Incident Sun Research Articles

Selection of Best Materials and Parametric Optimization of Solar Parabolic Collector Using Fuzzy Logic

This paper focused on selection of best materials for absorber tube and reflective surfaces of Solar Parabolic Collector (SPC) using fuzzy logic, after analysing the material data. The glass mirror and Aluminium absorber have been identified as best materials. These selected materials are replaced in existing experimental setup. An experimental design is prepared based on the considered parabolic collector parameters: Absorptivity, Reflectivity and Period of Sun Incidence. During experiments, outlet temperature of water and discharge is recorded for each experimental run. These data are analyzed using fuzzy Logic integrated with the Taguchi method and optimal parameter combination has been found.

Hourly and Monthly Variation in Shading and Blocking of Aperture Area in a Linear Fresnel Reflector Field

In a Linear Fresnel Reflector (LFR) field, rows of reflectors direct the incident sun rays towards a linear receiver. Some portion of reflector aperture area gets shaded and blocked by neighboring reflector-rows. Thus, complete utilization of reflector aperture area is hampered. Continuously changing sun's position in sky demands appropriate tracking of reflectors, which leads to varying shaded and blocked aperture areas over a day. Orientation of the field also plays an important role. Orientation is defined by the tracking axis of the reflector. For example, North-South (N-S) oriented LFR field is the one having tracking axis of reflector along N-S. In the present work, analytical expressions are used to find out shaded and blocked aperture areas. Results for hourly and monthly variation in shaded and blocked aperture areas for different orientations of the field, different values of spacing between reflector-rows and height of receiver are plotted and compared.

Analysis of a Low Concentration Solar Plant with Compound Parabolic Collectors and a Rotary Expander for Electricity Generation

In the last decade many studies have been carried out on low temperature solar compound parabolic collectors (CPC) that are able to collect solar direct and diffuse radiation without the need of a tracking system, especially if coupled with small scale Organic Rankine Cycles for electricity and heat combined production.This paper presents a study on a thermal power plant that uses an expansion device driven with pressurized vapor generated with the heat collected by a CPC solar field. The numerical model of the expansion device was developed with the simulation tool AMESim v.12 and allowed the simulation of the indicated cycle of this machine for the evaluation of delivered power, isentropic efficiency and specific working fluid consumption.At the same time in this paper an analytical model of the evacuated solar CPC is presented for the evaluation of the collected heat as a function of sun incidence angle, external temperature, inlet carrier fluid temperature and mass flow rate.These two models were used in conjunction for the analysis of the electricity that may be generated as a function of the ambient and working conditions. This study was performed in steady state conditions and with several working fluids to evaluate the power that would be delivered by a given displacement expander rotating at a fixed speed.The results are given in terms of delivered power, thermal efficiency and amount of collecting surface needed for a given displacement expansion machine, calculated for several working fluids and different operating conditions.

Relationship between Sun Exposure and Kidney Cancer: Preliminary Experience with the Evaluation of Recreational UV Exposure

Recent findings reported an inverse relationship between solar ultraviolet-B (UV-B) exposure and mortality from various types of cancers, including renal cancer. We reviewed the literature concerning the relationship between sun exposure and incidence of kidney cancer. We performed a case-control study, evaluating recreational sun exposure in 50 kidney cancer patients and 50 controls.A questionnaire concerning sun exposure habits during childhood, adult life and in the previous 2 years was filled in by every patient. The questionnaire focused on: hours/day spent in the sun during summer; hours/day spent sunbathing (considering as well which kind of UV protection was used); sunburns; holidays in tropical countries. We found and analyzed few articles concerning the relationship between kidney cancer and sunlight exposure. The two cohorts of patients we evaluated were homogeneous for age, phototype, origin and living area.We found no statistically significant differences between sun exposure in patients affected by kidney cancer and controls, both during childhood and adult life; no differences were found in the use of sunscreens either. Recreational sunlight exposure does not differ in our cohorts of patients and controls; studies on greater cohorts are needed to evaluate the effect of recreational sun exposure in the development of kidney cancer.

Mercury’s radius change estimates revisited using MESSENGER data

Mapping tectonic features using MESSENGER data mainly acquired at high Sun incidence angle (>50°) reveals previously undetected structures. The analysis of the latter features determines an upward revision of measurements of density and spatial distribution of tectonism and thus of estimates of average contractional strain and planetary radius decrease. We calculated an average surface contraction of ∼0.23–0.30% (∼0.28% for fault dip angle θ=30°) within an area corresponding to 21% of the planet. This strain, extrapolated to the entire surface, corresponds to a decrease in radius of about 2.4–3.6km (∼3.0km for θ=30°). These values are three–four times higher with respect to previous estimates and are compatible with results from thermomechanical models.

