Solar Dish Concentrator Research Articles

Cavity receivers in solar dish collectors: A geometric overview

Many studies, as numerical and experimental, regarding the applications of solar dish concentrators have been performed. Most researchers focused on the maximum thermal efficiency, the minimum heat loss, and their relations to the solar receiver geometries. This paper presents and discusses the previous studies investigating different cavity receiver geometries and their optimization methods with parabolic dish collectors. More specifically, cylindrical, hemispherical, conical, and flat sides cavity receivers are investigated in this manuscript. For an inlet operating temperature of 200 °C, the conical cavity shape has shown a thermal efficiency of around 70%, exergy efficiency of 30%, and optical efficiency of around 87%. The working fluid temperature is often around 650 °C–750 °C in the solar dish collectors. Due to high working temperature and cavity shape, heat losses such as radiation, conduction, and convection losses are highlighted that could provide adverse effects upon the system thermal efficiency. Besides, the diameter aspect ratio, the cavity inclination angle, type of tube, and the tube shape can be impressive on the cavity heat losses value. Therefore, the optimized geometry of the cavity receiver is a vital subject. Based on the analyzed issues, some suggestions and concluding remarks are presented.

Helically coiled solar cavity receiver for micro-scale direct steam generation

Concentrated solar systems have a large potential for power generation and water pumping in rural off-grid settlements with a high solar irradiance resource. With the use of a solar dish concentrator, superheated steam can be directly generated in a solar cavity receiver. Volumetric expanders show promise for micro-scale power production (below 1 kW). However, naturalistic experimental investigations of micro-scale direct steam generation using a solar dish is limited. In this work, a low-cost helically coiled cavity receiver and a novel solar concentrator manufactured from off-the-shelf components are experimentally investigated for steam generation at water pressures of above 3 bar. Working fluid temperatures were measured throughout the coil length and pressures were measured at the inlet and outlet of the receiver coil. Using a concentrator with a total incident area of 2.70 m2 and a water flow rate of 0.294 g/s, the working fluid captured 861 W of heat with an outlet temperature of 343 °C at an average solar irradiance of 757 W/m2. The average thermal efficiencies of the collector and receiver were determined to be 42% and 50%, respectively, for the testing period. Furthermore, the average second-law efficiency was 12%. Flow patterns within the coil were investigated by considering the temperature differences between the coil surface and the working fluid. A heat loss model was developed that could predict the steady-state heat loss rate with an accuracy of 97%. The observations made during the study and the results obtained highlight important design aspects that need to be considered in future work.

Experimental investigation on thermal performance of cavity receiver integrated with short-term thermal energy storage for a solar parabolic dish concentrator

Solar parabolic dish collectors are widely used for solar thermal energy conversion for various medium- and high-temperature applications. One of the problems being faced by the receivers of parabolic dish collectors is the short-time non-availability of solar radiation because of cloud cover. This affects the useful output and also results in a sudden change in the receiver temperature, which induces thermal stress in it. Hence receiver with short-term thermal energy storage is attempted to tackle this issue. A hemispherical cavity receiver is developed with a double-layered wall, and the space between the two layers is filled with a salt bath composed of a eutectic mixture of NaNO3 and KNO3 as phase change material. The heat transfer fluid flows through the copper tubes that are coiled in the gap between the two layers. The phase change material surrounds the copper tubes and acts as a storage as well as a heat transfer medium. Experimental results show that the integration of the storage medium to the receiver has a good impact on the thermal output, even during irregular radiation input conditions. The receiver has attained a net energy efficiency of 31.4% for an average irradiance of 561 Wm−2.

Design and development of a low‐cost solar parabolic dish concentrator system with manual dual‐axis tracking

SummarySolar parabolic dish attracts most of the researchers with its higher concentration ratio and its modular ability. Parabolic dish concentration can be employed in many applications which falls under solar thermal and solar electricity production. This article presents a novel approach of designing and development of a low‐cost solar parabolic dish concentrator of 12.6 m2 aperture area with dual‐axis manual tracking, which can be utilized for process heating and electrical power generation simultaneously. The same set up has been fabricated in National Institute of Technology, Puducherry and ready for investigation and analysis on different prospective. The design concept of solar parabolic dish concentrator and dual‐axis tracking system and its economic analysis are elaborately discussed in this article. The complete procedure followed for the fabrication of the entire system is also highlighted. Based on the economic analysis it was found to be more economical than the other existing dish concentrators in the literature, which costs ₹6877.00 per square meter.

