Sharif Digital Repository

Ocean waves are a huge, renewable energy resource, and the potential for extracting energy from waves is high. So a lot of different systems have been designed but most of them are hydraulically and have a lot of problems and they are very complex. In this thesis, the mechanism designed is purely mechanical and very simple and innovative. It has some gears in special combination with together. The mechanism can convert any form of oscillation to rotation movement; this event has been shown in results and prototype. According to the results and discussion, Designed mechanism needs very low maintenance and has low lost. So, efficiency is between 80-95%  

One of the challenges which increasing penetration of renewable energy sources with variable generation brings is the need for more flexibility in the power system. A promising way to overcome the challenge is to have local sources of the flexibility in distribution level. To this end, we present a new model for multi-stage distribution system expansion planning which jointly considers expanding the network assets and increasing the flexibility at local level by installing conventional dispatchable distributed generator units and energy storage systems. Demand response is also considered as another source of the flexibility which can be utilized by the system operator. Since deviating from... 

With the increase of renewable energy generation in power systems, the flexibility of power systems has been challenged and the high potential of resources in active distribution systems for providing flexibility has been noticed by system operators and planners to help system flexibility. In this regard, these resources can participate in the Flexible Ramp Product market which is a new product that is defined for this purpose. In this work, the management of these resources has been modeled in an active distribution system for participating in this market by considering the network constraints, the uncertainty of renewable generation and forecasted prices of products in DA and RT markets,... 

It is possible to unload a transmission line for a while. In line restoration voltage and current of the line will have some dynamic changes. So the apparent impedance of distance relay will have dynamic changes. These changes may cause some bad results including entrance of apparent impedance to the operational zones of distance relay and even relay tripping. Consequently if relay trips, the line restoration process will stop and may not be possible.
So we want an algorithm to distinguish line restoration from short circuit condition and block the relay. This algorithm must be able to stop blocking if there is any fault in the operational zones of the relay.
In this thesis an... 

In order to improve the performance of structures against earthquake loads, engineers believe that both minimizing the rigidity and maximizing the ductility; can lead to minimization of the energy input of the structure. However, the minimized energy shall be depreciated as much as possible in different stories so that the damage to the main and Irreplaceable structural members remains as low as possible.
Steel with high strength and ductility is relatively an ideal material for this purpose; however, the ductility level of this material is much higher than that is normally in use. In order to have a better utilization of the steel ductility, RBS (Ribbed Bracing System) was invented in... 

In recent years, climate change due to greenhouse gases caused an increase in frequency and intensity of the natural disasters such as hurricanes, blizzards and floods. Moreover, it is anticipated that such events will increase in the future. As a result, power system decision makers are looking for methods to improve power system resiliency against such natural disasters with low occurrence probability and high impact. In this report, the distribution system resiliency has improved via placing remote control sectionalizing switches and micro grids formation during natural disasters. In this regard, the concept of resiliency and its characteristics along with the effect of remote control... 

In this project, polarization properties, intensity of reflected light, by one layer tissue that has specified optical properties has been investigated by means of Monte Carlo simulation. Fresnel's coefficients were considered in this simulation too. The incident beam was assumed very thin with specified wave length and linear polarization parallel to plane of incidence.This beam was radiated from origin to the tissue vertically. The layer consists of homogenous particles with defined radius. Concentration of particles was constant. 10000 photons with specified weight were launched to tissue in each simulation. The results of reflected light from tissue showed that variation of the size and... 

Surface Jet Pump (ejector) is one of the most widely used equipment in the industry, which can be used in the oil and gas industry, propulsion and refrigeration systems. One of the uses of surface jet pumps in the oil and gas industry is the use of high-pressure wells to transfar low-pressure wells. The purpose of this research is to measure the transmission feasibility of low-pressure wells using surface jet pumps and optimize surface jet pump geometry. The purpose of optimizing the geometry of the surface jet pump is to maximize the ratio of the discharge rate from the low-pressure well to the high-pressure flow (entranment ratio). One of the most common methods for optimizing the... 

Nowadays, according to environmental issues and fuel economy in internal combustion engines, the tendency to use of electrical and hybrid-electrical propulsions has become more than the past. On the other hand, still there are some problems like distance and charge time in electrical propulsions. Among them there are Hybrid-electric propulsions that have the benefits of two other propulsions. These propulsions are classified into three categories: series, parallel and series-parallel.Propulsion hybridization will change the cooling system. Internal combustion engine, electric motors, inverter and batteries operate at different temperature levels. So more than one cooling circuit with its own... 

In the recent years, there is a worldwide wave of considerable changes in power industries, including the operation of distribution networks. Deregulation, open market, alternative and local energy sources, new energy conversion technologies and other future development of electrical power systems must pursue different goals. Also growth in the demand and change in load patterns may create major bottlenecks in the delivery of electric energy. This would cause distribution system stress.Furthermore, in competitive electricity markets, operators determine the electricity price for specific intervals during a day, taking into account various economical and operational factors. Traditionally, a... 