Influence of light environment on yield determinants and components in large olive hedgerows following mechanical pruning in the subtropics of the Southern Hemisphere

Olive cultivation has expanded considerably beyond the Mediterranean Basin to include new areas in the Southern Hemisphere. This study evaluated the response functions of yield determinants and components to photosynthetically active radiation (PAR) in a large olive hedgerow (cv. ‘Arbequina’) in subtropical Argentina, and assessed whether mechanical pruning altered these relationships. Mechanical pruning was applied at the end of the winter dormant period to the east side and top of hedgerows oriented North–South, while the other side was left unpruned. The PAR distribution and leaf density at different positions within the hedgerow were measured over the two subsequent growing seasons with inflorescence density, fruit set, fruit density, individual fruit dry weight, and oil content (%) being assessed the second growing season. Hedgerow size increased substantially during the first season, especially on the pruned side and top, reducing transmitted PAR in much of the canopy to less than 20% of full Sun incident PAR values above the orchard. The relationship between leaf density (and thus number of axillary buds) and PAR was bilinear for the canopy positions within the unpruned side with a threshold of about 15% of full Sun PAR, above which leaf density did not increase. No relationships between leaf density and PAR were found within the pruned side and top. In contrast, inflorescence density exhibited a threshold of 18% of PAR for canopy positions within both the pruned and unpruned sides, although no relationship was apparent for the pruned top. Neither fruit set nor yield component relationships with PAR were affected by pruning. Fruit set had a linear response to PAR for the observed range of PAR values within the hedgerow (approx. 0–50% of full Sun). Individual fruit dry weight and oil content (%) also showed linear responses to PAR. The results suggest that oil production in large olive hedgerows (height×width) is limited by low solar radiation within the canopy, and that substantial vegetative growth triggered by mechanical pruning may be an important contributor to this limitation under current management practices in subtropical climates.

Design and Development of a Sun Tracking Mechanism Using the Direct SMA Actuation

An attempt has been made in this work to develop a simple yet efficient sun tracking mechanism (SSTM) using smart shape memory alloy (SMA). This mechanism is directly activated by the sun dispensing with the requirement of an additional external source to power it. The SMA element incorporated in the SSTM device performs the dual functions of sensing and actuating in such a way as to position the solar receptor tilted appropriately to face the sun directly at all times during the day. The mechanism has been designed such that the thermal stimulus needed to activate the SMA element is provided by the concentration and direct focusing of the incident sun rays on to the SMA element. This paper presents, in detail, the design and construction adopted to develop the functional model that was fabricated and tested for performance.

Tumor de colisão de pele do pescoço

The collision or mixed tumor is a malignant neoplasm of the skin related to sun exposure and incidence rates of up to 1.5%. It displays a distinctive clinical behavior in relation to other malignancies of the skin and the histological diagnosis, characterized by the collision between a basal cell carcinoma and squamous cell carcinoma, i.e., two malignancies with distinct histologies and sharp interface between them. The case reported was of a male, 73-year-old patient, with two cervical lesions progressively growing in recent months. The chosen treatment was surgery. Histological examination showed the presence of squamous cell carcinoma adjacent to basal cell carcinoma. These tumors preferentially occur in light-skinned men in the fifth or sixth decades of life. Their most common location is in the head and neck, especially in the central part of the face. The differential diagnosis of basal-squamous carcinoma is defined by distinct histological criteria, since both tumors have similar clinical behavior. Local recurrence rates vary from 12% to 45%, whereas regional ones are of approximately 7.5%. The main prognostic factors are gender, surgical margins, perineural infiltration and lymph node status. The treatment of choice is resection, radiotherapy being indicated as adjuvant or to inoperable lesions. Local recurrence is the main limiting factor in disease-free survival, with poor results.

Rendering Grass Blowing in the Wind with Global Illumination

We have simulated a time varying wind field using the lattice Boltzmann model, and its effect on blades of grass with a simple mass-spring model. We present a global illumination model for multiple scattering of incident sun and sky illumination within the field of grass. We model the grass as a continuous distribution of infinitesimal colored scattering flakes and solve a system of differential equations for the radiance transport. We repeat this for a collection of grass bending directions and amounts, and then interpolate the solutions when rendering animations of blowing grass.

