Nanofluid-based Solar Collector Research Articles

Enhancing upgraded solar still performance in summer and winter through nanofluid-based solar collectors

Nanofluid-based upgraded solar still had its day and nighttime performance evaluated while it was in the sunshine during the summer and winter seasons. At various points throughout the day, basin water was heated by both the solar pond and a nanofluid-based volumetrically absorbing solar collector (NBSC). The comparison of paraffin oil-based surface absorption solar collectors demonstrates that volumetric heating and surface heating work together to boost distillate yield. Sensible heat storage in the NBSC benefits from volumetric heating. The performance of upgraded stills using paraffin oil-based solar collectors (PBSC) and nanofluid-based solar collectors (NBSC) was superior to that of the traditional (reference) stills at basin water depths of 30, 40, and 50 mm. Using 40 mm BWD (Basin Water Depth) in conjunction with NBSC, the upgraded still's maximum efficiency, and productivity were 35.65% and 5.15 l/m2, respectively. The typical winter and summer day distillate produced by the upgraded stills attached with NBSC and solar pond was found to be 2.05 L/m2/day and 4.62 L/m2/day, respectively. The diurnal and nocturnal distillate produced during summer experiments was 144.02% and 64.52% higher than in winter.

Direct absorption nanofluid-based solar collectors for low and medium temperatures. A review

Solar energy is expected to play an important role in the decarbonization of the energy and industrial sectors. Low and medium temperature (<400 °C) solar thermal collectors have proved to be a reliable solution to supply heat and decarbonize the industrial sector, with over 800 Solar Heat for Industrial Processes (SHIP) plants put in operation in the last decade. Governmental support policy is a key factor for solar thermal energy to play a major role in CO2 emission reduction, which require improving the efficiency of solar collectors and reducing costs. Recent studies have demonstrated the potential of nanoparticles to enhance the optical properties of heat transfer fluids for direct absorption solar collectors (DASC). In a DASC the transfer fluid absorbs volumetrically the incident radiation, resulting in a more homogeneous temperature distribution and less heat losses than in conventional surface collectors. In this paper, the current state-of-the-art of SHIP installations and conventional surface collectors is presented, and a critical literature review dedicated to nanofluid-based DASC for both concentrating and non-concentrating collectors is provided. The key findings and the challenges to be overcome toward promoting the development of nanofluid-based DASC for SHIP applications are discussed.

Heat and Fluid Flow Characteristics of Nanofluid in A Channel Baffled Opposite to The Heated Wall

In this paper, a nanofluid-based solar collector duct equipped with baffles is examined numerically. Baffles are located on the back plate to guide nanofluid flow toward absorber plate for heat transfer enhancement purposes. Cu-water nanofluid with fixed flow rate and concentration in the baffled duct are investigated for thermohydraulic mechanisms. Baffles with different inclination angles, heights and pitches are considered in this study. Numerical simulations are performed using Ansys fluent software with verified results compared to those of an experiment in the literature. The results show that the baffle angle 60° causes the lowest thermohydraulic performance. Because in the angle range of 30 to 60° the heat transfer is less variable while the pressure loss increases sharply. At the baffle pitch of 40 mm, there is no reattachment point at the non-heated surface. At the angle of 90°, three eddies are formed around a baffle. The slope linear regression analysis yields that baffle height has the strongest effects on thermohydraulic performance followed by baffle pitch and baffle angle. Nanofluid pressure loss respectively increases with baffle height and baffle angle at the rate of 0.463675 and 0.0049607 while absorber plate temperature respectively decreases with the baffle height and baffle angle at the rate of -0.176746 and -0.001377. Flow patterns and isotherms of all the cases examined are presented and analyzed in this study.

Analysis on the extinction properties of nanofluids for direct solar absorption

Abstract Compared with conventional surface-based solar collectors, direct solar thermal collectors based on nanofluids have an improved photothermal efficiency. Optical extinction characteristics of nanofluids have an important effect on the photothermal properties. The influence of distribution characteristics of extinction spectra on photothermal properties is investigated. Extinction spectra of Gaussian and uniform distributions are constructed based on the average extinction coefficient of plasmonic Ag nanofluid. Temperature rises in nanofluids with different extinction spectra are calculated. With the broadening of extinction peak, the solar absorption properties are enhanced, and the temperature rise is improved. The uniformly distributed extinction spectrum has strong solar absorption and increased temperature rise even at a small average extinction coefficient. The extinction coefficient is proportional to the concentration of nanofluids. Therefore, nanofluids of uniform distributed extinction spectra can have strong photothermal properties even at low concentration, which is conducive to the stability and reliability of nanofluid-based solar collectors.

