A Solar Chimney for renewable energy production: thermo-fluid dynamic optimization by CFD analyses

Synergistic energy solutions: Solar chimney and nuclear power plant integration for sustainable green hydrogen, electricity, and water production

The concept of using flue gas waste heat as a backup in a solar chimney power plant is driven by the objective of solar chimney plant performance enhancement. This paper presents experimental results of thermal field of hybrid solar-flue-gas chimney power plant at different mode (solar mode, hybrid mode and flue gas mode). The experimental test rig consisted of two inclined absorber plate and diffuser surface with total area of 3.15 m 2 , flue gas channel (1m 3m 0.05m), greenhouse (air flow channel of 1m 3m 0.16m at inlet and 1m 3m 0.075m at exit), chimney of diameter 0.15m and height of 4m, flue gas inlet diffuser (1m 0.3m 0.05m) and flue-gas source (biomass burner coupled with centrifugal blower powered using a variable speed motor). The temperature distribution in the hybrid solar-flue gas chimney power plant test-rig was measured. Temperature difference between the chimney base (absorber plate exit air) and the ambient were studied which is the driving force in solar chimney power plant. On solar mode, the driving force (temperature difference between the absorber plate exit air and the ambient air) gave a maximum dT of 27.6 °C at irradiance of 797 W/m 2 . With flue gas as thermal backup during the day, maximum dT reached 38.1°C for inlet flue-gas temperature of 101.6 °C and irradiance of 672 W/m 2 , with flue gas as the only source of thermal energy (night mode), the temperature difference, dT, got up to 25.9 °C at a flue-gas inlet temperature of 107.6 °C. The solar mode experiment carried out after night mode experiment shows that the dT of the system the next day was enhanced as the temperature difference increased from sunrise contrary to the low temperature raise experienced on normal solar day.

South Africa has limited reserve electricity resources and many parts of the country have limited access to electricity. Predictions suggest South Africa will have a serious electricity allocation problem in the very near future, and current rolling blackouts in many of our cities can attest to the looming problem. The energy crisis in South Africa has highlighted the need to increase electricity generation capacity and to search for alternative energy sources. Solar chimney plants could form part of the solution in the near future in South Africa to create additional power. Solar radiation energy is abundant in South Africa, while wind sources are limited mainly to coastal regions. Presently, wind turbine technology is more efficient than solar voltaic cells. This study develops a wind generation system in areas where wind is absent. A solar chimney power plant is expected to provide remote areas in South Africa with electric power, or complement the current electricity grid. Solar energy and the psychometric state of the air are important to encourage the full development of a solar chimney power plant for the thermal and electrical production of energy for various uses. A solar chimney power plant consists of a greenhouse roof collector, and the chimney is located at the centre. The chimney is used to direct and vent the low density air through a wind turbine which in turn converts the air enthalpy into mechanical energy. The main advantage of a solar chimney system lies in its low maintenance cost, the simplicity to operate and the durability of the system. Research of a design within the South African context and particularly on increasing the effectiveness of the solar chimney power plant technology is lacking. Several simulations were performed to find the optimum design configuration to focus the research. The results from the simulations were used to design the best configuration for a pilot plant. * Symbols : A : Area, m2 b : Breadth, m C : Circle diameter, m Cair : Heat Capacity of air = 0.0342, J/kg K Cv : Heat Capacity of air at a constant volume, J/kg K E : Energy, J Ek : Kinetic Energy, J g : Gravity acceleration = 9.81, m/s2 h : Height, m L : Height of straight chimney, m m : Mass, kg m : Mass flow rate, kg/s P : Pressure, Pa P : Atmospheric pressure, Pa PE : Potential Energy, J Pel : Electrical Power, W/m2 Q : Flow rate, m3/s r : Radius, m Rair : Air constant = 287.058, J/Kg K s : Square diameter, m T : Temperature, K V : Velocity, m/s Wturbine : Power of turbine, W Greek symbols : ρ : Density, kg/m3 η : Efficiency, % γ : Specific heat ratio Subscripts : 1 : Inlet of the solar collector 2 : Inlet of the wind turbine/outer of the solar collector 3 : Inlet of solar chimney/outlet of the wind turbine 4 : Outlet of solar chimney

