Concentrated Solar Radiation Research Articles

Optimization and performance analysis of a solar concentrated photovoltaic-thermoelectric (CPV-TE) hybrid system

This work presents, for the first time, a statistical model to forecast the electrical efficiency of concentrated photovoltaic-thermoelectric system (CPV-TE). The main objective of this work is to analyze the impact of the input factors (product of solar radiation and optical concentration, external load resistance, leg height of TE and ambient temperature) most affecting the electrical efficiency of CPV-TE system. An innovative and integrated approach based on a multi-physics numerical model coupling radiative, conductive and convective heat transfers Seebeck and photoelectrical conversion physical phenomena inside the CPV-TE collector and a response surface methodology (RSM) model was developed. COMSOL 5.4 Multiphysics software is used to perform the three-dimensional numerical study based on finite element method. Furthermore, results from the numerical model is then analysed using the statistical tool, response surface methodology. The analysis of variance (ANOVA) is conducted to develop the quadratic regression model and examine the statistical significance of each input factor. The results reveal that the obtained determination coefficient (R2) for electrical efficiency is 0.9945. An excellent fitting is achieved between forecast values obtained from the statistical model and the numerical data provided by the three-dimensional numerical model. The influence of the parameters in order of importance on the electrical efficiency are respectively: product of solar radiation and optical concentration, the height legs of TE, external electrical resistance load, and ambient temperature. A simple polynomial statistical model is created in this work to predict and maximize the electrical efficiency from the solar CPV-TE system based on the four investigated input parameters. The maximum electrical efficiency of the proposed CPVTE (17.448%) is obtained for optimum operating parameters at 229.698 W/m2 value of product of solar radiation and optical concentration, 303.353 K value of ambient temperature, 2.681Ω value of resistance electrical load and at 3.083 mm value of height of TE module.

Study of the Impact of PV-Thermal and Nanofluids on the Desalination Process by Flashing

In this study, a mathematical and numerical modeling of the photovoltaic (PV)-thermal solar system to power the multistage flashing chamber process is presented. The proposed model was established after the mass and energy conservation equations written for finite control volume were integrated with properties of the water and nanofluids. The nanofluids studied and presented herein are Ai2O3, CuO, Fe3O4, and SiO2. The multiple flashing chamber process was studied under various conditions, including different solar radiation levels, brine flows and concentrations, and nanofluid concentrations as well as flashing chamber temperatures and pressures. Solar radiation levels were taken as 500 w/m2, 750 w/m2, 1000 w/m2, and finally, 1200 w/m2. The nanofluid volumetric concentrations considered varied from 1% to 20%. There is clear evidence that the higher the solar radiation, the higher the flashed flow produced. The results also clearly show that irreversibility is reduced by using nanofluid Ai2O3 at higher concentrations of 10% to 20% compared to water as base fluid. The highest irreversibility was experienced when water was used as base fluid and the lowest irreversibility was associated with nanofluid SiO2. The irreversibility increase depends upon the type of nanofluid and its thermodynamic properties. Furthermore, the higher the concentration (e.g., from 10% to 20% of Ai2O3), the higher the availability at the last flashing chamber. However, the availability is progressively reduced at the last flashing chamber. Finally, the predicted results compare well with experimental data published in the literature.