Improving the efficiency of thin film tandem solar cells by plasmonic intermediate reflectors

Thin film tandem solar cells made of amorphous and microcrystalline silicon provide renewable energy at the benefit of low material consumption. As a drawback, these materials do not posses the high carrier mobilities of their crystalline counterpart which limits the feasible material thickness. For maintaining the light absorption as high as possible, photon management is required. Here we show that metallic nanodiscs that sustain localized plasmon polaritons can increase the efficiency of such solar cells if they are incorporated into the dielectric intermediate reflector separating the top and the bottom cell. We provide quantitative estimates for the possible absorption enhancement of optimized bi-periodic nanodiscs that are feasible for fabrication. Emphasis is also put on discussing the impact of obliquely incident sun light on the solar cell performance.

Modulation of Donor−Acceptor Interface through Thermal Treatment for Efficient Bilayer Organic Solar Cells

In this article, we demonstrate the effect of donor−acceptor (D-A) interface on the performance of bilayer organic solar cells. Solution processing was used to develop liquid crystal poly(9,9′-dioctylfluorene-co-bithiophene) (F8T2) polymer films and variable morphology of the films was achieved by varying the annealing temperature. The morphology of the annealed active layers signature a well-aligned nanodomain feature with an interdegitated structure at 200 °C. The devices with bilayer configuration, ITO/PEDOT:PSS/F8T2/C70/Al, have yielded a power conversion efficiency (PCE) of 3.4(±0.2)% under 1 sun incident radiation. We attribute the high PCE to the increased D-A junction interface and balanced charge transport between electron/hole transport layers.

Analysis of microwave brightness temperature of lunar surface and inversion of regolith layer thickness: Primary results of Chang-E 1 multi-channel radiometer observation

In China’s first lunar exploration project, Chang-E 1 (CE-1), a multi-channel microwave radiometer was aboard the satellite, with the purpose of measuring microwave brightness temperature from lunar surface and surveying the global distribution of lunar regolith layer thickness. In this paper, the primary 621 tracks of swath data measured by Chang-E 1 microwave radiometer from November 2007 to February 2008 are collected and analyzed. Using nearest neighbor interpolation based on the sun incidence angle in observations, global distributions of microwave brightness temperature from lunar surface at lunar daytime and nighttime are constructed. Using the three-layer model (the top dust-soil, regolith and underlying rock media) for microwave thermal emission of lunar surface, the measurements of brightness temperature and dependence upon latitude, frequency and FeO+TiO2 content, etc. are discussed. On the basis of the ground measurements at Apollo landing sites, the observed brightness temperature at these locations are validated and calibrated by numerical three-layer modeling. Using the empirical dependence of physical temperature upon the latitude verified by the measurements at Apollo landing sites, the global distribution of regolith layer thickness is then inverted from the brightness temperature data of CE-1 at 3 GHz channel. Those inversions at Apollo landing sites are compared with the Apollo in situ measurements. Finally, the statistical property of regolith thickness distribution is analyzed and discussed.

Environmental Conditions in the Deterioration of Brick Façades

Despite the great progress made in the last few years in the manufacturing of ceramic bricks and their fitting technology, brick facades still suffer from a series of critical problems and in some cases the number of pathologies have even increased. The most common and critical problem of brick facade enclosures is the detachment of pieces from the die, thus the loss of union. This detachment can be associated with three different causes: an inadequate prescription of the griping material, the absence of control joints to make the enclosure compatible, and the incidence of sun and rain on the facades. While the first two factors are directly related to the design process, the fitting techniques, training of the work force, and quality control efficiency, the third factor is related to environmental factors that generate a different microclimate in each facade depending on its orientation. This paper describes some examples of detachments in brick facade enclosures and the main causes that originated from them.

SIMULATING SEASONAL PATTERNS OF INCREASED GREENHOUSE CROP PRODUCTION BY CONVERSION OF DIRECT RADIATION INTO DIFFUSE RADIATION

ISHS III International Symposium on Models for Plant Growth, Environmental Control and Farm Management in Protected Cultivation (HortiModel 2006) SIMULATING SEASONAL PATTERNS OF INCREASED GREENHOUSE CROP PRODUCTION BY CONVERSION OF DIRECT RADIATION INTO DIFFUSE RADIATION

Radiative transfer model STORM for full Stokes vector calculations in the visible and near infrared spectral range

Abstract. Based on the Matrix-Operator Method the radiative transfer code STORM (STOkes vector Radiative transfer Model) is introduced, which was developed in a joint project of DLR and Institut f{ü}r Weltraumwissenschaften-Freie Universität Berlin. STORM calculates the Stokes parameters (I, Q, U, V) in a plane parallel, multi layered atmosphere in the visible and near infrared spectral range. The scattering characteristics of aerosols are determined by Mie theory. The surface represents a Lambertian reflector or a wind ruffled water surface described by Cox-Munk model. The results of one calculation are the upward and downward directed Stokes parameters for one wavelength at a desired number of sun incident and viewing angles at varying altitudes in the principal plane and other azimuth angles. STORM is applied for an analysis in view of designing downward looking Earth observing optical remote sensing systems and values of the degree of polarization are presented as generic basis for remote sensing system design and data processing.

