Flat Plate Solar Thermal Collectors Research Articles

Novel application for graphene oxide-based ionanofluids in flat plate solar thermal collectors

This study presents new ionanofluids (INF) composed of 1-ethyl-3-methylimidazolium acetate ionic liquid (IL) and graphene oxide (GO) nanoparticles which have been assessed for the first time in an experimental flat plate solar thermal collector (FPSC). For this purpose, four types of INFs were synthesized, maintaining a constant concentration of GO nanoparticles dispersed in different base fluids: ionic liquid (IL/GO), a mixture of ionic liquid and water in varying concentrations (IL-water (75–25)%/GO and IL-water (50–50)%/GO), and water (Water/GO). These four INFs were characterized and their thermophysical and physicochemical properties were determined. The results indicated a 37.4% improvement in efficiency and up to a 2.5-fold increase in temperature within the collector when the IL was applied exclusively as the base fluid, compared to water. Furthermore, IL/GO demonstrated excellent stability, showing no signs of deterioration or nanoparticle precipitation two years after preparation and testing. These findings suggest that INFs based on IL and GO nanoparticles significantly enhance the efficiency of FPSC, presenting a promising option for solar energy applications and opening a new research avenue for INFs in the production of domestic hot water.

A holistic methodology for designing novel flat plate evacuated solar thermal collectors: Modelling and experimental assessment

This paper presents a comprehensive analysis of the design, implementation, experimentation, and optimization of a novel evacuated flat-plate solar thermal collector characterized by a vacuum level between the glass cover and the absorber plate. The paper addresses different research themes, primarily focusing on developing a low-cost evacuated solar thermal collector with a high innovation level. Additionally, it introduces a comprehensive approach for the conceptualization, design, fabrication, testing, and optimization of solar thermal collectors. Specifically, this study aims to highlight the characteristics of a vacuum-enhanced solar thermal collector and demonstrate a step-by-step process involved in its design, fabrication, testing, and optimization. The proposed methodology is based on the adoption of two software tools and an extensive experimental analysis: the commercial software ANSYS is utilized for structural analysis, while MatLab is employed to develop a suitable mathematical tool for assessing the energy performance of the system and optimizing it. The outcomes show the reliability of the methodology and the performance of the low-cost evacuated solar thermal collector under different vacuum levels, providing insights into energy, economic, and environmental aspects. This work innovates by presenting a thorough analysis covering all solar thermal collector production phases, from conceptualization to optimization. The conclusions highlight the production of a reliable approach, and proof-of-concept results demonstrate how increasing the vacuum level enhances the thermal efficiency of a solar collector.

Literature review of potential materials for the construction of an alternative flat-plate solar collector

Through systematic review method the article presents the potential of existing solar energy in Mozambique for use in water heating with the integration of thermal energy storage systems that are currently being investigated. It emphasizes the need for affordable materials in building solar collectors for Mozambique’s homes, leveraging the country’s solar potential to reduce electricity consumption and environmental impact for sustainable development. It explores current research on thermal energy storage systems for solar water heating and reviews alternative materials for solar collectors based on their properties, cost, and availability. The importance of thermal energy storage in solar collectors for efficiency and load balancing is highlighted., it discusses and list the potential alternative materials for the construction of flat plate solar thermal collectors from roofing material, frame, absorber, pipes, and heat storage material according to their thermophysical properties, costs, and availability in the Mozambican market in the context of industrialization.

Use of carbon nanotubes in flat and evacuated tube solar collectors for thermal enhancement: A review

Solar thermal collectors (STCs) are a potential heating and cooling solution owing to their pollution-free nature and availability in many parts of the globe. Enhancing the thermal efficiency of STCs is crucial for optimizing energy conversion. In this respect, the purpose of this article is to provide an overview of the usage of carbon nanotubes (CNTs) for the enhancement of thermal performance in evacuated tube and flat plate solar thermal collectors. According to the research that was conducted earlier, it was discovered that the use of CNTs, both single-walled and multi-walled, results to increases the efficiency of a flat and evacuated solar thermal collector. In this article, the impact of carbon nanotubes (CNTs) was investigated in depth for their potential usage in flat and evacuated tube solar collectors (ETSCs). This review article offers a novel aspect based on extensive research that has been published in the past related to the impact of CNTs on the thermal performance of flat and ESTCs.

