Crossed Compound Parabolic Concentrator Research Articles

Comparative Analysis of Reverse Truncated Pyramid and Other Nonimaging Concentrators as the Receiver in Laser Wireless Power Transmission System

The global energy landscape faces significant challenges in meeting the demands of modern industries for stable and efficient energy supply. Laser wireless power transmission (LWPT) systems, which utilize the photovoltaic effect to convert laser beam energy, hold great promise due to their long-range transmission capability and high precision. However, the current energy conversion efficiency of these systems requires further improvement to achieve optimal performance. To enhance concentrated photovoltaic (CPV) system performance, the study examines different nonimaging concentrators such as reverse truncated pyramid, cross-compound parabolic concentrator, and square elliptical hyperboloid. Numerical simulations using the finite element method analyze the multifield coupling mechanism of PV modules with various concentration lenses. Three CPV systems with RTP concentrators of different heights were studied to understand the impact of geometry on CPV performance. And the main impact of rotation angle was discussed. The research findings provide essential insights into CPV system performance and the influence of different concentration lenses, contributing valuable knowledge towards improving LWPT technologies.

Development of a comprehensive method to estimate the optical, thermal and electrical performance of a complex PV window for building integration

Increasing concerns over energy consumption and greenhouse gas emissions in buildings have contributed to the emerging of innovative PV glazing technologies to improve the building energy performance. However, some of these glazing systems have complex structures, making it challenging to investigate their optical, thermal and electrical performance for estimating their energy saving potential in buildings. In this research, a validated Computational Fluid Dynamics (CFD) combined with a ray-tracing model has been developed to accurately predict the optical, thermal and electrical performance of complex PV glazing systems under varying incident angles. A ray-tracing model is developed to calculate the light transmittance of the window and the solar energy absorbed by each solid element and PV cells. To estimate temperature profiles (e.g., PV temperature and window temperature) and secondary heat within the window, the results from the ray-tracing analysis, which detail the solar flux absorbed by each layer, are inputted into a validated CFD model as boundary conditions. Using the CFD combined ray-tracing calculation illustrated above, the Solar Heat Gain Coefficient (SHGC) of these complex PV window systems can be obtained. Furthermore, a PV modelling algorithm is developed to predict the power output based on the simulated PV temperature. This procedure is implemented to investigate a Crossed Compound Parabolic Concentrator Photovoltaic (CCPC-PV) window, which serves as an example of a complex PV glazing system in this study. The developed optical, thermal and electrical models have been validated through experimental tests. Additionally, new configurations have been designed to explore the impact of the pitch between adjacent optics on the SHGC and power output of the window. The results show that the original window (1.77 mm-pitch) possesses the maximum PV temperature of 64.73 °C and the maximum window inside surface temperature of 61.58 °C under National Fenestration Rating Council (NFRC) standard. Meanwhile the PV efficiency is 15.21 % and the SHGC is 0.463. The SHGC value of this innovative PV window is notably lower than that of a conventional double-glazed window, which has a SHGC value of 0.813. This reduction in SHGC decreases the likelihood of overheating issues, especially during the summer months.

Comprehensive investigation of a building integrated crossed compound parabolic concentrator photovoltaic window system: Thermal, optical and electrical performance

Integrating PV solar cells with concentrators into window systems can not only generate electricity for a building, but also has the potential to enhance the thermal resistance of the building's windows without a significant sacrifice of light transmittance for passive daylight. A novel system, known as the crossed compound parabolic concentrator photovoltaic window, has been recently studied for its electrical properties. However, its thermal and optical performance, particularly in terms of the overall heat transfer coefficient (U-value) and total optical transmittance when integrated into a building, remains unexamined. These factors are crucial for predicting the system's impact on a building's energy efficiency and indoor comfort. Therefore, this paper aims to investigate the U-value of this window system under various temperature scenarios and the optical transmittance of the window at different incident angles. The thermal conductance was assessed through numerical simulations using a computational fluid dynamics model, which was validated by experimental measurements conducted in a large climate chamber. The optical transmittance was investigated using a validated 3D ray-tracing model. The total optical transmittance and electricity generation were calculated for typical sunny days in winter and summer under London's climate conditions. Additionally, alternative designs were developed to explore the impact of pitch between adjacent optics on the thermal conductance and optical transmittance of the window. The results showed that the window with a configuration of Dx = Dy = 5 mm (where Dx and Dy represent the horizontal and vertical pitches, respectively, between two adjacent solar optics) achieved the lowest U-value (2.566 W/m2·K). This U-value is slightly lower than that of the original window design, which has a U-value of 2.575 W/m2·K. The original window configuration with Dx = Dy = 1.77 mm produces the highest power output. Specifically, it generates 499.25 Wh/m2 on a typical sunny day in winter and 162.73 Wh/m2 on a typical sunny day in summer. However, it exhibits the lowest transmittance (14.6 % on a typical sunny day in winter and 25.2 % on a typical sunny day in summer, respectively), indicating that it is more suitable for buildings with a higher window-to-wall ratio to ensure an adequate amount of natural light. For buildings with a lower window-to-wall ratio, the CCPC-PV window should be designed with a larger horizontal pitch, such as 15 mm and 30 mm, to meet indoor illuminance requirements while also providing enhanced thermal performance and additional power output.

