Crossed Compound Parabolic Concentrator Research Articles

Performance study of water-cooled multiple-channel heat sinks in the application of ultra-high concentrator photovoltaic system

For achieving cost effectiveness in solar power generation, ultra-high concentrator photovoltaic (UHCPV) system operating at 1800 suns is highly recommended in order to minimize the usage of semiconductor material. Although sunlight focusing can be accomplished via two-stage concentrator consisted of non-imaging dish concentrator and an array of crossed compound parabolic concentrator lenses, the thermal management of concentrator photovoltaic (CPV) cells remains as a crucial problem. The objective of this study is to optimize the configuration of multiple-channel heat sink with the best design in thermal performance so that the temperatures of CPV cells are below 100°C even operating under ultra-high concentrated sunlight. Comprehensive analysis has been carried out via computational fluid dynamics (CFD) simulation to study thermal performance of heat sinks for different configurations with various fin thicknesses and fin heights. To emulate the real case, optical analysis has been carried out via ray-tracing method to simulate the solar flux distribution and input solar power illuminated on receiver so that the results can be fed into the CFD modeling. The heat sink with configuration of 1mm fin thickness×20mm fin height (1×20) was found to be the most optimized design in which the CFD simulation has shown the lowest values for both average temperature of CPV cells and maximum temperature difference between CPV cells. By optimizing the average water velocity at 0.6m/s, the heat sink with the configuration of 1×20 can maintain the CPV cells operating at 91.4°C under solar concentrator ratio of 1800 suns and direct normal irradiance of 1000W/m2. Through the optimization of the thermal performance, the UHCPV system can produce the net electrical output power of 4064W at power conversion efficiency of 31.8%.

A novel absorptive/reflective solar concentrator for heat and electricity generation: An optical and thermal analysis

The crossed compound parabolic concentrator (CCPC) is one of the most efficient non-imaging solar concentrators used as a stationary solar concentrator or as a second stage solar concentrator. In this study, the CCPC is modified to demonstrate for the first time a new generation of solar concentrators working simultaneously as an electricity generator and thermal collector. The CCPC is designed to have two complementary surfaces, one reflective and one absorptive, and is named as an absorptive/reflective CCPC (AR-CCPC). Usually, the height of the CCPC is truncated with a minor sacrifice of the geometric concentration. These truncated surfaces rather than being eliminated are instead replaced with absorbent surfaces to collect heat from solar radiation. The optical efficiency including absorptive/reflective part of the AR-CCPC was simulated and compared for different geometric concentration ratios varying from 3.6× to 4×. It was found that the combined optical efficiency of the AR-CCPC 3.6×/4× remained constant and high all day long and that it had the highest total optical efficiency compared to other concentrators. In addition, the temperature distributions of AR-CCPC surfaces and the assembled solar cell were simulated based on those heat flux boundary conditions. It was shown that the addition of a thermal absorbent surface can increase the wall temperature. The maximum value reached 321.5K at the front wall under 50° incidence. The experimental verification was also adopted to show the benefits of using absorbent surfaces. The initial results are very promising and significant for the enhancement of solar concentrator systems with lower concentrations.

Performance study of crossed compound parabolic concentrator as secondary optics in non-imaging dish concentrator for the application of dense-array concentrator photovoltaic system

Optical and electrical analyses of non-imaging dish concentrator (NIDC) with secondary concentrator for the application in dense-array concentrator photovoltaic (CPV) system are presented. Array of crossed compound parabolic concentrator (CCPC) lenses is selected as secondary concentrator due to high acceptance angle, larger entrance aperture to provide more space for high flexibility of inter-connection among CPV cells, and square exit aperture matching well with commercial CPV cell. Electrical performance of integrated CPV cells with CCPC lenses (CPV+CCPC) assembly module is analyzed for different pointing errors: 0°, 0.1°, 0.2°, 0.3° & 0.4°, and the results are compared to that of dense-array CPV (DACPV) module. It was found that overall electrical performance of CPV+CCPC assembly module is better than that of DACPV module despite using 77% less CPV cells than that of DACPV module.