Investigation of factors influencing the performance of nanofluid-based direct absorption solar collector using Taguchi method

The performance of nanofluid-based solar collector depends on different factors like nanoparticle material, base fluid, mass fraction of nanoparticles, height of the collector, length of the collector, incident solar flux, mass flow rate of the nanofluid in the collector. In order to quantify the effect of nanoparticle material, optical properties of different nanofluids (different nanoparticles dispersed in DI water) were measured using spectrophotometer. After studying the optical signatures of the nanofluids, solar-weighted absorptivity of the nanofluids was calculated to evaluate the efficient nanoparticle material for harnessing solar irradiation. It has been found that amorphous carbon nanoparticles-based fluid has highest absorptivity at low mass fractions and is suitable for harnessing solar energy. Further, the performance of nanofluid-based solar collector has been investigated numerically using amorphous carbon nanoparticles. For the purposes of this analysis, a two-dimensional steady-state heat transfer model has been developed for a collector in which the nanofluid flows horizontally and is heated with normally incident solar irradiation. During the analysis carried out in this study, five factors were chosen (height of the collector, nanofluid mass flow rate, solar irradiation incident flux, nanoparticle mass fraction, and length of the collector). The influence of variation in these five factors on the overall performance of the solar collector (i.e., outlet temperature) was analyzed using the Taguchi method. In order to carry to this analysis, the values of these five factors were varied at three levels. Based on these variations, the L18 standard orthogonal array was prepared, and the matrix containing the 18 sets of combinations was organized. The results showed that two factors (length of the collector, and the incident solar flux) exhibited a strong increasing trend, while one factor (nanoparticle mass fraction) exhibited an optimizing trend on the output (outlet collector temperature). Further, from the calculations it has been observed that 60 mg L−1 is an optimum mass fraction at which maximum collector efficiency can be achieved for the length of the collector (= 1 m), height of the collector (= 10 mm), incident flux (= 1000 W m−2), mass flow rate (= 0.010 kg s−1).

Parametric study of the energy efficiency of the HDH desalination unit integrated with nanofluid-based solar collector

Humidification–dehumidification desalination (HDH) systems have been found to be ideal for treating seawater at a smaller scale. It requires thermal energy to drive the processes inside the HDH system which can be supplied by a renewable source of energy (such as solar energy). For this purpose, a nanofluid-based direct absorption solar collector (DASC) can be used which has a relatively higher thermal efficiency, as compared to the conventional surface absorption-based solar thermal collector. In this study, these two sub-systems—HDH and DASC, are coupled through a heat exchanger. In this paper, a numerical model has been prepared for DASC-based HDH system which aims to evaluate the energy efficiency of this combined system by calculating gained output ratio as a function of various parameters, related to the DASC, such as particle volume fraction (fv), height (H) and length (L) of the collector, mass flow rate of nanofluid inside the collector $$(\dot{m}_{\text{nf}} )$$ and amount of solar energy incident (q) on the collector. The performance of the combined or integrated system has also been verified against the various parameters related to HDH system such as ratio of mass flow rate of the saline water to the dry air $$(\dot{m}_{\text{w}} /\dot{m}_{\text{da}} )$$ , effectiveness of the humidifier (eH) and dehumidifier (eD) and the bottom temperature $$(T_{{{\text{w}}_{1} }} )$$ . Also the results of the numerical model prepared in this study have been compared with those available in the literature. Finally, the applicability and benefits of using nanofluids in various thermal desalination techniques have been presented.

Experimental investigation of thermal performance for direct absorption solar parabolic trough collector (DASPTC) based on binary nanofluids

Nanofluids can be utilized to capture and distribute effectively solar radiation due to the capability of their nanoparticles in the liquid medium to scatter and absorb solar radiation. Hence, nanofluid-based solar collectors have the potential to harness solar radiant energy. Proper nanofluids can be selected for solar applications based on their potential optical properties. Binary nanofluids as a new class of nanofluids comprising a base fluid and two different nanoparticles may exhibit a behavior different from any of their components. The behavior of such nanofluids has not yet been extensively investigated. The present experimental study was, therefore, designed and implemented to investigate the absorption and thermal conductivity of binary nanofluids and to evaluate the factors involved in their optimal stability. For this purpose, two dissimilar nanoparticles, i.e. CuO (with high absorption properties) and γ-Al2O3 (with high scattering properties) were chosen to prepare a binary nanofluid. Results showed that the thermal conductivity and aggregation of the prepared nanofluid were highest and lowest, respectively, under optimal stability conditions. As another main goal of this study, the effect of the binary nanofluid on the thermal efficiency of direct absorption solar parabolic trough collectors (DASPTCs) was evaluated. Results showed that solar irradiance is absorbed and converted into a significant amount of sensible heat along the length of the receiver pipe. Experiments with the DASTPC collector also revealed that the thermal efficiency of the system could be enhanced by increasing nanoparticle volume fraction and nanofluid flow rate.

