Compound Parabolic Concentrator Solar Collector Research Articles

Effects of Outdoor Conditions on the Compound Parabolic Concentrator Performance

In this study, the effect of outdoor conditions(wind velocity and ambient temperature) on the thermalefficiency of a non-evacuated Compound ParabolicConcentrator solar collector (CPC) was investigated fortwo different flow rates. Matlab program was built, andsimulation results for different outdoor conditions werecompared with an actual outdoor data set that was takenat Misurata city, Libya. Although this study showed someeffects of outdoor conditions on the CPC collectorcomponent’s temperatures and heat losses, no importantinfluence on the collector efficiency was noticed.Therefore, even though wind velocity and ambienttemperature vary throughout the day, approximatingthem as constant values is a reasonable assumption. Massflow rate is the most important parameter that affects theCPC efficiency.

Performance modeling and cost optimization of a solar desalination system using forward osmosis with energy storage

This study presents the design and performance evaluation of a solar-driven water desalination system based on forward osmosis (FO) with thermally responsive ionic liquids (ILs). FO is a two-step process involving dilution of the ILs with water, followed by heating above a critical temperature to induce phase separation of liquid water from the IL. This regeneration step can be achieved by integrating FO with low-grade solar energy, which is abundant in regions that face severe water scarcity. A system design is presented that couples an FO membrane module with a compound parabolic concentrator solar collector and thermal energy storage to minimize solar intermittency and produce clean water at a distributed scale of 10 m3/day. To determine the optimal sizing of components in the system, a technoeconomic analysis using the TRNSYS software is performed with the goal of minimizing the levelized cost of water (LCOW). Notably, over 96 % of the energy required for regeneration comes from solar energy and/or the thermal energy storage (TES) in all cases, with auxiliary heat from electricity being used to maintain a continuous process. To evaluate the potential of solar-FO in three different locations within the United States, a case study is presented for Phoenix, AZ; San Diego, CA; and Atlanta, GA. The simulation results reveal that for a small-scale desalination system, LCOW values as low as $1.31/m3 can be attained, with the potential to approach $1/m3 by lowering the costs of the solar collector and FO module based on a sensitivity analysis.

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.

Experimental study in a compound parabolic solar concentrator with different configurations of thermal energy storage system

ABSTRACT This study explores the integration of thermal energy storage (TES) systems with solar water heating systems to increase their utilization time. While solar water heating systems are effective for low-temperature applications, they become less efficient at higher heat transfer fluid (HTF) temperatures. To solve this problem, the study suggests combining a compound parabolic concentrator (CPC) solar collector with a TES system to improve heat transfer rates and minimize heat loss. The study examines the effect of different mass flow rates and HTF inlet temperatures on the integrated system's performance, evaluating energy efficiency, exergy efficiency, and overall loss coefficient. The results reveal that the six-phase change materials (PCMs) configuration achieves the highest intercept line efficiency of 72%, with a heat transfer rate 1.7 times higher than that of the single PCM configuration. Moreover, the exergy analysis shows superior performance compared to commonly used flat collectors. Overall, the proposed CPC solar collector integrated with a TES system is suitable for low-temperature applications with an inlet HTF temperature not exceeding 65°C.

Investigation of solar assisted air source heat pump heating system integrating compound parabolic concentrator-capillary tube solar collectors

Solar assisted air source heat pump heating systems are capable of achieving green heating where solar availability essentially affects its operation performance and application potentials, especially in higher-latitude regions, such as UK. Compound parabolic concentrator solar collectors can achieve high collector efficiency at high hot water temperature, benefitting to improve solar collection and corresponding thermal energy storage capacities. Though compound parabolic concentrator solar collectors have been widely investigated, application of such collector for solar assisted air source heat pump system is not studied yet. The paper reports numerical simulations of solar assisted air source heat pump heating systems that integrate compound parabolic concentrator-capillary tube solar collectors for domestic heating in the UK. The results show that, for the same seasonal performance factor, the size of the concentrated solar collector required is 12 m2 whereas the size of the flat plate solar collector required is 18 m2. This suggests one third reduction in the size of solar collector, significant reduction in cost and convenience for installation. The results also show the potential to further reduce the size of the concentrated solar collector to 9 m2 or less. The high collector efficiency of the compound parabolic concentrator-capillary tube solar collector enables much small size of solar collector, significantly lower cost and convenient for installation and wide rollout of solar assisted air source heat pump heating system to locations where solar irradiance is relatively lower.

