Fei-Lu Siaw

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.

Temperature effects on the performance of dense array concentrator photovoltaic system

The performance of dense-array concentrator photovoltaic (CPV) is studied in detail by considering temperature distribution pattern generated from a water-cooled copper cooling block. Using water flow rate 0.400 kg/s and inlet temperature 30°C, the temperature distribution is simulated and the temperature values are used as a means to predict each CPV cells operating temperature. It is observed that a solar cell located at the central region of the array experiences the highest temperature of 58.3°C, while CPV cells located furthest to the center are operating at 7°C lower than the center region cell. For comparison purpose, we also investigated the effect of uniform temperature distribution for all the cells at 55.2°C. It is found that the output power varies by less than 1W compared to the case of non-uniform temperature distribution where each solar cell is experiencing a different temperature value. On the other hand, the output power increases to 462.70 W when the array temperature is reduced to 40°C, while the output power dropped to 418.60 W when the array temperature is increased to 100°C. Through better understanding of temperature effects to dense array CPV performance, a suitable cooling system can be designed to minimize power loss.

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

Optimizing performance of dense-array concentrator photovoltaic system

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.