Compound Parabolic Concentrator Research Articles

Combining high power laser modules with compound parabolic concentrators to test components at high heat fluxes

Assessing the performance and lifetime of components is a key step towards deploying new technologies in the aerospace and fusion sectors. Experimental testing at representative thermal conditions is particularly important when investigating novel materials that have yet to be fully characterized. This paper presents the key features of a new high-power laser facility developed to test components destined for extreme environments.This facility, OLAHF (Oxford LAser Heating Facility), provides a maximum power of 24 kW over an area of 200 mm by 104 mm for a base intensity of 1.15 MW/m2 via a combination of laser modules. A bespoke control system manages the laser and instrumentation systems as well as supporting cooling air and water infrastructure. A numerical model of the lasers is validated against supplier data, enabling high fidelity computational representation of experimental setups.Compound parabolic concentrators (CPCs) are investigated to increase applied laser power over smaller testing surfaces. A laser module-CPC system assessed the performance of gold and aluminum coatings at a range of surfaces roughnesses. High transmission efficiencies were demonstrated when surfaces are gold coated and below 0.1μm average roughness. Future plans for OLAHF are additionally presented, including additional test campaigns using higher power CPC systems.

Experimental study on a compact solar driven two-stage humidification-dehumidification desalination system with shared dehumidifier

The low-cost and low-grade solar driven humidification-dehumidification desalination is considered a promising process for small and medium capacity freshwater production. Nevertheless, the enhancement of the unit volume water production rate is hindered by the disparity in mass transfer coefficient and the incongruity between heat and mass flow rate in the humidification and dehumidification process. This paper proposes a compact solar driven two-stage humidification-dehumidification desalination system with shared dehumidifier. It contains two humidifiers and a dehumidifier, wherein the dehumidifier is stacked between the vertically placed humidifiers. The circulating air is humidified by hot seawater in the top and bottom humidifiers respectively, and then goes to the middle dehumidifier to condense via a freshwater absorption process. Its design scheme and operating principle are introduced and a mathematical model describing its internal energy and mass flow process is established. An experimental setup with compound parabolic concentrator areas of 6 m2 is developed, and a sequence of experiments is carried out. The results indicate that its freshwater productivity can reach 29.6 kg/h with a gained output ratio of 0.84 when the feed seawater temperature is 80 ℃. Due to its compact structure, the freshwater production per volume unit per day reaches up to 224.1 kg/(day⋅m3). This work may promote the development of solar humidification and dehumidification systems towards low cost and high efficiency.

Optical performance investigation for spatially separated non-imaging concentrator with congruent plane concentrating surface

The thermal deformation on the concentrating surface of traditional CPC (Compound Parabolic Concentrator, CPC) is effectively addressed by SCSA-CPC (Separation of Concentrating Surface and Absorber CPC, SCSA-CPC). However, the energy flux density distribution on the absorber of SCSA-CPC is uneven and the concentrating surface is still a curved paraboloid structure, which hinders practical engineering applications and lacks significant economic benefits. In the present research, five kinds of SS-CPCs (Spatially Separated CPC, SS-CPC) with different numbers of congruent plane concentrating surfaces, namely SS-CPC2, SS-CPC3, SS-CPC4, SS-CPC5 and SS-CPC6 were constructed based on non-imaging optics principles. The optical performances of the SS-CPCs were investigated and compared to SCSA-CPC with the same specification. It is found that SS-CPC allows for an increased acceptance angle of up to 41° while effectively improving the uniformity of energy flux density distribution on the absorber. The results also showed that the annual beam radiation collection time can be extended by 43.11 % and SS-CPC has a particular advantage in collecting diffuse radiation, indicating its high adaptability to weather changes. Moreover, due to the congruent planar structure of the concentrating surface, SS-CPC holds promising prospects for practical engineering applications.

