Intermediate Absorbing Research Articles

Directly irradiated liquid metal film in an ultra-high temperature solar cavity receiver. Part 1: Concepts and a quasi-steady-state analysis

Solar thermal energy has the theoretical potential to deliver heat at ultra-high temperatures (>1300 K), which can enable integration with state-of-the-art thermal energy storage systems and unlock new applications, including advanced power cycles and thermal processes. Liquid metals are prospective heat transfer fluids for such systems, given their favourable thermo-physical properties, while their aggressive corrosiveness is shown to be mitigated using compatible refractory containment materials. The conventional approach of collecting concentrated solar energy typically involves intermediate solid absorbers, in form of tubes or porous structures, which are prone to thermomechanical and chemical failure under high solar radiation. This paper investigates the use of directly irradiated liquid metal (tin) film, operating between 800 and 1673 K, in two possible cavity configurations: A ‘reflective cavity’ and an ‘absorptive cavity’. The former employs cavity walls as internal reflectors to entrap radiation by secondary reflections until directly absorbed by the liquid metal. In the latter, the directly irradiated film is used to moderate the initial shot of concentrated solar radiation before diffusively reflecting them to the absorptive cavity walls, which perform as a radiative heat exchanger used to preheat the liquid metal. The concept performance is evaluated using an approximate quasi-steady-state energy model of the receiver. The reflective cavity performance is found strongly dependent on the optical properties of its internal surfaces, which resulted in poor efficiencies (<40 %) without special treatments. The absorptive cavity demonstrated higher efficiencies (>70 %) with greater insensitivity to the optical properties, hence, promoting its consideration in future developments of this concept.

A Multi-Zone Unsteady Heat Transfer Model for an Open Volumetric Air Receiver: A Step Towards Scale-Up and Design Optimization

A comprehensive, multi-zone, unsteady heat transfer model is developed for a straight absorber pore-based open volumetric air receiver. This includes heat exchange between the porous absorbers, absorbers and receiver casing, and absorbers and return air. The validation revealed its predictive capability within an uncertainty of ±7%. The model is used for the scale-up of receiver design with several intermediate absorber layers. The major recommendations for scale-up are a) multiple absorber layers is beneficial for mitigating thermal stress, b) higher flux concentration is required for non-volumetric heating, to achieve the desired air temperature, compared to volumetric heating, c) air return ratio should be 0.6, d) absorber porosity should be 0.6 for volumetric heating and higher for non-volumetric heating, e) absorber gap to length ratio should be 0.15 -0.25, f) the radiative heat loss is substantial for non-volumetric heating; therefore, the exposed surface area to ambient should be reduced, and g) absorber diameter to length ratio should be 1-2. The developed approach is generic and adaptable for the different open volumetric air receiver designs.

No Impact of Pharmacokinetics Profiles on the Clinical and Biological Response to Hydroxyurea in Children with Sickle Cell Disease

