Spectral Selectivity of CdTe Cells with Substrate Configuration for Photovoltaic/Thermal Applications

Existing photovoltaic cells with high infrared emissivity generate huge radiative heat loss in photovoltaic/thermal applications and degrade the photothermal performance.The purpose of this work is to evaluate the full spectral absorptivity of CdTe cells to find a spectrally selective photovoltaic cell for photovoltaic/thermal applications.To this end,the solar absorptivity and mid-infrared thermal emissivity of CdTe cells were tested by ellipsometry,UV-Vis-NIR spectrophotometer,and Fourier transform infrared spectrometer.The experimental results show that the AM 1.5 solar spectrum weighted absorptivity of the substrate configuration CdTe cell reaches 0.91,and the mid-infrared emissivity is only 0.29,while the superstrate configuration cell emissivity is as high as 0.9.Further research shows that substrate configuration with a transparent conductive layer on top can be flexibly grown on metal foils and has spectral selectivity with high solar absorptivity and low mid-infrared emissivity should be considered in the future for photovoltaic/thermal applications.

Selection of Spectral Data for Classification of Steels Using Laser-Induced Breakdown Spectroscopy

Principal component analysis （PCA） combined with artificial neural networks was used to classify the spectra of 27 steel samples acquired using laser-induced breakdown spectroscopy. Three methods of spectral data selection, selecting all the peak lines of the spectra, selecting intensive spectral partitions and the whole spectra, were utilized to compare the infiuence of different inputs of PCA on the classification of steels. Three intensive partitions were selected based on experience and prior knowledge to compare the classification, as the partitions can obtain the best results compared to all peak lines and the whole spectra. We also used two test data sets, mean spectra after being averaged and raw spectra without any pretreatment, to verify the results of the classification. The results of this comprehensive comparison show that a back propagation network trained using the principal components of appropriate, carefully selecred spectral partitions can obtain the best results accuracy can be achieved using the intensive spectral A perfect result with 100% classification partitions ranging of 357-367 nm.

Spectrally selective optical pumping in Doppler-broadened cesium atoms

The D1 line spectrally selective pumping process in Doppler-broadened cesium is analyzed by solving the optical Bloch equations. The process, described by a three-level model with the A scheme, shows that the saturation intensity of broadened atoms is three orders of magnitude larger than that of resting atoms. The 丨Fg = 3） →丨Fe = 4） resonance pumping can result in the ground state丨Fg = 4, mF = 4） sublevel having a maximum population of 0.157 and the population difference would be about 0.01 in two adjacent magnetic sublevels of the hyperfine （HF） state Fg = 4. To enhance the anisotropy in the ground state, we suggest employing dichromatic optical HF pumping by adding a laser to excite D1 line 丨Fg = 4） → 丨Fe = 3） transition, in which the cesium magnetometer sensitivity increases by half a magnitude and is unaffected by the nonlinear Zeeman effect even in Earth＇s average magnetic field.

Thermal Stability and Degeneration Behavior of Solar Selective Absorber Based on WTi-Al_(2)O_(3)Cermet

A WTi-Al_(2)O_(3)cermet-based solar selective absorber was prepared to investigate the atomic diffusion induced spectral selectivity degeneration.The as-deposited coating exhibits superior absorptance(0.934)and low thermal emittance(0.098),as well as excellent thermal stability with a selectivity of 0.900/0.07 even after annealing at 923 K for 400 h in Ar ambient.However,the multilayer coating failed after being subjected to annealing at 923 K for 400 h in an air environment,as indicated by a decrease in solar absorptance to 0.912 and an increase in thermal emittance to 0.634.The microstructure characterizations reveal that the annealed coating exhibits a columnar morphology along the vertical direction of the substrate.The presence of abundant grain boundaries in the multilayer coating promotes the outward diffusion of Cr and Mn atoms in the stainless-steel substrate.The Mn atoms,in particular,possess the capability to migrate towards the surface of the coating and undergo an oxidation reaction with oxygen,facilitating the formation of a thick Mn_(2)O_(3)layer.The roughness of the coating surface was significantly increased in this case,adversely affecting solar absorptance due to amplified sunlight reflection.In addition,the rocketing of thermal emittance is attributed to the destabilization of W infrared reflective layer during the annealing.These findings highlight the importance of considering the outward diffusion of Mn and Cr elements in the stainless-steel substrate when optimizing solar selective absorbers.

