Compound Parabolic Concentrator Research Articles

Evaluation of Heat Flux Distribution on Flat Plate Compound Parabolic Concentrator With Different Geometric Indices

AbstractThe Compound Parabolic Concentrator (CPC), when coupled with the photovoltaic system, namely the Concentrated Photovoltaic Thermal System (CPVT), makes utilizing solar energy efficient. The major challenge that hinders the electrical and thermal performance of the CPC–CPVT system is the non-uniform heat flux distribution on the absorber surface. In the present paper, detailed ray-tracing simulations have been carried out to understand the heat flux distribution characteristics of CPC with different geometrical conditions, and those are concentration ratio, truncation ratio, incident angle, and average heat flux on the absorber surface. To have a thorough understanding, the analysis has been carried out in multiple steps. First, it is performed by analyzing the effect of concentration ratio and incident angle on heat flux distribution characteristics at a fixed truncation ratio. Second, investigations have been carried out to understand the heat flux distribution characteristics at different truncation ratios and different incident angles by keeping the concentration ratio constant. Local concentration ratio and non-uniformity index have been employed to quantify the non-uniformity of heat flux distribution on the absorber surface. It has been observed that the 0-deg incidence angle is the most effective angle to achieve uniform heat flux distribution on the absorber surface. This paper sheds insight into the heat flux distribution characteristics on the absorber surface of a CPC–CPVT system which can be used by the research community for designing an effective CPVT system from the perspective of uniform heat flux distribution on the absorber surface.

Preliminary study on photo-thermal conversion investigation of compound parabolic concentrator for eliminate light escape in vacuum tube interlayer

The ELE-CPC (Eliminate Light Escape Compound Parabolic Concentrator, ELE-CPC) system with vacuum tube absorber is constructed to solve the problem of light escaping in the vacuum interlayer when the conventional vacuum tube absorber is coupled to CPC. The solar ELE-CPC photo-thermal conversion model is established theoretically, and the reliability of the model is validated by outdoor experiments. It is found that the average output temperature of ELE-CPC system is 366.4 K, the average thermal efficiency is 61.3%, and the maximum relative error of the theoretical model is less than 13.2%. The thermal collection efficiency of the ELE-CPC system improves with the increase of its flow rate. Evaluation of the operating characteristics of ELE-CPC showed that the useful energy obtained by ELE-CPC increased throughout the year, especially in April, the average daily utilized solar energy obtained by ELE-CPC increased by 6.9% compared with S-CPC (Standard CPC, S-CPC). Solar ELE-CPC system with such heat collection performance has a good application prospect in the fields of material drying, building heating, seawater desalination and so on.

Performance assessment of double pass photovoltaic/thermal solar air collector using bifacial PV with CPC and mirror reflector under Malaysian climate

The performance of photovoltaic thermal (PV/T) type solar collectors can be optimised with the use of bifacial photovoltaic panel since it can utilise the absorbed incident solar irradiance from its front and rear surface. However, its potential is highly determined by the amount of the reflected solar irradiance onto the rear surface of the panel. In this research, we assessed the potential of a novel double pass photovoltaic/thermal (PV/T) solar air collector using semi-transparent bifacial PV panel with compound parabolic concentrator and mirror reflector in Malaysia. The use of CPC and reflector was introduced to increase the amount of reflected light and hence increasing the efficiency of the collector. A mathematical model was developed, and validated o predict the performance of the solar collector. Using the validated mathematical model, the optimum mass flow rate of the bifacial PV/T collector with CPC and mirror reflector was found at 0.0589 kg/s. At this flow rate, when operated under the hot climate of Malaysia, the temperature output of as high as 51 °C is achievable implying its potential as a preheated air to regenerate desiccant materials in solar assisted cooling system and for agriculture drying application. Also, when compared with the bifacial PV/T solar collector without the CPC, the total energy useful was found almost 40% higher.