▪Hydroxyurea (HU) is an important drug for sickle cell disease (SCD) that improves clinical outcome and survival. However, its pharmacokinetics (PK) and pharmacodynamics (PD) are highly variable. HU has an excellent oral bioavailability, with half-life of 2-4 hours and renal elimination. Two oral absorption phenotypes have been identified: slow phenotype with a peak concentration reached after 60 to 120 minutes and rapid phenotype with a peak at 15 to 30 minutes. These phenotypes seem to be linked to the maximal tolerated dose of hydroxyurea and could affect the response to HU.The aim of this study was to explore the possible correlation between clinical and biological response to HU and PK and PD parameters.This study was conducted at Hôpital Universitaire des Enfants Reine Fabiola (Brussels, Belgium) and included SCD children older than 7 years, regularly followed for more than 3 years. PK samples (salivary and plasmatic) were collected at 0, 30, 60 and 180 minutes after oral HU intake. Patients have been classified as good (GR) or poor responders (PR) to HU according to the absence of recurrence of acute chest syndrome on HU and the number of vaso-occlusive crisis (VOC) and hospitalization days on HU. Changes in biological parameters were assessed after 1 year on HU. Chi square test was used for the comparison between good and poor responders on HU. Paired T test was used to compare biological effect of HU for each oral absorption phenotype and ANOVA to compare PK profile among them.Thirty-one patients have been included in this study. The characteristics of the patients are detailed in the Table 1. On HU, a significant decrease of the number of VOC and hospitalization days was observed with an improvement of biological parameters (Table 2). The numbers of VOC and hospitalization days were significantly lower in girls compared to boys on HU (0.33 vs. 0, P=0.02 and 3.17 vs. 1.33, P = 0.02 respectively). However except for reticulocyte count, biological data, age, dose of HU or PK parameters were similar in both sexes.Eighteen patients have been classified as GR (14 girls) and 13 as PR (5 girls). Their demographic characteristics and biological values (pre and on HU) were not significantly different, except a higher change of HbF level in GR compared to PR (+13% vs. +3.7% ; P=0.034). Girls had a non-significant trend to belong to the GR group (P = 0.059).The median plasmatic peak concentration (Cpmax) was 42.25mg/l (Range: 14.8-62), the median salivary peak concentration (Csmax) was 19.54 mg/l (Range: 5.03-124.43) and the median AUC was 4650mg.min/l (Range: 1197-8742). AUC was similar in both sexes (4650mg.min/l vs. 4666mg.min/l; P=0.79). Except for salivary concentration at 60 minutes, all PK parameters were not significantly different between the GR and PR (Table 3). No significant correlation was found between peak concentration (Cmax) and demographic parameters.We identified 3 absorption phenotypes with a Cpmax reached at 30, 60 and 180 minutes for rapid, intermediate and slow absorbers (Table 4). Biological changes on HU were similar among the 3 phenotypes, but did not reached statistical signification in slow absorbers (only 5 patients). 16/18 GR patients reach Cpmax at 30 and 60 minutes compared to 10/13 for PR (P=0.63). The AUC in the 3 absorption phenotypes was not significantly different (P=0.069). No correlation was found between salivary and plasmatic concentration at time-points studied.In conclusion, no correlation between the absorption phenotype and the clinical response to HU could be found. No correlation was found between AUC, Cpmax and clinical response. Nevertheless our study has limitation due to the limited sample size. Salivary measurement did not provide reliable information and cannot be used instead of plasmatic samples. The gender is the only factor identified that can predict the biological response to HU (with a trend to a better clinical response in girls) despite similar AUC and PK parameters. This finding may reflect the better adherence to treatment in girls compared to boys.The variability of the clinical response to HU remains to be elucidated. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Interface of Sn-doped AgAlTe2 and LiInTe2: A theoretical model of tandem intermediate band absorber

Designing a new absorber to overcome the Shockley–Queisser limit for single-junction solar cells is of great importance for solar cell advancements. Here, a theoretical model of tandem intermediate band absorber is proposed based on the interface of Sn-doped AgAlTe2 and LiInTe2. Sn-doped AgAlTe2 and LiInTe2 are imminent to produce ideal heterojunctions as they possess similar lattice constants and the type-II band offset, providing an approach to overcome the Shockley–Queisser limit.

Reaction Mechanism of Phenolic Lignin and High Concentration Chlorine Dioxide and Its Application.

In fact, the chemical reaction rate of traditional chlorine dioxide bleaching of pulp is too fast to observe the intermediate process. The mechanism behind the reaction of 4-hydroxy-3-methoxyacetophenone (APO), a phenolic lignin model compound, with high concentrations of chlorine dioxide was investigated. Individual solutions of each compound and a mixture of the two were analyzed by UV–vis spectrophotometry, and an absorbance band at 260 nm was observed for the stable benzoquinone intermediates at room temperature. Free chlorine dioxide displayed an absorbance at 360 nm and changes in this absorbance were studied with different APO concentrations. A fixed molar ratio of 1:3 was obtained between APO and chlorine dioxide consumption. The intermediate absorbance demonstrated a linear relationship with the APO concentration. The reaction path between APO and chlorine dioxide at high concentrations was speculated, and it was observed that the activity of C1, C2, C3, C5, and C6 on the APO benzene ring was enhanced when high concentrations of chlorine dioxide were present. From these results, a new method for efficient and clean chlorine dioxide bleaching can be developed.

