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South Africa currently has the highest carbon emission intensity per kilowatt of electricity generation globally, and its government intends to reduce it. Some of the measures taken by the government include a reduction of emissions in the building sector using solar water heating (SWH) systems. However, there is currently no study in the country that comprehensively assesses the technical, economic, and environmental impact of SWH systems across the country. This study therefore used the System Advisor Model (SAM) to model two different technologies of SWH systems (i.e., flat plate (FPC) and evacuated tube (EPC) SWH) at five different locations (i.e., Pretoria, Upington, Kimberley, Durban, and Cape Town) strategically selected across the country. According to the study, the optimum azimuth for both the evacuated tube and flat plate SWH system in South Africa is 0°. Installing FPC and EPC at the different locations would yield payback periods of 3.2 to 4.4 years and 3.5 to 4.3 years, respectively. Comparably, levelized cost of energy for the FPC and EPC will range from 7.47 to 9.62 cents/kWh and 7.66 to 9.24 cents/kWh, respectively, based on where the SWH system is located. Depending on where the facility is located, the annual cost savings for the FPC system would be between $486 and $625, while the EPC system would save between $529 and $638. Using SWHs can reduce CO2 emissions by 75–77% for the evacuated tube system and 69–76% for the flat plate system annually, depending on the location.

The large amount of energy consumed is produced as a result of the combustion of fossil fuels. This is due to the obvious pollution of the environment, the high cost and the possibility of running out of these sources that make alternative energy sources more important. Sunlight is a popular renewable energy source. Among the various alternatives, harnessing solar energy has become a promising option in all over the world being less expensive, environmentally friendly and impermeable. Parabolic collectors are an effective way to produce steam in thermoelectric power plants to convert radiant energy into thermal energy. However, these complexes can be improved by improving their design and modifying parameters related to thermal behavior. Heated receiver tubes are key components of a PTC device. These types of improvements can be achieved through use of Nano fluids and insert fins, or porous materials with in receiver tube to enhance the PTC performance. The current review papers seek to increase heat transfer in the receiver tube and reduce heat loss to improve convection fluid heat transfer. [ABSTRACT FROM AUTHOR]

Abstract Nowadays, direct absorption solar collectors are a new concept of solar collectors which have attracted special attention. The type of heat transfer fluid (HTF) has a significant influence on the efficiency of this kind of collector. Therefore, in this study, a wide range of working fluids including mono nanofluid (Al 2 O 3 and CuO), binary nanofluid, and especially the incorporation of a new hybrid combination of nanofluid and microencapsulated phase change material (MPCM), are used as the working fluids of a triple‐walled direct absorption evacuated tube solar collector. The computational fluid dynamics (CFD) method is used for simulating the collector and investigating the effect of different parameters including volume fraction, base fluid, mass flow rate, and type of absorber tube structure (double‐ and triple‐walled) on collector thermal performance. Results show that binary nanofluids of 0.06% Al 2 O 3/0.002% CuO/water and 0.06% Al 2 O 3/0.002% CuO/ethylene glycol (EG) have the largest working fluid temperature differentials equal to 48.31 and 66.5 K, respectively. It was inferred that, at the mass flow rate of 2.7 kg / h, the efficiency is obtained to be 60.29% employing binary/EG nanofluid, which is 8.68% and 15.31% higher than CuO/EG and Al 2 O 3/EG nanofluids, respectively. Inserting the hybrid CuO nanofluid/MPCM leads to an improvement of 1.14% and 1.22% in the efficiency of triple‐ and double‐walled collectors, respectively, with respect to the individual usage of the nanofluid. The thermal efficiency of the double‐walled structure is higher than triple‐walled considering all HTFs.

Abstract This study discusses an evacuated tube collector-type solar water heater (ETCSWH) using a phase change material (PCM) chamber with fins, nanofluid, and nano-enhanced phase change material (NEPCM). First, the charging phenomena in a horizontal triplex tube heat exchanger (TTHX) equipped with fins, natural convection, and an ETCSWH system without PCM is simulated to validate the solution. The impact of adding fins and nanoparticles with a volume fraction of 3% of Al2O3 and Cu to paraffin wax and water-based fluid, respectively, on the unit's efficiency has been examined. The proposed system for the PCM melting process, heat storage, fluid flow behavior in the system, and velocity distribution and temperature contour in the storage tank and three parts of the absorber tube have been evaluated using ANSYS FLUENT software in a three-dimensional and transient simulation. The results show that Case 8 has improved by 39.7% compared to Case 1 and Case 4 by 5.2% compared to Case 1 within 4 h of the melting process. Also, Case 8 with a 43% and 6.4% shorter melting time than Cases 1 and 5 has the best performance and the greatest heat transfer rate. The productivity of the ETCSWH system is considerably enhanced by the use of fins, NEPCM, and nanofluid.

Nowadays, direct absorption solar collectors are a new concept of solar collectors which have attracted special attention. The type of heat transfer fluid (HTF) has a significant influence on the efficiency of this kind of collector. Therefore, in this study, a wide range of working fluids including mono nanofluid (Al2O3 ${\text{Al}}_{2}{{\rm{O}}}_{3}$ and CuO), binary nanofluid, and especially the incorporation of a new hybrid combination of nanofluid and microencapsulated phase change material (MPCM), are used as the working fluids of a triple‐walled direct absorption evacuated tube solar collector. The computational fluid dynamics (CFD) method is used for simulating the collector and investigating the effect of different parameters including volume fraction, base fluid, mass flow rate, and type of absorber tube structure (double‐ and triple‐walled) on collector thermal performance. Results show that binary nanofluids of 0.06% Al2O3 ${\text{Al}}_{2}{{\rm{O}}}_{3}$/0.002% CuO/water and 0.06% Al2O3 ${\text{Al}}_{2}{{\rm{O}}}_{3}$/0.002% CuO/ethylene glycol (EG) have the largest working fluid temperature differentials equal to 48.31 and 66.5 K, respectively. It was inferred that, at the mass flow rate of 2.7 kg/h $\mathrm{kg}/{\rm{h}}$, the efficiency is obtained to be 60.29% employing binary/EG nanofluid, which is 8.68% and 15.31% higher than CuO/EG and Al2O3 ${\text{Al}}_{2}{{\rm{O}}}_{3}$/EG nanofluids, respectively. Inserting the hybrid CuO nanofluid/MPCM leads to an improvement of 1.14% and 1.22% in the efficiency of triple‐ and double‐walled collectors, respectively, with respect to the individual usage of the nanofluid. The thermal efficiency of the double‐walled structure is higher than triple‐walled considering all HTFs. [ABSTRACT FROM AUTHOR]

