Thermal Efficiency Of Solar Collector Research Articles

Solar Collectors with Nanofluid for Domestic Applications: A Review

Energy management and the usage of renewable energy sources are essential for a sustainable future. This paper carried out a review and summarize the recent topic of solar collectors heating water for use in a domestic application. Several researchers have studied solar collectors with flat plates, evacuated, and concentrators to improve heat gain for heating water. Entropy is an important function that the attention of investigators to reduce and increase the thermal efficiency of solar collectors. Nanofluid has been selected as have found a new class of thermal efficiency enhancement for this purpose. Thermal performance is enhanced by changing the geometry of the absorber plate of the solar collector and the evacuated tube is the best. It was found that increasing nanoparticle concentration to 4% improves solar collector efficiency to 30%. It was observed that the report of solar-collector enhancement by changing geometry and fluid flow through the solar-collector.

Analysis of parabolic trough solar collector thermal efficiency with application of a graphene oxide nanosheet‐based nanofluid

AbstractNowadays, clean energy production and reconciliation with nature is one of the best solutions known to rectify the global warming issue. Solar energy, as a clean and green one, has recently been drawing scientists' attention to itself more than ever. Applying parabolic trough solar collectors (PTSCs) is one of the state‐of‐the‐art ways to extract energy from the sun. As one of the most interesting research topics, the thermal efficiency enhancement of PTSCs is studied. The current study demonstrates how the thermal efficiency of PTSCs is enhanced through the application of graphene oxide (GO) nanosheets, as an inexpensive nanomaterial with superb thermal conductivity and unique structure, in thermal oil, namely, Behran oil, as heat transfer fluid, within the effective volume fraction range of 0.05. The above‐mentioned analysis is based on the theoretical calculations performed through a mathematical model based on the Taylor series approximation. All the calculations are performed with respect to a PTSC unit of a solar–thermal power plant situated in Shiraz, Iran, as the research case study. In addition, the Nan et al. model is used to analytically predict how the increase in the volume fraction of GO nanosheets raises the thermal conductivity and consequently increases the convection heat transfer coefficient of the nanofluid, leading to the thermal efficiency enhancement of PTSCs. The results reveal a maximum thermal efficiency of 71.10% for the volume fraction of 0.05. In comparison to the thermal efficiency of the real‐world case‐study mentioned above with pure thermal oil, that is, 67.71%, the thermal efficiency enhancement by about 5.5%, is achieved. Moreover, it is discussed how the thermal efficiency achieved from GO nanosheets surpasses the ones obtained from the application of particle shape nanomaterials, or carbon nanotubes in the same conditions.

A comprehensive review of the influence of nanomaterials on the thermal performance of a solar thermal collectors

The present review article investigates the utilisation of nanomaterials with the aim of augmenting the thermal efficiency of solar thermal collectors (STCs). A comprehensive analysis is conducted on the STC through the utilisation of nanomaterials, leading to an improvement in its performance. This evaluation highlights the similarities in the results through an in-depth discussion on several types of criteria that might impact the performance of STCs. In order to justify and, finally, explain the behaviour of nanomaterials for the purpose of thermal augmentation of STCs, analysis was carried out and is being discussed here. This review article presents a novel aspect that is based on an extensive investigation that was based on a significant amount of research that had been published in the past. The study indicated that the use of nanomaterials may boost the heat-absorbing ability of the STCs.

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.

Experimental and numerical investigation of parabolic trough solar collector thermal efficiency enhanced by graphene–Fe3O4/water hybrid nanofluid

This experimental study discusses and focuses on the working fluid because it is regarded as the most important factor influencing parabolic trough solar collector (PTSC) performance. To study the performance, two identical PTSCs were manufactured to use water and the graphene (G)–Fe3O4/water hybrid nanofluid (HNF) as working fluids with different concentrations. The two collectors were evaluated under the same conditions and based on experimental results that the average thermal efficiency and deviation between them not exceeding 0.11%. In addition, the HNF was prepared, and the effect of volume concentration and temperature on the viscosity and thermal conductivity of G–Fe3O4/water was studied. Test samples consisting of HNFs with volume concentrations of 0.01%, 0.05%, 0.1% and 0.2% were compared with water at a mass flow rate of 2 L/min. According to the results, the TE of the PTSC was improved by using a G–Fe3O4/water HNF. The thermal efficiency for G–Fe3O4 HNF was obtained for 0.2%, 0.1%, 0.05% and 0.01% VCs and reached 45.46%, 44.3%, 42.04% and 41.02%, respectively, while the collector efficiency with water was 40.41%. A numerical analysis of the performance of PTSC was also performed using ANSYS Fluent. The results obtained from the numerical and experimental work were in good agreement.

