Efficient Solar Concentrators Research Articles

Retraction Note: Luminescent solar concentrator efficiency enhanced via nearly lossless propagation pathways

Retraction Note: Luminescent solar concentrator efficiency enhanced via nearly lossless propagation pathways

Graphical Interface in MATLAB for design and analysis of reflectors for lighting systems or solar collectors on parabolic surfaces

This project introduces the successful development of a MATLAB graphical interface for the design and analysis of reflectors and solar concentrators on parabolic surfaces. The integration of spline techniques for precise modeling of these surfaces has been implemented, along with the capability to generate STL files for 3D printing. The interface not only enables detailed and adaptable design of reflectors but also includes an advanced simulator for projecting incident rays and analyzing their reflection on the parabolic surface, focusing specifically on the focal point location. This has led to a significant increase in the efficiency of solar concentrators and lighting systems by enabling the precise placement of absorbers to maximize energy transfer. The obtained results confirm the initial hypothesis, demonstrating that the interface enhances the precision and efficiency in the design of these systems, thereby offering a valuable tool in both educational and professional realms in the fields of solar energy and lighting.

A Study on the Optical Efficiency of Solar Concentrators Based on Ray Tracing Method

A Study on the Optical Efficiency of Solar Concentrators Based on Ray Tracing Method

RETRACTED ARTICLE: Luminescent solar concentrator efficiency enhanced via nearly lossless propagation pathways

Luminescent solar concentrators (LSCs) have the potential to serve as energy-harvesting windows in buildings. Although recent advances in nanotechnology have led to the emergence of novel fluorophores such as quantum dots, perovskites and others, the commercialization of such functional glass remains immature due to an insufficient power conversion efficiency. In other words, improvements in fluorophores alone cannot fully maximize the potential of LSCs. Here we introduce a new laminated type of LSC structure where a patterned low-refractive-index medium acts as an optical ‘guard rail’, providing a practically non-decaying path for guiding photons. We also propose the design rules regarding the dimensions of LSCs and the spectral characteristics of fluorophores. Once these rules were applied, we achieved record-high LSC performance. The measured external quantum efficiencies at 450 nm are 45% for a 100 cm2 area and 32% for the LSC with an edge aspect ratio of 71. The device efficiency is 7.6%, the highest value ever reported, to the best of our knowledge. These findings may have industrial implications and could accelerate the commercialization of LSCs.

Dust InSMS: Intelligent soiling measurement system for dust detection on solar mirrors using computer vision methods

The dust accumulation strongly impacts the optical efficiency of solar concentrators, in particular the reflectivity of solar mirrors. Therefore, reducing the impact of reflectivity losses due to soiling and optimizing cleaning strategy are key factors. In this paper, the impact of dust accumulation on the reflectivity parameter of Fresnel mirrors is studied at the GEP research platform during the dry period. Based on the collected data, a new system for dust detection is proposed based on the classification approach using the convolutional neural networks and image processing algorithms in which no similar work is presented in the literature that uses the same approach to quantify the soiling phenomenon on CSP mirrors. The test loss and accuracy obtained by the proposed model are respectively 0.28 and 0.96. The outdoor validation results obtained so far suggest that the Dust InSMS concept and method could be a promising efficient and low-cost sensor. As the proposed system performs the GPS coordinates for each measurement, an optimal cleaning scenario is developed based on genetic algorithms to optimize the cleaning scenario and to come up with the shortest cleaning path.

The Use of a Parabolic Solar Concentrator in Nasiriya city, Iraq

In this paper, it presents a detailed analysis of the use of the parabolic solar concentrator in heating and boiling water, as the parabolic solar concentrator was manufactured with a diameter of (96 cm), the focal length of the dish is (72 cm), and the focus depth of the dish is (8 cm). It was made using a parabolic dish with a diameter of (96 cm) and using glossy aluminum foil as a reflective sun ray after being cut into strips 10 cm wide and glued to the inner surface of the dish. Metal tin cans with two capacities (1L and 2L) were used as the absorbent receiver. Experiments were conducted to boil water from the roof of the house in Nassiriya city. The study calculated the optical efficiency of the equivalent solar concentrator, the amount of heat output as a result of the fall of concentrated solar radiation on the receiver, the amount of useful heat gained, the thermal losses from the receiver, the collector efficiency. Many tests were conducted in Nassiriya city weather conditions.
 The results of the experiments showed that the efficiency of the solar center mainly depends on the diameter of the concentrator dish, the quality of the reflector used, the time of heating the water, and the closing to midday. While the high ambient air velocity leads to a decrease in the receiver temperature by increasing the heat loses to ambient air by convection, thus reducing the efficiency of the solar concentrator; as well as the accuracy of directing the dish towards the sun and determining the focus accurately also affects the efficiency of the solar concentrator.

