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The presence of emerging contaminants in wastewater like tetracycline poses a significant challenge in water reuse worldwide. The implementation of a p-n heterojunction and dye-sensitized techniques in the enhancement of graphite carbon nitride provides a promising alternative for visible light-driven degradation of emerging contaminants present in wastewater. The present study investigated dye-sensitized and plain composites in degrading tetracycline using natural sunlight in a parabolic trough reactor. The study synthesized four composites of ZnFe2O4-g-C3N4 at 5, 15, and 25 wt% loading of the ferrite by direct annealing of melamine, followed by thermal and ultrasonic exfoliation of bulk graphite carbon nitride and in situ precipitation with zinc ferrites to yield a composite photocatalyst. The photocatalysts were characterized using X-ray diffraction (XRD) analyses which confirmed that all the spinel ferrite phases of ZnFe2O4 were well bonded with g-C3N4 nanosheets to form a composite. The crystallite sizes were calculated by the Debye–Scherrer equation indicating crystal sizes of between 4.63 and 8.61 nm confirming the nanostructures. The scanning electron microscope-energy dispersive spectroscopy (SEM-EDX) tests verified that the spherical globules of ZnFe2O4 were well attached to the mesoporous layers of g-C3N4 and absence of contaminant phases. The UV-Vis analysis for 25% ZF-GCN revealed a band gap reduction from 2.67 eV to 2.03 eV. The PL intensity for all the composites decreased at excitation of 266 nm and 550 nm which was evidence for suppressed charge recombination. A 25% ferrite loading resulted in the best photocatalytic performance with tetracycline degradation of 93.64% and total organic carbon (TOC) removal of 51.89%. The sensitization of the 25% ZF-GCN composite with Eosin Y further improved its performance for degradation of tetracycline to 94.62% and TOC removal to 68.29%. Therefore, dye sensitization is an efficient way of improving the photocatalytic activity of a multicomponent photocatalyst for the removal of emerging pollutants. [ABSTRACT FROM AUTHOR]

Competition between concentrated solar power and solar photovoltaic has been the subject of frequent debate in recent years based on their cost of fabrication, efficiency, storage, levelized cost of energy, reliability, and complexity of respective technologies. Taking Pakistan as a testbed, a study was conducted to determine which technology is economical in a particular location and climate. The study assesses the meteorological, orographic, and spatial factors that impact the performance and cost of both renewable energy systems. A SWOT analysis, followed by technoeconomic analyses, was conducted to determine suitable sites for setting up solar power plants in Pakistan. A detailed assessment of siting factors for solar power plants was conducted to shortlist the most suitable sites. Based on the results, economic analysis was performed to install 100 MW photovoltaic and parabolic trough power plants at selected locations. The levelized cost of energy for the 100 MW parabolic trough is 10.8 cents/kWh and 12 cents/kWh in best-case scenarios, i.e., for locations of Toba and Quetta, respectively, whereas the LCOEs of 100 MW photovoltaic systems stand comparatively low at 7.36 cents/kWh, 7.21 cents/kWh, 7.01 cents/kWh, 6.82 cents/kWh, 6.02 cents/kWh, and 5.95 cents/kWh in Multan, Bahawalpur, Rahim Yar Khan, Hyderabad, Quetta, and Toba, respectively. The results favor choosing solar PV plants over solar CSP plants in terms of finances in the selected regions. The findings will assist financiers and policymakers in creating better policies in terms of long-term goals. [ABSTRACT FROM AUTHOR]

The present study was conducted to design and develop the solar hybrid essential oil extraction system from turmeric at Department of Processing and Food Engineering, PAU, Ludhiana, Punjab. The developed system has six solar parabolic trough concentrator, steam generation unit, steam distillation unit, condensing unit and essential oil separator. A prototype of solar hybrid essential oil extraction system of 10 kg was designed and developed. The volume of steam distillation unit was 0.061m3 and volume of steam generation was 0.057 m3. The essential oil was extracted by using three turmeric grates size that is, 14.50 mm, 15.620 mm and 17.53 mm size. The smallest particle size (14.50 mm) having the highest essential oil yield (45 ml/kg) obtained from turmeric grates (P2, L42). The developed system was supplied additional 2 kW energy to extract oil from the turmeric grates. The results obtained from the study indicated that smallest grates size (14.50 mm) has the highest oil yield as compared to the largest grates size (17.53 mm). The steam generation and steam distillation unit has efficiency of 60 and 55.17%, respectively while the condensing unit having the efficiency of the 47.22%. The solar parabolic trough concentrators ensured energy saving of 21.53% and required 6.20 h extraction time. Developed system can be effectively helps in energy saving, reduced time required for oil extraction which makes the system more economical. Novelty impact statement: In the developed solar hybrid essential oil extraction system, the oil extraction was performed by the steam diffusion mechanism, as there is no such technology available for the essential oil extraction through the steam diffusion from turmeric. The developed hybrid system ensures 21.53% saving of electrical energy and 17.33% saving of the overall extraction time for the essential oils from turmeric grates. It can be installed and operated on a rooftop, so no additional space is needed. The developed system act as a tool for the generation of the extra income for the farmers in term of value addition. [ABSTRACT FROM AUTHOR]

The primary heat source from the sunlight is solar energy, which is used in photovoltaic panels, solar power plates, photovoltaic streetlights, and solar-based hybrid nanocomposites. A hybrid nanofluid is traversing an expanding sheet in this investigation. Maxwell fluid stream with two nanoparticles is going towards a trough with a parabolic form and is situated within the solar aircraft wing to investigate the phenomena of heat transfer rate. The term solar thermal radiation was introduced to describe heat transfer occurrence. The effectiveness of heat transmission from airplane wings is assessed by taking into account unique phenomena such as magnetic field and heat source. The bvp4c procedure was applied to quantitatively explain the energy and motion equations with MATLAB software. The copper (Cu) and graphene oxide (GO) nanosolid particles are mixed with sodium alginate (SA), a common liquid, to form the nanosolid particles. Numerous control variables are thoroughly examined, including temperature, shear stress, motion, friction component, and Nusselt number. The skin-friction coefficient upsurges with a growing magnetic impression. The upsurge in Deborah number reduces the skin-friction coefficient. The heat source impression declines the heat transport rate but upsurges the skin-friction coefficient. The skin-friction coefficient and heat transport rate increase with growing magnetic impression. When it comes to heat transfer analysis, hybrid nanofluid efficiency is substantially superior to that of regular nanofluid. [ABSTRACT FROM AUTHOR]

Summary: This study considers three parabolic trough collector models with rotating receiver tubes and elliptical inserts of two orientations and one with a smooth receiver tube. Hybrid nanofluid is considered as a working medium by mixing copper oxide and aluminum oxide nanoparticles in water. Computational experiments are performed with a 1% concentration in terms of vol. of hybrid nanofluids by considering a mixture of copper oxide and aluminum oxide nanoparticles in water (aluminum oxide 25%‐ copper oxide 75%, aluminum oxide 50%‐ copper oxide 50%, and aluminum oxide 75%‐ copper oxide 25%). Rate of flow for the simulation is considered to vary from 0.016 to 0.033 kg/s. Again, this study focuses on utilizing rotating receiver tubes with a varying velocity of 0‐15 rad/s to overcome the stratification of high temperature at the surface. Results show that enhanced values for the temperature at outlet, heat transfer coefficient, and thermal efficiency are noted for a model with elliptical inserts of major diameter 28 mm (longitudinal orientation) at 15 rad/s receivers speed for nanofluid‐1 (aluminum oxide 75%‐ copper oxide 25%) at 0.033 kg/s. The highest increment in heat transfer coefficient, as well as thermal efficiency for the model with a 28 mm major diameter elliptical insert (longitudinal orientation), is 44.21% and 29.21% respectively. Highlights: Use of a spinning receiver reduces the problem of uneven temperature distribution at receiver surface.Maximum 375 K outlet temperature is noted at 15 rad/s for elliptical insert of diameter 28 mm (longitudinal orientation) at 0.016 kg/s.The elliptical insert received the maximum thermal efficiency rating of 82.03%.An elliptical insert in receiver increases pump work by 18.13% than smooth receiver. [ABSTRACT FROM AUTHOR]

