Improving Heat Transfer in Parabolic Trough Solar Collectors by Magnetic Nanofluids

A parabolic trough solar collector(PTSC)converts solar radiation into thermal energy.However,low thermal efficiency of PTSC poses a hindrance to the deployment of solar thermal power plants.Thermal performance of PTSC is enhanced in this study by incorporating magnetic nanoparticles into the working fluid.The circular receiver pipe,with dimensions of 66 mm diameter,2 mm thickness,and 24 m length,is exposed to uniform temperature and velocity conditions.The working fluid,Therminol-66,is supplemented with Fe3O4 magnetic nanoparticles at concentrations ranging from 1%to 4%.The findings demonstrate that the inclusion of nanoparticles increases the convective heat transfer coefficient(HTC)of the PTSC,with higher nanoparticle volume fractions leading to greater heat transfer but increased pressure drop.The thermal enhancement factor(TEF)of the PTSC is positively affected by the volume fraction of nanoparticles,both with and without a magnetic field.Notably,the scenario with a 4%nanoparticle volume fraction and a magnetic field strength of 250 G exhibits the highest TEF,indicating superior thermal performance.These findings offer potential avenues for improving the efficiency of PTSCs in solar thermal plants by introducing magnetic nanoparticles into the working fluid.

Energy and Cost Analysis of Processing Flat Plate Solar Collectors

In this work,a life cycle analysis is accomplished for flat plate solar collectors.The purpose of this investigation is to predict the energy consumption during the manufacturing processes that results in carbon dioxide emissions.Energy consumption and system efficiency enhancement will be studied and predicted.CES EduPack software is used to perform the analysis of the currently commercial system,and the suggested changes are implemented to increase the efficiency and make the comparison.Even though cost analysis is done,the priority of selection is given to the most energy conserving and environmentally friendly alternative.However,if the compared alternatives result in the same energy consumption and CO_(2)emissions,the cost analysis would be a better approach.It can be stated that flat plate solar collectors are sustainable and renewable energy systems that do not produce CO_(2)emissions during their active usage,but the manufacturing processes they undergo during the design contribute to the greenhouse gasses emission.

Proposal of a Solar Thermal Power Plant at Low Temperature Using Solar Thermal Collectors

To this day, only two types of solar power plants have been proposed and built: high temperature thermal solar one and photovoltaic one. It is here proposed a new type of solar thermal plant using glass-top flat surface solar collectors, so working at low temperature (i.e., below 100°C). This power plant is aimed at warm countries, i.e., the ones mainly located between -40° and 40° latitude, having available space along their coast. This land based plant, to install on the seashore, is technologically similar to the one used for OTEC (Ocean Thermal Energy Conversion). This plant, apart from supplying electricity with a much better thermodynamic efficiency than OTEC plants, has the main advantage of providing desalinated water for drinking and irrigation. This plant is designed to generate electricity (and desalinated water) night and day and all year round, by means of hot water storage, with just a variation of the power delivered depending on the season.

An Evaluation to the Performance of Evacuated Tube Solar Heaters for Arid and Hot Areas

Solar energy applications could be the best alternative to the conventional fuels for the purposes of domestic,water and space heating and some industries in the sunny,arid,and hot areas.In the present study,the performance of an evacuated tube solar heater for water heating for months of February and March was experimentally investigated.This was performed in a hot and arid area(Nasiriya City,South of Iraq).A solar heater with ten evacuated tube solar collectors with a capacity of 100 liter was used in the experiments.Each evacuated tube had a length of 1.8m with an outside diameter of 8 cm.It was observed that for the two selected months,water temperature of the solar heater reached a maximum more than 70°C during sunny days with no heat extraction from the tank of the solar heater.Moreover,heat was extracted from the solar collector with four different flowrates 0.5,0.75,1,and 1.25 l/min,respectively.The results showed that temperature of the solar heater behaved differently from the static situation.When the heat extraction begun,there was a gradual and noticeable decrease in the water temperature of the heater.The observed decrease was slight with the lowest flowrate(0.25 l/m)and becomes sharp with the highest flowrate(1.25 l/min).However,water temperature of the solar heater remained higher than 40°C for the investigated flowrates except the case of 1.25 l/min.The results showed that evacuated tube solar heater can work efficiently in arid and hot areas in winter and spring seasons when the conditions of solar radiation are suitable.

