Chimney Height Research Articles

Computational modelling and simulation of the feasibility of a novel dual purpose solar chimney for power generation and passive ventilation in buildings

This paper presents numerical study and analysis of a novel application of a proposed solar chimney system to help solve the problem of ventilation (thermal comfort) and energy management (inadequate power supply) of buildings in the tropics. The main objective of the study is to determine the feasibility of the proposed system vis-à-vis the airflow rate within the room for adequate ventilation and within the solar chimney for required velocity to power a small size wind turbine. The commercial Computational Fluid Dynamics package FLUENT (ANSYS WORKBENCH 14.5) was used for the simulation. The computational domain consist of a 2-D 4 × 4 m2 room and solar chimney with varying heights between 5 and 9 m and gap between 0.5 and 1 m. The solar radiation condition with solar heat flux (SHF) of between 200 and 1,000 W/m2 and ambient wind conditions of no wind and wind speed of 1.0 to 8.0 m/s were simulated. The validation of simulated results with experimental data from previous studies showed conformity with a deviation not more than 2.5%. Results showed that the room mass flow rate increased from 1.0 kg/s with no wind effect to about 30.1 kg/s with induced wind of 1.0 to 8.0 m/s. The air mass flow rate increased from about 0.57 to 0.91 kg/s at chimney height of 5 and 9 m respectively for no wind condition and SHF of 400 W/m2. The power outputs obtained from the SC with SHF of 400 W/m2 for chimney height of 5 and 9 m were 32.8 and 85.2 W/m2 respectively. The results presented helps layout and establish the fundamentals and system response to temperature and airflow of a solar chimney system used for the combined purpose of passive ventilation and power generation in a building.

Application of a Solar Chimney Power Plant to Electrical Generation in Covered Agricultural Fields

Greenhouses are an ideal plant production environment, providing high quality products in all seasons of the year and removed from climatic influences such as wind, frost and rain. However, this type of farming involves costly construction, and it is necessary to consider using it in other aspects, in addition to agriculture. The purpose of the current work is to study the possibility of using a solar chimney power plant (SCPP) in the generation of electric power, thereby meeting the need for energy in agriculture, including lighting, pumps, drip irrigation and other applications. This paper describes an analytical study of solar chimney power plant in a greenhouse environment. The investigation was based on experimental calculations to identify out power from varying the air flow intensity inside the farm, depending on its conditions. The modelling was carried out in an ANSYS environment and the simulation of solar plant used a FLUENT k-ε Module for solving and post-processing the problem. Results showed that a solar chimney power plant, in which the chimney height and diameter were 20 m and 0.3 m, respectively, and the dimensions of the green farm collector 70 m × 50 m, could produce a monthly average of 1.31~2.42 kW electric power throughout the year.

Regional Detection Polluted with Diffusion and Convection Models in Banten Province

Numerical convection and diffusion models can be used to predict air pollutant concentrations in an area. Changes in air pollutant concentration can be analyzed using diffusion equations which depend on the coefficient of intra-particle diffusivity (D). Whereas to find out the changes in air quality categories become polluted using a convection equation which depends on the diffusivity coefficient between particles (Γ). The combination of the two equations can be used to estimate the polluted areas of a region. The results of the climate analysis indicate that Banten Province if viewed from the direction of the wind, is very potential for the development of increased fish production. Meanwhile, if viewed from the temperature and rainfall of Banten Province the potential for agriculture. However, considering that in the western part of the region there is a large industry with a chimney height of 275 meters, so based on atmospheric stability, the distribution of air pollutants spread far outside the industrial area. This will have implications for other regions so that at high concentrations (with diffusion equations) it will change the air quality (with the convection equation) so that in certain regions and at certain times it will become a polluted area.

