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Comparative studies on thermal efficiency of single and double glazed 
		flat plate solar water heater

Comparative studies on thermal efficiency of single and double glazed flat plate solar water heater

Soteris A. Kalogirou [1] performed an analysis of the environmental problems related to the use of conventional sources of energy and the benefits offered by renewable energy systems. The various types collectors including flat plate, compound parabolic, evacuated tube, Fresnel lens, parabolic trough, parabolic dish and heliostat field collectors were followed by an optical, thermal and thermodynamic analysis of the collectors and a description of the methods used to evaluate their performance. The thermal performance of the solar collector was determined by obtaining values of instantaneous efficiency for different combination of incident radiation ambient temperature and inlet fluid temperature
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An Entropy Approach to a Practical Limit of the Efficiencies of Developed and Multijunction Solar Cells

An Entropy Approach to a Practical Limit of the Efficiencies of Developed and Multijunction Solar Cells

Starting from a previously postulated definition of electric current as a flow of electromagnetic waves that have a specified, positive or negative, potential, it was possible to prove that the classical definition of thermoelectric effect as conversion of thermal energy into electrical energy implies the truth of such postulated definition of electric current. So, it was possible also to prove that the photoelectric and the photovoltaic effects are driven by a similar effect as the Seebeck effect which depends mainly on the thermal potential of the incident radiation and the interacting materials. We use such conclusion to deal with the photovoltaic cells as a thermoelectric power generator and to find a new limit of the efficiency of advanced and the multijunction solar cells that ex- ceed the broken limit of Shockley and Queisser. The found limit proves the conversion of the incident thermal radiation into electric current by the photovoltaic effect is a reversible process whose efficiency equals the effi- ciency of a Carnot cycle operating between the temperatures of the source of radiation and of the photovoltaic junctions.
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The structure of the Au(111)/methylthiolate interface : new insights from near edge X ray absorption spectroscopy and X ray standing waves

The structure of the Au(111)/methylthiolate interface : new insights from near edge X ray absorption spectroscopy and X ray standing waves

Measurements of near-edge X-ray absorption fine structure (NEXAFS) have been widely used to investigate the orientation of molecular species on surfaces [13]. In this approach the main spectral features seen are identified as excitations from a core level of known symmetry (usually a totally-symmetric s-state) into unoccupied molecular orbital states, also referred to as local intra-molecular scattering resonances. The known symmetry of these final-state orbitals, combined with selection rules applied to data recorded in different polarisation directions of the incident radiation, provides the basis of the orientational information. Such a description regards the NEXAFS as an entirely intramolecular phenomenon, with the surface primarily acting as a means of orienting the molecule in space, although energetic shifts in these scattering resonances may be attributable to changes in intramolecular bondlengths induced by the interaction with the substrate. In reality, however, the bonding of a molecule to a surface must introduce new unoccupied molecular orbitals involving substrate atoms or, equivalently, strong electron scattering resonances involving substrate atoms.
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Adoption of M- Wallet: A way Ahead

Adoption of M- Wallet: A way Ahead

Birefringence is the optical property of a material having a refractive index that depends on the polarization and propagation direction of light. These optically anisotropic materials are said to be birefringent (or birefractive). The birefringence is often quantified as the maximum difference between refractive indices exhibited by the material. Crystals with asymmetric crystal structures are often birefringent, as well as plastics under mechanical stress. Birefringence is responsible for the phenomenon of double refraction whereby a ray of light, when incident upon a birefringent material, is split by polarization into two rays taking slightly different paths. This effect was first described by the Danish scientist RasmusBartholin in 1669, who observed it in calcite, a crystal having one of the strongest birefringence. However it wasn't until the 19th century that Augustine-Jean Fresnel correctly described the phenomenon in terms of polarization, understanding light as a wave with field components in transverse polarizations (perpendicular to the direction of the wave vector. The simplest (and most common) type of birefringence is that of materials with uniaxial anisotropy. That is, the structure of the material is such that it has an axis of symmetry with all perpendicular directions optically equivalent. This axis is known as the optic axis of the material, and components of light with linear polarizations parallel and perpendicular to it have unequal indices of refraction, denoted ne and no, respectively, where the subscripts stand for extraordinary and ordinary. The names reflect the fact that, if unpolarized light enters the material at some angle of incidence, the component of the incident radiation whose polarization is perpendicular
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Effect of Dilution on Thermovoltage Generation using Homeopathic Nanomedicine Zincum Oxydatum

Effect of Dilution on Thermovoltage Generation using Homeopathic Nanomedicine Zincum Oxydatum

