Search Results (25)

This paper is a summary of the last ten years of work on the study of parabolic trough collectors (PTCs) and compound parabolic collectors (CPCs) coupled to photovoltaic and thermal solar receiver collectors (SCR-PVTs). While reviewing the state of the art, numerous review papers were found that focused on conventional solar receiver collector (SRC) technology for solar thermal generation. However, there is a lack of review papers summarizing SRC-PVT hybrid technology for solar electric/thermal generation, which would be beneficial for researchers interested in this area of research. This paper provides a review of SRC-PVT hybrid technologies. The theoretical foundations for analyzing and modeling PTC and CPC concentrators coupled to SRC-PVT are described, with an emphasis on modeling through thermal resistances and energy balances. Additionally, this section provides a concise overview of previous studies that have addressed the modeling of PTC and CPC collectors coupled to SCR-PVT, as well as experimental information useful for the validation of new mathematical models of SRC-PVT. Full article

In this study, the solar photo-Fenton (SPF) process was investigated for the degradation of doxycycline (DOX) using a solar compound parabolic collector (CPC) reactor and a borosilicate serpentine tube with an irradiated volume of 1.8 L. The influence of the operating parameters, such as H₂O₂, Fe²⁺ dosage, and DOX concentration, was investigated. The optimum H₂O₂, Fe²⁺ dosage, and DOX concentration were found to be 4, 0.1, and 0.06 mM, respectively. The results of photo-Fenton experiments fitted the pseudo-first-order kinetic equation (R² = 0.99). The efficiency of the treatment under optimized conditions was analyzed by an HPLC analysis of the samples, chemical oxygen demand (COD), and total organic carbon (TOC). The results obtained showed that the solar photo-Fenton process achieved a DOX degradation of 95.07%, a COD elimination of 81.43%, and a TOC elimination of 73.05%. The phytotoxicity tests revealed a 73.32% decrease in the germination index of watercress seeds, demonstrating that the SPF process minimizes the toxicity of the chemical and did not have any negative impact on plant growth. Overall, the results of this study suggest that SPF is a promising technology for the removal of doxycycline from wastewater. Full article

The building sector is targeting net-zero emissions through the integration of renewable energy technologies, especially for space cooling and heating applications. In this regard, the use of solar thermal concentrating collectors is of vital importance. The performance of these collectors increases by using an efficient fluid such as a nanofluid due to their high thermal conductivity. This research addresses the preparation, stability analysis, and characterisation of metallic and non-metallic oxide nanofluids and their experimental analysis in a compound parabolic collector (CPC) system. Five different combinations of nanofluids are used with different volumetric concentrations (0.025%, 0.05%, and 0.075%) including multi-wall carbon nanotube with water (MWCNT–H₂O), multi-wall carbon nanotube with ethylene glycol (MWCNT–EG), aluminium oxide with water (Al₂O₃–H₂O), aluminium oxide with ethylene glycol (Al₂O₃–EG), and magnesium oxide with ethylene glycol (MgO–EG). The prepared nanofluids are characterised in terms of thermal conductivity and viscosity. Detailed experimentation is performed to investigate the CPC system integrated with the nanofluids. The results obtained from the detailed characterisation of the MWCNT–H₂O nanofluid showed that the nanofluids have a 37.17% better thermal conductivity than distilled water as a primary fluid, and the MWCNT–EG nanofluid has demonstrated an increase in viscosity by 8.5% compared to ethylene glycol (EG). The experimental analysis revealed that the thermal efficiency of the collector integrated with the MWCNT–H₂O nanofluid is increased by 33% compared to water. Meanwhile, the thermal efficiency of the collector with MWCNT–EG was increased by 24.9% compared to EG. Moreover, a comparative analysis among metallic nanofluids was also performed, i.e., Al₂O₃–H₂O, Al₂O₃–EG, and MgO–EG. In each case, the thermal efficiency of the collector was recorded, which was greater than the base fluid by percentages of 29.4%, 22.29%, and 23.1%, respectively. The efficiency of non-metallic nanofluids is better than metallic nanofluids by 7.7%. From the obtained results, it can be concluded that the CPC system performed best with MWCNT–H₂O compared to any other combination of nanofluids. Full article

