Numerical and Experimental Analyses of Solar Chimney Parameters

Numerical investigation of solar chimney power plants performance for Saudi Arabia weather conditions

A solar chimney power plant system is theoretically designed for future erection in Jordan. Analytical analysis of the system is simulated by mathematical software. The actual values of solar irradiation in Jordan are used in the simulation to predict the power output of the solar chimney power plant. The output results of the maximum (inlet) values of velocity, pressure, and mass flow rate of air versus the chimney height variation are obtained. Furthermore, the electrical power output and the efficiency of chimney versus chimney height variation were determined. For a solar collector diameter of 40 m and a chimney diameter of 3.5 m, the maximum power output (85 kW) was obtained for a chimney height of 210 m.

A numerical methodology has been developed to analyze the thermo-hydrodynamic aspect of airflow occurring in solar chimney power plants (SCPP) according to some dominant parameters. The general curvilinear coordinates finite volume method (GCCFVM), which is necessary in the case of turbulent flow through complex geometries, is used in this work. The governing equations describing the steady state turbulent fluid flow are solved numerically using this technique. It is shown that the chimney tower dimensions control directly the hydrodynamic field. However, the collector dimensions control directly the thermal field and indirectly the hydrodynamic field. It is demonstrated that the solar radiation influences strongly and positively the thermo-hydrodynamic field by increasing the mass flow rate. The mass flow decreases with the increase of the ambient temperature and then the system is more efficient with low ambient temperature. Indeed, the mass flow rate increases from 0.8 kg/s up to approximately 2 kg/s when the solar radiation varies between 200 W/m2 and 1000 W/m2 for fixed ambient temperature value of 30 °C. When ambient temperature increases from 10 °C up to 50 °C, the mass flow rate decreases slightly and in a linear manner from 1.7 kg/s to 1.5 kg/s for fixed solar radiation intensity value of 600 W/m2. Contrasting to other studies, conclusion based on simplified analytical models, ambient temperature affects adversely the performance of a SCPP in decreasing the mass flow rate. This conclusion should be taken into consideration when analyzing models dedicated to the prediction of solar chimney power plant performance.

The aims of this study are to enhance the performance of a solar chimney power plant (SCPP), investigate utilization of thermal energy storage (TES) and analyze the environmental impact of the SCPP in providence of Isfahan, Iran. To achieve these goals, multi-stage numerical simulations during twenty-four hours of a day are performed in climate condition of Isfahan province (central region of Iran). Isfahan province has proper environmental condition for utilization of SCPP as a source of electricity and the environmental crises during the last decade in Iran have made utilization of green power plants a necessity. Performance enhancement of the SCPP is carried out by improvement in geometrical characteristics of collector and chimney of the SCPP. Considered factors for performance enhancement of SCPP are height, ceiling slop and radius of the collector as well as height, radius and throat shape of the chimney. Then a TES is employed to produce power in the absence of solar radiation in new proposed optimal configurations. In continue carbon dioxide emission and water consumption of enhanced configurations of SCPP are compared with shale gas, coal, hydroelectric and biomass power plants for same output power to investigate environmental impact of the SCPP. Results illustrate that improved collector of the SCPP increases the output power by almost 139% and enhanced chimney of the SCPP improves performance of the power plant by approximately 68.1%. Results also show that the SCPP with the TES would produce power during night hours in a stable range and TES has higher performance in SCPP with optimal proposed configurations. The results confirm that the SCPP is a proper choice for power generation in province of Isfahan (central region of Iran) and the enhanced SCPP with TES improves the output power range and environmental benefits considerably.