As the basic requirement of any solar to electrical conversion system is obviously the absorption of a significant part of the incident radiation, our study of[r]

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Investigation of the nature
of light scattering by water

Investigation of the nature of light scattering by water

Capabilities of light scattering effects for researches of structural properties of water are analysed. It is shown that measuring of indicatri с es of light scattering by water for different incident radiation intensities make it possible to determine degree of water polydispersity, along with dimensions and concentration of scat- tering centres. We provide information on how the ions contained or gases dis- solved in the water, the temperature, structural phase transitions, mechanical in- fluence, purification efficiency and the sources of water affect the characteristics of the scattering centres, thus facilitating some important conclusions about the structure of water clusters.
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Influence of atomizing voltage on fluorine doped tin oxide via spray pyrolysis technique

Influence of atomizing voltage on fluorine doped tin oxide via spray pyrolysis technique

material deposited with 3.8 kV, 4.0 kV and 4.2 kV, which represent sample FT1-FT3 showed a non-linear plot and observed to be a non Ohmic semiconducting material. It was also noticed that as the atomizing voltage of the depositing material increases the thickness of the films increases. The resistivity of the material deposited increases and decreases at 4.0 kV as the atomizing voltage and thickness of the films increases. The electrical conductivity of the material deposited increases with respect to the atomizing voltage and thickness respectively. It was observed that as the optical absorbance and reflectance decreased the wavelength of the incident radiation and transmittance enhanced as the wavelength of the incident radiation increased and the band gap energy of the films were observed to be at the range of 2.70-3.10 eV.
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Coherent Backscattering of Circularly Polarized Light from a Disperse Random Medium

Coherent Backscattering of Circularly Polarized Light from a Disperse Random Medium

In the current paper with a further development of the MC technique mentioned above we study numerically the coherent and non-coherent backscattering of circularly polarized light from a turbid tissue-like random medium. Strong multiple scattering typical for most of biological tissues leads to the loss of initial polarization, direction, phase and wavefront [1, 2, 4] of incident electromagnetic radiation. Nevertheless, the polarization of backscattered light survives more scattering events than the direction of its propagation, whereas the helicity of the backscattered light depends noticeably on the size of scattering particles [15–18]. The backscattered circular polarized light is expected to consist mainly of the cross-polarized component resulting from the specular reflection. However, it turns to be true only for the scatterers, which size is smaller than wavelength of incident radiation; for the media with larger scatterers the opposite situation happens [16, 17]. This phenomenon, known as the polarization memory, was explained by specific features of the Mie tensor phase function.
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Theoretical description of functionality, applications, and limitations of SO 2cameras for the remote sensing of volcanic plumes

Theoretical description of functionality, applications, and limitations of SO 2cameras for the remote sensing of volcanic plumes

vast variety of applications. However, both the technical im- plementation of the instrument as well as the data retrieval procedures are still in an early stage of development. Sev- eral advances along both lines were made in the scope of this study. The optical system described in Sect. 3.1 greatly reduces the dependence of the instrument sensitivity on the viewing direction. The use of a back-illuminated CCD detec- tor and the associated increase in quantum efficiency (factor of 5) enhances the signal-to-noise ratio of a given incident radiation intensity by more than a factor of 2 compared to front-illuminated chips. Finally, the maximum possible sen- sitivity was achieved by selecting filters according to the the- oretical considerations explained in Sect. 3.2.
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Development and Test of a New Solar Air Heat Exchanger for the Linear Mirror II System

Development and Test of a New Solar Air Heat Exchanger for the Linear Mirror II System

There is a second effect, which presumably can increase the performance of such a bellow-shaped absorber: for a given direction of incidence, the number of reflections of a light ray will always be the same, regardless of where it first hits the surface. The density of these reflections instead will very much depend on the initial point of incidence. Rays incident close to each bellow vertex will de- posit most of their energy on a very small surface, heating then the steel very much. This means that even if the incident radiation is distributed uniformly along the y-direction, the surface will not show a uniform temperature at all: it will be hottest in a region, which supposedly will be relatively well protected against heat loss to the environment. A detailed study of this effect is however not the priority oh this article and should be studied in a further dedicated in- vestigation.
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Design and Analysis of Parabolic Reflector with High Gain Pencil Beam and Low side lobes by Varying feed

