In this paper, a theoretical model for simulation of a solar updraft tower power plant with the assumption of axisymmetric condition is developed to study the impact of hot gas injection at the chimney base as well as extraction of a portion of hot gas after the turbine and re-entered it at the collector inlet. A new computational code is written by Matlab software and the effects of operational parameters are studied. Results show that the maximum power output is increased by 49. 9% by increasing the extraction fraction from 0% to 40% at a wind velocity of 10 m/s. Besides, the obtained results show that the power output is enhanced as the mass flow rate of hot gas increases. As a result, the maximum power output at a hot gas mass flow rate of 30 kg/s is approximately 37% higher than the one at a hot gas mass flow rate of 10 kg/s. Results reveal that the optimum performance of SUTPP takes place at the ratio of pressure drop across the turbine to driving pressure potential in the range from 0. 83 to 0. 87. Furthermore, the power output in the presence of wind is investigated and the positive influence of wind is illustrated. Results indicate that by increasing the wind velocity from 10 m/s to 30 m/s, the maximum power output is increased by 386. 1%

The solar vortex engine (SVE) aims to replace the tall and expensive chimney structure in solar updraft power plants by a shorter less expensive structure named the vortex generator. In this study, the entire SVE system is simulated by CFD to determine the appropriate location for the turbine unit as well as prove the capability of the vortex generator in replacing the chimney. Three different cases for the SVE are considered and compared to corresponding cases of the solar chimney power plant (SCPP). Results revealed that the optimum turbine location is at the outlet hole of the vortex generator. An updraft air velocity of 1.82 m/s was achieved at the outlet hole, compared to 1.56 m/s at the base of a solar chimney with the same diameter as the upper hole. The consideration of the turbine pressure drop did not affect the formation and preservation of the air vortex. So, the 1 m high vortex generator successfully replaced the 8.6 m chimney component in solar updraft power plants, greatly reducing the cost and construction complexity of the plant. The vortex generator accelerated the air delivered from the solar collector, increasing its velocity by 14 times. The SVE’s power output is directly proportional to the static pressure drop across the turbine. The mean difference values along the air vortex field between the cases with and without a turbine are 0.67 Pa and 0.026 m/s for the static pressure drop and velocity magnitude, respectively.

Abench-scale updraft gasifier was used as a fluidizedand fixed-bed gasification unit in three modes (fluidizedbed at equivalence ratios (ER) =0. 2 and 0. 25, and a mode in fixed-bed). The experiments were done in five different temperatures (650, 700, 750, 800 and 850oC). To obtain the required data to develop a thermodynamic equilibrium model, the proximate and ultimate analysis were carried out on potato shoot as feedstock. Since the developed model is a temperature-based model, it gives different outcomes in different temperatures. The model gave a completely exact result to predict CH4 in fluidized-bed at ER=0. 25. The average error for the difference between each produced gas in experiments and the model showed the best result of the model for CO with the error of just 0. 7%. Regarding each experiment data difference with the model data, the model was more accurate to be used in fluidized-bed, especially at ER=0. 25 than the other two modes. Moreover, the best performance of the model was obtained for CO, N2 and CO2, according to the average errors. Since the maximum amount of high heating value (HHV) and carbon conversion efficiency (CCE) was observed at higher temperatures, it can be contended that the model has better performance at higher temperatures.

Rubber wood (Ficus elastica) is one of the biomass waste that can be used as rawmaterial for gasification process, and has a calorific value of 4069 cal/g. Gasification is a process to convert a solid fuels to syngas (CO, CH4, and H2) through a partially combustion process using limited air between 20% to 40% of air stoichiometry. Depending on the direction of airflow, the gasifier are classified as updraft, downdraft, and cross-flow. The downdraft type of gasifier produces a lower tar content than updraft type. The gasification of rubber wood and rubber wood-coal mixture were carried out in this research. The purpose of the research is to determine the effect of Air Fuel Ratio (AFR) and temperature on calorific value and composition of syngas using a downdraft gasifier. The variations of AFR were 0. 64, 0. 95, and 1. 26. The temperature of gasification was varied between 600-1000º C. The result showed that the percentage of CO, H2, and CH4 decreased with increasing of AFR and decrease in calorific value. The calorific value of syngas increased along with the temperature. The use of coal in the gasification process can maintain the stable combustion temperatures and increase the syngas produced. The best-operating conditions in this research occurred at AFR of 0. 64, temperature of 800º C and use of coal as a stabilizer. At this condition, the percentage of syngas of 35. 95% of CO, 15. 95% of H2, 9. 38% of CH4, and caloric value of 9. 42 MJ/m3 was obtained. The highest gasification yield of 35. 75% was also reached.

