Tunku Abdul Rahman, in partial fulfillment of the requirements for the degree of Master of Science in Engineering. Theoretical modeling supported by experiments was performed to evaluate the optical performance of the CCPC-CPV composite module by investigating the detailed optical losses at each layer of the components.
Introduction
Research Background
The optical properties and performance of the SOE must be investigated to develop a reliable solution to the main problem. A good understanding of the optical properties is key to optimizing the performance of a CPV system.
Research Objectives
Since the CPV system mainly relies on optical elements, identifying the underlying causes of the optical losses helps to develop the real solution for optimizing the overall performance, including optical and electrical efficiency. To develop a ray tracing numerical simulation technique to investigate the characteristics of the CCPC module for the application of UHCPV system.
Outline of Thesis
In this study, a comprehensive optical characterization of the Crossed Compound Parabolic Concentrator (CCPC) module as the secondary optics of the ultra-high concentrator photovoltaic (UHCPV) system is presented by computational and laboratory methods. Both findings will be analyzed and compared to validate the accuracy and reliability of the proposed methodology.
Introduction to CPV system
Types of secondary optical element
Reflective light funnel
Tang and Liu suggested a V-trough concentrator for photovoltaic system application due to the higher uniformity of light intensity in the output area. A parabolic reflector is attached to the exit of the light funnel, as illustrated in Figure 2.4, and the focused incident will be poured down into the centralized receiver.
Compound Parabolic Concentrator (CPC)
The back surface of the CPC with lens wall can direct the incident to the outlet of the lens via second refraction. Based on their evaluation on several aspects, solid CPC earned the best score of three, as lens wall CPC only provides about 80% of the performance of the solid CPC in terms of solar accumulative energy collection, although it offers a wider acceptance angle.
Dome lens
In 2010, Fu, Leutz, and Annen discussed the optical properties of a "pole" as a secondary element for a Fresnel lens. Although the irradiance distribution generated at the top of the solar cell is relatively uniform at normal incidence, as the angle of incidence increases, it becomes progressively worse.
Evaluation of secondary optical element
Thus, some researchers have made great efforts to study the optical characterization of the cross composite parabolic concentrator as the secondary optics of the CPV system (Sellami, Mallick, and Mcneil, 2010; Sellami and Mallick, 2013; Baig, Sellami, and Mallick, 2015). Understanding the optical losses of the optics is essential for researchers to optimize their CPV system.
Overview of UHCPV system
Design of primary optical element
As shown in Figure 3.1(a), the NIDC is formed by 480 pieces of identical facet mirrors arranged in an array of 22 rows × 22 columns. The position of the facet mirrors is gradually lifted from central to peripheral regions to form a parabolic dish.
Overview of CCPC-CPV assembly module
The specification of the CCPC lens is listed in Table 3.2, and the detailed design rule of the CCPC lens used in this work was described in the previous work by Yew et al. Referring to Figure 3.2(a), the geometric design of the CCPC lens can be calculated using the following equations derived from Snell's law (Winston, Miñano, & Benitez, 2005). 𝑠𝑖𝑛 𝜃𝑖)2 (3.4) where 2α and 2α' represent the size of the input and output apertures, respectively, while L is the length of the CCPC lens. The half acceptance angle θ’i and angular half acceptance angle θ i of the CCPC lens can be calculated by Eqs.
Multi-junction solar cell
It is suitable for the application where the light enters the MJSC through secondary glass components or homogenizer. Because each pn transition material responds to a different range of the solar spectral irradiance in such a way that the three different III-V semiconductor materials can complement each other to cover almost the entire solar spectrum. In addition, the MJSC is designed to generate a high density of electrical power capable of accommodating high currents and high operating temperatures under highly concentrated sunlight compared to that of the conventional silicon solar cells.
Performance evaluation of CCPC-CPV assembly module
Simulation for different angle of incidence
The light source was placed at different angles of incidence relative to the entrance aperture of the CCPC-CPV module. Since the half acceptance angle of the CCPC lens is 37.77o, the range of the zenith angle used in the ray tracing simulation is from 0o to 37.77o, while the range of the azimuth angle used in the ray tracing simulation is from 0o to 360o. . The position of the light source changes according to the angle of incidence, which is listed in Table 3.7 and Table 3.8. acceptance angle of the CCPC lens).
Performance evaluation of the UHCPV System
A small gap of 50 mm is adjusted between the face mirrors to provide tolerance for installation in the actual assembly (Wong et al., 2017). The surface properties of the page mirrors are set as a standard mirror with a reflectance of 0.95. The overall SCR for the entire UHCPV system is obtained through simulation and will be discussed in Chapter 4.
Numerical analysis
Since three subcells in the MJSC are connected in series, the net output current of MJSC is limited by the lowest output current among the three subcells.
Experimental setup
Assembling CCPC-CPV assembly module
After applying a sufficient amount of optical glue, the CCPC lens is placed on top of the MJSC with the exit aperture facing down. The CCPC lens is wrapped by a small piece of fabric to prevent the glass from being stained by the solder fumes. This is to remove the flux residues and fingerprints left on the modules after soldering.