Modeling and comparative assessment of solar thermal systems for space and water heating: Liquid water versus air-based systems

This work pertains to the transient modeling and comparative study of active solar thermal space and water heating systems using liquid and air-type solar thermal collectors as the main energy source. The study utilizes TRNSYS to simulate the two systems in the context of Taxila's weather data (located at 33.74°N, 72.83°E), with the goal of meeting peak space and domestic water heating demands of 20 kW and 200 lit/day, respectively. The liquid water-based system (S-1) is primarily composed of a liquid solar collector, thermal storage, an auxiliary heater, connections to the hot water supply, and the space heating load through a water–air heat exchanger. In contrast, the air-based system (S-2), employs a pebble bed storage to store heat extracted from the solar thermal air collector. The heated air is subsequently used directly for space heating and passed through an air–water heat exchanger for water heating. Dynamic simulations of both systems span the entire winter season, and various performance metrics, including solar fraction, primary energy savings, and solar collector thermal efficiency, are computed. The results revealed that at the same collector area, the liquid water-based system (S-1) shows a higher solar fraction than the air-based systems (S-2) while the primary energy savings of the S-1 resulted in lower values than S-2 at smaller collector areas (< ∼30 m2) but surpasses the S-2 with increasing collector size. The optimal collector tilt for both systems is determined to be 50°, while specific storage volumes corresponding to maximum primary energy savings are estimated to be 100 and 40 L/m2 for S-1 and S-2, respectively.

Enhancing solar thermal collector systems for hot water production through machine learning-driven multi-objective optimization with phase change material (PCM)

Energy storage and supply in solar thermal collector systems rely heavily on phase change materials (PCM). It is vital to establish the appropriate values for energy discharge time (tPCM) and net amount of stored energy (Qnet) within the PCMs in order to increase the efficiency of solar thermal collectors. For this study, we implemented a multi-objective evolutionary algorithm based on decomposition (MOEA/D) for the optimization process using the MATLAB simulator software. The simulation findings show that, under ideal circumstances where tPCM is large and Qnet is low, these two goal functions are inversely connected to one another. According to an analysis of how input parameters affect the objective functions, the mass of PCM is minimized and the mass flow rate of the input water is increased under ideal circumstances. The relationship between the tube's inner diameter and the tPCM objective function shows that an increase in the tube's diameter corresponds to an increase in the energy discharge time. The amount of stored energy in the PCM increases when the system parameters are held constant while the tube diameter is increased. Additionally, we investigated the effects of several solid PCM materials on the discharge time and the energy stored.

Experimental Investigation of Parabolic Trough Solar Collector Thermal Efficiency Enhanced by Different Reflective Materials

Experimental Investigation of Parabolic Trough Solar Collector Thermal Efficiency Enhanced by Different Reflective Materials

Experimental investigation of parabolic trough solar collector thermal efficiency enhanced with different absorber coatings

The objective of this work is to investigate the thermal efficiency of a compound parabolic trough solar collector (PTSC) by using different absorber tube coatings. Two identical PTSCs were used to compare the different absorber coatings: one with matte coating (MC) and the other with nanocoating (NC) by adding Fe3O4 and graphene nanoparticles to the MC. In the beginning, similarity tests of the two collectors were carried out using the matte coating of the absorber tube under the same conditions and a mass flow rate of 120 L/h. The test results show the average thermal efficiency of collectors did not reach 0.11%. Then, the PTSC was compared with various mass flow rates: 30, 60, 90, and 120 L/h. The results show the maximum heat removal factor of PTSC for both nanocoating and matte acrylic coating at 120 L/h was 52.72% and 50.33%, respectively. And the maximum thermal efficiency of PTSC for both nanocoating and matte acrylic coating at 120 L/h was 41.58% and 40.37%, respectively. Finally, adding iron oxide and graphene nanoparticles to the matte acrylic coating has increased the amount of radiation absorption. As a result, PTSC's optical and thermal efficiency improved.