This paper presents computational fluid dynamics (CFD) simulation of the solar chimney power plant to analyze to analyze buoyancy-nature of heated air by har-nessing solar energy. ANSYS Fluent a fi nite volume code has been used for axisym-metric model of the solar chimney power plant (SCPP) prototype in Manzanares, Spain considering updraft tower. A standard k- turbulence model and Boussinesq approximation for buoyancy driven flow is considered. Small pressure difference because of natural draft inside the chimney during day time has been observed due to solar radiation. The numerical results obtained for average velocity and temper-ature at chimney inlet are validated with the experimental results of the prototype. It has been observed that both the velocity and temperature of air inside the SCPP increases signifi cantly with the increment in solar radiation. Increase in the chimney height and collector radius also increases the power output of the plant. The effect of chimney convergence with different area ratio on the power output of SCCPs have been analyzed.

The study was aimed examine the effect of microwave preheated pyrolysis on the characteristics of volatile metal compounds. In order to monitor the behavior of volatile metals, samples were preheated with microwave oven in varying energy ranges and process durations. In order to determine optimum conditions, 360-, 600- and 900-W microwave power and 3-, 5- and 10-min microwave irradiation were used. Chemical analyses of samples were carried out both before and after experiments by X-ray fluorescence. Pyrolysis experiments were performed in a laboratory-scale fixed-bed updraft stainless steel reactor in the presence of 1 L min-1 N2 gas. Content of synthetic gas product obtained via pyrolysis was analyzed by a continuous gas analyzer. Microwave preheated pyrolysis resulted an increase in the weight percentage of calcium oxide, iron (III) oxide, and chromium (III) oxide in galvanic sludge. Similar changes were determined for most of the samples at 600 W and 5 min of microwave preheated pyrolysis. In this point, the weight percentage of calcium oxide, iron (III) oxide, and chromium (III) oxide were measured as 22.47, 16.93, and 5.63 wt% which were 19.86, 10.89, and 3.03 wt% after single pyrolysis. It is concluded that, future analysis are needed to increase the efficiency of stabilization by microwave preheated pyrolysis.

Cloud models can play a key role in interpreting observational evidence to estimate the potential for successful cloud seeding experiments. Among different types of cloud models, onedimensional cloud models with bulk water microphysical parameterization are very useful. Therefore in this paper, a one-dimensional Ogura and Takahashi (O-T) cloud model with bulk parameterization has been discussed for studying the possibility of improvement in microphysical processes in applying for cloud seeding experiments. The most important features of the new model could be defined as the inclusion of Kessler Parameterization (PMZ) in a warm rain process, Bigg’s freezing PMZ, and terminal velocities of rain water and hail particles. The model has been run for various cases, Kessler PMZ, Kessler PMZ and Bigg’s freezing, and Kessler PMZ, Bigg’s freezing, and Lin PMZ. Strong modifications were noticed in the rainfall profile, with Kessler PMZ rain started later due to the necessity of cloud droplets to initiate formation. Rainfall became heavier due to the accretion of cloud droplets and raindrops. With Bigg’s freezing, due to the enhancement of the freezing process rate, the second peak of rainfall intensity vanished. With Lin terminal velocities of rain and hail, due to the accumulation of rain water near the surface, the updraft became weaker, while downdraft became stronger. Due to the above mentioned improvements, the rainfall pattern of the improved model became heavier and sharper in a shorter time and is in good agreement with the behavior of occurrence of natural showers.