In this research work, dimple texture tubes and silicon dioxide (SiO2) nanofluid were used to analyze the performance parameters of a solar water heater. For this purpose, SiO2 was mixed with deionized (DI) water using an ultrasonic dispersion device to prepare the nanofluids (SiO2/DI-H2O). The size of the nanoparticle was in the range of 10-15 nm. Different volume concentrations of the nanoparticles in the range of 0.1% to 0.5%, in steps of 0.1%, were chosen to prepare the nanofluids to carry out the experiments. Apart from this, computational fluid dynamics (CFD) tool was used to numerically analyze the parameters affecting the performance of the solar water heater, as well as the fluid flow pattern in the dimple texture tube. During the experiment, the mass flow rate of the base fluid (water) varied in the range of 0.5 kg/min to 3.0 kg/min in steps of 0.5 kg/min. The added advantage of the dimple texture tube design led to an increase in turbulence in the flow pattern, resulting 34.2% increase in the convective heat transfer efficiency compared with the plain tube. Among all experimental modules, SiO2/DI-H2O with a mass flow rate of 2.5 kg/min and 0.3% volume concentration gives overall optimized results in absolute energy absorption, gradient temperature, and efficiency of the solar water heater. The efficiency metrics of the experimental results were compared with the simulation results, and it was in the acceptable range with an overall deviation of ±7.42%. [ABSTRACT FROM AUTHOR]

Solar energy found abundantly in nature is considered a renewable energy source. It is also of great interest as an option for energy generation and CO2 emissions reduction. Several technologies of solar concentrating systems, known internationally as CSP (concentrated solar power), are found in the industrial and scientific environment. One of the most mature and internationally known technologies is the parabolic trough solar collector (PTSC), which has several applications, such as electricity generation, desalination, steam generation, and refrigeration systems, among others. However, more research and development (R&D) has been done to improve its performance, using new materials, absorber tube geometries, solar tracking systems, and work (thermal oils, nanofluids). Thus, the present work describes the development of a low-cost PTSC for academic and research purposes. The PTSC was built with an edge angle of 120°, an opening area of 2.2 m2, and a copper absorber tube of 42 mm in outer diameter without a glass envelope. The gutter structure is composed of wooden sheets cut in a parabolic shape, where a 1.2 mm-thick galvanized steel sheet coated with a reflective film is supported, thus functioning as the reflective surface of the PTSC. The solar tracking system is one of the active types with two axes containing photoresistive sensors, which are used to determine the solar position and electric actuators to correct the positioning of the gutter. The monitoring system was developed through an interactive panel to visualize the operating parameters of the sensing elements, thermocouples that measure the inlet and outlet temperature in the absorber tube, and the flow sensor to measure the flow of the heat transport fluid. Laboratory tests were performed with deionized water as a transport fluid, establishing two testing conditions. The first test condition analyzed the efficiency of the collector at different temperatures. Thus, the inlet temperature varied, between 30 and 70°C, presenting a flow of 0.020 kg/s. The second one evaluated the collector efficiency for different flows, subjecting the collector to flows from 0.002 to 0.030 kg/s. Thus, the proposed collector obtained an efficiency as a function of the temperature represented by the expression η = 0.324-2.47443 c', where c' is a parameter that relates the inlet temperature to the ambient temperature as a function of the solar radiation available. Yet, the efficiency in function of the flow became optimal when the flow regime became turbulent. It was concluded that the proposed solar collector obtained lower efficiency when compared with other collectors in the literature, which was assumed to be due to the diffusion losses of the parabolic trough reflector and thermal losses by convection in the parabolic trough absorber tube (optical efficiency, removal factor, and heat loss coefficient). [ABSTRACT FROM AUTHOR]

Summary: The development of renewable solar technologies determines the constant need to improve and increase their energy efficiency. Determination of solar systems performance characteristics must take place under given conditions set by proper standards. Due to unstable weather conditions, including temperature and solar radiation, it is necessary to simulate the laboratory conditions' radiation. For these purposes, so‐called solar radiation simulators are being constructed. This article presents the results of solar simulator modeling for parabolic trough collectors testing. A new approach presented here proposes to use reflectors placed parallel on one plane to simulate both, total radiation and direct radiation used in parabolic concentrator tests. The methodology adopted from the normative approach for evaluating the quality of the simulator is presented. The methodology used for solar radiation simulators was modified to test concentrators in constant, repeatable conditions. The analysis was carried out not only to assess the energy distribution on the plane area but also to assess the energy reaching the tubular absorber external surface. The optical engineering ray tracing software, based on Monte Carlo Method, was used for the analysis. A selection of appropriate light sources, quantity, type, and arrangement of reflectors and their coatings was carried out. Metal‐halides and xenon arc lamps were considered as sources. The distribution of radiation intensity on the analyzed surface was determined for two cases, 22 reflectors and 4 reflectors. The analyzed area was 1 square meter. The evaluation index has been defined to determine the quality of the energy distribution. The influence of the simulator distance on the amount of energy reaching the absorber surface was also analyzed. An estimation of the required financial outlays for analyzed constructions of the simulator was performed. Research has shown that in terms of maintaining the energy field's homogeneity and the price for the entire radiation simulator, it is more reasonable to construct a simulator consisting of 22 reflectors. The construction of such a simulator seems to meet the assumptions required for the correct operation of the radiation simulator. Novelty statement: Paper's novelty is the methodology to identify and evaluate solar radiation simulators to simulate heat radiation for parabolic trough collectors. The paper specifies the evaluation index and the way of its interpretation, which determines the radiation distribution on the simulated surface, which is crucial in this issue. In a better and more accurate way, this factor assesses the energy field in terms of quality. Modifying the normative measurement approach of solar radiation on a flat surface, we propose the analysis of concentrated radiation by performing optical analyses using software which are based on the Monte‐Carlo method. The location of light sources on the plane surface is a new approach for PTC testing. [ABSTRACT FROM AUTHOR]

Summary: Nitrate salt with low melting point as heat transfer and storage fluid simplifies the heat transfer, storage, and exchange processes, and organic Rankine cycle as heat and power conversion system can realize the distributed energy supply. This study experimentally investigated the solar organic Rankine cycle with parabolic trough concentrator using nitrate salt as heat transfer and storage fluid, and the main problems and phenomena during the operation process have been described and analyzed in detail. Experimental results showed that the temperature difference of collector tube changes with direct normal irradiation and lags behind the changes of direct normal irradiation. Molten salt heat storage system can effectively restrain the temperature fluctuation at the collector tube outlet. The abrupt temperature drop at the evaporator inlet was caused by the heat imbalance between R123 and nitrate salt and inappropriate design of the evaporator. The effects of expander inlet pressure and expansion ratio on the ORC electrical power output were obtained at different superheating degrees of the expander inlet. The researches on each component are instructive to the technology of the parabolic trough concentrated solar power generation system with molten salt as heat transfer and storage fluid and provide some guides for the subsequent research. Furthermore, the energy and exergy analyses on overall system were developed, and results indicated the system average efficiency can reach 1.5%. Novelty statement: Experimental study on parabolic trough concentrated solar ORC system with nitrate salt as heat transfer and storage medium were firstly analyzed.Single screw expander was firstly applied in a real solar thermal power generation system and showed a stable performance.Dynamic changes on the temperatures of PTC, molten salt tanks, and ORC were shown, and energy and exergy analyses on overall system were carried on. [ABSTRACT FROM AUTHOR]

Summary: The experimental investigation with the incorporation of toroidal rings in an absorber tube of a lab‐scale solar parabolic trough collector is carried out in the present study. Five different cases of the absorber tube including the reference smooth absorber tube and the absorber incorporated with 2, 4, 6 and 8 mm thick toroidal rings are investigated. The influence of performance parameters like thermal efficiency, heat loss, thermal enhancement index and so on with different absorber tube configurations are evaluated, compared and illustrated to determine the best case. The outcomes indicate that the absorber tube with 6 and 8 mm thick toroidal rings are the best cases, with the 8 mm case exhibiting a higher exergy efficiency in the range of 38.57%‐24.64%. The thermal efficiency for the best absorber cases is found to be 69.43% and 70.34% with the pressure drop being 1.67 and 0.93 kPa, respectively. Also, the cost of heat gain produced with the efficient absorber case is seen to be ₹ 3.43/kWh (US$ 0.045/kWh and € 0.040/kWh), which is nearly 15.51% lower than the reference case. Hence, the incorporation of toroidal rings could be effectively utilized in a large‐scale solar thermal system for improved thermal performance. [ABSTRACT FROM AUTHOR]

