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Solar updraft tower (SUT) plant is one of the potential technologies for carbon-free power generation. However, a conventional SUT plant is not economical due to its lower thermal performance. The present work provides an in-depth numerical investigation and thereby enhancing the thermal performance of the SUT plant. The real SUT plant (Manzanares, Spain) dimensions were considered for this three-dimensional analysis. Two models of the SUT plant were developed; Case 1 having no fillet, Case 2 having a 45° square fillet. Comparative analysis was done between Case 1 and Case 2 on various performance characteristics such as turbine power (Pthe), collector and overall efficiencies (ηcoll, ηo). Higher updraft velocity (about 38.5% rise) was observed due to the provision of fillet in case 2. Also, case 2 produced a Pthe of 141 kW, ηcoll of 62% and ηo of 0.25% which are with an enhancement of 73.3%, 48.44% and 72.4%, respectively. These abrupt variations in performance parameters proved that the fillet makes much impact on the SUT system and therefore it must be built on the base of the chimney. The results were compared with the existing experimental data and found promising agreement.

A renewable energy resource like solar energy that is abundant in nature and eco-friendly, is a better alternative for electricity generation. Solar energy is already being used to produce electricity with the help of photo-voltaic panels and among many other technologies solar updraft power plant is a noble promising technology which can be used to supply power to countries with large wastelands or unused desert lands. In this study, the temperature and velocity values that affect the performance of solar tower are analyzed for different chimney height and collector surface areas. The simulation of the Solar Updraft Tower was performed with Energy2D software based on computational physics. It was analyzed that the increase in tower height and collector surface area significantly increased the temperature and velocity values of the air flowing from the collector mouth inlet to the center. As a result, when different solar updraft tower models were compared, the most important factor affecting the performance of the solar chimney was the chimney length and the collector surface area.

Solar vortex engine (SVE) is one of the novel alternative energy concepts which uses solar energy for creating artificial vortices. The working principle of SVE is the same as the solar updraft tow...

Solar chimney power plants play an important role in the field of renewable energies. The present study undertaken is related to design a solar updraft tower with all the variable geometric parameter in consideration and to optimize the performance for solar chimney power plant by means of experimental data as well as computer simulation with the formulation an approximate mathematical model. The components of the solar chimney power plant include the collector sheets, chimney and turbo generator. Solar radiation is transferred to the collector plates, air under the solar collector is heated up which is sucked vertical chimney located at the centre of the vertical cylindrical shell. The updraft is formed which drives the turbine and generator to produce the electricity with low cost as compared to other methods.

Wind energy characteristics include lack of “stability and predictability”. Solar updraft tower, also known as solar chimney SC, is a device in which wind is locally generated by the thermal effects of a solar collector which covers an area surrounding the chimney. In this work computational fluid dynamics, is applied to model the heat and transport relations in the collector and chimney area. The geometry, mesh layout and the existing analytical models are verified for consistency against the experimental data of Manzanares plant in Spain. As one of the geometrical parameters such as collector diameter is changed, an optimization process occurs, leading to a decision on the best matching size for the other dimensions. The process checks the output against the optimized profiles of temperature, velocity and pressure. Based on studying 180 cases in 15 groups for collector size against chimney height and diameter and another 130 cases in 12 groups for collector height, a table and graphs of matching dimensions are obtained. As a consequence of this work, it is possible now to make a more accurate decision on consistent dimensions for a solar chimney plant.

Solar updraft tower (SUT) is a simple power plant in which ventilation of heated air inside a channel drives a turbine. This system is recognised as suitable for areas with abundant solar radiation. As a result, there is no extensive research on the performance of SUTs under mild solar radiation. Studies show that strong ambient crosswinds can affect the performance of a SUT. In this paper, the efficiency of SUTs in areas which benefit from strong winds, despite low solar radiation, is investigated through numerical modelling. Comparison is made between the efficiency of a commercial-scale SUT in Manzanares (Spain) with intensive solar radiation, and one of the same size potentially located in the windy and mild climate of Orkney Islands in Scotland. The results show that ambient crosswinds can increase internal air speed and efficiency of a SUT by more than 15% and 50%, respectively. Consequently, such a SUT in Orkney can offer more than 70% of the efficiency of the one in Manzanares. The results show that, for a given power capacity, a wind turbine enclosed in a SUT can be considered as an alternative to a number of conventional wind turbines installed at height in the open air.

