Parabolic Dish Concentrator Research Articles

Opto–geometric performance of fixed-focus solar concentrators

In this paper, the opto–geometric performance of fixed-focus solar concentrators (FFSCs), namely, the high temperature concentrator (HTC), the Scheffler concentrator and the Scheffler-type solar concentrator (STSC), is analysed. The goal of this study is to determine the behaviours of FFSCs as a function of their dimensions and to compare the results to the results of parabolic dish (PD) solar concentrators. An algorithm based on opto–geometric models of these concentrators was developed, and numerical calculations were performed for each type in a range of thermal power of 1–50kW.The numerical results indicate that FFSCs require a reflector with a diameter 45% larger than the diameter of a PD concentrator and increase the diameter of the solar image at the receiver by 350% compared with a PD concentrator. The increase in the diameter of the solar image by the fixed receiver in the FFSC produces a lower concentration. For thermal demands of less than 10kW, FFSCs do not have significantly large dimensions. The proposed algorithm can be employed to evaluate the potential use of FFSCs and an FFSC instead of a PD concentrator because of the operational advantages of the fixed receivers of the different types.

An advanced solution to boost sun-to-electricity efficiency of parabolic dish

This paper investigates the coupling of parabolic dish concentrator with air micro gas turbine engine (net power output equal to 32.9kWel). With the aim of increasing the conversion efficiency of the incoming solar radiation, a high temperature system (up to 1100°C) has been considered: this solution implies the adoption of a ceramic expander coupled with a high temperature indirectly-irradiated solar receiver. A flexible Matlab® suite has been developed for the plant sizing and for the part-load simulation; in addition, the model is able to handle general solar field configurations through the computation of reciprocal shading effect. The obtained yearly sun-to-electric efficiency (26.48%) reveals the energetic advantage over other CSP technologies that can mitigate the technological issues and consequently higher investment cost, related to high operating temperatures. The potential of a hybrid version of the dish is also discussed.

Solar Torrefaction of Solid Olive Mill Residue

Torrefaction is a thermochemical pretreatment method for improving fuel characteristics of biomass. The process is conducted between 200 and 300 °C under inert atmosphere. The relatively low process temperature of torrefaction makes the use of solar energy suitable with low costs. In this study, solid olive mill residue (SOMR) was used to test the feasibility of using solar energy in the torrefaction process. SOMR is an agricultural waste obtained from olive oil extraction, and it is mainly produced in the Mediterranean region, which has high solar energy potential. In this study, the torrefaction of SOMR was conducted by concentrating solar energy with a parabolic dish concentrator, at 250 °C for 10 min. The fuel properties of solar torrefaction products were compared with raw SOMR. Solar torrefaction yielded a deoxygenated solid fuel with increased carbon content and higher heating value (HHV), similar to torrefaction.

Thermodynamic analysis of an organic rankine cycle using a tubular solar cavity receiver

In this study, a non-regenerative Organic Rankine Cycle (ORC) has been thermodynamically analyzed under superheated conditions, constant evaporator pressure of 2.5MPa, and condenser temperature of 300K. R113, R601, R11, R141b, Ethanol and Methanol were employed as the working fluid. A parabolic dish concentrator with a square prismatic tubular cavity receiver was used as the heat source of the ORC system. The effects of the tube diameter, the cavity depth, and the solar irradiation on the thermodynamic performance of the selected working fluid were investigated. Some thermodynamic parameters were analyzed in this study. These thermodynamic parameters included the thermal efficiency, second law efficiency, total irreversibility, availability ratio, mass flow rate, and net power output. The results showed that, among the selected working fluids, methanol had the highest thermal efficiency, net power output, second law efficiency, and availability ratio in the range of turbine inlet temperature (TIT) considered. On the other hand, methanol had the smallest total irreversibility in the same range of TIT. The results showed also that mass flow rate and consequently the net power output increased for higher solar irradiation, smaller tube diameter, and for the case of cubical cavity receiver (i.e. cavity depth h equal to the receiver aperture side length a).