Improving angular response of crossed compound parabolic concentrators using rectangular entry aperture

A novel design of crossed compound parabolic concentrator (CCPC) that has a rectangular entry aperture is presented, which has the advantage of considerably improved angular response compared to a conventional CCPC that has a square entry aperture. It is found that the half acceptance angle of this novel design is 40° for a 4.0x rectangular concentrator when operating in the “east-west” direction, which is approximately 10° larger than that of a conventional square concentrator of the same concentration ratio. This is a substantial increase and completely unexpected because the design theory for this type of concentrators predicted a much smaller half acceptance angle of 26.6°. Experimental and simulation work reported in this paper confirms this discovery. The results reveals that the observed improvement is attributed to multiple light reflection inside the concentrator, which was not considered in the commonly employed design theory. An important implication of this work is that the multiple light reflection plays an important role in the angular response of the CCPC and its effect cannot be neglected in the design.

Performance investigation of SUNTRAP module for different locations: An energy and exergy analysis

Concentrating Photovoltaic/Thermal (CPV/T) systems can harness the freely available solar energy to simultaneously generate electricity and sensible heat. Using the principles of optical concentration, they can generate more electrical energy per unit area of solar cells and provide a better quality of thermal energy. In this work, we have developed an analytical model to simulate and predict the performance of a dense array hybrid CPV/T collector called “SUNTRAP.” The concentration of incident radiation is achieved using a reflective type three-dimensional cross-compound parabolic concentrator (3DCCPC) with a geometric concentration ratio of 3.6 × . The extraction of heat from the solar cells is achieved by allowing water to flow through the copper cooling duct on which the solar cells with CCPC are bonded. Using previously developed algorithms, the optical efficiency of the CCPC is calculated as a function of solar azimuth and altitude angle. The obtained optical efficiency is coupled to the thermal model to obtain the temperature distribution in the collector. The numerical results are in good agreement with the experimental measurements obtained at the outdoor solar laboratory at Penryn Campus, Cornwall. The average deviation in outlet water temperature between the numerical and experimental ones is 1.9%. The total electrical and thermal energy obtained from the CCPC-PV/T module on an experimental day is 1.21 kWh/m2 and 46.46 kWh/m2. A parametric study was done to obtain the effect of flow rate and external wind velocity on the performance of the collector. The solar cell temperature is found to decrease with an increasing flow rate. The performance prediction of the CCPC-PV/T module at Penryn shows that the module produced maximum energy in August, producing 7.51 kWh/m2 of useful energy. An economic analysis was performed to obtain the Levelized cost of electricity (LCOE) that the CCPC-PV/T module can deliver, and the LCOE was found to be £1.08/kWh. The coupled model is also utilised to predict the performance of the system for five different geographical locations, including Chennai, Rome, Alice Springs, Montreal, and Barrow. The model considers optimum panel tilt and time-dependent optical efficiency of the concentrator while estimating the energy output. Based on the results, the overall performance of the collector was found to be good in Chennai, with an annual electrical energy gain of 51.95 kWh/m2 and an annual thermal energy gain of 1164 kWh/m2.