Analysis of some available heat transfer coefficients applicable to solar chimney power plant collectors

Study on the Performance of a solar chimney power plant chlef, Algeria region was presented in this work. The solar chimney is used in hot areas such as Chlef with high intensity of solar radiation. In this work, the solar chimney power plant (collector, chimney and turbine) is modeled theoretically, and the global solar radiation, the air temperature was measured during the period of 01/01/2015 to 1/06/2016. The model is employed in simulation to predict the electrical power produced by the solar chimney plant using the meteorological data of Chlef region. The effect of the geometrical parameters on the performances of the solar chimney power plant was studied. The influence of chimney height on electrical power produced is simulated in order to have the optimum SCPP to respond to the electricity demand in Chlef region. The performance characteristics of solar chimneys indicate that the dimensions of the chimney (height of the chimney, diameter of the collector, height of the collector and the diameter of the chimney) and the climatic condition (air temperature and solar radiation) are important parameters in the production of electrical energy.

ABSTRACTSolar chimney power plants constitute an impressive construction by its size and its output seems low for its dimensions. Although many works have been carried out on the subject, there is still much scientific and technical improvement to be done. In the present work, we consider the modeling of turbulent flow under the effect of natural convection within a solar chimney power plant (SCPP) by performing numerical simulation using the Saturne Code coupled with Syrthes code. The objective of the study is the analysis of the collector cover slope influence on the performance of the SCPP in two cases. In the first case, the storage system considered is composed solely of the ground under the collector. For the second case, the storage system is made, in addition to the ground, of a 10 cm thick tub filled with water, covering the entire surface of the collector. The concept of minimizing the entropy production is also studied with the objective of optimizing the geometric configuration as well as the effect of the collector cover slope on the efficiency of SCPP. The boundary conditions are defined according to the meteorological data for a typical day available on the site of Adrar, Algeria. The results allow us to focus on the storage system influence on the SCPP performance and the duration of its operation after sunset. This leads to the improvement of the global efficiency of the SCPP. Results show the positive impact of the extra storage media use and the configuration which improves the velocity at the chimney entrance.

Critical evaluation of solar chimney power plant performance

An experimental study on the thermal performance of a solar chimney with different dimensional parameters

Objective: To investigate the effect of ultrasonic parameter settings on maximum temperatures in the drilling site and penetration time and determine the most suitable parameters for efficient and safe robot-based ultrasonic bone drilling in spinal surgery. Methods: Five adult bovine thoracic and lumbar vertebrae specimens (T10-L6) were cut into 10 mm thick slices. A total of 50 slices were obtained. Among them, 30 and 20 slices were used for cancellous bone experiments and cortical bone experiments, respectively. In the cancellous bone experiment, the slices were randomly divided into three groups, corresponding to different feed rates of 0.8 mm/s, 1.6 mm/s, and 2.4 mm/s, respectively, with 10 slices in each group. The cancellous part of each slice was drilled 9 times with different output powers from 20% (48 W) to 100% (120 W). In the cortical bone experiment, the slices were randomly assigned into two groups, corresponding to a different feed rate (0.8 mm/s and 1.6 mm/s). Drilling was performed on the cortical part of each slice 4 times with different output power, which increased from 70% (84W) to 100% (120 W). All experiments were conducted at room temperature of 25 ℃. Maximum temperature and penetration time were recorded. The maximum grinding temperature and penetration time of cancellous bone and cortical bone under different output power and feed rate were compared. Results: At the same feed rate, the maximum temperature of the cancellous bone decreased as output power increased. There were statistically significant differences in the maximum temperature between the output powers of 120 W and 24 W under different feed rates(61.2 ℃±9.4 ℃ vs 70.9 ℃±5.7 ℃, 59.2 ℃±7.1 ℃ vs 69.5 ℃±10.7 ℃, 55.5 ℃±5.5 ℃ vs 69.2 ℃±9.3 ℃, all P<0.05). At the premise of the same output power, there was no significant difference in the maximum temperature among different feed rates (all P>0.05). At the feed rate of 0.8 mm/s, the maximum temperature of cortical bone decreased as the output power increased. The maximum temperature at the output power of 120 W was significantly lower than that of 84 W (P=0.048). However, at the feed rate of 1.6 mm/s, the maximum temperature could not be significantly lowered by the increase in output power (P>0.05). Under the same output power, the maximum temperature at the feed rate of 1.6 mm/s were all significantly lower than those of 0.8 mm/s (all P<0.05). The penetration time of cancellous bone did not decrease significantly with the increase in the output power (all P>0.05) while it decreased significantly as the feed rate increased (all P<0.05). Regarding cortical bone at the feed rate of 0.8 mm/s, the increase in output power could not shorten the penetration time (P>0.05); at the feed rate of 1.6 mm/s, the penetration time at the output power of 120 W was significantly shorter than that of 96 W (P=0.008). With the same output power, the penetration time at the feed rate of 1.6 mm/s were significantly shorter than those at 0.8 mm/s (all P<0.05). There was no statistical difference in the penetration failure rate among different feed rates with the same output power (all P>0.05). The penetration failure rate was 0 when the output power of cancellous bone was 48 W and above and the output power of cortical bone were 108 W and 120 W. Conclusions: The maximum temperature of vertebral cancellous bone and the cortical bone is primarily influenced by the output power and the feed rate, respectively; the penetration time of cancellous bone and the cortical bone is affected by the feed rate and both of feed rate and output power, respectively. The most suitable parameters are output power of 120 W and feed rate of 2.4 mm/s for cancellous bone and output power of 120 W and feed rate of 1.6 mm/s for cortical bone.