Solar parabolic dish Stirling engine system design, simulation, and thermal analysis

Modeling and simulation for different parabolic dish Stirling engine designs have been carried out using Matlab®. The effect of solar dish design features and factors such as material of the reflector concentrators, the shape of the reflector concentrators and the receiver, solar radiation at the concentrator, diameter of the parabolic dish concentrator, sizing the aperture area of concentrator, focal Length of the parabolic dish, the focal point diameter, sizing the aperture area of receiver, geometric concentration ratio, and rim angle have been studied. The study provides a theoretical guidance for designing and operating solar parabolic dish Stirling engines system. At Zewail city of Science and Technology, Egypt, for a 10kW Stirling engine; The maximum solar dish Stirling engine output power estimation is 9707W at 12:00PM where the maximum beam solar radiation applied in solar dish concentrator is 990W/m2 at 12:00PM. The performance of engine can be improved by increasing the precision of the engine parts and the heat source efficiency. The engine performance could be further increased if a better receiver working fluid is used. We can conclude that where the best time for heating the fluid and fasting the processing, the time required to heat the receiver to reach the minimum temperature for operating the Solar-powered Stirling engine for different heat transfer fluids; this will lead to more economic solar dish systems.Power output of the solar dish system is one of the most important targets in the design that show effectiveness of the system, and this has achieved when we take into account many factors in the design of the solar dish system. One of these factors is the reflector material of the concentrator and using the results from the Matlab simulation program; where the Polymeric Film, Non Metal reflectors, with a net conversion power of more than 97.07%, still holds the conversion record than the Anod Aluminum reflectors, which has a net conversion power 85.97% with respect to the polished stainless reflectors with a net conversion power 49.52% from the 10kW Stirling engine. Where the power output differ as 9707, 4952, 8597W, respectively from the 10kW Stirling engine. It is shown that there are changes in Stirling power output for different materials, which guide us to select the optimum material, based on the targeted power output and cost. Our target to reach the optimum power that we need it in the design 10kW power output design as an example from the solar dish Stirling engine.

Step tracking program for concentrator solar collectors

The increasing living standards in developed countries lead to increased energy consumption. The fossil fuel consumption and greenhouse gas effect that accompany the energy production can be reduced by using renewable energy. For instance, the solar thermal systems can be used in temperate climates to provide heating during the transient period or cooling during the warmer months. Most used solar thermal systems contain flat plate solar collectors. In order to provide the necessary energy for the house cooling system, the cooling machine uses a working fluid with a high temperature, which can be supplied by dish concentrator collectors. These collectors are continuously rotated towards sun by biaxial tracking systems, process that increases the consumed power. An algorithm for a step tracking program to be used in the orientation of parabolic dish concentrator collectors is proposed in the paper to reduce the consumed power due to actuation. The algorithm is exemplified on a case study: a dish concentrator collector to be implemented in Brasov, Romania, a location with the turbidity factor TR equal to 3. The size of the system is imposed by the environment, the diameter of the dish reflector being of 3 meters. By applying the proposed algorithm, 60 sub-programs are obtained for the step orientation of the parabolic dish collector over the year. Based on the results of the numerical simulations for the step orientation, the efficiency of the direct solar radiation capture on the receptor is up to 99%, while the energy consumption is reduced by almost 80% compared to the continuous actuation of the concentrator solar collector.