Second law analysis of a nanofluid-based solar collector using experimental data

The present study deals with the entropy generation analysis of a flat-plate solar collector using SiO2/ethylene glycol–water nanofluids. For this purpose, available experimental data on the performance of a flat-plate solar collector are exploited for estimating the entropy generation in the system. Ethylene glycol–water (EG–water) and EG–water-based nanofluids having three different nanoparticle volume fractions including 0.5, 0.75, and 1 % are considered as the working fluids. The results are presented in terms of exergy efficiency, entropy generation parameter, and Bejan number for three different mass flow rates and various solar radiation intensities. It is found that when nanofluid concentration increases from 0 to 1 %, exergy efficiency enhances up to 62.7 % for a mass flow rate of 1 L min−1, whereas the corresponding increases in mass flow rates of 1.75 and 2.5 L min−1 are 45.2 and 39.7 %, respectively. The results also elucidate that entropy generation parameter, which is a function of entropy generation, ambient temperature, and solar radiation, reduces with increasing the nanofluid concentration.

Measurement and Control System for Thermosolar Plant and Performance Comparison Between Traditional and Nanofluid Solar Thermal Collectors

Abstract Aim of this work is the design of a programmable electronic system for monitoring the environmental parameters and managing the electrical functions of a thermo-solar plant. The designed control unit detects data from temperature and light sensors, processes acquired information and commands external equipments (pumps, electric valves and power supplies) in order to optimize plant performances and maximize efficiency and energy savings. Recently several researches, in the field of solar thermal energy production, have demonstrated that nanofluid-based solar collectors present higher conversion efficiency. In this context, the designed control unit can be used to detect their operation parameters in order to compare the performances of nanofluidbased solar collector with those of traditional one. The electronic experimental setup is capable to monitor, at the same time, the two different types of solar collector in similar environmental conditions and to show on touch screen display the detected performances. In order to have reference data, experimental measurements have been carried out by using traditional water and Al2O3-based nanofluid thermo solar collectors. The obtained experimental data showed the benefit in terms of efficiency in the use of nanofluid as heat transfer fluid in such a system.

Experimental and numerical investigation of nanofluids heat transfer characteristics for application in solar heat exchangers

One of the innovative methods of improving heat transfer characteristics of heat exchangers in solar systems is applying nanofluids as the heat transfer media. In this study, laminar convective heat transfer of water-based TiO2 nanofluid flowing through a uniformly heated tube has been investigated via experiments and numerical modeling. The thermal conductivity and dynamic viscosity of the prepared nanofluids have also been measured and modeled at different temperatures and nanoparticle concentrations. Based on the results, a maximum enhancement of 21% in average heat transfer coefficient has been obtained using TiO2/water nanofluids. For the numerical section, the single-phase model was compared with the common two-phase numerical approaches. The numerical investigation indicated that the predicted heat transfer coefficients using single-phase and common two-phase approaches, even based on experimental thermophysical properties of nanofluids, underestimate and overestimate the experimental data, respectively. Therefore, some modifications are implemented to the common two-phase model in order to obtain more accurate predictions of the heat transfer characteristics of nanofluids. This modified model investigated the effects of particle concentration, particle diameter, and particle and basefluid material on the heat transfer rate at different Reynolds numbers. The results indicated that the convective heat transfer coefficient increases with an increase in nanoparticle concentration and flow Reynolds number, while particle size has an inverse effect. The obtained results can be very useful to the investigation of the potential application of nanofluid-based solar collectors.

