Doctoral Dissertations (FEAS)

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Design synthesis of articulated heavy vehicles with active trailer steering systems
(2010-04-01) Islam, Md. Manjurul; He, Yuping
A new design synthesis method for articulated heavy vehicles (AHVs) with an active trailer steering (ATS) system is examined and evaluated. Due to their heavy weights, large sizes, and complex configurations, AHVs have poor maneuverability at low speeds, and low lateral stability at high speeds. Various passive trailer steering and ATS systems have been developed for improving the low-speed maneuverability. However, they often have detrimental effects on the high-speed stability. To date, no systematic design synthesis method has been developed to coordinate the opposing design goals of AHVs. In this thesis, a new automated design synthesis approach, called a Single Design Loop (SDL) method, is proposed and investigated. The SDL method has the following distinguished features: 1) the optimal active design variables of ATS systems and the optimal passive vehicle design variables are searched in a single design loop; 2) in the design process, to evaluate the vehicle performance measures, a driver model is developed and it „drives‟ the vehicle model based on the well-defined testing specifications; and 3) the ATS controller derived from this method has two operational modes: one for improving the lateral stability at high speeds and the other for enhancing path-following at low speeds. To demonstrate the effectiveness of the new SDL method, it is applied to the design of an ATS system for an AHV with a tractor/full-trailer. In comparison to a conventional design approach, the SDL method can search through solutions in a much larger design space, and consequently it provides a more comprehensive set of optimal designs..
Investigation of sustainable hydrogen production from steam biomass gasification
(2010-12-01) Abuadala, Abdussalam Goma; Dincer, Ibrahim
Hydrogen is a by-product of the gasification process and it is environmentally friendly with respect to pollution and emission issues when it is derived from a CO2-neutral resource such as biomass. It is an energy carrier fuel and has flexibility to convert efficiently to other energy forms to be used in different energy applications like fuel cells. The proposed research presents literature on previous gasification studies regarding hydrogen production from biomass and updates the obtained results. The main objectives of the thesis are: a) to study hydrogen production via steam biomass (sawdust) gasification; b) to evaluate the produced hydrogen by performing comprehensive analysis by using thermodynamic, exergoeconomic and optimization analyses. Despite details specific to the gasifier, in general, there is a special need to theoretically address the gasifier that gasifies biomass to produce hydrogen. This further study of gasification aspects presents a comprehensive performance assessment through energy and exergy analyses, provides results of the optimization studies on minimizing hydrogen production costs, and provides a thermo-economic analysis for the proposed systems (Systems I, II and III). This thesis also includes the results from the performed study that aims to investigate theoretical hydrogen production from biomass (sawdust) via gasification technology. Results from the performed parametric study show that the gasification ratio increases from 70 to 107 gH2 per kg of sawdust. In the gasification temperature studied, system II has the highest energy efficiency that considers electricity production where it increases from 72 % to 82 % and has the lowest energy efficiency that considers hydrogen yield where it increases from 45 % to 55 %. Also, it has the lowest hydrogen cost of 0.103 $/kW-h. The optimization results show that the optimum gasification temperatures for System I, System II and System III are 1139 K, 1245 K and 1205 K, respectively.
Development of a new hybrid photochemical/electrocatalytic water splitting reactor for hydrogen production: design, analysis and experiments
(2012-01-01) Baniasadi, Ehsan; Dincer, Ibrahim; Naterer, Greg F.