Renewable energy sources are the best alternative for giving solution to the energy shortage and CO2 emission problems. Solar updraft tower is a relative novel technology for electricity pr...

Solar power is one of the most raising and encouraging renewable source of energy generation. Solar plants are playing an important role in power supplies worldwide. Nowadays, the electrical energy demand is increasing rapidly due to fast-growing daily requirements. In the last few decades, scientific researchers have focused on a novel technology called the solar chimney power plant, sometimes recognized as solar updraft tower. The solar chimney is principally composed of three main constituents, namely, a solar collector, a chimney and a wind turbine. This promising technology addresses a very challenging idea of generating electricity from free solar energy. It is categorized as a viable resource of clean energy for many non developed countries. The world’s first solar chimney prototype was designed and constructed at Manzanares in Spain, as a result of a joint project between the Schlaich Bergermann partner and the Spanish government. The plant is characterized by a tower high 195 m with a radius of 5 m. The radius and height of the collector encircling the tower are respectively 120 m and 1.85 m. The spanish prototype built by the engineer Jorg Schlaich of Schlaich Bergermann operated without significant problems for seven years. Several research projects have been conducted all over the world to design and introduce different solar towers based on experience gained from operating the 50 kW Spanish prototype. To ensure that the energy conversion is maintained at satisfactory levels to guarantee considerable power generation, an unprecedentedly high tower and an immense collector area are needed. This plant is then based on a thermal updraft movement of hot air resulting from natural convection. In this chapter, the simulations were conducted using cylindrical coordinate system. The inner fluid flow is considered turbulent and simulated with the k-e turbulent model, by means of the CFD commercial software ANSYS Fluent. Numerical data were validated by comparing them with those from experiments. The agreement between simulation results and the measurements taken from the experimental plant in Manzanares is fairly good. A set of mathematical models of the solar updraft power plant have been developed where a model considering the kinetic energy difference within the solar collector was proposed. The operation of such a plant is strongly dependent on the amount of solar radiation. The main disadvantage of this system is the inability to operate constantly at night. A geothermal heating device is suggested to guarantee a continuous operation during night hours. In this chapter, an auxiliary heating system constructed of in-plane spiral coil tubes is proposed to be placed above the ground under the collector. Thus, the computational model is afterward combined with a mathematical model for a geothermal heat exchanger to evaluate the effect of combining both solar and geothermal energy on the plant performance. A parametric study of the hybrid plant is carried out. The study focus essentially on the impact of the collector size, the meteorological conditions as well as the effectiveness of the heat exchanger on the air flow rate, the temperature increase within the collector and the global performance of the solar-geothermal hybrid system.

Solar updraft tower (SUT) power plant is a unique system using solar energy, which consists of three main parts: the chimney, turbine, and collector. In tropical climate conditions, especially in Malaysia, the application of solar chimney can be deemed more competitive compared to other renewable energy systems. In this study, one prototype with a dimension of 3.5 m in diameter for the collector and 5 m height for the chimney, was built in Melaka, Malaysia. Vital parameters such as temperature field, pressure, humidity, and air movement were measured using data logger and stored using non-volatile memory. The most exciting finding was that the temperature and pressure difference was significantly seen during the experiment along the day. There was a significant surge for the humidity in the morning with an average of above 95% and the ambient temperature was approximately 35 °C due to low solar radiation. The humidity kept decreasing after sunrise due to the greenhouse effect produced in the solar collector. With the collection of these critical parameters, a solar chimney power plant was adequate to function and generate power from solar radiation in a country such as Malaysia, which is based in the equatorial region. These studies are limited as the analysis focused mainly for high radiation and did not investigate efficiency during low solar radiation. The addition of heat storage underneath the collector with current techniques is another direction of research for continuous system operation, particularly during low solar radiation. It is proposed that the synthesis of these factors should be extensively explored in future studies coupled with the application of heat storage.

To facilitate sustainable energy development, one has to understand the limited availability of nonrenewable energy resources, and the ability of the earth to renew or recover. Emergy is an instrument that measures environmental loading, ecological economics, and regional sustainable development. In this study, emergy indicators are calculated to investigate the sustainability of solar updraft tower (SUT). SUT produces energy from the hot air, utilizing a combination of a solar collector, central tower, and air turbines. The results demonstrate that the sustainability of SUT grew as the size of the plant increased. Further, emergetic ternary diagrams are drawn to facilitate the comparison between SUT and various technologies. The resources-use efficiency of wind energy and SUT, 200 MW is found to be the lowest among all energy technologies presented in this research. Scenario analysis is performed to explore the future optimization directions. The results demonstrate that the development direction of SUT systems should mainly focus on reducing the materials demanded by the manufacturing and construction of its solar collectors. This study aims to demonstrate the value of emergy as a powerful instrument for drawing long-term sustainable strategies in energy markets for a greener tomorrow.