Illustrations of Efficient Solar Driven Organic Reactions

The article covers some of the important prior art on solar-mediated organic transformations. It additionally highlights recent initiatives from our laboratory toward use of concentrated solar radiation to drive thermochemical and photo-thermochemical organic reactions. Solar radiation (800-1000 W m-2) comprises a continuum of photons of various wavelengths – from ultraviolet (uv) to visible (vis) to infrared (IR) – covering a part of the electromagnetic spectrum. In the context of organic synthesis, uv-vis radiation helps drive reactions via the excited state of substrate or reagent while IR radiation can provide thermal energy. Single sun exposure limits the photon flux and maximum attainable temperature. On the other hand, concentrated radiation provides higher photon flux and also helps generate higher temperatures. This assists in speeding up reactions and/or conducting reactions at larger scale. A laboratory scale solar photo-thermochemical reactor in V-trough configuration was developed that generated reaction temperatures up to 80 °C besides providing ca. two fold higher photon flux. It was used successfully to conduct a variety of photo-thermochemical bromination reactions in efficient manner. Benzylic bromination of p-methylstyrene-based inter-polymer film was also carried out successfully. Tandem reactions were also developed for the synthesis of more complex molecules such as oxazole derivatives from simple building blocks. The reactions presumably occurred via intermediate formation of halo derivatives. Radiation from parabolic dish concentrators provide still higher levels of concentration of solar radiation. These were used to drive useful thermochemical processes such as the energetically uphill conversion of dicyclopentadiene to cyclopentadiene (Cp) and further downstream processes such as Diels-Alder synthesis of a norbonadiene derivative from Cp. A continuous process of production of β-bromostyrene from cinnamic acid was also explored using radiation from a parabolic trough. Concentrated radiation was additionally employed for distillation of a variety of organic solvents. Keywords: Solar driven synthesis, bromo derivatives, oxazole derivatives, -bromostyrene derivatives, solar energy storage, continuous process.

Mechanical design of a low cost parabolic solar dish concentrator

The objective of this research was to design a low cost parabolic solar dish concentrator with small-to moderate size for direct electricity generation. Such model can be installed in rural areas which are not connected to governmental grid. Three diameters of the dish; 5, 10 and 20m are investigated and the focal point to dish diameter ratio is set to be 0.3 in all studied cases. Special attention is given to the selection of the appropriate dimensions of the reflecting surfaces to be cut from the available sheets in the market aiming to reduce both cutting cost and sheets cost. The dimensions of the ribs and rings which support the reflecting surface are optimized in order to minimize the entire weight of the dish while providing the minimum possible total deflection and stresses in the beams. The study applies full stress analysis of the frame of the dish using Autodesk Inventor. The study recommends to use landscape orientation for the reflective facets and increase the ribs angle and the distance between the connecting rings. The methodology presented is robust and can be extended to larger dish diameters.

Stand alone triple basin solar desalination system with cover cooling and parabolic dish concentrator

A stand-alone triple basin solar desalination system is experimentally tested and the results are discussed in this paper. This system mainly consists of a triple basin glass solar still (TBSS), cover cooling (CC) arrangement, parabolic dish concentrator (PDC) and photovoltaic (PV) panel. Four triangular hollow fins are attached at the bottom of the upper and middle basin in order to increase the heat transfer rate and place the energy storing materials. The performance of the system is studied by, conventional TBSS system, integrating the TBSS with CC, TBSS with PDC, and TBSS with CC and PDC. Also, each configuration is tested further by using fins without energy storing material, fins filled with river sand, and fins filled with charcoal. The results of the test reveal that, TBSS with charcoal and TBSS with river sand enhance the distillate by 34.2 and 25.6% higher than conventional TBSS distillates. TBSS with cover cooling reduces the glass temperature to about 8 °C compared to the conventional TBSS. The presence of concentrator increases the lower basin water temperature upto 85 °C. The maximum distillate yield of 16.94 kg/m2.day is obtained for TBSS with concentrator, cover cooling and charcoal in fins.

Optical analysis and performance evaluation of a solar parabolic dish concentrator

In this study, the optical design of a solar parabolic dish concentrator is presented. The parabolic dish concentrator consists from 11 curvilinear trapezoidal reflective petals made of polymethyl methacrylate with special reflective coating. The dish diameter is equal to 3.8 m and the theoretical focal point distance is 2.26 m. Numerical simulations are made with the commercial software TracePro from Lambda Research, USA, and the final optimum position between absorber and reflector was calculated to 2.075 m; lower than focus distance. This paper presents results for the optimum position and the optimum diameter of the receiver. The decision for selecting these parameters is based on the calculation of the total flux over the flat and corrugated pipe receiver surface; in its central region and in the peripheral region. The simulation results could be useful reference for designing and optimizing of solar parabolic dish concentrators as for as for CFD analysis, heat transfer and fluid flow analysis in corrugated spiral heat absorbers.