A new solar mid-and-low temperature receiver/reactor with linear Fresnel reflector

The hydrogen production by a mid-and-low temperature solar receiver/reactor traditionally uses a parabolic trough collector, where the circumferential non-uniformity of the concentrated solar flux poses a challenge to the safety of the catalyst bed and absorber tube. To address this challenge, this study proposes a new hydrogen production method that allows for a more uniform distribution of solar flux, temperature, and deformation in the receiver/reactor by combining a linear Fresnel reflector, a compound parabolic concentrator, a mid-and-low temperature receiver/reactor, and methanol steam reforming reaction. The solar light is concentrated on the surface of the receiver/reactor by the linear Fresnel reflector and the compound parabolic concentrator instead of the traditional parabolic trough collector, and then converted into chemical energy by the methanol steam reforming reaction in the receiver/reactor. A three-dimension model is established to study the performance of the mid-and-low temperature receiver/reactor, including solar flux distribution, fluid flow, mass diffusion, heat transfer, chemical reaction, and structural deformation. The influences of key factors are studied, including the inlet temperature, feeding rate of reactants, molar ratio of water to methanol, and porosity of the catalyst bed. A comparative study between linear Fresnel reflector and parabolic trough collector is conducted to discover the influence of the light-concentrating methods on hydrogen production. The results show that the temperature and reaction fields are highly influenced by the circumferential distribution of the solar flux. The linear Fresnel reflector can achieve a more uniform temperature distribution along the cross-section in the flow direction than the parabolic trough collector owing to the more uniform distribution of solar flux. The maximum temperature difference of the absorber tube in the center of the absorber tube is 12.5 % of that in the parabolic trough collector, which effectively alleviates the local overheating of the catalyst and decreases the thermal deformation of the steel tube. This study provides a reference for the mid-and-low temperature hydrogen production in the linear Fresnel reflector.

The development of a new thermal modeling and heat transfer mechanisms of a compound parabolic concentrator (CPC) based on nanofluids

The development of a new thermal modeling and heat transfer mechanisms of a compound parabolic concentrator (CPC) based on nanofluids

An estimation of bio-methane generation from photovoltaic thermal compound parabolic concentrator (PVT-CPC) integrated fixed dome biogas digester

An estimation of bio-methane generation from photovoltaic thermal compound parabolic concentrator (PVT-CPC) integrated fixed dome biogas digester

Performance Simulation of Solar Trough Concentrators: Optical and Thermal Comparisons

The solar trough concentrator is used to increase the solar radiation intensity on absorbers for water heating, desalination, or power generation purposes. In this study, optical performances of four solar trough concentrators, viz. the parabolic trough concentrator (PTC), the compound parabolic concentrator (CPC), the surface uniform concentrator (SUC), and the trapezoid trough concentrator (TTC), are simulated using the Monte Carlo Ray Tracing method. Mathematical models for the solar trough concentrators are first established. The solar radiation distributions on their receivers are then simulated. The solar water heating performances using the solar trough concentrators are finally compared. The results show that, as a high-concentration ratio concentrator, the PTC can achieve the highest heat flux, but suffers from the worst uniformity on the absorber, which is only 0.32%. The CPC can generate the highest heat flux among the rest three low-concentration ratio solar trough concentrators. Compared with the PTC and the CPC, the TTC has better uniformity, but its light-receiving ratio is only 70%. The SUC is beneficial for its highest uniformity of 87.38%. Thermal analysis results show that the water temperatures inside the solar trough concentrators are directly proportional to their wall temperature, with the highest temperature rise in the PTC and the smallest temperature rise in the TTC. The solar trough concentrators’ thermal deformations are positively correlated to their wall temperatures. The radial deformation of the SUC is much larger than those of other solar trough concentrators. The smallest equivalent stress is found in the SUC, which is beneficial to the long-term operation of the solar water heating system.

A New Two-Foci V-Trough Concentrator for Small-Scale Linear Fresnel Reflectors

We present the design of an original secondary cavity for use in Small-Scale Fresnel Reflectors in photovoltaic applications. The cavity is similar to the classical V-trough, but the primary reflector system is configured so that there are two focal points on the aperture. The rays coming from each side of the primary system reach the opposite side of the cavity, producing a non-symmetrical distribution of the irradiance. This modifies the acceptance half-angle and allows us to break the maximum limit for the concentration ratio of ideal symmetric concentrators. Our study is analytic, and we provide formulas for any number of reflections. Numerical simulations with a ray-tracing program based on MATLAB are included. We provide a comparison of optical concentration ratio, height and cost parameter between our system and two classical designs with a single focal point: the V-trough and the Compound Parabolic concentrators. This way, we verify that our design yields better concentration ratios while keeping the ray acceptance rate at one. Our solution proves to be better than both the classical one-focus V-trough and the Compound Parabolic concentrator. Specifically, the proposed solution is significantly better than the classical one-focus V-trough in optical concentration ratio, with an increase between 15.02 and 35.95%. As regards the compound parabolic concentrator, the optical concentration ratio is always slightly better (around 4%). The height of the cavity, however, is notably less in this design (around 54.33%).