A solar updraft tower is one of the wind power generation plants which utilizes solar energy. The purpose of this study was to ascertain whether the tower was also able to utilize crosswind energy. Wind tunnel experiments and numerical simulations were conducted simulating the crosswind. The results showed that suctioned updraft speed in the tower was proportional to the crosswind speed, and its conversion rate depended on the tower configuration. A diffuser-shaped tower with a vortex generator achieved to produce the updraft whose speed exceeded the crosswind speed. It was due to the low pressure created by the vortex atop the tower and to the diffuser effect. The crosswind utilization enables the simple power generation device to generate electricity during the night, and the hybrid utilization of renewable energies contributes to the increasing wind energy market.

The functioning of a turbine for solar updraft tower (SUT) power plant mainly relies upon the wind properties of the site and the streamlined structure of the blades. The power and torque generated by the rotor are determined by the rotor blade geometry. In this turbine blade design, few elements are different from a large wind turbine. For example, lower Reynolds number streams happen in the small wind turbines than the substantial ones, along these lines larger scale wind turbine airfoil blades may perform ineffectively in little applications. The small turbines are self-begun at lower wind velocities, in this way the hub (center part of a turbine) and tip parts are essential for the beginning up torque which ought to have the capacity to vanquish the resistance of the generator and the mechanical system. This paper shows the design of turbine blade for a prototype of SUT plant using direct method of approach (BEM theory). The solidity ratio, optimal chord length power, lift force and drag force, tip speed ratio, relative wind angle and blade pitch angle for different air velocities are evaluated and presented. At higher wind speeds, the performance of turbine was enhanced and vice versa.

The need for widespread use of renewable energy has created intense interest in developing various renewable energy technologies that can be used in different applications. Solar chimney is a system that can be used for cooling or heating the buildings, and power production. Moreover, in recent years solar chimneys were widely used for air cleaning, urban planning and sea water desalination. One of the reasons behind these various purposes is the simple working principle of solar chimneys. Due to its simplicity, it can play a key role in transitioning to 100% renewable energy. However, solar chimneys have weaknesses, and many of these issues need new approaches and innovative solutions. It is not a mature technology yet, either for power production or building energy efficient projects. Standardization, integration, hybridization, and finally developing the key components are the main subjects of solar chimney research and development. However, this unique system has great potential for harnessing solar energy in the near future in various applications.

Today, solar radiation is known as an important renewable energy which can be exploited in several ways such as solar updraft tower power plants, photovoltaic power plants, etc. In a solar updraft tower power plant, sunshine heats the air beneath a wide collector surrounding a tall tower and causes a hot air updraft in the tower by the chimney effect. This airflow drives wind turbines, placed almost in the chimney base, to produce electricity. In this study, the effect of the geometric form of the chimney on the performance of one solar updraft tower power plant is numerically investigated. Regarding the importance of the kinetic power of the hot air on power generation, it is intended to increase the air velocity by varying the forms of the chimney without changing the main dimensions of solar updraft tower power plant such as tower height and collector geometries. This approach may decrease the financial costs of the solar updraft tower power plant. For the numerical simulations, a finite volume computational fluid dynamics code solves the governing equations on an axisymmetric pi-shape domain (15° of whole geometry). To validate the results, the Manzanares solar updraft tower power plant experimental data are utilized. In this study, 15 forms of chimney based on a logical three-step procedure (from a basic cylindrical to a parabolic form) are examined. So, an appropriate/final form with a parabolic curve of chimney wall with divergence angle is obtained. Results indicate that the final form has the highest updraft air velocity. In fact, the average updraft air velocity increases from 15.66 m/s for the basic form to the value of 23.36 m/s (around 49.17% increments) for the final form.

