Variation Of Tilt Angle Research Articles

Investigation of wind speed cooling effect on PV panels in windy locations

Environmental concerns have considerably increased the penetration of renewable energy sources in the electricity grid. Especially, the quick rise of photovoltaic (PV) installations aroused more research interests in efficiency improvement during the recent years. Even one percent more gain is of crucial importance for sustainable energy development, potential impacts of some parameters as wind speed has not been taken into account broadly in PV systems yet. This paper is intended to help project planners to accurately estimate true potential of the PV plants especially in windy locations by taking into account generally underestimated wind speed cooling effect. Firstly, optimum tilt angle variations have been investigated and secondly yearly energy comparisons are made for cases with and without considering wind speed. A more accurate mathematical model is given to estimate yearly energy gain especially in the planning stage. Particle swarm optimization (PSO) algorithm is used to find optimum tilt angles for several time intervals. Results are given in detail through a case study in a windy northern European city, Aalborg, Denmark. The presented methodology can also easily be applied to other systems located around the world.

Solar Receivers Optimum Tilt Angle at Southern Hemisphere

One of the important parameters that affects the performance of a solar collector is its tilt angle with the horizon. This is because the variation of tilt angle changes the amount of solar radiation reaching the collector surface. Meanwhile, is the rule of thumb, which says that solar collector should be orientated towards the Equator with a tilt equal to latitude, valid for high latitudes region? Thus, it is required to determine the optimum tilt for Equator facing collectors. In addition, the question may rise: how much adjustments of Equator facing solar collector tilt angle is reasonable to do during a year? A mathematical model was used for estimating the solar radiation on a tilted surface, and to determine the optimum tilt angle and orientation (surface azimuth angle) for the solar collector at any latitude. This model was applied for determining optimum tilt angle in the high latitudes zone in the Southern Hemisphere, on a daily basis, as well as for a specific period. The optimum angle was computed by searching for the values for which the radiation on the collector surface is a maximum for a particular day or a specific period. The results reveal that changing the tilt angle 12 times in a year (i.e. using the monthly optimum tilt angle) maintains approximately the total amount of solar radiation near the maximum value that is found by changing the tilt angle daily to its optimum value. This achieves a yearly gain in solar radiation up to 1.8 times of the case of a horizontal surface while the daily gain reaches 60 times approximately. Moreover, general formulas are proposed for predicting daily optimum tilt angle and optimum tilt angle over any number of days.

A study on polymorphism of hydrogen-bonded thermotropic liquid crystals

A novel mesogenic homologous series comprising of eight hydrogen-bonded liquid crystalline complexes are isolated and analyzed by forming a hydrogen bond between p-n alkyloxy benzoic acids (where n represent alkyloxy carbon number which varies from 5 to 12) and mesaconic acid, respectively. Eight synthesized complexes are subjected to Fourier transform infra-red spectroscopy, polarizing optical microscopy and differential scanning calorimetry studies to meet the basic characterization. The variation of optical tilt angle with respect to temperature in various conventional and smectic X phases are investigated and analyzed. A phase diagram is constructed to elucidate the mesogenic behavior of novel liquid crystalline series. The Cox ratio that reveals the order of various mesophases and the stability factor, to invoke the thermal stability of mesophases, is studied under the results of DSC thermogram.

A MECHANISM FOR THE DEPENDENCE OF SUNSPOT GROUP TILT ANGLES ON CYCLE STRENGTH

The average tilt angle of sunspot groups emerging throughout the solar cycle determines the net magnetic flux crossing the equator, which is correlated with the strength of the subsequent cycle. I suggest that a deep-seated, non-local process can account for the observed cycle-dependent changes in the average tilt angle. Motivated by helioseismic observations indicating cycle-scale variations in the sound speed near the base of the convection zone, I determined the effect of a thermally perturbed overshoot region on the stability of flux tubes and on the tilt angles of emerging flux loops. I found that 5-20 K of cooling is sufficient for emerging flux loops to reproduce the reported amplitude of cycle-averaged tilt angle variations, suggesting that it is a plausible effect responsible for the nonlinearity of the solar activity cycle.

