Antireflection coatings for solar photoelectric elements based on SiO<Subscript>2</Subscript> and TiO<Subscript>2</Subscript> mixed oxides

Computer modeling of one-layer antireflection coating based on SiO₂ and TiO₂ mixed oxides was carried out for solar elements. It was concluded that a photoelectric current can be increased by varying the thickness of the covering within the limits of 55–90 nm, while the concentration of SiO₂ in TiO₂ shall not exceed 30%. A method of magnetron spattering was offered as a method for application of the coating based on a SiO₂-TiO₂ mixture.     

Study on Al<Subscript>2</Subscript>O<Subscript>3</Subscript> extraction from activated coal gangue under different calcination atmospheres

Coal gangue was calcinated under air, nitrogen, carbon dioxide, air–hydrogen, and hydrogen atmospheres. The effects of different calcination temperatures and atmospheres on the mineral composition of activated coal gangue were investigated by X-ray diffraction. Moreover, the acid leaching kinetics of aluminum oxide from coal gangue was investigated with sulfuric acid. It showed that the air atmosphere promoted kaolinite decomposition during coal gangue calcination. The hydrogen atmosphere promoted the activation and decomposition of kaolinite at reaction temperatures exceeding 650°C. The carbon dioxide atmosphere eliminated the influence of residual carbon on coal gangue. When the ratio of acid/coal gangue was 1.5 and reaction temperature was 650°C, the sulfuric acid leaching rate under air, air-hydrogen, carbon dioxide, hydrogen and nitrogen atmospheres were 93.66%, 90.90%, 84.06%, 81.91% and 77.54% respectively. The acid leaching reaction process conformed to unreacted shrinking core model of particle unchanged, and was controlled by the interfacial chemical reaction. The reaction kinetic equation for the leaching process was 1-(1-x)1/3=kt with an apparent activation energy of 48.97 kJ/mol.     

Antireflection coatings for solar elements based on a composition of Ge and GeO2

The optical properties of a single layer antireflection coating for solar elements based on a composition of Ge and GeO₂ are studied. The results of computer modeling and optical measurements led to the conclusion that a single layer coating based on a composition of Ge and GeO₂ is an efficient antireflection coating and has technological advantages as compared with the traditionally used coatings.     

Ceramic microfilters based on the solar-furnace-synthesized CaZr<Subscript>4</Subscript>(PO<Subscript>4</Subscript>)<Subscript>6</Subscript>

Ceramic microfilter samples (d _max = 18.3 μm) were prepared based on mixed calcium orthophosphate with an NZP structure melted in a solar furnace; the microfilters have a productivity one order of magnitude higher that that of chamotte-bentonite filters with the same size of the largest pores.     

Possibilities of increasing the efficiency of Si and CuInSe<Subscript>2</Subscript> solar cells

The paper proposes a method of increasing the efficiency of Si and CuInSe₂ solar cells using the impact ionization and impurity photovoltaic effect in pZnTe-pSi-nSi and pZnTe-pCuInSe₂-n(CuInSe₂)_1−x (2InAs) _x structures.     

Research on Thermophysical Properties of Nanoliquids Based on SiO<Subscript>2</Subscript> Nanoparticles for Use as a Heat-Transfer Medium in Solar-Thermal Converters

This paper presents an analysis of the modern state of studies of the thermophysical properties of nanofluids and the heat-transfer mechanism in them. The results of experimental studies of obtaining and determining the dynamic viscosity of the nanofluids (SiO₂ + water) with various concentrations of nanoparticles are given. Nanofluids are obtained using a two-stage method in an ultrasonic field with a frequency of 20 kHz. It is shown that, in the SiO₂ + water system, nanoparticles with sizes of 7, 12, and 16 nm are most stable. Various SiO₂ concentrations in the volume range 0.5–5% were tested, and their thermophysical properties were studied for the purpose of using them as a heat-transfer medium in flat-plate solar collectors.     