Dynamic Simulation and Optimization of Rhombic Drive Stirling Engine Using MSC ADAMS Software

In this work, a Beta type Stirling engine with rhombic drive is simulated and optimized using MSC ADAMS software to enhance engine performance. Schmidt model is adopted to determine the instantaneous gas pressure. Hence, the exerted forces on the power piston can be calculated. The model is designed with low to moderate temperature difference in order to facilitate the use of low cost evacuated tubes solar collector. This is in contrast to the use of high cost double axes tracking parabolic dish concentrator that results high temperature difference. All gas forces, friction forces at joints, masses and inertias as well as temperatures of expansion and compression chambers were considered in the model. Simulation at different external loads are carried out and Power-Speed curves for the engine are obtained. The performance optimization based on the dynamic model obtained from the software is formulated. The dimensions of all rhomboid mechanism links, diameters of displacer and piston, and the length of displacer are set as the design variables. The masses and the inertias of the links are set as function of their lengths to account for the variation of the links’ dimensions during optimization. The mass of the working gas is kept constant to maintain the input energy at certain value. Results showed that a great increase in the output power could be achieved by optimizing the geometrical parameter of the engine drive.

Design, simulation and optimization of a solar dish collector with spiral-coil thermal absorber

The efficient conversion of solar radiation into heat at high temperature levels requires the use of concentrating solar collectors. The goal of this paper is to present the optical and the thermal analysis of a parabolic dish concentrator with a spiral coil receiver. The parabolic dish reflector consists of 11 curvilinear trapezoidal reflective petals constructed by PMMA with silvered mirror layer and has a diameter of 3.8 m, while its focal distance is 2.26m. This collector is designed with commercial software SolidWorks and simulated, optically and thermally in its Flow Simulation Studio. The optical analysis proved that the ideal position of the absorber is at 2.1m from the reflector in order to maximize the optical efficiency and to create a relative uniform heat flux over the absorber. In thermal part of the analysis, the energetic efficiency was calculated approximately 65%, while the exergetic efficiency is varied from 4% to 15% according to the water inlet temperature. Moreover, other important parameters as the heat flux and temperature distribution over the absorber are presented. The pressure drop of the absorber coil is calculated at 0.07bar, an acceptable value.

Ray Tracing Study of Optical Characteristics of the Solar Image in the Receiver for a Thermal Solar Parabolic Dish Collector

This study presents the geometric aspects of the focal image for a solar parabolic concentrator (SPC) using the ray tracing technique to establish parameters that allow the designation of the most suitable geometry for coupling the SPC to absorber-receiver. The efficient conversion of solar radiation into heat at these temperature levels requires a use of concentrating solar collectors. In this paper detailed optical design of the solar parabolic dish concentrator is presented. The system has diameter D=3800 mm and focal distance f=2260 mm. The parabolic dish of the solar system consists of 11 curvilinear trapezoidal reflective petals. For the construction of the solar collectors, mild steel-sheet and square pipe were used as the shell support for the reflecting surfaces. This paper presents optical simulations of the parabolic solar concentrator unit using the ray tracing software TracePro. The total flux on the receiver and the distribution of irradiance for absorbing flux on center and periphery receiver are given. The goal of this paper is to present the optical design of a low-tech solar concentrator that can be used as a potentially low cost tool for laboratory scale research on the medium-temperature thermal processes, cooling, industrial processes, polygeneration systems, and so forth.

