Summary
According to new findings, the use of clean energy sources such as solar energy to supply energy (both electricity and heat) to human societies is essential. On the other hand, choosing the ...appropriate technology to convert solar energy into useful energy in the form of individual or combined systems is a fundamental issue. Individual solar energy systems have inherently low performance. However, their use in hybrid energy systems with other energy generation devices is key solution and shows high performance. The present work provides the performance of a new combined energy system composed of the parabolic dish solar collector (PDC), Stirling engine (SE) and thermoelectric device (TD) under various parameters. Sun is the main source of energy in this system, where, sunlight is focused on the PDC focal point by the parabolic shaped mirrors. Thus, the useful thermal power is produced by PDC and then feeds to the SE. The operating fluid of the engine is heated by this heat and converted into mechanical energy. Then, the mechanical energy is converted into electricity by a generator connected to the SE and the excess heat is lost from the engine. The exhaust of the SE transferred to the TEG hot end and produces further electricity. In addition, the TEC module absorbs the cooled environment heat and produces cooling energy (by consuming electricity from the TEG). Therefore, the proposed combined process provides the electricity, heat and cooling. The paper is based on the following three scenarios: (1) the system performance is evaluated under constant climatic conditions, (2) climate data from five various cities in Europe and Asia are used for system operation and (3) this scenario presents the general comparison between the two different hybrid energy systems driven by PDC and linear Fresnel reflector (LFR). In addition, multi‐objective optimization is provided to obtain the optimal performance of the developed hybrid system. The optimization results showed that, the optimum total output electricity and overall efficiency were 26.21 kW and 39.17%, respectively. It was also found that, average daily useful power generated by PDC in Moscow on 14‐June is 373.97 W/m2, which is about 11.1%, 1.55%, 33.3% and 14.23% more than Tehran, Beijing, Geneva and Kiev, respectively. Furthermore, increasing the temperature of PDC absorber improves the performance of SE and TD and subsequently improves the overall operation. Also, in terms of the PDC numbers, the system in the cities of Tehran, Beijing and Moscow has a better justification compared to the other two cities (Geneva and Kiev).
Thepresent work provides the performance of a new combined energy system composedof the parabolic dish solar collector (PDC), Stirling engine (SE) andthermoelectric device (TD) under various parameters.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
•Thermal analysis helps to choose the best performance enhancement technique.•Performance augmentation methods try to minimize thermal losses from collectors.•Use of nanofluids significantly enhances ...the thermal performance of collectors.•Integration of collectors with PCMs can both increase efficiency and save energy.
Solar energy as a plentiful and environment-friendly source of energy has an acceptable potential in nearly most of the regions around the world. Thermal technologies are commonly used to provide heat requirements of different domestic, agricultural, residential, and industrial applications from the sun. This paper reviews thermal performance enhancement techniques of the most widely-used low-temperature solar collectors (LTSCs) including flat-plate collectors (FPCs), evacuated tube collectors (ETCs), and compound parabolic concentrators (CPCs) by introducing challenges and discussing future research potentials. In this regard, energy analysis of each collector type along with the latest advancements to boost the heat collection capability of the LTSCs reported in the previous studies is presented. The discussed methods in this study broadly cover structural modifications, absorber coatings, integration with reflectors, using alternative working fluids including nanofluids, and employing thermal energy storage (TES) systems. This comprehensive review is reflecting the level of technical maturity of each type of LTSCs and is expected to serve scientists, engineers, and developers with the latest achievements in this technology.
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GEOZS, IMTLJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Nanofluids as a new generation of fluids have attracted a lot of research works. There is growing evidence that the nanofluids are more suitable for various heat transfer applications than the ...conventional fluids. One of the most important parameters in the thermal behavior of such fluids is the type of nanoparticles dispersed in the base fluid. The present review paper is devoted to provide an overview on the distinct types of particles used in nanofluid research with emphasis on their application in solar collectors. The impact of nanofluids on heat transfer under different dispersive particles is explained for both numerical and experimental researches. Works concerning the application of nanofluids in solar collectors are singled out and analyzed. The nanoparticles are classified into metallic and non-metallic and the various configurations of solar collectors are considered. The review indicates that the flat plate solar collectors are the most investigated among the considered configurations. It is also shown that Al2O3-based nanofluids have been widely considered in these collectors compared to other nanofluids. In addition, the non-metallic based nanofluids can be more useful for the efficiency enhancement of solar collectors compared to metal based nanofluids. Some negative aspects related to nanofluids are also pointed out such as the thermo-physical instability and the reduced efficiency at high nanoparticle volume fraction. Finally, the general conclusions are drawn and future directions for research are proposed. It is noted that the present review concerns the nanofluids based on a single nanoparticle type. Hybrid nanofluids are subject to a future review.