An Energy Production System Powered by Solar Heat with Biogas Dry Reforming Reactor and Solid Oxide Fuel Cell

In this paper, an energy system consisting of solar collector, biogas dry reforming reactor and solid oxide fuel cell (SOFC) has been proposed. The heat produced from the concentrating solar collector is used to drive a biogas dry reforming reactor in order to produce H2 as a fuel for SOFC, in such as system. The aim of this study is to clarify the impact of climate data on the performance of solar collector with various sizes/designs. The temperature of heat transfer fluid produced by the solar collector is calculated by adopting the climate data for Nagoya city in Japan in 2021. The amount of H2 produced from the biogas dry reforming reactor and the power generated by SOFC were simulated. The results show the temperature of heat transfer fluid (Tfb) and Tfb ratio (a) based on the length of absorber (dx) = 1 m have a peak near the noon following the trend of solar intensity (I). Results also revealed that a increases with increase in dx. It is found that the differences of Tfb and a between dx = 2 m and dx = 3 m are larger than those between dx = 1 m and dx = 2 m. It is revealed that Tfb and a are higher in spring and summer. dx = 4 m is the optimum length of solar absorber. The amount of H2 produced from the biogas dry reforming reactor as well as the power generated by SOFC is the highest in August, resulting that it is prefer to produce H2 and to generate SOFC in summer.

Performance Investigation of the Solar Chimney Power Plants Heater Case Study in Aswan, Egypt

Solar collector is a thermal device that uses the heated air in the power generation and many engineering applications. The purpose of the present work is to study the performance and temperature distribution for the solar collector which uses heated air in solar chimney power generation that it consist of three parts, a turbine-generator unit which is used in the generation of electric energy, and cylindrical chimney is fixed vertically and finally a solar collector under the climatic conditions of Egypt-Aswan is studied. This site is specified as the hottest site because the nearest of this location from the Tropic of cancer. Experiments are performed in ten summer days of May and June 2015 with different solar radiations and clarity of the sky. Hourly values of global solar radiation and some meteorological data (temperature, pressure, velocity, etc.) for measuring days are obtained by measuring devices. Inlet and outlet temperatures of air from a solar collector and velocity at junction region. In this work, attempt has been made to present the effect of environmental factors such as ambient temperature, the clarity of the sky and solar radiation on the performance of solar collector. The temperature of the base and the cover of the solar collector, the variation of solar radiation, solar collector efficiency, heat transfer coefficient, the velocity at the junction region between the chimney base, the outlet of the solar collector and temperature distribution along the air heater are discussed. A prediction for the results of the solar collector were performed by using developed theoretical model was made by this study which is based on the previous works. The numerical study has used a commercial code CFX, ANSYS 16.1 to simulate the flow through the collector. The study show that the outlet air temperatures from the solar collector and the velocity at the junction are depending on the climate condition such as ambient temperature and solar radiation, the differences in air temperature at the solar collector ranging between 8° - 24°. It is concluded that the theoretical model is basically valid for the system under study, and theCFD simulation can be used conveniently to predict the performance of the system, the comparison between them and experimental result shows a good agreement.