Performance Evaluation of a Paraboloidal Concentrator

This research aims are to design, build and analyze the performance of concentrated solar energy onto a simple calorimeter, made of copper and stainless steel. A scrapped yard antenna dish with a diameter of 1.68 meters was lined with aluminum foil reflector sheet. The average dish aperture area of 2.21 m2, the system uses water as a heat transfer fluid distributed from overhead tank. Absorbed energy was investigated at a water flow rate of 0.5 L/min were performed in the experiment and the maximum useful energy was determined. Parabolic dish concentrator displacement angle was adjusted in every 15 degrees per hour, with the used of electric controlled sun tracking system. The experimental tests carried out in Faculty of Industrial Technology, Vallaya Alongkorn Rajabhat University Pathum Thani, under Thailand climatic conditions (14.134°N, 100.611°E) during 2 selected days of the months April 2013. The performance of a paraboloidal concentrator was assessed using open-air experimental measurements including the incoming heat, the energy absorbed by the water, and the concentrator efficiency. The experimental results shown the maximum thermal efficiency was 89.73%. It was also found that copper calorimeter can simply attain during operation relatively high water temperature levels oncoming 97 °C. The concentrated solar flux at the focal point was 442,073.11W/m2 for stainless steel calorimeter and 619,448.66 W/m2 for copper calorimeter, respectively.

Thermal Performance of Solar Parabolic Dish Concentrator with Hetero-Conical Cavity Receiver

Concentrated solar collectors have high efficiency as compared to flat plate and evacuated tube solar collectors. Cavity receivers are mainly used on the parabolic dish concentrators and tower type concentrator systems. The heat transfer surfaces of cavity receiver are composed by coiled metal tube. Heat transfer fluid flows in the internal spaces of coiled metal tube, and the external surfaces would absorb the highly concentrated solar energy. This paper explains the thermal performance of parabolic dish concentrator system with hetero-conical cavity receiver. The experimental analysis was done during the month of April 2014 on clear sunny days at Chennai [Latitude: 13.08oN, Longitude: 80.27oE] to study its thermal performance.

Integrated solar thermal Brayton cycles with either one or two regenerative heat exchangers for maximum power output

The main objective of this paper is to optimise the open-air solar-thermal Brayton cycle by considering the implementation of the second law of thermodynamics and how it relates to the design of the heat exchanging components within it. These components included one or more regenerators (in the form of cross-flow heat exchangers) and the receiver of a parabolic dish concentrator where the system heat was absorbed. The generation of entropy was considered as it was associated with the destruction of exergy or available work. The dimensions of some components were used to optimise the cycles under investigation. EGM (Entropy Generation Minimisation) was employed to optimise the system parameters by considering their influence on the total generation of entropy (destruction of exergy). Various assumptions and constraints were considered and discussed. The total entropy generation rate and irreversibilities were determined by considering the individual components and ducts of the system, as well as their respective inlet and outlet conditions. The major system parameters were evaluated as functions of the mass flow rate to allow for a proper discussion of the system performance. The performances of both systems were investigated, and characteristics were listed for both. Finally, a comparison is made to shed light on the differences in performance.

Design and Dynamic Simulation of a Combined System Integration Concentrating Photovoltaic/Thermal Solar Collectors and Organic Rankine Cycle

This study presents the design of a novel ultra-high efficient solar power system. The system is equipped with a concentrating PhotoVoltaic/Thermal (CPVT) solar collectors bottomed by an Organic Rankine Cycle (ORC). The basic idea is to use a high temperature CPVT device producing simultaneously electricity and hot diathermic oil. Then, this hot fluid is used to supply heat to the Organic Rankine Cycle producing additional electricity. The collector is based on a combination of a parabolic dish concentrating solar thermal collector and a high efficiency solar photovoltaic collector. Among the possible high-temperature PVT systems, this paper is focused on a system consisting in a dish concentrator and in a triple-junction PV layer. In particular, the prototype consists in a parabolic dish concentrator and a planar receiver. The system is equipped with a double axis tracking system. The bottom surface of the receiver is equipped with triple-junction silicon cells whereas the top surface is insulated. Similarly, the ORC subsystem is equipped with tube and shell heat exchangers, a pump and an expander. In order to analyze the performance of the CPVT collector and ORC cycle, detailed mathematical models were implemented. These models are based on zero-dimensional energy balances on the control volumes of the system. The simulation model allows one to calculate in detail the temperatures of the main components of the system and the main energy flows. Both CPVT and ORC models are integrated in a more complex dynamic simulation model, developed in TRNSYS environment. Here, additional components are included in the system: Pump, tank, controllers, valves, etc. The input parameters of the model include weather conditions (temperature, insolation, wind velocity, etc.) and the geometrical/material parameters of the systems. This novel system was compared with a more conventional one, consisting of a concentrating PV collector equipped with III-V cells. Results showed that such second system (only CPVT) is more profitable from an economical point of view, with a 20 years Net Present Value 15% higher than the novel system (CPVT+ORC). Conversely, the novel (ORC+CPVT) system produces 6% more electrical energy.

