Article

A comprehensive review of Scheffler solar collector

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Abstract

A Scheffler collector is a fixed focus solar radiation concentrator. It has capacity to increase the temperature of the receiver up to 200 °C. It is being widely used in the various applications such cooking food, generation of power in the solar thermal power plant and etc. This communication presents a complete review of the Scheffler collector. The first part reviews a complete designing of a Scheffler collector with respect to the equinox by selecting a specific lateral part of a paraboloid. The next part compares the energy and exergy analysis of the Scheffler collector followed by the various applications of Scheffler collector and its recent developments.

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... One of most studied solar irradiation collectors is known as parabolic dish or Scheffler collector. The Scheffler solar collector consists of a parabolic dish that tracks sun movement to concentrate its irradiation into a focal area that can be used for heating to achieve up to 700 C (A. Kumar et al., 2017;Tian & Zhao, 2013). The main components of this collector include parabolic frame, small reflectors placed on internal surface of parabolic frame, and a support that can be adjusted coupled to a system to track sun position (Kumar et al., 2017;Panchal et al., 2020). ...
... The Scheffler solar collector consists of a parabolic dish that tracks sun movement to concentrate its irradiation into a focal area that can be used for heating to achieve up to 700 C (A. Kumar et al., 2017;Tian & Zhao, 2013). The main components of this collector include parabolic frame, small reflectors placed on internal surface of parabolic frame, and a support that can be adjusted coupled to a system to track sun position (Kumar et al., 2017;Panchal et al., 2020). ...
... The parabolic frame assists in the physical support that gives the expected shape to the sun collector, which essentially leads to creation of a focal area for sun irradiation beams. The design and calculation to design the parabola can be found elsewhere (Kumar et al., 2017). Small glass mirrors are commonly used as reflectors due to their satisfactory optical (especially with high reflectance) and energy-related properties (Isravel et al., 2020;Patel & Patel, 2022). ...
Chapter
The use of sun irradiation to power hydrodistillation units is an emerging technology with promising application to obtain essential oils and hydrosols. The current diversity of sun collectors is an important aspect about the versatility of this emerging technology for direct (parabolic collectors) and indirect (flat plate collectors) use of energy obtained from the sun. The two main products generated from solarassisted hydrodistillation, essential oil and hydrosol, have received increasing attention in the last decade. Studies with essential oils have produced important advances regarding the general understanding of the process, processing variables, and factors to be monitored and controlled prior to and during the extraction process. In the case of hydrosols, scientific evidence is emerging, and more studies are expected to be developed in the upcoming years. In this context, the case study presented in this chapter, and related scientific evidence can assist in the generation of more knowledge about hydrosol production and sustainable actions to extract bioactive compounds and promote societal and economic development. However, advances are still necessary to advance the design of sun collectors and improve their thermal efficiency and capacity to overcome current challenges for sun collectors in general, such as operation under low sun irradiation incidence, operation on suboptimal temperatures, and accumulation of dust. Configuration of the entire system is also expected to solve the current issues in terms of batch size, for instance. Additionally, the study of nonexplored sources for essential oil production is also interesting to generate knowledge about the solar-assisted hydrodistillation and produce new ingredients with potential biological effects.
... Review of thermodynamic studies [20][21][22][23] included the figure of merit, energy and exergy analyses. Only two review articles [24,25] on Scheffler cooker are available in the open literature since it is a commercial version. The major application of Scheffler collectors is institutional/community cooking, wherein multiple collectors are connected through a pumping network to generate steam. ...
... Unlike thermosyphon systems (heat transportation to indoor/shaded area through different passive devices), Scheffler concentrators (Wolfgang Scheffler [71], 1982) direct the solar flux into the indoor kitchen. Although a reasonable number of Scheffler cookers are installed worldwide, open literature is scanty (reported by Kumar et al. [24]) as it is a commercial variant. Hence both Scopus and non-Scopus literature have been reviewed here. ...
Article
A significant amount of domestic energy consumption is for cooking in the majority of the countries. However, open fire cooking using wood and charcoal releases harmful climate-warming emissions. Thus, developing a clean cooking technology is the need of the hour, which includes electric and solar cookers. In most cases, the former technique involves converting thermal energy to high-grade electrical energy and converting it back to thermal energy is energy-splurging, if not criminal wastage of energy. The latter option uses either non-concentrated or concentrated solar thermal energy directly for cooking and, therefore, is more efficient (as high as optical collection efficiency) besides helping reverse global warming. Low-cost solar cookers for outdoor cooking have been available for a long time. However, it has low social acceptance due to the inconvenience of cooking outdoors rather than in the kitchen and the inability to cook during off-sunshine hours. Hence, in line with the current need, this review explores numerous designs of solar cookers intended for indoor usage, which includes thermosyphon systems, Scheffler cookers, pumped systems, and other innovative designs. Most of the designs reviewed are operated in a shaded area rather than a true indoor system. Although pumped systems solve this issue, the auxiliary power requirement and reliability are questionable. Hence, a few designs are handpicked for their novelty and ease of indoor cooking. Solar chulha, being one of them, has great prospects as the design involves a sustainable mechanism for round-the-clock indoor solar cooking.
... Among the non-conventional sources of energy solar energy have been always at the center of attention. Studies suggest that "the total amount of energy received by earth from the sun in an hour is more than the energy consumed in one year" [16].Solar energy is used all over the world for generation of electricity or heating. Nowadays solar photo-voltaic panels are widely used to convert solar energy directly to electricity and studies suggest that in 2014, "worldwide installed PV capacity increased to at least 177 gigawatts (GW), sufficient to supply 1 percent of global electricity demands" [30]. ...
... Scheffler Collectors which are fixed focus radiation concentration are able to increase the temperature of the receiver up to 200 C. The majority of studies conducted on Scheffler have concentrated on its application for cooking and making hot water [27,21,8,7,24,31,34,9,33,16]. Some studies have compared the priorities of Scheffler cooking system and other types. ...
Chapter
Scheffler solar reflector has been used internationally more than two decades. invented by Wolfgang Scheffler. This collector harvests the solar energy and has a fixed focal point and sun tracking system. the current study aims to conduct a exhaustive review on Scheffler solar collectors and its implications. Scheffler fixed focus concentrators, Parabolic Scheffler reflectors, Techniques used in Scheffler, Applications, Concentrated Solar Power (CSP), Concentrated Solar Technologies (CST), and Design Factors of Scheffler are areas this study focus.
... Among the non-conventional sources of energy solar energy have been always at the center of attention. Studies suggest that "the total amount of energy received by earth from the sun in an hour is more than the energy consumed in one year" [16].Solar energy is used all over the world for generation of electricity or heating. Nowadays solar photo-voltaic panels are widely used to convert solar energy directly to electricity and studies suggest that in 2014, "worldwide installed PV capacity increased to at least 177 gigawatts (GW), sufficient to supply 1 percent of global electricity demands" [30]. ...
... Scheffler Collectors which are fixed focus radiation concentration are able to increase the temperature of the receiver up to 200 C. The majority of studies conducted on Scheffler have concentrated on its application for cooking and making hot water [27,21,8,7,24,31,34,9,33,16]. Some studies have compared the priorities of Scheffler cooking system and other types. ...
Conference Paper
Scheffler solar reflector has been used internationally more than two decades. invented by Wolfgang Scheffler. This collector harvests the solar energy and has a fixed focal point and sun tracking system. the current study aims to conduct a comprehensive review on Scheffler solar collectors and its implications. Scheffler fixed focus concentrators, Parabolic Scheffler reflectors, Techniques used in Scheffler, Applications, Concentrated Solar Power (CSP), Concentrated Solar Technologies (CST), and Design Factors of Scheffler are areas this study focus.