Küçük Bir Güneş Bacasının Sıcaklık Dağılımlarının İncelenmesi

Environmental friendly and sustainable energy policies are gaining importance day by day. A prototype solar chimney constructed in Elazig is investigated experimentally in terms of temperature distribution and solar chimney efficiency. Elazig is in the third degree day region where the temperature varies between -15 ° C and + 42 ° C. The experimental results showed that efficiency increased with an increase in the height of the solar chimney. The efficiency depends on the chimney height and the ambient temperature. The higher the height of the chimney, the more is the efficiency. However, the effect of ambient temperature on the efficiency seems to be very low. It was seen that, solar chimney system can be an alternative system for energy production under Elazig conditions. .

Stability analysis and parametric study of natural circulation integrated self-pressurized water reactor

The stability analysis of a natural circulation integrated self-pressurized water reactor is investigated by the Lyapunov approach. The analysis of the pressurized water reactors (PWRs), particularly the integrated self-pressurized water reactors, is essential in keeping the neutronic and thermal-hydraulic parameters of the system stable. An appropriate nonlinear dynamic model is introduced based on conservation of mass, momentum and energy which is then linearized, in a state-space model. The Lyapunov approach and Routh-Hurwitz criterion are applied to assess the stability of this linearized system over its entire power range. The analysis is done for the primary coolant circuit in the RPV by assuming the steam dome pressure as the fixed parameter. It is found that the system remains stable over its entire power range. The influence of different geometrical features is studied at nominal conditions. It has been found that by reducing the chimney height results in a decrease in the coolant flow rate and a downward motion of the onset of flashing while the average core coolant temperature rises. For lower values of friction losses coefficient, the coolant flow rate increases, and the onset of flashing moves upward and the average core coolant temperature decreases. A change in independent parameters, which are effective in generating the natural circulation of the coolant, can influence the inherent safety of the system: An increase in reactor power and chimney height and a decrease in friction losses coefficient improve the system inherent safety. Two input functions as extra reactivity for increasing and decreasing the power from the nominal state are implemented into the dynamic model and the model response is therefore assessed by considering the lack of two phase flow entry to the core restriction. The boundary of the system stability lies in the range 32–107 MWt and using the system outside this range the system pressure needs to be controlled through spray and heater systems. The obtained results are based on the initial information, data and primary design of these types of reactors. Determining a more accurate boundary requires more detailed design and assessment together with experimental test facilities with respect to other restricting parameters of the system. The results presented in this paper can be implemented in further research on this type of reactors, particularly for nonlinear stability analysis and finding nonlinear Lyapunov function.

Performance analysis of a wind supercharging solar chimney power plant combined with thermal plant for power and freshwater generation

In this article, a wind supercharging solar chimney power plant combined with seawater desalination and waste heat (WSCPPDW) and a solar chimney power plant combined with seawater desalination and waste heat (SCPPDW) were proposed. Both of them were equipped with a spiral exhaust gas heating channel (SGC), and the main difference between the two was the presence or absence of the wind supercharging device. Then the physical and mathematical models were constructed for evaluating the output characteristics under different conditions. It was found that the rise of chimney height and flue gas temperature were both beneficial to the overall performance of WSCPPDW and SCPPDW. The reduction of seawater thickness improved the entirety output characteristics under adequate irradiance conditions. As the solar irradiance and flue gas mass flow increased, the electricity generation was augmented, but the freshwater production and comprehensive efficiency represented a downward trend. Besides, the performance of WSCPPDW was always better than that of SCPPDW, and the energy comprehensive utilization efficiency of WSCPPDW was increased by 15.4% throughout the utilization of high-altitude wind. Concretely, the hourly freshwater yield, power generation and comprehensive efficiency of WSCPPDW reached 193.7 kW, 17.2 ton/h and 13.5% respectively.

