional architectural concepts were incorporated in the medieval Indian structures to achieve thermal comfort.Traditional architecture is optimization of building design to climate,adaptive crafts,and building techniques learnt over time and experience.The objective of this study is to interpret and evaluate the architectural and engineering aspects of stepwells pertaining to passive cooling techniques used in stepwells and the shelters associated with them.This paper reviews technical aspects pertaining to passive cooling in the design of stepwells,which has identified fundamental principles that can adopted for the building of various structures presently.展开更多
Passive daytime radiative cooling has great potential for energy conservation and sustainable development.Polymer-based radiative cooling materials have received much attention due to their excellent cooling performan...Passive daytime radiative cooling has great potential for energy conservation and sustainable development.Polymer-based radiative cooling materials have received much attention due to their excellent cooling performance and scalable potential.However,the use of large amounts of organic solvents,the long cycle time,and the complexity of the preparation process have limited their development.Herein,we report a two-step cold-press sintering method for the preparation of a polymer radiative cooler,which is free of organic solvents.For demonstration,a polyvinylidene fluoride-hexafluoropropylene copolymer(PVDF-HFP)coating with a solar reflectance of 97.4%and an emissivity of 0.969 within the atmospheric window is prepared,which can achieve a sub-ambient cooling phenomenon with a temperature reduction of 4.8℃.Besides,the maximal radiative cooling power of 50.2 W/m^(2)is also obtained under sunlight.After the implementation of the proposed sintered PVDF-HFP coating in buildings,more than 10%of annual energy consumption can be saved in China.This work proposes a simple,environmentally friendly,and scalable processing method for the preparation of radiative cooling materials,facilitating the large-scale application of radiative cooling technology.展开更多
Temperature-swing adsorption(TSA)is an effective technique for CO_(2) capture,but the temperature swing procedure is energy-intensive.Herein,we report a low-energy-consumption system by combining passive radiative coo...Temperature-swing adsorption(TSA)is an effective technique for CO_(2) capture,but the temperature swing procedure is energy-intensive.Herein,we report a low-energy-consumption system by combining passive radiative cooling and solar heating for the uptake of CO_(2) on commercial activated carbons(CACs).During adsorption,the adsorbents are coated with a layer of hierarchically porous poly(vinylidene fluoride-co-hexafluoropropene)[P(VdF-HFP)HP],which cools the adsorbents to a low temperature under sunlight through radiative cooling.For desorption,CACs with broad absorption of the solar spectrum are exposed to light irradiation for heating.The heating and cooling processes are completely driven by solar energy.Adsorption tests under mimicked sunlight using the CACs show that the performance of this system is comparable to that of the traditional ones.Furthermore,under real sunlight irradiation,the adsorption capacity of the CACs can be well maintained after multiple cycles.The present work may inspire the development of new temperature swing procedures with little energy consumption.展开更多
Passive daytime radiative cooling(PDRC)technology is emerging as one of the most promising solutions to the global problem of spacing cooling,but its practical application is limited due to reduced cooling effectivene...Passive daytime radiative cooling(PDRC)technology is emerging as one of the most promising solutions to the global problem of spacing cooling,but its practical application is limited due to reduced cooling effectiveness caused by daily wear and tear,as well as dirt contamination.To tackle this problem,we report a novel strategy by introducing a renewable armor structure for prolonging the anti-fouling and cooling effectiveness properties of the PDRC coatings.The armor structure is designed by decorating fluorinated hollow glass microspheres(HGM)inside rigid resin composite matrices.The HGM serve triple purposes,including providing isolated cavities for enhanced solar reflectance,reinforcing the matrices to form robust armored structures,and increasing thermal emittance.When the coatings are worn,the HGM on the surface expose their concave cavities with numerous hydrophobic fragments,generating a highly rough surface that guarantee the superhydrophobic function.The coatings show a high sunlight reflectance(0.93)and thermal emittance(0.94)in the long-wave infrared window,leading to a cooling of 5℃ below ambient temperature under high solar flux(∼900 W/m^(2)).When anti-fouling functions are reduced,they can be regenerated more than 100 cycles without compromising the PDRC function by simple wearing treatment.Furthermore,these coatings can be easily prepared using a one-pot spray method with low-cost materials,exhibit strong adhesion to a variety of substrates,and demonstrate exceptional environmental stability.Therefore,we anticipate their immediate application opportunities for spacing cooling.展开更多