Development of characteristic equations of conical solar still by incorporating N identical concentrator collectors with/without photovoltaic panel: A comparative investigation

This paper focuses on the development of characteristic equations and performance analysis of a conical solar still (CSS) connected to N identical compound parabolic concentrator (CPC) collectors, with or without photovoltaic thermal (PVT) integration. The objective is to achieve sustainable solar distillation in line with the United Nations' sustainability goals. The thermal model is developed by formulating energy balance equations for each part followed by its experimental validation considering N=0and1. A fair agreement between analytical and experimental results is observed having correlation coefficients as 0.996, 0.993, 0.992, and 0.97, 0.98, 0.99 for water temperature, yield, and glass temperature for N = 0 and 1, respectively. The study considers three cases: CSS integrated with N identical partially covered PVTCPCs (case (i)), CSS integrated with N identical fully covered PVTCPCs (case (ii)), and CSS integrated with N identical CPCs (case (iii)). The performance of these cases is compared using climate conditions in New Delhi on a typical day in June. The findings indicate that the mean value of instantaneous efficiency for case (i) is higher by 67.75 % than case (ii), however lower by 22.22 % than case (iii). The study also investigates the influence of variations in mass-flow rate and N on the output of the active CSS.

Assessing performance of an external compound parabolic concentrator solar collector with cascaded latent heat thermal storage

AbstractThis study presents quantitative results of charging experiments conducted on cascaded thermal energy storage system (CTESS) integrated with external compound parabolic concentrator solar collector (XCPCSC). Increasing mass flow rate in 2‐stage CTESS integrated with XCPCSC resulted in a 30% reduction in initiation time of phase change materials (PCMs) during charging, with a higher mass flow rate of 0.025 kg/s. However, due to disparate melting point temperatures of PCMs, phase transition in the two‐stage CTESS did not occur simultaneously, leading to poor heat transfer rates within the CTESS. To address this, study extended number of phases from two to three, resulting in a 1.5‐fold increase in rate of heat transfer compared to 2‐stage PCM system. The simultaneous melting processes at various stages in the CTESS maximized energy absorption, leading to a 25% increase in system efficiency. Notably, the values of energy stored efficiency and over‐all efficiency reached their peak values of 95% and 60%, respectively, between t = 12.00 h and t = 13.00 h. This time period also saw a significant increase in collector efficiency to 72%. These quantitative findings highlight importance of mass flow rate and PCM arrangement in achieving efficient heat transfer and system performance in a CTESS integrated with XCPCSC.

A Numerical Case Study of Particle Flow and Solar Radiation Transfer in a Compound Parabolic Concentrator (CPC) Photocatalytic Reactor for Hydrogen Production

Compound parabolic concentrator (CPC) photocatalytic reactors are commonly used for photocatalytic water splitting in hydrogen production. This study aimed to gain a better understanding of the physical processes in CPC photocatalytic reactors and provide theoretical support for their design, optimization, and operation. The analysis involved the ray tracing approach, Euler–Euler two-fluid model, and discrete ordinates method (DOM) to study solar radiation transfer and particle flow in the reactor. The distribution of solar radiation on the receiving tube’s surface after CPC concentration was obtained by conducting the ray tracing approach. This solar radiation distribution was then coupled into the Euler–Euler two-fluid model to solve for the natural convection flow field, the temperature field, and particle phase volume fraction distribution inside the receiving tube over a period of 120 s. Lastly, the discrete ordinates method (DOM) was used to analyze the transfer of radiation inside the receiving tube at different times, obtaining the distribution of local volume radiative power absorption (LVRPA) and the total radiative power absorption (TRPA) inside the tube. The results showed that the TRPA reached its maximum at 120 s, accounting for 66.61% of the incident solar UV radiation. According to the above results, it could be suggested that adopting an intermittent operation mode in CPC photocatalytic reactors is reasonable and efficient.