... En effet, c'est une source d'énergie abondante, propre et inépuisable à l'échelle humaine [9]. L'énergie solaire peut être convertie en énergie électrique via deux technologies : les panneaux solaires photovoltaïques (PV) et les centrales solaires à concentration (CSP) [10]. Le rendement électrique des panneaux PV reste toujours faible et se situe entre 14 à 20% [11]. ...
Thesis
Solar tower power plant (STPP) requires high concentration ratio to provide high temperature for power generation. The main objective of this work is to use three-dimensional compound parabolic concentrator (3D-CPC) to increase the concentration ratio into the receiver. To achieve this objective, we determined at first the sizes and made the design of the STPP subsystems. We modelled then the solar field in SolTrace using a developed and validated optical model. After that, we studied the heat transfer inside the receiver using a developed and validated CFD model. Finally, the energy performance of the electrical conversion system (ECS) of the STPP is determined by thermodynamic models. We performed the simulations during the solstices and the equinoxes. The results obtained showed that the solar field consist of 175 heliostats with a surface area of 2 m2 and a height of 1.5 m each. The optimal configuration of the 175 heliostats showed that the field is made up of 14 rings divided into 7 main rings and 7 staggered rings. The 3D-CPC truncated at 35° increased the concentration ratio by a factor of 4.90 for an optical efficiency of 82.15%. The ECS provided a thermal efficiency of 37.92% and a solar-electric efficiency of 26.97% for an outlet temperature of the receiver of 1301 K. The results obtained in this work showed that the 3D-CPC increased the concentration ratio into the receiver. Thus, it improved the thermal performances of the receiver and consequently, the energy performances of the STPP.
... Solar energy has the potential to reduce GHG emissions for environmental preservation and increase access to reliable electricity in Sahelian countries like Senegal [12]. Solar energy can be transformed into electricity through two technologies: Photovoltaic (PV) and Concentrating Solar Power (CSP) plants [13,14]. Research indicates that CSP technologies generate electricity more efficiently than PV technologies [15]. ...
Article
The operation of Solar Tower Power (STP) plants requires high solar concentration for power generation. In this study, a Three-Dimensional Compound Parabolic Concentrator (3D-CPC) is used to increase the solar concentration within the receiver and thereby enhancing its thermal performance and, consequently the energy performance of the STP plant. To attain this objective, the solar field is sized for an electrical power of 30 kW. The heliostats are arranged in the field using the radial staggered layout design as seen in PS10 plant. The 3D-CPC is sized, designed and incorporated at the receiver inlet. The solar field is modelled in SolTrace software using an optical model that was developed and validated to gather the average solar flux absorbed by the receiver. In order to ascertain the thermal performance of the receiver, a Computational Fluid Dynamics (CFD) model is created using the volumetric heat source produced from the absorbed solar flux, and then validated to study the heat transfer into the receiver. Subsequently, the energy performance of the STP plant is assessed. The results showed that the solar field consists of 175 heliostats. Each heliostat has a surface area of 2 m² and a height of 1.5 m. Furthermore, the 3D-CPC enhances solar concentration in the receiver by a factor of 4.90, yielding an optical efficiency of 82.15%. Additionally, outlet air temperatures of the receiver were higher than those obtained with the conventional Capstone (C30) turbine. For instance, during the summer solstice, the outlet air temperature of the receiver was 1332.77 K and there was a Direct Normal Irradiation (DNI) of 549.64 W/m2, resulting in 39.68% and 28.32% thermal and solar-electrical efficiencies, respectively
... Thousands of years are required for the formation of fossil fuels and a rapid rate of their consumption can results in their depletion. Alternates of these energy should be searched in order to meet the essential energy requirement of the people [3]. Renewable sources of energy especially solar energy can be good options, which are clean in nature and do not pollute the environment [4]. ...
Chapter
Renewable and sustainable energy Book series aims to bring together leading academic scientists, researchers and research scholars to publish their experiences and research results on all aspects of Renewable and sustainable energy. It also provides a premier interdisciplinary platform for researchers, practitioners and educators to present and discuss the most recent innovations, trends, and concerns as well as practical challenges encountered and solutions adopted in the specified fields. High quality research contributions describing original and unpublished results of conceptual, constructive, empirical, experimental, or theoretical work in all areas of Renewable and sustainable energy are cordially invited for publication
... The flat receivers are found to have lower thermal efficiency as compared to cavity receivers [17]. However, the Scheffler dish is a low cost with ease of construction, and superior efficiency as compared to a parabolic dish [17][18][19]. The research has demonstrated that a cavity receiver with a Scheffler dish outperforms a flat receiver thermally [22][23][24]. ...
... For example, heating devices like solar collectors, which use solar energy to warm water or air, are eco-friendly options. [12][13][14] The main problem of solar systems is that weather acts as a restrictive factor. [15] Heat pumps are a promising alternative since they take heat from the surroundings, reducing the total energy consumption of the heating system. ...
Preprint
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The building climate industry and its influence on energy consumption have consequences on the environment due to the emission of greenhouse gasses. Improving the efficiency of this sector is essential to reduce the effect on climate change. In recent years, the interest in porous materials in applications such as heat pumps has increased for their promising potential. To assess the performance of adsorption heat pumps and cooling systems, here we discuss a multistep approach based on the processing of adsorption data combined with a thermodynamic model. The process provides properties of interest, such as the coefficient of performance, the working capacity, the specific heat or cooling effect, or the released heat upon adsorption and desorption cycles, and it also has the advantage of identifying the optimal conditions for each adsorbent-fluid pair. To test this method, we select several metal-organic frameworks that differ in topology, chemical composition, and pore size, which we validate with available experiments. Adsorption equilibrium curves were calculated using molecular simulations to describe the adsorption mechanisms of methanol and ethanol as working fluids in the selected adsorbents. Then, using a thermodynamic model we calculate the energetic properties combined with iterative algorithms that simultaneously vary all the required working conditions. We discuss the strong influence of operating temperatures on the performance of heat pump devices. Our findings point to the highly hydrophobic metal azolate framework MAF-6 as a very good candidate for heating and cooling applications for its high working capacity and excellent energy efficiency.
... This problem of fuel can easily be solved with the help of solar energy. Solar energy is a form of energy that is present in abundance in the Sun [3]. Sun is the best source of energy in the world. ...
Article
Full-text available
The Solar energy is a non-exhaustible type of energy that serve to the survivability of mankind and all the living beings on the earth. In recent time due to increase in population density and rapid urbanization, the entire world is facing enormous environmental challenges such as global warming, air pollution, imbalance of ecology, and many more. There is a necessity to sustain natural endowments with the help of advanced materials and technologies. In the research domain, the majority of them are looking for a mechanism that can be used for harnessing solar energy. Many types of solar devices such as solar panels, solar heaters, solar concentrators, etc. are in practice. The Scheffler reflector is used for the harness of solar energy at an advanced stage. Addition of a thermal storage unit in the Scheffler system, heating performance can be enhanced by extending the heat storage time. In this study, a comparative analysis of the thermo-physical properties of nine Latent Heat Storage (LHS) storage materials (generally used in solar applications) is carried out using three MCDM techniques: analytical hierarchy process, TOPSIS, and weighted sum model. These techniques are very useful in solving such problems, where we need to select the best option amongst the group having similar characteristics. Materials taken for the study are as: Di-Sodium Hydrogen Phosphate Do-decahydrate (Na2HPO412H2O), Erythritol, Stearic Acid, Acetamide, Calcium Chloride Hexahydrate (CaCl26H2O), Magnesium chloride hexahydrate (MgCl26H2O), Malic Acid, Palmitic acid, and Lauric Acid. Results show that the three techniques are nearly yielding the same (slight deviation) ranks of the top materials (rank 1; Erythritol, rank 2; Stearic acid and rank 3; Na2HPO412H2O) which can be used in Scheffler reflector for using the heat up to a longer period of time. This research work is novel in the sense that the selection of LHS material for Scheffler reflector using MCDM hybrid model is carried out for the first time. LHS material demand is expected to increase over time due to its more consciousness and stronger regulatory frameworks. Other MCDM techniques can be applied to select the best thermo-chemical substances which improve the heat-carrying capacity of the Scheffler reflector.