Component exergy analysis of solar powered transcritical CO<Subscript>2</Subscript> rankine cycle system

In this paper,exergy analysis method is developed to assess a Rankine cycle system,by using supercritical CO2 as working fluid and powered by solar energy.The proposed system consists of evacuated solar collectors,throttling valve,high-temperature heat exchanger,low-temperature heat exchanger,and feed pump.The system is designed for utilize evacuated solar collectors to convert solar energy into mechanical energy and hence electricity.In order to investigate and estimate exergy performance of this system,the energy,entropy,exergy balances are developed for the components.The exergy destructions and exergy efficiency values of the system components are also determined.The results indicate that solar collector and high temperature heat exchanger which have low exergy efficiencies contribute the largest share to system irreversibility and should be the optimization design focus to improve system exergy effectiveness.Further,exergy analysis is a useful tool in this regard as it permits the performance of each process to be assessed and losses to be quantified.Exergy analysis results can be used in design,optimization,and improvement efforts.     

The influence of concentrated solar radiation on the properties of Ga<Subscript>0.7</Subscript>In<Subscript>0.3</Subscript>P/GaP photoconverters

The properties of Ga_0.7In_0.3P/GaP heterophotoconverters with a two-sided contact grid are studied in the range of solar radiation concentration K _s = 1−100 times and with natural convective heat exchange. It is found that, in the considered photoconverters, the dependences of an idle running voltage, the duty cycle of the current-voltage characteristic, and the efficiency on concentration are additionally improved due to high heat conduction of GaP and the temperature stability of the broad-band heterophotoconverter with “transparent“ structural design.     

Synthesis of pyroxene pyroceramics in large solar furnace with ZrO<Subscript>2</Subscript> crystallization nucleator

Research on the development of zirconium-containing pyroxene glass-ceramic materials with high mechanical and chemical stability has been performed.     

Antireflection coatings for solar cells based on an alloy of a mixture of MgO and SiO2

Alloys of a mixture of MgO and SiO₂ oxides are obtained using radiant heating. X-ray phase analysis shows that the mixture alloys are multiphase crystalline structures and solid solutions; they contain a glass phase and traces of the original oxides. For the mole: mole concentration, forsterite is identified in the composition of the composite material. It is found that films of an alloy of MgO and SiO₂ deposited on the surface of glass and silicon wafers exhibit high mechanical strength and adhesion; they are transparent in the range of sensitivity of solar cells and can be used as antireflection coatings.     

The Formation of Nano—Size SiO2 Thin Film on an Aluminum Plate with Hexamethyldisilazane（HMDSA）and Hexamethyldisiloxane（HMDSO）

This study is using HMDSA(C6H19NSi2)or HMDSO(C6H18OSi2) vapor into C3H8/air premixed flames to form SiO2 thin film on the surface of an aluminum palte.With the addition of HMDSO or HMDS to premixed flames,an orange secondary flame or a flame brush appeared and was contributed to the formation of SiO2 particles.Based upon the EDS,XPS and FTIR analysis ,it is believed that the synthesized products consist of mainly SiO2 and a small amount of SiO,The pure SiO2 crystal structure,was proved by XRD analysis,which may form form the SiO2 amorphous structure after high temperature(1300℃) thermal treatment.The nano-size SIO2 particles,which ranged form 2.5-25nm,are proved by analysis of the BET and TEM.A 2-D CFD-RC code with 12 reduced chemical reaction mechanism.based upon the SIMPLER procedure,was successfully employed to predict the flame temperature and both of the SiO2 and SiO concentration profiles.Compared with the experimental results,the calculated temperature profiles in the post-flame region are in good agreement with the measured data and observation phenomena.     