Gas-fired absorption heat pump applied for high-temperature water heating: Parametric study and economic analysis

Despite being efficient water heating technologies, conventional absorption heat pumps can hardly produce hot water with temperature over 90 °C, and compressor-based systems have low primary energy efficiency. In order to fill this temperature gap and improve the energy efficiency, a gas-fired ammonia-water absorption heat pump with intermediate process is proposed to supply hot water with large temperature lift for residential and industrial applications. In addition to the ambient heat utilized in the evaporator, the proposed system recovers the exhaust heat in the intermediate evaporator, and the evaporated ammonia vapor is absorbed in the intermediate absorber to further heat the water, which is initially preheated in sequence in the condenser, rectifier and absorber. Simulation results indicate that at the ambient temperature of 20 °C, the proposed system can produce hot water with temperature over 95 °C and the obtained temperature lift is 75 °C, while the primary energy efficiency is 1.38. Obtained results indicate that the intermediate pressure of 0.7 MPa is the optimum pressure from both thermodynamic and economic aspects. Moreover, it is found that the energy saving potential of the proposed system is in range of 36.7% to 43.5%, when the comparison is made with conventional gas-fired boilers, and the average payback period is 3.0 years in three typical cities of south China. It is concluded that the proposed system is an efficient scheme for high-temperature water heating with large temperature lift. This is especially pronounced in warm regions with average ambient temperature over 5 °C.

Spectral Studies of Lead‐Free Organic‐Inorganic Hybrid Solid‐State Perovskites CH3NH3Bi2/3I3 and CH3NH3Pb1/2Bi1/3I3: Potential Photo Absorbers

AbstractThe spectral analysis of bismuth based halide perovskite materials has been carried out using FTIR, UV‐Vis, photoluminescence and fluorescence time resolved spectroscopy. Methylammonium bismuth iodide (CH3NH3Bi2/3I3) has shown promising results to become a potential candidate for the replacement of lead based organic‐inorganic hybrid halide perovskite solar cells, having superior moisture stability and environmentally benign nature. The lead and bismuth both have been used to synthesize methylammonium lead bismuth iodide (CH3NH3Pb1/2Bi1/3I3) to develop an intermediate photo absorber to counter the moisture degradation properties as well as the low absorbance of bismuth based perovskites. Spectral studies have revealed information about electron transitions, phase separation and exciton recombination time.

Boosting the Performance of Solar Cells with Intermediate Band Absorbers—The Case of ZnTe:O

Boosting the Performance of Solar Cells with Intermediate Band Absorbers—The Case of ZnTe:O

Substitutionally-Doped Intermediate Band Absorbers of Readily Tunable Composition

Intermediate band photovoltaics (IBPV) attempt to significantly increase photovoltaic efficiency by absorbing more photons to produce additional photocurrent without sacrificing significant photovoltage. Through creation of a density of states within the parent semiconductor gap, a partially filled intermediate band (IB) may be used as a stepping stone to allow photons with sub-band gap energy to be absorbed and generate extractable charge carriers in a two-part absorption process. Sandwiching the IB material between selective n- and p-type contacts (or the parent semiconductor) excludes this Fermi level from the contacts, thereby theoretically preserving the full photovoltage of the parent material. This design theoretcially increases the maximum efficiency of a solar cell from 40.7 to 63.2% (assuming a large concentration factor). Substitution of V into In2S3 to form V0.25In1.75S3.00 is predicted to produce nearly ideal properties to maximize efficiency under concentrated sunlight, with a band gap of 2.1 eV, and an intermediate band 0.70 eV above the valence band. While powders of this material have been fabricated previously, we report the V x In(2–x)S3 thin films. Atomic layer deposition (ALD) is ideally suited to its fabrication as compositional doping/substitution can often be simply and reproducibly achieved with simple precursor pulse sequence control. This is in contrast to many physical deposition methods in which the source composition is fixed by the target allow for composition changes when the deposition rate of each element is nonequal. We utilize an oxygen-free process for growing In2S3 but periodically incorporate a novel vanadium precursor in place of the indium precursor to achieve continuous compositional control over V and In. The physical, optical, and electrical intermediate band properties as well as photoelectrochemical performance of the V x In(2–x)S3 films will be presented. The figure shows the absorption coefficients for VxIn(2–x)S3 films as a function of the doping level x. Figure 1

