Nanofluid-based Direct Absorption Solar Collector Research Articles

Corrosion analysis and performance investigation of hybrid MXene/C-dot Nanofluid-Based direct absorption solar collector

Nanofluids having exceptional thermo-optical characteristics can enhance the performance of direct absorption solar collectors (DASC). Conventional nanofluids have either high optical properties or thermal properties. In this study, carbon quantum dot (C-dot) nanomaterial with high stability and optical absorption along the UV range, and MXene nanoparticles with high thermal conductivity and absorption along visible and near-infrared (NIR) spectral range was selected for synthesizing a hybrid nanomaterial with synergistic thermo-optical properties. Hybrid MXene/C-dot nanofluid exhibits higher stability, thermal conductivity, and complementary absorption properties of individual nanomaterials. A two-step method was used for the synthesis of nanofluids using water as the base fluid. Thermal conductivity, UV–Vis-NIR spectroscopy, and stability analysis were conducted on nanofluids, and the concentration was optimized for corrosion study and application in direct absorption parabolic trough collector (DAPTC). Optimised concentrations of C-dot, MXene, and hybrid nanofluids were 0.15 wt%, 0.1 wt% and 0.15 wt%, respectively. The corrosion study states that copper electrodes dipped in the hybrid nanofluid exhibited the least corrosion rate of 0.6 mm/year with an anticorrosion efficiency of 64.5 % over DI water. Thermal efficiency and entropy generation in the system with different HTFs were measured and compared with that of the base fluid. The study shows that C-dot and MXene/C-dot nanofluids were producing the highest efficiencies of 50.5 % and 47.5 % at a flow rate of 1.2 lpm. This study shows that hybrid MXene/C-dot nanofluid exhibited exceptional thermal stability, reduced corrosion effects, and considerable enhancement in photothermal conversion efficiency of the DASC.

Multi-objective optimization of nanofluid-based direct absorption solar collector for low-temperature applications

Multi-objective optimization of nanofluid-based direct absorption solar collector for low-temperature applications

Electric field combined nanofluid to enhance photothermal efficiency of the direct absorption solar collector

Compared with conventional surface absorption collectors, nanofluid-based direct absorption solar collectors (DASC) have superior optical absorption performance and photothermal conversion efficiency. However, problems such as nanoparticles deposition and large temperature difference inside the collector still limit the development of DASC systems. To solve these problems, this paper firstly proposed to apply the electric field to manipulate the motion of nanoparticles to make the upper and lower nanofluids to exchange heat in the DASC system. The Al2O3-thermal oil nanofluids with the concentration of 0.01–0.3% are prepared, and the transmittance of the nanofluids and photothermal conversion as well as mechanism are performed and analyzed. The results show that the electric field can reduce the temperature difference inside the collector and improve the photothermal conversion efficiency of the DASC system. The temperature rise and photothermal conversion efficiency of 0.2 vol% Al2O3 nanofluid at voltage of 10 kV are 62.11 °C and 87.85%, which are 19.24% and 14.17% larger than those without electric field respectively. Under the action of electric field, the resuspension of deposited nanoparticles and heat transfer between upper and lower nanoparticles work together to improve the photothermal conversion efficiency of DASC system.

Experimental investigation of an asymmetric compound parabolic concentrator–based direct absorption solar collector using plasmonic nanofluids

Plasmonic nanofluid-based direct absorption solar collector (DASC) systems have shown a better perspective over surface-based solar thermalcollectors. These nanofluids demonstrated high thermal performance in photo-thermal conversion efficiency even at minute concentration compared to other testednanofluids. However, very few studies have been reported so farwith real-time outdoor experiments to show the opportunities and challenges in the practical applications of concentrating DASC systems. For the work presented here, an asymmetric compound parabolic concentrator (ACPC)-based DASC system has been designed, fabricated, and tested using mono-spherical gold and silver nanoparticle-based plasmonicnanofluids over several clear sky days at Jalandhar city (31.32° N, 75.57° E), India. The optical and morphological properties of synthesized nanoparticles were studied using UV-Vis spectrophotometry and High-resolution transmission electron microscopy (HR-TEM). Photo-thermal conversion tests were conducted using different working fluids and compared with a flat DASC system under similar operating conditions. The experimental results revealed that ACPC-based DASC system reached a maximum thermal efficiency of around 70% using plasmonic nanofluids which was approximately 28% higher than a flat DASC system with water as the working fluid. The stability analysis showed that plasmonic nanofluids are capable of retaining their optical properties even after several hours of sun exposure. The present study highlights the use of plasmonic nanostructures for achieving high photo-thermal conversion efficiency in concentrating DASC systems.