THERMAL PERFORMANCE ANALYSIS OF GLAZED AND UNGLAZED RECEIVER OF SCHEFFLER DISH

The impact of reradiation and convection losses from the receiver is substantial on the performance of solar parabolic dish concentrator. In this paper, an experimental and theoretical study to compare the performance of the glazed and unglazed receiver of Scheffler dish for direct steam generation is presented. Tempered glass cover is provided on aperture to reduce the reradiation and convection losses from the receiver. Improvement in the efficiency of the Scheffler dish is found due to suppressed heat losses from the receiver front surface. Overall heat loss coefficient, useful energy transfer rate to water, steam flow rate, and efficiency of the system with and without glass cover on the receiver are evaluated and compared. The average solar beam intensity during experimentation was 569 W/m2 and 600 W/m2 with the glazed and unglazed receiver respectively. The average temperature at the receiver with glazing is recorded as 425oC, even at low solar beam intensity in comparison with the unglazed receiver. Overall heat loss coefficient at the front surface of the receiver is reduced to 6.04 W/m2K. It has been observed that the Scheffler dish with a glazed receiver achieves thermal performance above 50.00% within the solar beam intensity range of 600-650 W/m2. The enhancement of 8.74% in the average thermal efficiency, with glass cover on the receiver is achieved.

Solar gasification of grape marc for syngas production: Solar-dish-coupled reactor basic engineering and optimization

In this paper, a new 5.8 kW solar biomass gasification reactor design is proposed. It is meant for energetic exploitation of grape marc, a residue of the wine-making industry. The design couples the reactor with a 3.0 m diameter Parabolic Dish Solar Concentrator, and contemplates controlling its temperature by manipulating the biomass inlet rate. This work aims to establish an upper limit on the reactor syngas yield under actual solar and environmental conditions, to determine the optimal dimensions of the reactor, and to evaluate the feasibility of the temperature control system. Also, a process is proposed for industrial application and practical implications are considered. The performance of the reactor was numerically simulated employing 1-min solar irradiance data, heat transfer models, reaction models and enthalpy balances. The reactor dimensions that maximize syngas production were determined. Simulation results showed an upper limit of 73 gdry basis/min for the grape marc inlet rate (stationary regime), and of 3180 Nm3 (36.68 GJ) for the total syngas yield on the grape marc production season. Solar irradiance peaks were compensated, which supports the proposed temperature control system. Several design aspects were found to have substantial impact on the reactor performance, which contributes towards prototype manufacturing.

Rotordynamics analysis of solar hybrid microturbine for concentrated solar power

Microturbine based on a parabolic dish solar concentrator runs at high speed and has large amplitudes of subsynchronous turbo-shaft motion due to the direct normal irradiance (DNI) fluctuation in daily operation. A detailed rotordynamics model coupled to a full fluid film radial or journal bearing model needs to be addressed for increasing performance and to ensure safe operating conditions. The present paper delivers predictions of rotor tip displacement in the microturbine rotor assembly supported by a journal bearing under non-linear vibrations. The rotor assembly operates at 72 krpm on the design speed and delivers a 40 kW power output with the turbine inlet temperature is about 950 °C. The turbo-shaft oil temperature range is between 50 °C to 90 °C. The vibrations on the tip radial compressor and turbine were presented and evaluated in the commercial software GT-Suite environment. The microturbine rotors assembly model shows good results in predicting maximum tip displacement at the rotors with respect to the frequency and time domain.

