Flat-plate Collector Research Articles

Novel flat-plate solar collector with an inclined N-S axis and relative E-W tracking absorbers and the numerical analysis of its potentials

The current flat-plate solar collectors perform best when their absorbers rotate around their axis. However, with their concentrators, reflectors, and tracking mechanisms, they take up a lot of space and are thus commercially speaking, not the best solutions. This paper proposes a novel solar collector design which employs the (relative) rotation of absorbers, but strives to combine the benefits of fixed and (absolute) tracking solar systems, i.e. volume occupancy from the former and thermal performance from the latter. The findings of our numerical analysis show that, the solar irradiance efficiency of this novel design is 20% higher than that of a fixed flat-plate collector during clear-sky days, and it is equally lower than that of an absolute tracking collector. This paper also introduces a new criterion for describing single-axis tracking solar collectors which should be included in the classifications of solar collectors. Finally, the article, which represents a continuation of our research in the field of solar energy utilization, can contribute to the future development of solar technologies and solve some of the current challenges.

Experimental Study of Temperature and Humidity Variations in an Incubator Fitted with a Flat-Plate Collector

Experimental Study of Temperature and Humidity Variations in an Incubator Fitted with a Flat-Plate Collector

INVESTIGATING THE PERFORMANCE OF A FLAT-PLATE SOLAR WATER-HEATING SYSTEM USING CeO2/WATER NANOFLUID: A HOLISTIC APPROACH

The efficiency of a solar water heater with a flat-plate collector, which had an absorber area of 2 m<sup>2</sup> and utilized a cerium oxide-water nanofluid as the working medium with a fixed volume fraction of 0.01%, was analyzed using a holistic approach. To assess the impact of flow rate on its heat transfer characteristics, the working fluid was systematically circulated through a pump-circulation system at various flow rates ranging from 1 to 3 liters per minute (LPM). The system underwent analytical and field testing, which revealed that it achieves a maximum thermal efficiency of 78.2% at a flow rate of 2 LPM. The heat transfer coefficient underwent a notable enhancement, leading to a 21.5% increase in thermal efficiency compared to a system operating with plain water. A refined artificial neural network (ANN) model was created to forecast thermal performance and outlet temperature. The optimized ANN model is structured with a 3-10-2 architecture and achieves a mean squared error of 8.2 × 10<sup>-3</sup>. The performance of the optimized ANN model was assessed by testing its generalization capacity against experimental results. It was determined that the ANN model predictions aligned closely with the experimental data, exhibiting correlation coefficients ranging from 0.96 to 0.98. This study conclusively demonstrates that the analytical model and ANN can serve as a highly effective design tool for evaluating the performance of innovative solar collectors.

Energy and Exergy Analysis of Forced Convection Solar Drying of Allium Sativum With and With Out Sensible Heat Storage

In this article the energy & exergy analysis of forced convection solar dryer for drying of garlic has been investigated. The exergy parameter, air velocity has been taken to conduct the experiments and its effect on thermal efficiency. Forced draft fans were used in all the two working conditions. During the two conditions, with and without sensible heat storage system, the average air-velocities were 4.5, 9.5 and 11.4 m/s selected as ideal and subsequently its entire effect on thermal efficiency and outlet. The ambient temperatures were between (17-25) °C during the month of October and November. A DC fan is directly connected to the photovoltaic cell in the solar dryer. The thermal energy storage bed was packed with gravels with 1.5 in of thickness up to the surface of flat plate collector, the storage system becomes space-efficient. The average thermal efficiency with sensible heat storage materials was high as compared to system without sensible heat storage. The highest thermal efficiency of 61% was achieved. The maximum collector temperature obtained was 55 °C, with a mean temperature of 42 °C in the drying chamber. The collector’s greatest exergy loss was 30.38 kJ/kg and highest exergy efficiency was 70%.