Comparative exergy and economic analyses of single slope solar desalination unit combined with concentrator integrated evacuated collectors

This paper deals with the exergy analysis of single slope solar desalination unit combined with N number of compound parabolic concentrator integrated evacuated tubular collectors (NCPCETC-SU) considering New Delhi climate. An exhaustive computation considering each month of year is carried out. The methodology consists of feeding all fundamental equations with relevant data to MATLAB code and presenting the output in the suitable form. Results of NCPCETC-SU are compared with results of SU incorporated with evacuated tubular collectors (NETC-SU). Concludingly, the annual exergy and daily exergy efficiency for NCPCETC-SU are higher by 36.51% and 30.81% than NETC-SU for same mass flow rate, N and water depth under similar climatic situation. The annual freshwater output is higher by 16.81% and freshwater cost is higher by 9.85% at 2% rate of interest for NCPCETC-SU than NETC-SU respectively. Further, the freshwater cost of NCPCETC-SU can be diminished by increasing the concentration ratio.

A spectral splitting CPV/T hybrid system based on wave-selecting filter coated compound parabolic concentrator and linear Fresnel reflector concentrator

Efficient full-spectrum solar energy utilization shows great potential to improve solar energy conversion efficiency. In this paper, a spectral splitting concentrated photovoltaic/thermal hybrid system based on a wave-selecting filter-coated compound parabolic concentrator and linear Fresnel reflector mirror field is developed. Optical models to simulate the linear Fresnel reflector have been developed and validated. With the wave-selecting filter coated compound parabolic concentrator, the visible and near infrared spectra transmit onto the photovoltaic cells, while the rest are reflected to the receiver tube. Furthermore, a simplified receiver indoor test prototype is designed to investigate the characteristic of solar photovoltaic module with the spectral filter in the context of the compound parabolic concentrator. The measured I–V curves are compared with the modeled results. Additionally, the thermodynamic performance of the system is analyzed. Parametric studies are performed to investigate the effect of key design parameters including the mirror width, focal length and the radius of the receiver tube on the solar flux density and the exergy efficiency. An exergy efficiency of 35.51% and an optical efficiency of 94.78% are achieved. With a preliminary techno-economic analysis, the levelized cost of the electricity of the system is $0.209/kWh with a payback period of 10 years.

Economic and Performance Analysis of Modified Solar Distillation System Coupling Different Integrations Using Carbon Quantum Dot Nanoparticles: Generalized Thermal Model

Abstract Clean drinking water and electricity production utilizing non-conventional sources of energy is the global demand for sustainable development. Ultrafast heat transfer fluids have delivered impressive results in photovoltaic (PV)-integrated solar thermal systems, in recent times. Efforts have been made for the productivity and electricity augmentation of solar still equipped with helically coilled heat exchanger and coupled with different integrations, viz., (a) partially covered N-photovoltaic thermal compound parabolic concentrator (N-PVT-CPC), (b) partially covered N-photovoltaic thermal flat plate collector (N-PVT-FPC), (c) N-FPC-CPC, and (d) N-flat plate collector (N-FPC). System design has also been modified by adding a roof-top semi-transparent PV module and built-in passive copper condenser (circulation mode), and effect of carbon quantum dots (CQDs) water-based nanofluids, nanoparticles volume concentration, and packing factor (βc) of the PV module has been studied by developing generalized thermal modeling of the system (special cases). Overall, 41.1%, 21.52%, 22.01%, and 10.01% rise in evaporative HTCs is observed in FPC-CPC, PVT-CPC, FPC, and PVT-FPC integrations, respectively. Thermal exergy is found to be higher for FPC-CPC integration, and it follows the enhancement order as FPC-CPC (max-0.147 kW) > PVT-CPC (0.088 kW) > FPC (0.038 kW) > PVT-FPC (0.028 kW). In reference to the base fluid, significant enhancement in the daily productivity is observed for FPC-CPC (10.9%) and PVT-CPC (5.16%) integrations using CQD-NPs. The production cost of potable water has also been estimated for all the cases for n = 30 and n = 50 years life span and i = 4% and 8% interest rates, and it is found to be the lowest (0.014 $/L) for FPC-CPC integration using CQD-NPs (n = 30 years, i = 4%).