Investigation on the energy conversion of dye-sensitized solar cells based on TiO<Subscript>2</Subscript> core/shell using metal oxide as a barrier layer

Photo-electrochemical solar cells based on a core-shell structure including ZnO shell and TiO₂ cove, have been fabricated with ruthenium bipyridyl complex (N719) as the sensitizer. Compared with the pure anatase TiO₂, the ZnO-covered TiO₂ film possesses outstanding ability to transport electrons with an overall power conversion efficiency of 3.72. Elctrochemical study shows that surface modification of TiO₂ film with ZnO can increase the concentration of free electrons in the conduction band of TiO₂. This remit implies that the charge recombination is reduced in process of electron transport through the TiO₂ porous film, which can decrease the photocurrent loss and hence improve Dye-Sensitized solar ceils (DSSCs) efficiency. This result indicates that optimization of TiO₂ porous network fabrication condition is efficient, for the improvement of TiO₂ based DSSC’s performances.     

Morphology and Photoelectric Characteristics of the Thin-Film Polycrystalline Structure SnO<Subscript>2</Subscript>-CdS/Cu(InGa)Se<Subscript>2</Subscript>-Ag

The surface morphology and photoelectric characteristics of a thin-film SnO₂-CdS/Cu(InGa)Se₂-Ag heterostructure have been studied. The chemical and phase composition of the Cu(InGa)Se₂ film in the synthesized structure have been investigated. The current transfer mechanism has been studied, and the main parameters of the semiconductor material have been determined. It has been found that there are no oppositely connected barriers in the heterostructure.     

CO<Subscript>2</Subscript> mitigation in coal gasification cogeneration systems with integration of the shift reaction,CO<Subscript>2</Subscript> absorption and methanol production

Cogeneration of electricity and liquid fuel can achieve higher efficiencies than electricity generation alone in Integrated Gasification Combined Cycle (IGCC), and cogeneration systems are also expected to mitigate CO₂ emissions. A proposed methanol-electricity cogeneration system was analyzed in this paper using exergy method to evaluate the specified system. A simple cogeneration scheme and a complicated scheme including the shift reaction and CO₂ removal were compared. The results show that the complicated scheme consumes more energy, but has a higher methanol synthesis ratio with partial capture of CO₂. In those methanol and electricity cogeneration systems, the CO₂ mitigation is not merely an additional process that consumes energy and reduces the overall efficiency, but is integrated into the methanol production.     

Thermovoltaic effect of <Emphasis Type="Italic">p</Emphasis>Si-<Emphasis Type="Italic">n</Emphasis>(Si<Subscript>2</Subscript>)<Subscript>1−x</Subscript>(ZnS)<Subscript>x</Subscript> structures

The pSi-n(Si₂)_1−x (ZnS) _x (0 ≤ x ≤ 0.92) structure, on which thermovoltaic effect is observed, has been obtained by means of liquid-phase epitaxy from tin solution-melt on plates of p-type technical silicon. This effect is explained by grain boundary defects and influence of ZnS impurities in a thin layer adjacent to the p-n-junction.     

Production and Characteristics of (ZnSe)<Subscript>0.1</Subscript>(SnSe)<Subscript>0.9</Subscript> Films for Use in Thin Film Solar Cells

(ZnSe)_x(SnSe)_1–x films have been produced using chemical molecular beam deposition (CMBD) from an ZnSe and SnSe compound with a stoichiometric composition at a substrate temperature of 500°С. The structural, morphological, and electrophysical properties of (ZnSe)_0.1 (SnSe)_0.9 films are studied. The size of film grains is 5–6 μm. The results of X-ray diffraction analysis of specimens have revealed that the films have a crystalline (orthorhombic) structure. The structural parameters of the produced films are presented. The electrical conductivity of the films measured using the Van der Pauw method varies within 15–0.6 Ω cm^–1.     