This work is part of a joint project funded by the Science and Technology Development Fund (STDF) of the Arab republic of Egypt and the Federal Ministry of Education and Research (BMBF) of the Federal Republic of Germany. Continuation of the use of fossil fuels in electricity production systems causes many problems such as: global warming, other environmental concerns, the depletion of fossil fuels reserves and continuing rise in the price of fuels. One of the most promising paths to solve the energy crisis is utilizing the renewable energy resources. In Egypt, high insolation and more than 90 percent available desert lands are two main factors that encourage the full development of solar power plants for thermal and electrical energy production. With an average temperature of about 40 °C for more than half of the year and average annual sunshine of about 3200 hours, which is close to the theoretical maximum annual sunshine hours, Aswan is one of the hottest and sunniest cities in the world. This climatic condition makes the city an ideal place for implementing solar energy harvesting projects from solar updraft tower. Therefore, a Solar Chimney Power Plant (SCPP) is being installed at Aswan City. The chimney height is 20.0 m, its diameter is 1.0m and the collector is a four-sided pyramid, which has a side length of 28.5 m. A mathematical model is used to predict its performance. The model shows that the plant can produce a maximum theoretical power of 2 kW. Moreover, a CFD code is used to analyse the temperature and velocity distribution inside the collector, turbine and chimney at different operating conditions. Static calculations, including dead weight and wind forces on the solar updraft chimney and its solar collector, have been performed for the prototype. Mechanical loading and ambient impact on highly used industrial structures such as chimneys and masts cause lifetime-related deteriorations. Structural degradations occur not only from rare extreme loading events, but often as a result of the ensemble of load effects during the life-time of the structure. A Structural Health Monitoring (SHM), framework for continuous monitoring, is implemented on the solar tower. For the ongoing case study, the types of impacts, the development of the strategic sensor positioning concept, examples of the initially obtained results and further prospects are discussed. Additional wind tunnel tests have been performed to investigate the flow situation underneath the solar collector and inside the transition section. The flow situation in and around the SCPP has been simulated by a combination of the wind tunnel flow and a second flow inside the solar tower. Different wind tunnel velocities and volume flow rates have been measured respectively. Particle Image Velocimetry (PIV) measurements give some indication of the flow situation on the in- and outside of the solar tower and underneath the collector roof. Numerical simulations have been performed with the ANSYS Fluent to validate the experimental tests.

Analysis and feasibility of implementing solar chimney power plants in the Mediterranean region

The aim of the work presented in this study is related to solar chimneys energy performances determination, and flow modelling analysis, according to certain dominant parameters. The analysis of the problem presented in this paper is structured into two parts: the first one, is corresponding to energy calculation, for the prediction of the performances, such as the output and the power delivered by a solar chimney power plant (SCPP), according to some geometrical and physical parameters, such as the height and the solar radiation. The second one is related to the modelling of the air flow in the chimney. It consists, in analysing a natural convective heat transfer problem, that take place in a solar chimney plant were the thermo- hydrodynamic aspects of the air flow through an axis symmetric system with well defined boundary conditions is examined. Obtained results are related to the temperature, and the velocity distributions in the device were they are determined by solving the energy and the Navier and Stokes equations, by using the finite volume method. A specific consideration is given to identify the adequate position, in order to choose, and to optimize the site of the wind turbine in the chimney.

A solar chimney power plant (SCPP) is a renewable power technology which is able to convert heat energy from solar radiations to mechanical powers. In this study, the influence of geometric variation of the tower on the Air Velocity of one SCPP is numerically investigated. Regarding the importance of the kinetic power of the hot air on power generation of SCPP, This article aims to propose an approach to increase the air velocity by considering the various forms of the chimney without changing the main dimensions of SCPP. This approach increases the efficiency of the power plant. For the numerical simulations, a commercial CFD code solves the governing equations using the finite volume method. To simulate the problem in the 3-dimensional setting, by cutting a 15 degrees wedge out of the whole power plant geometry, a pi-shape domain is created. In order to validate the obtained results, the Manzanares Power Plant experimental data are utilized. In this study, ten forms of chimney wall based on a logical procedure are examined. By considering this procedure, an appropriate divergence form for the chimney wall is obtained. These results indicate that the final form (i.e. the divergence form of the chimney wall) has the highest updraft air velocity which is an important factor on wind turbine power generation. In addition, the average updraft air velocity increases from 15.66 m/s for the basic form to the value of 22.52 m/s for the best form (form 7), (i.e. the increment of around 43.81%).