Renewable process heat from solar thermal: Poultry slaughterhouse processes

Jordan faces pressing energy challenges, characterized by a substantial dependence on imported resources. This paper addresses these challenges by examining the potential integration of solar thermal energy systems into poultry slaughterhouses, using a representative case study. The study starts by providing a brief background on Jordan's energy challenges and the rationale for exploring solar thermal applications in the poultry industry. The methodology involves a meticulous analysis of existing processes in the slaughterhouse, followed by the necessary calculations for integrating a solar thermal flat plate collector. Validation is performed through T*SOL and Polysun simulations, accompanied by a comprehensive economic analysis. The proposed flat plate collector-based system demonstrates the capacity to cover approximately 72% of the facility's annual energy requirements, resulting in substantial savings of 1,926,396 kWh per year, equivalent to 330,318 L of diesel. Simulation results indicate a concise payback period of 3.8 years and net profits approximately 6.6 times the initial investment over a 25-year span. Beyond economic benefits, the adoption of solar technology leads to an 84% reduction in annual CO2 emissions, underscoring its environmental advantages. The study also sheds light on a notable lack of awareness about solar thermal technology, emphasizing the need for knowledge dissemination to foster global renewable energy adoption.

Enhanced performance of photovoltaic thermal module and solar thermal flat plate collector connected in series through integration with phase change materials: A comparative study

The decline in photovoltaic cell efficiency due to temperature elevation, coupled with solar energy's inherent intermittency, presents challenges for solar systems, including photovoltaic panels and solar thermal (ST) collectors. The integration of phase change materials (PCMs) emerges as a promising solution to enhance thermal energy storage and regulation, thereby improving system performance and sustainability. This study investigates the performance of series-connected photovoltaic thermal (PVT) and ST systems with integrated PCMs from energy and exergy viewpoints, utilizing a 3D transient numerical simulation. The proposed system's performance is compared with that lacking a PCM across various heat transfer fluid mass flow rates. Suitable PCM selection based on melting temperature is explored, along with PCM layer thickness and nanoparticle augmentation. The research highlights that PCM integration effectively regulates PV cell temperature, enhancing electrical power and exergy rate. While increasing the mass flow rate improves thermal and electrical power, it reduces the thermal exergy rate. Comparing different PCMs (RT28 HC, RT35 HC, and RT44 HC), the RT28 HC PCM provides the lowest temperature of PV cells and the best electrical performance during the day. Moreover, increasing PCM layer thickness results in lowering PV cell and outlet temperatures and storing more heat. Nanoparticles added to PCMs lead to a marginal improvement in energy and exergy, especially for the system with RT28 HC. This analysis emphasizes PCM integration's role in enhancing solar thermal system performance, highlighting the importance of considering the PCM's melting temperature for effective thermal energy management.

Energy and exergy assessment of a flat plate solar thermal collector by examine silicon carbide nanofluid: An experimental study for sustainable energy

