As a passive cooling strategy without energy consumption, radiative cooling has attracted considerable attention, especially in the building field. Building energy simulations have been conducted to ...identify the benefits of this technology in buildings. However, in existing studies, constant emissivity was used for radiative cooling materials in the building energy simulation programs, which can cause certain errors. To tackle this problem, this study developed a method to couple the spectral-dependent radiative cooling with building energy simulations in EnergyPlus. Compared with the existing constant-emissivity model, the proposed coupled model can further consider the influence of spectral-dependent emissivity, material surface temperature, and precipitable water on the radiative cooling power in EnergyPlus. Based on the results in a typical strip mall in New York, the radiative cooling power calculated by the proposed spectral-dependent model can be significantly different from that by the existing constant-emissivity model. However, since the energy saving from radiative cooling was relatively small compared with the total energy consumption, the differences in annual cooling electricity and heating natural gas consumption calculated by both models were not significant. Furthermore, case studies in five cities using the proposed model showed that using a broadband radiative cooling roof on a typical strip mall would reduce the annual electricity consumption for cooling, while increasing the annual natural gas consumption for heating. The coupling of spectral-dependent radiative cooling with building energy simulation would improve the accuracy of energy performance assessment for buildings with radiative cooling technology.
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•Coupled spectral-dependent radiative cooling and building energy simulation was achieved.•The developed model and the existing constant-emissivity model were compared.•The energy saving and penalty from using radiative cooling roof were assessed.
As the planet warms, keeping cool without releasing greenhouse gases will be a challenge, but radiative cooling technology is poised to meet this goal. Hundreds of radiative cooling materials have ...been reported in the literature to yield acceptable cooling performance, but there is a lack of guideline for engineers to select the suitable candidates for commercialization. In order to tackle this problem, we gathered information on 55 radiative cooling materials reported in the literature according to our selection criteria and grouped them into four categories: multilayer structure, metamaterial, randomly distributed particle structure, and porous structure. Using a comparison method that objectively evaluated their cooling performance and commercialization potential, we found that the polymer-based porous structure and randomly distributed particle structure without reflective metal layer tend to be more promising for commercialization because of their superior cooling performance, low cost, ease of manufacture, high scalability and compatibility. Furthermore, we proposed an approach for the design and optimization of potential radiative cooling materials. This review will not only provide engineers with guidelines for selecting the best materials in applying and commercializing this technology, but will also enable researchers to propel this technology forward through improved material design in the future.
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•The cooling performances of 55 radiative cooling materials were evaluated.•Porous and randomly particle structure without metal layer are more promising.•An approach for the design of potential radiative cooling materials was proposed.
With advances in design and manufacturing, the cooling performance of daytime radiative cooling materials has progressively improved. However, there has not been an effective method for comparing the ...cooling performance of the materials tested in different geographical locations and laboratories. Here, we present a simulation-based method, consisting of the basic radiation theory, the standard solar spectrum, and six standard model atmospheres, for comparing the cooling performance of different daytime radiative cooling materials. The proposed simulation-based comparison method was then used to compare four representative daytime radiative cooling materials selected from the literature. The results demonstrated the effectiveness of the proposed method in comparing the cooling performance of different radiative cooling materials tested under different environmental conditions. With the proposed comparison method, the engineers can choose the most suitable daytime radiative cooling material for a specific environment.
•A method for comparing performance of different radiative cooling materials was proposed.•The method consisted radiation theory and standard solar spectrum and model atmospheres.•Representative radiative cooling materials from literature were compared using the method.
In this warming world, radiative cooling is believed to be one of the most promising techniques for keeping cool without increasing greenhouse gas emissions. Glass bubbles have been proposed as a ...component of high-performance radiative cooling paints because of the bubbles’ controllable size and their enhancement of light scattering. However, the current radiative cooling paints with glass bubbles suffer from low solar reflectivity because of their large particle size. In this study, we propose the idea of breaking the glass bubbles by means of ball milling to enhance the cooling performance of radiative cooling paints. The ball-milling process increases the solar reflectivity from 93.3% to 97.3% with the thermal emissivity of ∼93.4%, while the temperature difference with the ambient air is increased from 1.8 °C to 3.5 °C at noon. When the paint is covered with nanoporous polyethylene film, the temperature is 8.5 °C below the ambient air temperature at noon and 14.1 °C at night. The superior radiative cooling capability of the paint and the record-setting temperature difference achieved in Hong Kong demonstrate its excellent cooling performance, while the simple preparation method and ease of application make this paint promising for commercialization and large-scale production.
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•The ball milling process could increase the solar reflectivity from 93.3% to 97.3%.•The temperature difference was increased from 1.8 °C to 3.5 °C at noon.•Record-setting temperature reduction in Hong Kong was achieved.
•The ball-milling process could increase solar reflectivity from 75.8% to 95.8%.•Larger glass bubbles can be used to make high-performance radiative cooling paints.•The larger glass bubbles are over ...60% cheaper than the original glass bubbles.