The passive radiative cooling technology shows a great potential application on reducing the enormous global energy consumption.The multilayer metamaterials could enhance the radiative cooling performance.However,it i...The passive radiative cooling technology shows a great potential application on reducing the enormous global energy consumption.The multilayer metamaterials could enhance the radiative cooling performance.However,it is a challenge to design the radiative cooler.In this work,based on the particle swarm optimization(PSO)evolutionary algorithm,we develop an intelligent workflow in designing photonic radiative cooling metamaterials.Specifically,we design two 10-layer SiO_(2) radiative coolers doped by cylindrical MgF_(2) or air impurities,possessing high emissivity within the selective(8–13μm)and broadband(8–25μm)atmospheric transparency windows,respectively.Our two kinds of coolers demonstrate power density as high as 119 W/m^(2) and 132 W/m^(2) at the room temperature(300 K).Our scheme does not rely on the usage of special materials,forming high-performing metamaterials with conventional poor-performing components.This significant improvement of the emission spectra proves the effectiveness of our inverse design algorithm in boosting the discovery of high-performing functional metamaterials.展开更多
In response to thermal runaway(TR)of electric vehicles,recent attention has been focused on mitigation strategies such as efficient heat dredging in battery thermal management.Thermal management with particular focus ...In response to thermal runaway(TR)of electric vehicles,recent attention has been focused on mitigation strategies such as efficient heat dredging in battery thermal management.Thermal management with particular focus on battery cooling has been becoming increasingly significant.TR usually happened when an electric vehicle is unpowered and charged.In this state,traditional active battery cooling schemes are disabled,which can easily lead to dangerous incidents due to loss of cooling ability,and advanced passive cooling strategies are therefore gaining importance.Herein,we developed an enhanced thermal radiation material,consisting of~1μm thick multilayered nano-sheet graphene film coated upon the heat dissipation surface,thereby enhancing thermal radiation in the nanoscale.The surface was characterized on the nanoscale,and tested in a battery-cooling scenario.We found that the graphene-based coating's spectral emissivity is between 91% and 95% in the mid-infrared region,and thermal experiments consequently illustrated that graphene-based radiative cooling yielded up to15.1% temperature reduction when compared to the uncoated analogue.Using the novel graphene surface to augment a heat pipe,the temperature reduction can be further enlarged to 25.6%.The new material may contribute to transportation safety,global warming mitigation and carbon neutralization.展开更多
Passive strategies for acclimatization of buildings have been studied by several authors in many countries, especially the evaporative and radiant cooling techniques. Fiber cement tiles are very common in popular cons...Passive strategies for acclimatization of buildings have been studied by several authors in many countries, especially the evaporative and radiant cooling techniques. Fiber cement tiles are very common in popular constructions due to their low cost. However, they have over twice of the value thermal transmittance indicated to this bioclimatic zone according to Brazilian guidelines. The objective is to present an alternative to reduce high temperatures on fiber cement tiles. In this paper, the monitoring of passive cooling of roofing during the spring season in a city with subtropical climate is described. Single and combined reflective and evaporative cooling systems were studied in different environmental conditions. Internal surface temperatures of tiles were monitored together with weather variables. Results show a decrease of about 6 ℃, 9 ℃, 10 ℃ and 11 ℃ as compared to the original tiles according to environment conditions and the combined passive cooling techniques. These results allow for the conclusion that the use of passive cooling techniques opens up new possibilities to attenuate the internal surface temperatures of tiles and to consequently decrease the roofing solar heat gain into buildings, thus, providing less air cooling energy consumption.展开更多