Optimizing the efficiency of solar thermal collectors and studying the effect of particle concentration and stability using nanofluidic analysis

The emission of greenhouse gases is widely acknowledged as the primary driver of global warming. The adoption of renewable energy sources is paramount to address the dependence on fossil fuels, which contribute significantly to this issue and account for 84.3% of current energy production. Solar thermal energy stands out as a prominent option, representing 54.1% of the world's solar energy derived from solar collectors. However, solar thermal energy encounters challenge due to the suboptimal thermal properties of the liquids used in these collectors. Incorporating particles into the liquids offers a potential solution to enhance absorption and thermal properties. Nanofluids, formed by reducing solid particles to nanoscale dimensions, provide an avenue for improvement. This study aimed to produce an Ag nanofluid through mechanical exfoliation and assess its impact on radiation absorption compared to a GO nanofluid. Under a simulated power of 1 unit, the Ag nanofluid demonstrated temperature differences of 4 to 7°C, while pure water showed no significant deviation. Moreover, the evaporation efficiency of the Ag nanofluid reached up to 40.8% for concentrations of 200 and 500 ppm, compared to 28.6% for pure water. These findings highlight the potential of Ag nanofluid as a promising option for direct absorption solar collectors, owing to its cost-effectiveness, low toxicity, and similar benefits to graphene. Incorporating nanofluids, particularly the Ag nanofluid produced through mechanical exfoliation, can significantly enhance the efficiency of direct absorption solar collectors.

Experimental investigation of improved parabolic trough solar collector thermal efficiency using novel receiver geometry design

Experimental investigation of improved parabolic trough solar collector thermal efficiency using novel receiver geometry design

Investigation of tungsten halogen lamp for possible usage as heat source for testing solar collector

Artificial sunlight is a heat source in solar collector testing, where the light intensity and ambient conditions are controlled to provide uniformity in each test. In this study, twenty-five tungsten halogen lamps of 300 W 220 V were investigated for possible usage as the heat source. The experiment was conducted by varying the height of the lamps to the light field (Hd). The EN-12975–2 Standard was used to control the quality of the heat source on the light field. The results showed that the average light intensity (Iavg) decreased with an increase in Hd. When Hd was low, the %uniformity values (%uxy) met the criteria. The small light field area met the EN-12975–2 Standard better than the large area. A comparison of solar collector testing under a heat source from tungsten halogen lamps and natural sunlight was subsequently performed, and the experimental results were in accordance with the EN-12975–2 Standard. A single-channel flat plate solar collector was used as the test device and air was used as the working fluid. The experimental results revealed that the solar collector thermal efficiency (ηavg) trends were similar for both the heat source from tungsten halogen lamps and natural sunlight testing. A low %uxy resulted in a ηavg that was more similar to that of natural sunlight.

Analysis of Mixed Convection and Free Convection in a Reduced Solar Collector Using a Nanofluid as Heat Transfer Fluid

A three-dimensional investigation of mixed convection which occurs from Al2O3-water nanofluid flow in tube of a reduced solar collector and free convection in air gap situated between cover of solar collector and its absorber was investigated. Heat transmission by conduction in absorber and cover as well as thermal losses to exterior expressed in form of a convective flux have also been taken into account. The different transport equations were solved using CFD-Fluent software which is founded on finite volume method and Boussinesq’s law was introduced to take into account of buoyancy effects. In this investigation, thermal efficiency of solar collector was evaluated and use of nanofluids allows to increase this parameter which is generally low for this kind of thermal systems. Length of thermal regime established in the tube is proposed and this investigation is extended relative to other works developed in this research field. Results obtained gave an idea about the flow structure of the fluid under consideration in a tube of a solar collector and heat transmission mechanisms in air gap and in other elements of the solar collector. These results can facilitate design of this thermal system.

The impact of the V-corrugation on the thermal efficiency of a solar collector

Solar energy plays an essential role in the process of the energy transition to renewable sources, and so too do technological innovations for exploring these energy sources, and for improving the thermal efficiency of conventional flat solar collectors. This study set out to model, simulate, and investigate the effect of modifying the geometry of the absorber plate of standard solar collectors for heating liquids, by inserting V corrugations. This leads to making consequent modifications to geometrical and optical parameters that improve the efficiency of the equipment. This paper presents the application of a mathematical-graphical model that seeks an optimum incidence angle to corrugate an absorber plate. This model, based on available optical experimental data, was built to improve the efficiency of solar collectors. During its application, an investigation could be made of the effect of the corrugation on the radiation and on the convection coefficients, the correlations of which were introduced into the mathematical model, and some of them were neither mentioned nor used in previous publications. A case study was carried out to investigate the behavior of three different collectors and the improvement in the efficiency of these collectors. It was shown that by using V grooves the efficiency was improved for all three flat solar collectors studied. As seen, the geometric modification contributes to improving efficiency when associated with selective absorption layers of solar collectors. The combination of both strategies can enhance the thermal efficiency of solar collectors and this can be further explored by researchers and manufacturers.