Radiative cooling technology potentially can be applied to buildings to reduce cooling energy consumption. One general approach to making radiative cooling paints is to mix polymers with reflective materials. However, the high cost of materials has limited the large-scale application of radiative cooling in real scenarios. In this work, we propose another method to make high-performance radiative cooling paint, at a lower cost. This method entails ball-milling larger glass bubbles instead of the commonly used small glass bubbles. Glass bubbles with a median particle size of 47.9 μm were chosen as the component. After only 5 min of ball-milling, the median particle size was reduced to 9.7 μm. The solar reflectivity of paint made from glass bubbles after 5 min of ball-milling increased from 75.8 % (without ball-milling) to 95.8 %. In field tests, radiative cooling paint made from unground 47.9 μm glass bubbles was found to be 9.4 °C warmer than the ambient temperature at noon, while the paint made by 5 min of ball-milling of these glass bubbles achieved a temperature close to that of ambient air. Moreover, the price per unit of weight of 47.9 μm glass bubbles is only 40 % that of the previous 16.1 μm glass bubbles.
As the planet warms, keeping cool without releasing greenhouse gases is a major challenge, but radiative cooling technology is poised to meet this goal. Radiative cooling functions by simultaneously ...reflecting most of the sunlight and sending infrared thermal radiation through the atmosphere to the cold universe. As a promising cooling strategy without energy consumption, it has been attracted in both academia and industry recently. In order to provide engineers with guidelines for selecting the best materials for commercializing this technology and enable researchers to propel this technology forward through improved material designs, the modeling and analysis of radiative cooling are essential. Based on this background, this thesis aims to advance our fundamental understanding of radiative cooling technology and then propose a general approach for designing potential radiative cooling materials. A novel radiative cooling material was designed and fabricated accordingly. Then an assessment method was proposed to compare the performance of the developed radiative cooling material with that of the existing materials. In addition, a method to couple the spectral-dependent radiative cooling with the building energy simulation program EnergyPlus was developed to assess the impacts of the developed radiative cooling material on building energy consumption.Firstly, a general approach for the design and optimization of potential radiative cooling materials was proposed. The information of radiative cooling materials reported in the literature was gathered and grouped into four categories: multilayer structure, metamaterial, randomly distributed particle structure, and porous structure. Based on the database, the approach of selecting appropriate materials and corresponding simulation methods was summarized. The proposed design approach makes it possible for researchers to propel radiative cooling technology forward through improved material design in the future.According to the design approach, a novel radiative cooling material was then designed. Glass bubbles have been proposed as a component of high-performance radiative cooling paints because of the bubbles’ controllable size and their enhancement of light scattering. However, the current radiative cooling paints with glass bubbles suffer from low solar reflectivity because of their large particle size. In this study, we proposed the idea of breaking the glass bubbles by means of ball milling to enhance the cooling performance of radiative cooling paints. The ball-milling process increased the solar reflectivity from 93.3% to 97.3% with the thermal emissivity of ~93.4%, while the temperature difference with the ambient air was increased from 1.8 °C to 3.5 °C at noon. When the paint was covered with nanoporous polyethylene film, the temperature was 8.5 oC below the ambient air temperature at noon and 14.1°C at night. The superior radiative cooling capability of the paint and the record-setting temperature difference achieved in Hong Kong demonstrated its excellent cooling performance, while the simple preparation method and ease of application make this paint promising for commercialization and large-scale production.To facilitate the applications of the developed radiative cooling material, it is important to compare its performance with the existing materials. However, there has not been an effective method for comparing the cooling performance of the materials tested in different geographical locations and laboratories. In order to tackle this problem, a simulation-based method for comparing the cooling performance of different radiative cooling materials was presented. It consists of the basic radiation theory, the standard solar spectrum, and six standard model atmospheres. The proposed simulation-based comparison method was then used to compare the developed radiative cooling paint with the 55 radiative cooling materials reported in the literature. The results show that the developed radiative cooling paint was among the best in terms of cooling performance.Practical applications of the developed radiative cooling paint in buildings are expected to reduce the energy consumption for air-conditioning. To quantitatively and accurately assess the impact of radiative cooling material on building energy consumption, a method to couple the spectral-dependent radiative cooling with the building energy simulation program EnergyPlus was developed. Compared with the existing constant-emissivity model, the proposed coupled model can further consider the influence of spectral-dependent emissivity, material surface temperature, and precipitable water on the radiative cooling power in EnergyPlus. Based on the results in a typical strip mall in New York, the radiative cooling power calculated by the proposed spectral-dependent model can be significantly different from that by the existing constant-emissivity model. Therefore, the coupling of spectral-dependent radiative cooling with building energy simulation can improve the accuracy of energy performance assessment for buildings with radiative cooling technology. By using this model, it was found that the use of radiative cooling paint can significantly reduce the cooling energy consumption in strip malls in Shenzhen and Beijing.
