Chee-Woon Wong

Optical Characterization of Nonimaging Planar Concentrator for the Application in Concentrator Photovoltaic System

The design and construction of miniature prototype of nonimaging planar concentrator, which is capable of producing much more uniform spatial irradiance and reasonably high concentration ratio, were presented in the previous paper. In this paper, we further explore the optical characteristics of the new concentrator that is specially designed to be incorporated in concentrator photovoltaic systems. For this study, we have carried out a comprehensive analysis via numerical simulation based on all the important design parameters, i.e., array of facet mirrors, f/D ratio, receiver size, and the effect of suntracking error, which lead to the overall optical performance of the new concentrator.

Optical characterization of nonimaging dish concentrator for the application of dense-array concentrator photovoltaic system

Optimization of the design of a nonimaging dish concentrator (NIDC) for a dense-array concentrator photovoltaic system is presented. A new algorithm has been developed to determine configuration of facet mirrors in a NIDC. Analytical formulas were derived to analyze the optical performance of a NIDC and then compared with a simulated result obtained from a numerical method. Comprehensive analysis of optical performance via analytical method has been carried out based on facet dimension and focal distance of the concentrator with a total reflective area of 120 m2. The result shows that a facet dimension of 49.8 cm, focal distance of 8 m, and solar concentration ratio of 411.8 suns is the most optimized design for the lowest cost-per-output power, which is US

Performance optimization of dense-array concentrator photovoltaic system considering effects of circumsolar radiation and slope error.

1.93 per watt.

Solar flux distribution analysis of Non-Imaging Planar Concentrator for the application in concentrator photovoltaic system

This paper presents an approach to optimize the electrical performance of dense-array concentrator photovoltaic system comprised of non-imaging dish concentrator by considering the circumsolar radiation and slope error effects. Based on the simulated flux distribution, a systematic methodology to optimize the layout configuration of solar cells interconnection circuit in dense array concentrator photovoltaic module has been proposed by minimizing the current mismatch caused by non-uniformity of concentrated sunlight. An optimized layout of interconnection solar cells circuit with minimum electrical power loss of 6.5% can be achieved by minimizing the effects of both circumsolar radiation and slope error.

General Formula for On-Axis Sun-Tracking System

The design and construction of Non-Imaging Planar Concentrator (NIPC), capable of producing much more uniform spatial irradiance and reasonably high concentration ratio, have been presented in our previous research paper. In this study, we would carry out a comprehensive analysis through the numerical simulation on solar flux distribution at the target by considering all the important criteria to improve the overall performance of dense-array concentrator photovoltaic system, which are the maximum solar concentration, uniform illumination area, spillage loss etc. Maximum solar concentration ratio and percentage of energy in uniform illumination area are plotted for different cases. In general, the simulated results have shown a reasonably good uniformity of solar irradiance and high concentration ratio at the receiver plane.

Study of image quality of mirror via solar flux distribution measurement using a high speed optical scanner

Sun-tracking system plays an important role in the development of solar energy applications, especially for the high solar concentration systems that directly convert the solar energy into thermal or electrical energy. High degree of sun-tracking accuracy is required to ensure that the solar collector is capable of harnessing the maximum solar energy throughout the day. High concentration solar power systems, such as central receiver system, parabolic trough, parabolic dish etc, are the common in the applications of collecting solar energy. In order to maintain high output power and stability of the solar power system, a high-precision sun-tracking system is necessary to follow the sun’s trajectory from dawn until dusk. For achieving high degree of tracking accuracy, sun-tracking systems normally employ sensors to feedback error signals to the control system for continuously receiving maximum solar irradiation on the receiver. Over the past two decades, various strategies have been proposed and they can be classified into the following three categories, i.e. open-loop, closed-loop and hybrid sun-tracking (Lee et al., 2009). In the open-loop tracking approach, the control program will perform calculation to identify the suns path using a specific suntracking formula in order to drive the solar collector towards the sun. Open-loop sensors are employed to determine the rotational angles of the tracking axes and guarantee that the solar collector is positioned at the right angles. On the other hand, for the closed-loop tracking scheme, the solar collector normally will sense the direct solar radiation falling on a closed-loop sensor as a feedback signal to ensure that the solar collector is capable of tracking the sun all the time. Instead of the above options, some researchers have also designed a hybrid system that contains both the open-loop and closed-loop sensors to attain a good tracking accuracy. The above-mentioned tracking methods are operated by either a microcontroller based control system or a PC based control system in order to trace the position of the sun. Azimuth-elevation and tilt-roll tracking mechanisms are among the most commonly used sun-tracking methods for aiming the solar collector towards the sun at all times. Each of these two sun-tracking methods has its own specific sun-tracking formula and they are not interrelated in many decades ago. In this chapter, the most general form of sun-tracking formula that embraces all the possible on-axis tracking approaches is derived and presented in details. The general sun-tracking formula not only can provide a general mathematical solution, but more significantly, it can improve the sun-tracking accuracy by tackling the

Dense-array concentrator photovoltaic system using non-imaging dish concentrator and crossed compound parabolic concentrator

A method to study the solar flux distributions of the solar images reflected by mirrors with different dielectric thicknesses is proposed in this paper. An optical scanner, also known as a flux mapping system, capable of acquiring the flux distribution pattern of a light source in a two-dimensional flat surface, has been designed and constructed. The optical scanner can measure the profile of flux distribution at reasonably high resolution with fewer photo-sensors with a fast scanning speed of several seconds. The real time measurement results of solar images projected by mirrors with dielectric thicknesses, i.e., 3 mm, 4 mm, 5 mm and 6 mm, have been performed to analyze their surface qualities.

Optimizing performance of dense-array concentrator photovoltaic system

Solar concentrating device plays an important role by making use of optical technology in the design, which can be either reflector or lens to deliver high flux of sunlight onto the Concentrator Photovoltaic (CPV) module receiver ranging from hundreds to thousand suns. To be more competitive compared with fossil fuel, the current CPV systems using Fresnel lens and Parabolic dish as solar concentrator that are widely deployed in United States, Australia and Europe are facing great challenge to produce uniformly focused sunlight on the solar cells as to reduce the cost of electrical power generation. The concept of non-imaging optics is not new, but it has not fully explored by the researchers over the world especially in solving the problem of high concentration solar energy, which application is only limited to be a secondary focusing device or low concentration device using Compound Parabolic Concentrator. With the current advancement in the computer processing power, we has successfully invented the non...

General formula for on-axis sun-tracking system and its application in improving tracking accuracy of solar collector

To optimize performance of dense array concentrator photovoltaic (CPV) system, we have acquired real time flux distribution pattern using novel optical scanner and then fed the data to computational modeling algorithm for the sake of designing optimized configuration of dense-array layout. As a case study, a prototype of non-imaging planar concentrator (NIPC) capable of producing reasonable uniform solar irradiance has been constructed to verify our new methodology in optimizing performance of CPV system. Current mismatch effect in dense array solar cells is crucial drawback that greatly affects electrical performance of CPV systems due to non-uniformity of solar irradiance. It always happens to any solar concentrator including NIPC prototype in which the non-uniformity is usually attributed to solar disc effect, slope error of reflective surface, structure misalignment, sun-tracking error etc. Improper handling of current mismatch problem can reduce maximum output power of the array considerably if a current-voltage (I-V) curve has many mismatch steps which will subsequently lead to low fill factor (FF) as well as conversion efficiency. Our computational modeling method is also validated via the work of field testing on the optimized configuration of dense-array solar cells with the NIPC prototype. The measured results are found to be in close agreement with the simulated results using the computational modeling in maximum output power.