Sunlight Concentrators Research Articles

Concentration performance evaluation of sunlight concentrators: Fresnel lens, plano-convex lens, and parabolic mirrors for daylighting application

ABSTRACT This study investigates the concentration performance of three concentrator types – Fresnel lens, plano-convex lens, and parabolic mirrors in focusing sunlight onto a 1.5 mm diameter plastic optical fiber. The evaluation uses TracePro ray tracing software for simulation and analysis, considering visible light and infrared bands. Results show that parabolic mirrors achieved the highest concentration ratio at 7720 suns, followed by the Fresnel lens at 6400 suns, and the plano-convex lens at 2750 suns for a wavelength of 535 nm, surpassing geometric concentration values of 1202 suns. Efficiency measurements revealed that the Fresnel lens achieved 86% efficiency, the parabolic mirrors reached 97% efficiency, and the plano-convex lens achieved 93% efficiency. Additionally, the parabolic mirror demonstrated potential for creating the smallest concentration spot size due to its ability to focus light on a single point. This study highlights potential applications of sunlight concentrators in enhancing natural lighting in buildings and promoting energy efficiency. The comparative analysis of these concentrators offers insights into their performance characteristics, aiding in the selection and optimization of concentrators for daylighting applications. Moreover, this research supports the concept of green and sustainable energy by demonstrating the potential of solar energy to meet building energy demand and promote daylighting as a means to reduce reliance on conventional energy sources.

Гибридный концентраторно-планарный фотоэлектрический модуль с гетероструктурными солнечными элементами

The paper presents a promising solution for photovoltaic modules that provides overcoming the main conceptual limitation for the concentrator concept in photovoltaics - the impossibility to convert diffused (scattered) solar radiation coming to the panel of sunlight concentrators. The design of a hybrid concentrator-planar photovoltaic module based on heterostructure solar cells: A3B5 triple-junction and Si-HJT is presented. The results of initial outdoor studies of the module output characteristics are discussed and estimates of its energy efficiency are given.

Hybrid concentrator-planar photovoltaic module with heterostructure solar cells

The paper presents a promising solution for photovoltaic modules that provides overcoming the main conceptual limitation for the concentrator concept in photovoltaics --- the impossibility to convert diffused (scattered) solar radiation coming to the panel of sunlight concentrators. The design of a hybrid concentrator-planar photovoltaic module based on heterostructure solar cells: A3B5 triple-junction and Si-HJT is presented. The results of initial outdoor studies of the module output characteristics are discussed and estimates of its energy efficiency are given. Keywords: hybrid concentrator-planar photovoltaic module, multijunction solar cell, Si-HJT planar photoconverter, diffusely scattered radiation.

Diffuse optical properties of a Fresnel lens sunlight concentrator.

A combined module that combines a concentrator with planar photovoltaic circuits provides energy conversion of both parts of global terrestrial radiation: direct sunlight by concentrator solar cells and scattered (diffuse) sunlight by planar (non-concentrator) photoconverters. The decrease in Fresnel lens concentrating ability is usually associated with imperfections in the optical refractive surfaces, where some part of the direct light, which arrives normal to the surface of the Fresnel lens and is intended to be concentrated, becomes scattered and directed off the highly efficient concentrator solar cell. The diffuse light flux propagates inside the volume of the combined photovoltaic module. This flux undergoes multiple reflections from the structural elements, is partially absorbed, and ultimately reaches the photoconverters of the planar circuit. Thus, two types of diffuse light impinge the planar circuit: "external" from the atmosphere and "internal" produced by the Fresnel lens from direct light. This Letter proposes a method for determining the diffuse properties of sunlight concentrators such as Fresnel lens.

Multijunction solar arrays for space and terrestrial applications

Photovoltaic conversion of the solar energy is the most prospective direction of the renewable power engineering. Solar arrays ensure power supply of spacecrafts and are gaining increasingly more application on the Earth. In the majority of developed countries, laws on state support of the green power engineering assisted in a substantial increase of power of the solar photovoltaic systems have been adopted. The main barrier to increasing the terrestrial solar photovoltaics development rates is a relatively high cost of the solar electric power. The ways for reducing the cost are the rise of the efficiency of power systems and the reduction of the material consumption for arrays based on multijunction solar cells. Results of multijunction solar cells and modules developments for space and terrestrial solar arrays are discussed in the article. In the last years, a significant experience on creation of multijunction solar cells was accumulated. Cascade solar cells and solar photovoltaic installations on their base with sunlight concentrators have been developed. At present, the terrestrial cascade solar cell efficiency exceeds 45%, which is substantially higher than that in conventional Si and thin-film solar arrays. The cascade solar cell efficiency increase has been achieved at the expense of splitting the sunlight spectrum into several intervals by the solar cell semiconductor structure fulfilling more effective photon energy conversion of each of these intervals in a definite parts of this structure. It is shown that multijunction solar cells provide the highest efficiency and they are the basic components of space arrays. Multijunction solar cells provide the highest conversion efficiency of concentrated sunlight as well. It opens prospects for decreasing the solar cell area and cost proportionally to the sunlight concentration. Developed concentrated photovoltaic installations are promising for wide applications in the high scale terrestrial solar photovoltaic energetics.