Solar-driven water splitting combines several attractive features for sustainable energy utilization. The conversion of solar energy to a type of storable energy has crucial importance. An alternative method to hydrogen production by solar energy without consumption of additional reactants is a hybrid system which combines photochemical and electro-catalytic reactions. The originality of this research lies in the engineering development of a novel photo-catalytic water splitting reactor for sustainable hydrogen production, and verification of new methods to enhance system efficiency. The scope of this thesis is to present a thorough understanding of complete photocatalytic water splitting system performance under realistic working conditions. In this dissertation, an experimental apparatus for hydrogen and oxygen production is designed and built at UOIT to simulate processes encountered in photo-catalytic and electro-catalytic water splitting systems. The hybridization of this system is investigated, and scale-up analysis is performed based on experimental data using a systematic methodology. The hydrogen production rate of approximately 0.6 mmol h-1 corresponds to a quantum efficiency of 75% is measured through illumination of zinc sulfide suspensions in a dual-cell reactor. Utilization of ZnS and CdS photo-catalysts to simultaneously enhance quantum yield and exergy efficiency is performed. The production rate is increased by almost 30% as compared with ZnS performance. In the next step, an oxygen production reactor is experimentally investigated to simulate processes encountered in electro-catalytic water splitting systems for hydrogen production. In this research, the effects of ohmic, concentration and activation losses on the efficiency of hydrogen production by water electrolysis are experimentally investigated. The electrochemical performance of the system is examined by controlling the current density, temperature, space, height, and electrolyte concentration. The experimental results show that there exists an optimum working condition of water electro-catalysis at each current density, which is determined by the controlling parameters. A predictive mathematical model based on experimental data is developed, and the optimized working conditions are determined. The oxygen evolving half-cell is also analyzed for different complete systems including photo-catalytic and electro-catalytic water splitting. An electrochemical model is developed to evaluate the over-potential losses in the oxygen evolving reaction and the effects of key parameters are analyzed. The transient diffusion of hydroxide ions through the membrane and bulk electrolyte is modeled and simulated for improved system operation. In addition, a new seawater electrolysis technique to produce hydrogen is developed and analyzed from energy and exergy points of view. In this regard, the anolyte feed after oxygen evolution to the cathode compartment for hydrogen production is examined. An inexpensive and efficient molybdenum-oxo catalyst with a turn-over frequency of 1,200 is examined for the hydrogen evolving reaction. The electrolyte flow rate and current density are parametrically studied to determine the effects on both bulk and surface precipitate formation. The mixing electrolyte volume and electrolyte flow rate are found to be significant parameters as they affect cathodic precipitation. Furthermore, a new hybrid system for hydrogen production via solar energy is developed and analyzed. In order to decompose water into hydrogen and oxygen without the net consumption of additional reactants, a steady stream of reacting materials must be maintained in consecutive reaction processes, to avoid reactant replenishment or additional energy input to facilitate the reaction. Supramolecular complexes [{(bpy)2Ru(dpp)}2RhBr2](PF6)5 are employed as the photo-catalysts, and an external electric power supply is used to enhance the photochemical reaction. A light-driven proton pump is used to increase the photochemical efficiency of both O2 and H2 production reactions. The maximum energy conversion of the system can be improved up to 14% by incorporating design modification that yields a corresponding 25% improvement in exergy efficiency. Moreover, a photocatalytic water splitting system is designed and analyzed for continuous operation on a large pilot-plant scale. A Compound Parabolic Concentrator (CPC) is presented for the sunlight-driven hydrogen production system. Energy and exergy analyses and related parametric studies are performed, and the effect of various parameters are analyzed, including catalyst concentration, flow velocity, light intensity, reactor surface absorptivity, and ambient temperature. Two methods of photo-catalytic water splitting and solar methanol steam reforming are investigated as two potential solar-based methods of catalytic hydrogen production. The exergy efficiency, exergy destruction, environmental impact and sustainability index are investigated for these systems, as well as exergoenvironmental analyses. The results show that a trade-off exists in terms of exergy efficiency improvement and CO2 reduction of the photo catalytic hydrogen production system. The exergo-economic study reveals the maximum hydrogen exergy price of 2.12, 0.85, and 0.47 $ kg-1 for production capacities of 1, 100, and 2000 ton day-1, respectively. These results are well below the DOE 2012 target and confirm the viability of this technology.
Exergy and exergoeconomic analyses and optimization of thermal management systems in electric and hybrid electric vehicles
(2012-01-01) Hamut, Halil S.; Dincer, Ibrahim; Naterer, Greg F.