Recently, several researches have been done to improve the perfomance of solar chimney power plants (SCPP) and increase their low output power during hours when the solar radiation is limited. In this study, by combining a SCPP and a gas power plant, the output power is increased and the power output of the combined power plant can be gained at all hours of the day and night. Pipes are buried under the ground and the outlet hot gas from gas power plant flows through the buried pipes instead of being released into the atmosphere through the stacks. Flowing of hot gas through the buried pipes at the soil under the canopy increases the temperature of soil which is exposed to the solar radiation. Increasing of the soil temperature leads to the growth in the value of air temperature under the canopy. The air density reduces as the air temperature increases which leads to the increase of air velocity and output power. By applying the buried pipes, the output power is not zero during the hours when there is no radiation flux. The results for air temperature, heat loss and output power are studied in detail and it is shown that the use of buried pipes in which hot gas flows leads to the increase of the output power of SCPP by 554%, 208% and 125% at the radiation flux of 200 W/m2, 500 W/m2 and 800 W/m2, respectively.

Numerical study on the performance of a solar chimney power plant

Development of analytical model for solar chimney power plant with and without water storage system

Economic analysis of a 1 MW solar chimney power plant in Tozeur, Tunisia

The depletion of fossil fuels and climate change are major worldwide problems. Unlike hydrocarbon resources, solar energy is a clean, inexhaustible, and sustainable power source to meet all of humankind’s energy demands. Solar chimney power plants (SCPPs) having a simple design are capable of generating large‐scale solar powered electricity. The systems have three primary components: a chimney, turbine, and collector. The optimization of the chimney geometry plays a key role in achieving the peak efficiency of SCPPs. In the current work, a three‐dimensional (3D) model on the basis of the Manzanares prototype with a chimney height ( H ) of 194.6 m and radius ( R ) of 5.08 m is developed to identify optimal height for the innovative constricted chimney section configurations via ANSYS FLUENT. The height of the narrowed chimney sections varies as 1/4, 1/8, 1/16, and 1/32 of H for a fixed radius as 1/3 of R . The findings indicate that the power output ( P o ) increases with decreasing the narrowed section height from H /4 to H /32 owing to enhanced mass flow rate and turbine pressure drop. The highest P o of 65.9 kW is gained with the configuration with the height of H /32 and P o enhances by 43.3% compared to the base case at 1000 W/m 2 . The novel equations are improved from the numerical data to estimate the performance features. Besides, the impact of the narrowed section radius on the performance is examined to optimize the dimensions of the constricted section. It is found that a decrease in the narrowed section radius from R /3 to R /5 for a constant height of H /32 leads to a reduction in P o by 1.2% because of a remarkable decrease in mass flow rate. H /32 and R /3 can be optimum height and radius value for the reduced chimney section to augment system efficiency.