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This work studied the performance improvement of a two-axis solar tracking system by using flat-mirror reflectors. The two- and four-sided flat-mirror reflectors were set on the solar panel with angles of 90°, 120°, and 150° between the panel and flat-mirror reflectors. The highest efficiency, electrical power, and current were observed for four-sided flat mirrors at the angle of 120°, followed by two-sided flat mirrors at the angle of 120°, two-sided flat mirrors at the angle of 150°, two-sided flat mirrors at the angle of 90°, four-sided flat mirrors at the angle of 150°, and four-sided flat mirrors at the angle of 90°, respectively, because when the four-sided flat mirrors were mounted at a suitable degree of 120°, this improved the collected irradiance. At 90°, the four-sided flat mirrors blocked more solar rays than the two-sided ones. At 150°, the angle was too big for the solar ray to be reflected to the solar panel. The results indicated that the performance of the solar tracking system (efficiency, electrical power, and current) was affected by the number and angle of flat mirrors. The results of this study can be applied for the efficient performance of a novel solar tracking system design. This will be beneficial for the use of solar energy.

In this work a Solar Thermal Generator is analysed from an energy point of view. It is a dish collector that is part of a concentrating solar grid system. The analysed plant is used for the generation of low enthalpy thermal energy as an integration to the hot water production plant for some student residences of the University of Calabria (Italy). A thermal model is developed that simulates the behaviour of the plant with the aim of analysing its performance and optimizing the design of its fundamental parts from an energy point of view. The optical model of the solar collector is carried out for a particular external condition. The emissive characteristics of the absorber is determined with the use of a thermal imaging camera. To identify the main parameters that affect the functioning and the thermal balance of the capturing system, a thermo-fluid dynamic analysis is performed. The results show which are the main causes of loss. It is possible to understand the weight of each factor in the energy balance. [ABSTRACT FROM AUTHOR]

Among the new technologies for the exploitation of the solar source, double-sided hotovoltaic panels represent a valid high efficiency solution. These are latest generation photovoltaic panels that allow you to capture solar radiation even from the back and to obtain a greater production of electricity compared to traditional single sided panels. The performance of the panel is higher, with the consequent possibility of educing the installation surface. The paper defines a calculation model to analyse performances of a double-sided photovoltaic field, for both type of orientation N-S and E-W, in order to assess the effective increase in performance compared to a traditional system. Panels are equipped with a single-axis solar tracker, which changes their inclination so that they can have the best exposure to solar radiation. The study also focuses on the optimal tracking methodology, in order to reduce the losses caused by shading. The applied technique is that of "backtracking". We have seen that backtracking is not useful for bifacial panels, but only for mono-facial. In the work, a parametric analysis is also conducted to evaluate the increase in efficiency due to distance between rows of panels. [ABSTRACT FROM AUTHOR]

We report a simple technique for the realization of fiber-based Fabry-Pérot microcavities with large Q/V values as well as high cavity-to-fiber coupling efficiencies. The open microcavity we demonstrate consists of a flat mirror and a concave mirror on the tip of a single mode optical fiber. Combining hydrofluoric acid chemical wet etching with CO2 laser reflow, we obtain a fiber-tip atomically smooth concave surface with a diameter of 4.7 μm determined by the fiber core size. The concave surface with a spherical profile is automatically aligned with the fiber core, which enables high cavity-to-fiber power coupling efficiency (higher than 90%) with an optimal fiber-tip mirror's radius of curvature based on numerical simulation results. After distributed-Bragg-reflector coating, we have realized a wavelength-tunable open microcavity with a quality factor Q exceeding 1000 and a mode volume V of 13.6 μm3, and laser emission is demonstrated from this microcavity. [ABSTRACT FROM AUTHOR]

The objective of this paper is to investigate thermal efficiency enhancement methods in a linear Fresnel reflector (LFR) with evacuated tube receiver. The primary reflectors of the collector are flat mirrors of 27 m2 total net aperture, while the secondary reflector has a parabolic shape. The working fluid is Syltherm 800, and the analysis is performed for temperatures up to 650 K. The use of nanofluids and internal fins is the investigated thermal enhancement methods in the receiver of the LFR. The examined nanofluid is Syltherm/CuO for concentrations 2, 4 and 6%, while the examined internal fins are 8 longitudinal fins which are symmetrically located in the absorber. The LFR is examined using nanofluids and pure thermal oil in smooth or finned absorber. According to the final results, the maximum thermal efficiency enhancement is up to 1% and it is greater for higher operating temperature levels. The use of internal fins is better enhancement method compared to the use of nanofluids, while the combination of these two techniques leads to the highest possible performance. For the inlet temperature of 600 K with 200 L min−1 flow rate, the thermal efficiency enhancement with 4% nanofluid and finned absorber is found 0.82%, while it is found 0.61 and 0.28% with finned absorber with pure oil and 4% nanofluid with smooth absorber, respectively. [ABSTRACT FROM AUTHOR]