With the recent improvements in battery technologies, in terms of energy density, cost and size, the electric (EV) and hybrid electric vehicle (HEV) technologies have shown that they can compete with conventional vehicles in many areas. Although EVs and HEVs offer potential solutions for many key issues related to conventional vehicles, they still face considerable challenges that prevent the widespread commercialization of these technologies, such as thermal management of batteries and electrification. In this PhD thesis, a liquid thermal management system (TMS) for hybrid electric vehicles is investigated and evaluated against alternative thermal management systems, and optimal parameters are selected to maximize the system efficiency. In order to achieve this goal, a model of the liquid thermal management system is established to determine the irreversibilities and second-law efficiencies associated with the overall system and its components. Furthermore, the effects of different configurations, refrigerants and operating conditions are analyzed with respect to conventional exergy analyses. In addition, advanced exergy analyses are also conducted in order to better identify critical relationships between the TMS components and determine where the system improvement efforts should be concentrated. Moreover, investment costs are calculated and cost formation of the system is developed in order to evaluate the TMS with respect to exergoeconomic principles and provide corresponding recommendations. Environmental impact correlations are developed, along with a cradle-to-grave life cycle assessment (LCA), to highlight components causing significant environmental impact, and to suggest trends and possibilities for improvement based on the exergoenvironmental variables. Finally, the TMS is optimized using multi-objective evolutionary algorithm which considers exergetic and exergoeconomic as well as exergetic and exergoenvironmental objectives simultaneously with respect to the decision variables and constraints. Based on the conducted research for the studied system under the baseline conditions, the exergy efficiency, total cost rate and environmental impact rate are determined to be 0.29, ¢28/h and 77.3 mPts/h, respectively. The exergy destruction associated with each component is split into endogenous/exogenous and avoidable/unavoidable parts, where the exogenous exergy destruction is determined to be relatively small but significant portion of the total exergy destruction in each component (up to 40%), indicating a moderate level of interdependencies among the components of the TMS. Furthermore, it is determined that up to 70% of the exergy destruction calculated within the components could potentially be avoided. According to the analyses, electric battery is determined to have the highest exergoeconomic and exergoenvironmental importance in the system, with cost rate of ¢3.5/h and environmental impact value of 37.72 mPts/h, due to the high production cost of lithium ion batteries and the use of copper and gold in the battery pack. From an exergoeconomic viewpoint, it is determined that the investment costs of the condenser and evaporator should be reduced to improve the costeffectiveness of the system. On the other hand, from an exergoenvironmental viewpoint, all the component efficiencies (except for the battery) should be improved in order to reduce the total environmental impact even if it increases the environmental impact during production of the components. In addition, it is determined that the coolant pump and the thermal expansion valve before the chiller are relatively insignificant from exergoeconomic and exergoenvironmental perspectives. Subsequently, objective functions are defined and decision variables are selected, along with their respective system constraints, in order to conduct single and multiple objective optimizations for the system. Based on the single objective optimizations, it is determined that the exergy efficiency could be increased by up to 27% using exergy-based optimization, the cost can be reduced by up to 10% using cost-based optimization and the environmental impact can be reduced by up to 19% using environmental impact-based optimization, at the expense of the nonoptimized objectives. Moreover, multi-objective optimizations are conducted in order to provide the respective Pareto optimal curve for the system and to identify the necessary trade-offs within the optimized objectives. Based on the exergoeconomic optimization, it is concluded that 14% higher exergy efficiency and 5% lower cost can be achieved, compared to baseline parameters at an expense of 14% increase in the environmental impact. Furthermore, based on the exergoenvironmental optimization, 13% higher exergy efficiency and 5% lower environmental impact can be achieved at the expense of 27% increase in the total cost.
