Sharif Digital Repository

The long-term storage of solar energy presents a significant challenge in satisfying energy demands. Given the frequency and magnitude of solar radiation, this abundant and free energy source can be primarily stored in liquid fuels and utilized as needed, particularly in the long-distance transportation sector. Concurrently, the absorption and utilization of CO2 emissions from energy-intensive industries represent steps towards establishing a zero-carbon cycle to mitigate emissions.This study initially presents a thermodynamic analysis of synthesis gas fuel production via the reduction and oxidation cycle of ceria in a solar reactor under isothermal cycle conditions. Under radiation, ceria... 

Focusing on fossil fuel to secure energy demand lead to big challenges. Hydrogen as alternative for fossil fuel has attracted a lot of attentions. Fuel cell with an electrochemical reaction which it’s byproducts are water and heat convert Hydrogen into electricity. High efficiency and low environmental pollution, persuade many researchers toward fuel cell commercialization. But problems such as high cost, high power oscillation and inertia, avoid fuel cell from significant development. One way to deal with these problems is using the fuel cell and battery hybrid system. In recent decade too many research has been made in utilizing this hybrid system in transportation. This project... 

The short life of Polymer Electrolyte Membrane (PEM) fuel cells is one of the critical criteria to their commercialization. A longer operation life time should be achieved to reach high reliability, low $/kWh cost and to use fuel cells as economical alternative energy systems.Therefore,diagnosing degradation mechanisms and the causes of power loss in fuel cell life time is of great importance. Operating conditions affect output power density and performance degradation. To achieve maximum power generation through fuel cell life time, a model is needed which is able to estimate power density and performance degradation simultaneously regarding to operating conditions. In present work, a... 

In this study dynamic response of Timoshenko beam and rectangular Kirchhoff plate under moving mass are investigated. Applying Hamilton’s principle, governing differential equations of beam and plate are derived considering the effect of moving mass. Afterward, a numerical-analytical solution based on eigen function expansion method for analyzing nonuniform beams and plates by means of beams’ and plates’ free vibration modes is presented and convergence of the solution is proved by proving that the governing differential equations of Timoshenko beam and Kirchhoff plates are self adjoint. Modal orthogonality circumstances are discussed due to their important role in eigen function expansion... 

Inappropriate effects of fossil fuels and conventional power generation systems on the environment have necessitated a sustainable energy system for the next decade by growing interests in renewable energy systems. The world’s most fast-growing renewable energy resource is the wind energy. The main problem of wind power is the power fluctuations at the load side caused by the variable nature of wind speed, and the main issue in case of remote locations is the long-term storage of power generated by wind turbines. Batteries can be used to store a limited amount of energy for a short time. Although new advances in this field have been achieved, most common type of batteries is hardly able to... 

The gradual exhaustion of oil and gas resources and the various problems involved in their pollution makes it necessary to promote a renewable energy system. One of the most interesting developments of standalone systems based on the utilization of hydrogen is solar hydrogen system. Central and southern Iran exhibit an excellent solar climate which makes them ideal places for solar hydrogen systems. The economy of Iran is based on oil and it has one of the largest reserves of oil and gas in the world but the reserves would not be enough to meet the domestic and export markets starting in three to four decades. Moreover, elimination of energy subsidies in Iran, will led to more tendencies to... 

In this thesis a general model for simulation of solar cooler for domestic usage is developed. The model consists of 2 main parts: thermo-dynamical and economical calculations. The thermodynamic part consists of 4 sub models: a model for calculation of incoming solar radiation, cooling load demand calculation, the refrigeration cycle and the solar cycle with heat storage.As for hourly calculation of system performance part of the model produces the hourly received radiation data based on geographical position and orientation of the receiving surface. Base on results of the cooling load calculation for a 9 m2 studying room located in western part of Tehran, 1 TBR (3.516 kW) is chosen as... 

increasing energy demand and emission of environmental pollutant as a result of using fossil fuels and increase in waste generated due to human activities resulted in considering this source as a partial substitute for fossil resources in power application . Hence in this project biomass is considered as source of energy for heat and power application. Having low quality energy is the most important difficulty for application this resource as an energy carrier, so, gasification is applied to convert this source to gas with higher quality one. Produced gas in gasification enters to a micro turbine to meet thermal and electrical demand of the Sharif energy research institute. To investigate... 

Fuel cells are a reliable technology for electrical power generation, widely regarded as a promising alternative for stationary and mobile applications. In order to supply vehicle required power, fuel cell must possess suitable transient response. In this work, a mathematical zero dimensional control-oriented model for a PEM fuel cell stack is developed. Afterwards, to increase the efficiency, four parameters including cathode air inlet flow rate, return manifold cross section area, anode hydrogen inlet flow rate and hydrogen humidity are optimized in different vehicle current demand. Also, in order to decrease water production inside the fuel cell membrane, considered parameters are... 

This current reseach concentrates on designing and evaluation of stand-alone alternative energy system which consists of a proton exchange membrane fuel cell system (PEMFC), a photovoltaic (PV) panel, a proton exchange membrane electrolyser and a hydrogen storage tank.. To establish the minimum capacity of the system components, a system sizing model is developed in MATLAB Based on meteorological and the electrical yearly demand data which are extracted from DEDM model. The accuracy of the sub models is checked by comparing the experimental measurements of the system components obtained from other literatures with model outputs. The evaluation is based on demand profile, investment costs,... 

In many previous Polymer Electrolyte Membrane Fuel Cell (PEMFC) models,the catalyst distribution in Catalyst Layer (CL) was assumed to be uniform and there are just a few models which consider variation of catalyst loading across the CL. In this research, a half-cell PEMFC cathode model is applied to investigate the effect of catalyst loading in CL plane under the land and channels of bipolar plates. In addition, the agglomerate model which has been shown to be more complete representation of the fuel cell CL is used. It is necessary to mention, in many previous PEMFC models, the catalyst layer was treated as a pseudohomogenous layer. In both models, the micro structure of CL and its effect... 

In recent years, the issue of sustainability in the energy systems has attracted the attention of energy researchers. Using fossil fuels in common energy conversion systems cause environmental pollution, declining reserves of fossil resources and increase their prices because of the scarcity of fossil resources. Therefore, achieving the goals of sustainability necessitate using high efficiency energy conversion technology. Bio-inspired energy systems are one of the main candidates to improve energy conversion systems. The main target of this study is developing an optimal multi-generation energy system model, dynamically. MFC, Septic tank and Algae culture are integrated and produced power,... 

The energy systems efficiency is a great issue confront power plants professionals. Besides using high-tech components in power plants, plant operation optimization can significantly improve energy efficiency and economic performance, as efficiency of plant components generally depends on operating conditions. In addition, system preventive maintenance can reduce plant operation and failure costs, however it is also costly when done frequently. Therefore, optimizing operating conditions and preventive maintenance intervals can minimize the expected total cost of plant due to operation, failures and preventive maintenances. In recent years, the use of optimization models to determine plant... 

In this thesis the superstructure of continuous monitoring system has been developed to help energy service companies’ network. Suggested superstructure consists of three main sections: data acquisition, data analysis and decision-making, optimizer. Historical data and data which picked up by sensors are imported in decision support tool. Input data are analyzed by technical, economical and environmental models and converted to actionable indicator for best management of the project to promote energy saving project. Because the ESCO income obtained from the energy saving project, development of analytical decision support tool will help ESCO to evaluate the procedure of the project....