Nabin Sarmah

Evaluation and optimization of the optical performance of low-concentrating dielectric compound parabolic concentrator using ray-tracing methods

We present a detailed design concept and optical performance evaluation of stationary dielectric asymmetric compound parabolic concentrators (DiACPCs) using ray-tracing methods. Three DiACPC designs, DiACPC-55, DiACPC-66, and DiACPC-77, of acceptance half-angles (0° and 55°), (0° and 66°), and (0° and 77°), respectively, are designed in order to optimize the concentrator for building façade photovoltaic applications in northern latitudes (>55 °N). The dielectric concentrator profiles have been realized via truncation of the complete compound parabolic concentrator profiles to achieve a geometric concentration ratio of 2.82. Ray-tracing simulation results show that all rays entering the designed concentrators within the acceptance half-angle range can be collected without escaping from the parabolic sides and aperture. The maximum optical efficiency of the designed concentrators is found to be 83%, which tends to decrease with the increase in incidence angle. The intensity is found to be distributed at the receiver (solar cell) area in an inhomogeneous pattern for a wide range of incident angles of direct solar irradiance with high-intensity peaks at certain points of the receiver. However, peaks become more intense for the irradiation incident close to the extreme acceptance angles, shifting the peaks to the edge of the receiver. Energy flux distribution at the receiver for diffuse radiation is found to be homogeneous within ±12% with an average intensity of 520 W/m².

Performance analysis of the lineal model for estimating the maximum power of a HCPV module in different climate conditions

A model based on easily obtained atmospheric parameters and on a simple lineal mathematical expression has been developed at the Centre of Advanced Studies in Energy and Environment in southern Spain. The model predicts the maximum power of a HCPV module as a function of direct normal irradiance, air temperature and air mass. Presently, the proposed model has only been validated in southern Spain and its performance in locations with different atmospheric conditions still remains unknown. In order to address this issue, several HCPV modules have been measured in two different locations with different climate conditions than the south of Spain: the Environment and Sustainability Institute in southern UK and the National Renewable Energy Center in northern Spain. Results show that the model has an adequate match between actual and estimated data with a RMSE lower than 3.9% at locations with different climate conditions.

Solar cells design for low and medium concentrating photovoltaic systems

The solar cell is the key element of any CPV system, and its design plays an important role in enhancing the performance of the entire system. Special types of cells are required in the CPV systems capable of operating at high concentrations and elevated temperatures. These Concentrator solar cells differ significantly from the usual solar cells in the method of manufacture, the overall cell design and their performance. Systematic design and manufacture of the cell ensures better performance in a given CPV system. A number of factors come into play while designing the solar cell for a specific system these include concentration, cell material properties, expected operating temperature, shape, bus bar configuration and finger spacing. Most of these variables are decided on based on some rules of thumb and PC1D calculations. However, there is scope for design improvement and cell optimization by performing a detailed analysis based on the illumination profile incident on the cell. Recent studies demonstrat...

Rotationally asymmetric optical concentrators for solar PV and BIPV systems

Building Integrated Concentrated Photovoltaic (BICPV) systems are one of the options to reduce the dependency on fossil fuels and minimise energy consumption in buildings. These systems not only contribute to the generation of electricity, but also to the reduction of energy consumption by allowing the passage of ambient light and by making use of the cogenerated heat for indoor heating and/or cooling. This paper presents a novel optical concentrator called Rotationally Asymmetric Dielectric Totally Internally Reflecting Concentrator (RADTIRC) for use in BICPV systems. The RADTIRC-PV structure is capable of providing a maximum power concentration of 4.2x. Key benefits of this technology include: reduction of cost of BICPV systems, flexibility of design, and higher electrical power outputs.

Indoor performance analysis of a low concentrating photovoltaic module for building integration

A low concentrating photovoltaic concentrator is designed for building integration in Edinburgh and higher latitudes (>55°). The dielectric Asymmetric Compound Parabolic Concentrator (ACPC) is manufactured by machining a 15mm thick PMMA sheet by a specially designed cutter. Maximum 2.1 times increase in power of the CPV module compared to the non-concentrating counterpart is observed at 15° incidence angle. The maximum short circuit current of the CPV module with 1 sun is found to be 439mA. The short circuit current and power of the CPV module is found to be decreased towards the extreme acceptance angles which is due to the higher optical losses, which may occur due to the light escaping from the parabolic surfaces and from the concentrator-encapsulation interface.