Kinetics and transport phenomena in the chemical decomposition of copper oxychloride in the thermochemical Cu-CI Cycle
(2012-04-01) Marin, Gabriel D.; Naterer, Greg F.; Gabriel, Kamiel
The thermochemical copper-chlorine (Cu-Cl) cycle for hydrogen production includes three chemical reactions of hydrolysis, decomposition and electrolysis. The decomposition of copper oxychloride establishes the high-temperature limit of the cycle. Between 430 and 530 oC, copper oxychloride (Cu2OCl2) decomposes to produce a molten salt of copper (I) chloride (CuCl) and oxygen gas. The conditions that yield equilibrium at high conversion rates are not well understood. Also, the impact of feed streams containing by-products of incomplete reactions in an integrated thermochemical cycle of hydrogen production are also not well understood. In an integrated cycle, the hydrolysis reaction where CuCl2 reacts with steam to produce solid copper oxychloride precedes the decomposition reaction. Undesirable chlorine may be released as a result of CuCl2 decomposition and mass imbalance of the overall cycle and additional energy requirements to separate chlorine gas from the oxygen gas stream. In this thesis, a new phase change predictive model is developed and compared to the reaction rate kinetics in order to better understand the nature of resistances. A Stefan boundary condition is used in a new particle model to track the position of the moving solid-liquid interface as the solid particle decomposes under the influence of heat transfer at the surface. Results of conversion of CuO*CuCl2 from both a thermogravimetric (TGA) microbalance and a laboratory scale batch reactor experiments are analyzed and the rate of endothermic reaction determined. A second particle model identifies parameters that impact the transient chemical decomposition of solid particles embedded in the bulk fluid consisting of molten and gaseous phases at high temperature and low Reynolds number. The mass, energy, momentum and chemical reaction equations are solved for a particle suddenly immersed in a viscous continuum. Numerical solutions are developed and the results are validated with experimental data of small samples of chemical decomposition of copper oxychloride (CuO*CuCl2). This thesis provides new experimental and theoretical reference for the scale-up of a CuO*CuCl2 decomposition reactor with consideration of the impact on the yield of the thermochemical copper-chlorine cycle for the generation of hydrogen.
Analytical modeling and simulation of metal cutting forces for engineering alloys
(2012-04-01) Pang, Lei; Kishawy, Hossam A.
In the current research, an analytical chip formation model and the methodology to determine material flow data have been developed. The efforts have been made to address work hardening and thermal softening effects and allow the material to flow continuously through an opened-up deformation zone. Oxley's analysis of machining is extended to the application of various engineering materials. The basic model is extended to the simulation of end milling process and validated by comparing the predictions with experimental data for AISI1045 steel and three other materials (AL-6061, AL7075 and Ti-6Al-4V) from open literatures. The thorough boundary conditions of the velocity field in the primary shear zone are further identified and analyzed. Based on the detailed analysis on the boundary conditions of the velocity and shear strain rate fields, the thick “equidistant parallel-sided” shear zone model was revisited. A more realistic nonlinear shear strain rate distribution has been proposed under the frame of non-equidistant primary shear zone configuration, so that all the boundary conditions can be satisfied. Based on the developed model, inverse analysis in conjugation of genetic algorithm based searching scheme is developed to identify material flow stress data under the condition of metal cutting. ii On the chip-tool interface, The chip-tool interface is assumed to consist of the secondary shear zone and elastic friction zone(i.e. sticking zone and sliding zone). The normal stress distribution over the entire contact length is represented by a power law equation, in which the exponent is determined based on the force and moment equilibrium. The shear stress distribution for the entire contact length is assumed to be independent of the normal stress. The shear stress is assumed to be constant for the plastic contact region and exponentially distributed over the elastic contact region, with the maximum equal to the shear flow stress at the end of sticking zone and zero at the end of total contact. The total contact length is derived as a function governed by the shape of normal stress distribution. The length of the sticking zone is determined as the distance from the cutting edge to the location where the local coefficient of friction reaches a critical value that initiates the bulk yield of the chip. Considering the shape of the secondary shear zone, the length of the sticking zone can also be determined by angle relations. The maximum thickness of the secondary shear zone is determined by the equality of the sticking lengths calculated by two means. With an arbitrary input of the sliding friction coefficient, various processing parameters as well as contact stress distributions during orthogonal metal cutting can be obtained.
Fluid transport and entropy production in electrochemical and microchannel droplet flows
(2012-04-01) Odukoya, Adedoyin; Naterer, Greg F.