Elastic and inelastic transmission of electrons through insulating polyethylene terephthalate nanocapillaries

The transmission of electrons with incident energies of 300, 500, and 800 eV through insulating polyethylene terephthalate (PET) nanocapillaries for small tilt angles near 0\ifmmode^\circ\else\textdegree\fi{} was studied. The exiting electrons showed elastic and inelastic behaviors with the inelasticity increasing with the tilt angle. This paper is an extension of our earlier work for electrons on PET reported by Das et al. [Phys. Rev. A 76, 042716 (2007)], but the present study goes further by investigating the transmission for very small tilt angles near 0\ifmmode^\circ\else\textdegree\fi{} with the small step sizes revealing distinct regions of behavior. The work performed here was conducted for two samples with different capillary diameters and pore densities: sample 1 with 100-nm diameter capillaries in a foil of 12-\textmu{}m thickness and a pore density of $5\ifmmode\times\else\texttimes\fi{}{10}^{8}/{\mathrm{cm}}^{2}$, and sample 2 with 200-nm diameter capillaries with the same foil thickness and a pore density of $5\ifmmode\times\else\texttimes\fi{}{10}^{7}/{\mathrm{cm}}^{2}$. Two distinct regions of transmission depending on the sample tilt angle for both samples corresponding to direct and guided electrons as well as the transition region between them were observed. The angular centers and widths of the transmission for each angle investigated were found and are discussed in terms of the tilt angle variation in the foil. For the widths, comparison with the inherent angular width of the electron spectrometer is made. Energy loss of electrons was studied from the centroids of the energy spectra with these energies corresponding to the peak centers of the angular profiles. The broadness of the energy distributions due to inelasticity was investigated from the full width at half maxima (in eV) of the spectra. The results for both samples agreed well despite the differences in capillary diameters and pore densities. The results are in partial agreement with the previous work performed for PET nanocapillaries by Das et al. [Phys. Rev. A 76, 042716 (2007)], but differences are also found.

SU‐E‐T‐230: Creating a Large Number of Focused Beams with Variable Patient Head Tilt to Improve Dose Fall‐Off for Brain Radiosurgery

Purpose:To develop a treatment delivery and planning strategy by increasing the number of beams to minimize dose to brain tissue surrounding a target, while maximizing dose coverage to the target.Methods:We analyzed 14 different treatment plans via Leksell PFX and 4C. For standardization, single tumor cases were chosen. Original treatment plans were compared with two optimized plans. The number of beams was increased in treatment plans by varying tilt angles of the patient head, while maintaining original isocenter and the beam positions in the x‐, y‐ and z‐axes, collimator size, and beam blocking. PFX optimized plans increased beam numbers with three pre‐set tilt angles, 70, 90, 110, and 4C optimized plans increased beam numbers with tilt angles increasing arbitrarily from range of 30 to 150 degrees. Optimized treatment plans were compared dosimetrically with original treatment plans.Results:Comparing total normal tissue isodose volumes between original and optimized plans, the low‐level percentage isodose volumes decreased in all plans. Despite the addition of multiple beams up to a factor of 25, beam‐on times for 1 tilt angle versus 3 or more tilt angles were comparable (<1 min.). In 64% (9/14) of the studied cases, the volume percentage decrease by >5%, with the highest value reaching 19%. The addition of more tilt angles correlates to a greater decrease in normal brain irradiated volume. Selectivity and coverage for original and optimized plans remained comparable.Conclusion:Adding large number of additional focused beams with variable patient head tilt shows improvement for dose fall‐off for brain radiosurgery. The study demonstrates technical feasibility of adding beams to decrease target volume

Temperature-Induced Switchable Adhesion using Nickel-Titanium-Polydimethylsiloxane Hybrid Surfaces.