Thermal Performance Analysis of Solar Dryer Integrated with Heat Energy Storage System and a Low-Cost Parabolic Solar Dish Concentrator for Food Preservation

Solar energy has become a viable alternative energy because it is a clean type of energy that converts solar radiation into heat energy for various applications such as heating water, power generation, cooking, and food drying. The solar dryer, integrated with the heat energy storage system, uses nitrate salt as a heat storage medium which was designed and tested by drying 1000 grams of red pepper at 19.6 to 62.4°C. The average ambient temperature ranged from 19.3 to 37.4°C, and the maximum temperature of the heat storage media ranged from 87.8 to 125°C. The solar drying process was compared to open sun drying system loaded with 1000 grams of red pepper. The findings showed that the solar dryer maintained color and flavor and lowered the original moisture content from 86% to 10% for 24 hours compared to 36 hours of drying in open air. In this study, nitrate salt is shown to be the perfect heat storage medium for drying food products; it preserved heat for about 4 hours when there is no active sunlight.

Exergy recovery from water heating by a Scheffler collector for more exergetic factor

AbstractIn this experimental research, the recovery of exergy from a Scheffler collector is assessed where a receiver cum spiral absorber tube of mild steel of size, 0.025 m diameter and 10 m length was tested at various Direct Beam Radiations (DNI) (500, 600, 700, 800, and 900 W/m2) and mass flow rates of water (400, 600, 800, 1,000 and 1,200 kg/hr). For this aim, the heating of the flowing water is performed through the receiver, installed at the fixed focus of the collector. As a significant consequence, by rising the DNI and mass flow rate, the recovered exergy enhanced. Further, the increment of the exergy factor because of the utilization of the recovered exergy from the Scheffler collector has also been investigated in this paper. The results demonstrate that by utilizing the recovered exergy, the exergy factor increased approximately 36.18%. The outcomes of this research article are also validated with the “solar parabolic dish concentrator” to set the novelty of the work.

The Effect of Different Absorber Configurations On The Exergy and The Energy of Parabolic Solar Dish

Abstract— The solar energy is the most important type of energy. The parabolic dish solar collector (PDSC) is the best type among other solar collectors because it is always tracking the sun movement. The exergy and the energy performances of a PDS were analyzed experimentally and numerically. The effect of different coil geometries and different mass flow rates of heat transfer fluid (HTF) were investigated. The PDS has parabolic dish and receiver with diameter (1.5) m and (0.2) m respectively. Concentration ratio is 56.25. The parabolic polar dish was supported by a tracking system with two axes. The types of the copper absorber were used which are: (spiral –helical) coil (SHC) and spiral-conical coil (SCC). The results showed that the useful energy and thermal efficiency are varying with solar radiation variation. The useful energy varying between (480-765) W for (SHC), the thermal efficiency varying between (35.2-39.8) % for (SHC). Exergy efficiency varying between (6.9 –8.6) %. It was shown that the higher values of useful energy for (spiral – helical) absorber was 0.1L/min flow rate.
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Improvement in the Flux Uniformity of the Solar Dish Concentrator System through a Concave Quartz Window

A nonuniform and high-strength heat flux load would reduce the working efficiency, safety, and in-service life of a cavity receiver. Four types of concave quartz windows, including conical, spherical, sinusoidal, and hyperbolic tangent, were proposed to be used in the cylindrical cavity receiver of a solar dish concentrator system, which can improve the flux uniformity and reduce the peak concentration ratio of the receiver. For each concave quartz window, 36 structural schemes were offered. Based on the Monte Carlo ray-tracing method, the results showed that the nonuniformity coefficient of the receiver was 0.68 and the peak concentration ratio was 1320.21 by using a plane quartz window. At the same time, when the receiver is in the best optical performance, it is the receiver with sinusoidal, conical, spherical, and hyperbolic tangent quartz windows, respectively. The optical efficiency of the receiver with the above four types of quartz windows was basically the same as that of the receiver with the plane quartz window, but their nonuniformity coefficients were reduced to 0.31, 0.35, 0.36, and 0.39, respectively, and the peak concentration ratio was reduced to 806.82, 841.31, 853.23, and 875.89, respectively. Obviously, the concave quartz window was better than the plane quartz window in improving the flux uniformity. Finally, a further study on the sinusoidal quartz window scheme of all of the above optimal parameter schemes showed that when the installation position of the receiver relative to the dish concentrator was changed, the flux uniformity of the receiver could continue to improve. When the surface absorptivity of the receiver was reduced, the optical efficiency would be reduced. For the parabolic dish concentrator with different focal distance, the concave quartz window can also improve the uniformity of the flux distribution of the cylindrical cavity receiver.

