Sharif Digital Repository

Among the equipment used in supermarkets, refrigeration systems should be the focus of energy efficiency initiatives; Because they are the biggest consumers of energy and refrigerant with significant maintenance costs. Fault detection and diagnosis (FDD) can provide considerable potential for energy savings as well as reduced maintenance costs. Although there have been numerous investigations of FDD for HVAC systems, there has been very little research on the application of FDD for supermarket refrigeration systems. Therefore, this thesis focuses on the application of FDD to these systems and helps to fill these research gaps. The studied system is a commercial refrigerator system on a... 

In this study, membrane distillation process was used for treatment of high salinity waters. The focus of this study is to simulate and build a setup of membrane distillation process. Since the membrane distillation process is based on the driving force of the temperature difference, the required temperature is provided by both the use of heaters and the use of solar energy. To increase the feed temperature by solar energy, a black polymer coating on the main membrane is used. The main membrane used in this process is PVDF polymer and the polymer coated on the surface is the PAN polymer. After simulating and constructing the laboratory setup, the influence of a variety of parameters on the... 

Distributed generation (DG) and its utilization have some benefits and risks for its owner and power network. From owner perspective, benefits of DG include selling energy, reducing costs related to fuel, and other economic benefits. However, there are some risk factors for the owner including risk of supplying fuel, risk of selling generated power, and other risk factors related to establishment of the DG unit. Utilizing risk-reduction tools such as signing agreements for selling power, purchasing fuel, and related economic tools are necessary for risk management of the owners of DG units. The purpose of this thesis is to investigate the economic situation of the DG units and optimize the... 

Hard disk drives are the main component of computers for permanent data storage. The security of the stored data is related closely to the air gap between the read-write head and the surface of disk. This gap which is created by the aerodynamic force between head and the disk is altered continually by lateral oscillations of disk. In the extreme condition of zero gap and contact between the protective coating layer and subsequently the magnetic material of the disk with the head, the disk will be scratched and damaged. Therefore, the active or passive control of these vibrations has a particular importance in the technology of manufacturing of hard disks. The first step in active control... 

All over the world availability of electrical power is an important matter. Electrical power is a basic requirement in each country so with increasing the demand, supply system should be adjusted.Compressed Air Energy System (CAES) stores the excessive produced energy as compressed air and will inject it to gas turbine to produce energy in peak load hours.This project aim is modeling and analyzing of CAES considering reliability. In this project some of failure mechanisms have been identified and modeled and then the performance effect on system failure have been surveyed. This project innovation is incorporating operational models with reliability to determine the best performance for... 

The advantages of using solar energy, including absence of environmental pollution, renewability, availability, ease of installation and use, and has attracted much attention of researchers. Expanding the use of solar energy in remote areas where national grid coverage is weak, makes off-grid inverter vital role clear. The swinging nature of solar energy requires the use of electrical energy storage and battery charger for optimum energy extraction in a technically and economically manner. The aim of this project is to develop a Smart Charger in Standalone Solar Inverter. Charger circuit design has been done in order to accommodate a 4kW inverter. Selected Charger topology is the... 

Increasing global final energy demand and the use of fossil fuels to meet this amount of energy demand have raised concerns about environmental impacts of fossil fuel consumption and the reduction of fossil energy reserves. Among the energy consumer sectors including industry, transport activities, agriculture, and households, the household sector is one of the most important sectors, regarding its share of total final energy consumption. Heating and cooling systems, which mainly use fossil fuels, are the biggest energy consumers in the household sector. Hence, optimal management of the heating and cooling systems can play an effective role in reducing energy costs in buildings. In this... 

Due to the energy crisis in recent years, much of which is due to excessive energy consumption in the air conditioning of buildings, many studies have been conducted from the perspective of engineering sciences on the subject of insulation and optimization of buildings. This study aims to investigate the conditions of thermal comfort from the mental and psychological perspective of human beings, which is the basis of the individual's decision to accept thermal adaptation behavior in the standard temperature range. In this study, the thermal adaptation model was designed on the theory of programmed behavior, which can explain the adaptation of individuals to the comfort temperature region.... 

Restructuring energy systems for increasing the competence and improving the efficiency has been regarded by energy policy makers. Also, the emerging of new technologies and also the district generation has increased the competence in energy industry. Planning and exploiting the energy system in a restructured environment, has basic differences with integrated systems. Models that can assess the behavior of independent players are needed to assess energy systems in a restructured space.The goal of the present study is to present a model to optimally develop the energy system in a restructured environment. The concept of energy hub was applied to model multicarrier systems. Three steps were... 