Analysis of Innovations in Concentration of Solar Radiation

As part of my research work carried out successfully at the level of Master 2 in 2016, in the laboratory of Electrical Engineering, Mechatronics and Signal Processing, I designed a TVS central, which allowed me to replace the use of diesel fuel by solar energy in the production of electrical energy. This solar power plant was named: TVS system. Its solar energy collector is parabolic and well suited to urban areas. I have noticed that its installation, operation and maintenance are complex and require good training for officers working at the plant. The rural area is not electrified in Cameroon it has been very interesting to extend the use of the TVS system in rural areas since water and the sun being available in these places, it will work with steam which will allow to have a kW at lower cost. It will be a question for me in the context of performance research in the production of electricity, to redesign the TVS system with innovative solar energy collection equipment which also allows to add a thermal storage system to overcome lack of sunshine at night. The process of producing electricity from solar radiation is complex for concentrated solar energy, but direct for voltaic panels. Since the solar energy is not very dense, it is necessary to concentrate it to obtain exploitable temperatures for the production of high-power electricity. These sought temperatures are between 400°C and 600°C. Figure 1 below shows the capture of solar radiation and the movements of the thermal energy received until its transformation into mechanical movement driving the alternator. The solar energy production sector has become dynamic all over the world and we are witnessing various promising innovations which will announce the primordial place that renewable energies will occupy in the near future. Today, solar energy is estimated at 19% of the world's electric energy. During my thesis work, I propose to: analyze of innovations in concentration of solar radiation. [10]

Concentrated solar radiation as a renewable heat source for a preparative-scale and solvent-free Biginelli reaction

Highly sustainable, economical, and faster Biginelli reaction has been established using concentrated solar radiation.

Photo-Thermal Conversion Efficiency of Spectrally Selective Cr <sub>2</sub>O <sub>3</sub>/Cr/Cr <sub>2</sub>O <sub>3</sub> Multilayered Solar Absorber

Renewable energy is the alternative resource to deal with environmental problems and to satisfy the ever-increasing energy demand. Concentrating Solar Power (CSP) systems are valuable candidates to harness solar energy. CSP systems first convert solar radiation into thermal energy which is much easier and economical than storing electricity. The solar absorbing surface is the critical part of CSP systems, as it directly affects the efficiency of the solar thermal energy conversion into electricity. To achieve high conversion efficiency of incident light into heat, the solar absorber should be spectrally selective. To obtain this spectral selectivity, various designs such as absorbing semiconductor-metal tandems, composite films and multilayer interference stacks with multiple dielectric and metallic thin films have been used such as Cr2O3, Al2O3, HfO2, Ni, Cr, and Zr. However, their optical properties determine the efficiency of the energy conversion from the concentrated solar irradiation to the thermal energy recovered by the heat transfer fluid or nanofluid. This paper experimentally investigates on the photo-thermal conversion efficiency of Cr2O3/Cr/Cr2O3 multilayered selective solar absorber (SSA) deposited onto stainless steel substrates by using an electron beam physical vapor deposition technique. Interestingly, the fabricated Cr2O3/Cr/Cr2O3 SSA showed good photo-thermal conversion efficiency with a peak temperature exceeding 180 °C after an irradiation time of 2500 s; this obtained value is comparable to the performance of state-of-the-art SSA surfaces.

Thermo-Economic Optimization of Solar Thermal Devices by Coherent Integration of Technologies

Radiation is a form of energy where the angular variable of the direction of its photons has a primary importance, particularly for radiation concentration processes, which are essential tools to reach high temperatures from radiation beams (as the solar ones) with moderate intensities. Solar radiation cannot be used directly to feed thermodynamic cycles, and optical concentration must be applied to that goal. In general, reflection from mirrors is preferred to refraction by lenses in this case, because they have less optical aberrations. Concentration conveys very high temperatures in the receiver. However, the higher the temperature, the lower the efficiency of the solar thermal apparatus. Besides that, economy also suffers quite a lot when going to very high concentration factors, which is one of the main burdens in the development of Solar Thermal Energy. A new configuration of solar radiation concentrator is presented. It includes a salient innovation in the way the mirrors are given the right curvature by mechanical forces. Those mirrors are originally flat and do not need any special thermal treatment for this purpose. The whole device concept has been guided by the principle of thermoeconomic coherence, which requires similar efforts in all degrees of freedom that have strong influence in the performance and cost of the system. The paper shows the decision tree that has oriented the project, following the principle of equilibrium in efforts, which leads to a design window of moderate values in the main variables. The prototype of this new configuration has already been built, and the first stage of research is considered to be finished, because the prototype has shown excellent conditions to include selected (fitting) technologies at a very low cost.