Epidermal electronics with superb passive-cooling capabilities are of great value for both daytime outdoor dressing comfort and low-carbon economy. Herein, a multifunctional and skinattachable electronic is rationally...Epidermal electronics with superb passive-cooling capabilities are of great value for both daytime outdoor dressing comfort and low-carbon economy. Herein, a multifunctional and skinattachable electronic is rationally developed on a porous all-elastomer metafabric for efficient passive daytime radiative cooling(PDRC) and human electrophysiological monitoring. The cooling characteristics are realized through the homogeneous impregnation of polytetrafluoroethylene microparticles in the styrene–ethylene–butylene–styrene fibers, and the rational regulation of microporosity in SEBS/PTFE metafabrics, thus synergistically backscatter ultraviolet–visible–near-infrared light(maximum reflectance over 98.0%) to minimize heat absorption while efficiently emit human-body midinfrared radiation to the sky. As a result, the developed PDRC metafabric achieves approximately 17℃ cooling effects in an outdoor daytime environment and completely retains its passive cooling performance even under 50% stretching. Further, high-fidelity electrophysiological monitoring capability is also implemented in the breathable and skin-conformal metafabric through liquid metal printing, enabling the accurate acquisition of human electrocardiograph, surface electromyogram, and electroencephalograph signals for comfortable and lengthy health regulation. Hence, the fabricated superelastic PDRC metafabric opens a new avenue for the development of body-comfortable electronics and low-carbon wearing technologies.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
Integrating passive radiative cooling techniques with wearable fabrics provides a zero-energy strategy for preventing people from heat stress and reducing cooling demand.However,developing wearable passive radiative c...Integrating passive radiative cooling techniques with wearable fabrics provides a zero-energy strategy for preventing people from heat stress and reducing cooling demand.However,developing wearable passive radiative cooling fabrics with ideal optical characteristics,wearability,and scalability has consistently presented a challenge.Here,we developed a metafabric with high sunlight reflectivity(88.07%)according to the design of an individual photonic structure,which demonstrates total internal reflection with the tailored triangular light track.A skin simulator covered by metafabric exhibits a temperature drop of 7.17℃ in the daytime compared with regular polyester fabric in an outdoor cooling test.Consequently,it was theoretically proven to exert a substantial influence on achieving a significant cooling demand reduction of 52.69–185.79 W·m^(-2).These characteristics,coupled with structural stability,air-moisture permeability,sufficient wearability,and scalability,allowed the metafabric to provide a solution for introducing zero-energy passive radiative cooling technique into human body cooling.展开更多
With the increasing global energy consumption and cooling demands,traditional active cooling technologies face inefficiency and environmental challenges.Recently published in Science,a team led by Prof.Hai-bo Zhao has...With the increasing global energy consumption and cooling demands,traditional active cooling technologies face inefficiency and environmental challenges.Recently published in Science,a team led by Prof.Hai-bo Zhao has proposed and developed a biomass-based photoluminescent aerogel made from DNA and gelatin to address these challenges.This material achieves a solar-weighted reflectance of over 100%(0.4-0.8μm)and provides a cooling effect of 16.0℃under sunlight.This sustainable material is repairable,recyclable,and biodegradable,offering significant potential for energy-efficient buildings and wearable cooling devices.展开更多
基金supported by the National Natural Science Foundation of China (No.22278225)Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD)。
文摘Particle engineering has opened the floodgates to material science in both fundamental and application field. However, covalent interactions have not yet been adequately designed in the particle engineering for functional colloidal photonic crystals(CPCs). Herein, we achieved covalent coupling between carboxylrich poly(styrene-acrylic acid)(P(St-AA)) monodispersed colloidal particles and amine-rich carbon dots(CDs) based on an feasible and universal particle engineering strategy. The designed CDs-grafted P(St-AA)monodispersed colloidal particles initiate a hydrogen bond-driven assembly mode and ensure the construction of large-scale crack-free CPCs. Moreover, the CDs equipped with selective broad-band absorption capacity could improve the saturation of structural colors for high-visibility CPCs. Furthermore, an injectable photonic hydrogel(IPH) is developed to design CPC supraball hydrogel via integrating the CDsgrafted P(St-AA) CPC supraballs with supramolecular hydrogel. Combining superior flexibility, sufficient self-healing capacity of supramolecular hydrogel with visual optical information of our CPC supraballs, a cyclically reversible coding and decoding system was developed. Meanwhile, we firstly demonstrated the novel strategy of 3D supraballs-based passive cooling. The designed 3D CPC supraball hydrogel presents nearly full observation angle reflections behavior and excellent water evaporation capacity and achieves3.6 ℃ temperature drops, showing the application advantages in 3D thermal management. This work not only provides a new insight for manipulating optical properties of CPCs, but also demonstrates an easyto-perform platform, as well as indicates the direction for the promising application of CPCs.