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•Flat plate solar collectors are the most investigated among other configurations.•Al2O3-based nanofluids have been widely considered in solar collectors.•The results of Newtonian and non-Newtonian nanofluids are compared and discussed.•Non-metallic based nanofluids can be more useful for the efficiency of SC.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•Double wall tube and PCM are the keys of the developed compact solar collector.•The compact solar collector has a favorable performance compared to FSWHS.•Fins enhance the heat transfer ...characteristics during the simultaneous operation.•Fins assist in keeping the PCM profile almost uniform.
Space and weight requirements coupled with time delay between energy production and consumption represent great barriers toward further deployment of typical solar water heating systems in existing buildings with limited space. Therefore, a new compact U-pipe evacuated tube solar collector (ETC) integrated with paraffin wax (ALEX WAX 600) for energy storage is presented in the current study. The ALEX WAX 600 is an organic chemical-based phase change material (PCM) having an average melting temperature of 60°C and a thermal conductivity of 0.21W/mK. The key issue of the developed system is the elimination of entire systems components by storing the energy in the evacuated tube itself through the usage of paraffin wax. Due to the low thermal conductivity of paraffin wax, heat transfer plate (fin) with an area of 0.1251m2 is integrated in the proposed system. The present study investigates the developed system under two configurations; un-finned and finned U-pipe evacuated tube solar collector side by side with a typical forced recirculation solar water heating system (FSWHS) under the same operation and weather conditions. The operation of the solar water heating systems is studied during the on-demand operation under a simultaneous operation and a real water consumption profile. The results clarify the favorable performance of the developed compact solar water over the typical FSWHS during different operation scenarios and weather conditions due to their low thermal inertia. Furthermore, the utilization of fin in the developed system has a substantial effect on improving the heat transfer characteristics of the PCM and enhances the overall system stability. During simultaneous operation tests, the total effective energy discharged for the un-finned system is higher than FSWHS by 35.8% under clear day weather conditions. However, the finned system is higher than FSWHS by 47.7%. The simultaneous long-term predictions based on regression modeling show that the average annual efficiency is 71.8%, 85.7% and 40.5% for the un-finned, finned and FSWHS systems, respectively. During real water consumption profile tests, the daily system efficiency is, 33%, 26% and 20% for the un-finned, finned and FSWHS systems.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Among different sources of renewable energy, solar energy is widely used almost exclusively because of its ease of availability and its lowest environmental effects. The most commonly used solar ...collectors are the flat plate solar collectors (FPSCs). However, they are less powerful (low capacity to convert solar energy to thermal energy). It is possible to classify the use of nanofluid on FPSCs as an efficient way to boost the solar collectors’ performance. In this paper, studies on metal oxides, non-metal oxides, solid metals, semiconductor nanomaterials, carbon nanostructured, and nanocomposite nanofluids used as heat transfer fluids (HTFs) within FPSCs are examined sequentially. Various parameters affecting the FPSC’s thermal efficiency, such as nanoparticle type, nanoparticle concentration, nanoparticle size/shape, solar radiance, and mass flow rate, are extensively analyzed. Studies have also compared various types of single nanofluids or mixture nanofluids with FPSCs under the same operating conditions. It is found that the use of carbon-based nanofluids compared to metal oxides of nanofluids under the same conditions has resulted in a major improvement in the energetic and exergetic performance of the FPSC. Furthermore, the reviewed research revealed that there is a tremendous opportunity to achieve the commercial application of carbon-based nanofluid FPSC. The obstacles and opportunities for further study are also highlighted.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•Single-layer graphene and GO nanofluids were designed for solar thermal application.•Uniform temperature distribution is achieved in nanofluids based on the RI-DASC mode.•The photothermal conversion ...efficiency of SLG is 49.13% at 100 ppm in the RI-DASC mode.•The photothermal conversion efficiency of GO reaches 46.26% at 100 ppm in the RI-DASC mode.
Direct absorption solar collectors (DASC) are extremely attractive in solar energy utilization. In this paper, starting from these two aspects, graphene-based nanofluids, including single-layer graphene (SLG) and graphene oxide (GO), are prepared to enhance solar absorption and photothermal conversion performance. The influence of nanofluids' concentration and two different irradiation modes: traditional DASC and reverse radiation DASC (RI-DASC) on the photothermal conversion performance of graphene-based nanofluids has been studied. The addition of a small amount of SLG or GO significantly improves the photothermal conversion efficiency of base fluid, and it increases along with the increase of the concentration. Furthermore, the RI-DASC mode has a more uniform thermal field distribution and the higher photothermal conversion efficiency than the DASC mode. In DASC mode, the photothermal conversion efficiency of pure water is 17.00%. By changing the irradiation mode, the introduction of GO and SLG nanofluids (100 ppm) increased the photothermal conversion efficiency by about 172% and 189%, reaching 46.26% and 49.13%. According to the photothermal-thermoelectric conversion experiment, the positive correlation between the output power of the TE module and the heating state of the nanofluid makes it possible to adjust the nanofluid in real-time. This work presents a feasible way to enhance solar energy absorption and improve the photothermal conversion efficiency of nanofluids for DASC.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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•Investigated the effect of using heat pipe solar collector integrated with pyramid-shaped solar still.•Conducted the effect of using water and ethanol as working fluid.•An optimal ...filling ratio was 40%.•The maximum hourly and accumulated yield were 1235 and 6970 ml/m2, respectively.•The cost of produced fresh water was 0.0137 $/l.