Design and development of a novel and cost effective modified Compound parabolic trough collector

In the context of achieving Net Zero targets, the adoption of compound parabolic concentrator (CPC) technology can play a vital role. The purpose of this work is to modify the design of a conventional CPC in such a way that for the same concentration ratio, and for same aperture area, the modified CPC (MCPC) will require significantly less material for its support structure, receiver and reflector: and hence will have reduced cost. The MCPC, we designed, has a concentration ratio of 4 and an acceptance angle 10° and requires position modification only once a month when oriented with its long axis along the East-West direction. We report experiments on an experimental prototype: the solar-to-thermal efficiency of which was 35.7% and cost of which was below $60/m2. This MCPC enables inexpensive and convenient generation of heat applications including driving low temperature industrial process heating, generation of hot water, hot air for drying, space-heating and even cooking. This can directly contribute to meeting Net Zero goals and furthermore address the problem of deforestation due to use of wood for domestic cooking. Also, since the MCPC can be manufactured using technologies available even in semi-urban regions of the Sun-belt, use of the MCPC can also boost local manufacturing economies providing dignified employment opportunities in currently underserved parts of the world.

A novel integration of supplementary photovoltaic module into compound parabolic concentrator for accelerated defrosting of solar collecting system

In order to improve the temperature of solar greenhouse in winter and reduce the cost and energy consumption of traditional heating methods for solar greenhouse. This study presents a novel compound parabolic concentrator (CPC) coupled with a supplementary photovoltaic (SPV) module for soil heating in solar greenhouse. Firstly, a novel SPV-CPC was designed and its optical model was established by TracePro. The optical and thermal performance of the novel SPV-CPC and the traditional CPC under the same conditions were compared. The results indicate that the SPV module can intercept and utilize the escaping rays when the incident angle is large, for example, at the incident angle of 15°, the light receiving ratio of the novel SPV-CPC and traditional CPC are 78.50 % and 61.50 % respectively. In particular, the SPV module can effectively capture rays in early morning of winter to accelerate the defrosting on the glass cover. Under sunny days, the solar heat collection performance of the SPV-CPC is similar to that of the traditional CPC, and their photothermal conversion efficiencies are 54.61 % and 54.05 %, respectively. However, owing to the SPV module, the overall primary-energy saving efficiency of the SPV-CPC is 64.09 %.

Model construction and energy harvesting investigation of shell shaped multi-section compound parabolic concentrator with solar vacuum tube

The solar non-imaging concentrator has the characteristics of no tracking device, stable system structure, and collected beam radiation and diffuse radiation. In particular, the Multi-section Compound Parabolic Concentrator(M-CPC) also has the advantages of a high utilization rate of reflector, long working time, and low manufacturing cost. In present research, a Novel Multi-section Compound Parabolic Concentrator (NM-CPC) is constructed based on the edge ray principle and Monte Carlo ray tracing (MCRT) method for the Shell Shaped Compound Parabolic Concentrator (SS-CPC) horizontally placed. The reliability of the model is verified by visual laser experiments, and its optical performance is analyzed considering the influence of the outer tube glass of the vacuum tube on the ray propagation. Compared to SS-CPC of the same specification, NM-CPC can eliminate the rays that escaped from the vacuum tube interlayer effectively. The heat-absorbing surface has a more uniform energy flux distribution and lower peak of energy flux. In spring and autumn, it has better solar radiant energy harvesting, which is 206 MJ and 297 MJ respectively. In terms of economic performance, the cost of the reflector is saved by 75.5%. All results show that NM-CPC has good application potential and economic performance.

Design and Optical Performance Evaluation of the Three-Dimensional Solar Concentrators with Multiple Compound Parabolic Profiles and Elliptical and Rectangular Receiver Shapes

