Solar Chimney Plant Research Articles

Optimization of Design Parameters of Wind Turbine Blade for a Solar Chimney Plant Using Betz and Bernoulli’s Theories

Optimization of Design Parameters of Wind Turbine Blade for a Solar Chimney Plant Using Betz and Bernoulli’s Theories

An application of artificial neural network (ANN) for comparative performance assessment of solar chimney (SC) plant for green energy production

This study aims to optimize the power generation of a conventional Manzanares solar chimney (SC) plant through strategic modifications to the collector inlet height, chimney diameter, and chimney divergence. Employing a finite volume-based solver for numerical analysis, we systematically scrutinize influential geometric parameters, including collector height (hi = 1.85 to 0.1 m), chimney inlet diameter (dch = 10.16 to 55.88 m), and chimney outlet diameter (do = 10.16 to 30.48 m). Our findings demonstrate that reducing the collector inlet height consistently leads to increased power output. The optimal collector inlet height of hi = 0.2 m results in a significant power increase from 51 to 117.42 kW (~ 2.3 times) without additional installation costs, accompanied by an efficiency of 0.25%. Conversely, enlarging the chimney diameter decreases the chimney base velocity and suction pressure. However, as turbine-driven power generation rises, the flow becomes stagnant beyond a chimney diameter of 45.72 m. At this point, power generation reaches 209 kW, nearly four times greater than the Manzanares plant, with an efficiency of 0.44%. Nevertheless, the cost of expanding the chimney diameter is substantial. Furthermore, the impact of chimney divergence is evident, with power generation, collector efficiency, overall efficiency, and collector inlet velocity all peaking at an outer chimney diameter of 15.24 m (corresponding to an area ratio of 2.25). At this configuration, power generation increases to 75.91 kW, approximately 1.5 times more than the initial design. Remarkably, at a low collector inlet height of 0.2 m, combining it with a chimney diameter of 4.5 times the chimney inlet diameter (4.5dch) results in an impressive power output of 635.02 kW, signifying a substantial 12.45-fold increase. To model the performance under these diverse conditions, an artificial neural network (ANN) is effectively utilized.

Design characteristics and validation of the turbine model — Case of development of turbine effect in sloped collector solar chimney plant

Blade design for a solar chimney power plant turbine is modeled geometrically. NACA 4412 blade is selected for its favorable lift to drag characteristics in the considered diameter range. The constructed model is integrated into a solar chimney plant and validated against existing examples in literature. A similar process is applied using a reverse fan model. Margins of discrepancies obtained from the turbine and reverse fan models are used as indicators for the total deviation expected from using the reverse fan model with a sloped collector plant. Here, the effect of turbine pressure change on the temperature rise and air flow are examined to set the upper limit of pressure drop and check the capacity of the system for power generation. The maximum air flow velocity at the center of the sloped collector reached 9.8 m/s. The highest achievable temperature difference was 37 °C. The favorable working zone for turbine operation inside the tower of a sloped collector solar chimney in terms of pressure drop and air flow rate is marked based on a constant efficiency.

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

• Solar chimney power plant (SCPP) system is used to generate electrical power and produce distilled water for different wind speeds in two cities in UAE. • Sharjah and Alain cities in UAE were selected based on the geographic location and metrological data. • Alain city shows more annual electrical power and water production than Sharjah city. • The economic and environmental considerations were evaluated and compared with the reverse osmosis (RO) technique. In this paper, a solar chimney power plant (SCPP) system is modeled and simulated using MATLAB code. The economic and environmental considerations were analyzed for the SCPP. The implementation of the SCPP system in Sharjah and Al Ain cities in the United Arab Emirates (UAE) were compared in terms of electrical power generation and cumulative water production, as well as the potential of increasing the wind speed by 2.5% - 10% with a step of 2.5%. The selected cities were considered due to the big difference in the relative humidity. The results showed that even though Sharjah’s water production was more stable and consistent, Al-Ain would have significantly higher water production and slightly lower power generation. After increasing the wind speed, both cities showed similar behavior of a significant increase in water production and a slight decrease in power generation. The novel design was analyzed and compared to the reverse osmosis technology from an economic and an environmental perspective. Using the SCPP is in alignment with the 2030 vision of the UAE for both electrical power generation and water production. Furthermore, the SCPP can be an effective solution to solve the demand for energy and water and reduce the effect of greenhouse gas (GHG) emissions.