An IoT Based on Smart CPV Units Composed of a Hyperbolic Optical Element

The first part of the study refers to the development of a 3D solar concentrator composed of two optical elements; a flat circular Fresnel lens associated with a hyperbolic concentrator. This research is conducted to provide better insight into the concentrator optical performance. The concentrator optical performance system is evaluated for the acceptance angle, achieved concentration, fresnel lens tolerances in secondary element placement, and flux distribution on the secondary optic output. Results show the optical efficiencies of the circular apertures and the square apertures of hyperbole as a function of the heights. We noticed that the circular apertures of hyperbole present high optical efficiency for lengths of 30 to 55mm. Still, beyond this length, the square apertures of the hyperbole exhibit higher optical efficiency. Comparison of these optical elements as secondary optical elements with the elements studied in the previous work (pyramid, compound parabolic concentrator, cone, crossed compound parabolic concentrator). We found that pyramid remains the best secondary optical element for a Fresnel lens as a primary optic. The second part is based on deploying a new cost-effective method using IoT to remotely monitor and assess a photovoltaic plant operation. Using technology to supervise concentrated solar generation can significantly improve plant performance, monitoring, and maintenance. This will make preventive maintenance, defect detection, historical plant analysis, and real-time tracking easier. The follow-up program successfully collected all the data from morning till evening. The mean transmission time is 52.34 seconds, with 30 and 102 seconds the shortest and greatest transmission times.

Comparison analyses of three photovoltaic solar-assisted heat pumps based on different concentrators

The main problem of concentrated photovoltaics is the high temperature caused by high radiance, which deteriorates the electrical efficiency and service life of photovoltaic cells. Most concentrated photovoltaics are assembled into the photovoltaic/thermal systems and cooled by water. However, if concentrating photovoltaics is combined with an evaporator in a direct-expansion solar-assisted heat pump, the photovoltaic damages (reduced life span and conversion efficiency of photovoltaic cells) caused by the high temperature in concentrators will be much better alleviated. But at present, there is little research on the combination of concentrating photovoltaic and direct-expansion solar-assisted heat pump. To enrich the relevant content and explore the optimal concentrating method combined with heat pumps, three hybrid heat pumps with different concentrating evaporators are proposed and investigated. Results indicate that in the photovoltaic heat pump system based on Fresnel concentrator, photovoltaic heat pump system based on compound parabolic concentrator, and the photovoltaic heat pump system based on 3-D crossed compound parabolic concentrator, the electrical efficiency could achieve 30.31%, 15.37%, and 11.66% under 300 W/m2. The coefficient of performance (considering both electricity and heat) could reach 7.65, 5.67, and 5.45 under 800 W/m2, meanwhile, the 29.87%, 16.25%, and 13.66% exergy efficiency can be obtained under the same irradiation. Therefore, the photovoltaic heat pump system based on Fresnel concentrator has the best capacity, followed by the system based on compound parabolic concentrator and 3-D crossed compound parabolic concentrator. Besides, in the FPV-SAHP system, two concentration ratios are designed and discussed. And the effect of ambient temperature, water temperature, as well as solar irradiance on the systems is also explored.

Comprehensive analysis on the assembly of a dielectric-filled crossed compound parabolic concentrator and a concentrator photovoltaic module.

A comprehensive analysis on assembly of dielectric-filled 3D crossed compound parabolic concentrator (CCPC) and concentrator photovoltaic (CPV) module is presented by embracing the consideration of spectral irradiance, incident angles, and breakdown optical losses. The theoretical modeling is supported by experimental validation to evaluate the optical efficiency of the CCPC-CPV module. From our analysis, Fresnel reflection loss of 11.27%, absorption loss of 11.59%, and other losses of 4.79% are obtained to reach the total loss of 27.65% or equivalent solar concentration ratio (SCR) of 4.65 suns out of a geometrical concentration ratio (GCR) of 5.998 suns. Then, indoor and outdoor measurements prove the actual SCR of 4.57 and 4.48 suns, respectively.