The compound parabolic concentrator (CPC) is a core technology in the field of solar concentration. Nevertheless, it only has one degree of freedom in the choice of its half-acceptance angle. In this study, extending the idea of the three-dimensional CPC, a design method for new kinds of concentrators having a CPC shape at each profile with various acceptance angles in all directions is proposed. The feature of this method is that the receiver can take any shape. Here, elliptical and rectangular receivers are assumed, and the shape and concentration performance of the concentrators with multiple CPC profiles and an elliptical receiver (MultiPro-ECPCs) and the concentrators with multiple CPC profiles and a rectangular receiver (MultiPro-RCPCs) are derived. The new designs are compared to the conventional CPC and a mirrorless flat receiver through ray-tracing simulations in terms of energy distribution on the receiver, optical efficiency, and optical concentration ratio based on axial and solar angles. The results show that in terms of optical efficiency, the MultiPro-RCPCs cover a wider range of incident angles after the 3DCPC. In terms of the optical concentration ratio, the MultiPro-ECPC with a longitudinal half-acceptance angle of 15° has the highest peak value of 19.5, followed by the MultiPro-RCPC. This study enlightens that with the concentration system settings adapted to the acceptance range of the proposed concentrators, a higher concentration can be achieved with the MultiPro-ECPC and MultiPro-RCPC compared to the conventional CPC.

Energy matrices, enviro-economic and characteristic equation-based performance analyses of photovoltaic thermal compound parabolic concentrator (PVT-CPC) coupled solar still equipped with heat exchanger using SWCNTs and MWCNTs–water nanofluids

In this paper, effect of single wall carbon nanotubes (SWCNTs) and multiwall carbon nanotubes (MWCNTs)- water based nanofluid have been studied to examine the performance, long-term feasibility andenviro-enviro-economic analysis of partially covered series connected N- photovoltaic thermal (PVT)-compound parabolic concentrator (CPC) collectors coupled double slope solar still (DSSS) equipped with helically coiled heat exchanger (HE). Analysis have been carried out by developing thermal modelling of the proposed system. Instantaneous gain and loss efficiencies; annual thermal energy/exergy, and productivity – is investigated for optimized parameters of the proposed system in detail. Gain efficiency of the proposed system is found to be approximately 25-30% higher using CNT-NPs as compared to the system without using NPs. Annual thermal energy and exergy of CNTs, particularly SWCNTs water-based nanofluid (thermal energy- 2491.55 kWh, thermal exergy-894.67 kWh) have been found to be greater in comparison to basefluid (thermal energy -2185.76 kWh, thermal exergy-772.18 kWh). Also, results give higher value of CO2 mitigation using CNT-NPs both on the basis of energy (SWCNT-5.082t, MWCNT-4.787t) and exergy (SWCNT-1.83t, MWCNT-1.76t) respectively. SWCNT-NPs shows better performance due to their better TPPs; also PVT-CPC collector integrated DSSS equipped with HE is more viable practically.

Harnessing the characteristic of compound parabolic concentrators for directional concentration of emitted thermal radiation and solar shielding in building-integrated radiative cooling

Radiative sky cooling (RC) is a promising solution for meeting the growing cooling demands by passively dissipating waste heat into frigid outer space. However, current RC systems suffer from low cooling power density and limited installation flexibility, impeding their effective application as building cooling strategies. To overcome these challenges, a novel concentrated RC system coupled with a compound parabolic concentrator (CPC) is proposed and experimentally studied. The objective is to investigate the effectiveness of the CPC in enhancing the cooling capability of the RC system and the feasibility of achieving all-day RC in unfavorable working conditions when integrated with building roofs. During nighttime experiments in the humid Nottingham region, the CPC-RC system exhibited an average emitter temperature that was 5.83 °C lower than the ambient temperature, representing a 30 % and 13.6 % improvement in RC performance compared to the flat-RC system and trapezoidal-concentrated RC system, respectively. The Photopia optical software simulation indicates that when the modules are tilted to the north, the CPC functions as a solar shield, effectively limiting solar radiation reaching the emitter surface, which is advantageous for conducting daytime RC experiments. In the daytime experiment, the emitter temperature of the CPC-RC module in anti-sunward group was still 1.59 °C lower than the ambient temperature and 5.49 °C lower than that of flat-RC module. At night, the CPC-RC module of the three placement groups all showed the highest RC effect in the same group. The average emitter temperature of the CPC-RC module in the horizontal placement group is 0.6 °C lower than that of the flat RC module. This novel CPC-RC scheme presents a new energy-saving strategy for buildings and showcases its potential for achieving 24-hour RC when integrated into anti-sunward roofs.

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.