Coupled Simulation of Performance of a Crossed Compound Parabolic Concentrator with Solar Cell

An optimal installation of a compound parabolic concentrator (CCPC) into a scalable solar thermoelectrics and photovoltaics system is desirable by applying analytical tools to improve the optical and thermal performance of a CCPC with a solar cell. In this paper, the optical and thermal performances of an isolated CCPC with solar cell are investigated by employing commercial software ‘ANSYS CFX 15.0’ with a coupled optical grey and multiphysics model. Numerical results are validated against the experimental data at various incidence angles, especially for the optical concentration ratio and optical efficiency. Results confirm that ‘ANSYS CFX’ is an effective numerical tool for determining correctly both the optical and thermal behaviour of CCPC. The very important finding is a highest temperature core in the silicon layer of solar cell which may be responsible for a solar cell to work properly. The limitation of the work is that the electric performance of the solar cell is not involved and the simulations are steady.

Trapping light escaping from the edges of the optical element in a Concentrating Photovoltaic system

The encapsulant is an important element used for mechanical bonding and optical coupling between the concentrator and the solar cell in a typical concentrating photovoltaic system. In this work we explain the concept of trapping the light escaping through the optical concentrator – encapsulant interface. Understanding how the losses incur is important for the development of concentrating photovoltaic systems. A case study is performed on a 3D Cross Compound Parabolic Concentrator (3DCCPC) based low concentrating photovoltaic system. Detailed optical analysis is presented quantifying the losses based on the thickness of the encapsulant spillage. Simulation results show that the optical efficiency drops from 84.5% to 55.6% whilst increase in the encapsulant spillage thickness from 0.1mm to 3mm. Use of reflective film is made along the bottom edges of the concentrator in order to make the interface region optically inactive to carry out refraction and trap the escaping light. Modelling shows that the optical losses can be completely managed by the use of the reflective film. Experiments are carried out by building a prototype in order to demonstrate the concept and validate the results. The short circuit current is found to increase by a maximum of 8.5%. A maximum power ratio of 2.73 is observed at an incidence angle of 10° for the system using the reflective film compared to 2.56 without the reflective film.

Optical efficiency study of PV Crossed Compound Parabolic Concentrator

Static solar concentrators present a solution to the challenge of reducing the cost of Building Integrated Photovoltaic (BIPV) by reducing the area of solar cells. In this study a 3-D ray trace code has been developed using MATLAB in order to determine the theoretical optical efficiency and the optical flux distribution at the photovoltaic cell of a 3-D Crossed Compound Parabolic Concentrator (CCPC) for different incidence angles of light rays. It was found that the CCPC with a concentration ratio of 3.6× represents an improved geometry compared to a 3-D Compound Parabolic Concentrator (CPC) for the use as a static solar concentrator. The CCPC has a maximum optical efficiency of 95%, in line with the optical efficiency of the 3-D CPC, with the added advantage of having a square entry and exit aperture. A series of preliminary experimental measurements were taken on a setup of nine solar cells. The experimental results provide validation of the MATLAB code developed, showing a deviation of 12±2% from the simulation results, thus confirming that the code can be used to investigate different concentration ratios of the CCPC.

Analysis of static and quasi-static cross compound parabolic concentrators

Static and quasi-static concentrators present interesting characteristics for obtaining photovoltaic solar energy. In this work we study the characteristics of the crossed compound parabolic concentrator, formed by the intersection of two cylindrical compound parabolic concentrators (CPC). Bifacial cells are used in this concentrator as a requirement for obtaining higher concentrations. Static and quasi-static concentrators see the sun as an extended source, so a simplified source model of radiance for the sky of Madrid is used. The figures of merit of a lossless concentrator are studied and the most important parameters influencing its optical behavior are discussed. We conclude that these concentrators obtain results that lead to a decrease in the cost of photovoltaic energy.