Design and Analysis of Parabolic Reflector with High Gain Pencil Beam and Low side lobes by Varying feed

configuration of its surface is upgraded. In geometrical optics, if a beam of parallel rays is incident upon a reflector whose geometrical shape is a parabola, the radiation will converge at spot, which is known as a focal point. In the same manner, if a point source is placed at the focal point, the rays reflected by a parabolic reflector will emerge as a parallel beam. Rays that emerge in a parallel formation are usually said to be collimated. Collimation is often used to describe the highly directional characteristics of an antenna even though the emanating rays are not exactly parallel. Since the transmitter (receiver) is placed at the focal point of the parabola, the configuration is known as front-fed.
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A BRIEF REVIEW OF COMPUTING THE PERFORMANCE OF EXISTING SOLAR DRYERS BY OPTIMAZING THE TILT ANGLES OF SOLAR COLLECTORS TO RECEIVE MAXIMUM SOLAR RADIATION

A BRIEF REVIEW OF COMPUTING THE PERFORMANCE OF EXISTING SOLAR DRYERS BY OPTIMAZING THE TILT ANGLES OF SOLAR COLLECTORS TO RECEIVE MAXIMUM SOLAR RADIATION

Researchers have introduced a variety of isotropic and anisotropic models, suggesting relations to determine the ratio of the average daily diffused radiation incident on an inclined surface to that on a horizontal surface (Rd). A. K. Yadav and S. S. Chandel conducted a review of the solar radiation models, where each model had its own limitations and conditions [6]. Nooriana et al. made an evaluation in which 12 models where investigated to estimate the hourly diffused radiation on inclined surfaces and compared the results to actual measured data [7]. If one of those models can be validated for a certain place and atmospheric conditions, an optimum tilting angle can be reached by varying tilt angle (β) from 0 to 90 until the solar radiation on the tilted surface is maximized.
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Thermal Analysis and Experimental Validation of Parabolic Trough Collector for Solar Adsorption Refrigerator

Thermal Analysis and Experimental Validation of Parabolic Trough Collector for Solar Adsorption Refrigerator

Thermal analysis of this kind of solar collectors has been made by some re- searchers [13] [14]. Kalagirou [15] performs an analysis considering all mechan- isms of heat transfer for a solar tracking parabolic trough collector, Jin et al . [16] uses the Monte Carlo Ray-Trace method (MCRT) to determine the solar flux, and Hachica et al . [17] develops a numerical model contemplating the non- uniformity of the received solar radiation and the heat losses along the cross- section of the absorber tube. Huang et al . [18] coupled a thermal model with an optical model in order to predict the performance of a PTC. Other researchers have developed computational models combining the Finite Volume Method (FVM) and the MCRT method, [19] [20].
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Numerical Analysis of an Industrial Polycrystalline Silicon Photovoltaic Module Based on the Single Diode Model Using Lambert W Function

Numerical Analysis of an Industrial Polycrystalline Silicon Photovoltaic Module Based on the Single Diode Model Using Lambert W Function

sorber layer. The photoelectron generation rate is directly proportional to the incident light flux power density [16] and should take into account the carri- er-injection efficiency. The absorber layer is responsible for absorption and conversion of incident photons into charge carriers.

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Design of an Antireflection Coating for Mid- wave
Infrared Regions in the Range (3000-5000) nm

Design of an Antireflection Coating for Mid- wave Infrared Regions in the Range (3000-5000) nm

substrate [6]. Silicon (Si) using as a substrate. For the normal incidence, the reflectance of Si as a function of wavelength are shown in figure (1). It clear that the reflectance is high (R~30.31 %). ZnS and CdS using as low and high index coating materials. In this section, five theoretical designs of antireflection coating have been suggested. each design have a different number of layer or different arrangement of the layers from the others in order to minimize the reflectance of silicon. Figure (2-6) shows the reflectance as a function of wavelength at normal incidence for the five design, the design [Air / LHL /Si] have minimum reflectance (high transmittance) in design wavelength. So, we using this design to study the effect of angle of incident on the performance of this design. Figure (7-11) shows the effect of angle of incident on the reflectance as a function of wavelength of the design [Air / LHL /Si]. When angle of incidence increase the reflectance increase with shift toward shorter wavelengths, this shift may be as result of varying the optical thickness of layer due to the oblique incidence of plane electromagnetic wave.
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Heat Transfer Optimization in Air Flat Plate Solar Collectors Integrated with Baffles

Heat Transfer Optimization in Air Flat Plate Solar Collectors Integrated with Baffles