文摘This paper will present several passive-cooling technologies and design features that can be adopted to reduce building heat gain without the need of excess energy consumption. A typical residential unit will be selected as case study and a three basic passive cooling strategies were selected to enhance the building envelop, as well as using appropriate shading devices and green roofing system that prove to be a good environment quality improver. IES energy simulation software will be used to evaluate the performance of the building. The study revealed a number of significant findings in reducing the energy consumption and enhancing the tenants＇ thermal comfort. American Society of Heating Refrigerating and Airconditioning Engineer （ASHRAE） standards specially via improving the performance of building envelop because it is the interface between internal and external environment. Moreover, improving the building envelope has recorded that overall energy and chiller energy consumption can be reduced up to 10.8% and 21.6% respectively, Therefore, it is anticipated that further reductions can be achieved via applying more passive cooling strategies. Finally, it could argue that the results of this paper will not only be applicable to Bahrain but also many countries that have similar climatic and environmental context.
文摘<div style="text-align:justify;"> With rising health risks escalating from temperatures in the Global South, the shortage of essential indoor cooling is frequently seen as a dimension of energy poverty and human wellbeing. As a result, this study assessed ventilation and passive cooling in Jakande, Lagos Housing estate to design social housing that integrates proper cross ventilation and cooling. A total of 1215 housing units in the estate were used for the sampling frame. Based on the survey, the authors proposed an analytical housing design equipped with urban greenery that allows for free air movement with minimal thermal discomfort. The design methodology aids continuous cooling within the housing envelope and also improves aesthetics and landscaping within the environment. </div>
文摘The solar chimney can generate airflow through the living space of the building to provide cooling. Hence, solar energy represents the best renewable, environmentally friendly source of energy that can be used for heating and cooling of houses. The present paper reports the numerical study of the performance of the mixed convection in the associated hybrid Photovoltaic/Thermal chimneys integrated into building for natural habitat ventilation. The front side glass plate of the chimneys is heated by a non-uniform daily solar radiation flux. Air is considered to be the cooling fluid. The stream fucntion-vorticity formulation with a finite difference numerical discretization solution scheme has been adopted. The system of algebraic governing equations is solved by Thomas algorithm method. The aim of the present paper is to study and to predict the dynamic fields and particularly of the mass flow rate of the air thermosiphon drawing in the associated hybrid Photovoltaic-Thermal chimneys integrated into a building for passive cooling in the habitats. The effects of the governing parameters, namely Reynolds number (30 ≤ Re ≤ 200), Rayleigh number (103 ≤ Ra≤ 105), the integrated chimney width on the fluid flow and the heat transfer characteristics, are studied in detail. The local Nusselt number, streamlines, isotherms, PV cells electrical efficiency and the outlet velocity at the top of the channels are the results represented versus the above controlling parameters.
文摘An experimental investigation of passive cooling buildings has been carried out for a typical summer days extended from July to December of Baghdad in Iraq. Six independent chambers were designed and constructed for different roof constructions. Night ventilation has been applied to study the possibility of reducing air temperature in buildings by testing different air changes per hour extended from 5 to 30. Measurements outside chambers including air temperature; relative humidity and solar radiation were achieved, while surface temperature and air temperature inside the chambers were recorded. The results show that the air temperature can be decreased with a range from 3 ℃ to 6 ℃ when using 50 mm polystyrene. This decrease can further be lowered by 2 ℃ to 4 ℃ if night ventilation of change per hours in buildings is allowed. The reduction in air temperature can be reduced to 5 ℃ by combination of external night ventilation and white paint.
基金financially supported by Heilongjiang Postdoctoral Fund(Grant No.LBH-Z24057)Outstanding Master’s and Doctoral Thesis of Longjiang in the New Era(Grant No.LJYXL2023-076).