Physical Parameters of Phosphor Layers and their Effects on the Device Properties of Beta‐radioluminescent Nuclear Batteries

AbstractA series of phosphor layers (ZnS:Cu‐Large, ZnS:Cu‐Small, and Y2O2S:Eu) precipitated with varying mass thicknesses were prepared using a homogeneous precipitation method. Radioluminescence (RL), the light emitted from phosphor materials immediately upon beta particle radiation, was measured at room temperature using RL spectra under 4.89 mCi cm−2 63 Ni and 2.23 mCi cm−2 147 Pm beta particle sources, respectively. The RL properties, such as emission intensity, are affected by the mass thickness of the phosphor layers. In this work, the performance of beta‐radioluminescent nuclear batteries with the aforementioned phosphor layers as intermediate absorbers was analyzed and discussed. The current–voltage characteristics of the nuclear batteries revealed the effect of the physical parameters of the phosphor layers. The maximum output power of the batteries increased approximately linearly with increasing RL intensity for the three types of phosphors under excitation by different beta sources.

A drop-tube particle-entrained flow solar reactor applied to thermal methane splitting for hydrogen production

A solar chemical reactor with continuous particle feeding in a tubular absorber has been designed and tested for CO2-free hydrogen production from thermal methane decomposition. The entrained-flow reactor was operated on sun with carbon black particle injection in a stream of methane diluted in argon. The carbon particles are expected to act as a catalyst for the dissociation reaction and the indirect irradiation via an intermediate opaque tubular absorber results in a more uniform heating of the reactor volume and thus an easier reaction temperature control and determination. The effect of particle injection on the reactor performance was investigated as a function of the type of carbon black catalyst and characteristics, reaction temperature (1150–1400°C), total volumetric gas flow rate and methane content in the feed gas (10–40%). Key measured performance outputs were CH4 conversion and H2 yield, C2H2 outlet concentration, and solar-to-chemical reactor efficiency. The particle feeding did not drastically improve the methane decomposition rate and hydrogen yield, which can presumably be attributed to kinetic limitation due to short particle residence time in the high-temperature region. Likewise, the inlet methane mole fraction was not a primary influencing parameter. In contrast, the temperature and the gas flow rate strongly affected the methane decomposition rate.

Welding of PMMA by a femtosecond fiber laser.

Developing versatile joining techniques to weld transparent materials on a micrometer scale is of great importance in a growing number of applications, especially for the fabrication and assembly of biomedical devices. In this paper, we report on fs-laser microwelding of two transparent layers of polymethyl methacrylate (PMMA) based on nonlinear absorption and localized heat accumulation at high repetition rates. A fiber CPA laser system was used delivering 650-fs pulses at 1030 nm with repetition rates in the MHz regime. The laser-induced modifications produced by the focused beam into the bulk PMMA were firstly investigated, trying to find a suitable set of process parameters generating continuous and localized melting. Results have been evaluated based on existing heat accumulation models. Then, we have successfully laser welded two 1-mm-thick PMMA layers in a lap-joint configuration. Sealing of the sample was demonstrated through static and dynamic leakage tests. This fs-laser micro-welding process does not need any pre-processing of the samples or any intermediate absorbing layer. Furthermore, it offers several advantages compared to other joining techniques, because it prevents contamination and thermal distortion of the samples, thus being extremely interesting for application in direct laser fabrication of microfluidic devices.

