Solar Collector Applications Research Articles

Heat transfer optimization of nonlinear mixed convection flow of nanoliquid past a vertical rotating cone with Stefan blowing using response surface method

Mixed convection heat flow is an imperative topic that has engrossed the consideration of numerous researchers for its applications in solar collectors, engine cooling by radiators, cooled nuclear reactors etc. In such applications, the linear form of the density deviation concerning temperature is insufficient since the thermal difference is substantially large. Hence the modified Boussinesq approximation is appropriate and noteworthy. Therefore, the non-linear mixed convective dynamics of the nanoliquid on a surface of a rotating cone subject to the Stefan blowing, Lorentz body force and thermal jump surface conditions are studied. The response surface method (RSM) is employed to simultaneously optimize the heat and mass transfer rates. The axial flow is significantly decelerated due to stronger Lorentz body force, while the thermal energy increases. RSM optimization procedure determined that the maximum Nusselt number (0.47408) and Sherwood number (1.20187) occurred for a low level of Brownian motion and the high level of Stefan blowing number and thermophoresis number. The Lorentz force improves the temperature field, consequently the Nusselt number reduces for stronger Lorentz force.

Thermo-optical performance of bare laser-synthesized TiN nanofluids for direct absorption solar collector applications

Thermo-optical performance of bare laser-synthesized TiN nanofluids for direct absorption solar collector applications

Thermal transport of mixed convective flow of carbon nanotubes with Fourier heat flux model: Prabhakar-time derivatives assessment

The thermal prospective of hybrid nanofluid is more impressive and presents many dynamical applications in solar collectors, thermal systems, machining, extrusion processes, nuclear cooling, heating and cooling devices, desalination. Owing to such motivations in mind, this research communicates thermal impact of carbon nanotubes due to inclined plate under the effect of a magnetic field. Both single-walled carbon nanotubes (SWCNTs) and multiple-walled carbon nanotubes (MWCNTs) are considered as nanoparticles to enhance the thermal mechanism of human blood and water base liquids. The mixed convection phenomenon for natural convective flow is considered. The most recent definition of fractional scheme namely Prabhakar derivatives is used to perform the theoretical outcomes. The integral of problem is supported with Laplace transform. The impact of dimensionless parameters on velocity and temperature profiles is studied and graphs are plotted by the mathematical software. The obtained results are compared numerically and graphically by using different inverse techniques known as Stehfest method and Tzou’s methods. It is observed that nanoparticles’ volume fraction boosted the thermal phenomenon more effectively for SWCNTs. The improved velocity profile due to interaction of buoyancy forces is observed.

Investigation on stable TiN plasmonic nanofluids for applications in direct absorption solar collectors

AbstractTiN nanoparticles based plasmonic nanofluids exhibit promising results in performance improvement of direct absorption solar collectors, but the main issue for practical application is their poor stability. In this work, ethylene glycol (EG) based TiN nanofluids with polyacrylic acid (PAA) stabilizing ligand were prepared. The optical properties of the TiN‐PAA/EG nanofluids with concentration ranging from 10 to 100 mg/L were characterized. The solar weighted absorption fraction of 99.55% is achieved at the optical depth of 1 cm when the concentration of the TiN‐PAA/EG nanofluids is 100 mg/L. In addition, the experimental results of the long‐term stability indicated that the TiN‐PAA/EG nanofluid retained excellent dispersion stability after ambient storage of 250 days. Then, the stability of TiN‐PAA/EG nanofluids upon prolonged heating cycle and accelerated ultraviolet (UV) irradiation was investigated. The results showed that TiN‐PAA/EG nanofluid with concentration of 75 mg/L presents superior thermal stability after prolonged heating cycles at 120°C and excellent photostability after 30 days of UV irradiation. Finally, the photo‐thermal conversion performance for TiN‐PAA/EG nanofluids was studied. The stagnation temperature of the 100 mg/L TiN‐PAA/EG nanofluids after light irradiation of 2 h reaches up to 80.12°C. The specific absorption rate of the prepared TiN‐PAA nanofluids is demonstrated higher than that of reported TiN nanofluids.