A switchable dry adhesive based on a nickel–titanium (NiTi) shape-memory alloy with an adhesive silicone rubber surface has been developed. Although several studies investigate micropatterned, bioinspired adhesive surfaces, very few focus on reversible adhesion. The system here is based on the indentation-induced two-way shape-memory effect in NiTi alloys. NiTi is trained by mechanical deformation through indentation and grinding to elicit a temperature-induced switchable topography with protrusions at high temperature and a flat surface at low temperature. The trained surfaces are coated with either a smooth or a patterned adhesive polydimethylsiloxane (PDMS) layer, resulting in a temperature-induced switchable surface, used for dry adhesion. Adhesion tests show that the temperature-induced topographical change of the NiTi influences the adhesive performance of the hybrid system. For samples with a smooth PDMS layer the transition from flat to structured state reduces adhesion by 56%, and for samples with a micropatterned PDMS layer adhesion is switchable by nearly 100%. Both hybrid systems reveal strong reversibility related to the NiTi martensitic phase transformation, allowing repeated switching between an adhesive and a nonadhesive state. These effects have been discussed in terms of reversible changes in contact area and varying tilt angles of the pillars with respect to the substrate surface.

Optimum Tilt Angle at Tropical Region

: One of the important parameters that affect the performance of a solar collector is its tilt angle with the horizon. This is because of the variation of tilt angle changes the amount of solar radiation reaching the collector surface. Meanwhile, is the rule of thumb, which says that solar collector Equator facing position is the best, is valid for tropical region? Thus, it is required to determine the optimum tilt as for Equator facing and for Pole oriented collectors. In addition, the question that may arise: how many times is reasonable for adjusting collector tilt angle for a definite value of surface azimuth angle? A mathematical model was used for estimating the solar radiation on a tilted surface, and to determine the optimum tilt angle and orientation (surface azimuth angle) for the solar collector at any latitude. This model was applied for determining optimum tilt angle and orientation in the tropical zones, on a daily basis, as well as for a specific period. The optimum angle was computed by searching for the values for which the radiation on the collector surface is a maximum for a particular day or a specific period. The results reveal that changing the tilt angle 12 times in a year (i.e. using the monthly optimum tilt angle) maintains approximately the total amount of solar radiation near the maximum value that is found by changing the tilt angle daily to its optimum value. This achieves a yearly gain in solar radiation of 11% to 18% more than the case of a solar collector fixed on a horizontal surface.

Surface plasmon resonance on the surface: metal - liquid crystal layer

Surface plasmon resonance (SPR) is widely used in different types of optical detection schemes and for light manipulation at sub-wavelength scale. Usually Kretschmann configuration is used for effective SPR excitation. There are a lot of experimental and theoretical investigations about the influence of the dielectric, adjacent to the metal, on SPR. However, till now the influence on liquid crystal layer, adjacent to the metal, is not considered to our best knowledge. The purpose of the present paper is to cover this gap. We simulate the influence of thin layer of liquid crystal, adjacent to the metal, on the SPR characteristics. For this purpose Maxwell equations are numerically solved for layer structure: prism/gold/liquid crystal/air. The light reflection spectra are calculated for chiral structure of ferroelectric smectic C (SmC*) liquid crystal layer. The angular and wavelength response are considered. Special attention is paid to SPR excitation for variation of tilt angle and different angle of incident light. The influence of SPR of the pitch length and cell thickness is also considered.

An Algorithm for Determining Optimum Tilt Angle and Orientation for Solar Collectors

Proper installation, especially the tilt angle, directly affects the system’s output. Determination of the optimal tilt angle of a solar cell module depends on the solar radiation characteristics, season, and reflectivity in the local area. One of the important parameters that affect the performance of a solar collector is its tilt angle with the horizon. This is because of the variation of tilt angle changes the amount of solar radiation reaching the collector surface. A mathematical model is presented for determining the optimum tilt angle at different orientations (surface azimuth angle) for the solar collector, on a daily basis, as well as for a specific period such as monthly, seasonally and yearly basis. The optimum angle was computed by searching for the values for which the extraterrestrial solar radiation on the collector surface is a maximum for a particular day or a specific period. The results reveal that changing the tilt angle 12 times in a year (i.e. using the monthly optimum tilt angle) or even 4 times/year (i.e. using the seasonally optimum tilt angle) maintains approximately the total amount of solar radiation near the maximum value that is found by changing the tilt angle daily to its optimum value. This achieves a yearly gain in solar radiation of 5.5% at 0o latitude to 78% at 60o latitude more than the case of a solar collector fixed on a horizontal surface.