A Method for the Installation Measurement and Alignment of a Mirror Unit in the Solar Dish Concentrator

The mirror unit installation error of the solar parabolic dish concentrator can adversely affect its optical performance causing optical intercept losses and hot spots on the absorber surface, which in turn affect safety. Thus, minimizing mirror installation error is considered very important. In this paper, a new method for the facet installation measurement and facet alignment of the mirror unit in the dish concentrator is presented. Firstly, a “clean” facet installation error measurement method using photogrammetry is presented. The photogrammetry measures the spatial coordinates of three feature points to reverse the mirror facet alignment error parameters. Next, two novel methods, a three-rotation alignment method and two-rotation alignment method for aligning the mirror facet are presented and corresponding mathematical models. The advantage of these alignment methods is that the adjustment value and order for each support bolt can be determined before the mirror facet is aligned, which could provide quantitative adjustment information to operator and avoid repeated adjustments. Finally, validity of the installation measurement and facet alignment method was verified by a numerical simulation and an experiment using a metal facet alignment. The presented methods do not rely on the geometry of the reflector mirror and could therefore have extensive uses in applications such solar tower and trough concentrator.

Experimental Analysis of Solar Dish Concentrators With Cylindrical, Oval, and Conical Cavity Receivers

Abstract Three experimental models including cylindrical, oval, and conical cavity receivers were analyzed and tested to estimate the optimum geometry for parabolic dish collector cavity receivers . The main contribution of this paper is that new experimental models are suggested and examined to strengthen the capability of absorbers of solar thermal dish collectors to absorb solar energy. The models were examined for three values of mass flow rates and five values of inlet temperatures of the heat transfer fluid. The thermal performance was evaluated by estimating the thermal efficiency , exergetic performance , and pressure difference. The results recorded the highest values of and for the conical cavity receivers, equal to , and the lowest values of the pressure drop.

可改善平面接收器能流均匀性的太阳能碟式聚光器设计

可改善平面接收器能流均匀性的太阳能碟式聚光器设计

Implementación de Motor Stirling para generación de energía eléctrica limpia empleando una lente de Fresnel

In search of expanding the generation of electric power and reduce the burning of fossil fuels. It is proposed to use the tools that already have and the necessary information to make a prototype of Alfa type Stirling engine, which is a thermal machine with low levels of noise and toxic emissions, that its relative design is of low manufacturing cost for the generation of clean electrical energy, for the heating we will use a Fresnel lens with the purpose of satisfying the thermal energy demand of the same, in the sense of achieving the best angle of capture of solar rays, at the same time achieving the highest concentration of heat possible for the heating angle of the motor. The validation of the proposed model is based on experimental results, using the information obtained from the production of electrical energy, with this the validation of the prototype will be performed, similar to the solar parabolic dish concentrator.

An experimental study on energy and exergy performance of a spiral tube receiver for solar parabolic dish concentrator

In this paper, energy and exergy performance of an external type spiral tube receiver for a solar parabolic dish concentrator is experimentally analyzed and presented. Performance evaluation is done at three different radiation conditions. The receiver is tested in the temperature range of 30 °C–100 °C with water as heat transfer fluid and at a flow rate of 1.5 L per minute. The overall heat loss coefficient of the receiver estimated from the stagnation test is found to be 182 W/m2K. The average thermal and exergy efficiencies of the receiver was determined to be 56.21% and 5.45% respectively under an average beam radiation of 750 W/m2. The variation trend of thermal efficiency of receiver is similar to that of difference between temperature of the heat transfer fluid at receiver inlet and outlet. The results show that this light weight, low cost receiver has potential to be employed with solar parabolic dish concentrator for process heating applications.