文摘Radiative cooling fabric creates a thermally comfortable environment without energy input,providing a sustainable approach to personal thermal management.However,most currently reported fabrics mainly focus on outdoor cooling,ignoring to achieve simultaneous cooling both indoors and outdoors,thereby weakening the overall cooling performance.Herein,a full-scale structure fabric with selective emission properties is constructed for simultaneous indoor and outdoor cooling.The fabric achieves 94%reflectance performance in the sunlight band(0.3–2.5μm)and 6%in the mid-infrared band(2.5–25μm),effectively minimizing heat absorption and radiation release obstruction.It also demonstrates 81%radiative emission performance in the atmospheric window band(8–13μm)and 25%radiative transmission performance in the mid-infrared band(2.5–25μm),providing 60 and 26 W m−2 net cooling power outdoors and indoors.In practical applications,the fabric achieves excellent indoor and outdoor human cooling,with temperatures 1.4–5.5℃ lower than typical polydimethylsiloxane film.This work proposes a novel design for the advanced radiative cooling fabric,offering significant potential to realize sustainable personal thermal management.
文摘Passive design responds to local climate and site conditions in order to maximise the comfort and health of building users while minimising energy use. The key to designing a passive building is to take best advantage of the local climate. Passive cooling refers to any technologies or design features adopted to reduce the temperature of buildings without the need for power consumption. Consequently, the aim of this study is to test the usefulness of applying selected passive cooling strategies to improve thermal performance and to reduce energy consumption of residential buildings in hot arid climate settings, namely Dubai, United Arab Emirates. One case building was selected and eight passive cooling strategies were applied. Energy simulation software namely IES was used to assess the performance of the building. Solar shading performance was also assessed using Sun Cast Analysis, as a part of the IES software. Energy reduction was achieved due to both the harnessing of natural ventilation and the minimising of heat gain in line with applying good shading devices alongside the use of double glazing. Additionally, green roofing proved its potential by acting as an effective roof insulation. The study revealed several significant findings including that the total annual energy consumption of a residential building in Dubai may be reduced by up to 23.6% when a building uses passive cooling strategies.
文摘Nowadays,the application of renewable energies such as solar energy in the building sector has increased notably considering the adverse impacts of climate change on human life;hence many studies have focused on the application of photovoltaic panels in buildings.In the current study,a 3D computational fluid dynamics(CFD)model has been developed to evaluate the performance of a newly designed building-integrated photovoltaic(BIPV)system.Given the negative influence of overheating on the lifespan and performance of PV panels,their passive air cooling has been studied.Further,the potential of rooftop-mounted solar panels in passive ventilation of buildings by generating natural convective currents has been explored.The developed CFD model takes into consideration the effects of radiation,conduction,and buoyancy-driven natural convective currents generated by solar PV panels which are heated due to the exposure to solar radiation heat flux.The results suggest that applying a high surface emissivity for the part of the roof beneath the PV panels intensifies the natural convective currents which in turn provides better cooling for PV panels with higher cooling effects at higher solar heat fluxes.Up to a 34%increase in the convective mass flow rate and a 3 K decrease in the mean temperature of the panels were attained by modifying the emissivity of roof surface.Such a 3 K decrease in the operating temperature of the PV panels can enhance their efficiency and lifespan by about 1.56%and 21%,respectively.Based on the operating conditions and system characteristics,the BIPV system yielded an air change rate(ACH)in the range of 3-13 which was considered to be highly prevalent in providing the required passive ventilation for a wide range of applications.It was also observed that the flow dynamics inside the building were affected by both the amount of solar heat load incident on the solar panels and the emissivity of the roof surface behind the panels.
基金This work was supported by the financial support from National Natural Science Foundation of China(Nos.52073159,22035005,52022051,22075165,and 52090030)State Key Laboratory of Tribology(No.SKLT2021B03)+1 种基金Tsinghua-Foshan Innovation Special Fund(No.2018THFS0412)This work is also supported by a grant(No.2019GQG1025)from the Institute for Guo Qiang,Tsinghua University.
文摘Radiative cooling technologies can passively gain lower temperature than that of ambient surroundings without consuming electricity,which has emerged as potential alternatives to traditional cooling methods.However,the limitations in daytime radiation intensity with a net cooling power of less than 150 W·m^(−2) have hindered progress toward commercial practicality.Here,we report an integrated radiative and evaporative chiller(IREC)based on polyacrylamide hydrogels combined with an upper layer of breathable poly(vinylidene fluoride-co-trifluoroethylene)fibers,which achieves a record high practical average daytime cooling power of 710 W·m^(−2).The breathable fiber layer has an average emissivity of over 76%in the atmospheric window,while reflecting 90%of visible light.This IREC possesses effective daytime radiative cooling while simultaneously ensuring evaporative cooling capability,enhancing daytime passive cooling effectively.As a result,IREC presents the practicability for both personal cooling managements and industrial auxiliary cooling applications.An IREC-based patch can assist in cooling human body by 13℃ low for a long term and biocompatible use,and IREC can maintain the temperature of industrial storage facilities such as oil tanks at room temperature even under strong sunlight irradiation.This work delivers the highest performance daytime passive cooling by simultaneous infrared radiation and water evaporation,and provides a new perspective for developing highly efficient,scalable,and affordable passive cooling strategy.