Design, Development, and Analysis of a Densely Packed 500x Concentrating Photovoltaic Cell Assembly on Insulated Metal Substrate

The paper presents a novel densely packed assembly for high concentrating photovoltaic applications, designed to fit 125x primary and 4x secondary reflective optics. This assembly can accommodate 144 multijunction cells and is one of the most populated modules presented so far. Based on the thermal simulation results, an aluminum-based insulated metal substrate has been used as baseplate; this technology is commonly exploited for Light Emitting Diode applications, due to its optimal thermal management. The original outline of the conductive copper layer has been developed to minimize Joule losses by reducing the number of interconnections among the cells in series. Oversized Schottky diodes have been employed for bypassing purposes. The whole design fits the IPC-2221 requirements. The plate has been manufactured using standard electronic processes and then characterized through an indoor test and the results are here presented and commented on. The assembly achieves a fill factor above 80% and an efficiency of 29.4% at 500x, less than 2% lower than that of a single cell commercial receiver. The novel design of the conductive pattern is conceived to decrease the power losses and the deployment of an insulated metal substrate represents an improvement towards the awaited cost-cutting for high concentrating photovoltaic technologies.

The design of a parabolic reflector system with high tracking tolerance for high solar concentration

A compact high concentrating photovoltaic (HCPV) module based on cassegrain optics is proposed; consisting of a primary parabolic reflector, secondary reflector and homogeniser. The effect of parabolic curvatures, reflector separation distance and the homogeniser’s height and width on the tracking tolerance has been investigated for optimisation. In this type of HCPV, the addition of a solid transparent homogeniser to the two stage reflector design greatly improves the tracking tolerance. Optical simulation studies show high optical efficiencies of 84.82 – 81.89 % over a range of ±1 degree tracking error and 55.49% at a tracking error of ±1.5 degrees.

Small-Volume Fabrication of a 144-Cell Assembly for High-Concentrating Photovoltaic Receivers

Concentrating photovoltaic (CPV) is a solution that is gaining attention worldwide as a potential global player in the future energy market. Despite the impressive development in terms of CPV cell efficiency recorded in the last few years, a lack of information on the modules manufacturing is still registered among the documents available in literature. This work describes the challenges faced to fabricate a densely packed cell assembly for 500× CPV applications. The reasons behind the choice of components, materials, and processes are highlighted, and all the solutions applied to overtake the problems experienced after the prototypes production are reported. This article explains all the stages required to achieve a successful fabrication, proven by the results of quality tests and experimental investigations conducted on the prototype. The reliability of the components and the interconnectors is successfully assessed through standard mechanical destructive tests, and an indoor characterization is conducted to investigate the electrical performance. The fabricated cell assembly shows a fill factor as high as 84%, which proves the low series resistance and the lack of mismatches. The outputs are compared with those of commercial assemblies. A cost breakdown is reported and commented: a cost of

Technical issues and challenges in the fabrication of a 144-Cell 500× Concentrating Photovoltaic receiver

0.79/Wp has been required to fabricate each of the cell assembly described in this paper. This value has been found to be positively affected by the economy of scale: a larger number of assemblies produced would have reduced it by 17%.

Design and production of a 2.5 kWe insulated metal substrate-based densely packed CPV assembly

Concentrating Photovoltaics (CPV) aims to reduce the cost of photovoltaic applications by replacing part of the semiconductor material with a less expensive concentrating material. The significant increase in irradiance and the related reduction of semiconductor area introduce some criticisms that affect the design, fabrication and operating stages. The system needs to handle high power and current densities and high heat fluxes, without having repercussions on the cost, the size and the weight of the module. The concentrating photovoltaic is an increasing market and a number of commercial companies has started or is starting to produce CPV receivers. Many papers have been published on the improvement in cell efficiency and on new systems design, but there is a lack of information about the manufacturing stage. An in depth investigation into benefits and weaknesses of assembly methods need to be carried out. This paper describes all the issues and the challenges faced during the fabrication of a novel large densely-packed system.