Nanofluids for Direct-Absorption Solar Collectors-DASCs: A Review on Recent Progress and Future Perspectives.

Owing to their superior optical and thermal properties over conventional fluids, nanofluids represent an innovative approach for use as working fluids in direct-absorption solar collectors for efficient solar-to-thermal energy conversion. The application of nanofluids in direct-absorption solar collectors demands high-performance solar thermal nanofluids that exhibit exceptional physical and chemical stability over long periods and under a variety of operating, fluid dynamics, and temperature conditions. In this review, we discuss recent developments in the field of nanofluids utilized in direct-absorption solar collectors in terms of their preparation techniques, optical behaviours, solar thermal energy conversion performance, as well as their physical and thermal stability, along with the experimental setups and calculation approaches used. We also highlight the challenges associated with the practical implementation of nanofluid-based direct-absorption solar collectors and offer suggestions and an outlook for the future.

Electrostatically Assisted Construction Modified MXene-IL-Based Nanofluids for Photothermal Conversion.

Solar energy, as renewable energy, has paid extensive attention for solar thermal utilization due to its unique characteristics such as rich resources, easy access, clean, and pollution-free. Among them, solar thermal utilization is the most extensive one. Nanofluid-based direct absorption solar collectors (DASCs), as an important alternative method, can further improve the solar thermal efficiency. Notably, the stability of photothermal conversion materials and flowing media is critical to the performance of DASC. Herein, we first proposed novel Ti3C2Tx-IL-based nanofluids by the electrostatic interaction, which consists of functional Ti3C2Tx modified with PDA and PEI as a photothermal conversion material and ionic liquid with low viscosity as the flow medium. Ti3C2Tx-IL-based nanofluids exhibit excellent cycle stability, wide spectrum, and efficient solar energy absorption performance. Besides, Ti3C2Tx-IL-based nanofluids maintain liquid state in a range of -80 to 200 °C, and its viscosity was as low as 0.3 Pa·s at 0 °C. Moreover, the equilibrium temperature of Ti3C2Tx@PDA-IL at a very low mass fraction of 0.04% reached 73.9 °C under 1 Sun, indicating an excellent photothermal conversion performance. Furthermore, the application of nanofluids in photosensitive inks has been preliminarily explored, which is expected to play a role in the fields of injectable biomedical materials and photo/electric double-generation thermal and hydrophobic anti ice coatings.

Effect of reverse irradiation angle on the photo-thermal conversion performance of MXene nanofluid-based direct absorption solar collector

Effect of reverse irradiation angle on the photo-thermal conversion performance of MXene nanofluid-based direct absorption solar collector

Photo‐thermal conversion performance of mono MWCNT and hybrid MWCNT‐TiN nanofluids in direct absorption solar collectors

Solar energy is being widely investigated due to its abundant, renewable, and clean features. Photo-thermal conversion in solar collectors is a direct approach for harvesting solar energy. Compared to the commonly used surface-based solar collectors (SSCs), nanofluid-based direct absorption solar collectors (DASCs) are more efficient. In this work, water-based mono MWCNT and hybrid MWCNT-TiN nanofluids were prepared through a two-step method, aiming at light absorption enhancement of nanofluids for applications in DASCs. The optical and photo-thermal conversion performance of the MWCNT nanofluids was firstly evaluated. The results showed that the MWCNT nanofluids presented high solar absorption capability, and the highest photo-thermal conversion efficiency was obtained at 10 ppm. The TiN nanoparticles were subsequently incorporated to form the hybrid MWCNT-TiN nanofluids. The absorption performance of the hybrid nanofluids was further enhanced. The highest efficiency of the hybrid MWCNT-TiN nanofluids was achieved at the TiN mass fraction of 10 ppm, which was about 6.9%, 6.0%, and 3.8% higher than that of the MWCNT nanofluid at 2000, 4000, and 6000 seconds due to the localized surface plasmon resonance (LSPR) effect of TiN nanoparticles. It was also found that the collector efficiency dropped rapidly with the prolonged irradiation time owing to the convection and radiation heat loss at the elevated temperature. Therefore, effective measures should also be taken to reduce heat loss to maintain high photo-thermal conversion efficiency.