The main reason behind the inefficient performance of heat transfer devices was the use of conventional fluids with poor heat transfer properties. However, remarkable improvement in efficiency was observed in thermal devices when these fluids were replaced by nanofluids with good thermal transfer properties. Various kinds of nanoparticles were used due to their increased thermal conductivity. Such nanofluids are particularly exploited in renewable energy systems like solar collectors. The most frequently used solar collectors in thermal applications are FPSCs. The current experimental research investigates how the use of nanofluids of SiC/DW impact the efficiency of a flat plate solar collector functioning in the climatic environment of Gödöllő, in Hungary. Firstly, the synthesis of nanofluid based on distilled water that contained nanoparticles of SiC (with a size 45–60 nm) at volume fractions of 0.025 %, 0.05 %, 0.075 %, and 0.1 % was performed. Various measurement instruments were used to test the thermophysical characteristics and stability. In the subsequent stage, thermal and exergy efficiencies tests were conducted on the solar collector with a range of mass flow rates including 0.025, 0.033, and 0.041 kg/s in which the collector’s efficiency was calculated according to the ASHRAE standard 93–2003. This developed collector was subjected to different flow rates, and nanoparticle concentrations to find out the effect of nanofluids on the thermal and exergy efficiencies of the solar collector. The findings indicated that an increase of up to 30.3 % was achieved in the fluid’s thermal conductivity through the addition of nanoparticles of SiC. The collector’s thermal efficiency was maximised at 77.43 % when the value of [(Ti – Ta)/GT] was zero for a volume fraction (φ) of 0.1 % and mass flow rate of 0.041 kg/s, which represented a 35.53 % increase over the base liquid. Additionally, an increase of 37.4 % was recorded for the exergy efficiency at volume fraction (φ) of 0.1 % than its value in distilled water. Ultimately, the heat transfer properties of the device showed improvement.

Enhanced Performance of Nickel–Cobalt Oxides as Selective Coatings for Flat-Plate Solar Thermal Collector Applications

Solar thermal collectors represent a practical option to capture energy from the sun, providing low-cost domestic and industrial heating and decreasing the dependency on fossil fuels. Spinel-type metal oxides show interesting physicochemical properties and so can be used as active materials for converting solar energy to electrical, chemical, and heat energy. We report the synthesis and characterization of nickel–cobalt mixed metal oxides used as an active phase in selective paints for solar absorber coatings applied to a domestic flat collector. The nickel–cobalt mixed oxides crystallized in the cubic phase related to the spinel structure, exhibiting good thermal stability and reproducibility. These mixed oxides presented oxidation states (2+ and 3+) for both nickel and cobalt. The coatings fabricated from the selective paints based on nickel–cobalt mixed oxides showed a solar absorptance value of 94%, while for the commercial paint Solkote®, the value was 93%. A representative coating based on the NiCo2O4 composition was evaluated for the first time in a domestic-type flat solar collector for water heating under real operating conditions, achieving an outstanding performance that competes with that of commercial collectors. The potential application of nickel–cobalt mixed oxides in solar collectors opens up new opportunities for future innovations and developments in functional absorber coatings.

Multicriteria Analysis of a Solar-Assisted Space Heating Unit with a High-Temperature Heat Pump for the Greek Climate Conditions

The goal of this investigation is the thorough analysis and optimization of a solar-assisted heat pump heating unit for covering the space heating demand for a building in Athens, Greece. The novelty of the studied system is the use of a high-temperature heat pump that can operate with radiative terminal units, leading to high thermal comfort standards. The examined system includes flat-plate solar thermal collectors, an insulated thermal storage tank, auxiliary electrical thermal resistance in the tank and a high-temperature heat pump. The economic optimization indicates that the optimal design includes 35 m2 of solar thermal collectors connected with a storage tank of 2 m3 for facing the total heating demand of 6785 kWh. In this case, the life cycle cost was calculated at 22,694 EUR, the seasonal system coefficient of performance at 2.95 and the mean solar thermal efficiency at 31.60%. On the other hand, the multi-objective optimization indicates the optimum design is the selection of 50 m2 of solar field connected to a thermal tank of 3 m3. In this scenario, the life cycle cost was calculated at 24,084 EUR, the seasonal system coefficient of performance at 4.07 and the mean solar thermal efficiency at 25.33%.