The growth of energy demand in the world requires addressing the increasing power requirements of industrial and residential consumers. Optimizing the design of new and existing large power producing systems can efficiently increase energy supply to meet the growing demand. Hydrogen as an energy carrier is a promising sustainable way to meet the growing energy demand, while protecting the environment. This thesis investigates the efficient production of hydrogen from the electrolysis of copper chloride, by predicting entropy production as a result of diffusive mass transfer. Also, this thesis investigates the possibility of producing electrical energy from waste heat produced by industrial or other sources. The thermocapillary motion of fluid droplet in a closed rectangular microchannel is used to generate electrical energy from waste heat in a piezoelectric membrane by inducing mechanical deformation as a result of the droplet motion. Modeling, fabrication, and experimental measurement of a micro heat engine (MHE) are investigated in this study. Analytical and experimental results are reported for both circular and rectangular microchannels. A novel fabrication technique using lead zirconate titanate (PZT) as substrate in microfluidic application is presented in this study. This thesis develops a predictive model of the entropy production due to thermal and fluid irreversibilities in the microchannel. Thermocapillary pressure and friction forces are modelled within the droplet, as well as surface tension hysteresis during start-up of the droplet motion. A new analytical model is presented to predict the effect of transient velocity on the voltage production in the MHE. In order to predict the effect of the applied stress on voltage, the different layers of deposition are considered for thin film laminates. The highest efficiency of the system from simulated taking into iv account the electromechanical coupling factor is about 1.6% with a maximum voltage of 1.25mV for the range of displacement considered in this study. In addition, new experimental and analytical results are presented for evaporation and de-pinning of deionised water and toluene droplets in rectangular microchannels fabricated from Su-8 2025 and 2075.
Multi-dimensional modeling of transient transport phenomena in molten carbonate fuel cells
(2012-06-01) Yousef Ramandi, Masoud; Dincer, Ibrahim; Berg, Peter
Molten carbonate fuel cells (MCFCs) have become an attractive emerging technology for stationary co-generation of heat and power. From a technical perspective, dynamic operation has a significant effect on the fuel cell life cycle and, hence, economic viability of the device. The scope of this thesis is to present an improved understanding of the system behaviour at transient operation that can be used to design a more robust control system in order to overcome the cost and the operating lifetime issues. Hence, a comprehensive multi-component multidimensional transient mathematical model is developed based on the conservation laws of mass, momentum, species, energy and electric charges coupled through the reaction kinetics. In essence, this model is a set of partial differential equations that are discretized and solved using the finite-volume based commercial software, ANSYS FLUENT 12.0.1. The model is validated with two sets of experimental results, available in open literature, and good agreements are obtained. The validated model is further engaged in an extensive study. First, the MCFC behaviour at high current densities or oxidant utilization, when the mass transfer becomes dominant, is investigated using peroxide and superoxide reaction mechanisms. In brief, both mechanisms predicted the linear region of the polarization curve accurately. However, none of these mechanisms showed a downward bent in the polarization curve. A positive exponent for the carbon-dioxide mole fraction is probably essential in obtaining the downward bent (“knee”) at high current densities which is in contrast to what has been reported in the literature to date. Next, a sinusoidal impedance approach is used to examine the dynamic response of the unit cell to inlet perturbations at various impedance frequencies. This analysis is further used to determine the phase shifts and time scales of the major dynamic processes within the fuel cell. Furthermore, numerical simulation is utilized in order to investigate the underlying electrochemical and transport phenomena without performing costly experiments. Results showed that the electrochemical reactions and the charge transport process occur under a millisecond. The mass transport process showed a comparatively larger time scale. The energy transport process is the slowest process in the cell and takes about an hour to reach its steady state condition. Furthermore, the developed mathematical model is utilized as a predictive tool to provide a three-dimensional demonstration of the transient physical and chemical processes at system startiv up. The local distribution of field variables and quantities are presented. The results show that increasing the electrode thickness provides a higher reaction rate, but may lead to larger ohmic loss which is not desirable. The reversible heat generation and consumption mechanisms of the cathode and anode are dominant in the first 10 s while the heat conduction from the solid materials to the gas phase is not considerable. The activation and ohmic heating have the same impact within the anode and cathode because of their similar electric conductivity and voltage loss. Increasing the thermal conductivity of the cathode material will facilitate the process of heat transport throughout the cell. This can also be accomplished by lowering the effects of heat conduction by means of a cathode material with a smaller thickness. In addition, a thermodynamic model is utilized to examine energy efficiency, exergy efficiency and entropy generation of a MCFC. By changing the operating temperature from 883 K to 963 K, the energy efficiency of the unit cell varies from 42.8 % to 50.5 % while the exergy efficiency remains in the range of 26.8% to 36.3%. Both efficiencies initially rise at lower current densities up to the point that they attain their maximum values and ultimately decrease with the increase of current density. With the increase of pressure, both energy and exergy efficiencies of the cell increase. An increase in this anode/cathode flow ratio lessens the energy and exergy efficiencies of the unit cell. Higher operating pressure and temperature decrease the unit cell entropy generation.