Solar updraft tower (SUT) is a viable option to produce electrical energy from solar energy. Extensive studies needed to estimate the flow parameters and analyse this set-up. A 3D numerical model is developed to analyse the flow parameters such as pressure, temperature and velocity of SUT plant. Effect of geometrical parameters such as chimney height and collector roof angle is studied numerically in this work. The diameter of absorber plate and chimney as 3.5 m and 0.6 m and the collector roof angle, chimney height and inlet gap as 30o, 6 m and 0.1 m, respectively, are selected for numerical simulation. A parametric study is performed for varying chimney heights from 3 to 8 m and collector roof angle 20o–35o with an increment of 5o each case. The airflow inside the SUT is turbulent, renormalization group (RNG) k-e model is selected, and (discrete ordinates) DO model is incorporated for evaluation of radiation effect inside the domain. From the simulation results, it is concluded that when collector roof angle is increased, air velocity is increased and also air temperature is slightly dropped. It is found that there is 31% velocity enhancement when the chimney height is increased from 3 to 8 m.

A 3D numerical model is developed to estimate and analyze the flow and performance parameters of solar updraft tower (SUT) plant. The effects of geometrical parameters, such as chimney height and collector roof angle are studied. A turbulent, renormalization group (RNG) k-e model and discrete ordinates (DO) model is used to solve the governing equations. It is concluded that with an increase in collector roof angle, air velocity increases but air temperature decreases. There is 31% velocity enhancement when the chimney height is increased from 3 to 8 m. The overall, chimney and collector efficiencies and power output are estimated to be 0.00354%, 0.0465%, 81.4% and 0.255 W, respectively.

An experimental analysis of the solar updraft tower (SUT) with convergent chimney was undertaken by using different absorbers. Four different types of absorber materials were used in the experiment to store the solar intensity and exchanging it to the air being heated. The SUT comprised the three basic parts named as the solar collector, the tower or chimney and the turbine. An analysis for the solar updraft tower has been carried out, which describes the performance of solar updraft tower based on energy and exergy analysis. The maximum temperature distinction between ambient air and collector outflow was obtained in the case of SUT with small stone pieces (16.4 °C). The maximum average collector efficiency, collector exergy efficiency and overall efficiency of the SUT were acquired with the small stone pieces. The benefit of SUT system is that it would be favorable in the region with magnificent sunbeams to satisfy the demand of electricity.

A novel hybrid solar updraft tower prototype, which consists of photovoltaic panels and transpired solar collector, is studied, its function principle is described and its experimental performance is presented for the first time. A test unit of transpired solar collector updraft tower was installed at the campus of Trakya University Engineering Faculty in Edirne-Turkey in 2015. PV modules cover 42% of transpired solar collector area. PV and turbine power output, solar radiation, ambient temperature, temperature rise, collector cavity temperatures, and chimney velocities were monitored during 18 months. The results showed that hybrid solar updraft tower efficiency increased by about 2% in average compared to stand-alone PV system. The temperature rise in hybrid solar updraft tower is found to be 12–14 °C on the typical sunny day. Energy was produced continuously for 24 h. The results showed that solar utilization ranges from 60% to 80% during daytime.

In this study, a solar updraft tower (SUT) plant was developed with a thermal energy storage system . It has the chimney height, diameter, inlet gap and absorber plate diameter of 6 m, 0.6 m, 0.1 m and 3.5 m, respectively. A novel canopy-shaped (inclined) collector cover with an inclination of 30° and an in-built TES system that is structurally different from existing studies are the innovation of the study. Experiments were carried out and the data is presented in this work. The study focuses on the time-temperature relationship of ambient air, absorber plate and storage system. Hourly solar flux variation, air velocity, power potential and efficiencies of the system were also investigated. The average temperatures of the collector cover and storage were estimated and these were 45.93 and 42.67 °C, respectively. A maximum air velocity of 2.66 m/s was observed at the chimney base at a maximum solar flux of 938 W/m 2. A temperature difference of 25.47 °C was noticed between the absorber plate and air. The maximum theoretical and actual power outputs were 3.45 and 2.3 W, respectively. The overall, chimney and collector efficiencies of the system were estimated and these were 0.02682%, 0.0186% and 44.1%, respectively. Uncertainty analysis was also carried out to verify the reliability of the measured and estimated data. The power potential per collector area for the present SUT plant was 0.239 W/m2 which is 305–505% higher than the similar scale SUT plants.