Variable sampling adaptive control of a distributed collector solar field

Distributed collector solar fields are spatially distributed engineering systems, which aim at collecting and storing energy from solar radiation. They are formed by mirrors which concentrate direct incident sun light in a pipe where a fluid, able to accumulate thermic energy, flows. From the control point of view, the objective considered here consists of making the outlet oil temperature to track a reference signal by manipulating the oil flow, in the possible presence of fast disturbances caused by passing clouds. Although this plant may be successfully controlled by methods assuming it to be modeled as a "black box" lumped parameter system, the point of view advocated in this paper is that explicit consideration of its distributed character leads to an increased control performance. In this respect, the contributions of this paper are twofold: First, a controller relying on variable sampling is developed. This is derived from the partial differential equation describing the oil temperature evolution in time and space on the field and has the effect of linearizing the plant model. Second, the resulting performance is illustrated by means of experiments performed in an actual solar field. The experiments reported show that it is possible to make fast temperature setpoint changes, with reduced overshoot. The ideas presented are applicable to other types of industrial processes, involving transport phenomena.

Aspectos da alimentação de Bryconamericus microcephalus(Characiformes, Tetragonopterinae) no córrego Andorinha, Ilha Grande – RJ

Esse estudo foi realizado no Córrego Andorinha, localizado na vertente oceânica da Ilha Grande (23°05', 23°15'S e 44°06 e 44°23'W) e teve como objetivo determinar a dieta de B. microcephalus, bem como suas variações entre jovens e adultos. As coletas foram realizadas entre nov/99 e out/00 através de rede de espera e arrastinho (malhas 5mm e 10mm) em um trecho do riacho onde a vegetação marginal cobre 100% da localidade, o substrato é formado por areia, cascalho, rochas e folhiço. A cada ocasião de coleta 20 exemplares eram amostrados e o conteúdo estomacal analisado sob microscópio estereoscópico através do método da Freqüência Numérica. A dieta da espécie é baseada em larvas de insetos aquáticos (autóctones) e insetos terrestres (alóctones). A participação dos itens autóctones e alóctones variam sazonalmente (rSpearman=0,296; p=0,325) sendo que os ítens alóctones predominaram na estação seca. Considerando-se a importância relativa dos itens alóctones e autóctone na dieta de jovens e adultos, separadamente, observamos predomínio de itens alóctones entre os primeiros (teste t; t = 2,51; gl = 30; p = 0,018) e ausência de diferença entre os adultos (teste t; t = 0,7 9; gl = 84; p = 0.429). O valor médio do Quociente Intestinal (QI) foi 0,77, sem diferenças entre jovens e adultos (teste t; t = -0,6 2; gl = 85; p=0,45), e sugere dieta onívora fato não corroborado pela dieta registrada. Isso pode ser explicado pela pontualidade das amostras realizadas em uma localidade de baixa produção primária decorrente da baixa insolação (100% cobertura); no entanto, como migradores, esses exemplares certamente utilizam outros recursos (e.g. algas filamentosas e/ou vegetais superiores) em outras localidades onde a produção primária é incrementada pela insolação (áreas abertas), justificando a pré-adaptação anatômica da população (QI de onívoro).

Branch growth and gas exchange in 13-year-old loblolly pine (Pinus taeda) trees in response to elevated carbon dioxide concentration and fertilization.