A Study on the Performances of Solar Air Collectors Having a Hemispherical Dimple on the Absorber Plate

In order to increase the efficiency of solar air collectors,a new variant with a protrusion is proposed in this study,and its performances are analyzed from two points of view,namely,in terms of optics and thermodynamics aspects.By comparing and analyzing the light paths of the protrusion and the dimple,it can be concluded that when sunlight shines on the dimple,it is reflected and absorbed multiple times,whereas for the sunlight shining on the protrusion,there is no secondary reflection or absorption of light.When the lighting area and the properties of the surfaces are the same,the absorption rate of the dimple is 10.3 percentage points higher than that of the protrusion.In the range of Reynolds number from 3000 to 11000,numerical simulations about the effects of the relative height(e/Dh=0.033–0.1)and relative spacing(p/e=4.5–8.5)of protrusions on air heat transfer and flow resistance show that,in terms of comprehensive evaluation coefficient(PF),the best relative height is 0.085,when the relative spacing is 5.A correlation of Nu and f with Re,e/Dh and p/e is obtained by linear regression of the results,in order to provide a useful reference for the design and optimization of this kind of solar air collector.

Enhanced efficiency in Concentrated Parabolic Solar Collector(CPSC) with a porous absorber tube filled with metal nanoparticle suspension

In this study, effects of different nanoparticles and porosity of absorber tube on the performance of a Concentrating Parabolic Solar Collector(CPSC) were investigated. A section of porous-filled absorber tube was modeled as a semi-circular cavity under the solar radiation which is filled by nanofluids and the governing equations were solved by FlexPDE numerical software. The effect of four physical parameters, nanoparticles type, nanoparticles volume fraction(φ), Darcy number(Da) and Rayleigh number(Ra), on the Nusselt number(Nu) was discussed. It turns out that Cu nanoparticle is the most suitable one for such solar collectors, compared to the commonly used Fe_3O_4, Al_2O_3, TiO_2.With the increased addition of Cu nanoparticles all the parameters φ, Da and Ra shows a significant increase against the Nu, indicates the enhanced heat transfer in such cases. As a result, low concentration of Cu nanoparticle suspension combined with porous matrix was supposed to be beneficial for the performance enhancement of concentrating parabolic solar collector.

Highly efficient energy harvest via external rotating magnetic field for oil based nanofluid direct absorption solar collector

Nanofluids based direct absorption solar collectors(DASCs) are considered as the important alternative for further improve the utilization of solar energy. However the low-quality energy and aggregation of nanoparticles obstructs their large-scale application. In this work, a new method of using magnetic nanofluids in DASCs is proposed. By this method, not only high-quality energy is got as well as the problems of blockage and corrosion in heat exchanger are well avoided. The result shows that the maximum temperature can reach 98℃ under 3 solar irradiations and the photothermal conversion efficiency can be further increased by 12.8% when the concentration is 500 ppm after adding an external rotating magnetic field. The highest viscosity of working fluid reduced by 21% when the concentration is 500 ppm at 95℃ after separating the Fe_(3)O_(4)@C nanoparticles from the nanofluids via magnetic separation technology. Meanwhile, the obtained pure base liquids with high temperature flow to heat exchanger, which also reduces the flow resistance in pipeline and avoids the problems such as blockage and corrosion in heat exchanger. This research promotes a new way for the efficient utilization of solar energy.

Numerical Investigation and Optimization of a Flat Plate Solar Collector Operating with Cu/CuO/Al_(2)O_(3)–Water Nanofluids

Nanofluids are a potential alternative to significantly improving the performance of heat transfer applications. In this work, a numerical analysis to examine the eff ect of dispersing copper(Cu), copper oxide(CuO), and aluminum(Al2O3) nanoparticles in pure water on the performance of a flat plate solar collector(FPSC) and a numerical model was proposed. The influence of the nanofluid type on the thermal efficiency was critically investigated and discussed. The eff ect of the mass flow rate on the performance was also analyzed and discussed. Based on correlations of the thermophysical properties of nanofluids, a sensitivity analysis was used to analyze the impact of the nanoparticles on the base fluid. The results indicate that the performance of the FPSC with Cu/water nanofluid was better than that of FPSCs using CuO/water or Al2O3/water nanofluids. When the mass flow rate of the nanofluids was 8.0 L/min, the efficiency of the FPSC was much greater than those at the flow rates of 5.0 L/min and 2.0 L/min. Mean enhancements in thermal efficiency of 4.44%, 4.27%, and 4.21% were observed when 2.0 L/min was applied using Cu/water, Cu O/water, and Al2O3/water nanofluids, respectively. Improvements in thermal efficiency of 2.76%, 2.53%, and 2.47% occurred when 8.0 L/min was applied.