Enhanced luminescent solar concentrator efficiency by Foster resonance energy transfer in a tunable six‐dye absorber

Enhanced luminescent solar concentrator efficiency by Foster resonance energy transfer in a tunable six‐dye absorber

Geometry effects on luminescence solar concentrator efficiency: analytical treatment.

Luminescence solar concentrators act as semitransparent photovoltaic cells of interest for modern urban environments. Here, their efficiencies were analytically derived for different regular unit shapes as simple, integral-free expressions. This allowed analysis of the shape and size effect on the device performance. All regular shapes appear to have a similar efficiency as revealed by optical path distribution formulas, despite differences in the perimeter length. Rectangles of the same area feature higher efficiency due to reduced average optical path. It comes with the cost of a longer perimeter, and the relation between these two is provided. An explicit formula for the critical size of an LSC unit, above which its inner part becomes inactive, has been obtained. For square geometry with matrix absorption coefficient α this critical size is ∼2.7/α, corresponding to 70-90 cm for common polymer materials. Obtained results can be used for treatment of individual units as well as for analysis of tiling for large areas.

Improving Luminescent Solar Concentrator Efficiency by Mixing Acriflavine and Eosin Y Organic Dyes

Improving Luminescent Solar Concentrator Efficiency by Mixing Acriflavine and Eosin Y Organic Dyes

Characterization of Double-Doped Polymer Optical Fibers as Luminescent Solar Concentrators

This work reports on a diameter dependence analysis of the performance as luminescent solar concentrators of three self-fabricated polymer optical fibers (POFs) doped with a hybrid combination of dopants. The works carried out include the design and self-fabrication of the different diameter fibers; an experimental analysis of the output power, of the output irradiance and of the fluorescent fiber solar concentrator efficiency; a comparison of the experimental results with a theoretical model; a study of the performance of all the fibers under different simulated lighting conditions; and a calculation of the active fiber length of each of the samples, all of them as a function of the fiber core diameter. To the best of our knowledge, this paper reports the first analysis of the influence of the POF diameter for luminescent solar concentration applications. The results obtained offer a general perspective on the optimal design of solar energy concentrating systems based on doped POFs and pave the way for the implementation of cost-effective solar energy concentrating devices.

Holistic Optimisation of Solar-assisted Multiple Effect Evaporators (MEE)

The effects of heat transfer performance of systems can be studied in combination with thermodynamic performance. The design solution of maximizing heat transfer always leads to increased entropy generation else if minimizing entropy was aimed then heat transfer got minimized. Hence there is need for holistic optimization. This paper attempts to merge the two competing criteria’s - (i) heat transfer and (ii) the thermodynamic performance of a solar assisted multiple effect evaporator system and optimize study parameters for its energy efficient operation. Solar assisted multiple effect evaporators use steam as source of energy to evaporate wastewater.The idea of amalgamating these two factors is to observe how much reduction in the performance of one factor will improve the performance of the other. This study couples the two criteria, which has been dealt with separately, to arrive at the parameters of interest which must be fine-tuned for ensuring system performance.Mass flow rate of steam and wastewater appeared to chiefly influence heat transfer and entropy generation of the system, negligible influence was observed on changing the concentration of the waste water or optical efficiency of the solar concentrator in single legged analysis. However through this holistic optimization study, it was found that variations in Prandtl number, i.e., the concentration of the waste water and optical efficiency of solar concentrator drastically shift the optimization balance of entropy generation and heat transfer rate.

Visible to NIR downconversion process in Tb3+-Yb3+ codoped silica-hafnia glass and glass-ceramic sol-gel waveguides for solar cells

The efficiency of photovoltaic solar cells is strongly related to the spectral absorption and photo-conversion properties of the cell's active material, which does not exploit the whole broadband solar spectrum. This mismatch between the spectrum of the solar light and the wavelength dependent cell's response can be partially overcome by using luminescent conversion layers in front or in the back of the solar cell. In this paper, the investigation of Tb3+-Yb3+ co-doped SiO2-HfO2 glass and glass-ceramic waveguides is presented. Due to a down-conversion process based on cooperative energy transfer between one Tb3+ ion and two Yb3+ ions, a blue photon at 488nm can be divided in two NIR photons at 980nm. Films with different molar concentrations of rare earths, up to a total amount of [Tb + Yb] = 15%, were prepared by a sol-gel route, using dip-coating deposition on SiO2 substrates. For all the films, the molar ratio [Yb]/[Tb] was taken equal to 4. The comparison of the energy-transfer efficiency between Tb3+ and Yb3+ ions in the glass and in the glass-ceramic materials demonstrated the higher performance of the glass-ceramic, with a maximum quantum transfer efficiency of 179% for the highest rare earth doping concentration. Moreover, experimental results and comparison with proper rate equations modelling showed a linear dependence of the photoluminescence emission intensity for the Yb3+ ions 2F5/2 → 2F7/2 transition at 980nm on the excitation power, indicating a direct transfer process from Tb3+ to Yb3+ ions. The reported waveguides could find applications not only as downconverting filters in transmission but also as efficient solar concentrators in the near-IR spectral region.