CPC solar collectors are a combination of new technologies that make it possible to generate heat from radiant solar energy by transferring heat between the absorber and the fluid. This study was performed based on heat transfer equations by proposing a mathematical model, as reported in the literature. A compound parabolic concentrators solar collector (CPC) numerical model was simulated and coded in Aspen HYSYS and MATLAB software and validated by comparing its results with other researchers and experimental results. The simulated mathematical model includes a two-dimensional numerical model to describe the thermal and dynamic behavior of the fluid inside the CPC solar collector absorber tube. Numerical simulations of the fluid flow equations inside the CPC solar collector absorber tube, along with the energy equation for the absorber tube wall, coating, insulation and reflector, and solar collector heat analysis, were performed repeatedly in MATLAB and Aspen HYSYS software. This method is the most appropriate and reliable method for solving equations for numerical convergence. The experimental results of the parabolic concentrated solar collector (CPC) were used to evaluate and validate the numerical model. A solar compound parabolic concentrators collector (CPC) with short reflectors was used. This collector includes a cylindrical absorber with a real density ratio of 1.8, a reception angle of 22 degrees and a length of 2.81 m, a width of 0.32 m, and an opening of 0.1764 m. Analysis and uncertainty of the proposed model were performed with the measured sample. In the thermal efficiency analysis, the average deviation of the model from the experimental results of other researchers was equal to 7%, for increasing the temperature by 9 °C. According to these results, a good correlation between numerical results and experimental results for this proposed model has been obtained. Full article

One of the key areas of the UN’s sustainable development goals is growing affordable and clean energy. Utilizing solar energy that is now accessible will significantly lessen the demand for fossil fuels. Around the world, cooking is a crucial activity for homes and uses a lot of non-renewable energy. Uncontrolled firewood usage results in deforestation, whereas using biomass-related fuels in inefficient stoves can result in smoke emanating from the kitchen and associated health issues. The benefits of solar cooking include reducing smoke-related problems and saving on fossil fuels and firewood. Applying thermal storage systems in cooking helps households have all-day cooking. This review article presents the research and development of a solar cooking system that transfers solar energy into the kitchen and integrates with the thermal energy storage system, finding the factors affecting indoor solar cooking performance. Adding portable cooking utensils helps in improved solar indoor cooking. Multiple phase change materials arranged in cascaded to store thermal energy helps in quick heat transfer rate, thus enabling better and faster cooking. A novel indoor solar cooker with an innovative arrangement of evacuated tube-based compound concentrating parabolic (CPC) collectors with a cascaded latent heat thermal energy storage system is proposed and needs to be tested under actual meteorological conditions. Full article

Research into solar absorption chillers despite their environmental benefits has been limited to date to mainly larger systems whilst ignoring smaller building-scale units, which can significantly benefit from the use of optimally designed, low concentrating, non-imaging optical reflectors. A solar absorption chiller system designed to provide year-round space cooling for a typical primary health care facility in Cairo, Egypt, was designed to match local ambient, solar, and occupancy conditions, its performance simulated and then optimized to minimize auxiliary power consumption using the TRNSYS18 software, TRNOPT. Different configurations of collector types, array areas, storage sizes and collector slopes were used to determine the optimum specifications for the system components. Non-concentrating Evacuated Tube Collectors (ETCs) were compared with the same Evacuated Tube Collectors but integrated with external Compound Parabolic Concentrators (CPCs) with a geometric concentration ratio of 1.5X for supplying thermal energy to the single-effect absorption chiller investigated. This paper describes a user-friendly methodology developed for the design of solar heat-powered absorption chillers for small buildings using TRNSYS18 employing the Hookes–Jeeves algorithm within the TRNOPT function. Clear steps to avoid convergence problems when using TRNSYS are articulated to make repeatability for different systems and locations more straightforward. Collector array areas were varied from 30 m² to 160 m² and the size of the water-based thermal storage from 1 m³ to 3 m³ to determine the configuration that can supply the maximum solar fraction of the building’s cooling requirements for the lowest lifetime cost. The optimum solar fraction for ETCs and CPCs was found to be 0.66 and 0.94, respectively. If the current air conditioning demand is met through adoption of the CPC-based solar absorption systems this can potentially save the emission of 3,966,247 tCO₂ per annum. Full article

The concentrating photovoltaic/thermal (PVT) collectors offer the benefits of the reduced per-unit price of electrical energy and co-generation of electrical and thermal energies by intensifying the solar irradiation falling on the hybrid receiving plane. The compound parabolic concentrating (CPC) collectors have appeared as a promising candidate for numerous applications in the field of solar energy due to their ability to collect both direct and diffuse solar radiation and suitability for stationary installation. Over the last few decades, various configurations of CPC collectors have been proposed and investigated by different researchers for the simultaneous generation of electrical and thermal energies. This article presents a comprehensive review of historical and recent developments and applications of CPC-based hybrid PVT systems. The review focuses on the heat extraction mechanisms and commonly used application areas of CPC-PVT systems. The innovative design configurations proposed by different researchers have been reviewed in detail. The outputs of CPC-PVT systems are generally found to be superior to their counterparts without CPCs, which justifies their increased popularity. Due to dual outputs, the hybrid CPC-PVT systems are considered to be suitable for rooftop and building façade integrated applications. Finally, future recommendations have been enlisted, highlighting the potential research opportunities and challenges for the prospective researchers working in the field of concentrating solar PVT systems. Full article