Experimental assessment of a solar photovoltaic-thermal system in a livestock farm in Italy

This paper presents an experimental evaluation of the performance of a solar photovoltaic-thermal (PVT) system in a swine farm at Mirandola in Italy. In this project named RES4LIVE, funded by the EU’s Horizon 2020 program, a PVT system is installed to replace fossil fuel consumption in one of the barns on the farm. The electrical energy from the collectors is utilized to operate the heat pump and provide electricity to the barn, whereas the thermal energy from the collector is stored in a borehole thermal energy storage (BTES) for further use by a 35 kW heat pump. The hybrid solar field consists of 24 covered PVT flat plate collectors (7.68 kWel and 25 kWth) with a total aperture area of 39.3 m2, which can increase the temperature of the heat transfer fluid (HTF) to up to 40 °C. The PVT system is connected to a modular solar central (SC) with a standardized design that can also be used for other similar applications. The hybrid solar system complemented by energy storage is expected to save approximately 20,850 kg CO2/year. The data collected from the PVT system, SC, and BTES are rigorously analyzed to evaluate its overall performance. A comprehensive performance assessment reveals the capability of the solar system to reduce carbon emissions and effectively replace fossil fuel consumption in the agricultural sector.

A Review on Next-Generation Solar Solutions: Pioneering Materials and Designs for Sustainable Energy Harvesting

As an essential initial step towards clean and sustainable energy, this research focuses on innovative materials and structural designs for maximizing solar energy conversion and harvesting. Modern solar thermal and photovoltaic system technologies and supplies are examined to show how alternative electricity has become less expensive and more sustainable. The primary focus is on complex ideas like multiple junctions and tandem solar cells, which increase the efficiency of single-junction systems. The review paper investigates innovative solar power storage solutions, involving battery technology and energy storage materials, to meet the increasing need for secure and easily available sources of clean energy. The research paper explores the technology and uses of flat plate collectors, tube collectors, and solar power plants and how those are used in residential and commercial solar thermal systems. Solar energy conversion efficiency and sustainability will improve with innovations in materials and architecture. Building-integrated photovoltaics (BIPV) is one of the easiest solar system architectures that can be integrated into any residential or commercial building. Quantum dot solar cells, photovoltaic (PV) solar energy frameworks, such as CIGS thin-film solar cells, and organic photovoltaics (OPVs). Organic photovoltaics are portable and lightweight but have a low energy conversion rate, whereas quantum dot solar cells have a high energy conversion rate but face fabrication challenges.

Experimental and numerical analysis of the thermal performance of pebble solar thermal collector

In this work, pebbles of higher specific heat than the conventional absorber materials like aluminium or copper are proposed as a absorber in the solar flat plate collector. The proposed collector are integrated into the building design and constructed with masonry. Tests were conducted by varying the operating parameters which influence its performance, like the flow rate of the heat-absorbing medium, and the tilt of the collector using both coated and uncoated pebbles. The maximum temperature difference that could be measured for a conventional absorber was approximately 8 °C for a flow rate of 0.6 L/min. While for a coated and uncoated absorber, it was 7 °C and 5.5 °C respectively. This difference decreased with an increase in flow rates from 0.6 L/min to 1.2 L/min. For all the flow rates, it was observed that the average difference in efficiency between the coated and the conventional absorber collector is 5.82 %, while the difference between the coated and uncoated absorber collector is 15.68 %. Thus, it is very much evident that by replacing the conventional absorber with the proposed coated pebble absorber, the overall loss in efficiency is just 5.82 %, but the advantages are enormous. Along with the experimental study, numerical analysis was also carried out with CFD modeling. The numerical results agreed well with experimental results with the least error. Therefore, CFD simulation can be further used to optimize the design of the collector.

Exploring the use of hybrid nanofluid in flat plate collector for sustainable energy harvesting: An experimental investigation

Application of hybrid nanofluid work as a performance booster of solar collector and also provide an opportunity of sustainable development of eco-friendly energy harvesting. The performance of Flat plate solar collector (FPSC) has been investigated experimentally at different combinations of flow rate, intensity of radiation and angle of inclination. The comparative performance analysis of FPSC with two different working fluids i.e. distilled water and Cu-MWCNT hybrid nanofluid have also been made. The best combination of the operating parameters has been identified for performance optimization. The mathematical co-relations between the efficiency of the FPSC with the operational parameters has also been studied. Contribution in prevention of greenhouse gases emission also calculated along with energy saving. Carbon credit contribution also identified for the used solar collector. The efficiency of operation with hybrid nanofluid as working fluid was better compared to the distilled Water. Hybrid nanofluids provided higher rise in temperature as well as the useful energy gain compared to the distilled water. The flow rate was identified as dominant factor for efficiency. The efficiency of the collector was a linear function with reduced temperature. Higher efficiencies were achieved at higher flow rates with minimum inclination angle.