Simulation study of compound parabolic collector‐based solar water heating system with thermal energy storage

AbstractSolar water heating (SWH) systems becomes increasingly popular in modern buildings, due to significant reduction in energy consumption in heating applications. In this work, an active SWH is modeled using TRNSYS software for climatic conditions of Chennai, India, employing an external compound parabolic concentrator solar collector and stratified thermal storage system (STESS). The performance parameters are estimated on the basis of monthly and annual averaged solar fractions (SF) by varying the collector area, mass flow rate, various controller strategies, and STESS geometry. The simulated studies have specified the ability of the optimized system to supply the hot water demand of 280 L d−1 at 60°C, attaining a SF of 0.97. This design strategy can be implemented for the development of an efficient SWH system, utilizing zero energy consumption from conventional resources. The proposed TRNSYS model has been validated using experimental data under similar test conditions. An influence of placing XCPC under evacuated tubes is simulated, resulting 5% improvement in energy gained over an evacuated tube solar collector without XCPC.

Amorphous carbon based nanofluids for direct radiative absorption in solar thermal concentrators – Experimental and computational study

Directly solar radiation absorbing nanofluids have the potential to absorb a wide spectrum of solar radiation and displace selectively coated metallic receivers in solar thermal collectors. Parameters including nanoparticle concentration, synthesis and storage conditions, can influence their long-term usage. In this study, 60 min was found to be optimal sonication duration to synthesise a uniform suspension of nanofluid containing amorphous-carbon nanoparticles and ethylene glycol as base fluid. Nanoparticle concentration can be used to tune extinction coefficient of nanofluid in the range of 75–400 m−1 for wavelength range of 320–1000 nm. Long-term stability and high temperature studies showed a time and temperature dependent increase in transmittance of nanofluid which is restored by 5 min of stirring. Computational modelling highlighted the role of incident intensity, nanoparticle concentration as well as inlet flow rate on receiver exit temperature. A ray-optics model employing weather data for Delhi (India) can predict the optical efficiency of an Asymmetric Compound Parabolic Concentrator solar collector. This combined approach can enable to predict the flow rate required to achieve a desired supply temperature at target locations. This rational framework combining experimental and computational approaches can be used to identify design parameters relevant for application of nanofluids in thermal collectors.

Thermal performance enhancement of compound parabolic concentrator solar collector using latent heat thermal energy storage

Employment of compound parabolic concentrator (CPC) solar collector with evacuated tubes enables effective collection of solar energy. The main objective of the present experimental work is to investigate thermal performance of CPC solar collector coupled with sensible and latent heat thermal energy storage (TES) system. Depending on obtained thermal stratification in sensible TES system, a commercial phase change material (PCM)—OM 65 has been selected and packed only at top quarter section of the TES system. Results showed an appreciable cumulative energy storage of 21 MJ d−1 due to existence of desired temperature driving potential during charging. A higher thermal stratification has been achieved in latent heat TES system, reducing the “MIX” number and supplying the heat transfer fluid at lower temperature to the collector. Due to enhanced useful heat energy gained, thermal efficiency of CPC collector reaches a maximum of 49% while coupling with latent heat TES system. The outcome of the study highlights the potential role of CPC and PCMs in solar thermal system, particularly for water heating applications.

Amorphous Carbon Based Nanofluids for Direct Radiative Absorption in Solar Thermal Concentrators

Directly solar radiation absorbing nanofluids have the potential to absorb a wide spectrum of solar radiation and displace selectively coated metallic receivers in solar thermal collectors. Parameters including nanoparticle concentration, synthesis and storage conditions, can influence their long-term usage. In this study, we found that 60 minutes is optimal sonication duration to synthesise a uniform suspension of nanofluid containing amorphous-carbon nanoparticles and ethylene glycol as base fluid. Nanoparticle concentration can be used to tune the extinction coefficient of nanofluid in the range of 75-400 m-1 for wavelength range of 320-1000 nm. Long-term stability and high temperature studies showed a time and temperature dependent increase in transmittance of nanofluid which is restored by 5 minutes of stirring. Computational modelling highlighted the role of incident intensity, nanoparticle concentration as well as inlet flow rate on receiver outlet temperature. A ray-optics model employing weather data for Delhi (India) can predict the optical efficiency of an Asymmetric Compound Parabolic Concentrator solar collector. This combined approach can enable to predict the flow rate required to achieve a desired supply temperature at target locations. This rational framework combining experimental and computational approaches can be used identify design parameters relevant for application of nanofluids in thermal collectors.