Solar updraft tower power plant is a way to harness energy from the sun. It is a simple concept which requires low maintenance and utilises land that is already being used for growing plants, and generates power from it. A prototype plant was setup in Manzanares, Spain. Numerical analysis on power generation is performed for a similar plant assuming it is setup in Ropar. By considering losses via convection and radiation through the top surface of the collector, collector efficiency is calculated. Two cases arise here, 1. With 100% collector efficiency and 2. Collector efficiency is obtained after subtracting convection and radiation losses. The influx of solar radiation is highest in June. Hence, the variation of parameters like temperature, velocity, power output, efficiency with time of the day is done by taking averages for the month of June. Next the impact of physical parameters like chimney height, chimney radius and collector radius are studied on 21st June 11:00 to 12:00. How each parameter impacts the output of the plant is studied by creating a mathematical model of the power plant. Methods to improve the power output are discussed.

The solar updraft tower (SUT) is a renewable power generation system that uses natural air convection from the ground that is heated by solar radiation. Placing flow-guide structures within the collector of the SUT can enhance aerodynamic performance, and hence, increase the kinetic power. Here, we propose a central guide post (CGP) structure in the SUT that controls updraft flow. The effect of the CGP geometry on aerodynamic performance was investigated using computational fluid dynamics modeling (ANSYS Fluent 19.2) to show that a CGP can play a positive role by preventing stagnation of the airflow at the center of the collector, resulting in increased kinetic power output (up to ~2%). However, excessively long CGPs retarded airflow, resulting in a dramatic decrease in kinetic power output. We also investigated a system with both a CGP (to improve aerodynamic performance and minimize energy loss) and a heat-exchange baffle (to maximize thermal energy transfer). When installed with a proper distance between components, the CGP and baffle showed a combined effect of increasing the kinetic power output by up to 10%. We expect that our proposed method using the CGP and baffle system will contribute to the development of better future SUT technology.

Sustainable power sources will be wellsprings of perfect, endless and progressively focused vitality. They contrast from petroleum products basically in their decent variety, plenitude and potential for use anyplace on the planet, yet most importantly in that they produce neither one of the greenhouses gases – which cause environmental change – nor contaminating discharges. This paper express about the emerging technologies of renewable energy with their variants which helps us to learn new things by consumption of fewer powers in day to day life. Some of the renewable energy are -Marine Energy, Artificial photosynthesis, Algae fuels, Space-based solar power, Enhanced geothermal systems (EGS), Experimental solar power, Floating solar arrays, Solar-assisted heat pump, Solar aircraft, Solar updraft tower and so on.

In constructing a hybrid solar updraft tower with an underground heat exchanger, this study provides a theoretical and experimental investigation. A valuable function that lowers energy consumption in the case of domestic buildings is the Underground Tube Heat Exchanger. The submerged underground heat exchanger tube for heating in winter season and cooling in summer and the air is to be supplied by the influence of solar updraft tower to the building. The findings show that at 3 m depth from the earth, which is called buried depth at a 152 mm outer diameter, the maximum efficiency of the underground heat exchanger system. In comparison, with rising velocity of air, the temperature of the outlet air from the ground heat exchanger increases, varying from (22.2- 28 °C) and also increases with increasing pipe diameter and decreases with increasing tube length. The difference between the findings of the theoretical and the experimental tests was 1.8 %. The combined geothermal heat exchanger and solar updraft tower system is used as an air conditioning system and was satisfactory efficient for thermal building loads.

Solar updraft tower power generation has been demonstrated to be a promising approach for future applications of solar radiation to provide energy. In this paper, the history of the solar updraft tower power plant (SUTPP, also called solar chimney power plant) technology is reviewed, its characteristics are presented, and its principle is described. The experimental studies, main important factors of theoretical modelings, and cost studies, in the past few decades, are reviewed. The characteristics of novel non-conventional SUTPP technologies are discussed as well as environmental effect and power production conditions for the SUTPP technology.

Due to rapid urbanization, dense haze is formed in some Chinese cities where urban heat island (UHI) effect is aggravated. The urban haze problem has become a touchy issue significantly affecting humans living and working in the cities. Solar updraft tower (SUT) is a device that can drive warm air up to high altitude under the effect of natural buoyancy. In this paper, high SUTs are proposed to be used to drive the UHI warm air containing haze up to higher altitude and help the haze disperse to farther distance, thus lowering the concentration of haze effectively. This proposal can effectively alleviate the urban haze problem and simultaneously produce clean electric power in Chinese cities. The performance analyses and cost analyses of sole SUT for power generation in a UHI are conducted. The number of 1 and 1.5 km high SUTs only for impelling air up in UHIs of several main Chinese cities are estimated, respectively.

