Conventional Flat-plate Collectors Research Articles

Transparent insulation integration in solar thermal collector: Advancing performance for domestic water heating in oceanic climates of Western Europe

Decarbonizing residential hot water demand requires efficient solar collectors. Conventional flat plate collectors are widely available but experience high heat losses in colder climates. This work investigates the performance of a modified flat plate collector that incorporates honeycomb transparent insulation to reduce convective heat loss, offering a cost-effective alternative to energy-efficient evacuated tube collectors. The thermal performance of the modified flat plate collector was obtained using the finite element method in COMSOL Multiphysics, revealing a significant reduction in convective heat loss. The obtained thermal performance was then incorporated into a transient simulation to assess the year-around performance of the modified flat plate collector in a solar domestic hot water system for Irish climate. The transient simulation accounted for variations in the transparent insulation’s transmission with incidence angle which was overlooked in previous studies. Over a year-long simulation, the modified flat plate collector generated a total useful energy of 532.45 kWh m−2, while requiring 1640 kWh of auxiliary energy to meet the hot water demand of a single-family house in Ireland. An economic analysis of solar domestic hot water system revealed that the modified flat plate collector could yield savings of 443.44 € more than the standard flat plate collector and 3281.03 € more than the evacuated tube collector for homeowners. Consequently, the simple payback period for the solar domestic hot water system decreased from 3.72 years with a standard flat plate collector and 8.37 years with an evacuated tube collectors to 3.56 years with a modified flat plate collector. In addition to its economic viability, the modified flat plate collector could result in a CO2 savings of 901.85 kgCO2 per year. The study concludes with a sensitivity analysis to identify the market conditions that maximize the profitability of the modified flat plate collector based solar domestic hot water system.

Towards maximum cost-effectiveness: multi-objective design optimisation of insulating glass flat-plate collectors

A significant challenge in the advancement of solar thermal heating systems lies in the unexplored techno-economic potential of insulating glass flat-plate collectors. These collectors are constructed in accordance with the specifications of standard insulating glass units and have emerged over the past decade as a promising design concept for enhancing the cost-effectiveness of solar thermal systems. However, substantial findings regarding the techno-economic viability of their production are still pending. The aim of this paper is to optimise insulating glass collector designs for solar district heating applications by identifying key design parameters that maximise cost-effectiveness. This study employed a five-stage methodology. It included thermo-hydraulic collector modelling using MATLAB/Simscape and the CARNOT Toolbox. The model was validated against experimental performance tests. A Latin hypercube computational design with 250,000 samples was set up to train supervised machine learning metamodels and perform a multi-objective optimisation using an elitist genetic algorithm. The study identified the argon concentration, collector length, and width as critical parameters influencing efficiency. Larger, thinner collectors demonstrated superior performance due to reduced convective losses and increased aperture-to-surface ratios. The optimisation revealed that the insulating glass collectors could achieve a 7.7 percentage point increase in efficiency, a 19.4 % reduction in material cost, and a 14.5 % decrease in weight compared to market-available flat-plate collectors. However, the direct economic comparison was not considered strong in evidence due to a lack of economic data from technology providers. The most cost-effective designs featured an argon concentration of 99 %, sealing thickness of 31.2 mm, and a glazing thickness of 4.1 mm, and 4.5 mm, while collector length and width varied more significantly. The research findings indicate the techno-economic potential of insulating glass collectors, demonstrating their ability to outperform conventional flat-plate collectors in terms of cost-effectiveness and efficiency. Future studies should focus on producing and testing larger modules and incorporating production costs to fully realise their potential for solar district heating applications. This study provides valuable guidelines for IGU designers and producers aiming to develop cost-effective and efficient solar thermal collectors for district heating systems.

Comparative energy, exergy and entropy generation study of a minichannel and a conventional solar flat plat collectors

Considering the importance of using renewable energies for human societies, it is necessary to optimize the devices used. Flat plate solar collectors play a prominent role in the domestic and industrial sectors, so it is very important to enhance their performance. Changing the structure of the collector and using minichannel flat plate collectors (MFPCs) instead of sheet and tubes conventional flat plate collectors (CFPCs) is one choice. This study examines and compares the performances of a MFPC and a CFPC based on the energy, exergy and entropy generation perspectives. The working fluid is water and the fluid flow is laminar. Both collectors have the same contact surface between the working fluid and the inner surface of the riser tubes or the minichannels. In order to solve the equations, a thermal model is developed and the engineering equation solver is used. The results show that for all of the investigated conditions, the thermal and exergy efficiencies of the MFPC are higher than those of the CFPC and the maximum energy and exergy superiorities of the MFPC are 13.8 and 14.08 %, respectively. The study of the energy performance criteria shows that the MFPC is more suitable at lower volumetric flow rates and higher inlet fluid temperatures. Investigating the entropy generation and exergy destruction indicates that for every similar case the entropy generation and exergy destruction of the MFPC are lower than those of the CFPC. These interpretations, which are based on the energy, exergy, entropy generation and exergy destruction evaluations, recommend utilization of MFPCs instead of CFPCs.