Design, fabrication and investigations of natural convection step serrated fin plate integrated trough array low-cost collector for solar air heating: An application to agricultural crop drying

This paper establishes the design modification procedure for flat plate solar thermal collector and investigates the performance by incorporating a specially designed low-cost Step Serrated Fin Plate Integrated Trough Array (SSFPT) on the sun-facing side of the collector. The idea of integrating trough profile on the step serration is for concentrating heat radiations with a latent heat storing copper pipe at its focal point filled with phase change material, giving tremendous improvements and high thermal and exergy efficiencies. Also, the step serrated fins increase air stagnation and heat acquisition. The performance of the SSFPT collector solar air heater is experimentally investigated and compared with the conventional Flat Plate Collector Solar Air Heater (FPC SAH) of the same collector area by natural convection. The average outlet temperature of SSFPT collector SAH and FPC SAH varies from 44.5 to 74.5 °C and 38.0–48.2 °C and the average stagnation temperature lies between 43.1 and 74.4 °C and 38.5–48.5 °C. The maximum thermal and exergy efficiency of SSFPT SAH is 66.32 % and 23.06 %. This proposed collector achieves a maximum Nusselt number of ∼ 7.11 at Rayleigh number ∼ 441.5 × 103 and a better augmenting effect with a thermo-hydraulic performance factor of 1.4 after 4 h of operational time. The thorough economic analysis yields cost per kWh of the SSFPT collector is 0.10$ which is 0.18$ lesser than conventional FPC SAH.

Graphene nanoplatelet nanofluids stabilised by hybridisation with graphene oxide: preparation, stability, and performance in flat plate solar thermal collector

Graphene nanoplatelet nanofluids stabilised by hybridisation with graphene oxide: preparation, stability, and performance in flat plate solar thermal collector

Experimental characterization of a solar still integrated with a spiral collector using energy, exergy, economic, and environmental (4E) analyses

In this study, an efficient and innovative flat-plate spiral solar thermal collector is integrated into a conventional solar still (CSS) system to substantially increase the potable water without increasing the associated cost. The integrated solar still is experimentally characterized in its daily operation using a complete energy, exergy, economic, and environmental (4E) analyses. The performance of the integrated solar still is compared with two other cases, a conventional solar still and a solar still linked to an internal condenser, for various saline water depths and volume flow rates of the collector and condenser. The results show that the total productivity of potable water around 24 h for the new system is 7325 mL which is significantly higher than that of the conventional solar still (860 mL) and the solar still with an internal condenser (1895 mL). Furthermore, it is found that the daily energy (exergy) efficiency of the proposed solar still is 17.23 % (2.77 %) higher than that of the conventional system. In addition, for the introduced system, the energy payback time decreases by 1.58 years and CO2 mitigation increases by 3548.6 kg compared to the conventional system.

Utilization of zinc-ferrite/water hybrid nanofluids on thermal performance of a flat plate solar collector-a thermal modeling approach.

Thermodynamic performance analysis is carried out on a flat plate solar thermal collector utilizing single and hybrid nanofluids. Fe2O4/water, Zn-Fe2O4/water hybrid nanofluids, and water are used as heat transfer fluids, and their performance is compared based on the energy and exergy transfer rate. The thermo-physical properties are evaluated by regression polynomial model for all the working fluids. Developed codes in MATLAB are created to solve the collector's thermal model iteratively, energy, and exergetic performance. The system is then subjected to parametric investigation and optimization for variations in fluid flow rate, temperatures, and concentrations of nanoparticles. The findings show that utilizing Zn-Fe2O4/water hybrid nanofluids with a particle concentration of 0.5% enhanced the solar collector's thermal performance by 6.6% while using Fe2O4/water nanofluids raised the collector's thermal performance by 7.83% when compared to water as the working fluid. The maximum energy efficiency of 80.1% is attained at the mass flow rate of 0.1 kg/s. The hybrid nanofluids have also given a maximum exergetic efficiency of 5.36% and an enhancement of 8.24% compared to Fe2O4/water nanofluids. It evidences that the hybrid nanofluids would become a better thermal alternative for water as well as single nanofluids.

