Use In Solar Energy Applications Research Articles

Insights into the pressure-dependent physical properties of cubic Ca3MF3 (M = As and Sb): First-principles calculations

Here, first-principles calculations have been employed to make a comparative study on structural, mechanical, electronic, and optical properties of new Ca3MF3 (M = As and Sb) photovoltaic compounds under pressure. The findings disclose that these two systems possess a direct band gap, showcasing a large tunable range under pressure, effectively encompassing the visible light spectrum. Adjusting various levels of hydrostatic pressure has effectively tuned both the band alignment and the effective masses of electrons and holes. Both compounds were initially identified as brittle materials at 0 GPa pressure; however, as the pressure increases, they transform, becoming highly anisotropic and ductile. Due to the material's mechanical robustness and enhanced ductility, as evidenced by its stress-induced mechanical properties, the Ca3MF3 (M = As and Sb) material shows potential for use in solar energy applications. Furthermore, as the influence of external pressure increases, the absorption edge seems to move slightly towards lower energy region. Optical properties show that the materials studied might be used from several optoelectronic devices in the visible and ultraviolet range area. Our findings show that pressure considerably influences the physicochemical properties of Ca3MF3 (M = As and Sb) compounds, which is a promising feature that can be useful for optoelectronic and photonic applications, for instance, light-emitting diodes, photodetectors, and solar cells.

Effect of Heat and Laser Treatment on Cu2S Thin Film Sprayed on Polyimide Substrate

Three samples of copper sulfide Cu2S thin film were deposited on polyimide substrate by spray pyrolysis using deposition temperature of 400°C and deposition time of about 45 min. One of the samples was left as deposited, another was heat treated, while the third was laser treated. The structural, surface morphological, optical, mechanical, and electrical properties of the films were investigated. X-ray diffraction (XRD) analysis showed that the copper sulfide films were close to copper-rich phase (Cu2S). Increased crystallite size after heat and laser treatment was confirmed by XRD analysis and scanning electron microscopy. Vickers hardness measurements showed that the samples’ hardness values were enhanced with increasing crystallite size, representing an inverse Hall–Petch (H–P) effect. The calculated optical bandgap of the treated films was lower than that of the deposited film. Finally, it was found that both heat and laser treatment enhanced the physical properties of the sprayed Cu2S films on polyimide substrate for use in solar energy applications.

ChemInform Abstract: Copper(I)‐Based p‐Type Oxides for Photoelectrochemical and Photovoltaic Solar Energy Conversion

AbstractReview: 136 refs.

Copper(I)-Based p-Type Oxides for Photoelectrochemical and Photovoltaic Solar Energy Conversion

Recent research efforts have been growing into p-type copper(I) based oxides for development of their use in solar energy applications. The oxides of interest include the binary Cu2O and a number of new ternary CuxMyOz oxides. Both the binary and ternary Cu(I)-based oxides have many advantages when compared to other well-known p-type oxides such as NiO, III–V, and II–VI semiconductors. The benefits found within the diverse group of Cu(I)-containing oxides include bandgap sizes that can be tuned from ∼1.2 to >3.0 eV, high charge carrier mobility, and favorable band energies relative to fuel-producing redox couples. These properties give them potential utility in a variety of different solar applications, such as in dye-sensitized solar cells and suspended powder photocatalysis. Research efforts into surface modifications and changes in their chemical compositions and structures have allowed for greater stability and greater efficiency in aqueous solutions, both of which have represented two key barriers fo...

Optical properties of Cu2S nano-hollow cactus arrays with different morphologies

In this study, a series of Cu2S nano-hollow cactus arrays (CNHC) with varying morphologies is prepared by a two-step process including electrodeposition and the solid–gas reaction method. The structure of the arrays is characterized by scanning electron microscopy, X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy; while, their light absorption performance is investigated by diffuse reflectance and photoluminescence spectroscopy. The “thorns” of the CNHC are single-crystal Cu2S semiconductors, and the band gap of the CNHC can be adjusted by changing their morphology, where the light absorption ability of the array is enhanced from 82% to 93% as the thorn diameter decreases from 1500 to 163nm. All of the different CNHC morphologies exhibit little sensitivity to the incident angle of the light. For example, the light absorption of the CNHC with a thorn diameter of 430nm only decreases by 5% as the incident angle increases from 0° to 45°. This shows the potential of the CNHC for use in solar energy applications, where its insensitivity to the angle of the incident light will reduce the necessity of adjusting the angle of solar cell panels using CNHC in the photovoltaics.