Photovoltaic (PV) concentrators use lenses or mirrors to concentrate sunlight onto PV cells. This allows for a reduction in the cell area and then significantly reduces in the cost of electricity generated by replacing expensive PV converter area with less expensive optical material. In this paper, an experimental PV low-concentration systems and two photovoltaic concentrators systems were built, the first system consists of a lens which will concentrate the light on a photovoltaic cell; various characteristics of the solar cell practically obtained for various enlightened surfaces Si correspond to the various rates of concentration X. The second experiment was carried out with commercially available PV module, based on reflector mirrors; the incident radiation is concentrated on a PV panel by means of a set of flat mirrors. A concentration X depends on two variables: the slope angle α and the reflectors length C. A comparative electrical and thermal study of PVG and the CPV is presented (with and without concentration). [ABSTRACT FROM AUTHOR]

An optical test method of the surface shape for very thin flat mirrors is presented and discussed. The effect of gravity on the mirror shape is greatly reduced by floating the mirror on water while the surface is measured using a Zygo interferometer. The floating mirror is supported by the buoyant force and surface tension. Mechanical analysis and error analysis show that the tested flat mirror can be considered as a rim supported mirror with a reduced gravity. The surface error caused by the rim constraint can be rather small because of the reduced effective gravity. The surface error of a flat mirror which is Ф102 mm, 0.6 mm thick was tested using this method. The results were compared to the method successfully used for the Hinode project. The Hinode method supports the mirror at three points and measures the surface for both the mirror facing up and facing down. The average of the face up and face down measurements yields the zero gravity shape. The test results including the surface error and the fringe of the surface shape by these two methods were in good agreement. Compared to the Hinode method, the method can be carried on before the mirror’s coating and can to be employed during the polishing process. [ABSTRACT FROM AUTHOR]

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Today restoring ancient 'camera obscura sundials' by drilling holes in building façades appears as an overly intrusive intervention in historical architecture. For this reason, our study proposes an innovative, low-cost gnomonic instrument, capable of adapting to any type of relationship between the façade where the original gnomonic hole was located) and the sundial on the floor. The tool that we have designed allows incoming sunlight to be caught by a reflection system of flat mirrors, appropriately tilted, thus producing a solar ray that exits the instrument with a different inclination. We created new angular relationships between the gnomonic hole and the astronomic data engraved along the sundial in two case studies of historic sundials that are now inactive and abandoned. The research was conducted weaving astronomy and gnomonics with geometry and mathematics, to create a 3D model to verify, plan and execute the restoration of historic sundials. [ABSTRACT FROM AUTHOR]

An improved QEPAS (quartz enhanced photo-acoustic spectroscopy) system based on an optical structure comprising miniaturized collimator and flat mirror is proposed. The beam diameter of the miniaturized collimator is designed less than 0.2 mm in a 20 mm working distance. Experiments are set up to compare the beam quality and photo-acoustic performance of three optical structures (this one, fiber lead mode and conventional focus mode). By virtue of the micro-resonator tubes and flat mirror, the new proposed structure achieves a SNR of 260 for a 3000 ppmv water vapor sample, which is much better than 183 for the fiber lead mode and 193 for the conventional focus mode respectively. This test is achieved by using the same self-designed circuit with the same parameters. The proposed optical structure is simpler and easier for optical alignment, and provides an alternative way in improving and simplifying the QEPAS system for industrial applications. [ABSTRACT FROM AUTHOR]

This paper addresses the problem of the mathematical design of a Linear Fresnel Reflector, specifically the design of a reflector concentrator with flat mirrors and a single absorber tube. The mathematical aspects of the design, i.e., the number, width and position of the primary mirrors and the height, length and relative position of the single absorber tube, are analysed. The optimization of the relative position with respect to the primary reflectors and the size of the single absorber tube are both addressed, further analysing up to 12 different configurations. To do so, both the frontal and lateral view of the structure are taken into account. The lateral optical performance factor analysed here, has been overlooked until now, as it may be insignificant in large-scale concentrators. It is shown in this paper that it is a key aspect in medium- and small-scale concentrators, the most common in applications in the Household Sector like, for example, micro-cogeneration. Finally, a number of numerical simulations performed in a custom-designed program compiled using Mathematica® is presented. At the time of this writing, a prototype is being built at CIFP in La Felguera, Asturias, Spain. [ABSTRACT FROM AUTHOR]