Experimental Study of Microalgae Cultivation under Selective Illumination by Ag/CoSO_(4)for Bioelectrode Materials Preparation

Microalgae biomass is an ideal precursor to prepare renewable carbon materials,which has broad application.The bioaccumulation efficiency(lipids,proteins,carbohydrates)and biomass productivity of microalgae are influenced by spectroscopy during the culture process.In this study,a bilayer plate-type photobioreactor was designed to cultivate Chlorella protothecoides with spectral selectivity by nanofluids.Compared to culture without spectral selectivity,the spectral selectivity of Ag/CoSO_(4)nanofluids increased microalgae biomass by 5.76%,and the spectral selectivity of CoSO_(4)solution increased by 17.14%.In addition,the spectral selectivity of Ag/CoSO_(4)nanofluids was more conducive to the accumulation of nutrients(29.46%lipids,50.66%proteins,and 17.86%carbohydrates)in microalgae.Further cultured chlorella was utilized to prepare bioelectrode materials,it was found that algal based biochar had a good pore structure(micro specific surface area:1627.5314 m^(2)/g,average pore size:0.21294 nm).As the current density was 1 A/g,the specific capacitance reached 230 F/g,appearing good electrochemical performance.

Emission Characteristics of the Side Radiation of Excited of the Layer of Alcohol Solution of Rhodamine 6G with the Round Geometric Shape

The spectral-spatial characteristics of the lateral radiation of a circular-shaped Rhodamine 6G solution layer were investigated. The layer is a part of the laser dye solution, which is in optical contact with the bottom of optical cylindrical cell, the shape of which determines the geometric shape of the exciting layer. Homogeneous excitation of this layer by the second harmonic of the Nd+: YAG (λ = 532 nm) laser is realized. Circular, plane-directed radiation, with a small, vertical, divergence was obtained from the edges of the excited layer. Is investigated experimentally the spectral and spatial characteristics of radiation. Excitation of the layer was performed from the side of the cuvette bottom. It turned out that within the concentrations of the dye in the solution from 0.12 to 0.03 wt%, the following processes are observed: 1) Plane-directed radiation, with a small vertical divergence, uniform in intensity, around the optical cell in the plane of the luminescent layer;2) An increase in the amplitude of radiation pulses with a decrease in the concentration of the dye in the solution;3) Shifting of the maximum of the emission spectrum to the short-wave region, significant narrowing of the radiation spectrum and decrease of the vertical divergence of radiation.

Superelastic Radiative Cooling Metafabric for Comfortable Epidermal Electrophysiological Monitoring

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.

A compact frequency selective stop-band splitter by using Fabry Perot nanocavity in a T-shaped waveguide

By utilizing a Fabry–Perot （FP） nanocavity adjacent to T-shaped gap waveguide ports, spectrally selective filtering is realized. When the wavelength of incident light corresponds to the resonance wavelength of the FP nanocavity, the surface plasmons are captured inside the nanocavity, and light is highly reflected from this port. The resonance wavelength is determined by using Fabry–Perot resonance condition for the nanocavity. For any desired filtering frequency the dimension of the nanocavity can be tailored. The numerical results are based on the two-dimensional finite difference time domain simulation under a perfectly matched layer absorbing boundary condition. The analytical and simulation results indicate that the proposed structure can be utilized for filtering and splitting applications.

Variable selection in near infrared spectroscopy for quantitative models of homologous analogs of cephalosporins