Summary: This work presents an experimental evaluation of a new design of a parabolic trough solar collector (PTC). To maximize the energy yield, a solar tracking system is implemented. The thermal performance of the PTC at three outdoor test methods is evaluated. The new design essentially affects the balloon, the trunk, the insulation, the inner reflector, the glass, the upper plane reflector, and the cover. The system performance with bi‐axial orientation and an absorber with a glass‐covered envelope is compared with two other designs of mono‐ and bi‐axial orientation without a glass‐covered envelope. The tests of the PTC with an aperture area of 2.88 m2 were conducted in Tunisian weather conditions, and the results are compared with similar systems already published data in the literature. A dynamic simulation with TRNSYS software is developed to evaluate the system performance based on experimental results. An economic study to evaluate the system's feasibility is conducted. The results showed that the new design achieved a maximum temperature of 179°C in comparison to 134 and 120°C for the mono‐ and bi‐axial orientation without a glass‐covered envelope, respectively. Furthermore, in the new PTC design, the useful daily energy gain increased by 33% and 15%, and the system thermal efficiency increased by 8.9% and 5.8% in summer and winter, respectively, in comparison to the case of mono‐axial orientation without a glass envelope. Besides, the maximum useful energy gain and the instantaneous thermal efficiency in the new design were 22.6 MJ and 73.45%, respectively, in comparison to 17.93 MJ and 67.41% for the mono‐axial orientation without a glass‐covered envelope. The gross payback period of the system was found to be 3.3 years with an NPV of €5257 over the lifetime of the system. [ABSTRACT FROM AUTHOR]

As a try, this work has been focused in the way towards the effective contribution in the field of solar aviation using renowned nanotechnology. After realizing the causes and effects of traditionally used energy forms, the search of cost-efficient, eco-friendly, and most prominent renewable source leads us back to the solar utilities. Research era of solar radiation-powered aircraft has been in trend. Focusing on that, an efficient numerical model representing the flow and thermal aspects of a parabolic trough surface collector (PTSC) embedded on solar aircraft wings has been adopted for this study. As the first time with the note, an eminent and leading form of thermal efficient fluid of kind, the Casson hybrid nanofluid has been engaged with the expectations of enhanced performance in the solar aircraft wings. To test it, a trending reputable numerical scheme of the Keller-box method has been utilized and the parametrical studies were carried out. The upshots of those studies provide the affable proofs in favor of our expectations towards the improved solar wings with better thermal efficiency. The glimpse of those successes in the parametrical level has been showcased in the forms of tables and graphs. The lateral "x" direction significant about the inertial forces, suspended particle ratio, and skin resistance phenomena, while for the transverse fluidity in the "y" direction were has to be concern about the magnetic interactions, rotational coordinates, viscous nature of the fluid along with the porous states. The power of hybrid nanofluid combos was exposed in higher notes in a unique state of solar aircraft wings. Furthermore, the thermal efficiency of hybrid nanofluids over nanofluids got down to a minimal level of 6.1% and peaked up to 21.8%. [ABSTRACT FROM AUTHOR]

This research proposes an innovative solar thermal plant able to generate mechanical power through an optimized system of heliostats with Scheffler-type solar receivers coupled with screw-type steam expanders. Scheffler receivers appear to perform better than parabolic trough collectors due to the high compactness of the focal receiver, which minimizes convective and radiative heat losses even at high vaporization temperatures. At the same time, steam screw expanders are volumetric machines that can be used to produce mechanical power with satisfactory efficiency also by admitting two-phase mixtures and with further advantages compared to steam turbines: low working fluid velocities, low operating pressures, and avoidance of overheating. This study establishes a mathematical model to assess the energetic advantages of the planned solar thermal power system by evaluating the solar-to-electricity efficiency for different offdesign working conditions. For this purpose, a numerical model on the Scheffler receiver is initially investigated, thus assessing all the energy losses which affect the heat transfer phase. A thermodynamic model is then developed to evaluate the energy losses and performance of the screw expander under real working conditions. Finally, parametric optimization of the solar energy conversion is performed in a wide range of operating conditions by establishing thermodynamic formulations related to the whole solar electricity generation system. Water condensation pressure and vaporization temperature are so optimized with respect to global energy conversion efficiency which, under the best operating conditions achieved in this research, rises from 10.9% to 14.4% with increasing solar irradiation intensity. Hence, the combined use of screw expanders and Scheffler receivers for solar thermal power system application can be a promising technology with advantages over parabolic dish concentrators. [ABSTRACT FROM AUTHOR]

Summary: The utilization of solar energy to generate electricity, cooling, and freshwater in remote areas in a sustainable way still poses lots of challenges to researchers. The aim of the current study is to design a new solar‐operated trigeneration system to produce electricity, cooling, and fresh water using parabolic trough collectors in remote areas. Electric power is generated by using Organic Rankine Cycle, and cooling and fresh water (using freezing desalination technique) are obtained by two‐stage NH3–H2O vapor absorption system run by solar energy. Simulation results show that for PTC arrays of 200 m2, an electrical output obtained is 3.3 kW, cooling rate is 20.4 kW, and mass flow rate of freshwater produced is 36 kg/h for an average solar irradiation of 0.7 kW/m2. Furthermore, sensitivity analysis is conducted by varying the parameter like solar irradiation, evaporator temperature, seawater inlet temperature, etc. and their effect on performance characteristics of the overall setup is investigated. [ABSTRACT FROM AUTHOR]

Summary: Oil‐based thermal energy storage system with solar collector has become populous due to its simple design and characteristics. Majorly, the solar‐based thermal storage systems operate between 70°C and 150°C temperature, with one disadvantage of inability to store energy during off‐peak hours. The stored energy in thermal storage can be used for the different domestic applications, such as water heating, cooking of food, boiling, etc. An effort has been made to investigate the oil‐based thermal energy storage system with the potential design to achieve the higher temperature range of above 200°C. These systems can be used for domestic applications such as cooking. The integrated thermal storage system has been developed using nitrate salt as phase changing material to store the latent heat. The phase change material is filled in the cavity of the oil‐based thermal storage. The aluminum oxide (Al2O3) and soybean oil nanofluid in a thermo‐syphon is used as a heat transfer fluid to store and transfer the sensible heat. Parabolic trough solar collector is coupled with thermal storage system. The maximum temperature of the phase change material, during the experiment, in thermal storage system was achieved up to 220°C, which is the melting point of phase change material. The mathematical model for the heat transfer analysis is also developed and the results were validated with the experimental results. The various heat transfer analysis using regression analysis is discussed. [ABSTRACT FROM AUTHOR]

Summary: A solar thermal collector collects heat by absorbing sunlight and converting this incoming radiation into useful thermal energy. The parabolic trough solar sollector (PTSC) is widely installed in concentrated solar power technology with a temperature range of 325‐700 K. The thermodynamic efficiency of the PTSC can be intensified by using nanofluids owing to their enhanced thermophysical properties. In this paper, the two‐dimensional flow over a stretched sheet in PTSC under Williamson nanofluid effects is explored. With the help of useful transformations, the partial differential equations arising from boundary layer equations of the Williamson nanofluid model are changed into nonlinear ordinary differential equations. The Keller box numerical scheme is then used to find the solution of the resulting nonlinear ordinary differential equations. Two nanofluids, copper‐engine oil (Cu‐EO) and alumina‐engine oil (Al2O3‐EO) are considered to address the performance analysis of PTSC in this study. It is observed that the parameters of the porous media reduced the heat transfer rate but increased the velocity gradient. In order to examine the effect on various performance parameters of the device, the nanoparticle concentration is also varied. With the increase in the Reynolds and Brinkman numbers, the entropy is found to increase. The thermodynamic performance of the Cu‐EO nanofluid is remarkably better than that of the Al2O3‐EO nanofluid under the same conditions. The thermal efficiency of Cu‐EO over Al2O3‐EO is seen with a minimum of 1.5% and a maximum of 9.1%. The theoretical simulations documented here may be effective in improving solar thermal energy systems. [ABSTRACT FROM AUTHOR]

Summary: In this study, a stand‐alone parabolic solar dish/Stirling (PSDS) system model is developed and investigated. The techno‐enviro‐economic performance of a 25‐kW stand‐alone PSDS system is simulated in the System Advisor Model (SAM) tool under ambient conditions of Jamshoro, Pakistan. The avoided CO2 emissions due to the installation of the proposed system are calculated in an Excel spreadsheet. The methodology for emissions calculation is based on the average value of emissions per kWh recommended by the Intergovernmental Panel on Climate Change (IPCC). The results indicate that the proposed PSDS system generates 38.6 MWh of electrical energy annually, and the maximum energy of 3.38 MWh is achieved in January. The main reason for that is the highest value of DNI in that month. The system has attained a net efficiency of 23.39% and a levelized cost of energy (LCOE) of 0.13 $/kWh. The yearly emissions from PSDS are 762 kg, which is only 2.2% and 4.69% of coal and natural gas, respectively. Moreover, the sensitivity analysis of the PSDS system showed that the projected mirror area and collector cost affects the power output and cost of generation significantly. [ABSTRACT FROM AUTHOR]