OPTIMUM YEARLY TILTED ANGLE OF PHOTOVOLTAIC CELL TO RECEIVE MAXIMUM SOLAR RADIATION IN SOUTHERN IRAQ CITIES

The performance of photovoltaic cell is affected by the value of its tilt angle with respect to horizontal plane, where the variation of tilt angle changes the amount of solar radiation permit to the photovoltaic cell surface. So that, the using of solar tracking system for photovoltaic cell will get the maximum solar radiation that permit to the surface of the cell at any time and day of the year, but the solar tracking systems have high operation and maintenance costs and are not always applicable. It is often convenient to set the solar collector at an optimum fixed tilt angle over a time of the year with less reduction in solar radiation received in the cell surface.This work is to find an optimum tilt angle of photovoltaic cell located in southern Iraqi cities Basrah city (latitude 30.30), Amarah city (31.55) and Nasiriyah (31). A mathematical models was used and programed by engineering equation solver EES to find an optimum tilt angle depending on the maximum solar radiation, the tilted angle varied with range from 0 to 90. The results showed that the optimum tilt angle for Basrah is 28, where for Amarah is 30 and for Nasiriyah is 29.

Displacement Parameter Inversion for a Novel Electromagnetic Underground Displacement Sensor

Underground displacement monitoring is an effective method to explore deep into rock and soil masses for execution of subsurface displacement measurements. It is not only an important means of geological hazards prediction and forecasting, but also a forefront, hot and sophisticated subject in current geological disaster monitoring. In previous research, the authors had designed a novel electromagnetic underground horizontal displacement sensor (called the H-type sensor) by combining basic electromagnetic induction principles with modern sensing techniques and established a mutual voltage measurement theoretical model called the Equation-based Equivalent Loop Approach (EELA). Based on that work, this paper presents an underground displacement inversion approach named “EELA forward modeling-approximate inversion method”. Combining the EELA forward simulation approach with the approximate optimization inversion theory, it can deduce the underground horizontal displacement through parameter inversion of the H-type sensor. Comprehensive and comparative studies have been conducted between the experimentally measured and theoretically inversed values of horizontal displacement under counterpart conditions. The results show when the measured horizontal displacements are in the 0–100 mm range, the horizontal displacement inversion discrepancy is generally tested to be less than 3 mm under varied tilt angles and initial axial distances conditions, which indicates that our proposed parameter inversion method can predict underground horizontal displacement measurements effectively and robustly for the H-type sensor and the technique is applicable for practical geo-engineering applications.

Thermal, Optical, and Dielectric Analysis of Hydrogen-Bonded Liquid Crystals Formed by Adipic and Alkyloxy Benzoic Acids

Intermolecular hydrogen-bonded homologous series comprising of eight liquid crystalline complexes are isolated and characterized. Double complimentary hydrogen bonds are formed between non-mesogen adipic acid (AA) and mesogenic p-n-alkyloxy benzoic acid (nBAO), the series is referred to as AA+nBAO. Hydrogen bond formation is evinced through Fourier transform infrared spectroscopy (FTIR) studies, while the mesogenic phases are identified by polarizing optical microscopic (POM) studies, which are further confirmed by differential scanning calorimetry (DSC). Phase diagram is constructed from the data of DSC and POM studies. The variation of tilt angle with temperature in smectic C phase is fitted to a power law and the exponent value (β) is found to be in agreement with Mean Field predicted value.

Spinning up the polymorphs of calcium carbonate

Controlling the growth of the polymorphs of calcium carbonate is important in understanding the changing environmental conditions in the oceans. Aragonite is the main polymorph in the inner shells of marine organisms, and can be readily converted to calcite, which is the most stable polymorph of calcium carbonate. Both of these polymorphs are significantly more stable than vaterite, which is the other naturally occurring polymorph of calcium carbonate, and this is reflected in its limited distribution in nature. We have investigated the effect of high shear forces on the phase behaviour of calcium carbonate using a vortex fluidic device (VFD), with experimental parameters varied to explore calcium carbonate mineralisation. Variation of tilt angle, rotation speed and temperature allow for control over the size, shape and phase of the resulting calcium carbonate.