The 3E Optimal Location Assessment of Flat-Plate Solar Collectors for Domestic Applications in Iran

The analytical hierarchy process (AHP) was utilized to determine the optimal location on which to install flat-plate solar thermal collectors for residential buildings in a number of cities in Iran under diverse climatic conditions. The payback period of investment (IPBP) was chosen as one of the decision criteria, while payback periods of energy and greenhouse gas emissions (EPBP and GGEPBP), being two recently introduced concepts, were also taken into account to provide a broader insight from the energy, economic, and environmental (3E) benefits of the system. The novelty of this work is proposing a method to find places with the greatest potential to install flat-plate solar collectors. It was performed using AHP as a systematic decision-making tool, and based on energy, environmental, and economic criteria, which are the key aspects of an energy system. Codes developed in the MATLAB software were employed to determine the values for different investigated cities. According to the results, Yazd, located in the center of the country, was found to be the best place to install the system. This city enjoys EPBP, IPBP, and GGEPBP scores of 2.47, 3.37, and 0.71 years, respectively. The collector area for this city was also found to be 109.8 m2. Yazd gained a score of 26.5 out of 100. With scores of 24.4, 18.6, 15.9, and 14.6 out of 100, Tehran, Bandar Abbas, Rasht, and Tabriz were found to be the second, third, fourth, and fifth priorities for utilizing the system, respectively.

Heat Transfer Analysis of the Flat Plate Solar Thermal Collectors with Elliptical and Circular Serpentine Tubes

In this study, the heat transfer characteristics of the flat plate collectors with circular and elliptical serpentine tubes are theoretically analyzed and compared in terms of m˙, Re, Nu, hfi, FR, Qu, and μTh under various water flow rates and the standard test conditions. The results reveal that the maximum μTh correspondence to the elliptical serpentine design with 56% under turbulent flow, and the minimum μTh of 47% for the circular cross-section under laminar flow. In addition, it was found that the highest useful energy gain per unit time (493.8 W) through the system is possible when FR, hfi, Nu, and m˙ are maximum and vice versa. It was concluded that, at the same area, the larger contact area in the elliptical cross-section compared to the circular would improve FR and Qu by an average of 2%. Overall, it is crucial to evaluate the thermal parameters of the thermal collector during the preliminary design stage to fabricate a highly efficient system and save time as well as initial cost.

First test field performance of highly efficient flat plate solar collectors with transparent insulation and low-cost overheating protection

The present work demonstrates prototypes of highly efficient flat plate solar thermal collectors prototypes based on transparent insulation materials (TIM) technology for efficiency improvement and an overheating protection system. The design and optimization of the collectors have been numerically carried out using a previously developed simulation tool based on an in-house software platform (NEST) capable of simulating all the entities constituting the system as a whole and using efficient coupling between the elements. Three design variants for the demonstration have been previously tested under laboratory conditions. These collectors are then mounted on the roof of a hospital building. Their performance is comparatively tested along with a conventional flat plate solar collector, under actual meteorological conditions and during long periods. The energy collected is about 2.5 and 1.4 times higher than standard collectors in winter and spring. Thus, due to the long-term exposure of the collectors, aspects such as reliability, durability, energy performance, and correct functioning of the protection system have been analyzed to improve the detected shortcomings for the future generations of the present design.

Design and experimental evaluation of a PV /T system cooled by advanced methods

Photovoltaic thermal (PV/T) systems combine a hybrid photovoltaic (PV) module and a flat-plate solar thermal collector. The hybrid design allows for simultaneou increase in thermal energy while providing cooling for the PV module. In doing so, the PV module temperature drops, and therefore the electrical efficiency increases. Another benefit of PV/T collectors is that they allow for the usage of thermal, and PV module in the same area and so that saved space for the consumer. This study presents a numerical (CFD) design and experimental evaluation of a PV/T system cooled by nano-PCM and nanofluid. The selected nanomaterial and PCM were nano-silicon carbide (SiC) and paraffin, respectively. Nano-silicon carbide particles were employed with the paraffin to ameliorate its thermal conductivity. The study examined various aspects of the system such as the SiC particles' optimal mass fraction suspended in both water (base fluid) and paraffin, the optimum mass flow rate of nanofluid, voltage and current of the PV module, thermal energy of solar thermal collector, and the combined PV/T efficiency. The numerical and practical results were very close, which proves the validity of the hypotheses used in building the program. The significance of this study is demonstrated by the result as this design led to maximum thermal and electrical efficiencies of 72% and 13.7%, respectively. The proposed PV/T system introduced better stability of the generated power and thermal efficiency at peak time than the other two studied systems.