Effect of the chimney design on the thermal characteristics in solar chimney power plant

Solar chimney power plant (SCPP) is an interesting project to produce clean and sustainable energy. An efficient SCPP system requires a very high chimney, and thus the optimization of the chimney shape presents an important way to enhance the SCPP performance. The aim of this paper is to analyze the effect of the divergent chimney shape on the airflow behavior inside SCPP. A comparison between four chimney shapes is carried out using CFD method: two cylindrical chimneys with different diameters and two divergent chimneys with different shapes. Indeed, both parameters were studied: the ratio of the inlet and outlet diameter of the chimney and the shape of the chimney which both hyperboloid and conical. The SCPP prototype was tested numerically and experimentally to validate the present computational outcomes. The obtained results confirm that the divergence shape affects directly the efficiency of the SCPP system. Moreover, the hyperboloid chimney presents the efficient solution which produces an important power output with keeping the chimney height constant.

The effect of the environmental parameters on the performance of asphalt solar collector

Abstract In this research, asphalt Solar Collector ASC was built outside the laboratory. Atmospheric air was used as a working fluid. The effect of the environmental conditions such as ambient temperature, wind speed, variation of solar day time, and ASC chimney height are considered. The construction of the ASC system consists of aluminum buried pipes under asphalt layers with the two ends open. In the present study for the construction of the used ASC and its thermal properties, experimental were carried to evaluate the effect of chimney height on the flow field. The results showed that the chimney height has a strong effect on the average air flow velocity through the ASC. Also, the ASC prototype performance for collecting the solar energy and transferring it to the flowing ambient air depends on the used chimney height, as well as the environmental/atmospheric conditions in terms of ambient air temperature, and wind speed.

Analisis Perubahan Waktu Pengeringan Terhadap Variasi Tinggi Cerobong

This study aims to find out the efficiency of grain dryers using a chimney and a fan as suction air from the collector into the drying chamber.The research was conducted at the Central of Laboratory Department of Mechanical Engineering Faculty of Engineering, University of Muslim Indonesia, Makassar. A dryer was made from a zinc plate of 0.2 mm as collector by using a hot-air and solar energy as a drying medium. It was expected that this tool can dry grain quickly with evenly distributed drying level or water content. There were five variations of the Chimney : 20 cm, 50 cm, 80 cm, 110 cm and 140 cm with the grain thickness of 7 cm, 5 cm and 3 cm. The data were then analyzed to obtained the efficiency of the dryer. The results reveal that the time required to lower the water content of the harvest grain from 24.6% to 13.6% - 13.85% of milled moisture was 4 hours - 6.5 hours with an efficiency of 34,232 % for grain thicknes 7 cm, 31,480 % for grain thicknes 5 cm and 30,122 for grain thicknes 3 cm at 80 cm chimney height.

Thermal and economic assessment of a solar chimney cooled semi-transparent photovoltaic (STPV) power plant in different climates

A new cooling approach for a semi-transparent photovoltaic system using a solar chimney (STPV-SC) is proposed and economically evaluated. The STPV panels are utilized as the collector roof of a solar chimney for enhancing the panels cooling. For analyzing the system, a mathematical model based on the heat transfers between three main components of system: STPV, inside air and ground is developed and the results are validated by the experimental data reported in the literature. Furthermore, a comprehensive economic evaluation is carried out for the proposed system and payback period, as well as unit cost of produced power, are reported as the main economic parameters. The influence of main decision variables including packing factor, chimney height and collector radius is investigated on the power generation and economic performance. Moreover, the economic assessment of proposed system is carried out for five selected cities in Iran. Based on the results, packing factor always optimizes the economic performance, whereas the lowest payback period is obtained for packing factors between 0.3 and 0.5. Also, it is found that the highest and lowest economic enhancements by using the proposed system belong to Shiraz and Tabriz cities with about 11% and 5%, respectively.