Model verification and photo-thermal conversion assessment of a novel facade embedded compound parabolic concentrator

A novel facade embedded compound parabolic concentrator solar collector (FE-CPC-SC) with great application potential was proposed, which was aimed to capture and utilize the solar rays reaching the building facade. The optical models of beam and diffuse radiation were constructed for the designed physical model, which was based on Monte Carlo Ray-trace and numerical method. The optical simulation results showed that average optical efficiency for FE-CPC-SC system is approximately 64.51%. Additionally, a closed-loop photo-thermal conversion experiment with a maximum uncertainty of 10.24% was performed to verify the numerical heat transfer model of the photo-thermal conversion performance for FE-CPC-SC system. The experimental values of photo-thermal efficiency were in good agreement with the theoretical values, and the relative error was between −12.5% and 10.8%. According to the verified numerical model, the photo-thermal performance of FE-CPC-SC system applicable to four different latitudes was predicted and evaluated. The evaluation results presented that the annual heat gain in different latitudes (Kunming, Chengdu, Xi’an and Beijing) is 825.17, 447.84, 655.77 and 441.38 MJ/m2, respectively. Furthermore, the FE-CPC-SC system could meet the human-oriented thermal energy demand in an environmental-friendly way and alleviate the pressure on building energy consumption.

Experimental and computational fluid dynamics investigations of tracking CPC solar collectors

The aim of the paper was to investigate thermal performance of two newly developed 15.4 m2 compound parabolic concentrator (CPC) solar collectors both theoretically and experimentally. The two collectors are identical except that one collector is equipped with a transparent Ethylene tetrafluoroethylene (ETFE) foil and the other collector is not. Experimentally the solar collectors were tested in an outdoor test facility at different temperatures. Collector efficiencies were determined. Theoretically simplified CFD models of the CPC solar collectors were developed and validated against the measurements. A ray tracing tool Tonatiuh was used to calculate distribution of solar irradiance on the receiver. The influence of the ETFE foil on collector heat loss coefficient and efficiency was investigated. The results show that the CFD model predicts satisfactorily temperature rises of the collectors in the temperature range between 20 °C and 81 °C. The deviations between the measured and the calculated temperature rises were limited to ±0.3 K with a relative error less than 3.7%. By installation of the ETFE foil, the first order collector heat loss coefficient decreased from 1.42 to 0.82 W/m2/K. Efficiency of the collector with the ETFE foil was measured to be 63%, 55% and 54% for a mean collector fluid temperature of 27 °C, 63 °C and 81 °C respectively. For a solar irradiance of 895 W/m2 and a mean collector temperature of 133 °C, collector efficiency is predicted to increase from 36% to 41% by installation of the ETFE foil. Another 5% increase of collector efficiency is expected if installation of the foil is made airtight.

Numerical and experimental investigation on a new type of compound parabolic concentrator solar collector

In order to improve the thermal efficiency, reduce the heat losses and achieve high freezing resistance of the solar device for space heating in cold regions, a new type of serpentine compound parabolic concentrator solar collector is presented in this paper, which is a combination of a compound parabolic concentrator solar collector and a flat plate solar collector. A detailed mathematical model for the new collector based on the analysis of heat transfer is developed and then solved by the software tool Matlab. The numerical results are compared with the experimental data and the maximum deviation is 8.07%, which shows a good agreement with each other. The experimental results show that the thermal efficiency of the collector can be as high as 60.5%. The model is used to predict the thermal performance of the new collector. The effects of structure and operating parameters on the thermal performance are mathematically discussed. The numerical and experimental results show that the new collector is more suitable to provide low temperature hot water for space heating in cold regions and the mathematical model will be much helpful in the designing and optimizing of the solar collectors.