Evaluation and comparison of performance of a solar pebble absorber collector with a conventional flat plate collector

The present study deals with the replacement to the absorber material of a conventional Solar Thermal Flat Plate collector by a low cost zero emission naturally available material. Here the emphasis is on reducing the emission that is generated while excavating and fabricating the absorber material for the flat plate collectors (FPC) by replacing it with a naturally available material without sacrificing much on the performance of the collector. Also, since the proposed material is directly used in its natural form without much modification, its cost is much less than that of the cost of the absorber of a conventional FPC. This reduces the overall cost of the FPC with the replaced absorber. The natural material proposed are the pebbles which are extensively used in solar energy storage systems because of their high heat absorbing capacity but have never been used as the absorber material in a FPC. Thus, this is an endeavor to replace and study the performance of a FPC with the proposed pebble absorber with and without coating of the pebbles and comparing the same with that of a conventional FPC using the conventional Copper absorber. During the study it is evident that the proposed coated pebble absorber is as good as that of a conventional absorber thus making it a cheap and nonpolluting alternative to the costly polluting absorber of a conventional FPC.

Multifunctional Magnetic Nanocolloids for Hybrid Solar-Thermoelectric Energy Harvesting.

Present environmental issues force the research to explore radically new concepts in sustainable and renewable energy production. In the present work, a functional fluid consisting of a stable colloidal suspension of maghemite magnetic nanoparticles in water was characterized from the points of view of thermoelectrical and optical properties, to evaluate its potential for direct electricity generation from thermoelectric effect enabled by the absorption of sunlight. These nanoparticles were found to be an excellent solar radiation absorber and simultaneously a thermoelectric power-output enhancer with only a very small volume fraction when the fluid was heated from the top. These findings demonstrate the investigated nanofluid’s high promise as a heat transfer fluid for co-generating heat and power in brand new hybrid flat-plate solar thermal collectors where top-heating geometry is imposed.

Fabrication analysis of flat vacuum enclosures for solar collectors sealed with Cerasolzer 217

Vacuum flat plate (VFP) solar thermal collectors exhibit excellent optical and thermal characteristics due to a combination of wide surface area and high vacuum thermal insulation offering a high performance and architecturally versatile collector with a variety of applications for industrial process heat and building integration. A vacuum flat plate solar collector consists of a solar absorber in a flat vacuum enclosure comprising glass or glass and metal covers sealed around the periphery with an array of support pillars to maintain the separation of the enclosure under atmospheric pressure. The edge seal must be both mechanically strong and hermetic to ensure the durability of the internal vacuum over collector lifetime. This presents several challenges for the fabrication of flat vacuum enclosures. In this study a novel sealing technique is presented using a tin-based alloy, Cerasolzer 217, to create the vacuum seal between two glass panes and an edge separating spacer. The sealing process is undertaken at temperatures ≤250 °C allowing the use of thermally tempered glass panes. The mechanical strength of the edge seal was investigated using a tensometer. It was demonstrated that the bond between glass and edge spacer was sufficiently strong to withstand induced stresses in the edge seal region. The edge seal was leak tested using a conventional Helium mass spectrometer leak detector and was shown to possess leak rates low enough to maintain an adequate vacuum pressure to supress conductive and convective heat transfer in the collector. A finite element method (FEM) is developed and validated against the experimental results and employed to predict the stresses in different regions of the enclosure. It was found that the mechanical strength limits of the seal and glass are higher than the stresses in the edge seal region and on the glass surface, respectively.