... The stress analysis were studied and optimize the dimension of dish. Anil Kumar et al. [18] reported a step by step procedure for designing of reflector parabola and comparative study of energy and exergy analysis was conducted. They calculated thermal efficiency with receiver capacity upto 200 0 C for medium temperature applications. ...
Conference Paper
Full-text available
In this paper 16m² paraboloidal dish is utilized to identify the thermal performance of the system for low and medium temperature applications, with the improved absorber material on the reflector dish surface. To identify thermal aspects, the experimental setup consists of paraboloidal reflector dish, receiver with 0.5m diameter, steam-water separator, electric calorimeter and condenser. The experimentation conducted during normal sunny days when the sky is clear with no clouds and radiation intensity above 550W/m². The scheffler dish frame is made of mild steel and channel structure is of aluminium to withstand wind speed during the operating conditions. To fix the glass mirror on the support structure, an industrial adhesive and fasteners are used to ensure the perfect fixing of the mirror and after ensuring equinox position of the support structure. The glass is 100 mm X 100 mm in size for easy handling and fixing on the aluminium channel with the help of silicon paste. The glass was coated with 0.5mm thick aluminium reflector with reflectivity of 85%. The thermal efficiency obtained 56.38% when net incident beam radiation of 604W/m². With the use of aluminium reflector on the surface of glass mirror, to enhances the performance of the system significantly.
... In current scenario focus has been shifted to the small distributed roof mounted systems rather than a huge concentrated station [10,11,12]. Hence there is a great scope of development and utility of small sized parabolic trough heat generation systems which can be installed on roof of a process industry to serve its medium temperature heat requirements [13]. In contrast to large sized parabolic troughs having width in the range of 6-9 meters, medium temperature troughs require smaller troughs with 1-3 meters of width [14]. ...
Article
Full-text available
The worldwide energy demand is rapidly increasing, increasing in turn the necessity of power generation. The generated power is used to fulfill domestic and industrial needs. Industries use electricity for medium scale heating applications, which is the worst use of electricity. Concentrated solar power can prove itself a superior alternative of electrical heating load, being the only technology which produces high quality heat. In this paper, a systematic design approach of a parabolic trough based solar field for a defined thermal load is presented. The performance simulation of the field has been done for a small scale, medium temperature industrial drying process of 290 kWth at 120oC, located in Bhopal using System Advisor Model (SAM), was found to be 23% efficient. The results can be used as a roadmap for designers for the feasibility analysis of local industrial application
... PDC consist of a parabolic reflector dish focusing sunlight onto the receiver, consisting in a cylindrical cavity with an absorbing plate. Several PDC designs can be found in the market, such as the ARUN dish [60], the Scheffler dish [61,62] or the TCT-RED proposed by Thermal Cooling Technology® (Fig. 3c) [40]. In India, PDC is the leading solar technology supplying heat for community cooking and industrial process heat, with 88 projects installed during 2017 [64]. ...
Article
Full-text available
Solar energy is expected to play an important role in the decarbonization of the energy and industrial sectors. Low and medium temperature (<400 °C) solar thermal collectors have proved to be a reliable solution to supply heat and decarbonize the industrial sector, with over 800 Solar Heat for Industrial Processes (SHIP) plants put in operation in the last decade. Governmental support policy is a key factor for solar thermal energy to play a major role in CO2 emission reduction, which require improving the efficiency of solar collectors and reducing costs. Recent studies have demonstrated the potential of nanoparticles to enhance the optical properties of heat transfer fluids for direct absorption solar collectors (DASC). In a DASC the transfer fluid absorbs volumetrically the incident radiation, resulting in a more homogeneous temperature distribution and less heat losses than in conventional surface collectors. In this paper, the current state-of-the-art of SHIP installations and conventional surface collectors is presented, and a critical literature review dedicated to nanofluid-based DASC for both concentrating and non-concentrating collectors is provided. The key findings and the challenges to be overcome toward promoting the development of nanofluid-based DASC for SHIP applications are discussed.
... However, this problem was solved by using a fixed focus Scheffler solar concentrator, which automatically allows accurate tracking and keeps the path of the incident radiations away from the focus of the receiver [26]. Moreover, its manufacturing work can be performed in a simple workshop with minimal tooling, providing more cost-effective solutions for small-scale applications in the food and agroindustries [28]. Therefore, a Scheffler concentrator reflector with an area of 8 m 2 was used as a source of solar thermal energy for coffee roasting experiments. ...
Article
The energy and exergy based thermal analysis was conducted on a newly developed solar coffee roasting system. The system is comprised of a rotating drum (diameter: 400 mm × length: 400 mm), electric motor with variable frequency drive, cooling tray (diameter: 500 mm × height: 100 mm), fan blower, and coupled with a heating source i.e., Scheffler fixed focus solar concentrator (8 m2). Experiments were conducted using 2 kg coffee beans (variety Coffea arabica L.). The results revealed that the system is capable to process the complete batch in 21±1 minutes at the temperature of 250 oC at corresponding solar radiations in the range of 800-850 W/m2. The specific product energy was calculated to be 1543 kJ/kg. The average exergy input, out, and loss of the solar roasting system were found to be 83.98, 47.58, and 36.40 kJ/kg, respectively. The results show that the average exergy efficiency and improvement potential factor of the solar roaster were 56.28% and 22.59 kJ/kg, respectively. Out of total available power (3680 W) at the solar reflector, 66% of energy was available for roasting coffee. The findings of this study show that the developed system could be a valuable tool for design and optimization of the energy distribution and losses at various components of the solar roasting system.
... Public awareness on solar energy has been raised over the past years raised as a result of environmental catastrophes and imbalanced energy prices. Thermal energy production from concentrating sunlight offers a promising alternative to fossil energy and will lead to a significant reduction off fossil fuel usage in global energy source preferences [1]. Being one of the most useful ways of energy production, gaining heat through concentrating sunlight to a point by a dish collector has been valued by the experts in the field [2]. ...
... Kumar et al. compared the thermal performance of various types of cookers and made the conclusion that Scheffler community type cooker is better than others in terms of exergy [10]. Prakash et al. carried out a comprehensive review of Scheffler solar collector and emphasized its various applications and recent developments [11]. The parametric analysis of a solar dish collector was carried out in details by Stefanovic et al. in order to find out the optimum fluid temperature and flow rate [12]. ...
Conference Paper
In the present study, an attempt is made to analyze the thermal performance of a prototype solar cooking system being widely used for commercial purpose. In this context, a prototype solar cooking system consisting of a Scheffler concentrator with a dome shaped receiver is designed and tested. Numerical analysis of a 2D model of a dome shaped receiver is carried out to investigate its performance and effect of mass flow rate on outlet temperature is studied at different fixed surface temperatures. Numerical results are observed and validated with experimental results.
... Energy from the concentrated rays is transferred to the heat transfer fluid (HTF) circulating through the receiver fixed at the focus. CSP is becoming a promising technology for thermal applications (Kumar et al., 2017). Depending upon the temperature requirement line focus or point focus, solar concentrators are used. ...