Improving thermal performance of a solar thermal/desalination combisystem using nanofluid-based direct absorption solar collector

Depletion of freshwater resources and reduction of rainfall in arid areas causes water scarcity, which is intensified by population and urbanization growth. In this study, a small-scale solar thermal/desalination combisystem using nanofluid-based direct absorption solar collectors and humidification-dehumidification desalination unit is proposed to supply domestic hot water, space heating, and freshwater demands of a residential building. The dynamic simulation of the system performance in the Hot-Dry climate zone is done using TRNSYS-MATLAB co-simulator. The results indicate that using the proposed combisystem reduces 94.3% and 17% of annual energy consumption for providing domestic hot water and space heating demands, respectively. The freshwater demand is supplied in the range of 11.3% to 100%. In the case of using a flat plate solar collector, the solar fraction for domestic hot water and space heating demands in comparison with nanofluid-based direct absorption solar collectors reduces by 3.7% and 1.7%, respectively. Furthermore, the produced freshwater reduces 18% on average. The payback time using nanofluid-based direct absorption and flat plate solar collectors are 6.4 and 7.8 years, respectively.

Adaptive neuro-fuzzy inference system modeling to predict the performance of graphene nanoplatelets nanofluid-based direct absorption solar collector based on experimental study

In this study, an artificial neural network (ANN) adaptive neuro-fuzzy inference system (ANFIS) model was developed to predict the performance of a low-temperature direct absorption solar collector (DASC) enhanced with nanofluids. The accuracy and the effect of different types of clustering methods such as Subtractive Clustering and Fuzzy c-means (FCM) clustering investigated. Various inlet temperatures, weight percentage of graphene nanoplatelets nanofluids based deionized water (0.0005, 0.001, 0.005 wt%) and flow rates (0.0075, 0.015, 0.0225 kgs−1) were tested. Five inputs used for the ANFIS model: the inlet temperature, rate of solar radiation, ambient temperature, mass flow rate and weight percentage of nanofluid. The ANN provides a single output: the efficiency of the collector. In total, 1536 data points utilized for modeling, including 1075 for the ANN training process and 461 for testing. Overall, the ANFIS model was very accurate at predicting the collector performance. This was indicated by the root mean square error (RSME), the mean absolute percentage error (MAPE), coefficient of determination (R2), and mean bias error (MBE), which calculated to be 0.008, 0.031, 0.999 and 7e-4 respectively. The ANFIS model agrees well with the experimental results.

Highly-efficient nanofluid-based direct absorption solar collector enhanced by reverse-irradiation for medium temperature applications

Abstract The direct absorption solar collector (DASC) with nanofluids is a promising solar energy collection technology. However, various studies have focused on low-temperature applications of nanofluids, and the medium-temperature collection system that involves high-grade energy is always neglected. This study examines the photo-thermal properties of titanium nitride nanofluids with thermal transfer oil as the base fluids under different solar irradiation intensities. The irradiation surface layer reaches ∼160 °C under 5 suns, and a high-temperature gradient develops within the working fluid, producing a low collector photo-thermal efficiency that is below expectation. To overcome these disadvantages, the heat transfer change from thermal conduction to free convection within the fluid is achieved via reverse irradiation direct absorption solar collector (RI-DASC). The performance parameters of this RI-DASC, including the optical properties of nanofluids, steady-state equilibrium temperature, photo-thermal conversion efficiency, and energy utilization distribution are investigated in detail. The experimental results demonstrate that the temperature difference between the irradiation and non-irradiation surfaces for ∼0.005 wt% under 5000 kW/m2 are ∼50 °C and ∼10 °C in DASC and RI-DASC, respectively. The collector photothermal conversion efficiency of DASC (∼40%) is improved to ∼50% for RI-DASC, and the steady-state temperature is enhanced to 165 °C in RI-DASC.

