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Abstract The characteristics of the wind at 10 m height were studied over a period of 32 months. The sampling interval was 20 ms and the averaging time was 10 min. Probability density functions are given for the speed, direction, inclination and intensity of turbulence of the wind. Frequency contour plots are given for wind speed vs solar time, wind speed vs wind direction, wind speed vs global solar irradiance and wind speed vs the intensity of turbulence of the wind. Differences between the results for day and night and between various seasons are examined.

Dynamic stall (DS) on a wind turbine is encountered when the sectional angles of attack of the blade rapidly exceeds the steady-state stall angle of attack due to in-flow turbulence, gusts and yaw-misalignment. The process is considered as a primary source of unsteady loads on wind turbine blades and negatively influences the performance and fatigue life of a turbine. In the present article, the control requirements for DS have been outlined for wind turbines based on an in-depth analysis of the process. Three passive control methodologies have been investigated for dynamic stall control: (1) streamwise vortices generated using vortex generators (VGs), (2) spanwise vortices generated using a novel concept of an elevated wire (EW), and (3) a cavity to act as a reservoir for the reverse flow accumulation. The methods were observed to delay the onset of DS by several degrees as well as reduce the increased lift and drag forces that are associated with the DSV. However, only the VG and the EW were observed to improve the post-stall characteristics of the airfoil.

Environmental pollution is a principal concern for all countries. In particular, the issue is alarming for Australia as the country has been suffering from various environmental disasters for some recent years. Therefore, examination the roles of some variables that are related to environment are vital. To this end, this work endeavors to ascertain the impacts of industrialization, non-renewable and renewable energy use, and financial development on environmental pollution in Australia. Using the data period of 1990 e2020, a series of econometric techniques such as the Augmented Dickey-Fuller test, Phillips-Perron test, Autoregressive Distributive Lag (ARDL) bounds test and the pairwise Granger causality test are applied. The findings reveal that industrialization and non-renewable energy use increase while the square of industrialization, renewable energy use, and financial development reduces CO2 emissions in Australia. The validation of the environmental Kuznets’ curve (EKC) hypothesis is also found. Bidirectional and unidirectional causal association of the studied variables with CO2 emissions are attained. All the outcomes are theoretically and empirically relevant and have important policy implications.

Abstract Sweet sorghum plant, containing starchy grain, juice, and bagasse, is a potential energy crop for biobutanol production as an advanced renewable fuel. This paper assesses the economy of production of butanol from the whole sweet sorghum plant based on available experimental results. Different scenarios, including separate hydrolysis and fermentation (scenarios 1 and 2), simultaneous saccharification and fermentation (scenario 3), and co-fermentation of the juice and pretreated stalk (scenario 4), were simulated using Aspen Plus®. Moreover, in scenarios 5 and 6, the stalk is directly fed to the fermenters without juice extraction and pretreatment. Gas stripping was used to enhance the recovery and fermentation yield in scenarios 2 to 6. Acetone, supplied from the process products, was used for bagasse pretreatment in scenarios 1–4. Economic viability was investigated using Aspen Process Economic Analyzer. The butanol production price was 0.62, 0.44, 0.45, 0.61, 0.39, and 0.56 US$/L for scenarios 1 to 6, respectively. The most profitable process was scenario 5, where US$47.75 million total capital is required for the production of 11,260 tonne/year butanol. The sensitivity analysis of butanol sales price showed that even in the case of its value reduction by 50%, scenario 5 can still be profitable.

Abstract The energy assurance and electricity supply are significant factors for progress and development of all countries. Low investment costs, reducing greenhouse emission, and high output efficiency for good performance of power plants are key factors in evaluating energy parameters for governments. This study is intended on determining and proving the compatibility of existing power plants in the country of Iran by applying observational data through the application of Multi-Criteria Decision-Making Analysis (MCDA). The obtained compromise solutions applied through a MATLAB code that helped in specifying which power plants are particularly suitable for establishment in the future work. Furthermore, it supports the generalization and validation of applying VIKOR method for thorough evaluation of power systems by comparing the results with real condition. The different types of power plants have been considered as alternatives. Multi-criteria evaluations of these diverse power plants were also carried out with respect to the environmental, technological, and economic criteria. It was concluded that hydropower plant is the best possible case for establishment, and the VIKOR method is a reliable technique for evaluating energy systems which can help to rank alternatives and determines the solution named compromise that is the closest to the ideal case.

For wind farm optimizations with lands belonging to different owners, the traditional penalty method is highly dependent on the type of wind farm land division. The application of the traditional method can be cumbersome if the divisions are complex. To overcome this disadvantage, a new method is proposed in this paper for the first time. Unlike the penalty method which requires the addition of penalizing term when evaluating the fitness function, it is achieved through repairing the infeasible solutions before fitness evaluation. To assess the effectiveness of the proposed method on the optimization of wind farm, the optimizing results of different methods are compared for three different types of wind farm division. Different wind scenarios are also incorporated during optimization which includes (i) constant wind speed and wind direction; (ii) various wind speed and wind direction, and; (iii) the more realisticWeibull distribution. Results show that the performance of the new method varies for different land plots in the tested cases. Nevertheless, it is found that optimum or at least close to optimum results can be obtained with sequential land plot study using the new method for all cases. It is concluded that satisfactory results can be achieved using the proposed method. In addition, it has the advantage of flexibility in managing the wind farm design, which not only frees users to define the penalty parameter but without limitations on the wind farm division.

Abstract Utilization of pump as turbine (PAT) systems is known as an economically beneficial method to harvest hydropower energy, especially in a remote area. Despite the extensive investigations on the operation and parametric study of the PAT components, the turbine mode of multistage PATs in case of a viscous working fluid is found as a literature gap. In this paper, a numerical simulation method is employed as a predicting tool to investigate the consequences of changing the fluid viscosity affecting the flow patterns within the multistage PATs. The commercial solver ANSYS CFX 16 was used for simulation. Validation of numerical solution was done for the single-stage pump considering water and 48 cSt viscous fluid. The numerical results in the single-stage PAT showed that increasing the viscosity causes an efficiency drop mainly at the part-load condition and translates the maximum efficiency point to higher flow rates, where the vortices at impeller passage and draft tube are weaker. Increasing the viscosity up to 48 cSt, results in 12.5% reduction of efficiency at the best efficiency point (BEP) in two stage PAT. Based on the two-stage PAT results, the total hydraulic efficiency at the BEP has been increased by 1% and 1.5% for water and the 48 cSt viscous fluid, respectively, in comparison with the single-stage PAT. According to the post-processed streamlines at different stages of the two-stage PAT, the undesired vortical structures were caused by the diffuser and the return channel, which were mainly designed for the pump mode. The hydraulic analysis of two-stage PAT shows that using multistage pumps in reverse mode is reasonable for power generation in high head and flow rate sites.