Data-driven optimal placement of minichannel-based solar water heater using satellite-derived and ground-telemetry weather information

The aluminum minichannel solar collector is a novel technology for solar water heating. Minichannel-based solar collectors have higher thermal efficiency than conventional flat plate collectors and do not suffer from potential loss of vacuum as evacuated-tube collectors. This technology can play a significant role in reducing natural gas consumption that translates into lower greenhouse gas emissions to the atmosphere. However, the performance of solar collectors depends on the geographical location of the installation due to solar resource availability and weather pattern. The potential reduction in natural gas consumption using aluminum minichannel solar collectors is assessed using solar irradiance, ambient temperature, and wind data obtained from ground weather station and satellite-derived data. A data-driven numerical analysis is performed using a validated solar water heater (SWH) model, population, and natural gas consumption data for the entire state of California to assess the best locations to install these systems. The SWH model is validated based on data collected from an actual SWH system installed at a single-family house in Northridge, California. A K-means clustering method is then applied to select the best regions for installation of this technology. Based on performance, population density, and natural gas consumption, the regions of Southern California and the Central Valley are chosen as having the highest potential for reduction of natural gas consumption. The analysis was performed from weather data obtained based on two full years (2020 and 2022), where the effect of COVID-19 (year 2020) is observed as having higher water tank temperatures and higher solar fractions, which could be associated with lower hot water consumption.

Performance enhancement of indirect solar dryer with offset strip fins: Experimental investigation and comparative analysis

In the present study, two indirect type solar dryers were designed, fabricated and experimentally investigated, one is equipped with a conventional flat plate collector, and the other is integrated with offset strip fins (OSF). The objective is to study the effect of OSF on the performance of the dryer. A series of experimental tests were conducted at the applied research unit in the semi-arid region of Ghardaia using locally available materials. The first test was starting the solar dryers with an empty chamber and the second with filled product. The peak and average temperature difference at the outlet of the collector were 11.3 and 8 °C respectively, in favor of OSF absorber. The courgette was dried to 0.69 (kg water/kg dry basis) from an initial moisture content of 26.24 (kg water/kg dry basis) in 20 h 18 min and 35 h 45 min in the solar dryer with OSF and without, respectively. The results show a high drying rate using the dryer with OSF compared the dryer with conventional collector. Also, Midilli-Kucuk model provided the best agreements between experimental and predicted moisture ratios. Average effective moisture diffusivity of 1.798x10−09 and 1.179x10−09 m2/s for the dryer with OSF and without, respectively. A 33 % increase in economic efficiency in favor the OSF dryer with 0.95 years payback period. Also, a reduced amount of GHGs makes the dryers environmental friendly.

Thermal Analysis of Novel Pebble Absorber Based Solar Thermal Collector

The fluid flow rate of the heat absorbing medium plays a crucial role in the performance of the collector. Studies were carried out with varying fluid flow rates of 0.01 kg/s, 0.013 kg/sec and 0.016 kg/sec respectively for different days from 8:00 hour to 18:00 hour. The input parameters considered for the computational modeling are i) Solar radiation (I) ii) Ambient temperature (Ta) iii) Inlet water temperature (Ti) and iv) Mass flow rate (mf). Experiments carried out using coated and uncoated pebbles as absorber along with a conventional flat plate collector. The efficiency of the solar thermal collector increases with flow rate and incident radiation. The coated pebble absorber collector is more efficient than the uncoated pebble absorber collector and less efficient than the conventional metal absorber collector at above mentioned flow rates. The total average efficiency of coated absorber collector was 67.036%, 51.35% for the uncoated absorber collector and 72.857% for the conventional copper absorber collector.

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.