Circulating fluidized bed gasification of low rank coal: Influence of O<Subscript>2</Subscript>/C molar ratio on gasification performance and sulphur transformation

To promote the utilization efficiency of coal resources, and to assist with the control of sulphur during gasification and/or downstream processes, it is essential to gain basic knowledge of sulphur transformation associated with gasification performance. In this research we investigated the influence of O₂/C molar ratio both on gasification performance and sulphur transformation of a low rank coal, and the sulphur transformation mechanism was also discussed. Experiments were performed in a circulating fluidized bed gasifier with O₂/C molar ratio ranging from 0.39 to 0.78 mol/mol. The results showed that increasing the O₂/C molar ratio from 0.39 to 0.78 mol/mol can increase carbon conversion from 57.65% to 91.92%, and increase sulphur release ratio from 29.66% to 63.11%. The increase of O₂/C molar ratio favors the formation of H₂S, and also favors the retained sulphur transforming to more stable forms. Due to the reducing conditions of coal gasification, H₂S is the main form of the released sulphur, which could be formed by decomposition of pyrite and by secondary reactions. Bottom char shows lower sulphur content than fly ash, and mainly exist as sulphates. X-ray photoelectron spectroscopy (XPS) measurements also show that the intensity of pyrite declines and the intensity of sulphates increases for fly ash and bottom char, and the change is more obvious for bottom char. During CFB gasification process, bigger char particles circulate in the system and have longer residence time for further reaction, which favors the release of sulphur species and can enhance the retained sulphur transforming to more stable forms.     

Effects on global CO<Subscript>2</Subscript> emissions when substituting LPG with bio-SNG as fuel in steel industry reheating furnaces—the impact of different perspectives on CO<Subscript>2</Subscript> assessment

The iron and steel industry is the second largest user of energy in the world industrial sector and is currently highly dependent on fossil fuels and electricity. Substituting fossil fuels with renewable energy in the iron and steel industry would make an important contribution to the efforts to reduce emissions of CO₂. However, different approaches to assessing CO₂ emissions from biomass and electricity use generate different results when evaluating how fuel substitution would affect global CO₂ emissions. This study analyses the effects on global CO₂ emissions when substituting liquefied petroleum gas with synthetic natural gas, produced through gasification of wood fuel, as a fuel in reheating furnaces at a scrap-based steel plant. The study shows that the choice of system perspective has a large impact on the results. When wood fuel is considered available for all potential users, a fuel switch would result in reduced global CO₂ emissions. However, applying a perspective where wood fuel is seen as a limited resource and alternative use of wood fuel is considered, a fuel switch could in some cases result in increased global CO₂ emissions. As an example, in one of the scenarios studied, a fuel switch would reduce global CO₂ emissions by 52 ktonnes/year if wood fuel is considered available for all potential users, while seeing wood fuel as a limited resource implies, in the same scenario, increased CO₂ emissions by 70 ktonnes/year. The choice of method for assessing electricity use also affects the results.     

Possibility of doping and using ZnSe,CdS, and GaP layers as down converters of Si and CuInSe<Subscript>2</Subscript> solar cells

The possibility and reasonability of developing down converters of Si and CuInSe₂ solar cells based on Ge₂P- and GaSb-doped GaP, ZnTe, and CdS is discussed. The case is considered when a down converter is a part of a solar cell’s p–n heterojunction, and the preparation conditions for the GaP(Ge₂GaSb) layer of the Si substrate are specified.     

Estimating the industrial waste heat recovery potential based on CO<Subscript>2</Subscript> emissions in the European non-metallic mineral industry

Industrial waste heat (IWH) is a key strategy to improve energy efficiency and reduce CO₂ emissions in the industry. But its potential for different countries remains unclear due to a non-existent or inconsistent data basis. The objective of this paper is to assess the IWH potential of the European non-metallic mineral industry, using databases which comprise CO₂ emissions of more than 400 industrial sites as well as country- and sector-specific parameters. This sector is selected because of its homogenous nature, meaning that most sites carry out similar or the same processes, which facilitates site-level modelling with subsector-level assumptions. The bottom-up approach is employed to derive the IWH potential for this industry over the period 2007–2012. Average results in this period show an IWH potential per site of 0.33 PJ/a and a potential for the whole sector of 134 PJ/a. The countries with the largest IWH potentials are Germany, Italy, France and Spain with yearly average potentials of 23, 19, 17 and 16 PJ, respectively. The subsector with the most IWH potential is cement. Further work should focus on the improvement of methodologies to assess the IWH potential, in particular through a techno-economic assessment of links between IWH sources and potential sinks.