文摘Stepwell is one of the unique medieval groundwater resource structures distributed across most of all the states in India.The main purpose of constructing stepped wells was to get access to the groundwater,but was also used for the storage of food,and as a summer shelter in medieval times.In tropical regions such as India,temperature is a major problem that causes thermal distress.Traditional architectural concepts were incorporated in the medieval Indian structures to achieve thermal comfort.Traditional architecture is optimization of building design to climate,adaptive crafts,and building techniques learnt over time and experience.The objective of this study is to interpret and evaluate the architectural and engineering aspects of stepwells pertaining to passive cooling techniques used in stepwells and the shelters associated with them.This paper reviews technical aspects pertaining to passive cooling in the design of stepwells,which has identified fundamental principles that can adopted for the building of various structures presently.
基金supported by the National Natural Science Foundation of China(NSFC 52130601 and 52106276)the Young Elite Scientists Sponsorship Program by CAST(2023QNRC001)+1 种基金the University of Science and Technology of China-Southwest University of Science and Technology Counterpart Cooperation and Development Joint Fund(24LHJJ09)the USTC Center for Micro and Nanoscale Research and Fabrication。
文摘Passive daytime radiative cooling has great potential for energy conservation and sustainable development.Polymer-based radiative cooling materials have received much attention due to their excellent cooling performance and scalable potential.However,the use of large amounts of organic solvents,the long cycle time,and the complexity of the preparation process have limited their development.Herein,we report a two-step cold-press sintering method for the preparation of a polymer radiative cooler,which is free of organic solvents.For demonstration,a polyvinylidene fluoride-hexafluoropropylene copolymer(PVDF-HFP)coating with a solar reflectance of 97.4%and an emissivity of 0.969 within the atmospheric window is prepared,which can achieve a sub-ambient cooling phenomenon with a temperature reduction of 4.8℃.Besides,the maximal radiative cooling power of 50.2 W/m^(2)is also obtained under sunlight.After the implementation of the proposed sintered PVDF-HFP coating in buildings,more than 10%of annual energy consumption can be saved in China.This work proposes a simple,environmentally friendly,and scalable processing method for the preparation of radiative cooling materials,facilitating the large-scale application of radiative cooling technology.
基金supported by the National Science Fund for Distinguished Young Scholars(22125804)the National Natural Science Foundation of China(21808110,22078155,and 21878149).
文摘Temperature-swing adsorption(TSA)is an effective technique for CO_(2) capture,but the temperature swing procedure is energy-intensive.Herein,we report a low-energy-consumption system by combining passive radiative cooling and solar heating for the uptake of CO_(2) on commercial activated carbons(CACs).During adsorption,the adsorbents are coated with a layer of hierarchically porous poly(vinylidene fluoride-co-hexafluoropropene)[P(VdF-HFP)HP],which cools the adsorbents to a low temperature under sunlight through radiative cooling.For desorption,CACs with broad absorption of the solar spectrum are exposed to light irradiation for heating.The heating and cooling processes are completely driven by solar energy.Adsorption tests under mimicked sunlight using the CACs show that the performance of this system is comparable to that of the traditional ones.Furthermore,under real sunlight irradiation,the adsorption capacity of the CACs can be well maintained after multiple cycles.The present work may inspire the development of new temperature swing procedures with little energy consumption.
基金supported by the National Natural Science Foundation of China(Nos.52003035,52203135 and 51973023)the CHN Energy Group Project(No.GJNY-21-183).