Perovskites and their potential use in solar energy applications.

1. Introduction A material may be described as having a perovskite structure1 if it has same type of crystal structure as perovskite--calcium titanium oxide (CaTi[O.sub.3])--does (Figure 1). Perovskite was first discovered in 1839 by Gustav Rose, in the Ural mountains in Russia, and is named after the Russian mineralogist L. A. Perovski (1792-1856), who first characterised the material. The general formula for perovskites is [ABX.sub.3], with 'A' and 'B' being two cations of significantly different sizes ('A'>'B'), while X is an that binds with both cations. The perovskite structure is adopted by many oxides that have an elemental composition: AB[O.sub.3]. The ideal cubic-structure has the 'B' cation in a 6-fold coordination, surrounded by an octahedron of anions, with the 'A' cation in a 12-fold cuboctahedral coordination. Cations 'A' occupy the cube corner positions (0, 0, 0), while cations 'B' occupy the body centred positions (1/2, 1/2, 1/2) with oxygen anions 'O' being located at face centred positions (1/2, 1/2, 0). Figure 1 shows edges for an equivalent unit cell with 'A' in body centre, 'B' at the comers, and 'O' in mid-edge. The requirements of relative ionic radii are quite exacting to maintain a stable cubic structure, meaning that even relatively minor degrees of buckling and distortion can result in a number of alternative versions with lower symmetry, in which the coordination numbers of either the 'A' cations, 'B' cations, or both, are reduced. Tilting of the B06 octahedron reduces the coordination of a too-small 'A' cation from 12 down to as low as 8. Conversely, when a small 'B' cation is brought off-centre, within its octahedral coordination, a stable bonding arrangement can be obtained. Such distortions can create an electric dipole and it is for this reason that perovskites such as BaTi03, which distort in this manner, exhibit the property of ferroelectricity. The most usual non-cubic forms of perovskites are the orthorhombic and tetragonal variants. There are also some more complex perovskite structures which contain two different 'B'-site cations, with the result that ordered and disordered variants are possible. [FIGURE 1 OMITTED] Under the high pressure conditions of the Earth's lower mantle, the pyroxene enstatite, MgSi[O.sub.3], is converted to a more dense perovskite-type polymorph, and indeed it is speculated that this particular phase of the material might be the most common mineral in the Earth (2). It has a perovskite structure, with an orthorhombic distortion, and is stable at pressures from ~24 GPa to ~110 GPa. [For comparison, the pressure at the centre of the Earth is ca 300 GPa.] However, it is stable only at depths of several hundred kilometres and could not be transported back to the Earth's surface without reforming into less dense materials. At yet greater pressures, MgSi[O.sub.3] perovskite undergoes a transformation to form post-perovskite. Although the most common perovskite compounds contain oxygen, perovskites containing fluoride anions are known, e.g. NaMg[F.sub.3]. Metallic perovskite compounds also exist (1), with the general formula [RT.sub.3]M, where R represents a rare-earth or other relatively large cation, T is a transition metal ion and M represents light metalloids (anions) which occupy the octahedrally coordinated 'B' sites, e.g. [RPd.sub.3]B, [RRh.sub.3]B and Ce[Ru.sub.3]C. MgC[Ni.sub.3] is a metallic perovskite compound, and is of particular interest on account of its superconducting properties. A further category has mixed oxide-aurides of Cs and Rb, such as [Cs.sub.3]AuO, which contain large alkali metal cations in the traditional anion sites, bonded to [O.sup.2-] and [Au.sup.-] anions. 2. Properties of perovskites As noted, the perovskite structure is imparted with an appreciable element of structural pliancy, and the ideal cubic structure (Figure 1) can be distorted in many different ways. Thus, the octahedra may become tilted, the cations can be displaced from the centres of their coordination polyhedra, and the octahedra might be distorted at the behest of electronic factors (e. …