Summary: Evacuated tube (ET) solar collectors are utilized in all climatic conditions for harnessing solar energy. This work aims to investigate thermal performance of ET with compound parabolic concentrator collector, integrated to a multiple phase change material‐based thermal energy storage (TES) system. The phase change material (PCM) have been selected depending on the degree of stratification in sensible heat storage configuration under constant heat load conditions. The charging experiments have been performed under three different TES configurations viz. sensible heat storage, three ("Case 1") and five ("Case 2") PCMs, using water as the heat transfer augmenting the energy storage by 41% than the sensible heat storage. A higher stratification number in "Case 2" reveals the significance of multiple PCMs in improving the charging efficiency of TES system. Cascaded arrangement of PCMs facilitates the supply of HTF at lower temperature to the collector resulting with an increase in useful heat energy gained. The instantaneous thermal efficiency of collector with "Case 2" is as high as 58%, storing 27 MJ d−1. Use of ET‐CPC and TES system with cascaded arrangement of PCMs finds potential application in water heating system. [ABSTRACT FROM AUTHOR]

Summary: Thermochemical energy storage, a promising candidate for seasonal solar thermal energy storage, offers an economic solution to mitigate the use of fossil fuels and CO2 emissions due to its large storage density and almost zero‐loss long‐term storage. The present article explored the potential of the thermochemical seasonal energy storage system using MgO/Mg(OH)2 system for solar district heating applications in China. The solar district heating model with thermochemical seasonal energy storage system, including the parabolic trough solar collector and a chemical reactor, has been built. The dynamic charging/discharging performance of the seasonal solar thermal energy storage system has been simulated and analyzed by using the real weather data and the practical domestic heating demand. The optimal parameters of the equipment have been identified. And the comparison of the performances between thermochemical seasonal energy storage system and the conventionally used water storage tank system has been carried out for various areas of China. The results indicate that the stored thermochemical energy is able to contribute 94.6% of heating demand in the discharging stage, demonstrating the application potential of MgO/Mg(OH)2 thermochemical energy storage system in China. The needed solar collector areas of the seasonal thermochemical energy storage system decrease by up to 2/3 compared with those of a water storage tank system in the condition of the similar storage system volume. The advantage of seasonal thermochemical energy storage is more obvious for the case of region with abundant solar energy supply. [ABSTRACT FROM AUTHOR]

Summary: Among the diverse renewable energy sources available, solar energy harnessing has become very common in most countries. Various collectors were developed, built and checked to work in various temperature ranges. The parabolic trough solar collector is found to be the most common among the other collectors in applications such as the distribution of process heat and the production of steam. The heat collector part known as receiver tube is one of the key practical devices of parabolic trough solar collector. Numerous research studies have centered on receiver tube to raise its thermal potential. The usage of passive techniques such as provision of inserts in the receiver tube and geometrical changes of receiver tube are efficient strategies for increasing thermal performance. Detailed review of the numerical and experimental studies conducted on heat transfer enhancement strategies that rely on the use of inserts with the use of different working fluids in a parabolic trough solar collector's receiver tube is described in this article. Additionally heat transfer enhancement due to geometrical modification of receiver tube is also presented. Further, on the basis of literature survey, a comparison among various strategies is outlined. These studies show that future work in this area, that is, usage of passive techniques in parabolic trough solar collector will offer further growth. [ABSTRACT FROM AUTHOR]

Summary: Large‐aperture parabolic trough solar collector (PTSC) has the potential to improve the performance of the solar field and also to reduce the capital cost of the power plant. In the present study, coupled flux distribution and thermal analysis of large aperture PTSC are presented by incorporating the limb darkening effect. MATLAB tool is used to develop the in‐house model to obtain the circumferential flux distribution on the absorber surface. The analyses are performed for different Sun shape models, the number of rays, aperture, rim angle, slope error, and receiver displacement on the flux distribution. The flux distribution for large aperture PTSC such as 7, 8, 9, and 10 m has also been studied with an available absorber diameter of 70, 80, 90 and 110 mm. Better manufacturing standards need to be incorporated to improve the performance of the large aperture PTSC with available receiver sizes. There is no significant effect on the intercept factor for the upward and downward displacement of larger aperture PTSC receiver, but the downward displacement of the conventional PTSC receiver drastically decreases the intercept factor. Based on the flux distribution analysis, a collector geometry having an aperture of 9 m with an absorber diameter of 110 mm has been considered for the thermal analysis. The effect of variation of the mass flow rate, aperture, and various heat transfer fluids are studied on the PTSC thermal performance. Liquid sodium offers the least thermal gradient around the absorber circumference, which leads to less deformation of the receiver from the focal length. [ABSTRACT FROM AUTHOR]

Summary: The utilization of hybrid nanofluids is a promising technique in the high temperature solar applications specially, parabolic trough collector (PTC). The purpose of the current research is to analyze, evaluate and compare the performance of PTC (converging‐diverging absorber tube) using mono and hybrid nanofluids to increase the convective heat transfer coefficient. To obtain this objective, converging‐diverging tube with sine geometry is examined as it enhances the turbulence in the flow due to increase in the inner surface roughness. The performance of the absorber tube is assessed for hybrid nanofluid (1.5% MWCNTs/therminol‐VPI and 1.5% TiO2/therminol‐VPI) as well as mono nanofluids (3% MWCNTs and 3% TiO2)/therminol‐VPI at a wide range of inlet temperature ranges from 350 K to 600 K. In order to compare the results of the converging‐diverging tube, a smooth absorber tube is also investigated at the same design conditions. Furthermore, our study comprises of the overall performance investigation about the exergy analysis, pressure drop, pumping power required and performance evaluation criteria to investigate the comprehensive performance of the absorber tubes. The results of the study reveal that the use of modified geometry with hybrid nanofluids considerably improves the performance of the system due to the presence of swirls and turbulence that will reduce absorber surface temperature and ultimately the heat losses. More specifically, the thermal efficiency enhancement for the converging‐diverging absorber tube with hybrid nanofluids ranges from 3.61% to 5.27%, while it is varied from 1.70% to 1.91% for smooth tube using hybrid nanofluids. Reynolds number ranges from 12 000 to 90 300 for hybrid nanofluid, while it is from 14 000 to 97 600 for pure therminol‐VPI. Furthermore, mean enhancement in the heat transfer coefficient using converging‐diverging tube with hybrid, TiO2 and MWCNTs therminol‐VPI‐based nanofluids are 1.72%, 0.67% and 0.70%, respectively at a mass flow rate of 0.6 kg/s and an ambient temperature of 300 K. The converging‐diverging/hybrid case has the values of 1.47 and 1.33 for performance evaluation criteria I and II, while all other cases has significantly less values compared to hybrid nanofluids. The thermal efficiency enhancement has a pressure‐drop penalty that leads to higher pumping power requirement; however, this requirement is very small as compared to the useful energy gain. [ABSTRACT FROM AUTHOR]

Summary: Hybrid nanofluids with Therminol‐55 as base fluid and TiO2 and Al2O3 as nano additives are investigated for parabolic trough collectors. Stable mono nanofluids based on Therminol‐55 with Al2O3 and TiO2 nanoparticles, and hybrid Al2O3–TiO2 nanopowder as additives are prepared by the two‐step method. Oleic acid has been made as a surfactant. The impact of nanoparticle content and fluid temperature on thermal conductivity was studied using the transient hot‐wire technique. Thermal conductivity exhibited an increase with an increase in both temperature and nanoparticle concentration. Al2O3–TiO2 Therminol‐55 hybrid nanofluids exhibit the highest increase of 33.5% in thermal conductivity followed by 27.06% in Al2O3–Therminol‐55, and lowest rise of 21% is found in TiO2–Therminol‐55 nanofluids. Synergetic effect of Al2O3 and TiO2 nanoparticles, increased Brownian motion, and filling of vacant spaces by smaller‐sized TiO2 nanoparticles in Al2O3–TiO2 hybrid nanofluids lead to effective thermal network for enhanced thermal conductivity. Maximum thermal conductivity of 0.15 W/m‐K is observed in the case of hybrid Al2O3–TiO2 Therminol‐55 nanofluid with 0.5 wt% concentration. Augmented thermal conductivity of HNF's leads to the efficient photothermal conversion in concentrating solar collectors. Further, a correlation for thermal conductivity with variation in nanoparticle content and the fluid temperature is proposed with R2 = 0.92. [ABSTRACT FROM AUTHOR]