In this paper, a modified pyramid-shaped solar still (MPSS) including a conventional pyramid-shaped solar still (CPSS) integrated with a heat pipe solar collector (HPSC) was fabricated and experimentally assessed in the outdoor conditions of Mashhad, Iran (latitude of 36°18', longitude of 59°34'). Two different working fluids (water and ethanol) were used at three different filling ratios (FRs). Results showed that using the HPSC increased the temperature difference between the glass cover and the basin water. Therefore, using the HPSC augmented the hourly and accumulated yield. The accumulated yield was escalated to 6970 and 3300 ml/m2 for the MPSS (with water as the working fluid at the FR of 40%) and the CPSS, respectively. Moreover, the HPSC increased exergy, although the instantaneous efficiency was rather invariant. Based on the experimental data the values of the total internal heat transfer coefficient have been calculated. Furthermore, the best performance of the MPSS was obtained with water as the working fluid at the FR of 40% whereas ethanol at the FR of 40% also showed a very good performance. Finally, the economic analysis revealed that the MPSS was economically reasonable and an estimated cost for 1 L of distillate was 0.0137 $ for the proposed MPSS.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The present work analyzes the performance of unshielded receiver tube integrated solar parabolic trough collector where Al.sub.2O.sub.3/deionized (DI) water nanofluid of low concentrations was used ...as heat transfer fluid (HTF) element. Nanofluid is synthesized at various volume fractions starting from 0.2 to 1.0% with surfactant-free condition, by ultrasonic technique. Several researchers investigated the performance of higher nanofluid concentrations (1.0-5.0%) with and without surfactants on parabolic trough solar collector. The outdoor experiments are conducted for two HTF flow rates of 0.010 kg s.sup.-1 and 0.015 kg s.sup.-1. When the nanofluid is subjected as HTF, the DI water acted as a base fluid. While DI water is allowed to flow through the absorber, it performs both as HTF and heat storage fluid. The synthesized nanofluid at various volume fractions is allowed to flow through the receiver for the purpose of analyzing the thermal performance and compare the results with DI water. The collector efficiency increases with the mass flow rate as well as the concentration of nanofluid. For 0.015 kg s.sup.-1, the maximum efficiency was calculated as 59.13% (hourly) and 58.68% (average).
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
•Proposal of a novel cogeneration of power, cooling, and heating using solar energy.•Utilization of zeotropic mixtures for efficiency improvement.•Evaluation of the system performance from the energy ...and exergy viewpoints.•Highest exergy and energy efficiencies of 20.26% and 15.81%.
In this study, a novel power, cooling, and heating cogeneration system was devised. In the proposed system, parabolic trough solar collectors were used as the primary energy source. Also, the zeotropic mixtures were employed as the working fluid of the dual-pressure organic Rankine and ejector refrigeration cycles for efficiency improvement. The system was analyzed from the energy and exergy viewpoints in MATLAB software using library data of Refprop and Coolprop toolboxes for obtaining the thermodynamic properties of working fluids. The best performance of the system was obtained under some circumstances, including a constant rate of solar radiation (DNI) as 1000W·m-2 and using 410 solar collectors with an area of 28976m2, and employing Pentane (0.5)/Trans-2-Butene (0.5) and Isobutane (0.2)/Isopentane (0.8) as the zeotropic working fluids in the dual-pressure organic Rankine cycle and the ejector refrigeration cycle. In these conditions, the electrical power, cooling load, and heating capacity were calculated by 4082.6kW, 51.52kW, and 1 616.4kW. Also, total exergy loss of the system was obtained by 22.19MW, and the highest exergy and energy efficiencies were computed by 20.26% and 15.81%, respectively.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
This paper addresses the design and specification of solar collector networks for the capture of solar radiation and its transformation into thermal energy for use in low energy intensity processes. ...All glass evacuated tube solar collectors are the type of technology considered in this work. Target temperature and heat load are the design objectives in the design of solar collector networks and they are achieved by specification of two design variables, namely: a) number of collectors in series in a row and, b) number of rows in parallel. The variability of ambient conditions is accounted for by means of the specification of the critical point conditions for the design of the network. From the thermal point of view, the number of solar collectors or heat transfer surface area required to achieve the targets depends on the ambient conditions chosen for the design. The targeting approach for the specification of the network structure is based on the use of a thermal model. The various design options available to the designer to specify the number of solar collectors in a row, are presented in a graphical way as a function of mass flow rate, inlet temperature, solar radiation intensity and target temperature.
•Methodology for the design and specification of networks of solar collectors.•Thermal model for the determination of outlet temperature of evacuated tube collectors arranged in series.•Parameter plots are derived for the design of networks of solar collectors.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