The solar collector is a kind of duct heat exchanger that transfers heat energy from incident solar radiation to the fluid passing through it. It absorbs solar ra- diation through glazing, converting it to heat energy and transferring it to a working fluid [20]. The collector comprises of absorber plate in a flat rectangular housing, glass cover on the upper surface and the insulation on other sides to limit the thermal losses. The solar energy absorbed by the plate is transferred to the fluid flowing within the collector channel [21]. To have effective thermal ef- ficiencies of a flat plate solar collector, heat has to be efficiently transferred from the absorber plate to the flowing air. Heat transfer coefficient inside the solar collector is an important parameter that affects the efficiency of the collector [22]. Researchers have recommended various modifications to enhance heat transfer rate in solar collector by incorporating different modifications between absorber plate and glass plate [23].
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An Investigation on the Human Thermal Comfort from a Glass Window

An Investigation on the Human Thermal Comfort from a Glass Window

Large commercial buildings usually have their building envelope made of glass window. These glass windows shall receive plenty of heat gain into building from the incident solar radiation especially when the building is located in a tropic zone near the equator. The large air conditioning system is usually needed to get rid of the heat gain from solar radiation. Besides the heat gain through the glass window, the glass window also has the effect on the person who sits nearby in term of thermal comfort. Thermal comfort is defined as the condition of mind that expressed satisfaction with the thermal environment (ISO 7730 [1] and ASHRAE Standard 55 [2]). The important parameters which commonly used to describe the thermal comfort condition are the mean radiant temperature, the predicted mean vote (PMV) and the predicted percentage of dissatisfied (PPD). Fanger [3] has related PMV value to the parameters that affects the thermal comfort. Rizzo et al. [4] have developed the algolithms for calculating the mean projected area factors of the seated and standing persons. Athienitis and Haghighat [5] have performed the experimental and numerical study of the effects of solar radiation on the indoor environment. They presented the effects of both transmitted direct solar radiation and transmitted diffuse solar radiation on the human thermal comfort in terms of globe temperature. Cannistraro et al. [6] developed the view factors between human body and rectangular surfaces in parallelepiped environments in the form of polynomial equation. La Gennusa et al. [7] have developed the mathematical model to determine the mean radiant temperature of a subject exposed to solar radiation. Sullivan [8] and Lyons et al. [9] have developed the relation to calculate the PMV that accounted for the solar radiation effect. Chaiyapinunt
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Design, Fabrication and Thermal Analysis of Trapezoidal Solar Cooker with Water Heating Facility

Design, Fabrication and Thermal Analysis of Trapezoidal Solar Cooker with Water Heating Facility

ABSTRACT: Energy is an important source for all sectors of any country’s economy. Due to rapid deterioration in the supply of fossil fuels, the solar energy can be the most appropriate option compared to other alternative energy resources. The solar cookers have a relevant place in the present fuel consumption pattern. But the position of the sun varies continuously throughout the daytime which affects the absorption rate of system and increases human effort. In this project we are designing a trapezoidal solar cooker havinginternal mirror reflectors placedsuch that the solar radiation incident upon the surface gets concentrated towards the Centre of the cooker. This increases the concentration ratio of the system and enhances the thermal conductivity. Along with it water heating has been achieved by placing spiral copper coil at the bottom of solar cooker which utilizes the waste heat which was earlier absorbed by the sidewalls but now are reflected by the internal mirror reflectors.
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Field Study and Modeling of an Unglazed Transpired Solar Collector System

Field Study and Modeling of an Unglazed Transpired Solar Collector System

Instantaneous efficiency according to equation 3.2.7 was calculated for each data point with the new controls where both fans were operating and the solar radiation was above 200 W/m 2 (63.4 BTU/hr/ft 2 ). The average daily instantaneous efficiency for these data points ranged from 32% to 55%. Previous performance studies of demonstration projects showed that these systems had annual average efficiencies of 57-72% (Brunger 1999). Therefore, the initial results from the 2003 heating season indicate that this system would have a lower annual efficiency than typical systems. The lower efficiency may be due to operating below the design air distribution flow rate (about 8600 cfm instead of 12000 cfm). A lower operating flow results in a higher temperature rise in the collector, but still less total heat delivered to the building.
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Development of Collective Thomson Scattering Diagnostic for Bulk and Fast Ions in the Large Helical Device

Development of Collective Thomson Scattering Diagnostic for Bulk and Fast Ions in the Large Helical Device

Collective Thomson scattering system has been devel- oped to measure the velocity distribution function in JET, TEXTOR, ASDEX-UG, and has been designed for ITER [1–3] in fusion plasma diagnostics. The high power gy- rotron with the frequencies of 140, 110, 105, and 60 GHz and the power of a few hundred kW ∼ MW is utilized as a probing beam for each device. The scattered radiation is resolved at a receiver to obtain the scattered spectra, which is analyzed by the scattering theory based on the electro- magnetic fluctuation.

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