Summary Utilization of a single evacuated tube heat pipe solar collector (ETHPSC) for the efficient deployment of the solar energy toward driving the Encontech heat engine for reverse osmosis desalination is considered in this study. The effects of the mass flow rate of water mw˙, inlet temperature (Ti), solar intensity (I), the ratio of the condenser to absorber area (Aco/Aabs), heat transfer coefficients (hair and hvacuum) on energy and exergy efficiency (η, ηEx), the absorber (Tabs), condenser (Tco), and the outlet temperature (To) are explored by using a heat transfer resistance model. An open‐source SCILAB software was used for performing the computer simulations. The simulation results show that for each hair there is an optimum Ti (based on the exergetic performance). The lower hair and hvacuum appears to be more promising to improve the efficiency and temperature gain (Ti − To) of the ETHPSC. The maximum energetic efficiency of 52.5% is obtained for hvacuum (1 W/m2K). Obtained results further demonstrate that the energetic and exergetic performances of the ETHPSC are higher at Ti = 50°C. Both energetic and exergetic efficiencies exhibit upper values at Aco/Aabs ratio up to 1. Further increment in this ratio up to 3 resulted in a decrease in the efficiency of the ETHPSC. [ABSTRACT FROM AUTHOR]

Summary: Fossil fuel‐powered thermal desalination processes have many harmful environmental effects including greenhouse gas (GHG) emissions and high‐salinity brine discharge resulting in biological damages, in addition to energy losses because of the high temperatures of the streams leaving the desalination unit. In this study, a solar energy‐based polygeneration approach has been proposed to address these issues. In the proposed system, concentrated solar parabolic trough technology is used to drive a multi‐stage flash (MSF) desalination unit for production of fresh water. To recover the waste heat carried by the produced clean water, an organic Rankine cycle is integrated to produce electricity. In addition, to recover the waste heat carried by brine, an absorption cooling system is employed to provide cooling. In order to mitigate the effects of high‐salinity brine, a pressure retarded osmosis (PRO) unit is installed, which reduces the salinity of the discharge and produces additional electrical energy. To ensure stable nighttime operations, a thermal energy storage (TES) system is also added to the system. A comprehensive thermodynamic analysis is conducted through mass, energy, and entropy, as well as exergy balances along with energetic and exergetic efficiencies to assess the overall performance of the system. The attained results show that at reference conditions with an overall parabolic trough collectors (PTCs) area of 100 000 m2, the system produces 583.3 kW of electricity, approximately 4284 kW of cooling, and 1140 m3 of freshwater daily. Furthermore, the effects of changing operational conditions on the overall performance of the system are investigated. At design conditions, the overall energetic and exergetic efficiencies of the system are found to be 34.54% and 14.55%, respectively. [ABSTRACT FROM AUTHOR]

Summary: Solar steam power plant is the dominant technology in the category of solar thermal power systems. In steam power cycles, there is usually a couple of steam lines, extracted from medium‐pressure and low‐pressure turbines, to preheat the working fluid before the boiler. This although leads to an increase in the energy efficiency of the cycle, reduces the contribution of the turbine proportionally. Therefore, finding an alternative method of preheating the working fluid would be effective in further enhancement of the efficiency of the system. In this study, the feasibility of using solar collectors for the preheating process in a solar steam power plant is investigated. For this, parabolic trough solar collectors and evacuated tube solar collectors based on a wide range of different scenarios and configurations are employed. The plant is designed, sized and thermodynamically analyzed for a case study in Saudi Arabia where there is a large solar irradiation potential over the year. The results of the simulations show that, among all the considered scenarios, a power cycle aided by a set of parabolic trough collectors as the preheating unit is the best choice technically. This configuration leads to about 23% increased power generation rate and 6.5% efficiency enhancement compared to the conventional design of the plant. Highlights: Performance enhancement of solar steam power plant in Saudi Arabia is investigated.Replacement of feed water heating via turbine extraction by solar thermal systems is proposed.Solar parabolic trough and evacuated tube collectors are considered as potential solutions.Six different scenarios are investigated to cover all the possibilities.The best solution among all the investigated scenario is introduced. In this study solar thermal units in different arrangements and configurations come into service to provide feedwater heating in conventional solar steam power plants. This results in a stronger effectiveness of solar energy in the system and a considerable improvement of the cycle efficiency. Comparison of different designs in terms of thermal effectiveness makes it clear which type of collector in which arrangement is the best choice. [ABSTRACT FROM AUTHOR]

Summary: A wide range of engineering industrial applications require both the thermal and optical efficiencies of the system to be maximized with a reasonable low penalty for the friction factor and subsequently low losses in pressure. Among the family of concentrated solar power systems, parabolic trough collectors (PTCs), which have recently received significant attention, face similar challenges. The current work presents an extensive review of the PTC systems comparing recent and past technologies, which are widely being used to improve and enhance the thermal and optical efficiencies. Furthermore, the techniques used for single and two‐phase flow modeling in numerical simulations, design variables, and experimental processes have been discussed in detail. The article also presents different numerical methods and analytical approaches of implementing the nonuniform solar distribution with different design parameters. Four main technologies are comprehensively addressed to effectively enhance the thermal performance of the PTCs; changing working heat transfer fluids, replacing the working fluids by nanofluids (single and hybrid) that have higher thermal–physical properties than those of base working fluids, inserting different tabulators with various design configurations, and finally combining the advantages of nanofluids and swirl generators in the same application. The article also critically summarizes the studies investigating the enhancement of thermal performance: use of novel design of PTCs and passive heat transfer enhancement techniques. Finally, a wide range of numerical and experimental studies are proposed for the future work related to the aforementioned main technologies. [ABSTRACT FROM AUTHOR]

Summary: Thermal storage, low power tariff at night, and low nocturnal temperature can be used in synergy to reduce the cooling costs of the solar‐powered absorption chiller cooling systems. This study aims to reduce the required cooling capacity of an absorption chiller (ACH) powered by a solar parabolic trough collector (PTC) and a backup fuel boiler by integrating thermal storage tanks. The thermal performance of the system is simulated for a building that is cooled for 14 h/day. The system uses 1000 m2 PTC with 1020 kW ACH. Chilled water storage (CHWS) and cooling water storage (CWS) effects on the system performance for different operation hours per day of the ACH under Izmir (Turkey) and Phoenix (USA) weather conditions are analyzed. When the ACH operates 14 h/day as the load for both systems and both locations, the variations of the solar collector efficiency and the cooling load to heat input ratio remain less than 4% after the modifications. From the addition of CHWS to the reference system, a parametric study consisting of changing the ACH operation hours per day shows that the required cooling capacity of the ACH can be reduced to 34%. The capacity factor of the ACH is improved from its reference value of 41% up to 96%. [ABSTRACT FROM AUTHOR]

Summary: The aim of the present work is to enhance the thermal management avoiding the high‐thermal stress on the outer surface of the parabolic trough receiver (PTR) derived from nonuniform concentrated solar flux distribution. A parabolic trough concentrating (PTC) system with second homogenizing reflector (HR) is numerically designed and optimized to ensure a uniform concentrated solar flux on the PTR walls. For this purpose, a three‐dimensional optical model has been developed to analyze quantitatively the improvement made by the HR using the optical efficiency and qualitatively basing on the uniformity of the solar flux density distribution over the entire surface of the PTR. The validation of the numerical tool is presented, and the algorithm of the design process has been proposed and detailed. As a preliminary trait, it was revealed that the peak of the designed system performance is achieved with a rim angle of 68° avoiding simultaneously the aberration and the blocking effects. Despite the optical efficiency decrease by about 7% compared with the conventional PTC design, the uniformity of the solar flux distribution has been strongly improved such that the maximum local solar flux density gradient is decreased from 80 to 11 kW/m2 equivalent to a decrease of 86.25% with respect to the conventional PTC and the average local density is about 25.5 kW/m2. [ABSTRACT FROM AUTHOR]