Experimental Investigation of a Novel Absorptive/Reflective Solar Concentrator: A Thermal Analysis

This paper presents the experimental investigation of a novel cross-compound parabolic concentrator (CCPC). For the first time, a CCPC module was designed to simultaneously work as an electricity generator and collect the thermal energy present in the module which is generated due to the incident irradiation. This CCPC module consists of two regions: an absorber surface atop the rig and a reflective region below that to reflect the irradiation onto the photovoltaic (PV) cell, coupled together to form an absorptive/reflective CCPC (AR-CCPC) module. A major issue in the use of PV cells is the decrease in electrical conversion efficiency with the increase in cell temperature. This module employs an active cooling system to decrease the PV cell temperature, optimizing the electrical performance and absorbing the heat generated within the module. This system was found to have an overall efficiency of 63%, which comprises the summation of the electrical and thermal efficiency posed by the AR-CCPC module.

Optical and Electrical Performance Evaluation of the Crossed Compound Parabolic Concentrator Module for the Application of Ultra-High Concentrator Photovoltaic System

This paper presents the performance evaluation in terms of optical and electrical characteristics of the crossed compound parabolic concentrator (CCPC) module for the application of the ultra-high concentrator photovoltaic (UHCPV) system. The CCPC module is the integration of a dielectric-filled 3D CCPC lens and a multi-junction solar cell (MJSC) module. The optical efficiency of the refractive lens has been evaluated through the ray-tracing simulation technique by including all the possible optical losses at each component level, and the output current of the MJSC module has also been calculated in accordance with its spectral response to the wavelengths range from 300 nm to 1800 nm. The optical efficiency of CCPC lens itself is determined to be 69.33%. With reference to the output current of the MJSC module without a CCPC lens, an optical concentration ratio of 4.65 is observed in the simulated result. An indoor experiment has been performed to validate the simulated result, in which an effective optical concentration ratio of 4.57 has been obtained via laboratory measurement. The experimental result is matched well with the simulated result and it shows that the CCPC module has an effective optical efficiency of 76.17% as the geometrical concentration ratio of the CCPC lens is 6.00. The detailed study of CCPC module is good for optimizing the performance of the UHCPV system.

An evaluation study of miniature dielectric crossed compound parabolic concentrator (dCCPC) panel as skylights in building energy simulation

The potential of miniature dielectric crossed compound parabolic concentrator (dCCPC) panel as skylights for daylighting control has drawn a considerable research attention in the recent years, owing to its feature of variable transmittance according to the sun position, but the viability of using it as skylights in buildings has not been explored yet comprehensively. This paper aims to study the feasibility of utilizing miniature dCCPC panel as skylight in different locations under various climates in terms of energy saving potential besides its daylighting control function. The transmittance of dCCPC panel varies at every moment according to the sky condition and sun position. Due to this specific property, this study novelly implemented a polynomial formula of the dCCPC transmittance in the Grasshopper platform, from which EnergyPlus weather data can be called to calculate the hourly transmittance data of dCCPC skylight panel throughout the whole year. An hourly schedule of transmittance is generated according to the hourly sky condition determined by the daylight simulation through Radiance and Daysim, and is then input to EnergyPlus simulation to predict the energy consumption of a building with dCCPC skylight. Fourteen locations around the world are therefore compared to find the most appropriate place for using miniature dCCPC panel as skylights. The energy saving in cooling, heating and lighting with use of dCCPC skylight panel are investigated and compared with low-E and normal double glazing. The results show that the dCCPC skylight panel can reduce cooling load by mitigating solar heat gain effectively although its performance is affected by several criteria such as sky conditions and local climates. It is generally more suitable for the locations with longer hot seasons, e.g., Log Angeles, Miami, Bangkok and Manila, in which dCCPC could provide up to 13% reduction in annual energy consumption of building. For the locations having temperate and continental climates like Beijing, Rome, Istanbul and Hong Kong, a small annual energy saving from 1% to 5% could be obtained by using dCCPC skylight panel.

Design and Fabrication of Absorptive/Reflective Crossed CPC PV/T System

A crossed compound parabolic concentrator (CCPC) is a non-imaging concentrator which is a modified form of a circular 3D compound parabolic concentrator (CPC) obtained by orthogonal intersection of two 2D CPCs that have an optical efficiency in line with that of 3D CPC. The present work is about the design and fabrication of a new generation of solar concentrator: the hybrid photovoltaic (PV)/thermal absorptive/reflective CCPC module. The module has a 4× CCPC structure truncated to have a concentration of 3.6× with a half acceptance angle of 30°. Furthermore, an experimental rig was also fabricated to test the performance of the module and its feasibility in real applications such as building-integrated photovoltaic (BIPV). 3D printing and Computer Numerical Control (CNC) milling technologies were utilized to manufacture the absorber and reflective parts of the module.