Application of artificial neural network for performance prediction of a nanofluid-based direct absorption solar collector

Recently, artificial neural network techniques have been widely used for the performance prediction of the renewable energy systems, in which solar collectors are one of the most used mechanical equipment. In this paper, the thermal performance of a nanofluid-based direct absorption solar collector is predicted using an artificial neural network based Multi-Layer Perceptron system. In the experimental part of study, nine collector prototypes with different geometries were tested at different conditions to investigate the effect of the collector depth and length on the collector thermal performance and also, to provide the required data for the network evaluation. The collector depth and length, the working fluid flowrate and concentration and the reduced temperature difference are selected as input parameters of the network to estimate the collector efficiency and Nusselt number. The proposed artificial neural network approach proved that the variation of the collector depth of 5–15 mm increases the collector efficiency about 9%, while the collector length has an insignificant effect on the collector efficiency. The Nusselt number of the collector increases considerably by the collector depth and nanofluid flowrate. The proposed network has the best performance for predicting the collector efficiency with nanofluid concentration of 1000 ppm as the input parameter by achieving the MAPE of 1.470%. In the case of predicting Nusselt number, the best performance with MAPE of 2.576% is obtained with collector length of 300 mm. Using the forward stepwise regression selection method, the best combination of input parameters for predicting the Nusselt number is obtained using all input parameters. The consistency of the experimental and predicted results confirms the great ability of artificial neural network to predicting the thermal performance of direct absorption solar collectors.

Ultrastable plasmonic nanofluids in optimized direct absorption solar collectors

Nanofluids used in low-flux direct absorption solar collectors (DASCs) typically encounter critical stability issues due to long-term storage, elevated temperatures, high particle concentrations, and fouling from free surfactants. Here, we developed ultrastable nanofluids, and their properties were used to computationally optimize DASC designs. Broadband photothermal absorption was achieved using citrate- (CIT-) and polyethylene glycol-coated (PEG-) gold nanoparticles, circumventing the need for free surfactants. The nanofluids were subjected to long-term ambient storage, high particle concentrations, and incremental heating to analyze their stability and utility in DASCs. Electrosteric stabilization (PEG + CIT) provided superior colloidal stability and more consistent optical properties; chemical and colloidal stability was verified for 16 months, the longest demonstration of stable nanofluids under ambient storage in the solar literature. Optical measurements of the stabilized solar nanofluids were fed into a DASC optimization model. A constrained generalized pattern search (GPS) algorithm simultaneously maximized collector thermal power-gain and minimized nanoparticle mass loading, while maintaining a collector temperature-gain target. Ultimately, by simultaneously developing ultrastable solar nanofluids, minimizing nanoparticle loading requirements, and maximizing collector thermal power gain, the outcomes from this study are considered significant steps towards deploying efficient and reliable low-flux, nanofluid-based DASCs in field applications.

Photothermal efficiency enhancement of a nanofluid-based direct absorption solar collector utilizing magnetic nano-rotor

The concentration of nanofluids and receiver depth are important factors that significantly affect the efficiency of direct absorption solar collectors. In the current work, the impact of the two factors is investigated using reduced graphene oxide/ethanol glycol nanofluids. The results show uneven temperature distribution in the receiver at high nanofluid concentration or when the receiver is deep. To overcome these issues, a forced convection nanofluid absorption system using α-Fe2O3 magnetic nanoparticles as the nano-rotor, and driven by an external rotating magnetic field, was designed. The mechanism of the new system is compared with the conventional one in detail. The photothermal conversion efficiency of the binary nanofluids (α-Fe2O3–graphene oxide/ethanol glycol nanofluids) in the new system reaches 56.8%, which is 14.5% higher than non-external rotating magnetic field nanofluids, for an RGO content of 0.007 wt%. This enhancement is ascribed to two effects of α-Fe2O3: improving the optical absorption capacity of binary nanofluids and acting as a nano-rotor. The optimum photothermal conversion efficiency is achieved at an RGO/α-Fe2O3 ratio of 3 in the current system.