Hydrogen production from thermo-catalytic decomposition of methane using carbon black catalysts in an indirectly-irradiated tubular packed-bed solar reactor

The solar thermo-catalytic decomposition of methane using carbon black catalysts for CO2-free hydrogen production is studied in a packed-bed reactor. The indirectly-irradiated reactor is based on a cavity receiver and a tube-type absorber in which a given load of particle catalyst is injected during on-sun operation, while enabling multiple refilling for catalyst replacement. Concentrated solar power is used as an external radiative source for supplying the high temperature process heat and for driving the endothermic reaction. The indirect irradiation via the intermediate opaque tubular absorber results in a more uniform heating of the whole reacting bed volume and thus an easier reaction temperature control and determination. Carbon particles are used for enhancing the rate of the heterogeneous decomposition reaction and the coupling of the reactor with a particle injection system is implemented to operate in semi-continuous mode with possibility of catalyst load renewal after deactivation.The packed-bed reactor was operated on-sun to investigate the effect of the various operating parameters on the reactor thermochemical performances. Complete methane conversion to hydrogen was achieved (100% selectivity to H2 with no side-products), but catalyst deactivation occurred progressively because of carbon deposition at the surface, with acetylene as the main evolving by-product. The temperature and the residence time of the flowing gas through the catalyst bed were identified as the main parameters influencing the chemical conversion and hydrogen yield. This type of scalable reactor configuration could be applied for continuous hydrogen production with in-situ catalyst regeneration or substitution without reactor operation break-down at high temperatures.

Photophysics of Fe(III)–tartrate and Fe(III)–citrate complexes in aqueous solutions

Femtosecond pump–probe spectroscopy was used to determine the photophysical processes of Fe(III) complexes with citric and tartaric acids ([Fe(Cit)] and [Fe(tart)]+) in aqueous solutions. The excitation of the complexes in the charge transfer bands is followed by formation of an intermediate absorbance decaying with two characteristic times. The shorter time constant (0.2, 0.4ps) is ascribed to vibrational cooling and solvent relaxation of Frank–Condon excited state of corresponding complex and the second time constant (1.4, 40ps) is assigned to superposition of internal conversion to the ground state and formation of the long-lived Fe(II) radical complex. The competition of these processes determines the quantum yield of photolysis of Fe(III)–carboxylates.

A computational method to help identify and measure metal lines in high resolution QSO spectra

A computational code is developed to help identify metal absorption lines in high resolution QSO spectra, especially in the Lyα forest. The input to the code includes a list of line central wavelengths, column densities and Doppler widths. The code then searches for candidate metal absorption systems and assesses the probability that each system could be real. The framework of the strategy we employ is described in detail and we discuss how to estimate the errors in line profile fitting that are essential to identification. A series of artificial spectra is constructed to calibrate the performance of the code. Due to the effects of blending and noise on Voigt profile fitting, the completeness of the identification depends on the column density of absorbers. For intermediate and strong artificial metal absorbers, more than 90% could be confirmed by the code. The results of applying the code to the real spectra of QSOs HS0757+5218 and Q0100+1300 are also presented.

The spectral properties and thermal stability of NbTiON solar selective absorbing coating

A new solar selective absorbing coating of NbTiON/SiON was prepared on Cu substrate using a reactive magnetron sputtering method. The new coating exhibits a high absorptance ( α) of 0.95 and a low emittance ( ε) of 0.07, and the thickness of NbTiON and SiON layers was optimized to achieve high solar selectivity. The spectral properties ( α/ ε) of the coating on Cu substrate are stable (0.94/0.08) even after heat-treatment at 500 °C in vacuum for 40 h, but decreased at 600 °C. If the substrate is replaced by stainless steel (SS), the coating exhibits better stability, which indicates its potential applications in intermediate temperate solar absorber.

Cholesterol-Absorber Status Modifies the LDL CholesterolLowering Effect of a Mediterranean-Type Diet in Adults with Moderate Cardiovascular Risk Factors

