Novel nonimaging solar concentrator for portable solar systems for developing countries

Portable solar chargers have been gaining popularity as a new technology to help increase electrification in rural areas in developing countries. It is a fast developing industry aiming to produce a low-cost solution for the application of off-grid solar lighting and charging of small devices to be used by the poorest and most vulnerable of society. Solar concentrators are proposed as an add-on to help further reduce costs, to increase light-output hours and to reduce charging time. So far, no suitable concentrator designs have been proposed. This paper presents a novel concept for the design of a static nonimaging concentrator, suitable for portable solar systems for developing countries. The novel concentrator design is compared with existing concentrators and its suitability for portable solar chargers, as well as its potential for further improvement, are highlighted

Photonics in photovoltaic systems

This paper gives an overview on photonics for photovoltaic systems. Starting from the spectral and angular distribution of the electromagnetic radiation from the sun, many important optical approaches how to improve the efficiency of solar cells are presented and discussed. Topics include antireflective coatings, various light trapping structures, refractive, reflective and fluorescent concentrators, and components for spectral management. The theoretical background is shortly described and examples of the experimental and also of the commercial realisation are given

Refractive integrated nonimaging solar collectors design and analysis of a novel solar-daylighting-technology

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.A novel and original category of low-cost static solar-daylighting-collectors named Keywo solar energy, solar collectors, daylighting systems, nonimaging optics, Refractive Integrated Nonimaging Solar Collectors (RINSC) has been designed and thoroughly tested. The RINSC category is based on nonimaging optics and integrates several optical elements, such as prismatic arrays and light guides, into a single-structured embodiment made of solid-dielectric material. The RINSC category is sub-divided in this thesis into four distinctive and original sub-categories/systems: Prismatic Solar Collectors (PSC), Multi-Prismatic Solar Collectors (MPSC), Integrated Multi-Prismatic Solar Collectors (IMPSC) and Vertically Integrated Nonimaging Solar Collectors (VINSC). The optical configuration and compact embodiment of these systems allows them to be integrated into a building façade without creating any protrusion, indicating that they can lead to solar collector systems with high building integration potential. Laboratory and outdoor experimental tests conducted with a series of demonstration prototypes made of clear polymethyl-methacrylate (PMMA) and manufactured by laser ablation process, yield peak transmission efficiencies TE varying from 2% to 8%. Computer simulations indicated that transmission efficiencies TE > 30% are possible. The design and development of the innovative optical systems introduced in this thesis were backed-up with extensive computer ray-tracing analysis, rapid-prototyping, laboratory and outdoor experimental tests. Injection moulding computer simulations and surface analysis concerning the development of the RINSC systems were also conducted. Basic theory and comprehensive literature review are presented. This research has also resulted in the design and prototyping of a novel optical instrumentation named Angular Distribution Imaging Device (ADID), specially developed to analyse the spatial distribution of light emerging from the exit aperture of solar collectors/concentrators. The systems and knowledge described in this thesis may find application in areas such as solar collector systems to harvest sunlight for natural illumination in buildings, solar-photovoltaic and solar-thermal.Funded in part by the Brazilian National Council for Scientific and Technological Development (CNPq), under the scholarship grant 200663/2004-6 (GDE)

Experimental characterization of Fresnel-Köhler concentrators

Most cost-effective concentrated photovoltaics (CPV) systems are based on an optical train comprising two stages, the first being a Fresnel lens

A Review of Solar Photovoltaic Concentrators

Throughout the recent centuries, the limits of using energy resources due to the cost and environmental issues became one of the scientists’ concerns. Because of the huge amount of energy received by the Earth from the sun, the application of photovoltaic solar cells has become popular in the world. The photovoltaic (PV) efficiency can be increased by several factors; concentrating photovoltaic (CPV) system is one of the important tools for efficiency improvement and enables for a reduction in the cell area requirement. The limits of the PV area can reduce the amount of absorbing irradiation; CPV systems can concentrate a large amount of sunlight into a smaller one by applying lenses or curved and flat mirrors. However, the additional costs on concentrating optics and cooling systems made CPV less common than nonconcentrated photovoltaic. This paper reviews the different types of PV concentrators, their performance with advantages and disadvantages, concentration ratio, acceptance angle, brief comparison between their efficiencies, and appropriate cooling system

Recent trends in concentrated photovoltaics concentrators' architecture

The field of concentrated photovoltaics (CPV) has met some remarkable advances in recent years. The continuous increase in conversion efficiency of multijunction solar cells and new advancements in optics have led to new demands and opportunities for optical design in CPV. This paper is a mini-review on current requirements for CPV optical design, and it presents some of the main trends in recent years on CPV systems architecture