Electrodeposited Cobalt-Sulfide Catalyst for Electrochemical and Photoelectrochemical Hydrogen Generation from Water

A cobalt-sulfide (Co-S) film prepared via electrochemical deposition on conductive substrates is shown to behave as an efficient and robust catalyst for electrochemical and photoelectrochemical hydrogen generation from neutral pH water. Electrochemical experiments demonstrate that the film exhibits a low catalytic onset overpotential (η) of 43 mV, a Tafel slope of 93 mV/dec, and near 100% Faradaic efficiency in pH 7 phosphate buffer. Catalytic current densities can approach 50 mA/cm(2) and activity is maintained for at least 40 h. The catalyst can also be electrochemically coated on silicon, rendering a water-compatible photoelectrochemical system for hydrogen production under simulated 1 sun illumination. The facile preparation of this Co-S film, along with its low overpotential, high activity, and long-term aqueous stability, offer promising features for potential use in solar energy applications.

Study of the Intensity of Global Solar Radiation Incident in Suan Sunandha Rajabhat University

Solar radiation is one of mains alternative energy, widely used in present day. Measure solar radiation accurately is an essential for planning in application of used. Universities are the places that have used significant of energy all year long. Therefore, long-term measured solar radiation data is important, for understand in both quantity and variation in time period, for application of the alternative energy in future. The main objective of this research is to investigate solar energy potentials of Suan Sunandha Rajabhat University, Bongkok, Thailand (Latitude 13.46°N, Longitude 100.31°E). A station for solar radiation was installed at Suan Sunandha Rajabhat University. The main equipment is composed of two parts: 1) a pyranometer from Kipp & Zonen Ltd., model CMP11, and 2) a digital data logger from Measurement Systems Ltd. model DX2000. The pyranometer is permanently installed on the top of a building. The data logger is keeping clean and safe inside the building. To analyze the values of the global solar radiations, the computer source code is written in Interactive Data Language version 6.1 (IDL6.1). The results show the variation of the average hourly global irradiance is about 800-900 W/m2 at 12:00 UTC. The maximum monthly average daily global radiation is 21.5 MJ/m2-day in April. The yearly average daily radiation at Suan Sunandha Rajabhat University is found to be 16.55 MJ/m2-day. The information from the monthly and yearly global radiation has relatively high solar energy potentials. Finally, the solar radiation database was also developed for use in solar energy applications in Suan Sunandha Rajabhat University and neighbor areas.

Influence of Morphology on the Optical Properties of Self-Grown Nanowire Arrays

Nanostructured materials such as nanowire arrays often absorb light more strongly than thin films, so they can be used to improve the performance of solar cells. In this study, a series of self-grown Cu2S nanowire arrays with different diameters, lengths, and morphologies is prepared by solid–gas reaction between Cu foil and a mixture of H2S and O2. The structure of the arrays is characterized by XRD, TEM, XPS, and Raman. Their light absorption performance is investigated systematically by diffuse reflectance and photoluminescence spectroscopy. The nanowire arrays are single-crystal Cu2S semiconductors, and their band gap can be adjusted by changing the morphology, diameter, and length of nanowires in the arrays. The light-absorption ability is enhanced from 70% for a planar Cu2S film to 93.5% for a Cu2S nanowire arrays and is less sensitive to both the wavelength and incident angle of light because of the morphology and distribution of the nanowires. The light absorption is high (about 92–95%) over a wide range of wavelengths (240–670 nm) and only decreases by 3% as the incident angle increases from 10 to 40°. This research shows the potential of Cu2S nanowire arrays for use in solar energy applications.