Improve the performance of solar thermal collectors by varying the concentration and nanoparticles diameter of silicon dioxide

Abstract The influence of different concentrations and nanoparticles’ diameter of silicon dioxide nanoparticles on the Nusselt number enhancement ratio and friction factor for solar thermal collector (STC) was examined numerically. The CFD model was designed to show the influence of the flow of water/SiO2 and pure water inside the pipe on the enhancement of the performance of the STC. Different concentrations of SiO2 nanoparticles are used (ϕ = 1–4%) with several nanoparticle diameters (dp = 20–50 nm). The water/SiO2 and pure water flow under different Reynolds numbers ranging from 5,000 to 30,000. The average Nusselt numbers Nuavg improved by increasing the Reynolds numbers for both fluids. The Nuavg increases with the increase in the concentration of SiO2 nanoparticles. The water/SiO2 with nanoparticle concentration of (ϕ = 5%) and nanoparticle diameter of (dp = 20 nm) has the highest Nusselt number. The Nuavg enhances 25% with water/SiO2 nanofluid flow at Re = 5,000 and 15% flow at Re = 30,000. It is noted that the skin friction factor decreases with the increase in the Reynolds number for both fluids. Water/SiO2 nanofluid has a higher skin friction factor than pure water. The Nuavg improved by 31% at the lowest Reynolds number by using water/SiO2 nanofluid as the working fluid with a change in the concentration of SiO2 nanoparticles from (ϕ = 1%) to (ϕ = 4%) and improved by 42% at the highest Reynolds number of 30,000. The decrease in the nanoparticle diameter led to an increase in the Nusselt number across all Reynolds numbers. The lowest size SiO2 nanoparticles (dp = 20 nm) provides the highest Nusselt number. The lowest size SiO2 nanoparticles (dp = 20 nm) provide the highest ratio of enhancement for the Nusselt number in STC. This investigation has confirmed that the flow of water/SiO2 with AL2O3 nanoparticles of 5% (diameter of 20 nm) has a significant influence on heat transfer enhancement to improve the thermal efficiency of STC.

Experimental Analysis of Air Inlet Height Variation in a Solar Tower system Using Plate and Metal Foam Absorber

The experimental analysis is conducted under the Iraqi climate conditions to investigate the performance enhancement of a solar updraft tower system (SUTS) using the porous copper foam as an absorber plate and conventional absorber plate with absorber inclination angle of 18°. In the present work, a semicircular collector is divided into two identical quarter thermal collectors to become two identical SUTS. One of the quarter circular thermal collectors contains on the metal foam as an absorber plate, while the other quarter collector on the conventional flat copper absorber plate. In this study the air inlet height is changed of (3, 5, and 8) cm. The experimental tests carried out in Baghdad city (latitude 33.3° N). Results showed that the air inlet height variation caused to enhance the solar updraft tower performance. The highest values was recorded when the air inlet height is 3 cm using porous absorber compared to flat absorber plate. Copper material foam as an endothermic surface causes a marked decrease in average surface temperature of the plate. The maximum hourly thermal efficiency of solar collector was increased to about 41.6 % and the maximum enhancement of the power output to about 45.2 % compared with flat absorber plate.

4E study of experimental thermal performance enhancement of flat plate solar collectors using MWCNT, Al2O3, and hybrid MWCNT/ Al2O3 nanofluids

Nanofluid is a cutting-edge heat transfer fluid with the potential to significantly improve the heat transfer performance of conventional fluids. The most valued aspects to increase the overall solar collector's effectiveness are to improve design factors and the convection heat transfer coefficient between the absorber tubes and fluid. Water nanofluids including MWCNTs, Al2O3, TiO2, SiO2, and CuO are the most often utilized nanofluids in solar collectors. In this paper, the Flat Plate Solar collector thermal efficiency was experimentally investigated for MWCNT, Al2O3, and hybrid MWCNT/Al2O3 50:50% as a working fluid, under controlled circumstances. The effects of several parameters, including solar radiation intensity, volume proportion of nanoparticles, and volumetric flow rate on the efficiency, are investigated. Four volume concentration percentages were studied for each type of nanofluid (0.5%, 0.025%, 0.01% and 0.005%) with three different mass flow rates for each concentration. The results show that using hybrid MWCNT/Al2O3 (50:50%) offers an increase in efficiency by 26%, 29%, and 18% for 1.5 L/m, 2.5 L/m, and 3.3 L/m, respectively, recommending the replacement of 50% of the MWCNTs by the more economic and environmentally friendly Al2O3.

