Sharif Digital Repository

Recently wind turbines with vertical axis attract attention of world’s scientific society to itself because of many reasons such as: ability to work in areas with high turbulency, structural simplicity, independency from wind direction, easy maintenance and low capital cost. So that major part of recent researches in context of wind turbines are about these turbines. In this project a small sample of wind turbine from darrieus type have been designed, manufactured and finally important parameters such as Pitch Angle, Blade numbers and Aspect Ratio have been investigated. Darrieus turbine with 4 Blades and Pitch Angle of +15° was the most appropriate sample between the test samples. In the... 

Both resources have shaped the development of societies during the course of history. The increase in population, the growthe of middle-class societies, climate changes, economic development, health and environmental concerns, all play roles in magnifying or reducing the growing stresses on the vital resources of water and energy. Projections for water availability and quality, food and enrgy availability, soil and air quality are alarming. These alarms point to a major conclusion:’business as usual’ is no longer viable. Indeed, they call for a fundamental shift in the manner in which we understand and manage resources: a shift away from traditional approaches toward more integrative,... 

Aerodynamical design of backward swept for a horizontal axis wind turbine blade has been carried out to produce more power. Computational Fluid Dynamics (CFD) calculations were used for solving the conservation equations in one outer stationary reference frame and one inner rotating reference frame, where the blades and grids were fixed in reference to the rotating frame. The Reynolds Averaged Navier-Stokes (RANS) solver was validated in a test case, the National Renewable Energy Laboratory (NREL) VI blades. Simulation results show considerable agreement with the measurements. Three different turbulence models have been compared: Spalart-Allmaras, the Standard K-ε, and Shear Stress Transport... 

Recently, a lot of attention has been devoted to the use of Darrieus wind turbines because of high power density and environment aspect in urban areas. Turbine airflows don’t effect on the power coefficient of Darrieus turbine. This turbine has an acceptable power coefficient depend on the other wind turbine in the small scale turbine. Aerodynamic performance of a Darrieus turbine is very complex due to phenomena such as dynamic stall and changing forces on the turbine caused by changing horizontal angles. So study airflows around turbine must be preformed. In this thesis the aerodynamics of an H-rotor vertical axis wind turbine (VAWT) has been studied using computational fluid dynamics in... 

Wind is one of the clean energies available in the world which its damage to the environment is less than other renewable resources. One of technologies of generating energy from wind is the small turbines installed in city area. However, installing these turbines in cities may encounter with problems such as low speed of wind and high turbulence in the air causing aero-dynamic noise. If the turbines are installed in a bad place in cities, their electricity generation might be zero. Among important parameters that affect the performance of the turbines installed in the roof is the formation of the building, the buildings around, and the location of wind turbine. If the buildings’... 

This project aims to investigate environmental effect –such as dust and rain- on the performance of a vertical axis wind turbine (VAWT). However, those issues are frequently investigated in the horizontal axis wind turbines, but this subject has not been studied in vertical axis wind turbines. Impact of rain or dust particles on the turbine blades can change the turbine performance. So consideration of the impact of environmental factors on the performance of wind turbines is very important. Vertical axis wind turbines, particularly the straight bladed VAWT are widely used in wind power generation in agricultural and rural lighting and the use of this type of turbines is increasing... 

The power generation system of this type of power plants operates on the air flowing through the power plant’s chimney and colliding with the turbine blades within the chimney. When the solar collector warms the nearby air and thus expands the air by absorbing the sunlight, a difference is created in the density. Then, this difference in the density creates the phenomenon of buoyancy, making the air pass to the top of the chimney through the collector.This study simulated and optimized a solar chimney power plant. The simulation and optimization were performed based on the information of Manzanares Solar Chimney Power Plant in Spain (located in 150 km from the south of Madrid). It was... 

Nowadays, electricity generation technology from renewable resources, especially solar energy has been very popular; specifically off-grid systems which have the ability of decentralized electricity generation. Dish/Stirling system is one of the most efficient technologies with capability of decentralized electricity generation from solar energy. The purpose of this study is design, optimization and analysis of a 10 KW Dish/Stirling system for different working location in Iran.
A mathematical model is introduced to analyze all the heat losses in different system components including parabolic dish, cavity receiver and Stirling engine. All the calculations are done with MATLABTM... 

Combined geothermal heat pump and solar collector system is a kind of load supply system for dwellings and greenhouses that operates by relying on renewable energies. The advantage of this system over conventional systems is lower power consumption. The aim of this study is to optimize the hybrid system so that in addition to reducing energy consumption and exergy destroied of the system, economically be minimized. In fact, in this study, we are dealing with an issue that should be optimize from different aspects. firstly, thermodynamic modeling for vertical ground source heat pump is done and then by considering 11 decision variables, the system is optimized by using single-objective and... 

In a solar central system plant about 40% of energy losses occurs in the heliostat field. Furtheremore, half of the investment costs for construction of the plant is related to the heliostat field. Therefore, an optimal design of the heliostat field is necessary for reduction of levelized cost of energy in solar tower power plants. In this study, in order to optimally design the heliostat field, first energy performance of the helistat field in one year is simulated. Solar power and sun’s position at each moment of the day is determined by mathematical relations. Then, loss factors in the field are modelled and heliostat field layout is designed by an algorithm. Finally, by using PSO... 