Enhanced electron acceleration by high-intensity lasers in extended (confined) preplasma in cone targets

We report on experimental results from a high-intensity laser interaction with cone targets that increase the number (×3) and temperature (×3) of the measured hot electrons over a traditional planar target. This increase is caused by a substantial increase in the plasma density within the cone target geometry, which was induced by 17 ± 9 mJ prepulse that arrived 1.5 ns prior to the main high intensity (>1019 W/cm2). Three-dimensional hydrodynamic simulations are conducted using hydra which show that the cone targets create substantially longer and denser plasma than planar targets due to the geometric confinement of the expanding plasma. The density within the cone is a several hundred-micron plasma “shelf” with a density of approximately 1020 ne/cc. The hydra simulated plasma densities are used as the initial conditions for two-dimensional particle-in-cell simulations using EPOCH. These simulations show that the main acceleration mechanism is direct-laser-acceleration, with close agreement between experimentally measured and simulated electron temperatures. Further analysis is conducted to investigate the acceleration of the electrons within the long plasma generated within a compound parabolic concentrator by the prepulse.

Indoor Performance Analysis of a Novel Double-Pass photovoltaic/thermal (PV/T) Asymmetric Compound Parabolic Concentrator (ACPC) Solar Collector

A photovoltaic/thermal (PV/T) solar collector combines solar photovoltaic (PV) modules and solar thermal that operates simultaneously to generate electricity and thermal energy. Design parameters, operating conditions and environmental factors all have a significant impact on the performance of a PV/T solar collector. This research investigates the influence of the variation in the air mass flow rate to the performance of a novel double-pass photovoltaic/thermal (PV/T) asymmetric compound parabolic concentrator (PV/T-ACPC) solar collector. To investigate performance of the solar collector, it was tested indoors using a solar simulator at average solar radiation of 800 W/m2 with the variation in the air mass flow rate ranging from 0.0074 kg/s to 0.0900 kg/s. From the analysis, we found that as the air mass flow rate increases, the thermal efficiency and electrical efficiency increases from 37.15 % to 60.51 %, and 2.51 % to 3.29 % respectively. Meanwhile while the difference in the air output temperature and PV panel temperature were found to decrease from 19.64 °C to 2.63 °C, and 66.83 °C to 41.86 °C respectively. We also found that, as the mass flow rate continues to increase, it will reach its ‘optimum point’ and approaching a plateau at mass flow rate of 0.0262 kg/s. The finding is crucial since the collector needs to be operated at its optimum flow rate to ensure optimum efficiencies at the optimum temperature rise of the useful air supply.

Life cycle greenhouse gas emissions of low-temperature process heat generation by external compound parabolic concentrator (XCPC) solar thermal array

New solar-based technologies are currently being developed as prospective low-carbon sources of heat for industry, which require life cycle assessment to determine their actual decarbonization potential relative to current heat sources. We performed the first life cycle assessment of the external compound parabolic concentrator (XCPC) solar array, a novel low-concentration and non-tracking solar thermal technology capable of providing low-to medium-temperature heat (up to 250 °C). Primary data on the materials and performance of the XCPC were used in this analysis. The embodied greenhouse gas (GHG) emissions associated with manufacturing the technology are 92.4 kg CO2eq/m2, cradle-to-gate. The life cycle GHG emissions cradle-to-grave over a 25-year lifetime under conditions in the Central Valley of California are 129.7 kg CO2eq/m2. On the basis of thermal energy delivered, the XCPC has a carbon footprint of 5.8 g CO2eq per kWhth. These results indicate that the XCPC can generate low temperature heat with a carbon footprint 97% lower than natural gas and 98% lower than propane combustion in regions of high solar insolation.