文摘Passive daytime radiative cooling(PDRC)technology is emerging as one of the most promising solutions to the global problem of spacing cooling,but its practical application is limited due to reduced cooling effectiveness caused by daily wear and tear,as well as dirt contamination.To tackle this problem,we report a novel strategy by introducing a renewable armor structure for prolonging the anti-fouling and cooling effectiveness properties of the PDRC coatings.The armor structure is designed by decorating fluorinated hollow glass microspheres(HGM)inside rigid resin composite matrices.The HGM serve triple purposes,including providing isolated cavities for enhanced solar reflectance,reinforcing the matrices to form robust armored structures,and increasing thermal emittance.When the coatings are worn,the HGM on the surface expose their concave cavities with numerous hydrophobic fragments,generating a highly rough surface that guarantee the superhydrophobic function.The coatings show a high sunlight reflectance(0.93)and thermal emittance(0.94)in the long-wave infrared window,leading to a cooling of 5℃ below ambient temperature under high solar flux(∼900 W/m^(2)).When anti-fouling functions are reduced,they can be regenerated more than 100 cycles without compromising the PDRC function by simple wearing treatment.Furthermore,these coatings can be easily prepared using a one-pot spray method with low-cost materials,exhibit strong adhesion to a variety of substrates,and demonstrate exceptional environmental stability.Therefore,we anticipate their immediate application opportunities for spacing cooling.
基金the National Natural Science Foundation of China(Grant No.11935010)the Opening Project of Shanghai Key Laboratory of Special Artificial Microstructure Materials and Technology。
文摘The passive radiative cooling technology shows a great potential application on reducing the enormous global energy consumption.The multilayer metamaterials could enhance the radiative cooling performance.However,it is a challenge to design the radiative cooler.In this work,based on the particle swarm optimization(PSO)evolutionary algorithm,we develop an intelligent workflow in designing photonic radiative cooling metamaterials.Specifically,we design two 10-layer SiO_(2) radiative coolers doped by cylindrical MgF_(2) or air impurities,possessing high emissivity within the selective(8–13μm)and broadband(8–25μm)atmospheric transparency windows,respectively.Our two kinds of coolers demonstrate power density as high as 119 W/m^(2) and 132 W/m^(2) at the room temperature(300 K).Our scheme does not rely on the usage of special materials,forming high-performing metamaterials with conventional poor-performing components.This significant improvement of the emission spectra proves the effectiveness of our inverse design algorithm in boosting the discovery of high-performing functional metamaterials.
基金supported by the National Natural Science Foundation of China(no.52106114)Beijing Natural Science Foundation(no.3234061)Hong Kong Scholars Program(no.XJ2022027)。
文摘In response to thermal runaway(TR)of electric vehicles,recent attention has been focused on mitigation strategies such as efficient heat dredging in battery thermal management.Thermal management with particular focus on battery cooling has been becoming increasingly significant.TR usually happened when an electric vehicle is unpowered and charged.In this state,traditional active battery cooling schemes are disabled,which can easily lead to dangerous incidents due to loss of cooling ability,and advanced passive cooling strategies are therefore gaining importance.Herein,we developed an enhanced thermal radiation material,consisting of~1μm thick multilayered nano-sheet graphene film coated upon the heat dissipation surface,thereby enhancing thermal radiation in the nanoscale.The surface was characterized on the nanoscale,and tested in a battery-cooling scenario.We found that the graphene-based coating's spectral emissivity is between 91% and 95% in the mid-infrared region,and thermal experiments consequently illustrated that graphene-based radiative cooling yielded up to15.1% temperature reduction when compared to the uncoated analogue.Using the novel graphene surface to augment a heat pipe,the temperature reduction can be further enlarged to 25.6%.The new material may contribute to transportation safety,global warming mitigation and carbon neutralization.
文摘Passive strategies for acclimatization of buildings have been studied by several authors in many countries, especially the evaporative and radiant cooling techniques. Fiber cement tiles are very common in popular constructions due to their low cost. However, they have over twice of the value thermal transmittance indicated to this bioclimatic zone according to Brazilian guidelines. The objective is to present an alternative to reduce high temperatures on fiber cement tiles. In this paper, the monitoring of passive cooling of roofing during the spring season in a city with subtropical climate is described. Single and combined reflective and evaporative cooling systems were studied in different environmental conditions. Internal surface temperatures of tiles were monitored together with weather variables. Results show a decrease of about 6 ℃, 9 ℃, 10 ℃ and 11 ℃ as compared to the original tiles according to environment conditions and the combined passive cooling techniques. These results allow for the conclusion that the use of passive cooling techniques opens up new possibilities to attenuate the internal surface temperatures of tiles and to consequently decrease the roofing solar heat gain into buildings, thus, providing less air cooling energy consumption.