... Energy from the concentrated rays is transferred to the heat transfer fluid (HTF) circulating through the receiver fixed at the focus. CSP is becoming a promising technology for thermal applications (Kumar et al., 2017). Depending upon the temperature requirement line focus or point focus, solar concentrators are used. ...
Article
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Abstract: In this work, Scheffler dish with improved design of the receiver isused for direct steam generation. Experiments were conducted from Februaryto May 2019, for monthly performance assessment of 16 m2 Schefflerconcentrator. Effect of varying aperture area, solar beam radiation, ambienttemperature and wind speed on the thermal efficiency of the system isinvestigated. The average receiver temperature at focus observed to be 323ºCwith average beam radiation 656 W/m2. From the results, the thermal efficiencyof the system is reduced by 2.36% with a decrease in aperture area from12.82 m 2 to 9.59 m2. The average thermal efficiency of the system decreasedlinearly from 57.29% to 39.99% with an increase in wind speed from 0.5 m/s to6 m/s where as it reduced by 1.13% with an increase in ambient temperaturefrom 24ºC to 46ºC (PDF) Parametric analysis of Scheffler concentrator with convex receiver for direct steam generation. Available from: https://www.researchgate.net/publication/350033192_Parametric_analysis_of_Scheffler_concentrator_with_convex_receiver_for_direct_steam_generation [accessed Apr 29 2022].
... Photovoltaic panels use solar irradiations and produce electricity. Moreover, during this electricity production process, a considerable amount of waste heat is also generated which can be taken its benefit by integrating a network of tubes which containing a fluid for heat transfer process (Ahmad, Saidur, Mahbubul, & Al-Sulaiman, 2017;Kumar, Prakash, & Kaviti, 2017). ...
Article
Full-text available
In this study, machine learning methods of artificial neural networks (ANNs), least squares support vector machines (LSSVM), and neuro-fuzzy are used for advancing prediction models for thermal performance of a photovoltaic-thermal solar collector (PV/T). In the proposed models, the inlet temperature, flow rate, heat, solar radiation, and the sun heat have been considered as the input variables. Data set has been extracted through experimental measurements from a novel solar collector system. Different analyses are performed to examine the credibility of the introduced models and evaluate their performances. The proposed LSSVM model outperformed the ANFIS and ANNs models. LSSVM model is reported suitable when the laboratory measurements are costly and time-consuming, or achieving such values requires sophisticated interpretations.
... In solar steam cooking system, the solar radiation falls on a solar concentrator, water become steam at high T&P, which is taken to the kitchen using insulated pipes. [11][12][13][14] The solar concentrators being propagated in the country are single axis TFFS dish and dual axis TFP (ARUN© Dish). (15,16) A solar cooking system of community size consists of number of automatically TPRs (Scheffler dish), assembled in series and parallel combinations to generate steam for cooking food for thousands of people twice a day without polluting environment with in short period of time. ...
Article
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Large amount of conventional fuels like coal, wood and LPG are being used for community cooking resulting emission of greenhouse gases. Concentrating type parabolic dish can generate temperature upto 350-4000C thus, suitable for cooking purposes. The solar steam cooking system can cook food for 50 - 25,000 persons daily. A number of solar steam cooking systems installed at various institutions have been presented. Keeping this in view, a solar steam cooking system for 1500 students is being proposed at Dr Y S Parmar University of Horticulture & Forestry, Nauni campus. Design specifications and possible applications have also been presented.
... Different solar thermal collectors are available to concentrate the solar energy at a point. Parabolic dish collectors are being used widely for medium and high-temperature heat applications [8], [9]. Scheffler concentrator is one of the efficient and low maintenance systems for steam-based applications [10]. ...
Article
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Blanching is an important stage of post harvesting processing of turmeric, which destroys the viability of the fresh rhizomes and eliminates the raw odor. Large amount of crop residue and wood is consumed during conventional turmeric boiling process. Solar-based turmeric blanching system had been developed to show the viability of concentrated solar power for agricultural produce processing and contribute to CO 2 mitigation. Experiments were conducted for several days in the month of April 2019, to study the performance of 16-m ² Scheffler concentrator for turmeric blanching. Turmeric was blanched in batches of 10 kg. Average 110 kg turmeric was successfully processed in a day. From the experimental data analysis, it is perceived that the thermal performance of the system directly depends on beam radiation. Average efficiency of 19.35 % was achieved with average beam radiation 721 W/m ² . Minimum blanching time was found as 27 minutes with an average steam flow rate 5.30 kg/hr. Power available at reflector, receiver, and blanching vessel is presented to identify energy losses at each component of blanching system.
... Photovoltaic panels use solar irradiations and produce electricity. Moreover, during this electricity production process, a considerable amount of waste heat is also generated which can be taken its benefit by integrating a network of tubes which containing a fluid for heat transfer process (Ahmad, Saidur, Mahbubul, & Al-Sulaiman, 2017;Kumar, Prakash, & Kaviti, 2017). ...
Preprint
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Solar energy is a renewable resource of energy that is broadly utilized and has the least emissions among renewable energies. In this study, machine learning methods of artificial neural networks (ANNs), least squares support vector machines (LSSVM), and neuro-fuzzy are used for advancing prediction models for the thermal performance of a photovoltaic-thermal solar collector (PV/T). In the proposed models, the inlet temperature, flow rate, heat, solar radiation, and the sun heat have been considered as the inputs variables. Data set has been extracted through experimental measurements from a novel solar collector system. Different analyses are performed to examine the credibility of the introduced approaches and evaluate their performance. The proposed LSSVM model outperformed ANFIS and ANNs models. LSSVM model is reported suitable when the laboratory measurements are costly and time-consuming, or achieving such values requires sophisticated interpretations.
... b Scheffler dish (Chandrashekara and Yadav 2017) purposely used for specific requirements in industries, commercial and residential complexes. Its tracking system takes care of the direction and inclination of the dish, keeping its focus onto the receiver only (Kumar et al. 2017). Though these types of solar collector systems are generally used for medium-to high-temperature thermal applications, they require larger area and infrastructural support. ...
Article
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World climate is an area of concern due to the use of fossil fuels that have been the most commonly preferred resource of energy since the industrial revolution and urbanization. The target to maintain the lowest level of carbon emissions and greenhouse gases has created an urge to look for renewable energy resources. Among the renewable energy resources available worldwide, solar energy is considered as one of the feasible and mature technologies in view of large-scale commercial deployment. Solar photovoltaic and solar thermal conversion (STC) techniques have been implemented so far and are still advancing towards cost-effective solutions. Parabolic trough collector (PTC) is one such economical and feasible STC technology as far as high-temperature thermal applications are concerned and are being widely used for power generation. This paper is an attempt to present the current scenario of PTC technology along with its various advancements over the years. Further in this paper, selective coatings, coating techniques and heat collection element (HCE) or receiver are discussed in detail with regard to their advancements. The present work also illustrates the progressive trends in PTC technology, particularly with respect to various heat transfer fluids, HCE inserts, selective coatings and other performance factors along with some futuristic aspects with respect to coatings and receiver inserts in view of high thermal performance. Graphic abstract
... Concentration of solar radiation to produce temperature in the range of 100 to 450˚C or more is called concentrated solar thermal (CST) technology [14]. There are six commercially available CST technologies in India [15], namely,  Fixed focus automatically tracked elliptical dish (Scheffler)  Dual axis tracked parabolic dish  Fresnel reflector based dish (Arun dish)  Single axis tracked parabolic trough concentrator  Non-imaging concentrators  Linear Fresnel reflector Abedani et al"s work on variation of aperture size directly influenced the light entry as well as radiated heat losses through the aperture.At an optimum temperature of 212.3 o C, the global maximum exegetic efficiency was foundto be 21.41% with the respect to thermal efficiency of 49.83% [16].A Scheffler collector is a fixed focus solar radiation concentrator which has a capacity to increase the temperature of the receiver up to 200 °C [17]. This paper presents the energy analysis of the receiver of a Scheffler dish solar collector, to calculate the various losses incurred in the process for capturing solar energy by using peripheral temperature distribution around the receiver. ...