Performance analysis of solar drying system with sunlight transparent thermally insulating aerogels

Solar drying can solve the problems of product quality caused by open sun drying and high energy consumption caused by conventional energy drying. However, due to the low solar heat collection efficiency of conventional flat-plate solar collectors, the maximum drying temperature of the existing solar drying system is typically <70 °C, making them difficult to be used in cold regions. Herein, we proposed a new solar drying system with high solar heat collection efficiency, high hot air outlet temperature, and high drying efficiency based on silica aerogels that are transparent to sunlight and have ultra-low thermal conductivity. The results show that the optimum thickness of the silica aerogel insulation layer is 10 mm. At ambient temperatures of −10 to 30 °C, the air outlet temperatures of the designed solar collector are 52–97 °C, increasing the air outlet temperature by 23 °C and 28 °C, respectively, compared to conventional solar collectors. The proposed solar drying system incorporating a 10-mm-thick silica aerogel insulation layer can meet the drying requirements of most agricultural products without an additional heat source and shorten the drying time by 58%.

A novel design for solar collector used for water heating application having nanofluid as working medium: CFD modeling and simulation.

A solar collector is a simple and cheap device that converts solar radiation into valuable heat energy. The thermal performance of the solar collectors can be enhanced significantly with the suspension of nanoparticles in the base fluid. A novel design for a solar-assisted water heater (SWH) is proposed in the current study, and the effect of nanofluid has been investigated on the thermal efficiency of the SWH. The use of nanofluid is one of the prominent methods in comparison to other techniques for improving the performance of solar collectors. Therefore, the base working fluid, i.e., water is mixed with the alumina nanoparticles of average particle size of 30nm, and they are assumed to be spherical. The flow and thermal characteristics of nanofluid through the solar water heater are simulated numerically with the help of the Eulerian-Eulerian two-phase model using the finite volume method (FVM). The commercial package ANSYS Fluent, is used for modeling the problem under transient conditions with a pressure-based solver. In comparison to a conventional flat plate collector, the proposed solar water heater consists of a corrugated absorber-plate and the effect of the radius of curvature has been investigated on the heat transfer and collector efficiency. With the proposed design, the heat transfer area available with the riser tubes increases remarkably and it leads to a 43% and 14% increase in heat transfer augmentation and collector efficiency, in comparison to the conventional solar water heater.

Experimental characterization of a small-scale solar Organic Rankine Cycle (ORC) based unit for domestic microcogeneration

The integration of a Micro-Organic Rankine Cycle (ORC) power unit with conventional solar flat plate collectors ensures the simultaneous fulfillment of electricity and domestic hot water (DHW) demands. Due to the variability of the solar source, despite the introduction of a thermal storage unit, the plant is subject to severe off design operating conditions. A small-scale ORC-based was designed, built and fully tested, to experimentally assess the performance and operating robustness of the plant in steady and dynamic off-design condition. The unit is fed by hot water from a 135 L reservoir. Dedicated electric heaters (12 kW each one) reproduce the thermal availability from 15 m2 of standard solar thermal collectors for domestic applications. The test bench underwent an extensive experimental assessment in both stationary conditions of the hot source and in presence of a variable thermal load at the evaporator. Due to the plant architecture and components, the control of the unit is based on the variation of the mass flow rate of the working fluid (R245fa) matching the thermal equilibrium at the evaporator in each operating condition of the system. The variation of the flow rate, in fact, must fit with thermal power available. The off-design steady state assessment allows the understanding of the wide operability of the plant (17–62 g/s), with power and efficiency varying between 150 and 500 W and 2.4–4%, respectively. The dynamic testing of the pilot unit points out the plant consistency and robustness to severe off-design operation, mostly due to the 1 kW scroll expander, very suitable for time-varying operating conditions. Both the option of a full discharge of the thermal energy of the reservoir and the option of a split discharge to the evaporator were investigated and provided a clear indication on the CHP feasibility when no addition of thermal energy takes place at the reservoir. It was observed that during a complete reservoir thermal discharge, the plant works for 3000–3300 s continuously, with a slow power decrease from 500 W to 100 W. Considering the thermal energy recharging time, the plant could be averagely operated up to 7 times during the day if a partial discharge was performed. Each plant activation lasts 900 s producing a power ranging from 500 W to 200 W. This operating strategy allows to cover up to 11.2% of the whole electric energy yearly required by an average European household.

Effect of magnetic field on the thermal performance of a ferrofluid‐based solar flat plate collector

AbstractIn this paper, the effectiveness of ferrofluid as a working fluid for solar flat plate collectors (FPCs) is studied. A mini‐ferrofluid‐based solar FPC is designed and tested under laboratory conditions. The thermal performance of the designed solar FPC is evaluated under different conditions and it is observed that it provides higher efficiency for the case of ferrofluid in the presence of a magnetic field. The thermal efficiency is observed to increase by 54% for ferrofluid in presence of a magnetic field as compared to no magnetic field. The thermal efficiency is observed to increase further with the increase in the magnetic field. The increase in thermal efficiency is attributed to the combined effects of higher thermal conductivity and magnetohydrodynamics of ferrofluid, which result in higher convective heat transfer from the riser tube walls into ferrofluid. The higher heat transfer for ferrofluid with a magnetic field is established by calculating the Nusselt number numerically using COMSOL. Simulation results show an increase in Nusselt number for ferrofluid with magnetic field and hence higher thermal efficiency for the solar FPC. The designed FPC provides simple modifications to conventional FPCs to use ferrofluid with magnetic field for higher thermal efficiencies.