A 3D numerical model was made to analyse the effect of divergence angle of chimney (Φch), ambient temperature (Ta), solar flux (I) and turbine efficiency (ηtur) on wind flow and performance parameters of a solar updraft tower (SUT). A parametric study was carried out by varying Φch from 1 to 5° for different I (600–900 W/m2) and the results were compared with results for existing cylindrical chimney SUT (CC-SUT) plants. The range of Ta selected was 293–318 K and ηtur was 0.54–0.9%. Five different configurations of divergent chimney SUT (DC-SUT) plants were modelled. It was noticed that at Φch of 2°, the average velocity of air at chimney base was enhanced by 58.9% compared to CC-SUT plant. The average absorber plate temperature increased from 316.4 to 332.85 K with an increase in I from 600 to 900 W/m2 for Φch of 2°. The maximum overall efficiency, theoretical and actual power output of the DC-SUT plant were 0.0307%, 3.99 W and 2.67 W, respectively. The exergy of DC-SUT was 58% higher when Φch was increased from 1 to 2° at I = 900 W/m2. Correlations were generated to calculate performance parameters as functions of geometrical parameters.

This paper presents the idea of a centrifugal-force-aided convective heat engine where convective flow of a working fluid in a closed loop is used for the conversion of heat to mechanical energy. Centrifugal force is used for the conversion of a large pressure-head developed in a small volume of gas by heating into a large-volume bulk flow at much lower pressures. This flow is used to run a low-pressure turbine. Theoretical and numerical model calculations have been performed on an ideal system, without friction. The energy output per cycle and the efficiency of conversion have been calculated for different parameters. Considering linear heat flow at source and sink, efficiencies have been obtained that closely match the Curzon-Ahlborn efficiency, validating the model. Use of centrifugal force on the working fluid is seen to be a very effective way to increase efficiency and work done per cycle. The closed loop of the system allows suitable working fluid selection, thermal-linkage options and pressurisation, increasing efficiency and work done. This technique has the potential to reduce the complexity and cost substantially and simplify tolerance requirements. Coupled with a concentrating collector, this system can be used for sustainable conversion of energy through the CSP route.

The full-scale three-dimensional analysis of solar updraft tower power plant in Manzanares, Spain has been performed using commercially available CFD tool ANSYS Fluent. The two-equation k-\(\varepsilon \) turbulent model with standard wall function has been utilized for the fluid flow. The soil has been modeled with the consideration of the fact that temperature at 20 m depth remains constant throughout the year. The surface-to-surface radiation model is also included in the heat transfer model. The simulation has been performed for the steady state without/with radiation, the transient state with/without thermal storage on 8th of June. In the present simulation, water has been taken as thermal storage. It has been found that results improve considerably by including radiation effect, closely match with the results published from the plant. There is a reduction in the maximum velocity with the thermal storage; however, sufficient energy is available in thermal storage to overcome intermittency of insolation. The strong dependency of the plant on insolation can be reduced with the thermal storage.

The expressions containing no integral and considering the gravitational effect for predicting the pressure potential of a sloped-collector solar updraft tower power plant (SCSUTPP) under various conditions are developed based on a compressible fluid model. Based on the mathematical model of a sloped collector presented by Zhou et al. (2013) [8] and the expressions of the pressure potential developed, the performance of SCSUTPP is comprehensively studied under various conditions by assuming a steady compressible flow. The pressure potential for the vertical tower estimated using the relative humidity of the air based on the temperature at the tower inlet due to higher temperature is shown to be over-predictive, as compared to that based on the temperature at the collector inlet, when the effect of the collector height on the pressure potential has not been considered. The results for SCSUTPP using the pressure potential expression for dry air are basically shown to be in good agreement with those using the essential expression. The pressure potential and power output are shown to decrease with the increase in the same relative humidity of the air inside and outside the SCSUTPP. This variation trend is opposite to that obtained for dry air outside the SCSUTPP. The pressure potential and power output are found to gradually increase with the increase in the ambient pressure, the collector height, or the tower height, or the decrease of the ambient temperature. The increase in the temperature due to the latent heat released from the potential vapor condensation is large enough to stop the vapor to continue condensation. This work lays a good foundation for the predication of the potential power production from SCSUTPP.