Dynamics and control of a solar collector system for near Earth object deflection

A solar collector system is a possible method using solar energy to deflect Earth-threatening near-Earth objects.We investigate the dynamics and control of a solar collector system including a main collector （MC） and secondary collector （SC）.The MC is used to collect the sunlight to its focal point,where the SC is placed and directs the collected light to an asteroid.Both the relative position and attitude of the two collectors should be accurately controlled to achieve the desired optical path.First,the dynamical equation of the relative motion of the two collectors in the vicinity of the asteroid is modeled.Secondly,the nonlinear sliding-mode method is employed to design a control law to achieve the desired configuration of the two collectors.Finally,the deflection capability of this solar collector system is compared with those of the gravitational tractor and solar sail gravitational tractor.The results show that the solar collector is much more efficient with respect to deflection capability.

Performance of Water in Glass Evacuated Tube Solar Water Heater under Kenya Climatic Condition

Solar water heaters which provide a cost-effective and environmental friendly approach to hot water generation are in widespread application. Evacuated tube solar water heaters perform better than flat plate solar water heaters as a result of their greater surface area exposed for sunlight absorption. Water-in-glass evacuated tube solar water heaters are widely used as compared to heat-pipe solar water heaters due to their short payback periods. In this study, the performance of water-in-glass evacuated tube solar water heater is investigated through experiments under the climatic conditions in Kenya. The results revealed a daily efficiency range of 0.58 - 0.65 and a daily final outlet temperature greater than 55°C given an initial temperature of 25°C.

Energy and Exergy Analysis of a Finned-Plate Double Pass Solar Air Heater with Different Arrangement

The present work investigated the solar collector system with triangular longitudinal fins fixed to the absorber surface at different configuration. Four models of collectors were manufactured with different absorber plates made from aluminum material. The experiments were carried out at the winter session in the climate of Iraq—Ramadi city with longitude (43.268) and latitude (33.43). The experiments have used three values from (0.027 to 0.037) kg/s. The results showed that the temperature difference increases gradually until midday and begins decreasing gradually until it becomes zero at sunset. Maximum temperatures difference has been obtained at the fourth type which is (20.6 °C), and maximum efficiency and exergetic efficiency (99.9%), (43.08%) respectively. A comparison has been made with previous works for thermal and exergetic efficiency. The comparison showed good compatibility between results; the percentage of error does not exceed 3%. The results proved that the existence of fins was a good technique for enhancing the thermal performance of double pass solar collector with a non-effective increase in pressure drop.

Torque Free Axi-Symmetric Gyros with Changing Moments of Inertia

The properties and characteristics of torque free gyros with rotational symmetry and changing moments of inertia are the subject of the subsequent discussion. It shall be understood that the symmetry can be expressed by the notation (A=B) which does not presuppose geometric symmetry, where A and B are the principle moments of inertia about x and y axes respectively. We study the case of a torque free gyro upon which no external torque is acting. The equations of motion are derived when the origin of the xyz-coordinate system coincides with the gyro’s mass center c. This study is useful for the satellites, which have rotational symmetry and changed inertia moments, the antennas and the solar power collector systems.