Nanofluid Based Pipe Flow Analysis in Absorber Pipe of Flat Plate Solar Collector: Effects of Inclination and Porosity

Nanofluid applications in solar collectors are an emerging area for enhanced heat transfer resulting in heat gain for domestic and industrial use. In the present work, the performance of a Flat Plate Solar Collector (FPSC) having water-CuO-based nanofluid has been studied. The effect of the tilting angle of cylindrical pipe and porosity of porous material is investigated for this nanofluid-based FPSC. A numerical approach has been adopted to stimulate the governing equations in the tube. The similarity transformation simplifies the model (PDEs) into ordinary differential equations (ODEs). The governing non-dimensional PDEs along with their appropriate boundary conditions are solved numerically using the 4th order Runge-Kutta method cum shooting technique. The impacts of significant and relevant physical parameters and physical quantities of interest are analyzed. From the present study, it is observed that amplification of tilting angle and curvature parameter ameliorates the heat transfer rate while that of porosity parameter controls it effectively. A similar approach can be employed for other solar collectors to assess the heat transfer augmentation by using nanofluids instead of existing fluids.

A hybrid deep learning - CFD approach for modeling nanoparticles’ sedimentation processes for possible application in clean energy systems

Sedimentation directly affects the thermal performance and efficiency of thermal systems such as boilers, heat exchangers, and solar collectors. This work investigates the effect of nanoparticles deposition inside a tube with possible application in parabolic solar collectors. This study combines the lattice Boltzmann (LBM) and the control finite volume (CFV) methods for a realistic simulation of nanoparticles deposition for the first time. While the bulk flow is solved using the CFV method, the flow behavior in the deposition layer is evaluated using the LBM model. Nanoparticle movements are also captured using dynamic mesh refinement in CFV in order to accurately predict their behavior. The numerical results are then used for training a deep feed-forward neural network with appropriate boundary conditions (DFNN-BC) to visualize and predict the transient sedimentation behavior. The prediction includes (i) representation of nanoparticles in the LB domain while it is trained during the particle movement in the FV domain and (ii) extension of the computational domain in space, which is three times bigger than the training domain. DFNN-BC is used to study the heat transfer and fluid flow characteristics for Reynolds numbers ranging from 12 to 50 where the working fluid is a nanofluid. The results indicated that using DFNN-BC can reduce the calculation time by 80% compared to the case where the entire domain is solved numerically. The results show that deposition has a maximum effect of 0.32% on the average velocity ratio (AVR) at Re = 12. This variation is related to the viscosity and shear stress of the fluid. With an increment in Reynolds number, the AVR decreases to 0.12%. This is because of the decrement in the number of sedimented nanoparticles. In addition, increasing the velocity significantly affects the rate of sedimentation and volume fraction ratio. It is also seen that the fluid's velocity and density increase by 8.69% and 6.53%, respectively, whereas the viscosity decreases by 7.74%. The findings of this study provide a better understanding of the details of the sedimentation process, such as particle behavior and variation in parameters near the surface, like concentration, thermal conductivity, and viscosity of the sedimentation and the formation of a deposition layer in fluid–particle multiphase flows. This, in turn, is expected to lead to cost savings in maintenance through more precise predictions of service periods for heat transfer equipment.

A GIS-AHP approach for determining the potential of solar energy to meet the thermal demand in southeastern Spain productive enclaves

In this work, the potential of southeastern Spain to host solar thermal plants to meet the heat demands of its industrial enclaves is assessed and presented. For this, the generation of thermal energy for industrial uses in the medium temperature range is estimated, with special emphasis on those areas not connected to the thermal energy distribution networks. This region has been selected due to its high availability of solar resources, while forming a geographic area that presents numerous agrifood industries. These facilities, according to their temperature range heat demands for boiling, pasteurizing, and other food-related processes, are one of the best-suited sectors for the application of medium-temperature solar collectors, both parabolic trough and linear Fresnel. A Geographic Information System and the Analytic Hierarchy Process Method have been used for information management and decision making, respectively. A geographic database was built using layers provided by different information sources on climate, land characteristics and use, industrial activity, and energy infrastructures, including the distance to natural gas distribution pipelines as a specific criterion for decision making. The final result translates into a geographic suitability scale, which revealed that about 5%(1482km2) of the total territory in southeastern Spain is highly suitable for the future development of productive enclaves fed by solar thermal installations, where it is estimated that the energy demand could be met in 42%(9.5TWh/y) with parabolic trough and 65%(14.7TWh/y) linear Fresnel collectors in areas with a score since 7 points.