Silicone oil envelope for enhancing the performance of nanofluid-based direct absorption solar collectors

Nanofluids inherently have high emissivity in the mid-infrared region making them unsuitable for satisfying the conditions of solar selectivity required for direct absorbers. In this study, a layer of silicone oil is located above nanofluid comprising of graphite nanoparticles and deionized water. Silicone oil layer is shown to act as a barrier against the infrared emissions from the nanofluid. High transparency of silicone oil in the visible solar spectrum and high absorptivity in the mid-infrared wavelength range made it an excellent candidate for this study. Solar selectively was achieved by using two different liquid layers (nanofluid and silicone oil) in direct thermal contact. Silicone oil layer on the top of the nanofluid resulted in an approximately 17% higher temperature rise in the nanofluid.

A review of nanofluid-based direct absorption solar collectors: Design considerations and experiments with hybrid PV/Thermal and direct steam generation collectors

Over the last 100 plus years, solar thermal energy has been used for residential heating applications, industrial process heating, electricity generation, and thermochemical reactions. Because of the vast number of applications, numerous designs have been developed to improve the efficiency of converting incoming solar energy into useful heat and to lower the cost. Conventional solar thermal collectors required a solid surface to absorb and convert incoming solar energy to useful thermal energy. Developments in materials science have enabled a new type of absorber—a volumetric absorber—which utilizes nanoparticles suspended in a fluid to absorb sunlight. Since most working fluids only weakly absorb sunlight, well-engineered ‘nanofluids’ are attractive because only a low volume fraction of nanoparticles is needed to obtain a large shift in the optical properties. This review, on the 10-year anniversary of the first appearance of nanofluid-based direct absorption solar thermal collectors, provides a forward-looking perspective on the challenges and opportunities associated with nanofluids as direct absorbers. Through a critical comparison of design considerations, as well as the most recent experimental results of less well explored areas like hybrid photovoltaic/thermal systems and direct steam generation, this review aims to provide discourse on the next steps for development.

Four-way coupling of particle-wall and colloidal particle-particle interactions in direct absorption solar collectors

A novel model based on the Eulerian-Lagrangian approach was introduced in order to capture the physics of particle-fluid, particle-wall, and colloidal particle-particle interactions through four-way coupling in low-flux nanofluid-based direct absorption solar collectors (DASCs). This was accomplished by means of a computationally efficient particle-particle-interaction detection algorithm implemented within the frame of an in-house fluid-particle coupling algorithm that allowed for the simultaneous evolution of the carrier and particulate phases. The optical, thermal, and dispersion effects of particle-wall and colloidal particle-particle interactions were investigated over a range of particle volume fractions ϕp and flow Reynolds numbers (Re). It was found that the outcome of a particle-wall collision is either particle deposition or rebound, depending on the balance between kinetic energy of the incoming particle and particle-wall van der Waals potential energy. Brownian motion was established to be the main deposition mechanism for nanoparticles in the boundary layer. As Re decreased, Brownian motion of nanoparticles dominated over convection, which led to higher deposition rates. Deposited particles were found to cause greater attenuation of solar radiation near the collector upper surface, especially in the visible region of the solar spectrum. Whereas in the infrared region, radiation attenuation became less sensitive to particle deposition. The drop in collector efficiency when particles are allowed to deposit relative to the case when particles are not allowed to deposit was highest for low Re and ϕp. Yet, regardless of Re, an increase in particle surface potential led to a better dispersion of nanoparticles. Furthermore, colloidal interparticle interactions were found to have a negligible effect on collector performance. The results highlight the important effects of particle deposition and non-uniform particle distribution on the performance of DASC systems, which cannot be captured using conventional single-phase models.

Effect of V-shaped rib roughness on the performance of nanofluid-based direct absorption solar collectors