Solar chimney power plants – Dimension matching for optimum performance

Solar chimney power plants are very large structures with the potential to generate significant amounts of electricity. Plant dimensions such as the collector diameter and chimney height and radius are important in determining system performance. The objective of this study is to identify the key parameters that drive performance. Performance was assessed in terms of power output and power output per cost. Using a detailed thermodynamic model, the plant power output was predicted for a wide range of design and operational parameters. It was found that the optimum pressure drop ratio depends on the collector and chimney radius, but not on chimney height, ambient temperature or insolation. The dimensions of the main components must be well matched to achieve best performance. Chimney radii of up to 200 m are essential to achieve maximum power generation up to 900 MW. Optimum power output exists for variation of the collector and chimney radius. However, increasing the chimney height always results in increased power generation. The physical phenomena underpinning high-performing configurations were highlighted. Power and efficiency increase with increased plant dimensions, but technological limits exist for the chimney height. A simple but robust cost model was introduced to identify optimum configurations in terms of power output per cost. Different relative costs between collector and chimney the optimum dimensions were selected. It was concluded that several smaller plants with collector radius about 3000 m are advantageous over one larger plant. Taller chimneys are economically beneficial until the specific chimney costs increase more than quadratically with height.

Numerical and Experimental Study of the Aerothermal Characteristics in Solar Chimney Power Plant with Hyperbolic Chimney Shape

Solar chimney power plant (SCPP) is an attractive way to produce electricity in the high solar radiations zones. It consists of three main components: collector, chimney and turbine. The chimney is considered as the most expensive part of the SCPP. This is due to the requirement of important height to achieve suitable performance. In this paper, a new chimney design of hyperbolic shape is proposed. The design is optimized by analyzing the impact of the divergence radius of the chimney on the SCPP performance using a 2D computational fluid dynamics code. For this end, the ratio of the hyperbolic chimney radius over the chimney height was varied from 0 to 0.3. Computational results were validated against test data from a developed experimental prototype. The comparison of the proposed designs with a conventional solar chimney power plant shows a significant performance improvement. In fact, the increase in the divergence chimney radius has led to more advanced power output. Specially, a rise of 295% of the total system efficiency is found when the divergence radius is set to 15 m.

Computational study on the effect of collector cover inclination angle, absorber plate diameter and chimney height on flow and performance parameters of solar updraft tower (SUT) plant

A computational model is developed to investigate the influence of geometrical configurations such as chimney height (Hch), absorber plate diameter (Dap) and collector plate angle (θcr) on flow and performance characteristics of solar updraft tower (SUT) plant. The diameter of the chimney (Dch) and air entrance gap (e) selected for numerical simulations are 0.6 m and 0.1 m, respectively. Parametric study is carried out by varying Hch of 3–8 m, θcr of 20°-35° with an increment of 5° and Dap of 3.5–12 m. A turbulent model (RNG k-ɛ) is incorporated for considering turbulence effect and Discrete ordinates (DO) model incorporated for estimation of radiation heat transfer inside the setup. It is found that a slight decrease of temperature and increase of air velocity when θcr is increased. It is noticed that air velocity is enhanced (up to 44%) while the Hch is increased from 3 to 8 m. Power output, overall, chimney and exergy efficiencies are estimated. Correlations are developed to estimate the performance parameters in terms of geometrical configurations. From the parametric study, it is concluded that for the Dch and e of 0.6 m and 0.1 m, respectively, better performance can be achieved at a Hch of 7 m, θcr of 30° and Dap of 5 m.

Solar chimney optimization for enhancing thermal comfort in Egypt: An experimental and numerical study

Air motion can be induced in naturally ventilated buildings using passive solar chimneys. This work aimed to optimize solar chimney design to maximize indoor air velocity induced by natural convection, with a particular emphasis on thermal comfort. A three-dimensional, quasi-steady computational fluid dynamics (CFD) model was established for the prediction of buoyant air flow using the renormalization group (RNG) k-ε turbulence model. In order to validate the CFD model, experiments involving an inclined solar chimney attached to a single room were performed. The experimental results agree reasonably well with the CFD calculations, with a 5.14% deviation between the values. Moreover, a Multi-Objective Genetic Algorithm (MOGA) coupled with Design of Experiments (DOEs) and the Response Surface Method (RSM) was employed to derive the optimal solar chimney design for the enhancement of indoor air motion. The optimization results reveal that the maximum indoor air speed in the living zone is achieved using a solar chimney of 1.85 m height, 2.65 m width, 75° inclination angle, and 0.28 m air gap. Sensitivity analyses indicate that solar chimney width is the most influential parameter, followed by inclination angle and then air gap, while the solar chimney height has a negligible effect. The proposed solar chimney is able t o passively induce air motion of up to 0.28, 0.47, and 0.52 m/s at mean solar radiation values of 500, 700, and 850 W/m2, respectively. These elevated air velocities are capable of enhancing thermal comfort upper limits by removing sensible and latent heat from the body.