Nowcasting Hourly-Averaged Tilt Angles of Acceptance for Solar Collector Applications Using Machine Learning Models

Challenges in utilising fossil fuels for generating energy call for the adoption of renewable energy sources. This study focuses on modelling and nowcasting optimal tilt angle(s) of solar energy harnessing using historical time series data collected from one of South Africa’s radiometric stations, USAid Venda station in Limpopo Province. In the study, we compared random forest (RF), K-nearest neighbours (KNN), and long short-term memory (LSTM) in nowcasting of optimum tilt angle. Gradient boosting (GB) is used as the benchmark model to compare the model’s predictive accuracy. The performance measures of mean absolute error (MAE), mean square error (MSE), root mean square error (RMSE) and R2 were used, and the results showed LSTM to have the best performance in nowcasting optimum tilt angle compared to other models, followed by the RF and GB, whereas KNN was the worst-performing model.

Numerical investigation of the thermal-hydraulic performance of horizontal supercritical CO2 flows with half-wall heat-flux conditions

Thermo-hydraulic characteristics of supercritical CO2 (SCO2) flows in horizontal tubes with half-wall heat-flux conditions are investigated numerically, which is a common practice such as applications in solar parabolic trough collectors, while the heat transfer performance and the underlying mechanisms have not been fully understood. In heated flows, buoyancy acts to inhibit heat transfer when the top half of the tube wall is heated, however, when the bottom half of the tube wall is heated, this inhibition is alleviated, and the synergy between the temperature gradient and velocity fields improves thanks to the secondary flow in the near-wall region at the bottom wall. As a result, the heat transfer coefficient is ∼95% higher (on average) than in the case when the top half of the tube wall is heated. When the bottom half of the tube wall is cooled, buoyancy is expected to enhance heat transfer, while the synergy between the temperature gradient and velocity fields is supressed by the secondary flow in the near-wall region at the bottom of the tube. Conversely, when the top half of the tube wall is cooled, the buoyancy effect inhibits heat transfer, while the synergy between the temperature gradient and velocity fields is improved by the secondary flow in the near-wall region at the top of the tube, which eventually leads to an increase of ∼21% (on average) in the heat transfer coefficient relative to the case when the bottom half of the tube wall is cooled. Finally, the heat transfer discrepancy due to different heat flux conditions revealed in this study are employed in a heat exchanger model, indicating that the thermal performance of this device can be increased by ∼6% through an appropriate arrangement of the hot and cold flows without additional costs.

Prototype of a Solar Collector with the Recirculation of Nanofluids for a Convective Dryer

Solar collectors are thermal devices that can trap solar energy and convert it to heat. This heat can be used for different industrial applications, for example, the drying of food is one of the most useful applications of solar collectors. This work aims to design and build a solar collector using nanofluids for the convective drying of food. The dimensions of the solar collector were 1 m2 by 20 cm with an angle of inclination of 45°. The collector was composed of 9-mm thick tempered glass and a heat exchanger in which the nanofluids circulate. Nanofluids were designed based on canola oil and nanopowders (>50 nm) of Al2O3, CuO, and a 1:1 (w/w) mixture of both. Thermal profiles were determined using differential scanning calorimetry (DSC). The solar collector temperatures were recorded using an Agricos® unit. The maximum temperatures of the air leaving the collector were 39.1°C, 44°C, 54°C, and 47.1°C for canola oil, and the nanofluids composed of Al2O3, CuO, and the 1:1 mixture, respectively, with a maximum efficiency of 65.09%. An increase in the outlet air temperature was observed using the nanofluids compared to canola oil alone

Hydrothermal analysis of turbulent fluid flow inside a novel enhanced circular tube for solar collector applications

In this study the impact of a novel enhanced tube on the hydrothermal performance of a working fluid flow is investigated. The behavior of the turbulent flow is analyzed numerically considering new designs of turbulators in a circular tube for applications in solar thermal collectors. Also, the three-dimensional model of the current problem is simulated using Computational Fluid Dynamics (CFD). The steady-state governing equations, of the heat transfer fluid flowing in the circular tube, are solved through a turbulence model. The influences of the angle and pitch of the flow turbulators on the Nusselt number and friction factor are studied. The findings indicate that the Nusselt number increases by adding the flow turbulators in the tubular tube. Additionally, a decrease in the pitch of the flow turbulators leads to larger heat transfer coefficient values, while the friction factor reduces by increasing the distance between the turbulators.