Satellite-derived solar resource maps for Myanmar

Solar resource maps for use in solar energy applications have been produced for Myanmar. A satellite-based solar radiation model, originally developed for the tropics, was improved and applied for the region. A 13-year period (1998–2010) of imagery data from GMS 5, GOES 9 and MTSAT-1R satellites was used as the main input in the model. The absorption and scattering of solar radiation by various atmospheric constituents was also taken into account. The absorption of solar radiation due to water vapour was estimated from precipitable water database obtained from the National Center for Environmental Protection (NCEP), USA. The total column ozone obtained from TOMS/EP and OMI/AURA satellites were used to calculate solar radiation absorption by ozone. The visibility data observed at meteorological stations in Myanmar and neighbouring countries were employed to estimate solar radiation depletion due to aerosols. In order to validate the model, five pyranometer stations were established in different regions of Myanmar and a two-year period of data from these stations were used for the model validation. Additionally, global solar radiation measured at 10 stations in a neighbouring country was also employed for the validation. It was found that monthly average global radiation obtained from the measurements and that estimated from the model was in good agreement, with a root mean square difference of 9.6% at monthly scale. After the validation, the model was used to estimate monthly average global radiation over Myanmar and the results were presented as solar resource maps. The maps revealed that geographical distribution of solar radiation was strongly influenced by the topography of the country and the tropical monsoons.

Controlling Morphological Parameters of Anodized Titania Nanotubes for Optimized Solar Energy Applications

Anodized TiO2 nanotubes have received much attention for their use in solar energy applications including water oxidation cells and hybrid solar cells [dye-sensitized solar cells (DSSCs) and bulk heterojuntion solar cells (BHJs)]. High surface area allows for increased dye-adsorption and photon absorption. Titania nanotubes grown by anodization of titanium in fluoride-containing electrolytes are aligned perpendicular to the substrate surface, reducing the electron diffusion path to the external circuit in solar cells. The nanotube morphology can be optimized for the various applications by adjusting the anodization parameters but the optimum crystallinity of the nanotube arrays remains to be realized. In addition to morphology and crystallinity, the method of device fabrication significantly affects photon and electron dynamics and its energy conversion efficiency. This paper provides the state-of-the-art knowledge to achieve experimental tailoring of morphological parameters including nanotube diameter, length, wall thickness, array surface smoothness, and annealing of nanotube arrays.

Thiocyanate Linkage Isomerism in a Ruthenium Polypyridyl Complex

Ruthenium polypyridyl complexes have seen extensive use in solar energy applications. One of the most efficient dye-sensitized solar cells produced to date employs the dye-sensitizer N719, a ruthenium polypyridyl thiocyanate complex. Thiocyanate complexes are typically present as an inseparable mixture of N-bound and S-bound linkage isomers. Here we report the synthesis of a new complex, [Ru(terpy)(tbbpy)SCN][SbF(6)] (terpy = 2,2';6',2''-terpyridine, tbbpy = 4,4'-di-tert-butyl-2,2'-bipyridine), as a mixture of N-bound and S-bound thiocyanate linkage isomers that can be separated based on their relative solubility in ethanol. Both isomers have been characterized spectroscopically and by X-ray crystallography. At elevated temperatures the isomers equilibrate, the product being significantly enriched in the more thermodynamically stable N-bound form. Density functional theory analysis supports our experimental observation that the N-bound isomer is thermodynamically preferred, and provides insight into the isomerization mechanism.

Improved chemical deposition and thermal emittance of tin (iv) oxide (SnO2) thin films for photothermal conversion of solar energy and possible applications

Thin films of tin (iv) oxide (SnO2) were deposited on six polished sample plates of stainless steel 430 using improved chemical bath deposition (CBD) method at 302 K and pH value of 12.4 for different deposition time of 16 to 36 h at 4 h interval, respectively. Ethylenediamine tetra acetate (EDTA) was used to stabilize the deposition at the required pH value. The thermal emittance values of the polished and coated sample plates were determined before and after the deposition of films, respectively, using thermocouple potentiometer. The average thermal emittance value of the uncoated polished sample plate is 0.15 ± 0.01 while thermal emittance values of the coated sample plates vary from 0.15 to 0.19 ± 0.01. The film thickness of the coated sample plates varies from 33.73 to 77.59 µm. These low thermal emittance values compare well with those obtained for oxidized stainless steel selective surfaces. The coated sample plates with most favorable conditions of thermal emittance 0.17 to 0.18 ± 0.01 and film thickness 45.70 to 69.18 µm could find applications in photothermal conversion of solar energy. The improved chemical bath deposition technique could be employed at different pH values with suitable deposition time to fabricate selective surfaces for use in solar energy applications. Key words: Improved chemical bath deposition (CBD) method, thermal emittance of tin (iv) oxide (SnO2), thin films and possible applications in solar thermal devices.