The solar updraft tower (SUT) is a renewable power generation system that uses the natural convection phenomenon of the ground&rsquo, s air heated by solar radiation. The baffle is a thermo-fluid dynamic structure that improves the heat exchange efficiency and has been recently reported to be a useful tool to increase the output of the SUT. However, one of the less well-known issues is the relationship between the thermo-fluid dynamic characteristics of the flow in the collector of the SUT and the installation location of the baffle and how this affects the power output and SUT efficiency. In this study, the positive and negative thermo-fluid dynamic effects of the baffle, which vary depending on the installation location, are quantitatively analyzed, and the best location is predicted where the overall kinetic power generated by the SUT is maximized. The target SUT model consists of a chimney (12 m height and 0.25 m diameter) and a collector (1 m height and 10 m diameter), and a total of eight model cases are calculated. The results confirm that the kinetic power is lower or higher than that of the control model having no baffle, depending on the baffle installation location. When the position of the baffle is 4.5 m from the center, the increase in kinetic power is maximized by 8.43%. Two important conclusions are that the baffle should interfere minimally with the progress of the main flow into the chimney, generating kinetic power, and at the same time, the baffle should isolate the inner recirculating flow in order to accumulate the heat in the collector so that the natural convection strength is maximized. The perspective gained from the resulting data is useful for SUT design and for pursuing a higher efficiency in the future.

This paper evaluates the Solar Chimney Power Plant performance subject to adverse solar radiance conditions. For that, numerical simulations are performed to estimate the optimal ratio of the turbine pressure drop to the total pressure potential (x-factor) as an independent control variable. The results show that x-factor values remain around 0.8 for periods with sufficient heat gain from sun or ground. Otherwise, x-factor values have a tendency to drop to zero. In winter, due to lower system heat gains, this trend is more accentuated.

This study goes along the previous study of Bernardes and Zhou (2013) , namely “On the heat storage in Solar Updraft Tower collectors – Water Bags” analysing especially the sensible heat storage physical process in a Solar Updraft Tower collector taking into account the transient heat transfer in some typical soils through conduction, convection and solar radiation. For that, the mathematical model implemented in the earlier work was adapted to investigate the influence of thermal diffusivity and effusivity for some ground thermal properties. These simulations disclosed a complex ground thermal behaviour for different soil materials revealing that materials with lower thermal effusivity and diffusivity can decrease substantially output peaks for periods with greater heat gains.

A mathematical model describing fluid flow, heat transfer and pressure distribution inside a sloped-collector solar updraft tower power plant (SCSUTPP) is presented by assuming a steady compressible flow. Compared to conventional horizontal-collector solar updraft tower power plants (HCSUTPPs), the performance of SCSUTPP is comprehensively studied based on the mathematical model. The power outputs for SCSUTPP and HCSUTPP using the essential expression of driving force are respectively compared with those using the driving force expressions containing no integral, as proposed in literature. Results show that the expression containing no integral is accurate for HCSUCPP based on a compressible fluid model. The expression containing no integral is not accurate for predicting the driving force of SCSUTPP based on an incompressible fluid model when no variation of the atmospheric density with heights and no variation of difference of the atmospheric density and the density of the current inside the short SUT with heights are assumed. The gravitational effect has to be considered for predicting the SCSUTPP performance. The results show that the pressure potential and the power production of an SCSUCPP with a collector of 848 m height and a vertical SUT 123 m high lies between those for two HCSUCPPs respectively with vertical SUTs 547 m and 971 m high. This work lays a good foundation for accurate predication of potential power produced from SCSUTPP.

The goal of this study is to analyze particularly the sensible heat storage physical process in a Solar Updraft Tower collector taking into account the transient heat transfer in ground through conduction, convection and solar radiation and the use of water bags. Simulations were carried out varying the thickness of some water bags sets with and without insulation regarding thermal stratification effect. Results disclosed that thicker water bags can reduce more efficiently the daily temperature spam and thermal stratification is an import thermal effect. Water bags alone are however not enough to break efficiently heat peaks.