Polymer membrane fuel cell is a rich source of renewable energy. Two problems of short life and low reliability in fuel cells are the main problems of this system. The difference in partial pressure of hydrogen and oxygen causes serious damage to the fuel cell and inefficiency of the electricity production capacity. On the other hand, the life and optimal performance of the fuel cell depends on the moisture content of the membrane because the membrane needs sufficient moisture to pass ions. Transparent fuel cells can be used to study the water in the fuel cell. With direct imaging of this type of fuel cells, the phenomenon of water creation in the fuel cell can be studied with the help of... 

The issue under discussion in this paper is to optimize the fuel consumption of the Toyota Prius hybrid car. In order to solve this problem, the ADVISOR design model used by NREL in the Matlab / Simulink environment has been used. Various parts of this model are described. The optimization performed on this issue is based on the emotional controller. This controller works by simulating learning in animals based on encouraging and punishing them. With the introduction of the controller, the model and its inclusion in the fuel consumption control and its implementation have achieved good results. In the initial state and the controller in the model, the fuel consumption was 4.9 liters per 100... 

In recent decades, renewable energy resources (especially wind power as the fastest-growing energy source) have increasingly been employed for providing electrical energy all over the world given to the rising energy demands, reduction in non-renewable fossil fuels as well as severe restrictions applied to the utilization of these fuels because of their contribution in environmental pollution, generating greenhouse gas emissions, and consequently earth warming. The main factors in the development of wind energy systems to date are the easy access to this energy source in all seasons and its cost-effectiveness compared to other counterparts. One of the key components utilized for converting... 

Today, due to increasing electricity consumption and demand, the use of conventional systems such as thermal, hydro and nuclear power plants is not enough to convert energy. Over the past century, scientists have sought to discover new technologies for exploiting different forms of energy and converting them into high-efficiency electrical energy. One of these ways is to use the phenomenon of magnetohydrodynamics (magnetic fluid dynamics) to convert thermal energy directly into electrical energy. Magnetohydrodynamics is a theoretical field that studies the dynamics of fluids with electrical conductivity. Induction magneto-hydrodynamic generators use ionized hot plasma (a quasi-neutral gas of... 

Nowadays, due to the advancement of robotic technologies and development of industrial robots, the robot manipulators are widely used for automation of various manufacturing processes, such as finishing processes. In these applications, the contact has to be made between robot end-effector and environment. Therefore, control of interaction force in the constrained manipulators is an important demand. On the other hand, due to use of gear box and belts for energy transmission in robot joints, robot manipulators have flexible joints. The vibration, generated due to the interaction force and robot joint flexibility, can deteriorate surface roughness in automated finishing processes. In order to... 

Hybrid Exoskeletons refer to simultaneous use of wearable robots and functional electrical stimulation technology. Hybrid exoskeletons have many advantages compared to the separate application of each of these technologies, such as reducing the robot’s energy consumption and the need for lighter and cheaper actuators for the robot, using humans muscle power, and reducing muscle fatigue. As a result, these robots have recently attracted a lot of interest in rehabilitation applications for patients suffering from mobility impairment.Control in hybrid exoskeletons is more complicated than control in traditional exoskeletons. Because in addition to robot and functional electrical stimulation... 

This project aims to design a smart microgrid connected to the utility grid in order to supply the demand of Energy Engineering Department at Sharif University of Technology. The electrical structure of this micro-grid is included utility grid, photovoltaic system with energy storage system and a consumer. Due to the energy storage system, an operation strategy is presented that is proportionate to the installed capacities in microgrid and based on a price basis that is determined by the micro-grid operator at the beginning of each day, in order to manage energy is provided. Micro-grid energy management is divided into two sections that the implementation of each part is depended to the... 

Hybrid electric vehicles (HEV) are proving to be one of the most promising innovations in advanced transportation systems to reduce air pollution and fossil fuel consumption. EMS is one of the most vital aspects of the HEV powertrain system. This research aims to design an optimal EMS under the condition of meeting the goals of drivability control, fuel consumption reduction, and battery charge stability. The current EMS is based on the classical rule-based method derived from fuzzy logic, which guides to the suboptimal solution in episodic driving cycles. Previous experiences in implementing Reinforcement Learning (RL) suffer from late convergence, instability in tracking the driving... 

We present here an analysis of controlling the Polymer Electrolyte Membrane Fuel Cells (PEMFCs) using the Q-learning algorithm, the most widely-known among reinforcement learning (RL) techniques. The method is to train the controller to guide and sustain the fuel cell power output in the 2.5 kW mark by way of manipulating elements of the reaction subsystem including the fuel cell current, the relative humidity, and the anode/cathode pressures. As the Q-learning algorithm need be implemented within a fuel cell simulation environment, the mathematical model known as Amphlett steady-state model of the PEM fuel cell was employed. The semi-empirical nature of this model necessitates the... 

Dish-stirling system with an efficiency of nearly 30% is the most efficient technology among solar energy technologies. This system includes four main parts; Parabolic dish, solar tracker, receiver and Stirling engine and generator. In this system, first parabolic dish concentrates sun rays on its focus. A receiver is put on the focus to receive the heat radiated from dish. This receiver transfers the heat to a Stirling engine. In Stirling engine, expansion and contraction of gas helps piston to move and finally rotational mechanical work is done. With coupling a generator and Stirling engine we can generate electricity. Also for keeping the focus of sun rays on receiver we should have sun...