The paper presents a design and operation analysis of an Integrated Collector Storage (ICS) solar water heater, which consists of an asymmetric Compound Parabolic Concentrating (CPC) reflector trough, while the water tank comprises two concentric cylinders. The annulus between these vessels is partially depressurized and contains a small amount of water in the bottom of the outer vessel which dominantly contributes to the heat transfer from the outer to the inner cylinder. A multi-criteria optimization algorithm is applied to re-evaluate the design specifications of the parabolic surface, thus modifying the design of the entire ICS system and predict the necessary number of units for achieving the highest possible effectiveness with minimized fabrication costs and environmental impacts. The environmental footprint of the device is assessed through Life Cycle Assessment (LCA). The produced thermal energy in conjunction with the environmental and economic results are evaluated as a function of different configuration parameters regarding the water storage conditions, the solar radiation and the total pressure inside the annulus. The ultimate aim of the evaluation process is to offer new perspectives on the design principles of environmentally friendly and cost-effective devices with improved thermal performance. Full article

Solar energy is a viable source to fulfill the energy demands of a solar rich country such as Pakistan. Various types of solar thermal technologies are being used around the world, including flat plate, evacuated tube, and compound parabolic trough collectors. However, the performance of these collectors is strongly influenced by the nature of work fluid. Utilization of nanofluids with high thermal conductivity is a very attractive way to further enhance the performance of solar collectors. Therefore, this study deals with the characterization and thermal performance enhancement of compound parabolic collectors (CPC) by using non-metallic nanofluids such as water-based multi-wall carbon nano tubes (H₂O-MWCNT) with a thermal conductivity of 3000 W/m·K. In the current work, multiple tests are performed to analyze the thermal conductivity and stability of nanofluids through thermal analyzer and UV-Vis Spectroscopy, respectively. Test results show that the thermal conductivity of water-based MWCNT nanofluid is 37% higher than water at a concentration of 0.075%. Prepared nanofluids are then employed in CPC, and detailed experimentation is performed by varying the concentration of nanoparticles (0.025, 0.05, 0.075%) and their flow rate (0.015, 0.02 kg/s). Maximum temperature difference of 10.5oC with volumetric concentration of 0.075% is achieved in experimental analysis at flow rate 0.015 kg/s. Thermal efficiency enhancement of 19.37% with volumetric concentration 0.075% is recorded as compared to water at flow rate 0.015 kg/s. Full article

Solar thermal collectors, such as flat plate and evacuated tube collectors, are used for maximum of 60–80 °C temperature and parabolic trough collectors are used for 700–900 °C temperature ranges. It is needed to develop and analyze solar collectors, such as compound parabolic collectors (CPC) which can operate in an intermediate temperature range from 50–300 °C for industrial and domestic applications. However, optical and thermal performance of CPC is strongly influenced by concentration ratio. The current study presents a comparative optical and thermal analysis of CPC with fixed (4) and variable (4.5 to 5.7) concentration ratio by using model-based transient simulation approach. Two profiles of compound parabolic collector are analyzed with fixed and variable concentration ratio for the subtropical climate of Taxila, Pakistan. 2D profiles of both collectors are modeled and designed in MATLAB and are then analyzed optically by using Monte Carlo ray tracing technique through TracePro. In addition, thermal analysis of both profiles is also performed through ANSYS. The resulting optical efficiencies with fixed and variable concentration are 72% and 79%, respectively. Whereas maximum temperature achieved with both profiles is 352 K and 367 K, respectively. Thus, it is concluded that performance of CPC with variable concentration ratio is much better compared to fixed value. Full article