We used whole-tree, open-top chambers to expose 13-year-old loblolly pine (Pinus taeda L.) trees, growing in soil with high or low nutrient availability, to either ambient or elevated (ambient + 200 micromol mol-1) carbon dioxide concentration ([CO2]) for 28 months. Branch growth and morphology, foliar chemistry and gas exchange characteristics were measured periodically in the upper, middle and lower crown during the 2 years of exposure. Fertilization and elevated [CO2] increased branch leaf area by 38 and 13%, respectively, and the combined effects were additive. Fertilization and elevated [CO2] differentially altered needle lengths, number of fascicles and flush length such that flush density (leaf area/flush length) increased with improved nutrition but decreased in response to elevated [CO2]. These results suggest that changes in nitrogen availability and atmospheric [CO2] may alter canopy structure, resulting in greater foliage retention and deeper crowns in loblolly pine forests. Fertilization increased foliar nitrogen concentration (N(M)), but had no consistent effect on foliar leaf mass (W(A)) or light-saturated net photosynthesis (A(sat)). However, the correlation between A(sat) and leaf nitrogen per unit area (N(A) = W(A)N(M)) ranged from strong to weak depending on the time of year, possibly reflecting seasonal shifts in the form and pools of leaf nitrogen. Elevated [CO2] had no effect on W(A), N(M) or N(A), but increased A(sat) on average by 82%. Elevated [CO2] also increased photosynthetic quantum efficiency and lowered the light compensation point, but had no effect on the photosynthetic response to intercellular [CO2], hence there was no acclimation to elevated [CO2]. Daily photosynthetic photon flux density at the upper, middle and lower canopy position was 60, 54 and 33%, respectively, of full sun incident to the top of the canopy. Despite the relatively high light penetration, W(A), N(A), A(sat) and R(d) decreased with crown depth. Although growth enhancement in response to elevated [CO2] was dependent on fertilization, [CO2] by fertilization interactions and treatment by canopy position interactions generally had little effect on the physiological parameters measured.

Polymer Electrolyte Photoelectrochemical Cells with Involatile Plasticizers: I. The n ­ Si / I − / I 2 Cell

We report results for a photoelectrochemical (PEC) cell based on n-Si-Pt/plasticized polymer electrolyte (with dissolved iodine/iodide redox couple). All elements except the electrolyte are kept the same as in earlier cells with bare (and platinized) silicon but “dry” polymer electrolyte, in order to separate out the electrolyte plasticization effect. The study is a precursor to a detailed study of novel electrolyte-containing PECs to be reported in a separate article. In the present study, the plasticizer is tetramethylene sulfone, and its incorporation is shown to increase the short circuit current by a factor of 44. Changes in iodide concentration produce an additional improvement. Effects of light intensity on photovoltage and photocurrent are reported. Short circuit photocurrents as high as 7 mA/cm2 (vs. 17 mA/cm2 with more appropriate redox couples) can be reached at 1 sun incident light intensity, without recourse to special coatings on the silicon photoanode. Factors affecting the efficiency of energy conversion are discussed. © 2001 The Electrochemical Society. All rights reserved.

Die Beiträge von direkter und indirekt diffuser Sonnenstrahlung im UV-Spektrum

Ultraviolet radiation differs in some respects from other parts of the solar spectrum. Spectroradiometric measurements were used to demonstrate how and to which extent direct and indirect diffuse radiation vary at certain wavelengths in the UV range depending on the solar elevation, i.e. during the course of a day. Measurements were done on the North Sea island of Sylt at 54° 55.5 N, 8° 18.6 E. UV-spectra were measured during a clear cloudless summer day using a double monochromator system (DM 150, Bentham Comp., Reading, England). ATeflon diffuser with an approximate cosine response served as input optic of the spectroradiometer. Direct solar radiation was measured when the receiving surface of the diffuser was arranged to be normal to the incident sun rays. A custom made aperture constructed according to the WMO guidelines for measurement of direct solar radiation by pyrheliometers (opening half-angle 2.5°, slope angle 1°) ensured that only the irradiance of the direct sun rays was measured. Conversely the diffuse radiation was measured when the horizontally adjusted diffuser was shaded from the direct sun rays by a shadow disk. To make both measurements comparable, the measured irradiance of the direct radiation was converted in relation to a horizontal plane. Out of the spectra the following six wavelengths were analyzed: 305 nm and 310 nm in the UVB and 330, 340, 360, and 380 nm in the UVA, respectively. Naturally both direct and indirect radiation increase with the elevation of the sun. However, they do so in a different manner. At low elevation up to about 30° indirect radiation prevails at all wavelengths in the UV range. At 305 nm and 310 nm this holds true even up to a solar elevation of almost 60° at noon. At these wavelengths indirect radiation contributes almost 80% to the global irradiance at 30° solar elevation and still about 56% at 60°. This means that indirect radiation exceeds direct radiation during the entire day. This relationship changes in the UVA range. The longer the wavelengths and the higher the sun the more important becomes the direct radiation. At 330 nm the irradiances of direct and indirect radiation are roughly equal at a solar elevation of 60°, At 340 nm this point of even shifts to about 50°, at 360 nm to 40 °, and at 380 nm to roughly 30 °. All in all, the shorter the wavelength the more the UV radiation is irradiated as diffuse indirect radiation scattered from the blue of the sky. This is of particular interest because the short wavelengths are precisely those which cause the most skin erythema.