Two universal spectral ranges(4550-4100 cm^(-1) and 6190-5510 cm^(-1))for construction of quantitative models of homologous analogs of cephalosporins were proposed by evaluating theperformance of five spectral ranges and their combinations,using three data sets of cephalos-porins for injection,ie.,cefuroxime sodium,cetriaxone sodium and cefoperazone sodium.Subsequently,the proposed ranges were validated by using eight calibration sets of otherhomologous analogs of cephalosporins for injection,namely cefmenoxime hydrochloride,ceftezole sodium,cefmetazole,cefoxitin sodium,cefotaxime sodium,cefradine,cephazolin sodium and ceftizoxime sodium.All the constructed quantitative models for the eight kinds of cephalosporinsusing these universal ranges could fulill the requirements for quick quantification.After that,competitive adaptive reweighted sampling(CARS)algorithm and infrared(IR)-near infrared(NIR)two-dimensional(2D)correlation spectral analysis were used to determine the scientific basis of these two spectral ranges as the universal regions for the construction of quantitativemodels of cephalosporins.The CAR.S algorithm demonstrated that the ranges of 4550-4100 cm^(-1) and 6190-5510 cm^(-1) included some key wavenumbers which could be attributed to content changes of cephalosporins.The IR-NIR 2D spectral analysis showed that certain wavenumbersin these two regions have strong correlations to the structures of those cephalosporins that wereeasy to degrade.

A spectrally selective surface structure for combined photothermic conversion and radiative sky cooling

The sun and outer space are the ultimate heat and cold sources for the earth,respectively.They have significant potential for renewable energy harvesting.In this paper,a spectrally selective surface structure that has a planar polydimethylsiloxane layer covering a solar absorber is conceptually proposed and optically designed for the combination of photothermic conversion(PT)and nighttime radiative sky cooling(RC).An optical simulation is conducted whose result shows that the designed surface structure(i.e.,PT-RC surface structure)has a strong solar absorption coefficient of 0.92 and simultaneously emits as a mid-infrared spectral-selective emitter with an average emissivity of 0.84 within the atmospheric window.A thermal analysis prediction reveals that the designed PTRC surface structure can be heated to 79.1℃higher than the ambient temperature in the daytime and passively cooled below the ambient temperature of approximately 10℃in the nighttime,indicating that the designed PT-RC surface structure has the potential for integrated PT conversion and nighttime RC utilization.

Effect of the spectrally selective features of the cover and emitter combination on radiative cooling performance

Radiative cooling(RC)shows good potential for building energy saving by throwing waste heat to the cosmos in a passive and sustainable manner.However,most available radiative coolers suffer from low cooling flux.The situation becomes even deteriorated in the daytime when radiative coolers are exposed to direct sunlight.To tackle this challenge,an idea of employing both a spectrally selective cover and a spectrally selective emitter is proposed in this study as an alternative approach.A comparative study is conducted among four RC modules with different spectral characteristics for the demonstration of how the spectral profiles of the cover and the emitter affects the RC performance.The results under given conditions show that the RC module with a spectrally selective cover and a spectrally selective emitter(SC/SE)reaches a net RC power of 62.4 W/m^(2)when the solar radiation is 800 W/m^(2),which is about 1.8 times that of the typical RC module with a spectrally non-selective cover and a spectrally selective emitter(n-SC/SE).When the ambient temperature is 30°C,the SC/SE based RC module realizes a daytime sub-ambient temperature reduction of 20.0°C,standing for a further temperature decrement of 9.2°C compared to the n-SC/SE based RC module.

Performance analysis of a photovoltaic/thermal system with lunar regolith-based thermal storage for the lunar base

Powering a moon base,especially keeping it warm during the long lunar night,is a big challenge.This paper introduces a photovoltaic/thermal(PV/T)system incorporating regolith thermal storage to solve the challenge of power and heat provision for the lunar base simultaneously.The vacuum of space around the moon helps this system by reducing heat loss.During the moon's daytime,the system not only generates electricity but also captures heat.This stored heat in the regolith is then used at night,reducing the amount of equipment we need to send from Earth.The spectrally selective PV/T panels are designed to absorb a wide range of sunlight(0.3–2.5μm)while minimizing heat loss in the infrared range(3–30μm).Simulation results of the hybrid solar energy system indicate the average value of the overall efficiency is 45.9%,which relatively elevates 56.1%compared to the PV system.The launch mass of the proposed PV/T system is only 8.4%of a traditional photovoltaic-lithium battery system with the same amount of energy storage.And the total specific energy of the proposed system is 7.3 kWh kg^(-1),while that of the photovoltaic-lithium battery system is about 0.3 kWh kg^(-1).In summary,this study proposes an alternative combined heat and electricity supply system for the lunar base,which can greatly reduce the launch mass and free up load for other scientific research equipment.