Ultra-high temperature ceramics (UHTCs) are a class of materials that have melting points above 3000°C and include borides, carbides and nitrides of some transition metals such as ZrB2, ZrC, HfB2, HfC, HfN, TaC. These compounds are of particular interest because of the unique property combination such as high electrical and thermal conductivity, chemical inertness against molten metals or non basic slags, and good thermal shock resistance. Sintering of these compounds is very difficult due to their high melting point and utilization of sintering aids or new consolidation routes is necessary to achieve high density sintered bodies. In this research, phase evolution and kinetics of diffusion... 

Power generation stations, which are commonly called power plants, are treated as the core module of power systems and are in charge of producing power to be transmitted and distributed to the end consumers. As the beating heart of power industry, power plants need to be available and reliable all the time and so do their constituent components since the need for reliable electricity, nowadays, is ever increasingly highlighted. The reason lies in the rapid jump of population growth in one hand and the incredible amount of damages as a consequence to the power interruptions due to the power plant component outages, if happened, on the other one. So, power plants have to be kept within a... 

Vertical ground-coupled heat pumps due to using a renewable energy stored in the ground and being away from ambient temperature fluctuations have a good coefficient of performance and very low pollution. Despite these advantages, these systems have not gained a pervasive position in the field of heating/cooling systems due to their high initial cost. Despite these advantages, these systems have not gained a pervasive position among communities due to their high initial cost. In the present project, a comprehensive study has been conducted to investigate the effect of using zeotropic refrigerant mixtures on the performance of vertical ground-coupled heat pumps and reducing its initial costs.... 

Providing fresh water for domestic and agricultural purposes has become one of the most pressing issues of the present century. Due to the dependency of conventional desalination on fossil fuels, these methods are associated with carbon dioxide and other greenhouse gas emissions. Therefore, renewable energy-based desalination systems have come to the fore. This study scrutinizes the performance of the solar Humidification-Dehumidification (HDH) desalination systems with subsurface condensers. In this system, solar energy evaporates water, and subsurface condensers condense water vapor into fresh water. Therefore, this system uses two renewable solar and geothermal energy. Due to the lack of... 

The appearance of renewable sources has created a more diverse energy mix and has made it challenging for grid operators to maintain stability in energy systems. The concept of a virtual power plant is the integration of different energy sources into a single entity that is collected and controlled through a central energy management system. It enables these sources to participate in electricity markets. This research presents a framework for the participation of a virtual power plant (VPP) in day-ahead (DA), reserve, and real-time (RT) energy markets. VPPs face several uncertainties, such as wind turbine (WT) production, demand, the status of calling the reserve, and energy market prices.... 

Recently, mechanical properties of advanced materials such as nanostructured and ultra-fine materials and especially nanocomposites were studied by lots of researcher. In this study, fatigue behavior of Al-SiC nanocomposites is observed. Ultra-fine grains Al matrix nanocomposites reinforced with 50 nm diameter SiC nanoparticles were produced by milling and hot extrusion. For this purpose, pure aluminum powder was mixed with 2, 4 and 6 Vol. % of SiC nanoparticles and then milled by planetary mill. The milled powder then were degased in an Argon atmosphere furnace, cold pressed and then hot extruded. Closed die-hot forging was used with about 18.8% reduction in cross section in order to... 

As a cost-effective and reliable alternative to supply remote areas, standalone Hybrid Energy Systems (HES) are recently under investigation to address various concerns associated with technical, financial and environmental issues. HESs are composed of renewable resources, fossil fuel generators, storage devices and power electronic converters, which are able to supply electrical and thermal loads. HESs have advantages of both renewable and fossil fuel technologies. HESs not only decrease the fuel consumption and maintenance cost of the diesel generator, but also reduce the effects of unpredictable and costly nature of renewable energy resources. Standalone hybrid energy systems should... 

Fundamental changes that has taken place in the restructured electricity industry require new methods to maintain the reliability of power system in the most possible economic way. Besides, power network maintenance processes has undeniable significance in promoting the desired level of reliability. Maintenance and repairs of electricity industry in generation units and power plants are more important than other parts of the power grid, because this part of the electric power infrastructure, compared to the other parts of the network, composes of more expensive equipments. Moreover, failures occurring in any of these parts cause a sharp decline in production leading to economic losses. Among... 

Depletion of the fossil fuel resources along with the environmental concerns have led to a significant growth in utilization of Renewable Energy Resources (RERs). Among different kinds of RERs, wind energy due to maturity of its associated conversion technologies and also its widespread presence in different regions has experienced a more rapid usage in generation sector of power systems. Despite numerous benefits of this environmentally-friendly energy, uncontrollability and uncertainty in output power of wind turbines has resulted in many technical issues for operators of power systems. However, it has been shown that the presence of various storage system technologies can alleviate these... 

Transmission expansion planning is an important part of power system planning that it task is to determine the optimal structure of transmission network based on load growth and to consider the future plan of system generation for a specified time period. The development of generation plans based on renewable resources, cost and time-consuming transmission expansion plans have caused that transmission planning to become a fundamental challenge. Therefore, in recent year’s decision makers of power systems are following the alternative ways of transmission expansion planning with lower cost and economic appropriate justification. Using of energy storage systems have cause to a delay on...