Economic and environmental assessment of the implementation of solar chimney plant for water production in two cities in UAE

Historic and recent progress in solar chimney power plant enhancing technologies

Enhanced power generation through integrated renewable energy plants: Solar chimney and waste-to-energy

The solar chimney power plant (SCPP) is a modernistic and promising technology, which utilizes the combination of solar heating and chimney effect for producing electricity. Solar collector, updraft tower and air turbine are the main components of a solar chimney unit, however, the turbine plays a royal role because it converts the kinetic energy of the heating air into useful mechanical energy. In this study, I measured the power, flow rate, rotational speed and pressure drop of the designed and industrial turbines within the wind tunnel, and the power coefficient of the turbines are calculated by measured values. The turbine was designed according to the blade element theory modified to consider the surrounding duct. we measured the electric power, flow rate and pressure drop of the turbine, and the power coefficient of the turbine is calculated by measured values. Testing of the designed and industrial turbine within wind tunnel shows that the highest power coefficient of the designed turbine is 0.45, while the highest power coefficient of the industrial turbine is 0.32. The designed turbine produces 28.89% higher than the industrial one.

In the presented work, it is made a numerical study about the main physical principle of a solar chimney (SCPP – Solar Chimney Power Plant) and the influence of some geometric parameters on the available power in the SCPP. The main objectives are to test the applicability of the studied numerical model in future studies of SCPP geometric optimization and to test the action of the collector inlet height (H1) and the chimney outlet diameter (D2) on the available power of the device. For that it is considered an incompressible, turbulent, steady flow with mixed convective heat transfer in a two-dimensional and axisymmetric domain, similar to the one found in a solar chimney. The conservation equations of mass, momentum and energy are numerically solved using the finite volume method, more specifically with the FLUENT software. The classical turbulence modeling (RANS) was used for the turbulence approach with standard model k – ε. The other geometric parameters: collector radius (R) and the inlet and outlet of the turbine section, R1 and R2, are also constant. The verification results indicated a good agreement with those presented in the literature, even using a simplified domain. It was also observed that the H1 parameter is almost insensitive in the solar chimney performance, whereas the D2 variable presented great influence in the available power. The best performance was attained for an intermediate value of D2, D2 = 0.44 m. For this value, the available power was almost 72% and 19% higher from those obtained in the inferior and superior extremes of the studied D2 variable, D2 = 0.22 m and 0.88 m, respectively. It was also observed that there is a very good possibility of optimization of the chimney geometry in future studies.