Thermal management of the copper-chlorine cycle for hydrogen production: analytical and experimental investigation of heat recovery from molten salt
(2012-08-01) Ghandehariun, Samane; Naterer, Greg; Rosen, Marc
Hydrogen is known as a clean energy carrier which has the potential to play a major role in addressing the climate change and global warming, and thermochemical water splitting via the copper-chlorine cycle is a promising method of hydrogen production. In this research, thermal management of the copper-chlorine cycle for hydrogen production is investigated by performing analytical and experimental analyses of selected heat recovery options. First, the heat requirement of the copper-chlorine cycle is estimated. The pinch analysis is used to determine the maximum recoverable heat within the cycle, and where in the cycle the recovered heat can be used efficiently. It is shown that a major part of the potential heat recovery can be achieved by cooling and solidifying molten copper(I) chloride exiting one step in the cycle: the oxygen reactor. Heat transfer from molten CuCl can be carried out through direct contact or indirect contact methods. Predictive analytical models are developed to analyze a direct contact heat recovery process (i.e. a spray column) and an indirect contact heat recovery process (i.e. a double-pipe heat exchanger). Characteristics of a spray column, in which recovered heat from molten CuCl is used to produce superheated steam, are presented. Decreasing the droplet size may increase the heat transfer rate from the droplet, and hence decreases the required height of the heat exchanger. For a droplet of 1 mm, the height of the heat exchanger is predicted to be about 7 m. The effect of hydrogen production on the heat exchanger diameter was also shown. For a hydrogen production rate of 1000 kg/day, the diameter of the heat exchanger is about 3 m for a droplet size of 1 mm and 2.2 m for a droplet size of 2 mm. The results for axial growth of the solid layer and variations of the coolant temperature and wall temperature of a double-pipe heat exchanger are also presented. It is shown that reducing the inner tube diameter will increase the heat exchanger length and increase the outlet temperature of air significantly. It is shown that the air temperature increases to 190oC in a heat exchanger with a length of 15 cm and inner tube radius of 10 cm. The length of a heat exchanger with the inner tube radius of 12 cm is predicted to be about 53 cm. The outlet temperature of air is about 380oC in this case. The length of a heat exchanger with an inner tube diameter of 24 cm is predicted to be about 53 cm and 91 cm for coolant flow rates of 3 g/s and 4 g/s, respectively. Increasing the mass flow rate of air will increase the total heat flux from the molten salt by increasing the length of the heat exchanger. Experimental studies are performed to validate the proposed methods and to further investigate their feasibility. The hazards involving copper(I) chloride are also investigated, as well as corresponding hazard reduction options. Using the reactant Cu2OCl2 in the oxygen production step to absorb CuCl vapor is the most preferable option compared to the alternatives, which include absorbing CuCl vapor with water or CuCl2 and building additional structures inside the oxygen production reactor.
Multiphase flow and chemical reactor thermodynamics for hydrolysis and thermochemical production
(2012-08-01) Pope, Kevin; Naterer, Greg F.