Fluid dynamic performances of a solar chimney plant: Analysis of experimental data and CFD modelling

A pilot plant of a solar chimney was tested for about 7 months in a suburban area near Naples (Italy) from February to August 2020. The solar chimney is 5 m high with a square-shaped collector of 4.5 m length on each side. In this paper we report and analyse data with the aim to study the fluid dynamic performances. Correlations between air flow and ambient parameters (solar irradiance, temperature, and relative humidity) are studied. A CFD model is developed to simulate the thermal and fluid dynamic behavior of the chimney. Results are useful for a better knowledge of the performances of solar chimneys and their main operating parameters such as air velocity, flow rate, temperature, and residence time that are very useful for the correct design of solar chimneys both as electrical power plants and as atmospheric pollutant abatement plants.

Experimental Investigation on The Effect of Divergent Tower Solar Chimney on The Theoretical Power Potential

Solar chimney power plant is a sustainable alternative for electricity generation using solar as the source of energy. In general, the main body of a solar chimney plant requires a tall structure which is costly and challenging to construct. Thus, it is important to increase the performance of the solar chimney power plant and have a better energy-cost ratio. This study aims to experimentally investigate the influence of divergent solar chimney as opposed to a cylindrical chimney on solar chimney performance. Three divergent scaled-down solar chimney model at 1-meter, 1.5-meter and 2-meter were fabricated and tested for its performance at various simulated heat loads. The test results were compared with similar heights cylindrical solar chimney. The experiments show that divergent solar chimney increases the theoretical power generation potential and improves the stalk effect and have higher outlet velocity compared to a cylindrical solar chimney. The power potential of the divergent chimney is increased up to 18 times with the maximum theoretical power obtain at 0.183W on the 2-meter divergent chimney. Higher temperature was recorded on the 2-meter divergent chimney outlet at 341.3k compared to 330.4k on the cylindrical chimney indicates better stack effect. The highest average velocities in the divergent and cylindrical chimneys were recorded under the electric heat load of 2 kW at 0.994 m/s and 0.820 m/s respectively in the 1-meter configuration. It is also observed that the air velocity in a shorter divergent chimney is higher than taller divergent chimney models while better compared to all cylindrical height. This study finds that a shorter divergent solar chimney produces greater energy compared to a higher cylindrical solar chimney. Therefore, it is possible to reduce the overall cost of solar chimney by reducing the height of the main structure without sacrificing the performance of the solar chimney.

Solar desalination tower, novel design, for power generation and water distillation using steam only as working fluid

The use of sustainable energy resources is indispensable nowadays. This paper studies a new solar chimney plant for electrical power generation and water distillation. The operating mechanism of the power plant is based on evaporating seawater using concentrated solar power techniques. The novelty of the proposed system is using steam only as working fluid; also, the collector area is separated away from the solar chimney. The solar field absorbs and transfers solar energy into the steam generator. As steam passes through the chimney, the vapor exchanges the heat with the outside environment resulting in water condensation at the inner surface of the chimney. A set of equations have been developed, and a hybrid integrated solar combined cycle (ISCC) is constructed for comparison purposes. In general, the results show that the proposed system can improve the efficiency of the solar utilization of the new solar chimney with 78% more than the conventional ISCC system. The geometrical dimensions of the solar field and chimney of the new system are smaller than the traditional one; therefore, the estimated capital cost ($/m2) will be relatively less.

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.

CFD Analysis of Hybrid Solar Chimney Power Plant

In this study, a novel approach has been proposed as a solar chimney integrated with an external heat source to extend the system operation during the absence of solar energy. Flue gas channels have been utilized to exchange heat with the air inside the collector of the solar chimney. The hybrid solar chimney has been investigated numerically by ANSYS-Fluent software, using discrete ordinates radiation model. The hybrid system was simulated in 3D, steady-state by solving Navier-Stokes and energy equations. The numerical results have been validated using experimental measurements of a conventional solar chimney. The influence of flue channels on the system performance was predicted and analyzed in hybrid mode. With 0.002 kg/s of flue gas at 100°C injected in flue channels during the daytime; hybrid mode results demonstrated enhancement of 24% and 9 % for velocity and temperature, respectively. The power generation was enhanced by 56%. It has been proved that the proposed technique is able to resolve the set back of night operation problem of the solar chimney plants.

New design of solar chimney (case study)

The solar chimney power plant has a promising future in the world. Α new design of solar chimney is offered including both PV panels with solar chimney plant for electricity generation. Two experimental models of a hybrid solar chimney were built and designed (systems A&B). System (A) had a collector glass roof cover and a PV panel as an absorber with a chimney of 2m height while system (B) is similar to system (A) but with PV panel as collector roof cover and plywood as an absorber in the base of the chimney.Two similar experimental models were built to achieve the performance of these new designs. Practical tests were conducted in Kirkuk (35° 28' latitude and 44° 24' longitude), northern Iraq. The results showed that system (A) had higher thermal gain than system B while the daily average of electrical power in system (B) was (75.6W) higher than system (A) (79W). This is because the high thermal gain raised the operating temperature of the PV panel which led to a decrease in its power output. The results also presented that system (A) converted thermal power to kinetic power with daily average (0.008W) because of the great thermal gain which made air less dense in turn increased its velocity more than system (B) (0.006W) which had lower kinetic power. The total useful power produced by the system (B) is greater than the useful power produced from the system (A).