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The study of appropriate receiver design is necessary for Scheffler dish solar collector to identify the efficiency of capture of solar energy. In this study experimental analysis work was carried out with an intention to prepare heat balance sheet of Scheffler dish solar collector using novel receiver. The objective behind this study is to prepare a work for future research in direction of increasing the energy collection efficiency of system.The study reveals that with the help of developed novel receiver around 30 minutes of time is sufficient to start receiving net positive energy capture from the system. Also two peak regions are observed where maximum outputof steam was obtained during afternoon. The research work has obtained around 80% of energy collection with the help of novel receiver for Scheffler dish in comparison with the value available in the literature.
... Photovoltaic panels use solar irradiations and produce electricity. Moreover, during this electricity production process, considerable amount of waste heat is also generated which can be taken its benefit by integrating a network of tubes which containing a fluid for heat transfer process [9,10]. Solar collectors can be categorized into two classifications based on the tracking model: no tracking system is installed, fixed collectors, and a tracker system is provided for tracking the sunlight during the daylight, tracking collectors. ...
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Solar energy is a renewable resources of energy which is broadly utilized and have the least pollution impact between the available alternatives of fossil fuels. In this investigation, machine leaening approaches of neural networks (NN), neuro-fuzzy and least squares support vector machine (LSSVM) are used to build the models for prediction of the thermal performance of a photovoltaic-thermal solar collector (PV/T) by estimating its efficiency as an output of the model while inlet temperature, flow rate, heat, solar radiation, and heat of sun are input of the designed model. Experimental measurements was prepared by designing a solar collector system and 100 data extracted. Different analyses are also performed to examine the credibility of the introduced approaches revealing great performance. The suggested LSSVM model represented the best performance regarding the mean squared error (MSE) of 0.003 and correlation coefficient (R2) value of 0.99, respectively.
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Abstract: Community solar cookers (CSCs) hold significant promise for addressing energy poverty and promoting sustainable development. However, existing methods for evaluating CSCs performance are primarily reported in low-temperature applications. This study addresses this gap by proposing a Cooker Opto-Thermal Ratio (COR) based performance evaluation approach for CSCs operating at intermediate temperatures (120-300 °C) for the first time. The big parabolic dish concentrating solar collector (3.801 m2 aperture area) acts as a CSC, which holds a cooking load (test fluid) of ∼ 13 kg in a cooking pot. Results depict that the average COR value for the CSC is 0.163, and the reference cooking time of the CSC varies between 35-46 minutes. Also, the highest achievable fluid temperature shows variation between 167-180 °C. The capital cost of CSC is $ 396, and the LCCM is 0.039 USD/Ml, which is competitive with the levelized cost of LPG-based cooked meals. While the study provides valuable insights, it is limited to a single CSC design. Future research should investigate the applicability of COR across various CSC geometries and configurations. This research establishes a framework for accurate performance assessment and facilitates the development of more effective CSCs for clean and sustainable cooking in decentralized communities.
Chapter
In order for humans to meet their fundamental needs, energy is required. The main sources of natural energy are carbon-based fuels such as biomass and fossil fuels. These fuels made of carbon are scarce and harmful to the environment. Innovative, clean, and environmentally friendly energy solutions are desperately needed. Particularly in light of the global issues posed by population expansion, the environment, and economic growth, solar energy may be a workable alternative for sustainable development. The Scheffler is a unique kind of solar concentrator that can quickly attain a high temperature. By adding a heat storage unit, Scheffler's capacity to retain heat may be greatly boosted. This study compares the thermal and physical properties, such as density, thermal conductivity, and melting point, of various thermal storage materials that are used to store heat energy for a longer amount of time, such as bricks, concrete, water, phase change material (PCM), latent heat storage material (LHS), aluminum, iron, molten salts, silicon, etc.
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Chapter
In order for humans to meet their fundamental needs, energy is required. The main sources of natural energy are carbon-based fuels such as biomass and fossil fuels. These fuels made of carbon are scarce and harmful to the environment. Innovative clean and environmentally friendly energy solutions are desperately needed. Particularly in light of the global issues posed by population expansion, the environment, and economic growth, solar energy may be a workable alternative for sustainable development. The Scheffler is a unique kind of solar concentrator that can quickly attain a high temperature. By adding a heat storage unit, Scheffler's capacity to retain heat may be greatly boosted. This study compares the thermal and physical properties, such as density, thermal conductivity, and melting point, of various thermal storage materials that are used to store heat energy for a longer amount of time, such as bricks, concrete, water, phase change material (PCM), latent heat storage material (LHS), aluminum, iron, molten salts, silicon, etc.
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A Scheffler reflector is a device which converts the Sun's radiation into energy. The receiver is placed at a distance from it to absorb the focused sunlight on it. The way to enhance the performance of a Scheffler reflector is to change the coating material. For a wide range of wavelengths different materials can be used for these coatings, and it is shown that by using different materials the heating output of Scheffler dishes can be enhanced. We have studied the performance analysis of reflectivity of various materials which can be used in Scheffler reflectors like aluminum and glass as well as silver and stainless steel are all great materials with high reflectance. As Scheffler reflector plays a significant part in renewable energy, it can be used in a variety of ways by modifying the material used to cover the reflector dish.
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Fixed focus type Scheffler Concentrators and convex receivers are popularly employed for several medium temperature process heat applications. The excessive convection heat loss from the receiver surface and the improper distribution of solar flux at the receiver are few key issues commonly observed for the Scheffler concentrators. The excessive heat lost is attributed to the convection losses at the receiver convex surface due to the wind. Moreover, experimental studies carried out on the receiver of 16 m2 Scheffler concentrator revealed that about 15–20 % of the total radiations received at the receiver are lost due to the focusing and tracking errors of the Scheffler reflector. In order to minimize the heat losses from the receiver convex surface, a Conical type Secondary Reflector (CSR) made up of highly polished mirror finished stainless steel material, in the form of frustum of a cone, and covered with toughened glass was designed and developed. The semi-cone angle of 36° has been estimated for the CSR based on the ray trace diagram analysis. The CSR, fixed over the periphery of the convex type receiver refocuses the lost solar radiations over the receiver surface and enhances the heat flux received at the receiver, while improving the overall efficiency of the concentrator. The toughened glass cover over the CSR, shields the receiver from the wind and thus reduces the overall convection losses due to wind. Experimental analysis carried with the installation of CSR revealed that the convective heat transfer coefficient has been reduced by 10–12 % on average while the overall system efficiency has been increased by at least 3–5 %. The increased heat flux received at the receiver has not only reduced the convection losses but also reduced the initial idle or lag time for the system by almost 15 min based on the solar insolation for the day.
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Fixed focus type Scheffler concentrators introduced by Wolfgang Scheffler are popularly used for different low to medium industrial process heat applications. These Scheffler concentrators are available in the standard sizes of 8 m 2 and 16 m 2. The present paper provides a detailed stepwise procedure for the design of a standing type 16 m 2 Scheffler concentrator and its fixed focus receiver, intended to be utilized in a solar thermal processing unit for essential oil distillation at our institute. The dome type receivers of boiler steel grade material, SS-304, are selected for the present application. The diameter of the receiver is estimated based on the analysis of the image formed at the receiver of the Scheffler concentrator. The crossbar equations, seasonal parabola calculations and aperture area calculations for the Scheffler concentrator have also been presented in the paper. The geometrical concentration ratio for the Scheffler reflector dish and receiver system are also evaluated for any given day of the year. The design procedure presented in the paper can be used for designing any suitable size Scheffler concentrator and its receiver as per the energy requirement of the application.