AbstractLDL-cholesterol (LDL-C) reduction may be achieved by various types of prudent diets, but their effects on surrogate markers of cholesterol absorption and synthesis have not been well studied in humans. We aimed to assess whether the extent of cholesterol absorption or synthesis, and cholesterol concentrations, are modified in adults when they shift from a Western-type diet (WD) to a combined low-fat, low-cholesterol/Mediterranean-type diet (LFCMD). Cholestanol and sitosterol, as well as desmosterol and lathosterol, surrogate markers of cholesterol absorption or synthesis, respectively, were quantified in the serum of 125 fasting, middle-aged participants at moderate cardiovascular risk. They habitually consumed a WD and then consumed a LFCMD during the 3-mo intervention. The group was stratified by serum cholestanol concentration and classified as high, intermediate, or low absorbers of cholesterol. When they consumed the WD, participants had comparable total and LDL-C concentrations, independent of absorber group and sex. After 3 mo of consuming the LFCMD, absorption and synthesis did not change or changed only slightly. The cholestanol concentration increased in low absorbers by 18% (P< 0.02) and decreased in high absorbers by 14% (P< 0.001), but these variations did not change the high- or low-absorber status. In male and female low absorbers, plasma total (–7%) and LDL-C (–9%) concentrations decreased after the 3-mo intervention and changes were 2.3- and 2.4-fold greater, respectively, than in high absorbers, independent of sex. Cholesterol synthesis/absorption status was not markedly altered by diet, but the decrease in plasma LDL-C due to the Mediterranean-type diet occurred only in low absorbers of cholesterol. This should be considered during further dietary interventions.

Influence of the absorber doping for p-type polycrystalline silicon thin-film solar cells on glass prepared by electron beam evaporation and solid-phase crystallization

A systematic investigation of the influence of the absorber doping on the performance of planar, p-type, evaporated, solid-phase crystallized polycrystalline silicon thin-film solar cells on glass is presented. It is found that the optimum Suns-Voc parameters (open-circuit voltage and pseudo fill factor) are achieved at intermediate absorber doping of Nabs∼1–2 × 1017 cm−3, while high short-circuit currents are achieved at the lowest absorber doping of Nabs ≤ 6 × 1015 cm−3. Since the short-circuit current is the dominating factor to achieve high conversion efficiencies for evaporated polycrystalline silicon cells, the maximum pseudo efficiencies are achieved at very low absorber doping. The Suns-Voc characteristics of lightly doped cells can be adequately described by a modified two-diode model with n1=1 and n2≈1.5, which is in contrast to the value of 2 for n2 commonly quoted in the literature. PC1D modeling demonstrates that such a low ideality factor for space charge region recombination can be modeled by a single trap energy level located at ∼0.18 eV away from midgap. Although the achievable short-circuit current densities and the conversion efficiencies can be higher for textured cells, planar cells are chosen intentionally to allow accurate modeling and extraction of relevant material parameters, such as minority carrier diffusion length.

A comparative study of naturally ventilated and gas filled windows for hot climates

The use of absorbing gases filling the gap between glass sheets appears to be an alternative solution for thermally insulated glass windows. Fluid flow in the gap between the glass sheets either forced or natural offers other options for thermally efficient windows. In this work, the thermal efficiencies of glass windows filled with an absorbing gas exposed to solar radiation in hot climate is compared with both a simple glass window and a double glass window naturally ventilated. The two-dimensional transient energy equations with radiation absorption in the internal domain are used to model the simple glass window. The cumulative wavenumber model (CW) for real gas modeling together the discrete ordinates method is used to model double glass window filled with infrared absorbing gases. The numerical simulations were realized with three mixtures of gases, a strongly absorbing gas mixture, an intermediate absorbing gas mixture and a transparent to infrared radiation mixture. To model a double glass window naturally ventilated, a two-dimensional transient laminar incompressible flow formulation is used and the buoyancy effects are accounting for by the Bussinesq approximation. Heat transfer through the windows is calculated and the total heat gain coefficient is compared for the three types of windows.

Iodine binding property of a ternary complex consisting of starch, protein, and free fatty acids

A ternary complex consisting of amylose, whey protein, and free fatty acids (FFA) has been identified in our previous investigations, and its iodine binding properties were investigated. After reaction with iodine solution, an absorption peak ( λ max) at 620 nm was shown for pure amylose whereas the λ max decreased to 510 nm when amylose was first complexed with FFA. Interestingly, a λ max of 550 nm with an intermediate absorbance was observed for the ternary complex indicating its intermediate spectrophotometric property. Consistently, the amount of iodine bound by the ternary complex was between free amylose and typical amylose–FFA complex from potentiometric titration indicating the amylose–FFA complex within the ternary complex is less compact and more space is left for iodine binding. This in-between property of the ternary complex suggests it can be used as a molecular carrier to accommodate a forth component in addition to its functional lipids carrying capability in food product development.