Low cost, two axis tracking solar dish with flat mirror system׳s (Solarux CSP) design and its advantages are described in this paper. System is based on the Concentrating Solar Power (CSP) technology. Heat energy and electricity are produced using oil and sunlight. In design stage, cost of production, constructability, automation, safety, cleaning and required energy that is required for the system have been taken into account. In this paper, it has been focusing on air-conditioning, heating, and producing electricity by using Solarux CSP. The aim of this invention is to use planar mirrors instead of parabolic mirrors in order to recuce cost and design a system that can be manufactured easily, can be constructed on every kind of terrain (rocky, plain etc.) and can be used by third world countries. For this purpose, for the development and design of solar flat system Solid Works 2012 has been used and the results are discussed and shown briefly. [ABSTRACT FROM AUTHOR]

Increasing the concentration ratio of parabolic troughs is one of the challenges to make this technology economically competitive against fossil fuels. Parabolic troughs with large concentration ratios face several problems such as difficulty capturing all the solar direct radiation and structural issues associated with thermal expansions and wind resistance amongst others. For larger mirrors it may be necessary to use a bigger absorber in order to capture all the radiation, thus increasing the thermal losses. A second stage reflector helps to increase the concentration ratio without increasing the primary mirror size. In this work, a theoretical analysis of a parabolic trough with a secondary flat reflector is developed and ray tracing is conducted in order to validate the equations obtained. A flat reflector will have a minimal economic impact in the cost of a parabolic trough and it allows larger concentration ratios for identical primary mirror areas compared to a standard parabolic trough. Increases of concentration ratio up to 80% are observed when a secondary flat reflector is inserted in a commercial system, while the shadow area introduced in the primary mirror is usually less than 15% of the primary mirror area. The increase in pumping power is offset by the increase in system efficiency. [ABSTRACT FROM AUTHOR]

We studied adults' understanding of the relationship between objects and their reflections. Two studies investigated whether adults performed in a similar way when asked to predict the movement of a reflection in a flat mirror based on the movement of the corresponding object or, vice versa, predict the movement of the material object based on the movement of its reflection. We used simple movements in the experiments: movements in a straight line at various angles with respect to the mirror. Despite the simplicity of the task, some of the participants made incorrect predictions in a percentage of cases ranging from 0% to 54%, depending on the angle. Asymmetries between the two directions of prediction emerged, in particular in terms of types of error. Results confirmed a cognitive difference between deriving the reflected (virtual) world from the “real” (material) world and vice versa. In particular the expectation that something will be opposite in a mirror is more salient when people imagine how a reflection will be with respect to the material world rather than when they imagine how the material world will be with respect to a reflection. [ABSTRACT FROM AUTHOR]

This paper presents the first investigation of the effect of lithium coating on the optics of Doppler backscattering. A liquid lithium limiter has been applied in the Experimental Advanced Superconducting Tokamak (EAST), and a Doppler backscattering has been installed in the EAST. A parabolic mirror and a flat mirror located in the vacuum vessel are polluted by lithium. An identical optical system of the Doppler backscattering is set up in laboratory. The power distributions of the emission beam after the two mirrors with and without lithium coating (cleaned before and after), are measured at three different distances under four incident frequencies. The results demonstrate that the influence of the lithium coating on the power distributions are very slight, and the Doppler backscattering can work normally under the dosage of lithium during the 2014 EAST campaign. [ABSTRACT FROM AUTHOR]