Active Optical Beam Shaping Based on Liquid Crystals and Polymer Micro-Structures

Emerging applications requiring light beam manipulation, such as high-efficiency sunlight concentrators for solar cells, switchable micro-lens arrays for autostereoscopic displays, tunable lenses for augmented reality goggles, auto-focusing spectacles, and smart contact lenses, mostly depend on one or more active optical components with the desired and controllable beam modifying functionalities, preferably manufactured at relatively low cost. Recent progress in research on components based on the combination of liquid crystals (LCs) and various polymer micro-structures is reviewed in this paper. It is found that such components can address the demands appropriately and have the potential of paving the way for large-scale applications of active optical beam shaping components.

Analysis of spectral irradiance blurring by Fresnel lens sunlight concentrators

Solar spectral irradiance blurring in the focal plane of the Fresnel lens arising from the chromatic aberration (CA) inherent to a lens was studied. The experimental complex for recording both irradiance distribution and spectral irradiance redistribution for the radiation concentrated by a small-sized energy concentrator based on a solar simulator with the possibility of modeling the spectral composition of light is presented. The methodology for scanning the irradiance spectral redistribution by a fiber spectrometer is described.

Optical materials for lens concentrators of solar radiation

“Solar” Abbe number is proposed to operate in assessing the suitability of optical materials at sunlight concentrators manufacture. Comparative results are presented for materials practically used in concentrator photovoltaics from the point of view of designing Fresnel lenses from them with a high average concentration in the focal spot of the minimum size and at the same time with minimum focal length.

Hybrid Solar Cells with a Sunlight Concentrator System

Hybrid solar cells based on InGaP/Ga(In)As/Ge multijunction structures integrated into crystalline Si heat-removal base and provided with sunlight concentrator system based on linear Fresnel lenses and carboplastic mount structure have been developed and investigated. The hybrid solar cells with sunlight concentrators in the photovoltaic module provide a specific electric power of 390 W/m2 (AM0, 1367 W/m2) at a photoconverter unit specific weight reduced to 1.0 kg/m2. Improved photovoltaic characteristics and high radiation resistance allow using the proposed hybrid solar modules with sunlight concentrators in space solar batteries and autonomous power supply facilities.

Photovoltaic module with sunlight concentrators: numerical simulation of steady state thermal regime

Numerical simulation of a steady state thermal regime of photovoltaic modules with sunlight concentrators has been performed. Contribution of different heat transfer mechanisms in the total thermal balance was analysed. The applicability of the single cell model for calculating the photovoltaic module thermal regime was investigated using an assumption of identity of all similar photovoltaic “Concentrator-Converter” pairs in a module and for a matrix comprising 3x3 units.

Sunlight simulation in investigating characteristics of small-size sunlight concentrators and multijunction solar cells

Presented are technical solutions on constructing optical systems for experimental simulating the sunlight parameters. Designs of two types of solar simulators are proposed. In the first one, the spectrum and the radiation angular divergence are simulated on the basis of a continuous light source, what corresponds to the principle “necessity and sufficiency” of simulated parameters of the light flux in investigating optical and power characteristics of small-size sunlight concentrators (Fresnel lenses). In the second type simulator, based on a pulsed radiation source, the emphasis has been placed on high-quality simulation of irradiance and spectrum for satisfying requirements in recording current-voltage characteristics of multijunction solar cells and in determining their efficiency.

State-of-the-art Architectures and Technologies of High-Efficiency Solar Cells Based on III–V Heterostructures for Space and Terrestrial Applications

Multi-junction solar cells based on III–V compounds are the most efficient converters of solar energy to electricity and are widely used in space solar arrays and terrestrial photovoltaic modules with sunlight concentrators. All modern high-efficiency III–V solar cells are based on the long-developed triple-junction III–V GaInP/GaInAs/Ge heterostructure and have an almost limiting efficiency for a given architecture — 30 and 41.6% for space and terrestrial concentrated radiations, respectively. Currently, an increase in efficiency is achieved by converting from the 3-junction to the more efficient 4-, 5-, and even 6-junction III–V architectures: growth technologies and methods of post-growth treatment of structures have been developed, new materials with optimal bandgaps have been designed, and crystallographic parameters have been improved. In this review, we consider recent achievements and prospects for the main directions of research and improvement of architectures, technologies, and materials used in laboratories to develop solar cells with the best conversion efficiency: 35.8% for space, 38.8% for terrestrial, and 46.1% for concentrated sunlight. It is supposed that by 2020, the efficiency will approach 40% for direct space radiation and 50% for concentrated terrestrial solar radiation. This review considers the architecture and technologies of solar cells with record-breaking efficiency for terrestrial and space applications. It should be noted that in terrestrial power plants, the use of III–V SCs is economically advantageous in systems with sunlight concentrators.