Summary: A renewable energy based integrated system is developed to meet the total energy demands of a house located off‐grid, and a thermodynamic analysis through energy and exergy methodologies is conducted for analysis, evaluation, and performance assessment. The present novel multigeneration system is mainly driven through the animal residues produced at the farm house. The proposed novel system is composed of nine main units namely, a biomass combustor, photovoltaic (PV) panels, parabolic solar trough collectors, thermoelectric generators, organic Rankine cycle, electrolyzer, homogeneous charged compression ignition (HCCI) engine, absorption chiller, and reverse osmosis (RO) unit. Biomass combustor runs an organic Rankine turbine for additional power during peak loads. The exhaust of gas turbine generates cooling to meet the cooling demand of the residential area of the farm house. PV panels are incorporated to generate hydrogen through electrolyzer. A HCCI engine generates power to compensate peak load as well as charging the farming vehicles of the farm house. The RO unit with energy recovery Pelton turbine produces fresh water for farming and residential use. The advanced integration of subsystems, thermoelectric generators and efficient utilization of waste, improves significant amount of energetic and exergetic efficiencies of overall multigenerational system. The energy and exergy efficiencies are enhanced in the order of 4.8% and 6.3%, respectively, after incorporating innovative cooling system to the PV modules. The overall energy and exergy efficiencies of the proposed multigeneration system with and without thermoelectric are found to be 67.6% and 57.1%, and 68.9% and 58.4%, respectively. [ABSTRACT FROM AUTHOR]

Summary: This paper provides fundamental principles to study the thermodynamic performance of a new screw expander–based solar thermal electricity plant. While steam turbines are generally used in direct steam generation solar systems without admitting fluid in two‐phase conditions, steam screw expanders, as volumetric machines, can convert thermal to mechanical energy also by expanding liquid‐steam mixtures without a decline in efficiency. In effect, steam turbines are not as competitive as screw expanders when the net power is smaller than 2 MW and for low‐grade heat sources. The solar electricity generation system proposed in this paper is based on the steam Rankine cycle: Water is used as both working fluid and storage, parabolic trough collectors are used as a thermal source, and screw expanders are used as power machines. Since screw expanders can operate at off‐design working conditions in several situations when installed in direct steam generation solar plants, studying expander performance under fluctuating working situations is a crucial issue. The main aim of the present paper is to establish a thermodynamic model to study the energetic benefits of the proposed power system when off‐design operating conditions and variable solar radiation occur. This entails, first and foremost, developing overexpansion and underexpansion numerical models to describe the polytropic expansion phase, which considers all the losses affecting performance of the screw expander under real operating conditions. To assess the best operating conditions and maximum efficiency of the whole power system at part‐load working conditions under fluctuating solar radiations, parametric optimization is then improved in a wide range of variable working conditions, assuming condensation pressures of water increasing from 0.1 to 1 bar, under an evaporation temperature rising from 170°C to 300°C. [ABSTRACT FROM AUTHOR]

This paper investigates the impacts of dispatchability of Parabolic Trough Concentrated Solar Power (PT-CSP) systems over PV power plants in Palestinian territories. Jericho governorate was taken as a case study. All conditions required for implementing PV and PT-CSP systems are verified. The capacity of each investigated system is 1 MW, and both systems are investigated in terms of technical, economic, and environmental aspects. The parametric analysis is used to identify the most feasible option of each renewable energy system by varying the cost of each option candidate and introducing thermal energy storage (TES) to the technology of PT-CSP systems with different capacities. A software based on the MATLAB environment is programmed to estimate the energy produced from each system with the important technical, financial, and environmental indicators. It is found that the alternative of installing a 1 MW PV system is the installation of 1 MWe PT-CSP systems with 14.5 h or 18.5 h TES. Introducing TES improves the dispatchability of the system and the capacity factor which consequently justifies the PT-CSP system investment. Increasing the degree of dispatchability improves the capacity factor of the PT-CSP system from 21% at 0 h TES to 57% at 18.5 h TES (24 h operation). The capacity factor of the PV system is 18.7% which is mostly similar to PT-CSP with zero dispatchability (0 h TES). The study considers the environmental benefits by estimating the amount of avoided CO2 emissions, and it was found that increasing the capacity factor augments the environmental benefits. [ABSTRACT FROM AUTHOR]

Summary: In this study, the energetic and exergetic efficiencies of a salt gradient cylindrical solar pond (SGCSP) that integrated and nonintegrated evacuated tube solar collectors (ETSCs) are investigated to improve daily heat preservation performance of the heat storage zone (HSZ). The integrated system is consisted of an SGCSP and four ETSCs. The SGCSP has a surface area of 2 m2, a depth of 1.65 m, salty water layers at different densities, and HSZ in which the cylindrical serpentine type heat exchanger (CSHE) is located. Thus, the daily effects of the heat storage performance of both the ETSCs and the SGCSP in the winter season was determined experimentally. The analysis of the data regarding the efficiencies of the system is investigated separately by means of experimental studies where the SGCSP is integrated and nonintegrated with the ETSCs. The number of ETSCs integrated with SGCSP is increased to 1, 2, 3, and 4, respectively, and each of the five different experimental systems is performed separately. The temperature distributions of the integrated system are measured by a data acquisition system on 11 different points per hour. The efficiencies are calculated using the data obtained from these studies. Consequently, the energetic and exergetic efficiencies of the SGCSP are obtained without collectors as 10.4% and 4.3% and with one collector as 12.83% and 6.15%, with two collectors 14.88% and 8.25%, with three collectors 16% and 9.35%, and finally with four collectors 16.94% and 10.3%, respectively. Furthermore, the theoretical efficiencies are found to be consistent with the experimental results obtained by increasing the collector numbers. [ABSTRACT FROM AUTHOR]

Summary: In this study, parabolic trough collector with an integrated source of geothermal water is used with regenerative Rankine cycle with an open feedwater heater, an electrolyzer, and an absorption cooling system. The absorption fluids used in the solar collectors were Al2O3‐ and Fe2O3‐based nanofluids. Detailed energetic and exergetic analyses are done for the whole system including all the components. A comparative analysis of both the used working fluids is done and plotted against their different results. The parameters that are varied to change the output of the system are ambient temperature, solar irradiance, the percentage of nanofluids, the mass flow rate of the geothermal well, the temperature gradient of the geothermal well that had an effect on the net power produced, and the outlet temperature of the solar collector overall energetic and exergetic efficiencies. Other useful outputs by this domestic integrated multigeneration system are the heating of domestic water, space heating (maintaining the temperature at 40°C‐50°C), and desalination of seawater (flash distillation). The hydrogen production rate for both the fluids diverges with each other, both producing average from 0.00490 to 0.0567 g/s. [ABSTRACT FROM AUTHOR]

Summary: A novel hybrid PVT/parabolic trough concentrator (PTC)/organic Rankine cycle (ORC) solar power system integrated with underground heat exchanger has been proposed. The evaporator unit consists of a transparent flat PVT solar collector and a PTC connected in series. The first transparent solar collector has transparent covers and consists of solar cells totally immersed within a pressurized transparent organic fluid that allows the solar radiation to reach the solar cells, cools them effectively, and captures all thermal losses from the solar cells. The second concentrator is a conventional one with opaque black receiver used to reheat the transparent organic fluid to higher temperatures. Both solar collectors (the PVT and PTC) perform as the boiler and superheater for the ORC. The performance of the proposed system is investigated by a steady‐state mathematical model. The results show that, at design conditions, the efficiency of the PV modules stabilizes around 12%, absorber efficiency varies within 64% to 75%, and the ORC efficiency varies within 7% to 17%. [ABSTRACT FROM AUTHOR]