A model of correlating atmospheric cross flow and the fluid flow inside a solar updraft tower (SUT) was presented by assuming SUT inflow as a compressible flow. The influence of atmospheric cross flow on SUT inflow was studied using the model. Results showed that atmospheric cross flow had a large influence on SUT inflow, and the SUT inlet air velocity approximately equaled to 26% of cross flow velocity for collector air temperature rise Δ T = 0 °C. With an increase in atmospheric cross flow velocity, the fluid flow velocity inside SUT was found to increase. The enlargement effect of pressure potential and SUT inlet air velocity induced by atmospheric cross flow increased with higher SUT height, but decreased with higher temperature rise, which is proportional to collector area. The percentage enlargement for cross flow to the pressure potential was between 67% and 102% and that to the SUT inlet air velocity was between 33% and 48%, for H varying from 100 m to 3000 m and Δ T = 20 °C. The enlargement drastically decreased for Δ T varying from 0 °C to 80 °C for H = 900 m. The work would lay a good foundation for accurate predication of potential power production from SUT power plants by considering the effect of atmospheric cross flow.

The solar chimney power plant is a simple solar thermal power plant that is capable of converting solar energy into thermal energy in the solar collector. In the second stage, the generated thermal energy is converted into kinetic energy in the chimney and ultimately into electric energy using a combination of a wind turbine and a generator. The purpose of this study is to conduct a more detailed numerical analysis of a solar chimney power plant. A mathematical model based on the Navier–Stokes, continuity and energy equations was developed to describe the solar chimney power plant mechanism in detail. Two different numerical simulations were performed for the geometry of the prototype in Manzanares, Spain. First, the governing equations were solved numerically using an iterative technique. Then, the numerical simulation was performed using the CFD software FLUENT that can simulate a two-dimensional axisymmetric model of a solar chimney power plant with the standard k-epsilon turbulence model. Both the predictions were compared with the available experimental data to assess the validity of the model. The temperature, velocity and pressure distributions in the solar collector are illustrated for three different solar radiations. Reasonably good quantitative agreement was obtained between the experimental data of the Manzanares prototype and both the numerical results.

In this paper, we present the performance analysis of a solar chimney power plant expected to provide the remote villages located in Algerian southwestern region with electric power. Solar energy and the psychometric state of the air in the south of Algeria are important to encourage the full development of solar chimney power plant for the thermal and electrical production of energy for various uses. We are interested in Adrar where solar radiation is better than other areas of Algeria. The obtained results show that the solar chimney power plant can produce from 140 to 200 kW of electricity on a site like Adrar during the year, according to an estimate made on the monthly average of sunning. This production is sufficient for the needs of the isolated areas.

A solar chimney power plant consists of a translucent collector which heats the air near the ground and guides it into the base of a chimney at its centre. The buoyant air rises in the chimney and electricity is generated through one or more turbines in or near the base of the chimney. Various studies about solar chimney power plant performance have been published. Different calculation approaches with a variety of considerations have been applied to calculate chimney power plant performance. In particular, two comprehensive studies are relevant, namely those of (Bernardes, M.A.d. S., Vos, A., Weinrebe, G., 2003. Thermal and technical analyses of solar chimneys. Solar Energy 75, 511–524; Pretorius, J.P., Kroger, D.G., 2006b. Solar chimney power plant performance. Transactions of the ASME 128, 302–311). The paper compares the methods used to calculate the heat fluxes in the collector, and their effects on solar chimney performance. Reasons for the discrepancies between the predictions of the two models are given. In general the Pretorius model produces higher heat transfer coefficients and higher heat rate fluxes for both the roof and for the ground surfaces. The two approaches lead to very similar air temperature rises in the collector and thus, similar produced power.

A new model for a solar updraft tower is presented. It is based on a one-dimensional description of the fully transient gasdynamics in an updraft power plant from the outer end of the collector to the top of the tower. All the main physical effects are included. The model is derived from basic gasdynamic equations, a low Mach number asymptotics is performed and numerical simulations are shown.

Current in solar chimney power plant that drives turbine generators to generate electricity is driven by buoyancy resulting from higher temperature than the surroundings at different heights. In this paper, the maximum chimney height for convection avoiding negative buoyancy at the latter chimney and the optimal chimney height for maximum power output are presented and analyzed using a theoretical model validated with the measurements of the only one prototype in Manzanares. The results based on the Manzanares prototype show that as standard lapse rate of atmospheric temperature is used, the maximum power output of 102.2 kW is obtained for the optimal chimney height of 615 m, which is lower than the maximum chimney height with a power output of 92.3 kW. Sensitivity analyses are also performed to examine the influence of various lapse rates of atmospheric temperatures and collector radii on maximum height of chimney. The results show that maximum height gradually increases with the lapse rate increasing and go to infinity at a value of around 0.0098 K m � 1 , and that the maximum height for convection and optimal height for maximum power output increase with larger collector