Heat enhancement in solar flat plate collectors – A review

Heat enhancement in solar flat plate collectors – A review

Energy, exergy, environmental, and economic (4E’s) analysis of a solar driven humidification-dehumidification desalination system: An experimental investigation

A solar-driven humidification-dehumidification (SDH-DH) desalination system has shown to be a highly efficient and viable solution to meet the freshwater needs of a community. However, the solar air heater based on flat plate collector, imposes constraints on their efficiency. The current work focuses on the development of an SDH-DH desalination system. This system is comprised of a solar air heater that utilizes a double-ends open evacuated tube collector, a humidifier equipped with cellulose pad packing material, and a dehumidifier based on a direct evaporative cooler. The current SDH-DH desalination system is operated in two modes, namely open loop and closed loop, at four distinct process air flow rates. The system's performance indices are evaluated based on energy, exergy, environmental and economic analysis. The solar air heater is capable of generating hot air at an approximate average temperature of 100 °C, while maintaining an airflow rate of 150 kg/h. This enhances the efficiency of the humidifier, resulting in a freshwater production rate of about 2.43 L/m2/day at a cost of 0.027 $/L. Moreover, the use of an evaporative cooler-based dehumidifier effectively mitigates the issue of fouling that arises during the condensation process. The system achieved the maximum mean energy efficiency of 25.39 % and exergy efficiency of 4.59 % in a closed loop configuration, with an air flow rate of 150 kg/h. The total CO2 reduction amounts to 119.08 tons during the designated duration.

Numerical analysis of thermo hydro-dynamics behavior of solar flat plate collector with square and V-cut twisted tape inserts

Numerical analysis has been conducted for a solar collector with two circular pipes having semi-circular contact with absorber plate. The tubes are analyzed with and without the inclusion of twisted tape inserts of twist ratio Y = 3 and Y = 4. The comparison between the heat transfer and pressure drop characteristics of a plain tube to that fitted with the twisted tape inserts is done and validated against experimental results with good agreement. Additionally, helical twisted tape is modeled with square- and V-cut to analyze its influence on flow and heat transfer phenomenon. V-cut twisted tape inserts act as turbulence promoters, increasing fluid flow and inducing vortex-like motion. As a result, boundary layer around the absorber plate is disrupted with decrease in stagnation temperature, resulting in better heat transfer and more effective absorption and conversion of solar energy. The Nusselt number, friction factor, and heat transfer coefficient variation with the Reynolds number have been studied for the given heat fluxes. It is found that the Nusselt number of the fluid flowing in the plain tube is increased by 76.44% when the tube is fitted with twisted tape inserts. The pressure drop in the tube is found to increase with the presence of the twisted tapes. The average temperature along the length of the circular tube and absorber plate has also been reported.

Experimental study of eco-friendly insulating materials for solar thermal collectors: A sustainable built environment

The typical solar flat plate collector relies on materials like rock wool for insulation to minimize heat loss. However, the use of such inorganic materials raises substantial concerns for both the industry and the environment. Therefore, it is crucial to decrease the reliance on these inorganic materials and instead adopt readily available biodegradable materials that pose no environmental risks to the system. The current research presents the usage of agricultural waste as insulating materials for S-FPC fabrication. The novelty of this current research work is the effective utilization of agriculture waste (rice husk, stubble fibre, coco-peat, and nitrile rubber) as an insulating material for the fabrication of S-FPC. Experiments were performed with insulating thicknesses of 50 mm and 70 mm. The optimum temperature was recorded to be 50–53 °C with an average thermal efficiency of 64–66 % by using rice husk as the insulating material at 70 mm thick.

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.