1.1 Floating Solar Chimney technology description The purpose of this chapter is to present the Floating solar chimney (FSC) technology, look for the site www.floatingsolarchimney.gr, in order to explain its principles of operation and to point out its various significant benefits. This technology is the advisable one for candidacy for large scale solar electricity generation especially in desert or semi desert areas of our planet and a major technology for the global warming elimination. The solar chimney power plants are usually referred to as solar updraft towers (http://en.wikipedia.org/wiki/Solar_updraft_tower) and the related solar chimneys are huge reinforced concrete structures. However due to the high construction cost of the concrete solar chimneys the solar up-draft tower technology is expensive demanding a high initial investment in comparison to its competitive solar technologies. Their solar up-draft towers are huge structures of high initial investment cost that can not be split into small units. That is possible for the relatively also expensive PV solar technology. Also the solar updraft technology is far more expensive compared to the conventional fossil fueled power plants of similar electricity generation. That is why the solar chimney technology has not yet been applied although it is a solar technology of many advantages. The Floating Solar Chimney (FSC) is a fabric low cost alternative of the concrete solar chimney up-draft towers that can make the Floating Solar Chimney technology cost competitive in comparison not only with the renewable electricity generation technologies but also with the conventional fossil fueled electricity generation technologies. Also the FSC technology is cost effective to be split into small units of several MW each. The Floating Solar Chimney Power Plant, named by the author as Solar Aero-Electric Power Plant (SAEP) due to its similarity to the Hydro-Electric power plant, is a set of three major components: • The Solar Collector. It is a large greenhouse open around its periphery with a transparent roof supported a few meters above the ground. • The Floating Solar Chimney (FSC). It is a tall fabric cylinder placed at the centre of the solar collector through which the warm air of the greenhouse, due to its relative buoyancy to the ambient air, is up-drafting. • The Turbo-Generators. It is a set of air turbines geared to appropriate electric generators in the path of up-drafting warm air flow that are forced to rotate generating electricity. The gear boxes are adjusting the rotation speed of the air turbines to the generator rotation speed defined by the grid frequency and their pole pairs. Source: Solar Energy, Book edited by: Radu D. Rugescu, ISBN 978-953-307-052-0, pp. 432, February 2010, INTECH, Croatia, downloaded from SCIYO.COM

Solar chimney power plants (SCPP) exploit solar radiation to create an up-draft airflow to run a turbine. This article proposes an innovative design of an SCPP that consists of transparent glass covered solar collector. Outdoor experiments have been carried out in the arid climates of Tikrit city, Iraq, with galvanized metal tower installed instead of conventional PVC solar towers. Performance of the SCPP has been studied with and without transparent cover for collector periphery heights of 2 and 4 cm. Measurements of ambient temperature, chimney inlet temperature, interior and outlet air temperatures, humidity, air mass flow rate, and solar irradiance values were recorded from 9:00 am to 4:00 pm throughout the month of May 2021. Results show that the solar chimney collector with a periphery height of 2 cm performed better than that with the 4-cm periphery height. In addition, using transparent cover in SCPP increases the air outlet temperature by 16.4°C and air flowrate augments by around 34%. Thermal efficiency of the solar chimney with non-covered tower is found to be 10.3% whereas for a glass covered tower it increases to 14.6%, which is a remarkable 41% enhancement. Likewise, mechanical and electrical power output augment by 39.6% and 40.3% using transparent cover in SCPP. Such innovation in SCPP design is proven apposite for hot arid climates.

A solar chimney power plant has three major components: (1) A circular solar collector (Greenhouse) (2) A tall cylinder in the center of the solar collector ( Solar Chimney) (3) A set of air turbines geared to electric generators around the bottom of the solar chimney The air warms up inside the greenhouse by the solar irradiation and, due to its buoyancy, tends to escape through the Solar Chimney. This warm stream of air is leaving part of its thermodynamic energy to the air turbines placed in the path of the airflow. The solar chimney power stations were named Solar Aero-Electric Power Plants (SAEPPs) due to their similarity to Hydro Electric Power Plants. The efficiency of the SAEPPs is roughly proportional to the height of their solar chimneys. Solar Chimneys can be made as reinforced concrete structures (Concrete Solar Chimneys, CFCs), or as lighter than air inflated structures (Floating Solar Chimneys FSCs). These floating solar chimneys are made by successive balloon tubes, filled with a lighter than air gas. This permits to the FSCs to float in the air and thus to have heights 1.5divide3 Km giving to their SAEPPs higher efficiencies than Concrete Solar Chimney SAEPPs. Using ground thermal storage, or artificial thermal storage in the form of water in closed plastic tubes, it can be proved that the SAEPPs can operate 24 hours per day 365 days per year with a minimum guaranteed power production. This means that the SAEPPs, although renewable by nature, can have a similar operation to conventional power stations and thus can replace them. In the present paper a comparison for construction cost of SAEPPs with Floating Solar Chimneys and Concrete Solar Chimneys is given. It is shown that FSC Technology Power Plants is 5 to 6 times cheaper than CFC Technology Power Plants.