Паркетирование поверхности параболического концентратора солнечного теплофотоэлектрического модуля по заданным дифференциально-геометрическим требованиям

The article discusses the geometric aspects of the design and creation of parabolic-type solar radiation concentrators. Practical methods of geometric design and manufacturing of concentrators of this kind are presented. Parabolic type concentrator is the main part of the solar photovoltaic thermal installation. Its effectiveness depends on the quality factors of the geometric shaping of the working surface, composed of a set of parquet components, linked to each other on the basis of differential geometric requirements. The distribution of illumination in the focal spot of such a concentrator, made by parquet based on the constructive connection of individual elements, makes it possible to obtain acceptable results. However, there is considerable potential for improving performance by providing a smoother and more uniform illumination of the photodetector. To ensure the specified accuracy and smoothness of the rim of the surface at the stages of designing and manufacturing the device, two methods are proposed: orthogonal and fan-shaped geometric parquetting of the surface of a parabolic concentrator with the ability to pre-set the required shape accuracy for given rim geometrical characteristics. Parquetting with given differential requirements for the surface, in turn, provides for two methods for calculating parquet elements: first, by the minimum number of curvilinear elements followed by stitching, taking into account the differential conditions; the second is based on the maximum number of flat elements, the multiplicity of which provides acceptable smooth surface properties. In this paper, we consider the first method for cases of orthogonal and fan parquet. On the example of a parabolic concentrator, the implementation of the considered method is presented, which provides for the possibility of controlling the geometric smoothness of the concentrator surface in order to ensure optimal distribution of concentrated solar radiation in the focal region. The output characteristics of photovoltaic and thermal converters of solar energy, which are in the focus of such a concentrator, become optimal, and the installation itself will operate in nominal mode.

EXERGY ANALYSIS OF DIRECT SUN RADIATION CONCENTRATION

In the article substantiates that the exergy method of thermodynamic analysis, along with the entropy method, makes it possible to determine the locations of the most significant thermodynamic losses in energy conversion processes. It is shown that the use of exergy analysis makes it possible to estimate the thermodynamic losses at each stage of the energy conversion scheme and to reduce them. It is proved that exergetic analysis of the concentration of solar radiation in solar installations with paraboloid mirrors, as well as in optical systems of tower solar thermal plants with horizontal fields of flat heliostats and thermal power plants with horizontal parabolic cylindrical mirrors will allow to increase the energy of these transformations. Exergy analysis of the concentration of solar radiation was performed. For the first time, solar radiation is treated as radiant heat flux, which is characterized by its own temperature, and its exergy is determined within the canonical Carnot cycle. On the basis of the new interpretation of the temperature of the radiant flux, an analytical expression was obtained for the radiation temperature of the thermal radiation of the Sun, both for direct radiation and for diffuse. The dependence of the direct solar radiation density on the mass of the atmosphere is found. The above formulas allow to calculate the radiation temperature of solar radiation and the density of exergy flux on the Earth's surface and in the focus of the concentrator mirror.

Experimental and numerical study of a hybrid solar-combustor system for energy efficiency increasing

Coupling of traditional combustion technologies with solar thermal energy is fundamental to enlarge the field of applicability and to lower the costs of renewable energy sources. A possible solution is represented by direct irradiation of a flame with concentrated solar energy, so as to increase its temperature thanks to the high absorption coefficient of combustion by-products such as soot particles. In this study, we use a detailed model of soot formation and oxidation to simulate the behaviour of a coflowing diffusion ethylene flame with and without the exposure to a concentrated solar radiation. Modelling data are compared with experimental data reported in the literature. Results confirm that our model is able to reproduce the effect of radiation both matching the temperature and soot volume fraction increase. Successively, a modified version of the solar-combustion hybrid system has been setup to test the effect of solar light orientation on the combustion process. A simulator of concentrated solar energy has been used to directly irradiate the flame from the top. Thermocouple-based temperature measurements highlighted that the flame effectively absorbed solar radiation.