Gas turbine cycles for hybrid solar power plants

Nowadays development of solar central receiver tecnology, with volumetric receivers heating air, asks for a thermodynamic cycle able to handle such high temperatures with high efficiency and ease of integration on a hybrid solar power plant. Todays Gas Turbine technology has turbine inlet temperatures of the same order as maximum temperatures experimented on volumetric receivers, and renders itself for a rather easy integration of solar energy input on a hybrid scheme. In this paper we analyse several gas turbine cycles for their use in solar energy applications, giving some insight on how to design and/or use them in solar thennal power plants.

Chemical oxidation and spectral selectivity of austenitic stainless steel AISI 321 (for use in solar-energy applications)

Polished samples of austenitic stainless steel AISI 321 were chemically oxidized in 0.1–0.6 M aqueous solutions of chromic and sulphuric acids at 90 °C for an oxidation time of 25 min, as well as for oxidation times ranging from 10 to 32 min in 0.6 M solution. Chemical oxidation of the stainless steel produced interference films ranging in colour from light-blue to deep-blue, purple-red and peacock-green. Measurements of solar absorptance ( α s ) and total hemispherical thermal emittance ( ϵ h ) showed that all the oxidized surfaces were spectrally selective. The most favourable spectrally selective surface was deep-blue in colour and it had values of α s = 0.85 ± 0.01 and ϵ h = 0.18 ± 0.01. This surface was prepared after an oxidation time of 12 min at a concentration of 0.6 M of chromic and sulphuric acids. For the unoxidized polished stainless steel, the α s and ϵ h were 0.38 ± 0.01 and 0.15 ± 0.01 respectively. No significant changes in the optical properties of the films were observed after 6 months exposure to highly humid tropical weather conditions.

Toxicological assessment of heat transfer fluids proposed for use in solar energy applications, II

Ten commercially available solar heat transfer fluids as well as three samples of used fluids (an ethylene glycol, a propylene glycol, and a silicone fluid) obtained from operating solar hot water systems were evaluated for acute oral toxicity in female rats and for dermal and ocular irritation in female rabbits. Mutagenicity testing was conducted in the Salmonella mutagenicity assay (TA 1538, TA 98, TA 1535, TA 100). Oral LD 50 values ranged from 7.0 g/kg for ethylene glycol-based products to >24 g/kg for propylene glycol, hydrocarbon oils, and silicone fluids. None of the solar fluids was mutagenic at the concentrations tested nor caused more than a slight ocular or dermal irritation. No appreciable differences were observed in evaluations between used and unused fluid samples. The results indicate that the fluids may be considered relatively safe for residential solar energy applications, although based on toxicity testing propylene glycol should be preferred over ethylene glycol. Trifluoroethanol (Fluorinol 100) was included in these studies because of its probable use as a working fluid in organic Rankine cycle waste heat recovery systems. Trifluoroethanol had an LD 50 of 0.21 g/kg, was not irritating to rabbit skin nor mutagenic in Salmonella, but demonstrated severe ocular toxicity.

Toxicological assessment of heat transfer fluids proposed for use in solar energy applications

The rapid expansion of solar technology will result in the introduction of new materials into large numbers of residential dwellings. While some of these materials have been evaluated toxicologically for industrial applications, their use in residential solar energy systems require that they be more closely scrutinized for human health hazards. Twenty-one commercial heat transfer fluids which included ethylene and propylene glycol, silicone oils, and various hydrocarbon oil formulations were evaluated for acute oral toxicity in the rat, dermal and ocular irritation in the rabbit, and mutagenic potential in the Salmonella mutagenicity (Ames) test (TA 1538, TA 98, TA 1538, TA 1537, TA 100). Oral, 24-hr LD50 values ranged from 1.9 g/kg for a polyalkylene glycol formulation to > 24 g/kg for most hydrocarbon and silicone oils and propylene glycol-based products. None of the fluids were more than mildly irritating to rabbit skin. One fluid produced reversible corneal damage and transient conjunctivitis was observed in most animals treated with hydrocarbon oil and ethylene glycol formulation. None of the fluids were mutagenic in the Ames test at concentrations ranging from 10 μg to 100 mg per milliliter. These results suggest that most of the fluids may be considered relatively safe for use in residential solar energy applications.