Study on Concentrating Characteristics of a Solar Parabolic Dish Concentrator within High Radiation Flux

Concentrating characteristics of the sunlight have an important effect on the optical-thermal conversion efficiency of solar concentrator and the application of the receiver. In this paper, radiation flux in the focal plane and the receiver with three focal lengths has been investigated based on Monte Carlo ray-tracing method. At the same time, based on the equal area-height and equal area-diameter methods to design four different shape receivers and numerical simulation of radiation flux distribution characteristics have also been investigated. The results show that the radiation flux in the focal plane increases with decreasing of the focal length and the diameter of the light spot increases with increasing of the focal length. The function of the position with a maximum of radiation flux has been obtained according to the numerical results. The results also show that the radiation flux distribution of cylindrical receiver has the best performance in all four receivers. The results can provide a reference for future design and application of concentrating solar power.

Experimental performance investigation of modified cavity receiver with fuzzy focal solar dish concentrator

In this paper, thermal performance analysis of 20 m2 prototype fuzzy focal solar dish collector is presented. The focal image characteristics of the solar dish are determined to propose the suitable design of absorber/receiver. First, theoretical thermal performance analysis of the fuzzy focal solar parabolic dish concentrator with modified cavity receiver is carried out for different operating conditions. Based on the theoretical performance analysis, the total heat loss (conduction, convection and radiation heat losses) from the modified cavity receiver is estimated. It is observed that the maximum theoretical efficiencies of solar dish collector are found to be as 79.2% for no wind conditions and 78.2% and 77.8% for side-on and head-on winds speed of 5 m/s respectively. Latter, real time analysis of parabolic dish collector with modified cavity receiver is carried out in terms of stagnation test, time constant test and daily performance test. From stagnation test, the overall heat loss coefficient is found to be 356 W/m2 K. The time constant test is carried out to determine the influence of sudden change in solar radiation at steady state conditions. The daily performance tests are conducted for different flow rates. It is found that the efficiency of the collector increases with the increase of volume flow rates. The average thermal efficiencies of the parabolic dish collector for the volume flow rate of 100 L/h and 250 L/h are found to be 69% and 74% for the average beam radiation (Ibn) of 532 W/m2 and 641 W/m2 respectively.

Experimental performance evaluation of a stand-alone point-focus parabolic solar still

A stand-alone point-focus parabolic solar still (PPSS) was designed and fabricated for desalination of seawater or brackish water and purification of non-potable water. The system consists of a parabolic dish concentrator; a two axis sun tracker based on programmable logic controllers (PLCs) and two plate heat exchangers (PHEs) to preheat the salt water before entering the absorber located at the focal point as well as condense the generating steam. Distillate productivity of the PPSS was measured along with evaluation of the effects of environmental and operational parameters that includes: beam solar insolation, wind speed, air temperature, absorber wall temperature and raw water salinity under the climatic conditions of Tehran during October. The maximum productivity of 5.12kg within 7h in a day was measured with the maximum average solar insolation of 626.8W/m2 and the absorber wall temperature of 150.7°C. However, no significant effect of air temperature, wind speed, and water salinity on the productivity was observed. The maximum daily efficiency of 36.7% was calculated with a maximum hourly output of 1.5kg/h. The quality of lab-prepared salt water samples was analyzed before and after desalination and the results comply with the WHO guidelines for drinking water quality.