Utilizing fins with horseshoe shape connected to bottom of tube and install of perforated tape at center of pipe, leading to higher level of productivity in current article. Furthermore, the mixing rate will hopefully be improved with dispersing hybrid nano-powders, because the thermal features of operate fluid will be intensified. The solar system includes twenty mirrors which concentrate the solar rays to the region of absorber pipe. The distribution of assimilating heat flux was derived via SolTrace and outputs showed that the bottom point absorbs the greatest rays, which is why the horseshoe fins were attached to bottom of pipe. Assessment of grid and accuracy of model have been presented and good accommodation with empirical data made it clear that such selected techniques in modeling were suitable for turbulent flow. The scrutinized variable parameters of current work are: Angle of horseshoe fins (θ = 0°, 30°, 45°); Pitch ratio (PR (=P/D) = 3.2, 4); Inlet flow rate (Q = 13, 19 Lit/min); Fraction of additives (φ = 0, 0.02). Not only the patterns of hybrid nanofluid in forms of contours but also substantial functions such as pumping power (W •) and thermal efficiency (η t h ) were evaluated in outputs. Due to elevate of heat absorption with dispersing hybrid nano-powders, η t h will be enhanced about 0.01% when θ = 0°, Q = 19, PR = 3.2. When Q = 13, with augment of θ, convective coefficient reduces around 12.02% and pumping power declines around 37.61%. As PR declines, the mixing of hybrid nanofluid improves and convective factor elevates around 6.43% while such change makes pumping power to augment about 30.67%. As flow rate of fluid at inlet increases, the thermal performance and convective factor augment around 0.18% and 31.98% but with higher level of pumping power about 195.41%. • Perforated tape and horseshoe shaped fins were combined in current paper. • Thermal features of operate fluid were intensified by using hybrid nanoparticles. • With augment of θ, convective coefficient reduces around 12.02%. • As PR declines, the mixing of hybrid nanofluid improves around 6.43%. • As Q increases, the thermal performance augments around 0.18%. [ABSTRACT FROM AUTHOR]

In this paper, a small non-imaging focusing heliostat is presented, and an analytical model for assessing its performance is described. The main novelty of the system lies in the tracking mechanism and the mirror mount, which are based on off-the-shelf components and allow a good trade-off between accuracy and costs. The concentrator mirrors are moved by this two-axis tracking machinery to reflect the sun's rays onto a fixed target, the dimensions of which can be varied to suit the user's needs. A prototype plant to be located in central Italy was designed and simulated with a ray-tracing algorithm, and it comprises 90 heliostats for a total reflective area of 7.5 m2. The reflected solar rays are tracked taking the mechanical positioning errors of the tracking system into account. The total flux of radiation energy hitting the target was determined, and intensity distribution maps were drawn. Simulations showed that the system's optical efficiency can exceed 90% in summer, despite the tracking errors, mainly because of the smaller distance between the heliostats and the receiver. The solar concentration ratio over a receiver of 250 mm in diameter reached 80 suns with a very good uniformity. Over a 400-mm receiver, the concentrated radiation was less uniform, and the solar concentration ratio reached 50 suns, with a higher optical efficiency and collected solar radiation. The present concentration ratio is still suitable for many applications ranging from the electric power production, industrial process heat, and solar cooling. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Within classical optics, one may add microscopic "roughness" to a macroscopically flat mirror so that parallel rays of a given angle are reflected at different outgoing angles. Taking the limit (as the roughness becomes increasingly microscopic) one obtains a flat surface that reflects randomly, i.e., the transition from incoming to outgoing ray is described by a probability kernel (whose form depends on the nature of the microscopic roughness). We consider two-dimensional optics (a.k.a. billiards) and show that every random reflector on a line that satisfies a necessary measure-preservation condition (well established in the theory of billiards) can be approximated by deterministic reflectors in this way. [ABSTRACT FROM AUTHOR]

Ultraprecise aspheric mirrors that offer nanofocusing and high coherence are indispensable for developing third-generation synchrotron radiation and X-ray free-electron laser sources. In industry, the extreme ultraviolet (wavelength: 13.5 nm) lithography used for high-accuracy aspheric mirrors is a promising technology for fabricating semiconductor devices. In addition, ultraprecise mirrors with a radius of curvature of less than 10 mm are needed in many digital video instruments. We developed a new type of nanoprofiler that traces the normal vector of a mirror's surface. The principle of our measuring method is that the normal vector at each point on the surface is determined by making the incident light beam on the mirror surface and the reflected beam at that point coincide, using two sets of two pairs of goniometers and one linear stage. From the acquired normal vectors and their coordinates, the three-dimensional shape is calculated by a reconstruction algorithm. The characteristics of the measuring method are as follows: the profiler uses the straightness of laser light without using a reference surface. Surfaces of any shape can be measured, and there is no limit on the aperture size. We calibrated this nanoprofiler by considering the system error resulting from the assembly error and encoder scale error, and evaluated the performance at the nanometer scale. We suppressed the effect of random errors by maintaining the temperature in a constant-temperature room within ±0.01°C. We measured a concave spherical mirror with a radius of curvature of 400 mm and a flat mirror and compared the results with those obtained using a Fizeau interferometer. The profiles of the mirrors were consistent within the range of system errors. [ABSTRACT FROM AUTHOR]

This paper initially presents a demonstration of the ability of 17th century artists to achieve self-portrait projections using concave and flat mirrors, and subsequently develops a case for the likelihood of this technique being employed by Rembrandt van Rijn and other old master painters. [ABSTRACT FROM AUTHOR]