Enhancement of mechanical, thermal and optical properties of TiO2 thin films using glancing angle deposition technique

RF Magnetron sputtering has been used to compare the mechanical, thermal, and electrical characteristics of titanium oxide (TiO2) thin films. The Glancing Angle Deposition methods (GLAD) have been implemented during the deposition of a thin film of TiO2. After annealing thin films on an ITO substrate, X-RD indicates the anatase phase, and SEM investigation confirms the deposition of TiO2 thin films and their surface morphology. The mechanical, thermal, and electrical properties of TiO2 thin films prepared by magnetron sputtering with RF supply have been investigated. Using GLAD deposition, a clear change in thermal conductivity and elastic properties has been observed. Experimental specific heat of thin film deposited at zero angles follows Debye and Einstein equation, while with GLAD deposition specific heat shows an increase in deviation as the angle of deposition increases. With a rise in inclination angle, a clear change in transmission spectra towards a higher wavelength has been observed. Following heat treatment, the optical transmission spectra of thin films with GLAD deposition confirm the formation of fringes and have been shifted towards the higher wavelength side to increase in inclination. Hence, using GLAD deposition on TiO2 plays an important role to change thermal conductivity, specific heat, elastic and electronic properties and which leads to many applications in thermal solar collectors, thermal sensors, thermo-optical switching, and sensing-based industries.

Performance investigation of flat plate solar collector with nanoparticle enhanced integrated thermal energy storage system

Since solar energy is unstable during the day, storage energy is essential to use this energy effectively. An experimental study on a newly designed, integrated solar collector with Nano enhanced-PCM-based energy storage has been carried out for solar collector application at night or when solar radiation is unstable. Before the collector design, performing a performance analysis on three different Nano-enhanced PCM was performed to select the nano-based PCM. To investigate the improvement in energy absorption performance, charging and discharging tests are performed at different flow rates. Amine functionalized paraffin wax (f-NH2-MWCNTs + PW)PCM has been selected due to high thermal conductivity and higher enthalpy gain among four samples, MWCNTS + PW, f-OH-MWCNTS + PW, and f-COOH-MWCNTS + PW. Finned triangular shape container designed for encapsulation of hybrid PCM, f-NH2-MWCNTs + PW. Fourteen triangular shape containers with rectangular profile fins are designed for PCM storage. PCM module has attached to the bottom of the trapezoidal absorber plate of the flat plate solar collector (FPSC). Experimental observation of charging and discharging shows that 21 % decrease in charging time while a 23 % decrease in discharging time observed for f-NH2-MWCNTs + PW compared to pure PCM, at 0.1 % particle volume concentration, flow rate 2.25 LPM and solar intensity 1010 W/m2. Instantaneous charging and discharging efficiencies are enhanced by 24 % and 28 %, respectively, compared to base PW PCM. Overall exergy gain for PCM enhanced system with respect to base FPSC is 12 %.The innovative design NePCM encapsulation and its attachment with the bottom of the trapezoidal absorber plate to utilize excess thermal energy that may go as waste through bottom insulation makes this work distinctive from past and contemporary research. This investigation aims to enhance energy utilization by storing excess amounts in the attached PCM storage. This system can be used for off-time hot water supply and milk pasteurization applications.

Solar-thermal conversion performance of heterogeneous nanofluids

Nanofluids have excellent optical and thermal properties and show great potential for applications in direct absorption solar collectors (DASCs). However, due to the preparation process or force interaction, the non-uniform distribution of NP radii (r) and volume fraction (fv) in heterogeneous nanofluids may affect the solar-thermal conversion performance. In this work, we established a multiscale model based on the finite element method (FEM) coupled with the Monte Carlo (MC) method to investigate the solar-thermal conversion performance of heterogeneous nanofluids. Results show that the non-uniform distribution of r has little effect on the solar-thermal conversion performance due to the weak scattering and strong absorption properties of NPs in dilute nanofluids. The non-uniform distribution of fv has great effect on the local heating flux distribution in the heterogeneous nanofluid, which would affect the collector efficiency (ηcol) due to the different surface heat losses. And a superior ηcol can be achieved at a downward-gradient distribution of r and fv compared with uniform or upward-gradient distributions. This work develops an effective method to evaluate the solar-thermal conversion performance of heterogeneous nanofluids and provides a promising strategy by tuning the distribution of r and fv to enhance the solar collector performance.