Indoor measurement
B The second letter indicates the uniformity of the radiation of the light source over the working area. The spectrum data of the light source generated by the solar simulator was measured using an AVANTES spectrometer and real-time data is collected through AvaSoft software. The effective SCR of CCPC-CPV assembly module can be obtained by comparing ICCPC-CPV (module with CCPC lens) and ICPV (module without CCPC lens).
Outdoor measurement
Five CCPC-CPV assembly modules are then used to collect data for ICCPC-CPV, as shown in Figure 3.13. This allows both modules to be exposed to the same amount of incident light within the same viewing angle. For outdoor measurements, the ICCPC-CPV and ICPV are measured by connecting the soldered external lead wires to the digital multimeter.
Comparison between full solar spectrum and single wavelength in simulation
The optical behaviour under different angle of incidence
It can be clearly seen that when ΦA = 90 as depicted in Figure 4.4(a), the incoming rays mainly fall on one side. It can also be verified through the simulation result as shown in Figure 4.6; the optical efficiency for ΦA of and 315 is higher compared to that of other azimuth angles. Based on Figure 4.6, the optical efficiency is not affected by the azimuth angle, unless the incidence angle is close to half the angular acceptance of the CCPC lens, which is 37.77o.
Optical efficiency profile of CCPC-CPV assembly module
As mentioned in the previous section, the use of optical glue will cause certain losses. Some light rays are refracted away from the MJSC due to the change of refractive index caused by the optical adhesive. For the rest of the simulation, the thickness of the adhesive layer is set to 1 mm and the thickness of the spill around the lens is set to 0.9 mm because it is the closest value to the actual adhesive thickness in the CCPC-CPV assembly. is module.
Optical losses occur at each component level
Therefore, it is impossible to change the geometry of the CCPC lens in this study and it has become a shortcoming of the design at the current stage. Further adjustments may be made to the geometry of the CCPC lens in the future to achieve this. The optical efficiency of the CCPC-CPV assembly module is 72.35% after considering the total optical losses as listed in Table 4.2.
Results for indoor and outdoor experiments
Overall, the effective optical efficiency of the CCPC-CPV junction module under direct full-spectrum solar light source outside the GCR is 5.998). The data collected during outdoor measurement are listed in Tables 4.4, 4.5 and 4.6 over three days of testing. The SCR of the CCPC-CPV assembly module under different solar irradiance is depicted in Figure 4.13.
Overall performance of UHCPV system
The simulated flux distribution map of the SOE inlet and the MJSC receiver is shown in Figure 4.15. The active area of the MJSC is only 9.8 mm × 9.8 mm, which means that the solar irradiance falling on the DBC will be wasted if there is no CCPC lens to direct sunlight to the solar cell. The total SCR of the entire UHCPV system is calculated by comparing the power intensity of the MJSC receiver with the standard irradiance of 1000 W/m2.
Conclusion
This shows that the algorithm and ray tracing technique used in this work presents a highly reliable and promising accuracy. Next, the performance of the CCPC-CPV assembly module under various practical scenarios is studied through experiments. Meanwhile, the outdoor measurement indicates that the CCPC-CPV assembly module can achieve an effective efficiency of out of GCR of 5,998) under real working conditions.
Recommended future work
2015) “A Dense Array Concentrator Photovoltaic System Using an Imageless Circular Concentrator and an Array of Crossed Compound Parabolic Concentrators”. 2013) “Performance of compound parabolic concentrators with polygonal apertures”, SOLAR ENERGY, 95, p. 2007) “Reduction of Fresnel back-reflection at the junction interface between hollow core PCF and single-mode fiber”, IEEE Photonics Technology Letters, 19( 13), p. 2011) 'Numerical Investigations of Solar Concentration. Concentration at the beginning of its commercial deployment, Progress in Photovoltaics Research and Applications, 14(5), p. 2012) 'Efficiency Analysis of Reflective 3D Cross Composite Parabolic Concentrating Photovoltaic Systems for Building Facade Integration', Progress in Photovoltaics : Research and Applications, 21, p. 2015) 'Efficiency study of a cross compound parabolic concentrator as a secondary optic in a non-imaging circuit. concentrator for the application of a dense array concentrator photovoltaic system', Solar Energy, 120, p. 2016) Design and Optical Evaluation of Secondary Optics to Optimize the Electrical Efficiency of a Dense Array Concentrator Photovoltaic System.
2015) “Efficiency Study of Cross Composite Parabolic Concentrator as Secondary Optics in Imageless Dish Concentrator for Dense Array Concentrator Photovoltaic System Application”, Solar Energy, 120, p. 2014) “Combination of a light funnel concentrator with a deflector for directional transmission of sunlight”, Energy Conversion and Management, 88, p. 2009) 'High concentration photovoltaic systems using III–V cells', Renewable and Sustainable Energy Reviews, 13(9), p. 2015) 'Efficiency Study of Cross Compound Parabolic Concentrator as Secondary Optics in Imageless Dish Concentrator for Dense Array Concentrator Photovoltaic System Application', Solar Energy, 120, p. .