This study discusses an evacuated tube collector-type solar water heater (ETCSWH) using a phase change material (PCM) chamber with fins, nanofluid, and nano-enhanced phase change material (NEPCM). First, the charging phenomena in a horizontal triplex tube heat exchanger (TTHX) equipped with fins, natural convection, and an ETCSWH system without PCM is simulated to validate the solution. The impact of adding fins and nanoparticles with a volume fraction of 3% of Al2O3 and Cu to paraffin wax and water-based fluid, respectively, on the unit's efficiency has been examined. The proposed system for the PCM melting process, heat storage, fluid flow behavior in the system, and velocity distribution and temperature contour in the storage tank and three parts of the absorber tube have been evaluated using ANSYS FLUENT software in a three-dimensional and transient simulation. The results show that Case 8 has improved by 39.7% compared to Case 1 and Case 4 by 5.2% compared to Case 1 within 4 h of the melting process. Also, Case 8 with a 43% and 6.4% shorter melting time than Cases 1 and 5 has the best performance and the greatest heat transfer rate. The productivity of the ETCSWH system is considerably enhanced by the use of fins, NEPCM, and nanofluid. [ABSTRACT FROM AUTHOR]

Copyright of EMERG: Energy. Environment. Efficiency. Resources. Globalization is the property of Romanian National Committee of World Energy Council and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The present work experimentally evaluated the performance of a solar collector comprised evacuated tube heat pipe (ETHP) coupled with a compound parabolic concentrator at different tilt angles. Therefore, experiments have been conducted in the climate conditions of Tamil Nadu (77.07° E,11.04° N), India, from April 15, 2019, to May 20, 2019. The objective of the work is to explore the effect of a tilting angle on the performance of an evacuated tube solar collector with a thermosyphon attached to the compound parabolic concentrator. The CPC is designed with an aperture width of 343 mm, concentration ratio of 2.32, and aperture angle of 25.4°, improving the solar collector efficiency with the help of MATLAB Programming, which gets Coordinate points based on these coordinate points. CPC Profile is fabricated. The Thermosyphon heat pipe is constructed with a Copper tube having a 19 mm diameter with 40% Acetone charged. The experiments were conducted by varying the tilting angles of the solar collector at 15°, 30°, 45°, and 60° horizontal. The heat resistance and instantaneous efficiency of the solar collector are studied in this study. The result reveals a minimum thermal resistance of 0.02 kW−1, and a maximum efficiency of 78% was recorded at a 45° tilting angle. [ABSTRACT FROM AUTHOR]

The study presents a comprehensive thermal performance analysis of a U-pipe Evacuated Tube Solar Collector (U-ETSC) system, integrated with Phase Change Material (PCM), for satisfying water demand in domestic applications. The innovative approach of incorporating PCM aims to enhance the system's efficiency during night or off-sunny hours, addressing a common limitation in solar heater systems. The research primarily focuses on the impact of varying mass flow rates of the heat transfer fluid (HTF) on the thermal dynamics of the system. Experimental results reveal that as the mass flow rates of HTF increase from 0.5 to 1 and then to 1.5 liters per minute, there is a notable change in the phase transition times of the PCM. Specifically, the melting time of the PCM is increased by 13% and 16% for the respective flow rates, suggesting a delayed response in energy absorption. Conversely, the solidification time of the PCM is reduced by 16% and 18% respectively, indicating a faster release of stored thermal energy. This behavior underscores the PCM's significant role in stabilizing the system's thermal output during varying solar intensities. The findings of this study highlight the potential of integrating PCM in U-ETSC systems to achieve a more consistent and reliable supply of hot water for domestic purposes, especially during periods when solar irradiance is low or absent.

The aim of this research to assess the thermal performance of a locally developed two-phase closed thermosyphon system charged with methanol. The performance of the system is examined through experiments to determine the impact of changes in the electrical heat power, liquid charge, flow rate, inclination angle, and cooling water temperature on the output temperature. Temperatures at various points of the heat pipe, as well as cooling water, are recorded. Several fluid loadings are examined, ranging from 4 to 9 ml, which corresponds to the limits of the half full and overfilled evaporator. Different flow rates in the interval 0.2–0.7 kg/min, heat input in the interval 13.0–41.4 W, and cooling water temperature in the interval 15–35°C are considered. According to the findings, the ideal liquid fill ratio provides the best results in terms of the output temperature, and the heat transfer coefficient is between 64 and 71%. The impact of the adiabatic zone insulation on the temperature distribution along the heat pipe is illustrated. [ABSTRACT FROM AUTHOR]