A three-point-based electrical model and its application in a photovoltaic thermal hybrid roof-top system with crossed compound parabolic concentrator

A new coupled optical, thermal and electrical model is presented in this study and applied to a concentrating photovoltaic thermal (PV/T) system for predicting the system performance under various operational conditions. Firstly, a three-point-based electrical model and a method for extracting its five model parameters are developed by using the currents and voltages at the short-, open-circuit and maximum power points provided in usual PV module/panel datasheets. Then, the model and method are validated with the existing six flat-plate PV modules and subsequently are used to predict the hourly electrical performance of the CPV/T roof-top system designed by us under outdoor conditions on four clear days by integrating with a scaling law developed by us. Additionally, transient effect and water temperature on the storage tank are examined. It turned out that the CPV system could operate for 6 h a day with a peak instant electrical power of 50W/m2 and could generate 0.22kWh/m2 electricity a day in May–July. The error in hourly electrical energy gained between the predictions and observations is in a range of (3.64–8.95)% with the mean of 5.53% in four days, and the estimated water temperature in the storage tank agrees with the monitored one in range of 0.2–1 °C. The proposed methods as well as the electrical models could potentially be applied widely across the solar energy field for the management and operation of the electrical energy production from any CPV/T roof-top system.

Conjugate refractive–reflective based building integrated photovoltaic system

Building Integrated Concentrating Photovoltaic (BICPV) systems make use of optical elements to concentrate the incoming solar radiation on small-sized solar cells with the aim of integrating PV technology into the building. We present a novel conjugate system designed to utilize the merits of both reflective and refractive optics. The optical geometry under study is a dielectric based three-dimensional cross compound parabolic concentrator (3DCCPC) enveloped by a reflective geometry of similar shape whilst maintaining an air gap between them. Monte Carlo ray-trace simulations are used to model and optimize the system configuration. The theoretical analysis shows that the optical performance of the system can be improved by 11% whilst maintaining an air gap of 0.1 mm between the reflective and the refractive surfaces. Experiments are carried out by making a prototype of the proposed system to evaluate the proof of concept. A maximum power ratio of 2.76 was found under standard testing conditions at an incidence angle of 10°. Results show that the average power output from the proposed system increases by 5.46% compared to its predecessor.

Parametric optimization and performances analysis of four secondary optical elements for concentrator photovoltaic systems

t he study concerns a general, parametric and performances analysis of four secondary optical elements (SOE) to use for Concentrator Photovoltaic Systems (CPV) using the same primary optic element: the Fresnel lens (FL). It concerns the Compound Parabolic Concentrator (CPC), the Crossed Compound Parabolic Concentrator (CCPC), the Cone and Pyramid. The study starts from optical modeling and considers several classical materials, with various refractive indexes in order to get a clear idea about their influences on the efficiencies, the sizes and the geometrical needs of the SOEs. The performances of the whole concentrator systems are compared in term of achieved effective concentrations, acceptance angles, output light power distribution and tolerances in the placement of the secondary element regarding the FL. Based on the etendue law, the geometrical considerations reveal that the length and the input aperture size of the whole SOEs increase with the increase of the refractive index of the considered material. Results show that the pyramid-based concentrator gives the more uniform irradiance distribution and the high optical efficiency whatever the used material, and the largest tolerance angle never reported. At the end, to easiest the comparison of the four elements, a merit graph is developed and proposed

Multiple nonlinear regression model for predicting the optical performances of dielectric crossed compound parabolic concentrator (dCCPC)

As a typical type of three-dimensional compound parabolic concentrator (CPC), dielectric crossed compound parabolic concentrator (dCCPC) has drawn a significant research attention in these years to explore its angular characteristics in solar collection for concentrating photovoltaics and daylighting control in buildings. Optical efficiency and transmittance are the main performance indicators to evaluate a dCCPC which may be base-coated as a receiver or non-coated for daylighting. The most common way to accurately determine the performance of a dCCPC is through ray-tracing simulation which requires advanced optical analysis software and lots of time. To facilitate the annual performance evaluation of dCCPC, this study puts forward several mathematical models for multiple nonlinear regression based on a mass of simulation results. The models can predict the transmittance of non-coated dCCPC and the both of transmittance and optical efficiency of base-coated dCCPC from several sky parameters, respectively. The agreement between predicted and simulated values is generally satisfactory. The coefficient of determination (R2) for each model is higher than 0.94 and the mean square error (MSE) is less than 0.002. Six specific time among the whole year are selected to verify the reliability of the prediction models in practice. The limitation and significance of these models are discussed as well. The regression models provide a convenient and accurate approach to predict the optical performance of dCCPC.