The design of solar concentrating collectors for the effective utilization of solar energy is a challenging condition due to tracking errors leading to different divergences of the solar incidence angle. To enhance the optical performance of solar parabolic trough collectors (SPTC) under a diverged solar incidence angle, an additional compound parabolic concentrator (CPC) is introduced as a secondary reflector. SPTC with CPC is designed and modeled for a single axis-tracking concentrating collector based on the local ambient conditions. In this work, the optical performance of the novel SPTC system with and without a secondary reflector is investigated using MATLAB and TRACEPRO software simulations for various tracking errors. The significance parameters such as the solar incidence angle, aperture length, receiver tube diameter, rim angle, concentration ratio, solar radiation, and absorbed flux are analyzed. The simulation results show that the rate of the absorbed flux on the receiver tube is significantly improved by providing the secondary reflector, which enhances the optical efficiency of the collector. It is found that the optical efficiency of the SPTC with a secondary reflector is 20% higher than the conventional collector system for a solar incidence angle of 2°. This work can effectively direct the choice of optimal secondary reflectors for SPTC under different design and operating conditions. Full article

This study focuses on the thermodynamic performance analysis of the solar organic Rankine cycle (SORC) that uses solar radiation over a moderate temperature range. A compound parabolic collector (CPC) was adjusted to collect solar radiation because of its long-lasting nature and featured low concentration ratios, which are favorable for moderate temperature applications. A thermal storage tank was fixed to preserve the solar energy and ensure the system’s continuous performance during unfavorable weather. However, water was used as the heat transfer fluid and R245fa was used as the working fluid in this system. The performance in both the hottest and coldest months was analyzed using the average hourly profile in MATLAB using weather data from Riyadh, Saudi Arabia. Variations in the tank temperature during the charging and discharging modes were found. The hourly based thermal efficiency and net power output for both configurations were also compared. The results show that at 17:00, when the cycle was about to shut down, the thermal efficiency was 12.79% and the network output was 16 kW in July, whereas in January, the efficiency was ~12.80% and the net power output was 15.54 kW. Full article

Compound parabolic concentrator (CPC) solar collectors are widely used for solar energy systems in industry; however, CPC collectors for residential applications have not been fully investigated. In this work, the thermal performance of non-tracking, small-size and low-cost CPC collectors with an absorber with and without segmented fins was studied experimentally and by means of a proposed numerical methodology that included ray tracing simulation and a coupled heat transfer finite element method (FEM)-computational fluid dynamics (CFD) simulation, which was validated with experimental data. The experimental results showed that the CPC with a finned absorber has better thermal performance than that of the CPC with absorber without fins, which was attributed to the increase in thermal energy on the absorber surface. The numerical results showed that ray tracing simulation can be used to estimate the heat flux on the absorber surface and the FEM-CFD simulation can be used to estimate the heat transfer from the absorber to the water running through the pipe along with its temperature. The numerical results showed that mass flow rate is an important parameter for the design of the CPC collectors. The numerical methodology developed in this work was capable of describing the thermal performance of the CPC collectors and can be used for the modeling of the thermal behavior of other CPCs solar systems. Full article

Photovoltaic (PV) panels and thermal collectors are commonly known as mature technologies to capture solar energy. The efficiency of PV cells decreases as operating cell temperature increases. Photovoltaic Thermal Collectors (PVT) offer a way to mitigate this performance reduction by coupling solar cells with a thermal absorber that can actively remove the excess heat from the solar cells to the Heat Transfer Fluid (HTF). In order for PVT collectors to effectively counter the negative effects of increased operating cell temperature, it is fundamental to have an adequate heat transfer from the cells to the HTF. This paper analyzes the operating temperature of the cells in a low concentrating PVT solar collector, by means of both experimental and Computational Fluid Dynamics (CFD) simulation results on the Solarus asymmetric Compound Parabolic Concentrator (CPC) PowerCollector (PC). The PC solar collector features a Compound Parabolic Concentrator (CPC) reflector geometry called the Maximum Reflector Concentration (MaReCo) geometry. This collector is suited for applications such as Domestic Hot Water (DHW). An experimental setup was installed in the outdoor testing laboratory at Gävle University (Sweden) with the ability to measure ambient, cell and HTF temperature, flow rate and solar radiation. The experimental results were validated by means of an in-house developed CFD model. Based on the validated model, the effect of collector tilt angle, HTF, insulation (on the back side of the reflector), receiver material and front glass on the collector performance were considered. The impact of tilt angle is more pronounced on the thermal production than the electrical one. Furthermore, the HTF recirculation with an average temperature of 35.1 °C and 2.2 L/min flow rate showed that the electrical yield can increase by 25%. On the other hand, by using insulation, the thermal yield increases up to 3% when working at a temperature of 23 °C above ambient. Full article

The compound parabolic concentrator (CPC) is a highly interesting solar collector technology for different low-concentration applications due to no tracking requirement. The CPC with a tubular absorber is the most common type of CPC. Here, a comprehensive state-of-the-art review of this CPC type is presented, including design features, structure, applications, etc. Key design guidelines, structural improvements, and recent developments are also presented. Full article