• A compact solar collector was designed and optimized for integration with buildings. • Optical/thermal performances were analyzed through theory, simulation and experiment. • Annual optical and thermal efficiencies are 57.6 % and 30.6 % @ 250 °C, respectively. • The tilt angle within latitude ± 10.5° has little effect on the optical efficiency. • The efficiencies can improve by manufacturing accuracy, vacuum degree and emissivity. Process industry consumed 15 % to 30 % of the global energy, and 40 % of it is thermal energy demand in the range of 80 °C-250 °C. To produce mid-temperature heat, a new solar collector was designed with heat pipe evacuated tube, including several parallel micro-parabolic troughs, heat pipes, double-layer vacuum tubes contained in a compact frame and an external mechanical solar tracker. In addition, the selective absorbing coating (SAC) was applied on the inner surface of the vacuum tube, and the gap between the heat pipe and the vacuum tube was filled with heat transfer oil. Since the height of the designed collector was only 124.5 mm, it can be easily integrated with buildings. Genetic algorithm (GA) was used to optimize the structural parameters based on maximum obtained solar energy of the collector, and theoretical analysis and numerical simulation are carried out for optical and thermal performance of the collector. The analytical and numerical results showed that the annual average optical efficiency is 57.6 % and the thermal efficiency is 30.6 % at 250 °C when the normalized temperature difference is 0.23. By exergy analysis, the collector has a maximum exergy efficiency of 15.5 % with operating temperature of 204.4 °C, which is the station of the best thermal performance of the collector. Furthermore, theoretical model was verified to be valid by a prototype. Overall, the proposed collector is suitable for mid temperature industrial applications and integrated with rooftop. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Railway Science & Engineering is the property of Journal of Railway Science & Engineering Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Thermal solar collector considers one of the main devices employed to transform solar energy into thermal energy and can be classified into three main types named Evacuated tube collector (ETC), flat plate collector (FPC), and compound parabolic collector (CPC) collector. In this study, where it was taken to evacuated tube solar collectors three different geometries of the inner pipe diameter were proposed and combined with type of phase change materials (PCM) to evaluate their performance using PCM. And mass flow rate 0.5 L\min, A validated computational fluid dynamic (CFD) model was used in this examination. The data indicates that the highest outlet water temperature was observed at 45 °C from 1:00 pm to 2:00 pm for case-1 with a smooth pipe, whereas for case-2 with two lobes and case-3 with four lobes, the maximum temperatures were 41 °C and 40 °C. respectively, The results showed that case-1 with Paraffin wax has the best efficiency among the proposed cases. Where it was recorded maximum outlet water temperature was about 45 °C. [ABSTRACT FROM AUTHOR]

The compound parabolic concentrators (CPCs) are of importance due to their capability in absorbing the incident solar radiation in a wide limit. The present paper deals with the optical and thermodynamic analysis of a solar CPC applying the accurate solar ray-tracing analysis. To this end, the optical efficiency of the CPC was obtained for different geometric concentration ratios ( $C_t$) based on the CPC modified equations and considering the diffuse radiation effects. The results demonstrated that the highest solar radiation absorption is obtained for $C_t$ of 1.63. The outlet temperature ( $T_o$), energy and exergy efficiencies ( $\eta _I$ and $\eta _{II}$) of the stationary evacuated tube CPC were compared with those of two different evacuated tube solar collectors without a concentrator (with large or low distance between the tubes). Based on the results, the average incident solar radiation of the CPC collector is higher than that of two other solar collectors without a concentrator. Besides, $\eta _I$ of the CPC is higher than that of other collectors within the range of effective reflective angle of the CPC, while for the higher incident angles, $\eta _I$ is lower than or equal to the other two collectors without a concentrator.

The water shortage crisis has been paid attention to and many efforts have been conducted to find proper and applicable solutions to it through developing desalination systems. Commonly, being simple in construction and easy operation, solar stills (SSs) have been developed to meet the freshwater need; especially, in arid areas. However, their productivity and efficiency improvement are still a challenge. Accordingly, the current work aimed to enhance the thermo-economic performance of a pyramid SS (PSS) by augmenting the evaporation and condensation processes. For obtaining high vapor generation, evacuated tubes and ultrasonic foggers were integrated into the developed PSS (DPSS) as a first case (DPSS-I), in which different operation times of the foggers were tested. Then, Co 3 O 4 nanofluid (1.5 wt%) was added as a basin fluid in the second case (DPSS-II). Finally, in the third case (DPSS-III), a glass cooling was used for boosting the condensation rate. Besides the experiments, a complete thermo-economic performance analysis was done via calculating the energetic and exergetic efficiencies and freshwater cost (per liter). All these performance indicators of DPSS were compared to that of traditional PSS (TPSS). As resulted, integrating all the proposed additives (DPSS-III) could enhance freshwater production, energy efficiency, and exergy efficiency by 83.87%, 18.29% and 38.86%, respectively. Additionally, the production cost, per freshwater liter, was reduced by 11.61%. These results showed the applicability, sustainability, and feasibility of the proposed additives in the field of solar desalination, particularly SSs. [Display omitted] [ABSTRACT FROM AUTHOR]

Evacuated tube collectors can achieve a much high efficiency and temperature for a much longer period compared to conventional single flat plate collector systems. However, they can be a lot more expensive compared to flat panel collectors. Hence, the building of a suitable model would make the analysis of the configuration of the systems more insightful to achieve higher efficiencies. In this paper, a thermal resistance network model of an evacuated tube heat pipe was developed. An analysis of its performance was done to understand the effect of adding an I-section geometry insert on the total thermal resistance, the heat transfer and the efficiency considering several working fluids such as water, ethanol, methanol, acetone and toluene. The proposed model was validated using data collected on a cloudy day from the SAURAN STATION located in UMLAZI, SOUTH AFRICA. This study reveals that the addition of an insert decreases the total thermal resistance, which results in improved efficiencies. Water exhibited higher efficiency compared to other working fluids with the efficiency of 62.24% and 54.27% corresponding to the configuration with and without a geometry insert. An improvement in the rate of heat transfer from 530 to 605 KW when introducing an insert into the heat pipe was observed. Interestingly, the solar collector exhibited better results, even on a cloudy day. The thermal resistance network model proposed in this paper was deemed appropriate to be used for the performance prediction of the heat pipe with an insert. [ABSTRACT FROM AUTHOR]