Today, financial exchanges have taken on a new form and cryptocurrencies were able to have a special place in these exchanges. Cryptocurrencies have attracted a lot of attention due to their decentralized nature. One of these cryptocurrencies is called Bitcoin and has the largest share of cryptocurrency exchanges. Due to the high volume of Bitcoin exchanges, a lot of energy is needed to supply this decentralized network to confirm transactions and extract it. In order for people in this industry to continue mining Bitcoin, they need to maintain their profitability. Therefore, choosing low consumption and profitable miners is one of the requirements of this industry. The aim of the thesis is... 

Due to the world's reliance on fossil fuels, the climate change situation has become more severe and has presented major challenges. One of the most promising growth avenues to address these issues in the medium to long term is widespread electrification based on renewable sources. However, this is only feasible if the energy infrastructure can support distributed and renewable energy sources without affecting the performance of the power grid. A grid is also necessary for energy systems in order to connect various technologies and guarantee proper integration of supply and demand for maximum efficiency. A novel idea called Energy Internet (EI) has been put forth to accomplish these goals,... 

This study focuses on the analysis and optimization of smart heating garments in office environments with the aim of improving individual thermal comfort. The primary objective of this research is to answer the question of how integrating a human body thermal model with heating garment systems can contribute to optimizing the garment and, consequently, enhancing individual thermal comfort. The thermal model used in this research is JOS-3, which simulates the thermal behavior of the human body under various environmental conditions. This model, combined with heating garment technology, allows for more precise control of body temperature. In this study, two types of smart heating garments are... 

In the past due to the lack of mechanical systems for air conditioning in the interior spaces, the buildings were designed to be able to maximize the use of natural forces such as solar and wind power. Natural ventilation is an old method of using natural forces. For example, wind tower is one of the traditional elements for using natural ventilation in the warm seasons for benefiting from wind and sun energy. In our country, Iran, in cities like Yazd, which are located in a warm and dry climate, the use of wind towers is very common and our predecessors were pioneer in this field. With the passage of time and the development of mechanical air conditioning systems, the use of natural... 

Increase in electricity demands and expansion cost of the power system as well as raising more concerns on environmental issues have led to increasing attraction towards Distributed Generation (DG) application in power systems. DG is generally defined as small generation units, ranging from several KW to several MW, that are installed on the distribution network. In Iran, the energy generated by DG units is purchased by Tavanir or distribution companies through guaranteed fixed-price purchase contract. The contract price imposes substantial effects on the cost and benefit of DG owners as well as those of the distribution company (DisCo). A logical and fair pricing model can provide more... 

Energy and environment crisis in past decades raised concerns about fossil fuels use and has accelerated renewable energy application in terms of solar electric, solar thermal and wind turbines. Due to the fluctuating nature in renewable resources, renewable electric power generation has a stochastic nature that makes it difficult to use by the electricity consumers. Energy storage plays a key role to put more control on renewable power generation.Lead-acid battery is a storage technology that is widely used in photovoltaic systems. Battery investment and maintenance costs account for a big part of photovoltaic system costs. Charging and discharging profiles of the battery has a great impact... 

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 this thesis, the problem of building energy prediction modeling is investigated using system identification method. Since system identification method has lower error and high accuracy than other methods of building energy prediction. This method was used to model the energy prediction of the building of the Faculty of Energy Engineering.In this method, the different thermal areas of the building are divided into two groups: central and surrounding areas for modeling purposes. The sunscreens are not used in the model but are added to other system inputs in the thermal areas around these two inlets.Given that it is difficult to obtain planning for the presence of persons and the use of... 

The purpose of this study was to investigate experimentally and modeling the process of gasification with supercritical water using waste motor oil. The effect of four important and influential parameters on the process, Temperature (350-450° C), Reaction time (15-45 minutes), Oil-to-Water volume ratio (0.2-0.4) and type of catalyst Consumption (Ni- NaOH- Na2CO3) was evaluated. Experimental experiments were designed and performed on the Design Expert software. The experimental results showed that the purity of hydrogen in the gas stream is more dependent on the temperature parameter and the higher purity is obtained with increasing temperature. Subsequently, as the oil concentration... 

By increasing the penetration of distributed generation (DG) technologies such as photovoltaiec, μCHP etc, power generation system is moving from a centralized network to a distributed scheme with different generation units at lower level of voltage.This trend will provide the opportunity for cosumers to make decision when and which source of energy to use, due to the owner’s objectives. Here, to investigate these aspects, we use the energy hub framework, considering different energy carrier networks, DGs and storage devices. In this thesis, we model and simulate an energy system containing three interconnected energy hubs, which serve as interface between suppliers and consummers. In an... 

One of the issues that today is considered by planners and system operators in power systems, especially the Iranian power grid, is the high variation and the lack of uniformity of load curves in different hours of the day. This has led to the use of all installed capacity of the country's production only in peak hours, and in the low and intermediate times, a large amount of installed capacity is out of the circuit, which means Unused capital. This problem is more or less seen in world power networks with high load variation curves. Also, the production of renewable energies has always been fluctuating, and the production of power control to improve this fluctuation is very important. This...