A review of Thermal Performance of Solar Concentrator – the future needs

Abundant solar energy is freely available almost round the year in India. As per the current scenario of global warming and climatic change, solar energy is the cleanest source in nature. Concentrated solar power (CSP)has hardly contributed to the overall installed solar power capacity in the country. CSP technologies are Parabolic Trough Collector (PTC), Linear Fresnel Reflector (LFR), Paraboloid Dish and Solar Power Tower. This paper presents a review of CSP in solar parabolic dish concentrator to understand thermal aspect like thermal efficiency, optical efficiency, useful heat gain, heat losses, solar irradiation, etc. for various applications and current development. The current scenario of global CSP is discussed to meet the future challenges and need of the society.

Numerical study of natural convection in flat receiver with and without secondary reflector for solar parabolic dish system

The sustainability of our eco system is under threat due to frequent use of the fossil fuels. Due to the rapid depletion of the conventional energy sources and oil crisis, there is a great shift towards renewable energy sources. In the realm of renewable sources of energy, solar energy plays an impeccable role because of its abundance and dominance over the other sources. Therefore, efforts are being made to replace our existing conventional fuels with renewable energy sources. In this context, flow simulation and heat transfer are performed for the flat receiver with and without secondary reflector of solar parabolic dish collector is presented. A two-dimensional (2-D) model is used to investigate the approximate estimation of the natural convection heat loss from the actual geometry of the receiver for solar dish concentrator system. The Nusselt number correlations are proposed separately and compared for both receiver with secondary reflector (WSR) and without secondary reflector (WOSR) using power law and asymptotic computational fluid dynamics technique.

Thermal analysis of a hybrid solar desalination system using various shapes of cavity receiver: Cubical, cylindrical, and hemispherical

In this research paper, a hybrid solar desalination system has been employed. The hybrid solar desalination system includes photovoltaic thermal panels, solar dish concentrator, and humidification-dehumidification desalination unit. The humidification-dehumidification desalination unit comprises a closed-air open-water flow configuration, and the solar dish concentrators are utilized for water heating. Examination of three different shapes of cavity receiver including cylindrical, cubical and hemispherical, as the solar dish absorbers, was carried out. Thermal oil was considered as the solar working fluid. The absorbed solar heat was transferred to the desalination unit using a heat exchanger. In the hybrid solar desalination, photovoltaic panels were used to generate the required power. Water flow was considered at the back of the photovoltaic panels for preheating and improving the photovoltaic efficiency. The principal aim of the current study is to propose hybrid solar desalination system to generate power, and produce freshwater. The solar desalination's performance was examined in terms of various solar dish parameters and different humidification-dehumidification desalination parameters. Examination of various solar dish parameters, including the solar working fluid's inlet temperature and the cavity shapes, was carried out. Also, some humidification-dehumidification desalination parameters, including the water to air flow ratio and the water flow rate, were considered. The effects of these four parameters were investigated on the water production and the gain output ratio. Based on the results, it was found that there was an increase in the production of freshwater by raising the water flow rate, decreasing the solar working fluid inlet temperature and increasing the air flow rate. Besides, there was an increase in the gain output ratio by increasing the water flow rate, increasing the inlet temperature, and increasing the air flow rate. Finally, the highest freshwater production and lowest gain output ratio were resulted by the hemispherical cavity receiver.

Mathematical modeling of an integrated system for regeneration of solid desiccants using a solar parabolic dish concentrator

In this work, an integrated system is introduced to regenerate the desiccant materials in solar air conditioning systems. A solar parabolic dish collector and a helically baffled cylindrical cavity receiver were coupled to two series finned-tube heat exchangers, and a fixed bed filled with silica gel. A silicone oil as heat transfer fluid absorbs the solar energy and heats the air to regenerate the silica gels in the bed. The system was studied both experimentally and theoretically. A comprehensive mathematical model was developed for the entire system, and the proposed model was validated with experimental data. The regeneration rate of the desiccant materials and the average daily thermal regeneration efficiency of the system were obtained up to 0.4 kg water/h m2 and 30% respectively, which compared to the other solar systems, the present system has a good performance and is more efficient. Based on the weather conditions of the installed location of the system, the operational or even geometrical parameters of the system can be designed in such a way that for specified required cooling capacity, the system can provide the required energy for regeneration of desiccant materials. The system performance was studied during a sample day based on real solar irradiation intensity and ambient conditions, and the influence of the effective parameters was investigated on the regeneration rate of the silica gels.