Performance Evaluation of Solar Chimney Draft: Application to Ventilation

Ventilation is one of the factors contributing to energy consumption in buildings and food preservation. The solar chimney proves to be an alternative for reducing conventional energy consumption. Thus, in this study, the performance of a solar chimney with two active faces for thermally drawing air from a chamber for preserving agri-food products was evaluated. These performances were experimentally assessed through data measurements: temperatures and velocities within the chimney, and their analysis using Excel and MATLAB. The obtained results were compared with those from literature to verify their validity. From this study, it is found that the maximum temperature at the chimney outlet reaches 49.4˚C with an average value of 43.7˚C. Additionally, the heating evolution of the chimney air presents four (04) identical phases in pairs, reflecting the chimney’s operation throughout day. The temperature difference between the outlet and inlet of the chimney reaches a maximum of 17˚C with an average of 12.6˚C. Regarding airflow, the maximum air velocity at the chimney outlet is 0.8 m/s, and the average velocities have consistently been greater than or equal to 0.46 m/s. Thus, it can be concluded that the solar chimney is capable of providing ventilation for the preservation chamber through thermal draft.

Optimization of a Solar Chimney with a Horizontal Absorber for Building Ventilation:A Case Study

A study is conducted to optimize the geometry of a solar chimney equipped with a horizontal absorber in order to improve its performances in relation to the provision of ventilation.The problem is tackled through numerical solution of the governing equations for mass,momentum and energy in their complete three-dimensional and unsteady formulation.The numerical framework also includes a turbulence model(k-ε)and a radiant heat transfer(DO)model.Moreover,a Multi-Objective Genetic Algorithm(MOGA)is employed to derive the optimal configuration of the considered solar chimney.It is shown that an air velocity of 0.2 m/s can be obtained.This value is the minimum allowed air velocity according to the ASHRAE’s(American Society of Heating,Refrigerating and Air-Conditioning Engineers)adaptive comfort approach.

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.

Experimental and Numerical Investigation of the Solar Chimney Power Plant’s Turbine

The solar chimney power plant is a relatively new electricity generation concept, based on renewable energy, combining the greenhouse effect with the chimney suction. The solar chimney powerplant consists of three parts, the solar collector, the chimney and the turbine generator unit, of which the study was focused on the later part. To evaluate the turbine performance inside the solar chimney powerplant, experimental system was constructed in Aswan, Egypt that has a metrological site (23°58'N and 32°47'E) occurs. The system was constructed to evaluate the performance of the solar chimney turbine and power generation characteristic in the hottest site where Aswan is located at the nearest of the Tropic of Cancer at the summer season. Velocity, electric power generation and the turbine efficiency are studying in this work. The numerical analyses were performed by using a commercial code CFX, ANSYS 16.1 to simulate the flow through the turbine and overall system. The study shows that the range of power generated (1.2 W - 4.4 W). It can be estimated, according to the results, the variation trend in pressure drops with the turbine rotation speed increase with small differences when the turbine rotation speed surpasses 1800 rpm with average efficiency of 57%. It is concluded that the theoretical model is basically valid for the system under study, and the CFD simulation can be used conveniently to predict the performance of the system, the comparison between them and experimental result shows a good agreement.

Effect of chimney shadow on the performance of wind supercharged solar chimney power plants:A numerical case study for the Spanish prototype

Three-dimensional numerical simulations for a solar chimney power plant(SCPP)and wind supercharged solar chimney power plant(WSSCPP)based on the Spanish prototype using the solar ray-tracing algorithm were performed to study the shadow effect of the chimney.The area of the shadow region increases with an increase in the incident angle of the solar rays.A parametric study was performed by varying the incident angle from 0°to 30°.The temperature and velocity distributions at different incident angles were analyzed.In addition,we investigated the chimney shadow effect in several comprehensive SCPP systems.The findings show that the turbine shaft powers of the SCPP and WSSCPP were reduced by 22.4%and 13.7%,respectively,when the incident angle increased from 0°to 30°.In conclusion,it is important to consider the chimney shadow effect when estimating the performance in the design and cost analysis of SCPP systems.

Book review:Solar chimney power generating technolog

Ting-zhen MING,2016.Solar Chimney Power Plant Generating Technology.Academic Press of Elsevier.ISBN 978-0-12-805370-6Ting-zhen MING,2016.Solar Chimney Power Generating Technology.Zhejiang University Press.ISBN 978-7-308-15907-4Since Prof.Jǒrg SCHLAICH from the University of Stuttgart in Germany built the first solar chimney power plant(SCPP)prototype in the early1980s,research on SCPP technology has aroused worldwide attention from experiment,to theory and then feasibility studies for large-scale

Effect of Impeller Solidity on the Generating Performance for Solar Power Generation

According to current solar power research,both the generating unit’s minimum start-up speed and power generation system’s minimum flow rate for operation decrease with the increase in the impeller solidity.Ideally,a high solidity should be achieved,as this translates more power for a solar power system in the start-up and shut-down cycles.However,increasing the number of blades does not increase the impeller solidity;therefore,there is an optimal number of blades needed to achieve the preferred solidity.This paper begins by selecting the blade airfoil and then performs a theoretical analysis based on the relationship between the blade number and chord length.Experiments are conducted to measure the starting and stopping wind speeds and power characteristics for different numbers of blades.The results show that a maximum impeller solidity of 0.2862 is achieved,as well as the minimum flow speed at the start-up,and the maintenance of the solar chimney power generation system is optimized when there are four blades.

Wind-Thermal Environmental Characteristic of Multi-Variable Passive Enhanced Natural Ventilation System for High and Large Space Building

Natural ventilation effects in high and large space buildings of tropical areas greatlya ffect the air conditioning energy consumption.Aiming at nearly zero energy building design,thisp aper mainly contributes to provide theoretical basis and reference for thermal comfortable air conditioning system design of high and large space buildings.Taking a theatre in Hainan as study object,a newly composite enhanced natural ventilation system is proposed by integrating theu nderground tunnel-based earth to air heat exchange system and the solar chimney.Ventilationq uantity,air velocity and air temperature field,human vertical temperature gradient differenceu nder24simulation working conditions are considered and analyzed by using ANSYS Fluent.Fort he underground tunnel,results show that Group Two with double underground tunnels and side airs upply location shows its advantages in cooling effects and air supply uniformity.Then for the solar chimney,results show that the solar radiation intensity contributes to larger difference int ransmission power and leads to different cooling effects.On the whole,the system under workingc ondition No.7with120m long,side air supply,double underground tunnel and20m high,1mw ide,0.6°absorber plate angle solar chimney shows its priority in better comprehensive performance.