Periodic microstructures for improved lens-to-waveguide coupling efficiency in microlens array planar solar concentrators

Thin form-factor planar sunlight concentrators fabricated using low-cost materials in conjunction with high-efficiency solar cells may prove economically competitive with silicon photovoltaics. A periodic structure with planar interfaces employing an array of microlenses and coupling structures is amenable to high-volume imprint manufacturing and hence a drastic cost reduction. A numerical study of periodic prismatic void structures aligned with microlenses to efficiently couple incoming light into a constant cross-section channel waveguide is reported. Three different prism-like cut-out structures: a bare prism, a planar connected prism, and a pointed prism are proposed. Numerical results show that the proposed pointed prism design offers a high-efficiency coupling with one-sided output (90.8% and 85.4% peak efficiency at concentration ratios of 320× and 400×, respectively).

Prism-Based Sunlight Concentrator Layout: A Genetic Algorithm Solution

Solar energy is a promising source of energy because it is abundant and harmless to the environment. One of the critical issues involving solar energy is the layout design of sunlight concentrators. This study presents a computational method for reforming the layout of a special sunlight concentrator that consists of a set of prisms to significantly enhance its light intensity. Sunlight movement toward the prisms is modeled, and a genetic algorithm is applied to find a good concentrator layout. Experiments under various light transmission rates validate the performance of our proposed method. The proposed optimal sunlight concentrator layout improves the intensity of light by 55%.

Asymmetric and symmetric light couplers of daylighting systems for direct indoor lighting

Daylighting systems, which collect and transport sunlight directly into building interiors for illumination, can reduce conversion losses between different forms of energy, and thus increase the efficiency of using solar energy. To collect enough sunlight for indoor illumination, a large number of sunlight concentrators and high-efficiency light couplers are needed. In the study, we developed theoretical models of the symmetric and asymmetric Y-couplers, and conducted numerical simulations of the light couplers of three coupling angles, 10°, 30° and 50° using LightTools and Matlab. The coupling efficiencies of the asymmetric Y-couplers were 5% in average higher than those of the symmetric Y-couplers. The light couplers with a large coupling angle (50°) achieved higher coupling efficiency for the light rays of large propagation angles, and the light couplers with small coupling angles achieved 100% coupling efficiency for the light rays of small propagation angles (<24°). Therefore, the f/# of the sunlight concentrators can be calculated from the coupler parameters to reduce the angles of the light rays and thus to increase the coupling efficiency. For the branch guide to have high efficiency, the largest coupling angle of the Y-couplers was equal to the critical propagation angle 46.77°.

Indoor illumination by solar light collectors

An innovative system for illumination of internal spaces was studied, constructed and tested. The system was dubbed `The Sunflowers' because the solar collectors were designed to track the sun's position during the day. Each Sunflower includes sunlight concentrators, optical fibres and mechanical and electronic systems for sun tracking. A Sunflower lighting system has been successfully installed in a prestigious museum to provide internal illumination of showcases. Solar illumination is obtained by concentrating the sunlight into optical fibres, which guide the light in the interior of the building and realise the lighting points.

High-efficiency AlGaAs/GaAs concentrator (2500 suns) solar cells

A study is made AlGaAs/GaAs heterostructure solar cells that have been optimized for ultrahigh concentrations of sunlight (1000–2500 suns). The maximum efficiencies were 25.1% at 500 suns, 25% at 1000 suns, and 22.8% at 2000 suns for sunlight passing through an air mass of AM1.5. Cells of this type open up the possibility of reducing the surface area of solar cells by more than three orders of magnitude and, as a result, substantially lowering the cost of electrical energy in power equipment with sunlight concentrators.

Luminescent-dye-doped-plastics characterization for light intensity sensing

Luminescent-dye-doped-plastics are nowadays extensively used for esthetic purposes (toys, ballpoint pens, etc.). In the early 1980's, these materials were investigated to be used as sunlight concentrators in energy generation. Recent developments in fiber optic technology, beyond mere data transmission, lead us to consider the feasibility of using such materials for light intensity sensing in fiber optic sensors networks. The sensor described in this work has proved to show high linearity, reproducibility and stability, and low directivity, however it lacks high sensitivity. Further optimization of some design parameters will definitely help to improve it.

The use of reflectors in venetian blinds to enhance irradiance in greenhouses

Using a venetian blind as a basis, we describe and analyse novel forms of high-gain, nonfocussed sunlight concentrators and test experimental versions. Generally, midday winter light passing mainly through the roof of an E-W single-span greenhouse is reflected downwards to the floor through the use of conventional and modified reflecting louvres in a venetian-blind assembly suspended from the greenhouse apex. Experimentally, in a 7.3-m wide compartment, a 2-m deep conventional louvre assembly produced approximately an 18% gain in the southern half of the house, but a 4% loss in the northern half. A modified louvre assembly, which directs light to both halves of the house, gave, without readjustment of the louvre angle, 16% in the southern half and 7 1 2% in the northern half. Under diffuse light conditions the blind was shown to produce an average 2% loss across the house. As a percentage of light received by the plant, as opposed to external irradiance, an average of 20% gain over the whole house width is predicted under sunny conditions if better manufacturing techniques are employed. Reasonable agreement with theoretical calculations of irradiance is also shown, and a theoretical analysis shows that full irradiance enhancement before and after midday, when oblique sunlight is incident on the reflector, will still be generally obtained.