Utilization of biodegradable novel insulating materials for developing indigenous solar water heater for hill climates

Conventional flat plate collector based solar water heating systems use glass or ceramic wool as insulating materials to minimize the heat losses. The utilization of these inorganic insulating materials, is associated with risk in the industrial workplace activities, manufacturing, and installation depending on the exposure to the material. Thus, it is important to use and develop biodegradable organic insulating materials which are easily available, low cost and environment friendly. This study presents the design and fabrication of a flat plate collector solar water heating system using biodegradable forest and agriculture wastes as insulating material. The utilization of pine needles and rice husk as thermal insulation for the fabrication of solar water heaters is the novelty of the study. The innovative solar water heater is tested under different outdoor climatic conditions. Maximum hot water temperatures between 52 °C and 55 °C were observed with an average efficiency of 52% and 57% with rice husk and pine needles as insulating materials respectively. Experimental analysis is performed using 40 mm, 60 mm and 80 mm pine needle insulation. The optimum pine needles insulation thickness is found to be 60 mm with a maximum hot water temperature of 64 °C for the indigenously developed flat plate collector based solar water heater for hill climates. Follow-up research areas are also identified.

An Experimental Study on the Performance of a Hybrid Photovoltaic/Thermal Solar System

Considered as the widespread renewable energy, solar energy is used to produce the electricity and heat for carbon peaking and carbon neutralization. However, the photo-electric conversion efficiency will decrease with the increase of cells temperature. To solve this problem, a water-type hybrid photovoltaic/thermal (PV/T) solar system has been designed and tested in Hong Kong. The outdoor experiment proceeded all days in 6 months with three different operating modes. The data of selected 33 days were used to analyze the performance of the system. The results showed that the thermal efficiencies were 33.6%, 52%, and 48.3% at zero reduced temperature, corresponding to three modes. Besides, the overall efficiencies were 43.2%, 60.9%, and 55.2% accordingly, which are higher than those of the conventional flat-plate solar collector. The average water temperature in the storage tank could reach 39.9°C, and the system could produce 0.07 kWh electric power after one-day operation, when the collector with 96 kg/m2 M/Ac installed vertically combining with external wall for each family. It is realizable to utilize the developed building integrated water-type photovoltaic/thermal (BIPVT) solar system for residentialintensive high-rise buildings in Hong Kong, satisfying the needs of hot water, and eventually reducing energy consumption of the buildings.

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.

Comparison Performance of Conventional Drying Methods and Flat Plate Collector Solar Dryer

As another to the marketing of fresh fruits and vegetables, small farmers can think of conservation by drying. In the conservation of agricultural crops, wastewater treatment, and biomass treatment, drying is an important process. Energy requirements for drying can be supplied from different sources, such as fossil fuel, natural gas , electricity, wood, remaining bark forests, and solar energy. Although the use of solar radiation has existed for drying since a long time ago, it has not yet been widely commercialised, particularly in the agricultural sector.

Modified Hottel-Whillier-Bliss Equation for an Active Solar Distillation System for Higher Yield and Thermal Efficiency

Abstract Based on energy-balance equations for a photo-voltaic thermal (PVT) active solar distillation system, a modified Hottel-Whillier-Bliss (HWB) analytical characteristic equation as a function of design and climatic parameters has been derived in the present article. It has been found that there is a significant difference between characteristic equations for PVT-based active solar distillation and the conventional flat plate collector (FPC). It is due to (i) opposite nature of loss factor from inside surface to ambient through glass cover and (ii) temperature dependence of the evaporative heat transfer coefficient between water surface and condensing cover in the solar distillation system. Numerical computations have been obtained for the characteristic curve of the proposed active solar distillation system and flat plate collector under the condition of a typical day in New Delhi, India. Further, the effect of performance parameters such as packing factor, electrical efficiency of individual PVT collectors, and water mass have also been studied for the proposed active PVT solar distillation system. Moreover, daily yield of portable water has been found to be 7.34 kg/m2 at n = 5 and βc = 0.25 which is 100.5% higher than the daily yield of 3.66 kg/m2 obtained at n = 1, βc. = 0.89.