Chapter
The Scheffler is a fixed focus elliptical dish system used for harvesting solar energy. It can concentrate the sunlight to a fixed point where receiver is mounted. The focused sunlight is used to heat a suitable fluid contained in the receiver. These types of concentrators are used in a variety of medium and high temperature solar applications. Commonly, cylindrical shape receiver is used with Scheffler collector system. In the current work, four conditions of cylindrical receiver were considered for experimentation to generate steam. Experimental results of 2.7 m² Scheffler for steam generation, show that thermal efficiency of cylindrical receiver is maximum for initial heating of working fluid water in the receiver without tilting condition, Experimentation also carried out for general condition that is working fluid in the receiver is at ambient temperature. An optimum value of thermal efficiency is calculated for combined conditions at different steam pressure for cylindrical receiver. In this case, optimization is done for design value of average solar radiation and mass flow rate of steam at different steam pressure. The comparison between experimental value and predicted value of optimum thermal efficiency shows that cylindrical receiver has satisfactory performance at 1 bar steam pressure. Response surface methodology, (RSM) was used to generate a collection of statistical data and generate equation of thermal efficiency as response with input factors are average solar radiation and mass flow rate of steam. Further, extending the research and enhancing the efficiency with the help of Nature inspired algorithm the results turned out to be the best parameters for maximum efficiency. Slime mold algorithm is used for optimizing the equation of Thermal efficiency and to get the best results and guidelines for further research.
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This paper investigates the turbulent flow of nanofluid (NFs) in which boehmite-alumina nanoparticles with different shapes of platelet, brick, blade, and cylinder suspended in a mixture of W/EG in a flat plate solar collector (FPSC). A hexagonal cross-sectional tube is used in the FPSC and compared with a simple one. The problem variables include flow rate (FR) (0.25–1 kg / s), shape and volume percentage (φ) of nanoparticles (NPs) (0–4%), tube shape (circular and hexagonal) and FPSC material (copper and steel). The influence of these variables on the FPSC output temperature (TCOUT), Nusselt number (Nu) and heat transfer coefficient (h) is investigated. The results reveal that copper FPSC can provide higher TCOUT but has lower convective coeffient and Nu than steel FPSC. The outlet fluid temperature is 1.86 °C higher when pure fluid flows in copper tubes. The addition of NPs, particularly bricks, causes the temperature of the fluid at the outlet to rise. This increase is about 1°for φ = 4%. The use of a hexagonal tube enhances the temperature of the fluid at the outlet relative to a circular one. For copper and steel FPSCs, this increase is 2.67 and 1.75 °C for pure fluid, respectively. The addition of NPs reduces the amount of heat transfer and Nu for the FPSCs.
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This paper proposes a Tension Cable-Membrane Concentrator with an ultra-lightweight, practical and low cost alternative construction which is used in the optical-electrical conversion system. The relationship between the varied count triangular facets of the membrane surface and the focal spot radius are studied. Based on Monte Carol ray-tracing method, the optical performances of the concentrator, such as the concentrate ratio, flux distributions and focal spot radiuses etc., are analyzed in different geometry design parameters. Further, a 15 m aperture Tension Cable-Membrane Concentrator is designed, and the form-finding design is studied and verified by ANSYS®. The optical performance comparisons with the original and pre-stressed shape of the reflective film are discussed. Simulation results exhibit that the surface density of the proposed Tension Cable-Membrane Concentrator is only 5% of that of traditional rigid concentrator. It takes on the ultra-lightweight and low-cost that excite designers. The optical performance comparisons show that the peak flux distribution after form-finding over a 0.25 m receiver approximately deliver up to 800 kW/m² corresponding to the peak concentrate ratio exceeds 1000 suns which are even better than the traditional steel design and completely satisfy design requirements.
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Background Today, one of the concerns is to reduce the efficiency of photovoltaic solar cells as their temperature rises. Therefore, cooling photovoltaic is one of the challenges that will be addressed in this article. In this paper, the cooling of a photovoltaic cell by a newly designed heatsink is numerically investigated. Method Two nanofluids were used to cool the heatsink. The heatsink consists of an Aluminum cover and two main parts in which there are numerous channels with zigzag walls. Moreover, the two-phase mixture method was employed to simulate the nanofluids flow based on finite volume method. The performance of the heatsink and photovoltaic were studied for concentration of the nanoparticles at different Reynolds numbers. Findings Using nanofluids increases the heat transfer coefficient but also increases the required pumping power. By adding 2% alumina at the Reynolds number of 150, the heat transfer coefficient increases by 83%. Furthermore, Al2O3/H2O nanofluids has better thermal resistance and temperature uniformity than CuO/H2O nanofluids for heatsink and photovoltaic. The addition of alumina nanoparticles increases the thermal efficiency of photovoltaic while the addition of copper oxide nanoparticles reduces it. Moreover, by increasing the Reynolds number from 50 to 150, the thermal efficiency increased by 7%.
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A review on various aspects of institutional solar cooking is presented. Starting with an overview of energy requirement for cooking, the review includes cooking technologies developed for institutional solar cooking, polices and programs for their promotion and case studies reported in the literature on field level application. State of the art concentrating solar technologies suitable for institutional level cooking includes Parabolic dish, Scheffler dish and ARUN® dish. Design, construction and operational details of both direct and indirect types of concentrating solar cookers have been discussed. The case studies, mainly from India, included provide useful feedback on the experiences of using large scale institutional solar cooking systems. A Few installations of each type of solar cooker have been reviewed and major findings and observations on various aspects of the same are reported.
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The thermal performance of cubical receiver with trapezoidal ice-pot has been investigated with the aim to generate hot water by melting of ice at high altitude regions (Leh Ladakh). In the experimental setup, one hollow mild steel cubical receiver (filled with heat transfer fluid) with ice-pot and four different types of solid cubical receivers with ice-pot are used to melt the ice with direct heating in minimum time. The radiations are focused on receiver with the help of 1m² Scheffler concentrator that is exposed to the atmospheric situations of NIT Kurukshetra. The results from the designed setup are obtained where it is found that the frozen ice at -4∘C melts completely, converting into water and the maximum temperature of the water attained in hollow cubical receiver, solid receiver (granite), solid receiver (dholpur stone), solid receiver (concrete) and solid receiver (mild steel) is 42.5∘C, 32.9∘C, 49.5∘C, 30.2∘C and 52.7∘C respectively.
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This review presents innovative extraction techniques and their role in promoting sustainable ingredients for the food, cosmetic and pharmaceutical industries. These techniques (such as microwave, ultrasound, pulse electric field, instant controlled pressure drop, sub- and super-critical fluid processing, extrusion, mechanochemistry, high pressure, and ohmic, UV and IR heating) use or produce less solvent, energy, and hazards. This review will provide the necessary theoretical background and some details about green extraction techniques, their mechanisms, some applications, and environmental impacts. We will pay special attention to the strategies and present them as success stories for research and education and at the industrial scale.