Chlorophyll triggered one-pot synthesis of 3,4-dihydropyrimidin-2(1H)-ones via photo induced electron transfer reaction

The photocatalytic potential of chlorophyll has been investigated for the facile synthesis of dihydropyrimidinones utilizing concentrated solar irradiation towards sustainable energy solutions. This, one-pot, multicomponent Biginelli reaction, which involves a photoinduced electron transfer (PET) mechanism, affords a green and efficient approach for the transformation of the commercial aldehydes, β-keto ester and urea into valuable 3,4-dihydropyrimidin-2(1H)-ones with wide substrate scope and diversity. These improved reaction conditions allow the formation of a variety of substituted dihydropyrimidinones with high yields and purity in a short duration of time and mild reaction conditions.

Distribution of solar pyrolysis products and product gas composition produced from agricultural residues and animal wastes at different operating parameters

Solar energy and biomass are the two major sources of renewable energy, which can be integrated to produce heat, power and transportation fuels, chemicals and biomaterials using pyrolysis. In this work, separate samples of chicken-litter waste and rice husk of different particle sizes (280 and 500 μm) were pyrolysed with a concentrated solar radiation to produce pyrolysis gases of high calorific value. Different operating parameters were investigated under the solar pyrolysis conditions. Heating rates from 10 to 500 °C/s and temperatures in the range of 800–1600 °C, generated from a lab-scale solar furnace with maximum power capacity of 1.5 kW, were applied. Temperature was found to have the highest effect, changing the gas yield from 10 to 39 wt%; decreasing the bio-oil and char yields from 48 to 41 wt % and 42 to 18 wt%, respectively as the temperature increased from 800 to 1600 °C. The highest specific energy content of the gas (7255 kJ/kg) was obtained with the 280 μm particle size chicken litter at 1600 °C. Overall, gases produced from solar assisted biomass pyrolysis have a high concentration of combustible products that could be directly used as fuels in engines or power plants.

Study of cracking of methane for hydrogen production using concentrated solar energy

In this study, the cracking phenomenon of methane taking place in a cylindrical cavity of 16 cm in diameter and 40 cm in length under the heat of concentrated solar radiation without any catalyst is analysed. Three cases have been chosen; in all cases the primary phase contains methane and hydrogen gases. In the first case, we consider two phases; the secondary phase is a homogeneous carbon black powder with 50 nm of diameter; in the second case we have three phases where the two secondary phases are a particles powder with two diameters 20 and 80 nm and finally, a third case of five phases with a powder of four different diameters 20, 40, 60 and 80 nm. The low Reynolds K-ε turbulence model was applied. A calculation code "ANSYS FLUENT" is used to simulate the cracking phenomena where an Eulerian – Eulerian model is applied. The choice of several diameters greatly increases the calculation time but it approaches more of the physical reality of the radiation by these particles during the cracking. Results have shown that increasing the number of diameters gives higher cracking rates; the case of the powder of 4 different diameters gives the highest cracking rate. A parametric study as a function of the inlet velocity, carbon particle diameters and the intensity of solar radiation is realized. For the cracking heat, provided by the choice of the two concentrators of 5 and 16 MW/m2 used in this simulation, the CH4 inlet velocity is a decisive parameter for the cracking rate. Any increase in the inlet velocity requires more heat and this leads to a decrease in the cracking rate. For a velocity not exceeding 0.177 m/s (i.e. 0.3 L/min), both solar concentrations give the same amount of hydrogen produced. These quantities of hydrogen obtained reach maximum values for an inlet flow rate of CH4 between 0.58 L/min (i.e. 0.34 m/s) and 0.62 L/min (i.e. 0.3655 m/s) for both reactors. The results are interpreted and compared with experimental work.

Ce:Nd:YAG continuous-wave solar-pumped laser

The first emission of a Ce:Nd:YAG solar-pumped laser is reported here, to the best of our knowledge. A solar laser head was composed of a fused silica liquid light guide lens and a conical pump cavity, which coupled and redistributed the concentrated solar radiation from the focal zone of a parabolic mirror into a Ce:Nd:YAG laser rod. The laser output performance of the 5 mm diameter, 30 mm length Ce:Nd:YAG laser rod was compared with that from a 5 mm diameter, 30 mm length Nd:YAG rod. With a solar pump power of 569 W, the Ce:Nd:YAG solar laser emitted 6 W continuous-wave power at 1064nm, corresponding to a collection efficiency of 4.9 W/m2. Even though this power level was lower than the 10 W obtained by using the Nd:YAG rod, the Ce:Nd:YAG laser medium may be an alternative active medium for solar-pumped lasers.