On the ability of Förster resonance energy transfer to enhance luminescent solar concentrator efficiency

Developing means to reduce the cost of solar energy is vital to curb our carbon footprint over the upcoming decades. A luminescent solar concentrator (LSC) is a potential solution as it provides light concentration without any tracking device and can be readily integrated into the built environment. In this study we report on an advanced LSC design that employs quantum dots as absorption fluorophores and organic dye molecules as emission fluorophores. By linking the two types of fluorophores to each other, energy is transferred efficiently via Förster resonance energy transfer (FRET) from the quantum dot to the dye molecule. This novel method makes use of the quantum dot's spectrally wide absorption profile and the higher quantum yield of the dye. We show that our design can overcome the losses normally incurred due to a low quantum yield emitter by transferring the absorbed energy to a linked fluorophore with a higher quantum yield. Our experimental measurements show FRET can enhance the optical efficiency of a LSC by at least 24.7%. The maximum theoretical efficiency has been investigated by ray-tracing and has been found to be 75.1%; this represents a relative improvement of even 215.5% compared to a LSC doped with quantum dots only (23.8%), showing the great potential of our concept. Our design will initiate interest in fluorophores which have not been considered for LSC applications thus far because of their low quantum yield or small Stokes shift.

Enhanced green and orange photoluminescence of nanostructured CdS in glass nanocomposites by energy transfer From Ho3+ and Eu3+ ions

We report enhanced photoluminescence (PL) of both band edge and trap state emissions in Ho3+ or Eu3+ ion doped CdS (II-VI semiconductor) nanoparticles (NPs) containing glass nanocomposites. These glass nanocomposites were synthesized by the conventional melt-quench technique. The sizes of CdS NPs are found to increase from 5–15 nm to 40–80 nm with the increase in thermal treatment. Band edge emission (green emission, peak around 495 nm) of CdS NPs is controlled by their size and enhanced about three to nine-fold by Ho3+ ions on excitation at 446 nm by a diode laser. Under the same excitation, twelve to fifty-fold enhanced trap state emission (orange and red emissions about 550–900 nm) of CdS NPs is obtained by Eu3+-doping compared to undoped CdS NPs containing glass nanocomposites. The predominant mechanism of PL enhancement is the energy transfer from rare earth ions to CdS NPs. Enhanced PL of these nanocomposites enables their applications in efficient solar concentrators, green and red light emitting component for white light emission devices.

Development of a solar concentrator with tracking system

Abstract. Solar Energy has been, since the beginning of human civilization, a source of energy that raised considerable interest, and the technology used for their exploitation has developed constantly. Due to the energetic problems which society has been facing, the development of technologies to increase the efficiency of solar systems is of paramount importance. The solar concentration is a technology that has been used for many years by the scientist, because this system enables the concentration of solar energy in a focus, which allows a significant increase in energy intensity. The receiver, placed at the focus of the concentrator, can use the stored energy to produce electrical energy through Stirling engine, for example, or to produce thermal energy by heating a fluid that can be used in a thermal cycle. The efficiency of solar concentrators can be improved with the addition of a dual axis solar tracker system which allows a significant increase in the amount of stored energy. In response to the aforementioned, this paper presents the design and construction of a solar dish concentrator with tracking system at low cost, the optical and thermal modelling of this system and a performance analysis through experimental tests. The experimental validation allows to conclude that the application of a tracking system to the concentrator is very important since a minimum delay of the solar radiation leads to important losses of system efficiency. On the other hand, it is found that the external factors can affect the final results which include the optical and geometrical properties of the collector, the absorptivity and the position of the receiver as well as the weather conditions (essentially the wind speed and clouds). Thus, the paper aims to present the benefits of this technology in a world whose the consumption of energy by fossil fuels is a real problem that society needs to face.