The recent progress of nanofluids and the state-of-art thermal devices

Nanofluids have been continuously investigated as innovative fluids in the last decades. The unique thermophysical properties exhibited by nanofluids have led to a variety of applications in modern energy-scarce environments. The purpose of this paper is to provide an overview of recent advances in nanofluids in cooling as well as to summarize the controversies of the existing applications. The development of electronic devices has heightened the need for an effective cooling system. Nanofluids in solar collector applications have greatly improved the thermal efficiency and solar energy utilization compared to conventional fluids, which can greatly alleviate today's energy problems. The cost of nanofluids in commercial applications may be too high, and long-term stability cannot be guaranteed due to the impacts of the thermal efficiency of nanofluids. More innovative approaches are needed to improve the cost and stability of nanofluids to cater to the commercial market. These results aim to provide a deeper understanding of the thermophysical properties and applications of nanofluids and to understand the limitations and potential for future improvements.

A brief review and comparative evaluation of nanofluid application in solar parabolic trough and flat plate collectors

The mixture of nanoparticles with base fluid for heat transfer fluid’s performance enhancement has received wide research attention recently. These nanofluids have been proposed by researchers as a better alternative in different thermal systems. However, the detailed comparison of these fluids is limited in the existing literature. Therefore, in this paper, a detailed parametric comparison of mono/hybrid nanofluids with other fluids’ applications in solar thermal collectors is presented. Specifically, the flat plate and solar parabolic trough collectors are considered within the scope of this study. While the flat plate collectors are modeled for low-temperature applications, the parabolic trough collectors are considered for high-temperature applications. Five nanofluids with different nanoparticles, namely; Al2O3, SiO 2, CuO, Al2O3-ZnO, and Al2O3-Fe are compared with four normal fluids (water, salt (7NaNO 3_40NaNO 2_53KNO2), Therminol_VP1, and Dowtherm_Q). From the energy/exergy efficiencies and useful energy output results of this study, the nanofluids had a better performance when applied in the flat plate collectors and parabolic trough collectors. Also, the working fluids with higher temperature output had lower energy efficiencies and useful energy output. Hence, the base (normal) fluids are more suitable for some specific temperature applications in a flat plate and parabolic trough collectors.

The optical characteristics of C@Cu core-shell nanorods for solar thermal applications

The development of high-efficiency, low-cost and pollution-free new energy has become the focus of scientific research in the 21st century. As for this aspect, exploring more efficient nanoparticles (NPs) for direct absorption solar collectors (DASCs) has become a key issue in solar collector applications. However, the common NPs are usually composed of precious metal gold (Au) or silver (Ag). In this work, we propose a core-shell nanorod surrounded by a Cu shell with a C core and study its absorption properties in solar absorption spectroscopy. The aim is to explore its capability in DASC solar absorption efficiency. The research results show that this nanorod can reduce the application cost while maintaining high solar absorption efficiency. And the possible effects of nanoparticle shell defects during nanoparticle synthesis are considered. The results are as expected, which significantly impacts solar energy absorption. In addition, the C@Cu core-shell nanorods have a wider absorption band and higher resonance absorption peak compared with single Cu NPs. The results indicate that the core-shell composite nanorods proposed in this work have great potential in the application of DASC and are expected to be one of the candidate materials.

Thermal Energy Application and Evaluation of Parabolic Dish Solar Collector

Thermal Energy Application and Evaluation of Parabolic Dish Solar Collector

Investigation on the photothermal performance of carbon quantum dots nanofluid with high-stability

The purpose of this paper is to give an in-depth study on the thermos-physical properties and photothermal conversion characteristics of carbon quantum dot (CQDs). In this study, CQDs nanofluids were synthesized by the simple one-step method. A series of stability analysis experiments were conducted to determine the excellent dispersibility and stability of CQDs nanofluids. The thermal conductivity of the nanofluids was measured by KD-2 Pro, and the results showed an enhancement up to 11 % at 50 °C. And the viscosity of CQDs nanofluids decreased with the concentration and temperature. In addition, it was found that the maximum photothermal conversion efficiency was up to 71.09 %. All the results indicated that the prepared CQDs nanofluids had great potential in the applications of direct absorption solar collectors (DASC).

Review on the structure and application of solar photovoltaic air collector

ABSTRACT At present, people use a large amount of coal, oil and other energy while causing a series of environmental pollution problems. In response to the national 3060 policy, improving the utilization of solar energy is imminent. Solar photovoltaic air collector can not only collect heat efficiently but also reduce the surface temperature of solar cells to improve the photoelectric conversion efficiency. The research progress of solar photovoltaic air collector system improvement and application scenarios are reviewed. The theoretical and experimental research of solar photovoltaic air collector in improving photoelectric/photothermal conversion efficiency is analyzed, the current application scenarios and advantages of solar photovoltaic air collector are discussed, and the research direction of solar photovoltaic air collector is prospected.