Surface engineering of Ni-Al coatings through concentrated solar heat treatment

An improvement in the hardness, wear and corrosion resistance of a thermal-sprayed nickel-aluminium coating has been described in this paper, by using a post-deposition annealing treatment in a vertical concentrated solar radiation furnace at Plataforma Solar de Almeria, Spain. Annealing temperatures between 900 and 970 °C were used. It has been determined that the heat treatment leads to a 56% increase in hardness, 65% increase in scratch resistance and coating adhesion to the substrate, coupled with a 20% improvement in wear resistance, compared to the non-annealed reference. The improvement in mechanical properties has been related to increased heating gradient, formation of intermetallic NixAl compounds in the structure of coatings, as well as to a better compacting of coated assembly. The solar annealing treatment leads also to an improvement in the properties of coatings, with up to 87% in terms of corrosion resistance, and 20% in terms of wear resistance, comparing to the reference.

Effect of Side Reflectors on the Performance of Flat Plate Solar Collector: A Case Study for Asir Region, Saudi Arabia

The solar collector’s efficiency is directly depended upon the solar radiation intensity falling on its surface. In order to increase the solar concentration over the collector, side reflectors are introduced which will concentrate both diffuse and direct radiations from the sun toward the collector surface. Therefore, in this study the influence of side (left and right) reflectors on efficiency improvement of the flat plate solar collector (FPSC) was analyzed. For determining the optimum tilt angles of side reflector and collector, a simulation model was developed by using TRNSYS software. The results obtained from simulation were validated with the experimental results for whole year during the daytime of semiarid Asir region of Saudi Arabia. Both simulation and experimental results indicate that optimal left side reflector angle is lowest in winter with the value of 38° and highest in summer with the value of 68°, while the optimal angle of right side reflector is lowest in summer with the value of 43° and highest in winter with the value of 74.5°. The thermal efficiency of FPSC has been improved significantly by adding side reflectors. The average thermal efficiency of FPSC without reflector was 46% which was increased to 58% by adding side reflectors. The addition of side reflectors increases the concentration of solar radiation falling on the collector surface and thus increases the output temperature of water by 12 °C as compared to input water temperature. Thus, the effective size of the system was reduced by adding side reflectors as thermal efficiency was enhanced which implies less space requirement for heating an appropriate quantity of water.

Modeling of Processes of Heating and Cooling of Materials in a Solar Furnace

The processes of heating and melting of materials in a concentrated high-density solar flux at the Large Solar Furnace are studied. The possibilities of calculating the rate of heating and cooling of molten materials are shown using the example of pyroxene rocks exposed to concentrated solar radiation. The influence of the main technological factors (the heating rate of the substance to the melting point and above, as well as the cooling rate) on the quality of the melt is studied. The equation of heating due to the absorption of solar radiation is constructed taking into account convective heat transfer and heat loss due to thermal radiation. The melt cooling process is described by the Newton–Richmann law taking into account thermal conductivity, convection, and radiation. Three different types of cooling of the melt at different rates were implemented. It is shown that by choosing the melt cooling method, various cooling rates can be achieved: 102, 103, and 104 K/s. The dependences of the grain size of the material on the cooling rate were obtained. The dependences of the microstructure of the material obtained from the cooled melt on the cooling rate of the melt were analyzed. It is shown that, within the context of the model, taking into account assumptions and initial conditions, it is possible to describe the processes of heating and cooling of pyroxene rocks under the influence of concentrated solar radiation of high density. It was revealed that the melt cooling rate, which has a strong influence on the dispersion of the obtained material, is determined by the method of melt cooling. To obtain a hardened material with nanosized particles, it is necessary to cool the melt at a rate above 106 deg/s.