Construction and concentrating performance of a critically truncated compound parabolic concentrator without light escape

Conventional solar CPC (Compound Parabolic Concentrator, CPC) has a limited collection of solar radiation at the end of the concentrating surface, which is not conducive to its wide application. In the present research, a solar CT-CPC (Critically Truncated CPC, CT-CPC) without light escape is proposed and constructed for the vacuum tube absorber, and discusses its optical properties, which provides a choice for improving or reforming the existing CPC system. Based on the edge ray principle, the geometric model of the CT-CPC is designed by the dichotomy method, and the concentrating performance of the CT-CPC is verified by the adjustable laser experiment. The study found that the average optical efficiency of CT-CPC reaches 47.84% and is 7.2% higher than the traditional S-CPC (Standard CPC, S-CPC) without light escape at the same aperture, and the energy flux distribution on the absorber surface is also more uniform, which is beneficial to improving system efficiency. The effective working hours of CT-CPC is higher than the S-CPC in the whole year, and the average effective working hours is 8.8 h and 5.7 h, respectively. The total annual radiation collection of CT-CPC is 3397 MJ/m2, which is 11.2% higher than the S-CPC. Furthermore, the economic analysis shows that solar CT-CPC has significant advantages and more friendly engineering application potential.

Experiment of a novel collector design with concentrators and heat storage cores

Combining the compound parabolic concentrator, phase change heat storage cores and vacuum tube solar air collector, a novel solar collector with both heat storage function and concentrating effect was proposed in this paper. Theoretical analysis and experimental investigation were used to illustrate the heat transfer principles and thermal performance of the novel collector. The results indicate that this type of collector not only increased the heat-collecting temperature and efficiency compared to the general solar collector, but also extended the heating time: the maximum output temperature could be improved by 4.5 °C (110.8 °C), maximum transient efficiency could be increased by 12.09 % (73.09 %) and heating time could be extended by approximately 3 h during the day. This study can provide a reference for the future research of multi-technology integrated collectors.

Simulation and Experimental Evaluation of a Refractive-Reflective Static Solar Concentrator

Static solar devices have advantages over solar tracking systems. In pure reflective systems, solar reception is limited by the entry angle of the reflector. Many reflective systems are based on mirror Compound Parabolic Concentrators. The solar collection can be improved by placing a lens on top of the reflector. In this work, a static system is proposed, consisting of a mirror funnel concentrator with a prism on top. The system is designed using ray-tracing software and is subsequently built and experimentally evaluated. The system designed for an effective concentration factor of 4× reaches an effective concentration of 3.2× at 11:30 a.m. and has an acceptance angle of 60°. Considering the time interval from 8 a.m. to 4 p.m., the system harvests 30.7% more energy than the flat surface. If the time interval considered is from 9:30 a.m. to 2:30 p.m., the increase in harvest is ∼77%. The incorporation of the prism represents an increase of ∼6% compared to the bare reflective system.

Novel Algorithm for Improving Tracking Accuracy of Open-Loop Mobile Sun-Tracking System via Different Timing Control Scheme

This paper proposes a mobile sun-tracking (MST) system to track the sun on the moving vehicle. We have developed a novel MST algorithm using general sun-tracking formulas associated with simple-moving average linear regression (SMALR) to smoothen sun-tracking activity. Furthermore, two different timing control schemes to activate sun tracking are investigated: time lapse (TL) mode and azimuth actuation (AA) mode. For experimental validation, a prototype of MST has been constructed on a small truck moving at constant speed of 30 km/h for field measurements. For the result, AA mode has average pointing error of 110 mrad for the open-loop tracking design (13% better than that of TL mode), which is still far below the half acceptance angle of compound parabolic concentrator at 659 mrad. Since there is no feedback sensor to be implemented in this prototype, optical encoders and CCD camera can be employed in the future work to further reduce the pointing error of MST system.

Improvement of uniformity of irradiance on truncated compound parabolic concentrator by introducing the homogenizer ratio

A compound parabolic concentrator (CPC) with a flat absorber is widely used in low-concentrating photovoltaic thermal (CPVT) systems. CPC certainly develops non-uniform heat flux distribution over the absorber surface which is significantly reduced by the integration of homogenizer referred as Elongated CPC (ECPC). The objective of the present work is to analyse the effect of homogenizer ratios, truncation ratios and concentration ratios on the heat flux distribution characteristics of a CPC collector. In this paper, a ray tracing simulation is carried out to obtain the heat flux distribution profiles and the same is incorporated within CFD software to obtain the temperature distribution profiles. As a result, it is observed that the optimum truncation ratio would be 0.7 at which uniformity in flux distribution is improved by 3%, with just 2% reduction of average heat flux value. Furthermore, with optimized homogenizer ratio of −0.35 at concentration ratio of 3, 64% improvement in uniformity of flux distribution has been noticed. From the study, it has been concluded that for different concentration ratios of 1.5, 2, 3, 4, 5, 6, 7 and 8, the optimum homogenizer ratio is observed to be −0.9, −0.55, −0.35, −0.25, −0.2, −0.15, −0.15 and −0.05 respectively.