Promising thermal photonic management materials for sustainable human habitat

The spectral characteristics of outdoor structures,such as automobiles,buildings,and clothing,determine their energy interaction with the environment,from broad-spectrum absorption of light energy to high-efficiency thermal emission.Recently developed spectrally selective absorption(SSA)materials permit the reduction of energy loss from human habitat eco-system in the sustainable way and further reduce the utilization of fossil energy to achieve carbon neutrality.Here we review recent advances in SSA materials that enable rational and efficient management of thermal energy and provide new solutions for the resource base that supports human life like comfortable heat management,electricity production,and water supply.The basic principles of thermal photonic management,the regulation of SSA materials,and functional properties are summarized.An outlook discussing challenges and opportunities in SSA material energy management for comfortable living environments is finally presented,which expects the enormous potential of this interdisciplinary research in solving growing resource-shortage of human society.

A review of high-temperature selective absorbing coatings for solar thermal applications

Solar selective absorbing coatings directly harvest solar energy in the form of heat.The higher temperatures are required to drive higher power-cycle efficiencies in favor of lower costs of energy.According to different dielectrics,high temperature coatings can mainly be divided to double cermet solar selective coatings,transition metal nitride multilayer coatings and transition metal oxide multilayer coatings.This paper assesses the photothermal conversion efficiency and thermal stability,and discusses the challenges and strategies of improving both thermal and optical properties.Double cermet layers can stabilize nanocrystalline structures by alloying,while transition metal nitride/oxide layers generally choose the reliable materials with superior mechanical properties and thermal stability.The purpose of this review is to get the optimized systems,and propose further research directions at higher temperature,such as all-ceramic absorbing coatings.

Design and optimization of thermally responsive autonomous dynamic glazed attachment systems for building solar heat gain control

Windows,as transparent intermediaries between the indoors and outdoors,have a significant impact on building energy consumption and indoor visual and thermal comfort.With the recent development of dynamic window structures,especially various attachment technologies,the thermal,visual,and energy performances of windows have been significantly improved.In this research,a new dynamic transparent louver structure sandwiched within conventional double-pane windows is proposed,designed,optimized,and examined in terms of energy savings in different climates.The uniqueness of the proposed design is that it autonomously responds to the seasonal needs prompted by solar heat gain through the use of thermally deflected bimetallic elements.Moreover,by integrating spectral selective louvers into the system design,the dynamic structure enables strong solar infrared modulation with a little visible variation.The optical and thermal properties of the dynamic glazing structure support about 30%and 16%seasonal variations in solar heat gains and visible transmittance,respectively.Furthermore,the potential energy savings were explored via parametric energy simulations,which showed significant potential for heating and cooling energy savings.This proposed design demonstrates a simple smart dynamic glazing structure driven by seasonal temperature differences,with significant solar heat control capabilities and minor effects on the visible or visual quality of the glazing system.

Design,fabrication and energy-saving evaluation of five-layer structure based transparent heat mirror coatings for windows application

Transparent heat mirror which allows the transmission of visible sunlight while reflects the infrared thermal energy is an effective building energy efficiency technology for hot climatic regions.In this work,a five-layer dielectric/metal/dielectric/metal/dielectric(DMDMD)coating of Si_(3)N_(4)/Ag/Si_(3)N_(4)/Ag/Si_(3)N_(4)structure is proposed.The radiative properties of the five-layer coatings are theoretically investigated by transfer matrix method.The thicknesses of the layers are optimized by using particle swarm optimization method.The sample of the designed Si_(3)N_(4)/Ag/Si_(3)N_(4)/Ag/Si_(3)N_(4)coating is prepared and the building energy performance when applying the DMDMD coating in a simple office room is also investigated,taking the hot weather condition of Guangzhou,China as an example.The simulated results show that the Tave+Rave value of the five-layer coating is 8%higher than that of the three-layer coating,and the long-wave emittance of the five-layer coating is 24.8%lower than that of the three-layer coating.And the application of the five-layer coatings on the glazed window could provide the highest energy saving rate of 8.9%when compared with the traditional low-e coatings.