Optical materials for lens concentrators of solar radiation

“Solar” Abbe number is proposed to operate in assessing the suitability of optical materials at sunlight concentrators manufacture. Comparative results are presented for materials practically used in concentrator photovoltaics from the point of view of designing Fresnel lenses from them with a high average concentration in the focal spot of the minimum size and at the same time with minimum focal length.

Performance investigation of a solar water distiller integrated with a parabolic collector using fuzzy technique

AbstractA recent study of the design of solar distillation with solar radiation concentration was carried out by an independent device. Transformer oil was used as a fluid to transfer heat to the distilled basin. The design and operational variables are essential, such as distiller dimensions, concentration ratio, pressure, and temperature. A mathematical model was proposed to simulate the system for 2 July 2018 from 10 am to 4 pm in the climatic conditions of the city of Kirkuk, Iraq. Fuzzy logic (FL) was used to select the affected parameters: water temperature (Tw), water pressure (Pw), glass temperature (Tg), and vapor pressure (Pg) which have a separated membership function that control the linguistic variables. The results showed that the best performance of the distiller is at Tw = 100°C, Pg = 10 000 Pa, Tg = 20°C, and Pw = 20 000 Pa, and concentration ratio of 30. This study used FL to analyze solar distiller performance and identify optimum temperature, pressure, and concentration ratio on the productivity of solar distiller.

Solar Heat for Materials Processing: A Review on Recent Achievements and a Prospect on Future Trends

Considering works published in the literature for more than a decade (period from January 2008 till June 2019), this paper provides an overview of recent applications of the so-called “solar furnaces”, their reactors, process chambers and related devices, aiming specifically at the processing of (solid) materials. Based on the author’s own experience, some prospects on future trends are also presented. The aim of this work is to demonstrate the tremendous potentialities of the usage of solar heat for materials processing, but also to reveal the necessity of further developing solar-driven high-temperature technologies (which are required to displace the use of electricity or natural gas). In particular, it is essential to improve the temperature homogeneity conditions inside reaction chambers for materials processing using solar heat. Moreover, new innovative modular systems, practical and flexible, for capture, concentration, control and conduction of concentrated solar radiation are suggested. Solar thermal technologies for the production of electricity, as well as solar thermochemical processes for production of gases or liquids, are outside the scope of this review.

Performance, limits, and thermal stress analysis of high concentrator multijunction solar cell under passive cooling conditions

Concentration of solar radiation onto the surface of triple-junction solar cells causes high cell temperature and system failure. Recently, several cooling methods were proposed for these systems. However, quantitative evaluation of the essential heat transfer coefficients to maintain stable operation of these systems at different meteorological and operating conditions is not found in the literature. Therefore, in this study, a comprehensive three-dimensional coupled thermal and structural model is proposed for the latest triple-junction AZUR SPACE solar cell. The model is used to investigate the performance of an HCPV system under different solar concentration ratios (CRs), ambient temperature, direct solar irradiance, wind speed, backside heat transfer coefficient, and copper-II substrate area ratios. In addition, a new structure of the solar cell is proposed by modifying the typical solar cell assembly by changing the area of the rear copper layer. The results indicate that by increasing the ambient temperature, CR and direct solar irradiance significantly increase the predicted cell temperature at the same backside heat transfer coefficient. In addition, increasing copper-II substrate area ratios significantly reduces the average cell temperature at the same backside heat transfer coefficient and CR. At the highest backside heat transfer coefficient, when the copper-II substrate area increased, the cell temperature decreased to a certain limit and subsequently remained constant. Critical values of the highest backside heat transfer coefficient were about 200, 600, 1000, and 1600 W/m2 K at CRs of 50, 500, 1000, and 1500 Suns, respectively. In addition, at the highest backside heat transfer coefficient of 1600 W/m2 K, the critical area ratio values were about 2, 3, 4, and 6 at CRs of 50, 500, 1000, and 1500 Suns, respectively.