Improving performances of fresnel cpv system: fresnel-rxi köhler concentrator

A novel and advanced photovoltaic concentrator optic is presented comprising a Fresnel lens and a dielectric solid RXI as a secondary optical element, both with free-form surfaces (i.e. neither rotational nor linear symmetry). The RXI secondary is designed with the Simultaneous Multiple Surface (SMS) design method of Nonimaging Optics. In the secondary optics rays undergo refraction (R), reflection (X) and total internal reflection (I), so SMS nomenclature [2] for the device is RXI assigning letters to each surface that deflects rays. This is the first time the RXI-type geometry has been applied to design a photovoltaic secondary element. The LPI patented Fresnel- RXI Köhler concentrator [1] produces both the desired light concentration with high tolerance (high acceptance angle) as well as high irradiance uniformity on the solar cell achieved by Köhler integration method. The optical performance of the FRXI device (F denotes a Fresnel lens surface) will be presented as well as comparison with other conventional Fresnel-based CPV concentrators and application of the designed syste

Freeform Fresnel RXI-RR Köhler design with spectrum-splitting for photovoltaics

The development of a novel optical design for the high concentration photovoltaics (HPCV) nonimaging concentrator (>500x) that utilizes a built-in spectrum splitting concept is presented. The primary optical element (POE) is a flat Fresnel lens and the secondary optical element (SOE) is a free-form RXI-type concentrator with a band-pass filter embedded in it. The POE and SOE perform Köhler integration to produce light homogenization on the receiver. The system uses a combination of a commercial concentration GaInP/GaInAs/Ge 3J cell and a concentration Back-PointContact (BPC) silicon cell for efficient spectral utilization, and an external confinement technique for recovering the 3J cell’s reflection. A design target of an “equivalent” cell efficiency ~46% is predicted using commercial 39% 3J and 26% Si cells. A projected CPV module efficiency of greater than 38% is achievable at a concentration level greater than 500X with a wide acceptance angle of ±1º. A first proof-of concept receiver prototype has been manufactured using a simpler optical architecture (with a lower concentration, ~100x and lower simulated added efficiency), and experimental measurements have shown up to 39.8% 4J receiver efficiency using a 3J cell with a peak efficiency of 36.9

Stationary Nonimaging Concentrators – A Comprehensive Study and Design Improvements

Most places on our planet receive an annual average radiation between 800-1000 W/m2. In the man-made world, this radiation is largely incident on stationary structures such as buildings, roads, monuments, bridges etc. Moreover, in the natural world also, there are large tracts of barren land which can be put to good use given their solar energy potential. The vision of the current research is to concentrate all this available solar energy to a more readily usable form. Therefore, stationary nonimaging solar concentrator technologies are sought after. This dissertation work is an exhaustive research on the nonimaging concentrating mechanisms with stationary applications in mind. Novel nonimaging concentrator designs have been proposed and verified through raytracing computer simulations. A possible coupling of the proposed nonimaging concentrators with passive solar tracking mechanism has also been discussed. The effect of Fresnel reflection and total internal reflection (TIR) losses on the performance parameters and thereby, energy collection of refractive-type nonimaging solar concentrators has also been researched. A raytracing analysis has been carried out to illustrate the effects of Fresnel reflection and TIR losses on different types of stationary dielectric-filled nonimaging concentrators. The refractive index of a dielectric fill material determines the effective acceptance angle of a solid stationary nonimaging collector. Larger refractive indices yield larger acceptance angles and, thereby, larger energy collection. However, they also increase the Fresnel reflection losses. The relative benefit of increasing refractive index from an energy collection standpoint has also been assessed. This work is significant because it presents a realistic idea of the diurnal energy collection when a stationary concentrator is subjected to reflection losses. The work should be of interest to readers in the area of nonimaging optics especially when applied to stationary solar energy applications. The application of novel design ideas to mitigate the energy losses and improve the collection efficiency has been discussed in detail. The use of anti-reflective coatings and the concept of stacked CPCs are the areas that have been explored in detail. Some truncated designs of solid nonimaging concentrators for stationary applications have also been investigated as a part of this research work. In short, this work will be found resourceful in stationary solar energy collection applications and the uses are endless, viz. building integration, stationary solar collector fields etc. Future work in the topic should investigate to solve the material constraints imposed to further improve the effectiveness of the proposed stationary solar collector designs

Progress In FK Concentrators

The Fresnel Köhler (FK) concentrator was first presented in 2008. Since then, various CPV companies have adopted this technology as base for their future commercial product. The key for this rapid penetration is a mixture of simplicity (the FK is essentially a Fresnel lens concentrator, a technology that dominates the market) and excellent performance: high concentration without giving up large manufacturing∕aiming tolerances, enabling high efficiency even at the array level. All these features together have a great potential to lower energy costs. This work shows recent results and progress regarding this device, covering new design features, measurements and tests along with first performance achievements at the array level (pilot 6.5 Kwp plant). The work also discusses the potential impact of the FK enhanced performance on the Levelized Cost Of Electricity (LCOE