Optical, electrical, and thermal performance enhancement for a concentrating photovoltaic/thermal system using optimized polynomial compound parabolic concentrators

Performance of a concentrating photovoltaic/thermal system directly depends on the solar irradiation gathered by concentrators. Few studies tackled the systemic and general optimizations of optical efficiency and uniformity of energy distribution for two-dimensional compound parabolic concentrators (CPCs). In this paper, a polynomial CPC is proposed. To evaluate the optical efficiency and uniformity of the concentrated irradiation, an interpolation method is also proposed. Using genetic algorithm, the optimized polynomial CPCs with different polynomial orders are determined. With fourth order, the concentrating efficiency reaches the theoretic limit, and the concentrated irradiation is relatively uniform. Accordingly, the optimized polynomial CPCs for concentration ratios not larger than 10 are determined. Using a double-pass spectral beam splitting photovoltaic/thermal system model, the electrical and thermal performance using the determined optimized polynomial CPCs is calculated. For concentration ratios not larger than 10, the optimized polynomial CPC is able to provide high concentrating efficiencies with good uniformity. Moreover, the maximum temperature of the photovoltaic cell is smaller than 325 K. And then, the optimized polynomial CPCs for multiple incident angles are presented, along with the system performance. For multiple incident angles, the optimized polynomial CPC also shows good performance, but the size increases.

Duplex solar cooker with selective evacuated tube and compound parabolic concentrator

In the present work, an indirect solar cooking proposal is shown. The proposal combines three technologies: evacuated tubes, selective absorber, and compound parabolic concentrator (CPC). The absorber used is an evacuated glass tube, with a highly selectivity inner surface. The temperature reached by the solar cooker is approximately 160°C, enough to cover the cooking needs of all types of food; Irradiance, wind speed, ambient temperature was measured, food cooking tests were carried out, using an evacuated tube and a parabolic solar concentrator; as well as evacuated tube without parabolic solar concentrator. A compound parabolic concentrator was designed with an acceptance angle of 15 degrees, the base of the solar cooker was made with acrylic, the concentrator was made with simple reflection mirrors, the clips were printed on a 3D printer, the trays were made with food grade stainless steel, food cooking tests were carried out, recording the weather variables every 15 minutes. The development of this evacuated tube duplex solar cooker project is not only important because it involves the achievement of an academic purpose, but also involves a social purpose. It is intended to provide an efficient and economical solution that is attractive to multilateral organizations capable of supporting its manufacture, industrialization and distribution to achieve the massification of the product with a real and lasting impact

Performance of compound parabolic concentrator solar air flat plate collector using phase change material

This work involves an experimental investigation on two different new models of Compound Parabolic Concentrator (CPC) solar air flat plate collector with adding paraffin wax Phase Change Material (PCM). The first model is called involute shape model, whereas the second model is called normal shape model. To explore the best model performance, the structures of compound parabolic concentrator models have two symmetric giant parabolic mirror reflectors, similar concentration ratio of 1.7, similar flat plate receiver with 12 tubes filled by paraffin wax phase change material. The performances of both models are presented together for purpose of comparison. The tests have been performed in April and May 2023 in Mosul city/Iraq under standard conditions for around 11 h during the day. The outcomes indicated that rising in air mass flowrate leads to rise the receiver performance. The findings confirm that the thermal efficiency of normal shape is more efficient than involute shape by 7.6%, 13%, and 11.7% for 0.0085 kg/s, 0.0174 kg/s, and 0.027 kg/s, respectively. The optimum thermal performances for involute and normal shapes have been obtained equal 65.4% and 77.1% for 0.027 kg/s, respectively. For constant air flowrate, the performance of normal shape is higher than involute shape by 15.5% (14th May), 12.6% (27th April) and 11.8% (15th April). A significant temperature change has been found in involute shape as compared to normal shape. The outlet temperature of normal shape is always lower than the involute shape for all air mass flowrate. It is demonstrated that phase change material and the position of the receiver have considerable influence on the model performance. The current work provides an important information for evaluating the compound parabolic concentrator model performance for Mosul/city.

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.