Design optimization of ultra-high concentrator photovoltaic system using two-stage non-imaging solar concentrator

This paper presents a systematic approach for optimizing the design of ultra-high concentrator photovoltaic (UHCPV) system comprised of non-imaging dish concentrator (primary optical element) and crossed compound parabolic concentrator (secondary optical element). The optimization process includes the design of primary and secondary optics by considering the focal distance, spillage losses and rim angle of the dish concentrator. The imperfection factors, i.e. mirror reflectivity of 93%, lens’ optical efficiency of 85%, circumsolar ratio of 0.2 and mirror surface slope error of 2 mrad, were considered in the simulation to avoid the overestimation of output power. The proposed UHCPV system is capable of attaining effective ultra-high solar concentration ratio of 1475 suns and DC system efficiency of 31.8%.

A scaling law for monocrystalline PV/T modules with CCPC and comparison with triple junction PV cells

Scaling laws serve as a tool to convert the five parameters in a lumped one-diode electrical model of a photovoltaic (PV) cell/module/panel under indoor standard test conditions (STC) into the parameters under any outdoor conditions. By using the transformed parameters, a current-voltage curve can be established under any outdoor conditions to predict the PV cell/module/panel performance. A scaling law is developed for PV modules with and without crossed compound parabolic concentrator (CCPC) based on the experimental current-voltage curves of six flat monocrystalline PV modules collected from literature at variable irradiances and cell temperatures by using nonlinear least squares method. Experiments are performed to validate the model and method on a monocrystalline PV cell at various irradiances and cell temperatures. The proposed scaling law is compared with the existing one, and the former exhibits a much better accuracy when the cell temperature is higher than 40°C. The scaling law of a triple junction flat PV cell is also compared with that of the monocrystalline cell and the CCPC effects on the scaling law are investigated with the monocrystalline PV cell. It is identified that the CCPCs impose a more significant influence on the scaling law for the monocrystalline PV cell in comparison with the triple junction PV cell. The proposed scaling law is applied to predict the electrical performance of PV/thermal modules with CCPC.

A coupled optical-thermal-electrical model to predict the performance of hybrid PV/T-CCPC roof-top systems

A crossed compound parabolic concentrator (CCPC) is applied into a photovoltaic/thermal (PV/T) hybrid solar collector, i.e. concentrating PV/T (CPV/T) collector, to develop new hybrid roof-top CPV/T systems. However, to optimise the system configuration and operational parameters as well as to predict their performances, a coupled optical, thermal and electrical model is essential. We establish this model by integrating a number of submodels sourced from literature as well as from our recent work on incidence-dependent optical efficiency, six-parameter electrical model and scaling law for outdoor conditions. With the model, electrical performance and cell temperature are predicted on specific days for the roof-top systems installed in Glasgow, Penryn and Jaen. Results obtained by the proposed model reasonably agree with monitored data and it is also clarified that the systems operate under off-optimal operating condition. Long-term electric performance of the CPV/T systems is estimated as well. In addition, effects of transient terms in heat transfer and diffuse solar irradiance on electric energy are identified and discussed.

Prototype of Dense-array Concentrator Photovoltaic System Using Non-imaging Dish Concentrators and Cross Compound Parabolic Concentrator

Abstract The paper presents a novel dense-array concentrator photovoltaic prototype system consisted of primary non-imaging dish concentrator and secondary concentrator (an array of crossed compound parabolic lenses). The secondary optics has a geometrical concentration ratio of 5.998 but the average measured concentration ratio is only 4.07 suns. The losses are mainly attributed to both the Fresnel reflection at the interfaces and absorption of the dielectric material. The preliminary measured power conversion efficiency of the system is 17% due to significant optical loss incurred by the secondary concentrator.