Analysis of the Geometric Constraints Employed in Constructal Design for Oscillating Water Column Devices Submitted to the Wave Spectrum through a Numerical Approach

This paper aims a numerical investigation about the fluid dynamic behavior of an oscillating water column (OWC) wave energy converter (WEC) into electrical energy. Constructal design is employed to perform a geometric evaluation of an OWC WEC submitted a Pierson-Moskowitz wave spectrum. The objective function is to maximize the energy conversion. The hydropneumatic chamber volume (VHC) and the total OWC volume (VT) are adopted as geometric constraints. In the first stage, the values are constant during the maximization process. However, in a second stage they are changed according to the constraint variation (CV). One of the goals is to analyze the influence of the choice of this geometric constraints value on the OWC performance in relation to the wave spectrum. For this purpose, are considered three different scenarios: 1) VHyd is equal to the minimum incident wavelength (λmin), that is relative to the maximum frequency of the wave spectrum times the significant wave height (HS); 2) VHyd is equal to the peak incident wavelength (λpeak), that is relative to peak frequency of the wave spectrum times the significant wave height (HS); and 3)VHyd is equal to the maximum incident wavelength (λmax), that is relative to minimum frequency of the wave spectrum times the significant wave height (HS). To do so, constructal design is employed varying the degree of freedom (DOF) H1/L (ratio between the height and length of OWC chamber), while the others DOF’s H2/l (ratio between height and length of chimney) and H3 (lip submergence), are kept fixed. It is employed a Pierson-Moskowitz wave spectrum with significant period (TS) equal to 7.5 s and significant wave height (HS) equal to 1.5 m. For the numerical solution it is used the computational fluid dynamic (CFD) code, based on the finite volume method (FVM). The multiphase volume of fluid (VOF) model is applied to tackle with the water-air interaction. The computational domain is represented by the OWC WEC coupled with the wave tank. The results showed that when CV = 2.25 for λmax and (H1/L)O = 0.2152 the highest average for power was obtained, nearly 18,000 W. While for λmin and (H1/L)O = 0.2193 it was smaller than 1,000 W. Besides, it was obtained a theoretical recommendation about the geometric constraints employed for the constructal design application, aiming the maximization of the OWC energy conversion from the incident wave spectrum.

Modeling solar chimney for geometry optimization

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.

A complete design data and performance parameter evaluation of a pilot scale solar updraft tower

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 production from solar energy. It consists of three main components; a solar air collector with absorber plate, central chimney, and a turbine. The objective of this work is to present complete design parameters of individual components of a small and less expensive prototype solar updraft tower. The main contents of this study are; solar radiation calculations, chimney design, solar wind turbine design calculations, heat loss and pressure loss estimations for collector. The pilot solar chimney power plant considered in this work consists of an air collector diameter of 3.5-m, the chimney diameter and height are 0.6 and 6 m, respectively. Theoretically the maximum velocity of air is achieved at chimney base is 1.9 m/s. The overall efficiency of the plant is estimated as 0.0019%.