Solar technologies are an efficient means of addressing environmental pollution and climate change challenges. In this study, an organic Rankine cycle (ORC) system driven by solar evacuated glass tubes named solar water power generation (SWPG) system was experimentally investigated to explore the performance of the SWPG system in powering buildings. For ORC, a new mixture called TD-3 was introduced for the experiment after comparing the thermodynamic characteristics of five working fluids using refprop software. The solar radiation intensity was simulated for solar collectors to determine the best installation angle of the evacuated glass tubes to be 30 deg in Tianjin, China. The power generating efficiency was tested as high as 4.5% at 1:00 pm on July 15. The optimization of operating parameters and the modification of generating equipment contributed to the increase in power generation. The SWPG system could achieve an optimal power output when the system guaranteed a small superheat and no more than 3 °C subcooling using the TD-3. The transmission ratio between the generator and expander also impacted power generation that the ratio of 2:1 helped optimize the power generation. [ABSTRACT FROM AUTHOR]

Copyright of Eastern-European Journal of Enterprise Technologies is the property of PC TECHNOLOGY CENTER and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This study aims to numerically assess the heat transfer performance of water-in-glass evacuated tube solar water heater (WGET-SWH) for various parameters. It is observed that the natural circulation flowrate, velocity, and temperature distribution are strongly dependent on WGET-SWH geometry and operating conditions. The natural circulation flowrate is found to be increasing with tube length, diameter, inclination angle, and circumferential heat input. However, the heat transfer rate decreases with an increase in aspect ratio. The average Nusselt number increases with an increase in inclination angle till 45 deg and then decreases. Also, the study shows that thermal stratification in reservoir fluid is greatly influenced by circulation flowrate, flow momentum, collector outlet temperature, thermal acceleration, and buoyancy effect. [ABSTRACT FROM AUTHOR]

Copyright of SDU Journal of Engineering Sciences & Design / Mühendislik Bilimleri ve Tasarım Dergisi is the property of Journal of Engineering Sciences & Design and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The evacuated U-pipe solar thermal collector is one of the most promising and efficient solar thermal collectors exploited for solar thermal applications. TiN nanofluid charged evacuated U-pipe solar thermal collector convective heat transfer performance, pressure drop, and efficiency measured experimentally. TiN nanoparticles of 40–50 nm size are suspended in distilled water at a volume concentration of 0, 0.025, 0.050, 0.075, and 0.1% to prepare nanofluid. The stability and thermophysical properties of the TiN nanofluid were measured experimentally. The outdoor experiments were performed at latitudes of 19.5761 deg N and 74.2070 deg E with and without twisted tape (H/D = 5) at a mass flow rate of 0.25–1.25 LPM and volume concentration of 0.0–0.1%. The ASHRAE Standard 93-2003 is used to evaluate collector thermal performance. The 0.1% TiN nanofluid and twisted tape (H/D = 5) combination give a 942.99% convective heat transfer coefficient enhancement at a 1.25 LPM flow rate compared with water at a 0.25 LPM flow rate. Under the same operating conditions, the pressure drop shows a 763.16% enhancement. TiN nanofluid-charged solar thermal collector efficiency reaches 98.66 and 71.53% at 0.1% volume concentration with and without twisted tape combinations, respectively. [ABSTRACT FROM AUTHOR]

This article focuses on the thermal performance testing of evacuated tube solar collectors with heat pipes (ETC-HP) using the ISO 9806:2017 standard test methods: Steady-state testing (SST) and Quasi-dynamic testing (QDT). The main objective of this work is to improve the experimental estimation of the incident angle modifier (IAM) for these types of solar collectors in both test methods. For the QDT method, a novel model for the IAM is presented and validated against SST results. This IAM model, recently developed for flat plate collectors under the SST framework, has demonstrated superior performance compared to other available models. This study marks its first application to ETC-HP technology, showcasing its adaptability across different technologies and test methods. While this work primarily focuses on ETC-HP collectors, the results are applicable to evacuated tubes in general. Thus, the generality of this model and its consistency with the SST method make it suitable for implementation in test standards as a general-purpose model. Regarding the SST method, and aiming to enhance consistency between testing methods, an improved parameter conversion from SST to QDT is also proposed, reducing IAM differences between test methods by 1 to 19 percentage points, with greater improvement at higher incidence angles. • A novel incident angle modifier is implemented for QDT testing of ETC. • A novel parameter conversion is proposed which improves SST and QDT coherence. • Data averaging time for QDT is analyzed and the optimal value is identified. • Guidelines are introduced to enhance the extension of QDT method for ETC. • A constrained nonlinear algorithm for QDT parameter identification is introduced. [ABSTRACT FROM AUTHOR]

This paper studies the improvement of an evacuated tube solar collectors(ETSCs) performance in two way. The first is by adding a finned electronic curtain in front of the solar collector. While the second is by using a nanofluid instead of pure water. The purpose of the curtain is to increase the amount of solar radiation reflected toward the collector. The curtain is distinguished by its self-ability to track the sun's rays automatically. The electronic curtain is also closed to shade the tubes depending on the movement of the electronic curtain's fins and the nanofluid's temperatures. MATLAB algorithm has been used to design the Simulink model and control the system using Fuzzy Logic Control (FLC) and Artificial Neural Network (ANN). The results showed that the system performance improved using TiO2(50nm)+PW) as a working fluid without the curtain are (3.906%,5.34%, and7.407%), while the rate of improvement in the case of distilled water only was 2.34%and3.81%. Finally, by adding the finned electronic curtain to the system and use of TiO2(50nm)+PW) as a working fluid, the efficiency increased by 7.03%,9.16%, and 11.89%. The results showed that the performance of evacuated tubes solar collectors increased by using a nanofluid and the finned electronic curtain.

A solar dryer was developed using an evacuated tube solar thermal collector and solar photovoltaic (SPV) panel to supply the electrical energy. Paraffin wax was packed in a well-sealed aluminum package and stored in the bottom of the drying chamber near the entrance of hot air enabling recharge and store thermal energy. A DC fan was used to supply hot air to the drying chamber. The chamber was made of locally available material with glass wool as insulation. The overall dimensions were 0.6 m × 0.55 m × 1.05 m with 7.0 trays having 0.25 m2 per tray. The capacity of the dryer is 5.0 kg. The maximum temperature that could attain inside the drying chamber during clear sunny days was 45 to 60ºC. The efficiency of the dryer is 27%.