Summary: Parabolic trough solar collector (PTSC) is one of the most proven technologies for large‐scale solar thermal power generation. Currently, the cost of power generation from PTSC is expensive as compared with conventional power generation. The capital/power generation cost can be reduced by increasing aperture sizes of the collector. However, increase in aperture of the collector leads to higher heat flux on the absorber surface and results in higher thermal gradient. Hence, the analysis of heat distribution from the absorber to heat transfer fluid (HTF) and within the absorber is essential to identify the possibilities of failure of the receiver. In this article, extensive heat transfer analysis (HTA) of the receiver is performed for various aperture diameter of a PTSC using commercially available computational fluid dynamics (CFD) software ANSYS Fluent 19.0. The numerical simulations of the receiver are performed to analyze the temperature distribution around the circumference of the absorber tube as well as along the length of tube, the rate of heat transfer from the absorber tube to the HTF, and heat losses from the receiver for various geometric and operating conditions such as collector aperture diameter, mass flow rate, heat loss coefficient (HLC), HTF, and its inlet temperature. It is observed that temperature gradient around the circumference of the absorber and heat losses from the receiver increases with collector aperture. The temperature gradient around the circumference of the absorber tube wall at 2 m length from the inlet are observed as 11, 37, 48, 74, and 129 K, respectively, for 2.5‐, 5‐, 5.77‐, 7.5‐, and 10‐m aperture diameter of PTSC at mass flow rate of 1.25 kg/s and inlet temperature of 300 K for therminol oil as HTF. To minimize the thermal gradient around the absorber circumference, HTFs with better heat transfer characteristics are explored such as molten salt, liquid sodium, and NaK78. Liquid sodium offers a significant reduction in temperature gradient as compared of other HTFs for all the aperture sizes of the collector. It is found that the temperature gradient around the circumference of the absorber tube wall at a length of 2 m is reduced to 4, 8, 10, 13, and 18 K, respectively, for the above‐mentioned mass flow rate with liquid sodium as HTF. The analyses are also performed for different HTF inlet temperature in order to study the behavior of the receiver. Based on the HTA, it is desired to have larger aperture parabolic trough collector to generate higher temperature from the solar field and reduce the capital cost. To achieve higher temperature and better performance of the receiver, HTF with good thermophysical properties may be preferable to minimize the heat losses and thermal gradient around the circumference of the absorber tube. [ABSTRACT FROM AUTHOR]

In this study, the form and operation modes of a novel solar-driven cogeneration system consisted of various solar collectors (flat plat collectors (FPC), evacuated tube collectors (ETC), and parabolic trough collectors (PTC)) and ORC (organic Rankine cycle) based on building heating load are analyzed. This paper mainly obtains the fitting formula of thermal efficiency of the ORC power generation device and determines the form and operation mode of the cogeneration system. The form is the same, but the operation modes are different for PTC and FPC or ETC. There are six operating modes, respectively, based on the size relationship between the heating load of buildings and the effective heat collection of the solar collector subsystem when the solar collectors are PTC or FPC and ETC. [ABSTRACT FROM AUTHOR]

Summary: An improved solar parabolic trough collector model has been developed in this study, to overcome the weakness of the previous published studies in predicting accurate performance, at higher operating temperatures. To check the accuracy of the proposed model, both on‐sun and off‐sun tests have been considered. The on‐sun tests are aimed to check the potential of the model for predicting the thermal efficiency while off‐sun tests are for heat losses. The results have indicated that the efficiency uncertainties of the present model are lower than those obtained during the experimental tests of Sandia National Laboratory for all the cases. When compared with previous published models, the proposed model is ranked first, more accurately than those of NERL, Garcia, and Behar. An average uncertainty of less than 0.50% has been obtained while Behar's model show less precision with a deviation of more than 0.55%. The models of Forristall and Garcia‐Valladares have been ranked third and last respectively, with absolute uncertainty of 0.782% and 1.202%. The evaluation of the accuracy of the model in predicting the heat losses have been carried out based on 7 test cases of different ambient conditions. At higher operating temperatures, the present model has shown significant improvements. At 350°C, the model has shown an uncertainty similar to that of experimental tests, ie, 7.3 W/m2. Moreover, it has been ranked first with an average deviation of 3.42 W/m2, more accurate than those developed by Behar, Garcia, and Forristall. If the glass of the solar receiver is broken during operation, the present model might offer some knowledge about their performance. Indeed, the model has also been checked for predicting the thermal performance of PTC with air in the annulus of solar receivers. The RMSE is found to be less than 1.5% for the case of efficiency during on‐sun tests, and values of 2.292% and 1.562% have been obtained for Garcia‐Valladares and Forristall models. Similar finding has been observed for the case of heat losses. Therefore, the proposed model might be an accurate tool for parabolic trough collector performance predictions. An improved PTC model is developed and validated with experiments. The model overcomes the issue of Behar model. The model is more accurate than Behar, Garcia, and EES model. [ABSTRACT FROM AUTHOR]

Summary: Present work encompasses developing a new methodology to incorporate the heat transfer characteristics of the evacuated space (vacuum) in the annulus region between the absorber tube and glass cover and the effect of selective coatings on the steel absorber tube for a 3‐dimensional computational fluid dynamics model of a parabolic trough solar collector (PTSC) receiver. In the present work, glass cover has been modeled semitransparent to the incoming solar flux, which has been applied on the glass cover. Wavelength‐dependent absorption properties of glass cover material also has been modeled. In the current work, the direct normal irradiation and the mass flow rate of heat transfer fluid (HTF) has been varied to check their individual effect on the performance of PTSC absorber tube. Circumferential temperature distribution of absorber tube and glass cover has been found out; heat transfer to HTF and pressure drop of HTF in the absorber tube have also been calculated. A comparative study has been undertaken to highlight the relative contribution of the vacuum and selective coating on the receiver performance. The value of circumferential temperature difference at mid‐length of absorber tube was found to be 14.78 K for 750 W/m2, which increases to 19.70 K for direct normal irradiation of 1000 W/m2. When vacuum is replaced by air in the annulus region, PTSC absorber performance decreases by 4.82%. Similarly, because of use of selective coating, the thermal efficiency of the receiver increased by 34.59%. Present work encompasses development of a new methodology to incorporate heat transfer characteristics of the evacuated space (vacuum) in the annulus region between the absorber tube and glass cover and selective coatings on the steel absorber tube for a 3‐dimensional computational fluid dynamics model of a parabolic trough solar collector receiver. Glass cover has been modeled semitransparent to the incoming solar flux, which has been applied on the glass cover. [ABSTRACT FROM AUTHOR]

Summary: The parabolic trough collector is 1 of the most deployed solar concentrating collectors in the world. In this research, the commercially available LS‐2 collector has been modeled using the engineering equation solver. The developed model is validated using the experimental results of the Sandia National Laboratory, LS‐2 collector test. The study presents a comparison of the exergetic performance of 4 different absorber tube geometry configurations: conventional absorber tube, longitudinal finned tube, absorber tube with twisted tape insert, and converging‐diverging absorber tube. The system is analyzed to observe the nature of exergy losses and exergy destruction for the various design configurations with the use of Therminol VP‐1 and Al2O3‐Therminol VP‐1 nanofluids. The results show that the biggest cause of reduced useful work is because of the destructed exergy from the sun to the absorber. While the optical errors account for a higher percentage of exergy losses. The converging‐diverging absorber geometry produced the best exergetic enhancement of 0.65% with the use of Therminol VP‐1 and 0.73% with the use of Al2O3/Therminol VP‐1 nanofluid. [ABSTRACT FROM AUTHOR]

The current study presents a numerical and real-time performance analysis of a parabolic trough collector (PTC) system designed for solar air-conditioning applications. Initially, a thermodynamic model of PTC is developed using engineering equation solver (EES) having a capacity of around 3 kW. Then, an experimental PTC system setup is established with a concentration ratio of 9.93 using evacuated tube receivers. The experimental study is conducted under the climate of Taxila, Pakistan in accordance with ASHRAE 93-1986 standard. Furthermore, PTC system is integrated with a solid desiccant dehumidifier (SDD) to study the effect of various operating parameters such as direct solar radiation and inlet fluid temperature and its impact on dehumidification share. The experimental maximum temperature gain is around 5.2°C, with the peak efficiency of 62% on a sunny day. Similarly, maximum thermal energy gain on sunny and cloudy days is 3.07 kW and 2.33 kW, respectively. Afterwards, same comprehensive EES model of PTC with some modifications is used for annual transient analysis in TRNSYS for five different climates of Pakistan. Quetta revealed peak solar insolation of 656 W/m2 and peak thermal energy 1139 MJ with 46% efficiency. The comparison shows good agreement between simulated and experimental results with root mean square error of around 9%. [ABSTRACT FROM AUTHOR]

The nonfragile cavity receiver is of high significance to the solar parabolic trough collector (PTC). In the present study, light distributions in the cavity under different tracking error angles and PTC configurations are analyzed. A new elliptical cavity geometry is proposed and analyzed. It is obtained from this study that light distribution on the tube receiver is asymmetrical when tracking error occurs. On increasing the tracking error angle, more lights are sheltered by the cavity outer surface. The PTC focal distance has negative correlation with the cavity open length, whereas the PTC concentration ratio has positive correlation with the cavity open length. Increasing the tracking error angle and increasing the PTC focal distance would both decrease the cavity blackness. Introducing a flat plate reflector at the elliptical cavity open inlet can largely increase the cavity darkness. [ABSTRACT FROM AUTHOR]