Performance Assessment of Solar Chimneys: Part I – Impact of Chimney Height on Power Output

Solar chimney is a truly sustainable and green energy technology, which is a potential alternative to carbon-based energy economy. The working principle of solar chimneys is based on the buoyant nature of air to turn a turbine that produces electrical power. Solar chimneys are highly in the centre of interest among all solar energy applications since they enable both day and night time operation owing to greenhouse and chimney effects. A typical solar chimney consists of three main parts as chimney, collector and turbine. When the in-situ applications of solar chimneys are gone through, it can be easily asserted that the driving force in electricity generation comes from the chimney effect as a consequence of the notable pressure differences between the inlet and outlet of the chimneys. In most cases, the greenhouse effects on power output are considered auxiliary only due to non-optimised geometric properties for the air medium beneath the collector. Within the scope of this CFD research, the impacts of chimney height on power output of a typical solar chimney are evaluated. A commercial and reliable CFD software ANSYS FLUENT is considered for the numerical analyses. For different chimney heights, the average velocity at the inlet of chimney in which the turbine is placed is determined by applying k-e turbulence model, continuity, momentum and energy equations for a 2D model. The results reveal that there is an exponential relationship between the pressure difference and the average air velocity and the solar chimney is found to be practical after a certain value of chimney height. For a chimney and collector diameter of 10 and 1000 m, respectively, the average velocity at the inlet of chimney is calculated to be 25.17 m/s for a chimney height of 100 m, whereas it is 18.06 m/s for the height of 50 m. The findings are of vital importance in terms of feasibility studies on solar chimneys since they give a clear understanding about the influence of chimney height on the electrical power output of any solar chimney power plant.

Performance Assessment of Solar Chimneys: Part 2 – Impacts of Slenderness Value and Collector Slope on Power Output

In the previous part, impacts of chimney height thus pressure difference on the power output of solar chimneys have been numerically evaluated. Within the scope of this research, slenderness and slope of collector are analysed in terms of their potential influence on average velocity of air at the chimney inlet. The analyses are based on a commercial and reliable CFD software ANSYS FLUENT. Chimney height is considered to be 100 m in the research and the chimney diameter is varied through a dimensionless parameter (β). Basically, β is defined as inverse slenderness and its value of 0.1 corresponds to a chimney diameter of 10 m as expected. Average velocity of air at the chimney inlet is numerically assessed for the β values in the range of 0.1-0.5. Collector slope is also investigated in the analyses through a dimensionless parameter (δ). The term δ is defined as the ratio of inlet height of collector to the collector height at the centre. Similarly, average velocity of air at the chimney inlet is determined for the δ values in the range of 0.2-1.0. The analyses are conducted for a constant solar intensity of 200 W/m2. The chimney height at the centre is taken to be 4 m in the slenderness analyses and 10 m in the collector slope assessments. The height of collector inlet is constant and 1 m in the slenderness research. On the other hand, it is varied from 2 to 10 m in the collector slope analyses. The results reveal that the velocity figures exponentially decrease from 15.93 to 11.85 m/s when the β value rises from 0.1 to 0.5. On the contrary, velocity figures increase with increasing δ value, the enhancement is determined to be about 23%.

Numerical Estimation of Heat Recovery within a Distributed Incinerator Using Water and Hydrocarbons as Working Fluids

The potential of a cogeneration system combined with a small combustion furnace was investigated in this study. The heat transfer between the exhaust gas and working fluid flowing in a spiral tube heat exchanger was estimated numerically and the amount of vapor generated was predicted. The combustion chamber had a 0.49 m3 inside volume with a chimney height of 2.5 m and an inner diameter of 0.28 m. A uniform gas side temperature condition that was referenced from the results of a preliminary experiment and a computational fluid dynamics simulation were adopted to simplify calculations and clarify the effects of working fluids. The amounts of heat recovery when utilizing water and other types of working fluids (Pentane, Butane) were compared. The most effective tube length considering pressure drop and phase change was also predicted. Isentropic theoretical thermal efficiency and T-s diagrams are analyzed to evaluate the vapor-power conversion rate using waste heat. As a result, a potential the heat recovery rate of approximately 100 kW at a 150 kg/h mass flow rate is expected.