A Review on the Performance of the Nanofluid Based Solar Collectors – Solar Energy

Using nanofluids as an innovative kind of liquid blend with a trivial volume fraction (in percent) of nanometer-sized solid particles in suspension is a fairly a novel arena or idea. The objective of this presented review paper is to inspect the performance of the nanofluid-based solar collector (NBSC). In past few years for a number of experimental and industrial thermal engineering systems solar energy has proven to be the best input energy source. The scarcity of fossil fuels and environmental contemplations motivated the researchers to utilize alternative energy sources such as solar energy, wind energy, tidal energy etc. Therefore, it is essential to boost the performance of the solar thermal engineering systems. Because of better rheological properties nanofluids are utilized to build up the performance of conventional solar thermal engineering systems. Therefore, major part of this presented review paper lays a main emphasis to investigate the effects of nanofluids on the performance of solar collectors. Some proposals are also given to use the nanofluids for future work in different solar thermal engineering systems such as parabolic trough systems (PTS), solar thermoelectric cells and finally, the challenges of using nanofluids in solar energy devices are reviewed in brief.

TO STUDY THE BEHAVIOR OF NANOFLUIDS IN HEAT TRANSFER APPLICATIONS: A REVIEW

Using nanofluids as an innovative kind of liquid blend including trivial volume fraction (in percent) of millimeter or nanometer size powdered particles with base fluids is fairly a novel arena or idea. The objective of this presented review paper is to inspect the performance of the nanofluid-based solar collector (NBSC). In past few years for a number of experimental and industrial thermal engineering systems solar energy has proven to be the best input energy source. Nanofluids are the fluid that has shown various developments in the thermal properties over the past decade. In the field of nanotechnology, nano fluids have a great potential to enhance the rheological properties like thermal conductivity of base fluid like water, ethanol etc. Nanofluids are the suspension of mainly the base fluid like water in nanoparticles such as alumina (Al2O3) of size micro or milimetre and shows distinctive features than that of conservative fluids used. Because of better rheological properties nanofluids are utilized to build up the performance of conventional solar thermal engineering systems. The presented literature review presents a detailed discussion about the solar collectors, applications of nanofluids in solar collector and their augmentation in thermo physical properties.

Numerical Investigation of Nanofluid-based Solar Collectors

Solar thermal collectors are applicable in the water heating or space conditioning systems. Due to the low efficiency of the conventional collectors, some suggestions have been presented for improvement in the collector efficiency. Adding nanoparticles to the working fluid in direct absorption solar collector, which has been recently proposed, leads to improvement in the working fluid thermal and optical properties such as thermal conductivity and absorption coefficient. This results certainly in collector efficiency enhancement. In this paper, the radiative transfer and energy equations are numerically solved. Due to laminar and fully developed flow in the collector, the velocity profile is assumed to be parabolic. As can be observed from the results, outlet temperature of collector is lower than that obtained using uniform velocity profile. Furthermore, a suspension of carbon nanohorns in the water is used as the working fluid in the model and its effect on the collector efficiency is investigated. It was found that the presence of carbon nanohorns increases the collector efficiency by about 17% compared to a conventional flat-plate collector. In comparison with the mixture of water and aluminium nanoparticles, a quite similar efficiency is obtained using very lower concentration of carbon nanohorns in the water.

Applicability of flashing desalination technique for small scale needs using a novel integrated system coupled with nanofluid-based solar collector

The present study introduces an attempt for the application of flash desalination technique for small scale needs. An integrated system uses a flashing desalination technique coupled with nano-fluid-based solar collector as a heat source has been made to investigate both the effect of different operating modes and that of the variation of functioning parameters and weather conditions on the fresh water production. The flashing unit is performed by similar construction design technique of commercial multi-stage flashing (MSF) plant. The thermal properties of working fluid in the solar collector have been improved by using different concentrated nano-particles. Cu nano-particle is used in the modeling to determine the proper nano-fluid volume fraction that gives higher fresh water productivity. An economic analysis was conducted, since it affects the final cost of produced water, to determine the cost of fresh water production. Although a system may be technically very efficient, it may not be economical. The effect of different feed water and inlet cooling water temperatures on the system performance was studied. The mathematical model is developed to calculate the productivity of the system under different operating conditions. The proposed system gives a reasonable production of fresh water up to 7.7l/m2/day under the operation conditions. Based on the cost of energy in Egypt, the estimated cost of the generated potable water was 11.68US$/m3. The efficiency of the system is measured by the gained output ratio (GOR) with day time. The gained output ratio (GOR) of the system reaches 1.058. The current study showed that the solar water heater collecting area is considered a significant factor for reducing the water production cost. Also, the produced water costs decrease with increasing the collecting area of the solar water heater. The volume fractions of nano-particle in solar collector working fluid have a significant impact on increasing the fresh water production and decreasing cost.