Solar parabolic trough collector (PTC) is the best recognized and commercial-industrial-scale, high temperature generation technology available today, and studies to assess its performance will add further impetus in improving these systems. The present work deals with numerical and experimental investigations to study the performance of a small-scale solar PTC integrated with thermal energy storage system. Aperture area of PTC is 7.5 m2, and capacity of thermal energy storage is 60 L. Paraffin has been used as phase change material and water as heat transfer fluid, which also acts as sensible heat storage medium. Experiments have been carried out to investigate the effect of mass flow rate on useful heat gain, thermal efficiency and energy collected/stored. A numerical model has been developed for the receiver/heat collecting element (HCE) based on one dimensional heat transfer equations to study temperature distribution, heat fluxes and thermal losses. Partial differential equations (PDE) obtained from mass and energy balance across HCE are discretized for transient conditions and solved for real time solar flux density values and other physical conditions of the present system. Convective and radiative heat transfers occurring in the HCE are also accounted in this study. Performance parameters obtained from this model are compared with experimental results, and it is found that agreement is good within 10% deviations. These deviations could be due to variations in incident solar radiation fed as input to the numerical model. System thermal efficiency is mainly influenced by heat gain and solar flux density whereas thermal loss is significantly influenced by concentrated solar radiation, receiver tube temperature and heat gained by heat transfer fluid. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

In order to reduce the cost and improve the efficiency of daylighting, an innovative parabolic trough solar lighting and thermal (PTL/T) system is designed and analyzed in this paper. Parabolic trough solar lighting and thermal system uses parabolic trough collector (PTC) controlled by two-axis solar tracking system as solar collector. The collected sunlight is split by a cold mirror into visible light and infrared. The visible light is reflected by cold mirror, re-concentrated by a second-stage Fresnel lens, and then delivered by plastic optical fiber to the buildings for daylighting. The infrared goes through cold mirror, reaches thermal system, and is used for heating generation. The basic structure of PTL/T was outlined and described. The dimension of fiber bundle and parabolic trough was chosen after an optimal analysis. The cost of illuminating unit area was expressed as a function of illumination space dimensions and critical components efficiency. A case study was conducted to get a specific optimized illumination area and PTC area for the first time. The optimized result is to use 8-m2 PTC as collector to illuminate 500-m2 office space. The total solar energy utilization efficiency is 39.4%, with the lighting efficiency of 16.3% and thermal efficiency of 23.1%. The maximum energy savings and simple payback period were calculated for 10 typical cities when applied in residential, commercial, and industrial sectors. The amounts of greenhouse gas-emission reductions were also calculated. The payback period in Sunbelt region is as low as less than 10 years like in Los Angeles. The results show the proposed PTL/T system is competitive compared with traditional solar energy systems. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Parabolic trough systems are the most used concentrated solar power technology. The operating performance and optical efficiency of the parabolic trough solar collectors (PTCs) are different in different regions and different seasons. To determine the optimum design and operation of the parabolic trough solar collector throughout the year, an accurate estimation of the daily performance is needed. In this study, a mathematical model for the optical efficiency of the parabolic trough solar collector was established and three typical regions of solar thermal utilization in China were selected. The performance characteristics of cosine effect, shadowing effect, end loss effect, and optical efficiency were calculated and simulated during a whole year in these three areas by using the mathematical model. The simulation results show that the optical efficiency of PTCs changes from 0.4 to 0.8 in a whole year. The highest optical efficiency of PTCs is in June and the lowest is in December. The optical efficiency of PTCs is mainly influenced by the solar incidence angle. The model is validated by comparing the test results in parabolic trough power plant, with relative error range of 1% to about 5%. [ABSTRACT FROM AUTHOR]

Parabolic trough systems are the most used concentrated solar power technology. The operating performance and optical efficiency of the parabolic trough solar collectors (PTCs) are different in different regions and different seasons. To determine the optimum design and operation of the parabolic trough solar collector throughout the year, an accurate estimation of the daily performance is needed. In this study, a mathematical model for the optical efficiency of the parabolic trough solar collector was established and three typical regions of solar thermal utilization in China were selected. The performance characteristics of cosine effect, shadowing effect, end loss effect, and optical efficiency were calculated and simulated during a whole year in these three areas by using the mathematical model. The simulation results show that the optical efficiency of PTCs changes from 0.4 to 0.8 in a whole year. The highest optical efficiency of PTCs is in June and the lowest is in December. The optical efficiency of PTCs is mainly influenced by the solar incidence angle. The model is validated by comparing the test results in parabolic trough power plant, with relative error range of 1% to about 5%. [ABSTRACT FROM AUTHOR]

Design, construction, and evaluation of a cylindrical-trough solar concentrator with 1.3m aperture, 2.15m length, and 0.54m focal length, with heat-pipe or vacuum tube receiver and one axis tracking system, are presented. Design performance was tested under ASHRAE standard 93-1986 (RA 91). The concentrator system is lightweight and inexpensive since it was made of polymeric membranes and was pneumatically inflated to acquire its cylindrical shape achieving good optical quality. Further implementation of a flat and a cylindrical extension of the concentrating mirror as secondary mirrors was incorporated into the concentrator design in order to compensate for seasonal variations of collected radiation. Total initial investment of $163.30 or $58.5/m² and efficiencies ranging from 33 to 25% for 25 up to 65°C show an excellent cost-performance ratio. Construction, costs, and efficiencies obtained by us and developed by other groups are compared to emphasize the high cost/benefit ratio and efficiencies of this approach. [ABSTRACT FROM AUTHOR]

Investigation of potential energy solutions paves the way for a more sustainable future by addressing the energy-related climate change effects. This special issue on "Potential Energy Solutions" contains numerous papers selected from the 12th International Exergy, Energy, and Environment Symposium (IEEES-12), which was virtually organized during December 20 to 24, 2020 by Hamad Bin Khalifa University, Doha, Qatar. [Extracted from the article]

SUMMARY In this paper, the mathematical modeling and simulations of a concentrating solar power system located at the Middle East Technical University Northern Cyprus Campus are presented. The system consists of parabolic trough collectors (PTCs), a propane boiler, an organic Rankine cycle (ORC), and a wet cooling tower. Presently, the PTC field is severely undersized with respect to the ORC making the system impossible to operate without burning significant propane. Expanding the solar field could result in better system performance. Hourly, daily and seasonal variations in the performance of this system are simulated using hourly meteorological data for Larnaca, Cyprus, over an entire year. Because the ORC is driven using a relatively low-temperature heat source rather than PTCs, the usage of nonconcentrating evacuated tube collectors that collect both beam and diffuse radiation is explored. The performance of east-west and north-south-tracking axis PTCs and the entire inventory of nonconcentrating evacuated tube collectors that were rated by the Solar Rating and Certification Corporation are compared in terms of annual performance metrics. Based on the simulations, several nonconcentrating evacuated tube collectors are identified with better thermal performance than PTCs, and the feasibility of using these collectors should be explored further. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

SUMMARY Parabolic trough solar collector usually consists of a parabolic solar energy concentrator, which reflects solar energy into an absorber. The absorber is a tube, painted with solar radiation absorbing material, located at the focal length of the concentrator, usually covered with a totally or partially vacuumed glass tube to minimize the heat losses. Typically, the concentration ratio ranges from 30 to 80, depending on the radius of the parabolic solar energy concentrator. The working fluid can reach a temperature up to 400°C, depending on the concentration ratio, solar intensity, working fluid flow rate and other parameters. Hence, such collectors are an ideal device for power generation and/or water desalination applications. However, as the length of the collector increases and/or the fluid flow rate decreases, the rate of heat losses increases. The length of the collector may reach a point that heat gain becomes equal to the heat losses; therefore, additional length will be passive. The current work introduces an analysis for the mentioned collector for single and double glass tubes. The main objectives of this work are to understand the thermal performance of the collector and identify the heat losses from the collector. The working fluid, tube and glass temperature's variation along the collector is calculated, and variations of the heat losses along the heated tube are estimated. It should be mentioned that the working fluid may experience a phase change as it flows through the tube. Hence, the heat transfer correlation for each phase is different and depends on the void fraction and flow characteristics. However, as a first approximation, the effect of phase change is neglected. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]