Nanofluids have numerous applications in heat transference procedures due to their exceptional thermal characteristics. The most desirable parameter to enhance the solar collector's performance is the enhancement of the convective heat transfer coefficient between the working fluid tubes and the absorber. As a result, nanofluids have gained prominence as working fluids in solar thermal systems. The trendsetting review reveals that mostly the nanofluids in solar collectors are based on water employing nanoparticles of Al2O3, TiO2, SiO2, and CuO. Besides, nanoparticle concentration is a challenging factor in using nanofluids. In this research, under controlled conditions, the working fluids multi-wall carbon nanotube, Aluminum Oxide, and hybrid MWCNT/Al2O3 50:50% were experimentally examined for the thermal efficiency enhancement of the evacuated tube solar collector. For each type of nanofluid, four volume concentration percentages (0.5%, 0.025%, 0.01%, and 0.005%) were examined along with three distinct mass flow rates. According to the findings, using hybrid MWCNT/Al2O3 50:50% delivers an efficiency boost of about 20% overusing Al2O3, as was previously reported. Finally, it was found that the utilization of 0.5% MWCNT/water nanofluid at 3.5 L/m can enhance the ETSC's energy and exergy efficiency to reach 73.5% and 51% respectively while reaching approximately 60% and 44% for AL2O3, and 69% and 38% for hybrid MWCNT/Al2O3 (50:50%) under the same test conditions.

In the reported study, a dynamic analytical model is developed to propose the energy, exergy, environmental impact, and economic analyses of the water heating system at Jaipur (India) with an evacuated tube compound parabolic concentrator field of a total area of 81 m2. Consequently, the model is used to perform parametric studies to report the effect of operating and meteorological parameters on the productivity and performance of the system. Moreover, the system's performance, environmental impact, and economic aspects have been investigated and compared under different meteorological conditions at four different Rajasthan (India) locations using TMY2 weather data files. Results clarified that Jodhpur receives the highest solar radiation intensity from these four locations. The model results were validated with the experimental data, and a good agreement has prevailed. Consequently, the results indicate the highest annual energy and exergy gain for Jodhpur with 79.72 MWh and 9.311 MWh, respectively, followed by Jaisalmer, Barmer, and Jaipur. The economic analysis results clarified that the simple payback period ranged from 4.5 to 4.75 years and the discounted payback period ranged from 6.6 to 7 years based on a 6% discount rate. At the same time, the levelized cost of heating for the given system is around 0.023 $/kWh which is very economical closest to that of CNG as a fuel which costs around 0.059 $/kWh. The internal rate of return is reported to be 16.76, 16.82, 16.77, and 16.75% for Barmer, Jodhpur, Jaipur, and Jaisalmer, respectively, and savings of 74.4, 78.1, 75.4, and 73.8 tonnes of CO2 emission to the environment. [ABSTRACT FROM AUTHOR]

The compound parabolic concentrators (CPCs) are of importance due to their capability in absorbing the incident solar radiation in a wide limit. The present paper deals with the optical and thermodynamic analysis of a solar CPC applying the accurate solar ray-tracing analysis. To this end, the optical efficiency of the CPC was obtained for different geometric concentration ratios ( C t ) based on the CPC modified equations and considering the diffuse radiation effects. The results demonstrated that the highest solar radiation absorption is obtained for C t of 1.63. The outlet temperature ( T o ), energy and exergy efficiencies ( η I and η I I ) of the stationary evacuated tube CPC were compared with those of two different evacuated tube solar collectors without a concentrator (with large or low distance between the tubes). Based on the results, the average incident solar radiation of the CPC collector is higher than that of two other solar collectors without a concentrator. Besides, η I of the CPC is higher than that of other collectors within the range of effective reflective angle of the CPC, while for the higher incident angles, η I is lower than or equal to the other two collectors without a concentrator. [ABSTRACT FROM AUTHOR]

In this research, a practical study and appraisal of the thermal performance for the solar collector with vacuum tube has conducted Two types of nanomaterials (aluminum and aluminum oxide) have added to distilled water with nanoparticles diameters of 30 nm and 50 nm respectively. The nanomaterials were used in three several concentrations and three several flow rates which used as a working fluid in evacuated tube solar collector (ETSC) in order to increase the efficiency and beneficial thermal gain. An electronic double-sided reflective and absorbent electronic curtain were added to enhance the performance and control the temperature of the nanoscale. A clear improvement in efficiency was observed when using the reflective curtain that helped to speed up the Nano fluid heating and controlling the required temperature.

The issue of freshwater shortage is a general problem that touches almost all human beings, and everyone is trying to find creative and practical solutions to try to overcome this problem. In this paper, the proposed desalination system consists of a modified solar still (MSS), parabolic trough solar collector (PTSC), separation unit (SU), and two external condensers (EC). The idea of this proposed device is that the PTSC was utilized to heat the saline feed water to a temperature from which steam can be extracted, and then a separation is made for this steam from the remaining water that has risen in temperature and has not been evaporated to be used as feed water for MSS. Also, MSS has been modified by making all its walls (except for the back wall of the distiller) of glass to obtain a greater amount of absorbed solar radiation. Besides, a double glass cover for MSS was used instead of the single glass sheet to prevent the heat loss to the atmosphere through the glass cover. The double glass cover is two sheets of glass between which there is a slight vacuum pressure. Regarding the experimental tests conducted through July 2021, the main conclusions of this work can be pointed. It was revealed that at 12:00, the maximum water temperature of PTSC was 55 °C at 20 L/hr (0.33 L/min), where the solar radiation was 1050 W/m². Besides, the effectiveness of PTSC was 60%, and the total accumulated productivity of PTSC was 83 L/daytime (daytime = 9 hrs). Moreover, the total accumulated productivities of conventional solar still (CSS) and MSS with double glass cover were 3330 and 2325 mL/m².daytime, respectively. Therefore, the productivity of MSS with double glass cover was smaller than that of the CSS by about 30%. In addition, the total accumulated freshwater distillate of CSS and MSS with double glass and condenser was 3370 mL/m².daytime and 6150 mL/m².daytime, respectively. As a consequence, the productivity of MSS with double glass and condenser was more than that of CSS by around 82.50%. In addition, the thermal and exergy efficiencies were 31% and 2.54%, respectively for CSS and 47.5% and 3.95%, respectively for MSS with double glass and condenser. Besides, the total productivity of the hybrid system (PTSC and MSS together) was reported as 91.0 L/daytime. Also, the cost of distilled water of proposed hybrid system is 0.008 $/L, and payback period of costs on proposed system is three months. Moreover, the environmental parameters of EPF, ϕ C O 2 , and Z ′ for MSS are slightly more than the double of that for CSS. [ABSTRACT FROM AUTHOR]