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This experimental analysis was performed with the aim to melt the ice into hot water at very high altitude regions such as Leh Ladakh. Three different designs of ice‐chamber were used to melt the ice with direct heating in minimum time. The radiations were focused on the receiver with the help of 1 m2 Scheffler solar concentrator exposed to the atmospheric situations of NIT Kurukshetra. The Scheffler solar concentrator was fabricated with fiber‐reinforced plastic material. The fabrication process is discussed in detail. The results obtained from the design showed that the ice frozen at −5°C completely melted, converting into water. The maximum temperature of water attained in the ice‐chamber with receiver 1 (circular plate with fins), 2 (CPC with fins), and 3 (copper crucible) was 57.7°C, 64.3°C, and 67.4°C, respectively.
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Most of the solar collectors experiments are carried out under clear-sky conditions to evaluate the maximum performance of collectors, even though this condition is not critical for some uses, such as cooking. The optical and thermal performance of a solar oven heated by Scheffler concentrator is here analyzed in more adverse weather conditions. The receiver for conversion and heat transfer of the concentrated solar energy is coupled to an oven specially developed for this work. The Scheffler concentrator geometry is a lateral cut angled 43.23° of a paraboloid matrix, and it works in a two-axis tracking system, to always maintain its focal image at the stationary receiver with the progression of the Earth rotation and solar declination movements. A model for distributing the daily radiation over the hours is used to compare the results. The time-constant experimental method is considered. The heating and cooling tests were carried out at the official local time. The maximum temperature achieved by the absorber was 328°C, and the maximum average temperature in the oven was 150°C. The results for heat loss factor were evaluated, and the trends for thermal efficiency and optical efficiency factor were analyzed for the system considered
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The technology of small point-focusing concentrator of solar energy has been developing rapidly in recent years owing to its compact structure and high collecting efficiency. This report presents important developments of small point-focusing concentrator in the past decade. This kind of solar concentrator refers to the parabolic dish concentrator, the point-focusing Fresnel lens, and the Scheffler reflector. Technological advances of these concentrators and the related performances have been presented. There are three main mirror fabrication technologies for dish concentrator, which are high polishing metal, silver-glass mirror and vacuum-membrane. Polymethyl methacrylate is widely used as material in Fresnel lens. Many scholars have proposed new lens shape to improve the uniformity of focusing. The Scheffler reflector has a characteristic of fixed focus, but its design parameters are not perfect so current research focuses on the theoretical calculation of the mirror. In addition, typical applications of the small point-focusing concentrator in photovoltaic system, solar thermal system, solar chemical system, and day-lighting system are summarized. Upon listing the important publications in open literature, a category of main applications of such kind of solar collector is provided based on the working characteristics of the system.
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The performance of Scheffler reflector has been studied. In this system, a single drum of 20 liter capacity was installed at focal point to serve the dual purpose as absorber tube and storage tank. The performance analysis tests have revealed that the average power and efficiency in terms of water boiling to be 1.30 kilowatts and 21.61 % respectively against an average value of beam radiations of 742[Wm-2]. The maximum water temperature in the storage tank to 98 °C was achieved on a clear day operation and ambient temperature between 28 °C to 31 °C. Using this experiment a generalized data based model is formulated.
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Distillation of medicinal and aromatic plants for essential oils extraction can be done by utilizing heat in medium temperature range.These essential oils are used in foods, medicines and cosmetics etc. and are money earning business for the farming community. This research is focused to develop an on-farm solar distillery for the processing of different plant materials. The system comprises of a Scheffler reflector and a complete set of distillation system. An 8 m2 ‘projected area of the Scheffler solar concentrator was coupled with the distillation still for the extraction of essential oils. In this paper, a complete mathematical description has been explained to design different components of solar distillation system. In order to provide a fixed focus on a receiver from morning to evening and in summer and winter, flexible crossbars have been used to achieve the desired shapes of the reflector. The paper also covers all the details regarding design, development, site specific installation and tracking system etc. Different types of Florentine apparatuses were used to separate the essential oils from the hydrosol. Necessary instrumentation was used for the performance evaluation of solar distillery. The system was capable of producing 300–450 �C temperature at the receiver section within the beam radiation range of 800–850 W m�2. The efficiency of solar distillery was calculated to be 33.21% with 1.548 kW thermal power available for processing in the distillation still. The system was operated for 10–12 h a day during summer. About 18.58 kW h thermal energy was obtained from the solar distillery in a sunny day. For the processing of 10 kg batch, an average 3.5 kW h energy was consumed. In this way, about 4–5 batches were processed successfully using different kinds of plant materials with 10–20 kg per batch. The research concluded that different kind of medicinal and aromatic plants could be processed effectively using solar distillery.
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The performance of Scheffler reflector has been studied. In this system storage reservoir was installed at Focus point. It has a single large diameter drum which serves the dual purpose of absorber tube and storage tank. The drum is sized to have a storage capacity of 20 liter for experiment. The tests were carried out with this set-up and were repeated for several days. Performance analysis of the collector has revealed that the average power and efficiency in terms of water boiling test to be 1.30 kW and 21.61%, respectively, against an average value of beam radiations of 742 W/m(2). The maximum water temperature in the storage tank of 98 degrees C has been achieved on a clear day operation and ambient temperature between 28 degrees C to 31 degrees C.
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The performance of 2.7 m 2 Scheffler reflector has been studied. Scheffler Reflector is parabolic dish collector designed to collect energy from sunlight. In this System storage vessel was installed at focus point . Vessel stores 10 ltr of water for the purpose of experimentation. Tests were carried out with this set up for the purpose experimentation. Performance analysis of the reflector revealed that average power and efficiency in terms of water boiling tests to be 550 W and 19%. Maximum temperature of water was observed to be 94 0 C. Ambient temperature was observed to be in between 32 o C and 40 0 C.
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The characteristics, performance and general operation strategy of parabolic-trough direct steam generation (DSG) loop in recirculation mode have been numerically studied. The controllable separation steam quality , which characterizes the two-phase flow, and the corrected direct normal irradiance ( W m−2), the major weather impact, were chosen as two independent parameters. The results show that for a given , the onset of evaporation is advanced with increasing . The convective heat loss is less or equal to the radiative part at the inlet, then surpasses and finally could reach up to 1.6 times of the radiative part at outlet. The energy efficiency decreases along the loop regardless of or while the exergy efficiency varies diversely according to in the superheating stage. This diverse variation is due to the opposite trends of energy level and heat gain. When W m−2, the stratified flow shows an apparently increasing probability to emerge over the loop with decreasing , where the thermal-stress risk may exist. To quantify the probability, a novel flow pattern indicator is proposed. In addition, a general -based operation strategy of DSG loop concerning both performance and safety is given, of which the merit is verified through a case study in typical summer and winter days in North China.
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Triple‐junction solar cells from III–V compound semiconductors have thus far delivered the highest solar‐electric conversion efficiencies. Increasing the number of junctions generally offers the potential to reach even higher efficiencies, but material quality and the choice of bandgap energies turn out to be even more importance than the number of junctions. Several four‐junction solar cell architectures with optimum bandgap combination are found for lattice‐mismatched III–V semiconductors as high bandgap materials predominantly possess smaller lattice constant than low bandgap materials. Direct wafer bonding offers a new opportunity to combine such mismatched materials through a permanent, electrically conductive and optically transparent interface. In this work, a GaAs‐based top tandem solar cell structure was bonded to an InP‐based bottom tandem cell with a difference in lattice constant of 3.7%. The result is a GaInP/GaAs//GaInAsP/GaInAs four‐junction solar cell with a new record efficiency of 44.7% at 297‐times concentration of the AM1.5d (ASTM G173‐03) spectrum. This work demonstrates a successful pathway for reaching highest conversion efficiencies with III–V multi‐junction solar cells having four and in the future even more junctions. Copyright © 2014 John Wiley & Sons, Ltd. In this work, a GaAs‐based top tandem solar cell structure was bonded to an InP‐based bottom tandem cell with a difference in lattice constant of 3.7%. The result is a GaInP/GaAs//GaInAsP/GaInAs four‐junction solar cell with a new record efficiency of 44.7% at 297‐times concentration of the AM1.5d (ASTM G173‐03) spectrum. This work demonstrates a successful pathway for reaching highest conversion efficiencies with III‐V multi‐junction solar cells having four and in the future even more junctions.