Statistical analysis of solar thermal collectors in the Solar Keymark Database

Experimental, analytical, or numerical investigations are ordinarily conducted to reveal optimisation potential for solar thermal collectors. At the same time, the ‘Solar Keymark Database’ contains more than 2,000 test reports from certified laboratories featuring properties including thermal efficiency, dimensions, or optical properties. This dataset offers untapped potential for statistical analyses as an alternative optimisation approach. Hence, this paper aims to provide a) the first statistical findings of solar thermal collector properties listed in the Solar Keymark Database and b) insights into statistical relations between these properties. The key correlations observed from the analysis of flat-plate collectors were between efficiency and both gross height (R=0.30) and gross area (R=0.27). We concluded that preferable collector designs may be featured with larger area to height ratios. The analyses of evacuated tube collectors revealed a strong correlation between efficiency and transversal incidence angle modifier (R=-0.65) as a result from different tube spacing. It was noticeable that the quasi-dynamic test method reported significantly higher efficiencies (7.14 percentage points) for evacuated tube collectors, which should be carefully considered for future test procedures. Overall, the statistical analysis was in accordance with conventional bottom-up analyses and revealed insightful dependencies for the present collector data.

Affordable lab-scale electrospinning setup with interchangeable collectors for targeted fiber formation

The electrospinning method is increasingly in demand due to its capability to produce fibers in the nanometer to micrometer range, with applications in diverse fields including biomedical, filtration, energy storage, and sensing. Many of these applications demand control over fiber layout and diameter. However, a standard flat plate collector yields random fibers with limited control over diameter and density. Other viable solutions offering a higher level of control are either scarce or substantially expensive, impeding the accessibility of this vital technique. This study addresses the challenge by designing an affordable laboratory-scale electrospinning setup with interchangeable collectors, enabling the creation of targeted fibers from random, aligned, and coiled. The collectors include the standard flat plate and two additional designs, which are a rotating drum and a spinneret tip collector. The rotating drum collector has adjustable speed control to collect aligned fibers and exhibits stability even at high rotational speeds. The spinneret tip collector was designed to produce helically coiled fibers. The setup was validated by directed fiber formation using polycaprolactone (PCL), a biodegradable and FDA-approved polymer. Overall, the uniqueness of the design lies in its affordability, modifiability, and replicability using readily available materials, thus extending the reach of the electrospinning technique.

Solar flat plate collector's heat transfer enhancement using grooved tube configuration with alumina nanofluids: Prediction of outcomes through artificial neural network modeling

Solar thermal systems are far more important than solar PV systems in residential and commercial applications. Improving the efficiency of solar thermal technology is a major challenge. Several researchers separately studied the effects of turbulence enhancers and nanofluids to enhance heat transfer of solar flat plate collectors (SFPC). The current research focuses on the synergic effect of an internally grooved absorber tube and Al2O3-WEG-based nanofluid on SFPC performance. The experimental investigation used various concentrations of nanoparticles (0.01 %, 0.05 %, 0.1 %, and 0.2 %) and mass flow rates (MFR) (0.024 kg/s, 0.036 kg/s and 0.048 kg/s). The outcomes of Al2O3-WEG based nanofluid and plain working fluid were compared. MFRs of 0.036 kg/s and 0.2 % vol. Showed the highest efficiency for SFPC models 1 and 2. The efficiency enhancement of model 2 over model 1 of plain fluid increased in an order of 46.37 %, 54.13 %, and 33.83 % for MFRs of 0.024, 0.036, and 0.048 kg/s, respectively. The maximum efficiency enhancement of model 2 over model 1 was 54.1 % for a MFR of 0.036 kg/s with 0.2 % vol. The created ANN models predicted the output values of the SFPC experiment accurately in real-time.

Optimizing solar energy for wood drying under various climates: A comparative study of flat plate and photovoltaic thermal solar collectors

Wood drying is an important operation in many sectors, and harnessing solar energy for this purpose has received a lot of interest due to its sustainability and cost-effectiveness. In this work, we compare how two solar collector configurations namely, Flat Plate Collector and Photovoltaic Thermal collector, perform in a solar wood drying system. The moisture content of wood was reduced from 73% to 12% in four different regions: Errachidia, Meknes, Tangier, and Rabat. The Gauss–Seidel method is used to solve the governing equations for heat transfer after discretizing them via implicit finite differences. The effectiveness of the solar collectors was simulated through the TRNSYS software, and a numerical program was generated using the Python programming language. According to our research, the FPC beats the PVT collector because of its higher output temperatures dramatically shorten the time it takes for wood to dry. The study emphasizes how temperature and humidity affect drying, showing that faster drying occurs in hotter, drier locations. Furthermore, drying time can be saved by using FPC and PVT collectors compared to conventional open sun drying.The primary conclusions of this research are: In the FPC solar dryer, the drying time needed in Errachidia, Meknes, Rabat and Tangier was 144 h, 162 h and 171 h, respectively. While in the PVT solar dryer, it required 162 h in Errachidia, 171 h in Meknes, 180 h in Rabat and 189 h in Tangier. Further, the FPC collectors showed a range of 293 K to 347 K for the outlet temperature. The PVT collectors, however, showed a variable range between 295.9 K and 320 K. The drying periods and temperature ranges examined revealed that Errachidia was the most advantageous location, regardless of whether FPC or PVT collectors were used. In fact, the drying time that can be saved by using FPC is 41% while PVT is 31% compared to traditional open sun drying.