An Application of Nonlinear Autoregressive(NARX)Model to Predict Adsorbent Bed Temperature of Solar Adsorption Refrigeration System

In any solar adsorption refrigeration system,there are three major components:a solar collector adsorbent bed,a condenser and an evaporator.All of those components operate at different temperature levels.A solar collector with a tubular adsorbent configuration is proposed and numerically investigated.In this study,a nonlinear auto-regressive model with exogenous input is applied for the prediction of adsorbent bed temperature during the heating and desorption period.The developed neuronal model uses the MATLAB Network toolbox to obtain a better configuration network,applying multilayer feed-forward,the TANSIG transfer function,and the back-propagation learning algorithm.The input parameters are ambient temperature and the uncontrolled natural factor of solar radiation.The output network contains a variable representing the adsorbent bed temperature.The values obtained from the network model were compared with the experimental data,and the prediction performance of the network model was examined using various performance parameters.The mean square error(MSE)and the statistical coefficient of determination(R2)values are excellent numerical criteria for evaluating the performance of a prediction tool.A well-trained neural network model produces small MSE and higher R2 values.In the current study,the adsorbent bed temperature results obtained from a neural network with a two neuron in hidden layer and the number of the tapped time-delays d=9 provided a reasonable degree of accuracy:MSE=1.0121 and R2=0.99864 and the index of agreement was 0.9988.This network model,based on a high-performance algorithm,provided reliable and high-precision results concerning the predictable temperature of the adsorbent bed.

Study on carnauba wax as phase-change material integrated in evacuated-tube collector for solar-thermal heat production

The evacuated-tube collector(ETC)for solar heat production is one of the most efficient systems to convert Sun energy into usable energy.Unfortunately,some technological barriers are still present in solar-thermal heat systems that limit the use of these technologies to decarbonize processes.An important obstacle is the requirement for heat at stable temperatures,which is not always achievable by solar fields,e.g.variable sky.For that reason,in this work,we studied the phase-change materials embedded in the ETC to keep stable the water temperature for a short period(minutes,hours).In this study,carnauba wax was used as a sustainable phase-change material(PCM),to avoid the use of PCM based on hydrocarbon waxes.The PCM has been packaged using a polyethylene bag inserted into an ETC with heat-pipe technologies and tested.The collector has been tested outdoors under solar irradiation and under shading conditions.The experimental results show that is possible to detect a sensible effect of the PCM on the temperature using 4 kg of carnauba wax while there is an important effect on the temperature stabilization using 9 kg of PCM.Using 9 kg of the PCM,we observed a stability of the outlet water temperature at 65°C for 30 minutes under shading conditions.

Comparison of mixed-mode forced-convection solar dryer with and without stainless wire mesh in solar collector

A mixed-mode forced-convection solar dryer(MMFCSD)is a device that utilizes both direct and indirect solar energy.The solar col-lector,which stores thermal energy for indirect solar uses,is an essential component of the dryer.Unfortunately,the thermal effi-ciency of this device is generally low.In this study,a technique was employed to improve the heat transfer of the solar collector in a MMFCSD.The technique involved adjusting the air flow pattern into a swirling flow to disturb the thermal boundary layer on the absorber plate under forced convection by using stainless wire mesh.The experiment was conducted under actual conditions and bananas were used as the drying sample.The experimental results of the thermal efficiency of the solar collector(ƞ_(solar))and the drying efficiency(ƞ_(drying))are presented.The results indicated that the air outlet temperature andƞsolar of the solar collector with stainless wire mesh were higher than the case without stainless wire mesh,reaching a maximum temperature of 46.22°C and 37.97°C,and average ƞ_(solar) of 0.26±0.02 and 0.14±0.01,respectively.The MMFCSD with stainless wire mesh had a higher ƞ_(drying) than the case without stain-less wire mesh,with values of 0.048±0.004 and 0.039±0.003,respectively,resulting in an~23.07%increase.This was attributed to the air swirling flow through the stainless wire mesh and the heat accumulation in the drying chamber,which led to an increase in the drying chamber temperature from 54.03°C to 63.60°C,an increase in the effective moisture diffusivity from 7.28×10^(-7) to 1.19×10^(-6) m^(2)/s and a decrease in the drying time of 5 h 30 min.However,further research is needed to investigate the quality of the dried sam-ples and their economic value.