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The global demand for energy is growing and conventional energy sources like coal and petroleum are depleting, and renewable resources will play a crucial role in the future. The development of clean and sustainable energy technology is imperative to avert the impending climatic crisis. A worthy investment option is concentrating solar power (CSP) technology which has the capacity to provide for about 7% of the total electricity needs projected for the world by 2030 and 25% by 2050 (considering a high-energy-saving, high-energy-efficiency scenario) [1]. In the present study, the various concentrators available have been explored. Countries all over the world have recognized the potential for CSP and numerous plants are being planned and constructed with incentives offered by the governments. In India, the states of Rajasthan and Gujarat have the potential for widespread application of CSP technology to harness the solar resource. The launch of The Jawaharlal Nehru National Solar Mission (JNNSM) in 2008 by the Indian Government and its initiatives, complemented by state solar policy passed by the states of Rajasthan and Gujarat, will go a long way in the establishment of CSP to supply a segment of India's upcoming energy needs.
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Consisting of two parts, this article explores the history and challenges facing the Gobitec project in China, Japan, Mongolia and South Korea, an ambitious proposal to build a multibillion dollar solar power system in the Gobi desert that then exports electricity throughout Northeast Asia. After detailing its primary methods of data collection—research interviews, site visits, and a literature review—this first part of the study details the history of the Gobitec concept and its close relation to the Desertec concept in North Africa and Europe. It then discusses the “promise” of very large solar systems in deserts, namely improved security of supply and reduced greenhouse gas emissions. However, the second part of our study finds that such projects also face a list of serious – and perhaps insurmountable – technical, economic, political, and social barriers. That second part concludes by drawing implications for large-scale energy projects and energy policymaking more broadly.
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This communication presents a second law analysis based on an exergy concept for a solar thermal power system. Basic energy and exergy analysis for the system components (viz. parabolic trough collector/receiver and Rankine heat engine, etc.) are carried out for evaluating the respective losses as well as exergetic efficiency for typical solar thermal power systems under given operating conditions. It is found that the main energy loss takes place at the condenser of the heat engine part, whereas the exergy analysis shows that the collector–receiver assembly is the part where the losses are maximum. The analysis and results can be used for evaluating the component irreversibilities which can also explain the deviation between the actual efficiency and ideal efficiency of a solar thermal power system.
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Scheffler fixed focus concentrators are successfully used for medium temperature applications in different parts of the world. These concentrators are taken as lateral sections of paraboloids and provide fixed focus away from the path of incident beam radiations throughout the year. The paper presents a complete description about the design principle and construction details of an 8m2 surface area Scheffler concentrator. The first part of the paper presents the mathematical calculations to design the reflector parabola curve and reflector elliptical frame with respect to equinox (solar declination=0) by selecting a specific lateral part of a paraboloid. Crossbar equations and their ellipses, arc lengths and their radii are also calculated to form the required lateral section of the paraboloid. Thereafter, the seasonal parabola equations are calculated for two extreme positions of summer and winter in the northern hemisphere (standing reflectors). The slopes of the parabola equations for equinox (solar declination=0), summer (solar declination=+23.5) and winter (solar declination=−23.5) for the Scheffler reflector (8m2 surface area) are calculated to be 0.17, 0.28, and 0.13 respectively. The y-intercepts of the parabola equations for equinox, summer and winter are calculated as 0, 0.54, and −0.53 respectively. By comparing with the equinox parabola curve, the summer parabola is found to be smaller in size and uses the top part of the parabola curve while the winter parabola is bigger in size and uses the lower part of the parabola curve to give the fixed focus. For this purpose, the reflector assembly is composed of flexible crossbars and a frame to induce the required change of the parabola curves with the changing solar declination. The paper also presents the calculation procedure of seasonal parabola equations for standing reflectors in the southern hemisphere as well as for laying reflectors in the northern and southern hemispheres. Highly reflective aluminium sheets are used on the crossbar profiles to complete the concentrator. The reflector is installed at the required site by setting its axis of rotation at an angle equal to the latitude of the site. For daily tracking, these concentrators rotate along an axis parallel to the polar axis of the earth at an angular velocity of one revolution per day with the help of simpler and cheaper self-tracking devices. For seasonal tracking, the reflector rotates at half the solar declination angle with the help of a telescopic clamp mechanism. The design procedure is simple, flexible and does not need any special computational setup, thus offering the prospect of potential application in domestic as well as industrial configurations.
Article
Essential oils have been used throughout the world in foods, fragrances, perfumery, cosmetics, and medicines and these oils are very expensive. The study was initiated to develop an on-farm solar distillation system for functional, environmental and economic reasons. A Scheffler fixed focus concentrator is used for the solar distillation system. The system comprises a primary reflector (8 m2 area), secondary reflector, distillation still, condenser and Florentine flasks. The primary reflector rotates along an axis parallel to the earth’s axis of rotation with the help of a precise photovoltaic tracking device and keeps the reflected beam aligned with the fixed secondary reflector as the sun moves. The secondary reflector further reflects the beam to target the bottom of the distillation still. The paper presents the development, evaluation and experimental results of the solar distillation system. The temperature at the focus was recorded as between 300 and 400 °C for beam radiation in the range 700–800 W m−2. The average power and efficiency of the solar distillation system were found to be 1.548 kW and 33.21% respectively. Different medicinal and aromatic plants like Melissa, Peppermint, Rosemary, Cumin, and Cloves etc were processed successfully by using the solar distillation system and their process curves were drawn.
Article
Thermal energy storage has recently attracted increasing interest related to thermal applications such as space and water heating, waste heat utilization, cooling and air-conditioning. Energy storage is essential whenever there is a mismatch between the supply and consumption of energy. Use of phase change material (PCM) capsules assembled as a packed bed is one of the important methods that has been proposed to achieve the objective of high storage density with higher efficiency. A proper designing of the thermal energy storage systems using PCMs requires quantitative information about heat transfer and phase change processes in PCM. This paper reviews the development of available latent heat thermal energy storage technologies. The different aspects of storage such as material, encapsulation, heat transfer, applications and new PCM technology innovation have been carried out.
Article
The exergetic performance of concentrating type solar collector is evaluated and the parametric study is made using hourly solar radiation. The exergy output is optimized with respect to the inlet fluid temperature and the corresponding efficiencies are computed. Although most of the performance parameters, such as, the exergy output, exergetic and thermal efficiencies, stagnations temperature, inlet temperature, ambient temperature etc. increase as the solar intensity increases but the exergy output, exergetic and thermal efficiencies are found to be the increasing function of the mass flow rate for a given value of the solar intensity. The performance parameters, mentioned above, are found to be the increasing functions of the concentration ratio but the optimal inlet temperature and exergetic efficiency at high solar intensity are found to be the decreasing functions of the concentration ration. On the other hand, for low value of the solar intensity, the exergetic efficiency first increases and then decreases as the concentration ratio is increased. This is because of the reason that the radiation losses increase as the collection temperature and hence, the concentration ratio increases. Hence, for lower value of solar intensity, there is an optimal value of concentration ratio for a given mass flow rate at which the exergetic efficiency is optimal. Again it is also observed that the mass flow rate is a critical parameter for a concentrating type solar collector and should be chosen carefully.
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