Machine learning models for predicting the performance of solar-geothermal desalination in different meteorological conditions

This research aimed to evaluate the amount of produced fresh water (FWP) in a desalination system based on humidification-dehumidification using TRNSYS software. The study was conducted for one year, analyzing the results for five cities in Iran with different climatic conditions. Meteorological data from Meteonorm software were used for the simulation. Different heating sources, including solar energy (SE) and geothermal energy (GE), were considered in the design. The impact of using three types of collectors and the simultaneous use of SE and GE heating sources was investigated. The findings showed that using a flat plate solar collector resulted in the highest FWP in June and July, as well as during certain day time hours with increased solar radiation intensity. Increasing the number of flat plate collectors and their cross-sectional area intensified the FWP about 10.60%–33.16%. When SE and GE were used as heat sources, increasing the mass flow rate of water and air entering the system led to a decrease and increase in FWP, respectively. The highest FWP for Hamedan city was achieved when using GE simultaneously with a compound parabolic collector. Exergy destruction was analyzed for humidification and dehumidification devices, with the maximum observed in the case of Type74. The LSTM deep learning neural network and the Gaussian process (GP) machine learning algorithm were used to approximate the desalination efficiency, with the GP method exhibiting slightly higher accuracy.

Effect of Changing the Water Flow Rate on the Efficiency of Hybrid PV/T Uncovered Collectors without Glasses: Numerical Study

The flat-plate collector is one of the most frequent types of collectors because it is simple to manufacture and it is relatively inexpensive in comparison to other collectors. The primary objective of this work is to improve the collector's efficiency, which can be accomplished by increasing the heat transfer quantitatively. This can be accomplished by increasing the efficiency of the collector. In this research employs hybrid photovoltaic panels through electrical generation and, on the other hand, takes advantage of the lost heat, which has reduced efficiency to useful heat, by transporting them through fluid and benefiting from them through industrial and domestic applications. The model was studied numerically by ANSYS computational code, where simulations were carried out on CFD and steady state thermal, as well as the effect of solar radiation, at a value of 10, on the layer of photovoltaic cells. Besides, several values of flow rate (0.02, 0.025, and 0.03) were used and compared. The current findings show that the efficiency of the current panel under consideration increased significantly, and the value of flow of 0.03 was the optimal value that led to obtaining suitable efficiency and a relatively acceptable water temperature.

Techno-economic analysis of hybrid solar thermal systems with flat plate and parabolic trough collectors in industrial applications

Hybrid configurations that combine two different solar thermal collector technologies are considered to improve the economic competitiveness of solar systems in district heating applications. However, the performance of these systems in the industrial sector has been scarcely studied. This study evaluates the energetic and economic potential of hybrid systems with flat plate and parabolic trough collectors under different industrial process temperatures and radiation levels. To enable this evaluation, a hybrid field sizing methodology was developed. The results showed that the hybrid system could achieve high solar fractions with a lower levelized cost of heat than parabolic trough collector individual systems and smaller solar field areas than flat plate collector individual systems. Furthermore, the hybrid system with approximately 50% flat plate collectors reached monthly solar fractions up to 91% higher than the individual flat plate collector alternative. The seasonal performance demonstrates that the hybrid configuration could have great potential for applications with higher demand in the summer months, such as solar cooling with absorption chillers and solar water desalination for crop irrigation. This study contributes to the understanding of the potential of hybrid systems in the industrial sector and presents tools and insights for future research of hybrid solar thermal configurations.