Lipid-Mediated Polypeptide Interactions in Membranes: Case Study on the Synergism Between Linear Cationic Antimicrobial Peptides

Biophysical investigations, that aim to explain the antimicrobial activities of cationic linear peptides will be presented (1,2). In particular we aim to understand how some mixtures of these peptides exhibit synergistic activities. Therefore, the structure, topology and dynamics of PGLa and magainin 2 were investigated in oriented phospholipid bilayers using solid-state NMR in the presence or absence of the other peptide and as a function of the membrane lipid composition (2,3). Furthermore, fluorescence spectroscopy was used to investigate how the peptides interact with each other within the lipid bilayer environment.Whereas, magainin 2 exhibits stable in-planar alignments under all conditions investigated PGLa adopts a number of different membrane topologies with considerable tilt angle variations (2,3). Notably, the hydrophobic thickness modulates the alignment of PGLa (1). In equimolar mixtures of PGLa and magainin 2 the former adopts transmembrane orientations in DMPC when at the same time magainin 2 remains associated with the surface (1). In contrast in bilayers, which represents better the natural membrane composition (1-palmitoyl-2-oleoyl-phospholipids), both peptides adopt a surface oriented topology. Therefore, lipid-mediated interactions play a fundamental role in determining the topology of membrane peptides and proteins (3) and thereby potentially also the regulation of their activities. These results have important consequences for the mechanistic models explaining synergistic activities of the peptide mixtures and will be discussed in the context of unpublished data where membrane structure and interactions are correlated with biological activities. Furthermore, recent results obtained with DNP enhanced solid-state NMR spectroscopy of supported lipid bilayer samples using prototype equipment will be presented.

Idiopathic Cam Morphology Is Not Caused by Subclinical Slipped Capital Femoral Epiphysis: An MRI and CT Study.

Background:Cam impingement as a known sequelae of slipped capital femoral epiphysis (SCFE) has led to speculation that subclinical SCFEs may be the causative factor in idiopathic cam morphology; alternatively, others have implicated an abnormal extension of the growth plate as a causative factor.Hypothesis/Purpose:To investigate the growth plate tilt angle in 4 patient cohorts: normal patients, patients with idiopathic cam morphology (CamIP), patients with cam morphology secondary to known SCFE (CamSCFE), and patients with incidental findings of an asymptomatic cam (Camasymp).Study Design:Case-control study; Level of evidence, 3.Methods:A database of 192 computed tomography scans of abdomens/pelvises of patients (ages, 5-19 years) with no known orthopaedic issues, reformatted to neutral tilt, inclination, and rotation, were utilized for the normal cohort, the Camasymp cohort, and to create an age- and sex-matched control cohort. In addition, a retrospective review of all patients treated for femoroacetabular impingement (FAI) with preoperative advance imaging was conducted, and patients were separated to CamIP and CamSCFE cohorts. The alpha angle and tilt angle were measured on each hip. Statistical analysis was performed.Results:The mean tilt angle among the normal patients was 12.1°, with 1.9% of the variation in tilt angle being explained by age; each additional year of age decreased the tilt angle by 0.27° (P = .008). The tilt angle for the CamSCFE cohort (mean, 44.5°) was found to be significantly greater than both the CamIP cohort (mean, 5.9°; P < .001) and the control cohort (mean, 12.8°; P < .001). The tilt angle for the CamIP cohort was found to be significantly less than the control cohort (P = .003). The alpha angle and tilt angle were positively correlated in the CamIP cohort, but no correlation was found in the other cohorts. The mean tilt angle of the 18 hips in the Camasymp cohort was 13.9° ± 11.5° (range, –12° to 37°), with 12 hips (67%) in the tilt angle range of CamIP cohort and 6 in the tilt angle range of CamSCFE.Conclusion: The proximal femoral growth plate normally has a posterior tilt that becomes more anterior through maturation. Idiopathic cam morphology has a drastically different growth plate tilt angle than cam morphology secondary to SCFE, suggesting that a majority of idiopathic cam morphology is not the result of subclinical SCFEs.