Thermal performance of a new CPC solar air collector with flat micro-heat pipe arrays

A new type of compound parabolic concentrator (CPC) solar air collector (SAC) with flat micro-heat pipe arrays (FMHPA) was investigated in this study. A cylindrical absorber was constructed by inserting the FMHPA into an evacuated glass tube to transport heat during the working process. The new FMHPA-CPC SAC is an edge ray collector with a concentration ratio of 1.8. The core concept is the integration of the FMHPA, an absorber tube, and a CPC reflector as a heat-collecting unit. Thermal performance investigation was conducted theoretically and experimentally. This study mainly analyzed the effect of different factors on the thermal performance of the collector. The efficiencies and heat loss coefficients of the new collector were determined. Experimental curves with different testing conditions are presented. The optimal value of efficiency was determined for the SAC. The aperture area of each CPC collecting unit is approximately 0.4 m2. The new FMHPA-CPC SAC was tested in Beijing, China. The average efficiency was approximately 61% at a volume flow rate of 320 m3/h, with a radiation of 799 W/m2 (ambient temperature of 28.8 °C). The instantaneous efficiency reached 68%, depending on the solar radiation, air volume flow rate, and ambient temperature. In addition, the time constant of the collector was approximately 14.8 min, with an air volume flow rate of 260 m3/h.

Experimental performance investigation of small solar air-conditioning systems with different kinds of collectors and chillers

Different types of solar collectors should be integrated with different sorption chillers. Traditional evacuated tube U pipe solar collector, high efficient CPC (Compound Parabolic Concentrating) solar collector and PTC (Parabolic Trough Collector) solar collector can provide 60–85°C, 85–125°C and 125–150°C of hot water. So, they can drive silica gel–water adsorption chillers, single-effect LiBr absorption chillers and double-effect LiBr absorption chillers, respectively. This paper will present the experimental performance investigation and economic analysis of three small solar cooling systems with these different kinds of collectors and chillers. The test results show that the solar COP (Coefficient of Performance) of the solar cooling system with adsorption chiller and U pipe solar collectors is about 0.15 and the silica gel–water adsorption chiller can be driven by 55°C of hot water. The solar COP of the system with CPC solar collector and single effect absorption chiller can reach 0.24 in the sunny weather condition. The solar COP of the solar cooling system with PTC solar collectors is about 0.5 and the double-effect LiBr absorption chiller is more attractive because of its higher solar COP (Coefficient of Performance) and better economy.

Optimal Design of Compound Parabolic Concentrator Solar Collector System

The multi-objective optimum design of stationary compound parabolic concentrator (CPC) solar collectors is considered. The clear day solar beam radiation and diffuse radiation at the location of the solar collector are estimated. Three objectives are considered in the optimization problem formulation: maximization of the annual average incident solar energy, maximization of the lowest month incident solar energy and minimization of the cost. A modified game theory (MGT) methodology is used for the solution of the three-objective constrained optimization problems. When compared to the optimum results of flat plate solar collectors, the CPC solar collector could significantly reduce the value of cost per unit energy ratio. Parametric studies are conducted with respect to changes in land price. The present study is expected to help designers in creating optimized solar collectors based on specified requirements.

Thermal Performance Testing of Heat Pipe Evacuated Tube with Compound Parabolic Concentrating Solar Collector by ISO 9806 - 1

Solar collector is an important component of solar hot water system. The purpose of this research is design, fabricate and test thermal efficiency of the heat pipe evacuated tube with compound parabolic concentrating (CPC) solar collector. The advantage of this system is it produces hot water over a period of time without adjusting the direction of the CPC to track the sun. The thermal performance of solar collector is critically important for the end users in order to ensure the efficiency of the system. The testing of CPC according to ISO 9806 - 1 found that the thermal efficiency was equal to 78%. The heat loss coefficient of the solar collector a1 and a2 are equal to 3.55 and 0.06 W/m2-oC respectively. The mathematical model was developed to determine the energy production base on solar radiation and ambient temperature data of Phitsanulok province. It was found that the monthly average energy of the CPC produced throughout the year is equal to 286.16 kWh or equal to 3,433.87 kWh/year.