Development and performance investigation of a novel solar chimney power generation system

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

Scenarios for solar thermal energy applications in Brazil

The Solar and Wind Energy Resource Assessment (SWERA) database is used to prepare and discuss scenarios for solar thermal applications in Brazil. The paper discusses low temperature applications (small and large scale water heating) and solar power plants for electricity production (concentrated solar power plants and solar chimney plants) in Brazil. The results demonstrate the feasibility of large-scale application of solar energy for water heating and electricity generation in Brazil. Payback periods for water heating systems are typically below 4 years if they were used to replace residential electric showerheads in low-income families. Large-scale water heating systems also present high feasibility and many commercial companies are adopting this technology to reduce operational costs. The best sites to set up CSP plants are in the Brazilian semi-arid region where the annual energy achieves 2.2MWh/m2 and averages of daily solar irradiation are larger than 5.0kWh/m2/day. The western area of Brazilian Northeastern region meets all technical requirements to exploit solar thermal energy for electricity generation based on solar chimney technology.

Accuracy of theoretical models in the prediction of solar chimney performance

A solar chimney is a solar power plant which generates mechanical energy (usually in terms of turbine shaft work) from a rising hot air that is heated by solar energy. The present paper compares the predictions of performances of solar chimney plants by using five simple theoretical models that have been proposed in the literature. The parameters used in the study were various plant geometrical parameters and the insolation. Computational Fluid Dynamics (CFD) simulation was also conducted and its results compared with the theoretical predictions. The power output and the efficiency of the solar chimney plants as functions of the studied parameters were used to compare relative merits of the five theoretical models. Models that performed better than the rest are finally recommended.

Flow Through a Solar Chimney Power Plant Collector-to-Chimney Transition Section

A solar chimney power plant consists of a large greenhouse-type collector surrounding a tall chimney. The air, heated within the collector, passes through an inlet guide vane (IGV)cascade and then through a transition section to a turbine that powers a generator. The transition section contains the turbine inlet guide vanes that support the whole chimney and guides the flow entering the turbine. The primary objective of the study was to determine the loss coefficient and mean exit swirl angle of the flow passing through the collector-to-chimney transition section of a full-scale solar chimney power plant as dependent on IGV stagger angle and collector roof height. Very good agreement was found between experimental values measured in a scaled model and commercial CFD code predictions of flow angles, velocity components, and internal and wall static pressures. The agreement between measured and predicted total pressure loss coefficient was reasonable when considering how small it is. The CFD code served to extend the predictions to a proposed full-scale geometry. Semi-empirical equations were developed to predict the loss coefficient and turbine mean inlet flow angles of solar chimney power plants as dependent on collector deck height and inlet guide vane setting angle. The two empirical equations may be useful in solar chimney plant optimization studies.

Counter-rotating turbines for solar chimney power plants

An efficiency model at design performance for counter-rotating turbines is developed and validated. Based on the efficiency equations, an off-design performance model for counter-rotating turbines is developed. Combined with a thermodynamic model for a solar chimney system and a solar radiation model, annual energy output of solar chimney systems is determined. Two counter-rotating turbines, one with inlet guide vanes, the other without, are compared to a single-runner system. The design and off-design performances are weighed against in three different solar chimney plant sizes. It is shown that the counter-rotating turbines without guide vanes have lower design efficiency and a higher off-design performance than a single-runner turbine. Based on the output torque versus power for various turbine layouts, advantageous operational conditions of counter-rotating turbines are demonstrated.

Solar chimney turbine characteristics

A typical layout of a solar chimney power plant has a single axial turbine with radial inflow through inlet guide vanes at the base of the chimney. Turbine efficiency depends on the turbine blade row and turbine diffuser loss coefficients. The paper presents analytical equations in terms of turbine flow and load coefficient and degree of reaction, to express the influence of each coefficient on turbine efficiency. It finds analytical solutions for optimum degree of reaction, maximum turbine efficiency for required power and maximum efficiency for constrained turbine size. Characteristics measured on a 720 mm diameter turbine model confirm the validity of the analytical model. Application to a proposed large solar chimney plant indicates that a peak turbine total-to-total efficiency of around 90% is attainable, but not necessarily over the full range of plant operating points.