Solar water heating (SWH) systems becomes increasingly popular in modern buildings, due to significant reduction in energy consumption in heating applications. In this work, an active SWH is modeled using TRNSYS software for climatic conditions of Chennai, India, employing an external compound parabolic concentrator solar collector and stratified thermal storage system (STESS). The performance parameters are estimated on the basis of monthly and annual averaged solar fractions (SF) by varying the collector area, mass flow rate, various controller strategies, and STESS geometry. The simulated studies have specified the ability of the optimized system to supply the hot water demand of 280 L d−1 at 60°C, attaining a SF of 0.97. This design strategy can be implemented for the development of an efficient SWH system, utilizing zero energy consumption from conventional resources. The proposed TRNSYS model has been validated using experimental data under similar test conditions. An influence of placing XCPC under evacuated tubes is simulated, resulting 5% improvement in energy gained over an evacuated tube solar collector without XCPC. [ABSTRACT FROM AUTHOR]

The evacuated tube solar collector is considered an efficient, convenient, and economical option used to convert solar energy into heat. In this work, enhancement of evacuated tubes solar collector performance and the potential for energy storage by using Al2O3 water-based nanofluid embedded in Graphite as a saturated porous media was presented and studied theoretically. The Governing equations derived from the principles of conservation of mass, momentum, and energy were written in a dimensionless form, and solved these equations analytically for the fully developed region, and numerically throughout the entrance region, and the heat flux data for Amman, Jordan was used in this study. The analysis of the effect of different parameters as porosity, pore diameter, nanoparticles solid volume fraction, pressure, and radius of conduit on temperature variation through the pipe and Nusselt number was done. The results show that the flow of nanofluid in porous media enhances the evacuated tube's performance compared to just using water in the same medium under the same conditions. In August, the temperature variation in the evacuated tube at the same condition for Al2O3 water-based nanofluid for 1.5% volume fraction reach 42 ℃ and 73 ℃ for 6% volume fraction. In contrast, In January for the 1.5% volume fraction the temperature variation reached 25 ℃ and 43 ℃ for 6% volume fraction. On the other hand, the stored energy approximately reached 30 kJ/kg and 45 kJ/kg for solid volume fraction 1.5% and 6% respectively at the same conditions

Evacuated tubes are extensively utilized for converting solar energy into thermal energy owing to their exceptional thermal properties and affordability. The circumferential temperature gradient of the evacuated tube is significant to the heat and mass transfer inside, but it is often neglected. This research proposed an improved model incorporating non-uniform heat flux and circumferential conduction to obtain the temperature distribution. In the experiment, A thermal insulation material was inserted inside the inner tube to create an adiabatic boundary. Various conditions (non-uniform, rectangular, and uniform heat fluxes, circumferential conduction of the coating) were numerically compared. The enhanced combined thermal transmission model was validated, demonstrating a relative error of 6.45 % in temperature increase calculation and increasing the prediction accuracy by 42.15 % at least. The distribution of the heat flux and the thermal conduction of the coating were identified as the primary factors affecting the heat transfer properties of the evacuated tube. An imbalanced distribution of heat flux resulted in non-uniform heat transfer, whereas the circumferential conduction within the coating effectively modulated the temperature distribution to achieve uniformity. The local heat transfer coefficient exhibited non-uniformity, with calculated values ranging from 0.23 to 3.25 W/(m2∙K), and an error range of −16 to +3 %. • A theoretical model incorporating circumferential conduction was developed. • The non-uniform heat transfer model exhibits the minimum RE avg (6.45 %) in dT. • An imbalanced distribution of heat flux results in non-uniform heat transfer. • The circumferential conduction modulates the temperature distribution to achieve uniformity. • The local heat transfer coefficient exhibits non-uniformity but the value is small. [ABSTRACT FROM AUTHOR]

The core aim of this investigation is to simulate the melting of paraffin within a solar heat pipe unit combined with thermal storage unit, while taking into account the presence of metallic fins. To enhance system performance, Multi-Walled Carbon Nanotube (MWCNT) nanoparticles were blended into the paraffin material (RT82) using a homogeneous mixture approximation. The temperatures of the heat pipe and inner walls were derived from previous experimental research. Three distinct fin arrangements were utilized, and simulations were carried out employing numerical method. Validation procedures were undertaken to verify the accuracy of the modeling and the applied approximations, relying on both prior experimental data and numerical publications. The investigation presents data on the liquid fraction (LF), temperature (T), and stream function for diverse configurations. This holistic approach seeks to deepen comprehension of the interactions among these elements within a solar collector system, offering vital insights for performance optimization. The outcomes demonstrated a notable improvement in LF, increasing by roughly 15.15% at t = 1200s with the integration of MWCNT. Furthermore, with the passage of time from 400 s to 1200s, the incorporation of additives results in a notable rise in LF and T, demonstrating enhancements of approximately 97.74% and 130.8% correspondingly. Notably, the utilization of fins positioned at a 90o angle expedites the melting process, yielding a 38.24% LF increase compared to the base case at t = 1200s. Moreover, the impact of fins demonstrates a 3.32% increase over time. In essence, these results emphasize the effectiveness of incorporating MWCNTs and fine-tuning fin configurations to accelerate the melting process, offering valuable insights for the progress of solar thermal systems. • Solar heat pipe system combined with thermal storage unit was investigated. • To enhance system performance, MWCNT nanoparticles were blended into the paraffin. • Improvement in LF, increasing by 15.15% at t = 1200s with adding MWCNT. • The impact of fins demonstrates a 3.32% increase over time. • Utilization of fin-90o expedites the melting about 38.24%. [ABSTRACT FROM AUTHOR]