Study of a novel solar adsorption cooling system and a solar absorption cooling system with new CPC collectors

One two-phase thermo-syphon silica gel-water solar adsorption chiller and LiBr-H 2 O absorption chiller with new medium CPC (Compound Parabolic Concentrator) solar collectors were investigated. The reliability of adsorption chiller can be improved, because there is only one vacuum valve in this innovative design. Medium temperature evacuated-tube CPC solar collectors were firstly utilized in the LiBr-H 2 O air conditioning system. The former system was applied in north of China at Latitude 37.45° (Dezhou city, China), the latter system was applied at Latitude 36.65° (Jinan city, China). Experimental results showed that the adsorption chiller can be powered by 55 °C of hot water. The adsorption chiller can provide 15 °C of chilled water from 9:30 to 17:00, the average solar COP (COPs) of the system is 0.16. In the absorption cooling system, the efficiency of the medium temperature evacuated-tube CPC solar collector can reach 0.5 when the hot water temperature is 125 °C. The absorption chiller can provide 15 °C of chilled water from 11:00 to 15:30, and the average solar COPs of absorption system is 0.19. ► Two-phase thermo-syphon adsorption chiller is designed. ► The adsorption chiller can be powered by hot water of 55 °C. ► New CPC solar collectors are used in LiBr-H 2 O absorption cooling system. ► Solar collector efficiency can reach 0.5 when the hot water temperature is 125 °C.

A review of natural convective heat transfer correlations in rectangular cross-section cavities and their potential applications to compound parabolic concentrating (CPC) solar collector cavities

Abstract Natural convective heat transfer in cavities is a complex function of cavity shape, aspect ratio, boundary conditions at the walls and the properties of the fluid contained within the enclosure. Considerable research into natural convection in regular shaped cavities, such as those of rectangular, square cross-section, or cylindrical annuli has been undertaken. Knowledge is, however, more limited relating to natural convective heat transfer in CPC solar collector cavities. Accurate knowledge of the variation in local convective heat transfer coefficients at the different CPC cavity components would facilitate to the design of suitable convection suppression devices, for example baffles at specific locations within the cavity, substantially reducing convective heat transfer and thus improving the performance of CPC solar collectors. From analysis of the correlations developed for regularly shaped enclosures it is concluded that the employment of these correlations to describe natural convection in CPC solar collector cavities can be misleading.

Optimum configuration of compound parabolic concentrator (CPC) solar water heater types for dwellings situated in the northern maritime climate

SYNOPSIS For northern maritime climates with a high diffuse component of solar radiation, non-imaging CPC solar collectors with concentration ratios of up to 2 can be used to concentrate direct as well as diffuse incident solar radiation without tracking. Due to the concentrated solar flux incident on the absorber, these systems can produce temperatures in excess of those produced by conventional solar water heaters, thus reducing the auxiliary energy requirement. Additionally, a smaller absorber area is required, reducing the cost of the solar collector and making these systems more economically attractive. Two CPC solar collectors with an identical cavity profile were fabricated, one utilising a heat-pipe absorber and the other a simple direct flow absorber. Both collectors were tested under steady state operating conditions at inlet temperatures of 20°C, 30°C 40°C and 50°C, to simulate the conditions experienced by a typical domestic solar water heater. It was found that the direct flow CPC performed better at higher solar intensities and lower inlet temperatures, as the heat-pipe CPC had a much higher absorber plate temperature. Thus, for domestic applications, simple direct flow CPC systems would be preferred due to their higher efficiency and lower cost.

An evaluation on thermal performance of CPC solar collector

The main objective of this work is the investigation and improvement of thermal performance of evacuated CPC (Compound Parabolic Concentrator) solar collector with a cylindrical absorber. Modified types of this solar collector are always combined with the evacuated glass envelop or tracking system. The conventional stationary CPC solar collector has been compared with the single axis tracking CPC solar collector in outlet temperature, net heat flux onto the absorber and thermal efficiency. Numerical model has been analyzed based on the irradiation determined actually and the results have been calculated to predict the thermal efficiency. Based on the comparison of the measured and calculated results, it is concluded that the numerical model can accurately estimate the performance of solar collectors. The result shows the thermal efficiency of the tracking CPC solar collector is more stable and about 14.9% higher than that of the stationary CPC solar collector.