A solar photoFenton process with calcium peroxide from eggshell and ferrioxalate complexes for the degradation of the commercial herbicide 2,4-D in water

The present study focused on the degradation of the commercial herbicide 2,4-D in water by solar photoFenton assisted with ferrioxalate complex and calcium peroxide (CaO2), using an experimental system consisting of a storage tank, a water pump, a solar reactor, and a compound parabolic concentrator (CPC), which collected solar energy of 212.102 kJ/L. The CaO2 was synthesized from eggshells, the influence of the 2,4-D concentration, oxalic acid (H2C2O4), iron (Fe3+), and CaO2 on the degradation of herbicide was evaluated by HPLC, and the intermediates such as 2,4-dichlorophenol, 1,4-benzoquinone, and oxalic acid were determined to confirm the proposed reaction mechanism. The generation of hydroxyl radicals and other reactive species, depends on the molar ratios of oxalate/Fe3+, CaO2/Fe3+, and CaO2/2,4-D. The optimum concentrations for 100 % degradation were 61.5 mg/L 2,4-D, 50.5 mg/L Fe3+, 100.5 mg/L H2C2O4, and 81 mg/L CaO2 with 42.27 % COD and 44.09 % TOC. This study highlights the viability of the solar photoFenton process to degrade the 2,4-D herbicide and aims to promote: the recovery of organic waste such as eggshells, the complexing effect of H2C2O4-Fe3+, the CaO2 as an alternative oxidant, and the application of renewable energy in the treatment of similar contaminants present in wastewater for future research.

Investigation of photo-thermal performance of compound parabolic concentrator system for soil heating in facility agriculture

Aiming at the large carbon emissions of facility agricultural heating in severe cold regions in winter, a compound parabolic concentrator based soil heating system was presented. The system integrated with novel trough compound parabolic concentrator and was used for soil heating in facility agriculture. Following the structure of the compound parabolic concentrator, TracePro software was selected to trace the light in the compound parabolic concentrator. The variation trend of the light escape rate of the compound parabolic concentrator with the different incident angles was analyzed. Based on the calculation results, the performance of the solar collector system was investigated, and the impact of circulating air velocity on the photo-thermal performance of the solar collector system was explored. Research results indicate that when the circulating air velocity is 1.4 m/s and the average ambient temperature is about 28.9?, the temperature of the system outlet is up to 90.9?. The average instantaneous heat collection, maximum photo-thermal conversion efficiency, and unit area heat collection of the system are 740.6 W, 27.83%, and 0.8 MJ/m2, respectively. This research can effectively promote the efficient integration of the solar collector system in facility agriculture.

Development of a bright MeV photon source with compound parabolic concentrator targets on the National Ignition Facility Advanced Radiographic Capability (NIF-ARC) laser

Compound parabolic concentrator (CPC) targets are utilized at the National Ignition Facility Advanced Radiographic Capability (NIF-ARC) laser to enhance the acceleration of electrons and production of high energy photons, for laser durations of 10 ps and energies up to 2.4 kJ. A large enhancement of mean electron energy (>2 ×) and photon brightness (>10×) is found with CPC targets compared to flat targets. Using multiple diagnostic techniques at different spatial locations and scaling by gold activation spatial data, photon spectra are characterized for Ephoton=0.5–30 MeV. Beam width and pointing variations are given. The efficient production of MeV photons at Ilaser≈2×1018 W/cm2 with CPCs is observed, with doses of >10 rad in air at 1 m for Ephoton>0.5 MeV; these exceed those previously reported with laser-driven sources. Using this source, sub-mm resolution radiographs are generated through large areal density radiograph objects. These results are promising for the development of bright MeV x-ray and particle sources on Petawatt class laser systems.

Concatenated Backward Ray Mapping on the Compound Parabolic Concentrator

Concatenated backward ray mapping is an alternative for ray tracing in 2D. It is based on the phase space descrip tion of an optical system. Phase space is the set of position and direction coordinates of rays intersecting an optical line. The original algorithm is limited to optical systems consisting of only straight line segments; we extend it to accommodate curved segments. The algorithm is applied to the compound parabolic concentrator, a standard optical system that collects parallel light and reshapes it to a focused beam. We compare the accuracy and speed of the extended algorithm to the original algorithm and Monte Carlo ray tracing. The results show that the extended algorithm outperforms both methods.