Energy consumption is steadily increasing with the ever-growing population, leading to a rise in global warming. Building energy consumption is one of the major sources of global warming, which can be controlled with renewable energy installations. This paper deals with an advanced evacuated hybrid solar photovoltaic–thermal collector (PVT) for simultaneous production of electricity and domestic hot water (DHW) with lower carbon emissions. Most PVT projects focus on increasing electricity production by cooling the photovoltaic (PV). However, in this research, increasing thermal efficiency is investigated through vacuum glass tube encapsulation. The required area for conventional unglazed PVT systems varies between 1.6–2 times of solar thermal collectors for similar thermal output. In the case of encapsulation, the required area can decrease by minimizing convective losses from the system. Surprisingly, the electrical efficiency was not decreased by encapsulating the PVT system. The performance of evacuated PVT is compared to glazed and unglazed PVTs, and the result shows a 40% increase in thermal performance with the proposed system. All three systems are simulated in ANSYS 18.1 (Canonsburg, PA, USA) at different mass flow rates and solar irradiance. [ABSTRACT FROM AUTHOR]

The present study represents theoretical and applied experimental test to advise new configuration of split air conditioning unit with compressor energy saving. The conventional cycle that consists of evaporator, compressor, condenser and expansion valve was set as the base cycle. Three cases will be investigated theoretically; conventional, conventional with partial compression in the compressor with compression completion via evacuated tube and conventional with partial compression in the compressor with compression completion via evacuated tube in the presence of heat exchanger. Five refrigerants are tested theoretically, R- 134a, R-152a, R-290, R-600a and R-1234yf; however the experimental test rig is tested with only R- 134a which is available. The results include cooling capacity, compressor power, condenser heat load and the cycle coefficient of performance (COP).‏ Good performance of the new ‏proposed system ‏with partial compression in the compressor with compression completion via the evacuated tube in the presence of heat exchanger has been found. The results showed that the utilization of evacuated tube with heat exchanger leads to maximum enhancement in system COP by 20.3% in case of using R-290 as a result of consumed power reduction in the compressor by 8.22% and increasing in the cooling capacity by 10.1%. • Air conditioning system utilizing evacuated tube and heat exchanger is introduced. •The new configuration saves the compression power up to 8.22%. •The COP is enhanced up to 20.3% due to an increase in cooling capacity by 10.1%. [ABSTRACT FROM AUTHOR]

In this study, the design, development, and performance analysis of novel thermal energy storage integrated evacuated tube heat pipe solar dryer was investigated. A new common condenser heat pipe system having thermal energy storage was incorporated into the solar collector of the dryer. Therminol 55 was used as the thermal storage medium. The performance analysis was carried out with air mass flow rates between 0.003 kg/s to 0.02 kg/s and a combination of two mass flow rates 0.015 kg/s and 0.0065 kg/s. The maximum outlet temperature of the air delivered by the solar collector during the study was 118 °C. The average energy and exergy efficiency of the solar collector varied between 10%-30% and 1.9%-5.6% respectively. Agricultural products like tomatoes and carrots were dried in the dryer. The effect of moisture diffusivity variation for tomatoes and carrots with the mass flow rate of air and product thickness was analyzed in this study. The Newton model fairly demonstrated the solar drying characteristics of tomatoes. The combined mass flow rate method increased the average collector outlet temperature to 67 °C against 56 °C during a single mass flow rate and decreased the drying time by 2 h. The payback period for the dryer was 2.6 years. [Display omitted] • Novel thermal storage integrated evacuated tube heat pipe based solar dryer. • Suitable for drying applications with wide range of temperatures. • A new common condenser heat pipe arrangement for thermal storage. • High-temperature air was obtained even during off sunshine hours. • The solar dryer is an economic and environment-friendly one. [ABSTRACT FROM AUTHOR]

• Performance analysis of novel hybrid greenhouse dryer attached with evacuated tube collector. • New model for predicting the moisture ratio of crop drying inside the solar dryers. • Evaluation of convective and evaporative heat transfer coefficients for three cases. • Drying behavior analysis of tomato, ginger and bottle gourd for three cases. The objective of the paper is to carry out the heat transfer analysis of novel designed hybrid active greenhouse solar dryer (HAGSD) attached with water-in-tube type evacuated collector. The experimentation is carried out to investigate the performance of dryer with and without evacuated tube collector (ETC) under active mode. Three high moisture seasonal crops namely tomato, ginger and bottle gourd have been dried inside the dryer for the two cases and also in open sun drying. Also the drying kinetic of crops has been fitted with ten drying rate models given by researchers. A new drying rate model is also obtained which gives a very close fit with experimental drying rate. The average values of convective heat transfer coefficients for dryer with ETC are 153%, 3.8% and 305.4% higher than the dryer without ETC for tomato, ginger and bottle gourd respectively. The drying time in case of dryer with ETC for tomato, ginger and bottle gourd is 9, 12 and 6 h respectively less than the dryer without ETC. The overall efficiency of the dryer for the three crops varies between 14.22 and 27.99% for dryer with ETC, while for dryer without ETC, it varies between 9.63 and 24.88%. [ABSTRACT FROM AUTHOR]