Limitations in solar module azimuth and tilt angles in building integrated photovoltaics at low latitude tropical sites in Brazil

Photovoltaic (PV) generation depends directly on the amount of radiation received by solar modules at a given temperature, and annual irradiation varies according to site location and PV array position. In this paper, the limitations and the solar irradiation levels received by building surfaces in different positions (with azimuth and tilt angle variation) in capital cities in Brazil are shown, making use of the Brazilian global horizontal solar irradiation data provided by the SWERA (Solar and Wind Energy Resource Assessment) project. These data were processed to generate figures on the irradiation at various PV module orientations and slopes for each city, which show the relative radiation levels received on specific azimuth and tilt angles in relation to the ideal position. Results were validated using four real and operating PV systems. In general, variations in azimuth or slope did not cause large annual irradiation losses up to around 20° tilt angles. This shows to PV system planners that under these fairly flexible conditions it is possible to install PV on any orientation, keeping high levels of annual irradiation, and that limitations in orientation and tilt can be relatively low. It also allows a quick analysis of PV retrofit in building-applied photovoltaics (BAPV), when seeking the best building surfaces to incorporate PV.

Theoretical Analysis of Interferometer Wave Front Tilt and Fringe Radiant Flux on a Rectangular Photodetector

This paper is a theoretical analysis of mirror tilt in a Michelson interferometer and its effect on the radiant flux over the active area of a rectangular photodetector or image sensor pixel. It is relevant to sensor applications using homodyne interferometry where these opto-electronic devices are employed for partial fringe counting. Formulas are derived for radiant flux across the detector for variable location within the fringe pattern and with varying wave front angle. The results indicate that the flux is a damped sine function of the wave front angle, with a decay constant of the ratio of wavelength to detector width. The modulation amplitude of the dynamic fringe pattern reduces to zero at wave front angles that are an integer multiple of this ratio and the results show that the polarity of the radiant flux changes exclusively at these multiples. Varying tilt angle causes radiant flux oscillations under an envelope curve, the frequency of which is dependent on the location of the detector with the fringe pattern. It is also shown that a fringe count of zero can be obtained for specific photodetector locations and wave front angles where the combined effect of fringe contraction and fringe tilt can have equal and opposite effects. Fringe tilt as a result of a wave front angle of 0.05° can introduce a phase measurement difference of 16° between a photodetector/pixel located 20 mm and one located 100 mm from the optical origin.

Identification and target strength of orange roughy (Hoplostethus atlanticus) measured in situ

It is often assumed that in situ target strength (TS) measurements from dispersed fish are representative of the surveyed schooling fish. For in situ TS measurements of orange roughy in deep water, it has been difficult to validate the target species, individual lengths, and tilt angles and how representative these are of schooling fish. These problems have been addressed by attaching an acoustic optical system (AOS) to a trawl net. The AOS enables in situ measurements of TS and volume backscattering strength (Sv) at 38 and 120 kHz with optical verification of species and stereo camera measurements of fish length and tilt angle. TS estimates believed representative of the schooling population were derived by (1) weighting the frequency-dependent TS values by the Sv frequency difference distribution of orange roughy schools and (2) weighting the in situ TS measurements with an assumed tilt angle distribution. The 120-kHz TS estimates were less sensitive to variations in frequency difference and tilt angle, suggesting that this frequency may be better for biomass estimates than 38 kHz, the traditional survey frequency. Computations performed with an anatomically detailed scattering model agree with measurements of TS at both frequencies over a range of tilt angles.

Techno-economic feasibility study of autonomous hybrid wind/PV/battery power system for a household in Urumqi, China

In this paper, based on renewable energy resources and load data research, a techno-economic feasibility study of an autonomous hybrid wind/photovoltaics (PV)/battery power system for a household in Urumqi, China, has been form carried out using Hybrid Optimization Model for Electric Renewables (HOMER) simulation software. The effects of ambient temperature, the variation of load and PV module tilt angles are considered in this simulation. The hybrid wind/PV/battery system with 5 kW of PV arrays (72% solar energy penetration), one wind turbine of 2.5 kW (28% wind energy penetration), 8 unit batteries each of 6.94 kWh and 5 kW sized power converters comprises an optimal power system for the household; it reduces the total net present cost (NPC) about 9% and 11% compared with PV/battery and wind/battery power systems, which has a similar consequence for the levelized cost of energy (COE). The economical, sensitivity and PV module tilt angle analyses of the proposed hybrid wind/PV/battery power system are discussed in this paper.