Enhancing the efficiency of solar concentrators by controlled optical aberrations: Method and photovoltaic application

Abstract We present a general method, based on controlled static aberrations induced in the reflectors, to boost receiver performances in solar concentrators. Imaging mirrors coupled with dense arrays suffer from severe performance degradation since the solar irradiance distribution is bell-shaped: mismatch losses occur in particular when the cells are series connected. The method consists in computing static deformations of the reflecting surfaces that can produce, for an adopted concentration ratio, a light spot matching the receiver features better than conventional reflectors. The surfaces and the deformations have been analytically described employing the Zernike polynomials formalism. The concept here described can be applied to a variety of optical configurations and collecting areas. As an example, we extensively investigated a dense array photovoltaic concentrator, dimensioned for a nominal power of about 10 kWe. The “flat” distribution of light we obtain can exploit the PV device cells close to their efficiency limit. A significant gain is thus obtained, with no need of secondary optics or complex dish segmentation and of special features in the receiver electrical scheme. In the design, based on seven 2.6 m mirrors, we addressed also non-optical aspects as the receiver and the supporting mechanics. Optical and mechanical tolerances are demonstrated not to exceed accurate, but conventional, industrial standards.

Study on Concentrating Characteristics of a Solar Parabolic Dish Concentrator within High Radiation Flux

Concentrating characteristics of the sunlight have an important effect on the optical-thermal conversion efficiency of solar concentrator and the application of the receiver. In this paper, radiation flux in the focal plane and the receiver with three focal lengths has been investigated based on Monte Carlo ray-tracing method. At the same time, based on the equal area-height and equal area-diameter methods to design four different shape receivers and numerical simulation of radiation flux distribution characteristics have also been investigated. The results show that the radiation flux in the focal plane increases with decreasing of the focal length and the diameter of the light spot increases with increasing of the focal length. The function of the position with a maximum of radiation flux has been obtained according to the numerical results. The results also show that the radiation flux distribution of cylindrical receiver has the best performance in all four receivers. The results can provide a reference for future design and application of concentrating solar power.

Shape Optimization for Parabolic Troughs Working in Non-ideal Conditions

The aim to realize more efficient solar concentrators, improves the research on the best configuration for the mirror surfaces. The optical behavior of a parabolic trough collector is investigated depending on its particular shape outside the ideal conditions. A 2D ray-tracing model of the real systems was realised taking into account a reference value for the solar radiation and different misalignment errors between the light beams and the mirrors axis.The computational analysis shows the relationship among the collection performance and the main geometrical parameters; different boundary conditions bring to consider different optimal configurations for the concentrator shape. Generally for medium concentration levels (50-150x) and non-ideal settings the more efficient parabolas are not characterized by a rim angle equal to 90°, which is the theoretical best value.Among the studied cases, it is interesting to note that a possible working condition for the PT system corresponds to a light beam scattering of 0.5° and a tracking misalignment of 0.2°.With these constrains, imposing high optical performance requirements, a maximum concentration ratio near to 60 can be reached with rim angle values of about 114°.

The role of FRET in solar concentrator efficiency and color tunability

We demonstrate concentration-dependent Förster-type energy transfer in a luminescent solar concentrator (LSC) material containing two high quantum yield laser dyes in a PMMA matrix. FRET heterotransfer is shown to be approximately 50% efficient in the regime of 2×10−3molal acceptor dye by weight in the host polymer. The two dyes used have been well studied for solar concentrator applications: BASF's Lumogen Red 305, and Exciton Chemical Company's DCM both demonstrate desirable stability, quantum yield, and complementary absorption spectra. We demonstrate how multiple-dye LSC devices employing FRET increase the absorption of air mass 1.5 solar irradiance without affecting the self-absorption properties of the film. Color tunability may be achieved through the addition of additional absorbers while minimizing the impact on waveguide efficiency.

Enhanced photon harvesting in silicon multicrystalline solar cells by new lanthanide complexes as light concentrators

Four europium complexes with enhanced luminescent properties have been synthesized. Thin transparent films of the complexes were prepared on glass panes and then were examined as efficient luminescent solar concentrators for full spectrum utilization in crystalline silicon photovoltaic cells. The complexes could behave as efficient solar concentrators since they absorb UV light, where the spectral response of the crystalline silicon solar cells is low and they emit at 615 nm where the spectral response is maximum. The glass panes covered with europium complexes act as planar waveguides of the emitted light that is collected by the solar cells, which are attached to the edges of the solar concentrators. The europium complexes as solar concentrators were examined in terms of the optimum concentrations and the number of coatings, which were determined in order to evaluate the maximum performance of the solar cells. The case of multiple glass panes with europium complexes was also examined while a 28% maximum increase in the photocurrent was finally established.