Efficiency enhancement of building multi-layer solar collector with SiO2–TiO2 hybrid nanofluids

Due to the depletion of conventional energy sources and its limitless resources,solar energy is currently being considered as a viable alternative,especially for water heating systems.The thermal performance of multilayer solar collectors for water heating systems can be improved further by introducing hybrid nanofluids as advanced fluids.This study demonstrates the utilisation of hybrid nanofluids in heating systems by employing a multilayer absorber solar collector.The SiO2–TiO2 hybrid nanofluids at volume concentrations up to 2.0%were tested at various flow rates(1.7 to 3.7 LPM)and solar radiation intensities(250 to 1000 W/m2).The thermal performance of the solar collector was assessed by measuring the temperature variation,heat loss,and overall efficiency of the collector.At the optimal volume concentration,the temperature difference for solar collectors employing SiO2–TiO2 hybrid nanofluids increased significantly.The optimal volume concentration of 1.5%yields a maximum temperature difference of 9.5°C.In addition,the efficiency and fluid temperature of the solar collector containing hybrid nanofluids have been enhanced by 22%and 37%,respectively.The SiO2–TiO2 hybrid nanofluids with the optimal volume concentration of 1.5%were therefore recommended for maximum efficiency in the solar collector.

Applying Double Skin Facade with ETFE Membrane Assembly for Energy Saving and Acoustic Protection for the Building of the Czech Institute of Informatics,Robotics and Cybernetics in Prague

Multidisciplinary, integrated planning approach by architects, engineers, scientists and manufacturers to reduce energy consumption of buildings. The CIIRC Complex, located on the main campus of Czech Technical University in Prague consists of two buildings, newly constructed building and adaptive reuse of existing building. CIIRC—Czech Institute of Informatics, Robotics and Cybernetics is a contemporary teaching facility of new generation and use for scientific research teams. New building has ten above-ground floors, on the bottom 4 floors of laboratories, scientist modules, classrooms, above are offices, meeting rooms, teaching and research modules for professors and students. Offices of the rector are on the last two floors of the building. On the top floor is congress type auditorium, in the basement is fully automatic car park. Double skin pneumatic cushions facade. In the project are introduced series of architectural and technical features and innovations. Probably the most visible is the double skin facade facing south-transparent double layer membrane ETFE (Ethylen-TetraFluorEthylen) cushions with triple glazed modular system assembly. Acting as solar collector, recuperating of hot air on the top floors, saving up to 30% of an energy consumption.

A portable,auxiliary photovoltaic power system for electric vehicles based on a foldable scissors mechanism

In recent years,countries worldwide have actively advocated electric vehicles for environmental protection.How-ever,restrictions on the driving range and charging have hampered the promotion of electric vehicles.This study proposes a portable,auxiliary photovoltaic power system based on a foldable scissors mechanism for electric vehicles.The system includes a photovoltaic power generation module and an electricity transfer module.The photovoltaic power generation module built based on a foldable scissors mechanism is five times smaller than in its unfolded state,improving its portability in its folded state.The electricity transfer module transfers electricity into the cabin via wireless power transfer units and stores electricity in supercapacitors.Solar simulation exper-iments were conducted to evaluate the system’s performance:maximum output power of 1.736 W is measured when the load is 5Ω,while maximum wireless power transfer efficiency is up to 57.7% with 10Ω load.An elec-tric vehicle in Chengdu city was simulated for a case study.The results show that the annual output of a single photovoltaic power system can drive the MINIEV for 423.625 km,indicating that the proposed system would be able to supply power for electric vehicles as an auxiliary power supply system.