Experimental investigation of a hybrid configuration of solar thermal collectors and desiccant indirect evaporative cooling system

This paper presents the integrated performance of a solar-assisted desiccant dehumidifier along with Maisotsenko cycle (M-cycle) counter flow heat and mass exchanger. This system handles latent load and sensible load separately. The hybrid configuration of solar thermal collectors was analyzed for efficiency of solar collectors and solar fraction. High consumption of fossil fuels, which are already present in a limited amount, is also associated with environmental problems and climate change issues, as these increase the chances of global warming. These issues demand of us to shift towards renewable energy resources. Increase in world energy use results in a number of environmental problems, such as climate change, in addition to global warming and ozone depletion. In building services, HVAC systems are major concerns. To overcome the requirement, conventional air conditioning and vapor compression systems are mainly used for air conditioning, although these also have some environmental problems. Solar thermal applications in combination with other renewable-energy-dependent cooling practices have generated a huge interest towards sustainable solutions, keeping in view several techno-economical, environmental, and climatic advantages. The experimental investigation reveals that the maximum outlet temperature and efficiency of solar thermal collectors was 87°C and 56% respectively. The maximum cooling capacity of the system is evaluated at 4.6 kW.

Experimental investigation of thermal efficiency and thermal performance improvement of compound parabolic collector utilizing SiO2/Ethylene glycol-water nanofluid.

A compound parabolic collector has been used in the present study to lower operating costs per unit of heat increase compared to other tracker concentrators. This type of collector has been given more attention in industrial and domestic applications in the temperature range of 60 to 300°C. Also, to increase the thermal efficiency, nanofluid containing SiO2 nanoparticles in ethylene glycol-water hybrid base fluid (10-90 vol.%) have been used in three different volumetric fractions. The innovation of this present study includes the utilization of mentioned nanofluids for the first time in this collector, which has good stability and is cost-effective compared to other nanoparticles. In addition, the experimental measurement of thermal and hydraulic properties of nanofluids represents new aspects of the present study. The experiments used three volumetric fractions of 0.5%, 1%, and 1.5% under extensive solar radiation. Thermal performance of the collector at four volumetric flow rates of 1, 1.5, 2, and 2.5 Lit/min have been investigated according to ASHRAE standard 93-2010 (RA2014). According to the experimental data, the thermal efficiency of the collector improved by 5% to 11.6% when the nanofluid was applied. The maximum enhancement of the average Nusselt number of the nanofluid versus the base fluid at the volumetric flow rate of 1 Lit/min and the volumetric fraction of 1.5% was equal to 7.3%. Besides, nanofluid increased the pressure drop, and consequently, the pumping power slightly. Finally, considering both the impacts of heat transfer and pressure drop, performance evaluation criteria and overall efficiency for nanofluid have been analyzed. The results represented that in all volumetric fractions, the values of performance evaluation criteria and overall efficiency enhanced compared to the base fluid. This research provides researchers and engineers with important information to better understand the thermal and hydraulic parameters of the parabolic compound concentrator in the presence of nanofluid to improve its thermal performance. The results also highlight the potential of using SiO2 nanoparticles to improve the thermal efficiency of solar collectors despite their low thermal conductivity compared to other conventional nanoparticles.

Analysis and CFD Modeling of Thermal Collectors with a Tracker System

Thermal solar systems are currently one of the most suitable ways to convert solar radiation into usable energy. To ensure maximum energy gain, it is necessary to correctly adjust the direction of the collectors in the southern direction. The deviation from the south is energy acceptable, but there are losses that reduce the overall efficiency of the system. A suitable tool for increasing the efficiency of solar thermal collectors is the usage of tracker systems which track the position of the Sun along the ecliptic orbit. The system is directed south towards the equator. It is important to know the effectiveness of the system in terms of assessment. For the monitored period of the equinox, the increase of the solar thermal gain of the system with rotation of the collectors represents 16.23%. One of the methods is to use simulation tools to simulate different conditions of solar energy flow. A model in the Ansys software was developed for solar thermal flat collectors. The model is based on setting the material parameters of the collector construction, the properties of the absorber in terms of absorption as well as the materials and its geometry, the properties of the heat transfer medium, and the setting of the volume flows. At the same time, it is possible to define the change in the energy flow of the incident radiation. The model is a useful tool for evaluating collectors used by different tracking systems. The model was experimentally verified on a tracker system and compared with experimental data with good agreement. For sunny days, the model shows an accuracy rate of 98.7% in the condition without rotation, and 99.1% in the condition with rotation of the collector. After including the 5% degree of uncertainty for the condition of the rotated collectors, the accuracy of the model is 94.2% and for the condition without rotation 93.8%.