基金financially supported by the National Natural Science Foundation of China (21875033, 52161135302)the Research Foundation Flanders (G0F2322N)+4 种基金the China Postdoctoral Science Foundation (2022M711355)the Natural Science Foundation of Jiangsu Province (BK20221540)the Shanghai Scientific and Technological Innovation Project (18JC1410600)the Program of the Shanghai Academic Research Leader (17XD1400100)the Postgraduate Research & Practice Innovation Program of Jiangsu Province (KYCX22_2317)。
文摘Epidermal electronics with superb passive-cooling capabilities are of great value for both daytime outdoor dressing comfort and low-carbon economy. Herein, a multifunctional and skinattachable electronic is rationally developed on a porous all-elastomer metafabric for efficient passive daytime radiative cooling(PDRC) and human electrophysiological monitoring. The cooling characteristics are realized through the homogeneous impregnation of polytetrafluoroethylene microparticles in the styrene–ethylene–butylene–styrene fibers, and the rational regulation of microporosity in SEBS/PTFE metafabrics, thus synergistically backscatter ultraviolet–visible–near-infrared light(maximum reflectance over 98.0%) to minimize heat absorption while efficiently emit human-body midinfrared radiation to the sky. As a result, the developed PDRC metafabric achieves approximately 17℃ cooling effects in an outdoor daytime environment and completely retains its passive cooling performance even under 50% stretching. Further, high-fidelity electrophysiological monitoring capability is also implemented in the breathable and skin-conformal metafabric through liquid metal printing, enabling the accurate acquisition of human electrocardiograph, surface electromyogram, and electroencephalograph signals for comfortable and lengthy health regulation. Hence, the fabricated superelastic PDRC metafabric opens a new avenue for the development of body-comfortable electronics and low-carbon wearing technologies.
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supported by the Ministry of Industry and Information Technology,the PRC National Development and Reform Commission,the Fundamental Research Funds for the Central Universities(No.2232020A-06)the Science and Technology Commission of Shanghai Municipality(No.21130750100,No.22dz1200102)the National Natural Science Foundation of China(Nos.52373281).
文摘Integrating passive radiative cooling techniques with wearable fabrics provides a zero-energy strategy for preventing people from heat stress and reducing cooling demand.However,developing wearable passive radiative cooling fabrics with ideal optical characteristics,wearability,and scalability has consistently presented a challenge.Here,we developed a metafabric with high sunlight reflectivity(88.07%)according to the design of an individual photonic structure,which demonstrates total internal reflection with the tailored triangular light track.A skin simulator covered by metafabric exhibits a temperature drop of 7.17℃ in the daytime compared with regular polyester fabric in an outdoor cooling test.Consequently,it was theoretically proven to exert a substantial influence on achieving a significant cooling demand reduction of 52.69–185.79 W·m^(-2).These characteristics,coupled with structural stability,air-moisture permeability,sufficient wearability,and scalability,allowed the metafabric to provide a solution for introducing zero-energy passive radiative cooling technique into human body cooling.
基金supported by the National Natural Science Foundation of China(No.52373085,U21A2095)Natural Science Foundation of Hubei Province(No.2023AFA828)+3 种基金Innovative Team Program of Natural Science Foundation of Hubei Province(No.2023AFA027)Department of Science and Technology of Hubei Province(No.2024CSA076)Open Fund for Hubei Key Laboratory of Digital Textile Equipment,Wuhan Textile University(No.DTL2023022)National Local Joint Laboratory for Advanced Textile Processing and Clean Production(No.17).
文摘With the increasing global energy consumption and cooling demands,traditional active cooling technologies face inefficiency and environmental challenges.Recently published in Science,a team led by Prof.Hai-bo Zhao has proposed and developed a biomass-based photoluminescent aerogel made from DNA and gelatin to address these challenges.This material achieves a solar-weighted reflectance of over 100%(0.4-0.8μm)and provides a cooling effect of 16.0℃under sunlight.This sustainable material is repairable,recyclable,and biodegradable,offering significant potential for energy-efficient buildings and wearable cooling devices.