Solar heating systems, which used nanofluid-based direct absorption solar collectors, have been recently introduced as the more efficient solar thermal systems because of the volumetric absorption of solar radiation within the direct absorption solar collectors. In this paper, a new direct absorption solar collector is constructed with the V-shaped ribs on its bottom surface in order to study the outdoor thermal performance of the conventional and ribbed collector, experimentally. Using graphene oxide nanofluid as the working fluid, the energy and exergy efficiencies of the conventional and ribbed direct absorption solar collectors are obtained by varying the nanofluid volume fraction, flow rate and the rib geometry (forward and backward rib). Measuring the spectral transmittance of the nanofluid samples shows that the absorbed energy fraction (F) for collector channel depth of 1 cm is 50.9%, 59.82%, 64.5% and 65.3% for nanofluid samples of 125 ppm, 250 ppm, 500 ppm and 1000 ppm, respectively. In volumetric flow rate of 15 L h−1, the zero-loss efficiency for BR-DASC and FR-DASC is increased up to about 16.6% and 11.7%, compared to DASC. These values attain 21% and 13.4% when the volumetric flow rate increases from 15 to 45 L h−1. The optimum volume fraction of graphene oxide nanofluid is 500 ppm in conventional and forward-ribbed direct absorption solar collectors in terms of both energy and exergy efficiencies. The higher friction factors, as a result of ribs, lead to lower exergy efficiency of the ribbed direct absorption solar collector in comparison with the conventional one.

Energy and exergy analysis and optimization of low-flux direct absorption solar collectors (DASCs): Balancing power- and temperature-gain

Abstract The objective of this work is to determine the balance between power gain and temperature gain in nanofluid-based direct absorption solar collectors (DASCs). The radiative transfer and energy conservation equations were numerically coupled and solved. It was observed that, despite the low exergy efficiency in low-flux DASCs, the design point at which exergy efficiency is maximized provides a compromise between power- and temperature-gain. The trade-off between power gain and temperature gain was investigated where it was observed that a collector efficiency of up to 55% can be obtained without sacrificing temperature gain. Beyond that, the trade-off between power- and temperature-gain dominates. Moreover, by expanding the parameter space, some seemingly contradictory results reported in the literature have been examined and justified regarding the effects of collector length on energy efficiency and flow velocity on exergy efficiency. Finally, the effect of nanofluid thermal conductivity on collector performance was found to be a function of the dominant solar radiation absorption mechanism. Comparing different base fluids, it was found that for water the energy efficiency was less sensitive to changes in nanofluid thermal conductivity when compared to oil.

Direct absorption solar collector (DASC) modeling and simulation using a novel Eulerian-Lagrangian hybrid approach: Optical, thermal, and hydrodynamic interactions

A novel two-way coupled Eulerian-Lagrangian hybrid approach was used to model nanofluid-based direct absorption solar collectors via a transient in-house code. By capturing the discrete nature of nanoparticles as well as motion and temperature slips between the carrier and dispersed phases, the proposed approach overcomes limitations of fully-continuous models by coupling the fully-resolved local nanoparticle concentration with the nanofluid optical and thermal properties. In particular, it was established that the non-uniform distribution of nanoparticles results in the spatially non-uniform attenuation of solar radiation due to spatial variations in the nanofluid optical properties. Moreover, the volumetric absorption and temperature fields were computed and compared to the conventional fully-continuous fields generated based on a homogeneous nanoparticle distribution assumption. The Reynolds number was found to have a strong effect on the local nanoparticle distribution in the flow of a nanofluid in a direct absorption solar collector, which greatly affects optical and thermal properties and performance of the nanofluid and collector. A critical flow Reynolds number was identified, after which the assumption of a homogenous particle distribution becomes inacceptable, and the homogeneous, fully-continuous modeling approach yields inaccurate results. In particular, the fully-continuous Eulerian modeling approach increasingly overestimates solar radiation extinction in vicinity of the channel top surface with an increase in Reynolds number, especially for Reynolds numbers ≥1. Effects on the coupled optical, thermal, and hydrodynamic interactions within the direct absorption solar collector due to the deviation of local nanoparticle distribution from the commonly-used homogeneous-nanoparticle-distribution assumption were investigated. Namely, new insights have been gained with regards to the impact of transverse nanoparticle migration, flow Reynolds number, mean nanoparticle concentration, and nanoparticle material type on the nanofluid temperature distribution, spectral radiation heat flux distribution, nanofluid optical properties, and collector optical and thermal performance metrics and losses. It was found that nanofluid optical properties in the visible radiation spectrum are highly dependent on the local nanoparticle concentration, which is in contrast to the infrared spectrum, where variations in the nanoparticle distribution have little effect on optical properties. The obtained results systematically identify the limitations of conventional direct absorption solar collector design tools and propose a new modeling approach that resolves those limitations as well as expands our physical understanding of the coupled optical, thermal, and hydrodynamics interactions within a volumetric absorption system.