Fluidized-carriers were supplemented into the aerobic tank of a full-scale wastewater treatment plant (WWTP) using an anaerobic/anoxic/aerobic (A2/O) system to improve the nitrogen removal efficiency ...in effluents. The effects of carrier supplementation on denitrification ability and the bacterial community structures were investigated over 10 months. The results showed that the average effluent concentration of total nitrogen (TN) was maintained at 9.46 ± 1.14 mg/L, which was lower than 15.17 ± 2.00 mg/L in the effluent without carrier supplementation, indicating that adding fluidized-carriers into the aerobic tank contributed to nitrogen removal efficiency. A thick biofilm was formed after 4 months, which provided a good anoxic-aerobic microenvironment to the microbes. Illumina sequencing analysis showed a higher bacterial diversity in the biofilm. The relative abundance of nitrifying bacteria, denitrifying bacteria, and aerobic denitrifying bacteria in the biofilms was 13.68–39%, 11.56–12.17%, and 9.76–12.50%, respectively, which was beneficial for nitrogen removal in the system. The most prevalent genera were Nitrospira, Bacillus, Thauera, Hyphomicrobium, Acinetobacter, Zoogloea, Pseudomonas, and Paracoccus, which can metabolize nitrogenous or aromatic compounds and were the major functional bacterial genera, suggesting that these organisms play key roles in biodegradation processes in the carrier-added A2/O wastewater treatment system.
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•Carriers in aerobic tank of full-scale A2/O system contributed to nitrogen removal.•The effluent TN was decreased significantly after carrier addition for 4 months.•Fluidized-carriers were beneficial for the accumulation of functional microorganisms.•Nitrospira and Bacillus genera developed in biofilm than that in suspended biomass.
Fluidized-carriers were supplemented into the aerobic tank of a full-scale wastewater treatment plant (WWTP) using an anaerobic/anoxic/aerobic (A
/O) system to improve the nitrogen removal efficiency ...in effluents. The effects of carrier supplementation on denitrification ability and the bacterial community structures were investigated over 10 months. The results showed that the average effluent concentration of total nitrogen (TN) was maintained at 9.46 ± 1.14 mg/L, which was lower than 15.17 ± 2.00 mg/L in the effluent without carrier supplementation, indicating that adding fluidized-carriers into the aerobic tank contributed to nitrogen removal efficiency. A thick biofilm was formed after 4 months, which provided a good anoxic-aerobic microenvironment to the microbes. Illumina sequencing analysis showed a higher bacterial diversity in the biofilm. The relative abundance of nitrifying bacteria, denitrifying bacteria, and aerobic denitrifying bacteria in the biofilms was 13.68-39%, 11.56-12.17%, and 9.76-12.50%, respectively, which was beneficial for nitrogen removal in the system. The most prevalent genera were Nitrospira, Bacillus, Thauera, Hyphomicrobium, Acinetobacter, Zoogloea, Pseudomonas, and Paracoccus, which can metabolize nitrogenous or aromatic compounds and were the major functional bacterial genera, suggesting that these organisms play key roles in biodegradation processes in the carrier-added A
/O wastewater treatment system.
Osteoprotegerin (OPG) is supposed to participate in the development of atherosclerosis and cardio-cerebrovascular disease. However, the results of research on relationship between OPG and ischemic ...stroke (IS) are controversial. Therefore, we carried out the first systematic review and meta-analysis to evaluate prognostic effect of osteoprotegerin in patients with IS.
We comprehensively searched databases of PubMed, Embase, and the Cochrane Library through 21 August 2023 to identify observational studies that evaluated effect of OPG on poor functional outcome (modified Rankin Scale mRS Score of 3-6) and mortality in patients with IS. Adjusted odds ratios (aOR) with a 95% confidence interval (CI) of each included study were used as much as possible to assess the pooled effect.
Five studies that enrolled 4,506 patients in total fulfilled our inclusion criteria. Three studies were included in the pooled analysis for each endpoint since one of the included studies had provided data on poor functional outcome as well as mortality. OPG was neither associated with poor functional outcome (aOR 1.29, 95% CI 0.90-1.85) nor with mortality (aOR 1.57, 95% CI 0.90-2.74) in patients with IS.
There is insufficient evidence to demonstrate the correlation between OPG and mortality or poor functional outcome in IS patients. OPG cannot be applied to predict worse neurological function in IS patients based on the current evidence.
Generative adversarial networks (GANs) are potential models in semi-supervised learning because of the excellent performance of GANs. However, most GAN-based semi-supervised models are sensitive to ...local perturbation, which means those models are not stable enough. Besides, Softmax classifier is the first choice of those models. In this paper, a novel method is proposed by introducing a discriminator using scalable SVM classifier with manifold regularization. Scalable SVM classifiers typically perform better in small sample data sets compared with other classifiers, which is consistent with the feature that semi-supervised learning consists of a few labeled data and a large number of unlabeled data. Manifold regularization forces discriminator to keep invariable to local perturbations. By incorporating into feature-matching GAN architecture, the proposed GANs-based semi-supervised learning algorithm has advantages over other methods on the Cifar-10, SVHN and Cifar-100 datasets. The results show that the proposed model SSVM-GAN has good robustness and strong generalization ability.