The evacuated tube solar collector is considered an efficient, convenient, and economical option used to convert solar energy into heat. In this work, enhancement of evacuated tubes solar collector performance and the potential for energy storage by using Al2O3 water-based nanofluid embedded in Graphite as a saturated porous media was presented and studied theoretically. The Governing equations derived from the principles of conservation of mass, momentum, and energy were written in a dimensionless form, and solved these equations analytically for the fully developed region, and numerically throughout the entrance region, and the heat flux data for Amman, Jordan was used in this study. The analysis of the effect of different parameters as porosity, pore diameter, nanoparticles solid volume fraction, pressure, and radius of conduit on temperature variation through the pipe and Nusselt number was done. The results show that the flow of nanofluid in porous media enhances the evacuated tube's performance compared to just using water in the same medium under the same conditions. In August, the temperature variation in the evacuated tube at the same condition for Al2O3 water-based nanofluid for 1.5% volume fraction reach 42° and 73° for 6% volume fraction. In contrast, In January for the 1.5% volume fraction the temperature variation reached 25° and 43° for 6% volume fraction. On the other hand, the stored energy approximately reached 30 kJ/kg and 45 kJ/kg for solid volume fraction 1.5% and 6% respectively at the same conditions. [ABSTRACT FROM AUTHOR]

In this study, the current research delves into the influence of nanoparticle size on turbulent forced convective heat transfer, entropy generation, and friction factor. The investigation focused on three different sizes (30 nm, 50 nm, and 80 nm) of Al 2 O 3 nanoparticles (NPs) suspended in a water-based nanofluid (NF) with a 1 vol% concentration flow in a circular tube. The nanoparticles (NPs) were characterized using various characterization techniques. The stability and pH of the NF were determined, and its viscosity (VST) and thermal conductivity (TC) were measured at a temperature of 60 °C. Heat transfer experiments were conducted with varying particle sizes and Reynolds number (Re), maintaining a fluid inlet temperature of 60 °C. The results indicated that the NF containing 30 nm particles exhibited higher VST and TC compared to the other samples and the base fluid. The maximum enhancement in Nu for Al 2 O 3 (30 nm) and Al 2 O 3 (80 nm) NFs is 60.7 and 18.5 % greater than that of base fluid, respectively. The maximum and minimum total entropy generation (S gen , T ) value of 0.499 and 0.286 observed for base fluid and Al 2 O 3 NF (30 nm), respectively at low Re. The highest friction factor enhancement for Al 2 O 3 NF (30 nm) exceeded by 9.4 % compared to the base fluid, and the maximum thermal performance factor observed for Al 2 O 3 NF (30 nm) was 1.57. Finally, regression analysis was employed to establish correlations for estimating Nu and friction factor values. Prognostic models were developed using two sophisticated machine learning algorithms, XGBoost and Gradient Boosting Regression (GBR). Both models demonstrated exceptional prediction abilities, achieving over 99 % accuracy rates based on the experimental data. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel thermal storage integrated evacuated tube heat pipe solar air heater. • Suitable for high temperature air heating applications. • A new common condenser heat pipe arrangement was introduced in the system. • High temperature air was obtained during off sunshine hours. • This new solar air heater is an efficient and environment friendly device. This study aims to present a novel thermal energy storage integrated evacuated tube heat pipe solar air heater suitable for high-temperature applications. A new heat pipe arrangement was introduced in this study by attaching all the evaporator tubes of heat pipes to a common condenser section. A thermal energy storage medium was kept in a chamber within the common condenser unit of the heat pipe to obtain uniform outlet air temperature from the system when there is fluctuation in solar radiation. Therminol 55 was used as the sensible heat storage medium in the system. The Performance evaluation of the system was conducted by varying four airflow rates 0.03 kg/s, 0.1 kg/s, 0.2 kg/s and 0.3 kg/s, respectively. 0.03 kg/s resulted in a maximum outlet air temperature of 128 °C and the system delivered more than 100 °C of hot air until 10 h of operation. The maximum thermal and exergy efficiency obtained during each airflow rate was 38%, 77%, 85%, 89%, and 5.01%, 5.21%, 5.34%, and 5.76% respectively. An average of 6200 kJ energy was collected by the present system during its operation. The total money saved per month during the operation of TS-ETHPSD was 445 INR. The Payback Period for the system is 69 months. The solar air heater can be considered as an environment-friendly device as it can save 73 kg/month of Co 2 from entering the atmosphere. [ABSTRACT FROM AUTHOR]

This study deals with the design and fabrication of parabolic trough solar collectors (PTCs) used to increase the yield of a single slope solar still. The designed parabolic trough solar collector is investigated numerically using Ansys Fluent 18.2. The proposed solar still is coupled with a parabolic trough solar collector with an evacuated tube receiver in its focal axis using different working fluids. The working fluids are water (case 1), oil (case 2), and nano‐oil (CuO/mineral oil 3% vol; case 3). In the case when the working fluid is not water, then a heat exchanger serpentine should be used in the solar still basin. The PTC has a rim angle of 82° and an aperture width of 0.9 m and length of 2.8 m. An assessment of the performance for the studied systems was accomplished under the weather conditions of Ismailia, Egypt, during summer months, June, July, and August 2019. The outcomes of closed‐loop working fluids different flow rates are investigated. The experimental results of the accumulated freshwater productivities record 2.955, 3.475, 4.29, and 5.04 L m−2 d−1 for the traditional solar still and the modified cases 1 to 3 solar stills, respectively. The modified solar still in case 3 has the highest daily accumulated freshwater productivity with a percentage increase of 71.2% than the traditional solar still. The maximum daily efficiency is 46% and 26.9% for the traditional and modified (case 3) solar stills, respectively. The cost of 1 L of fresh water is 0.057 and 0.062 $/L for the traditional and the modified (case 3) solar stills, respectively. [ABSTRACT FROM AUTHOR]