Modeling and analysis of a solar minichannel flat plate collector system and optimization of operating conditions using particle swarms

Solar minichannel flat plate collector (MFPC) has shown appreciable results in the recent past. Compared to the conventional flat plate collector (CFPC), MFPC is simple in construction and provides better output. However, optimization studies on MFPC have not been well attended. In this paper, a simulation of MFPC is carried out using a novel mathematical model. The objectives of this study are to validate the mathematical model using experimental results; identify the major factors that highly influence the collector performance, and optimize the performance using an evolutionary algorithm. Collector performance, namely collector efficiency and water outlet temperature are bound to be affected by many factors like solar irradiation, water inlet temperature, mass flow rate, and channel width. A new technique of simulating MFPC is demonstrated for which equations are developed based on the energy balance principle and fin analysis at steady state. The model is validated by corroborating with experimental results. When compared with CFPC, MFPC is 10–12% more efficient. A design of experiments is used to determine the set of trials followed by MANOVA and regression analyses. Multi-objective particle swarm optimization (MOPSO) is adopted to maximize the collector performance. Regression equations for collector efficiency and water outlet temperatures serve as objective functions. The results revealed that solar radiation, water inlet temperature, flow rate, and channel width are highly significant factors. From the MOPSO analysis, a mass flow rate ranging between 0.01 and 0.015 kg/s is found to be optimal for the MFPC system.

Approximate Representation and Exposition of ISI Flat Plate Collector including Revised Flat Plate Collector : A Review

Cosmic power is one of the numerous renewable energy sources that can use in a Photovoltaic (PV) system or Thermal. Solar collectors play a crucial role in solar thermal systems. They convert solar radiation into heat and transfer the heat to working fluids Such as water or air. The Flat-plate collectors are the numerous common type of solar collectors and typically used as a water heater or air heater. These collectors have low efficiency and low outlet temperature. Recently, many scientists have attempted to improve the efficiency and performance of flat-plate collectors via different methods. This review paper describes the results of the experimentation carried out to study and compare the performance of the modified flat plate collector having increasing riser tube diameter and reducing riser tube length with the conventional ISI marked solar liquid flat plate collector. To study, the comparative performance characteristics of a modified flat plate collector with ISI flat plate collector operated under natural circulation mode. The suggested design found to be better than the existing ISI design of the absorber plate from an efficiency point of view. The actual useful heat gain (Qu) in the suggested design understudy found to be more by 30% than that in the case of ISI collector. However, the modified flat plate collector found to operate at a relatively lower exit temperature than the conventional ISI marked collector.

Active Heating of Outdoor Swimming Pool Water Using Different Solar Collector Systems

Abstract In this communication, a theoretical thermal model has been developed by using basic energy balance equation for outdoor swimming pool in terms of design and climatic parameters. An analytical expression for swimming pool water temperature has been obtained to optimize the design parameters to get an optimum temperature of swimming pool by using solar energy. For general analysis, an integration of photo-voltaic thermal (PVT)-compound parabolic concentrator (CPC) collectors with swimming pool water has been proposed along with special cases, namely, (i) evacuated tube collectors, (ii) conventional flat plate collectors (FPCs), (iii) CPC–FPCs, and (iv) PVT flat plate collectors. Numerical computations have been carried out for cold climatic condition of Srinagar, India. The effect of sensitive parameters on thermal and electrical performance of swimming pool has also been carried out.

“Performance comparison of innovative spiral shaped solar collector design with conventional flat plate solar collector”

Flat plate solar collector is an essential device, which facilitate direct application of solar energy for water heating in household and industrial sector. Existing Flat plate solar collectors (FPSC) suffers from stagnant and comparatively low efficiency. Further research to improve efficiency of FPSC by inculcating innovative design is necessary. To fill the gap, the presented work is an experimental investigation of an innovative design and fabrication approach which deals with analysis of flat plate solar collector efficiency. Design modifications of solar collector always offer an important alternative to achieve significant effect on thermal efficiency. In this work single spiral shaped collector tube as compare to number of riser tubes connected with headers in conventional type flat plate solar collector has been developed. Keeping all other parameters similar to conventional design, it has been observed very encouraging outcomes in efficiencies of solar collector. Under forced mode of testing, enhancement in thermal efficiency achieved is, 21.94% compared to conventional flat plate collector design. Enhancement in exergy efficiency is 6.73%. Overall material saving is about ∼30% and cost of manufacturing and maintenance can be significantly reduced at equivalent performance of conventional collector.