Current techniques of hydrogen production (primarily reformation of fossil fuels) are unsustainable, releasing CO2 into the atmosphere, as well as consuming limited reserves of fossil fuels. The copper-chlorine cycle is a promising thermochemical process which can cost-effectively produce hydrogen with less environmental impact. In this thesis, new predictive formulations and experimental data are presented to improve the conversion extent and reaction rates of the hydrolysis reactor in the Cu-Cl cycle. This reactor has critical implications for the design, operation, and efficiency of the Cu-Cl cycle and hydrogen production. The relatively high temperature needed to drive the reaction requires a significant input of thermal energy. This thesis focuses on methods and analysis to reduce the unreacted steam in the hydrolysis reactor, in order to reduce the thermal energy input and improve the cycle’s thermal efficiency. A key outcome from this thesis is the experimental verification of reducing the steam to copper chloride ratio from 16:1 (past studies) to about 3:1. The results of this thesis provide key new data to design a more efficient hydrolysis reactor that can be effectively integrated within the Cu-Cl cycle.
Design, analysis and experimental investigation of Cu-Cl based integrated systems
(2013-01-01) Ratlamwala, Tahir Abdul Hussain; Dincer, Ibrahim
Burning fossil fuels for power generation results in emissions of greenhouse gases such as carbon dioxide (CO2) and air pollutants such as nitrogen oxides (NOx) and sulfur oxides (SOx), which are harmful to living creatures and the natural environment. Due to the negative effects of using fossil fuels, significant research is being carried out in the area of alternative energy carriers such as hydrogen, which can replace fossil fuels in the future. Hydrogen can be produced in a relatively environmentally friendly manner by using the copper-chlorine (Cu-Cl) thermochemical water splitting cycle (TWSC) due to its minimal reliance on fossil fuels, relatively lower operating temperature requirement and better overall efficiency as compared to other TWSCs. The electrolysis step of the Cu-Cl cycle is one of the most important steps, since it produces the hydrogen gas. The dependence of the Cu-Cl cycle on the electricity grid to run the electrolysis step impacts the overall environmental sustainability of the process. The aim of this study is to perform experimental investigations of the hybrid photocatalytic hydrogen production reactor for the Cu-Cl cycle. The electrochemical, energy, exergy and exergoeconomic analyses of the hybrid reactors are carried out to observe the effects of variation in different operating parameters on the performance of the system. The comparative energy and exergy analyses of two solar-based integrated systems are also conducted to show how the performance of integrated systems can be improved by recovering reflected solar light intensity in the photocatalytic hydrogen production reactor. The results obtained from the photo-electrochemical experimental study show that an increase in the voltage, solar light intensity, concentration of CuCl and concentration of ZnS increases the hydrogen production rate. The experimental results also show that the amount of voltage generated by inducing solar light intensity on titanium dioxide increases with an increase in the concentration of the titanium dioxide. The results based on electrochemical modeling of the hybrid reactor show that an increase in current density results in a higher voltage requirement by the hybrid photocatalytic reactor. The experimental hydrogen production rate and cost of hydrogen production is observed to increase from 1.28 to 1.47 L/s and 3.28 to 3.36 C$/kg, respectively, with a rise in reactor temperature. Energy and exergy analyses of the solar-based integrated systems show that the rates of hydrogen production by systems 1 and 2 increase from 126.9 to 289.4 L/s and 154.1 to 343.9 L/s, respectively, with a rise in solar light intensity. The exergy efficiencies of systems 1 and 2 increase from 47.98 to 50.82% and 56.87 to 59.64%, respectively, with a rise in ambient temperature.
Experimental design, analysis and improvement of a Marnoch Heat Engine with heat recovery.
(2013-01-01) Saneipoor, Pooya; Naterer, Greg F.; Dincer, Ibrahim
This research examines the prototyping of a Marnoch Heat Engine (MHE) and conducts thermodynamic and heat transfer analyses of this heat engine with a waste heat recovery system. The heat source for the MHE can be low grade heat (about 365 K). During cold seasons an ambient temperature can be adequate for the heat sink to operate the heat engine. When the ambient temperature is high, the system can be connected to a dry cooler to achieve higher efficiency levels. A water/glycol mixture transfers heat from the heat source into the hot heat exchangers and removes the heat from the cold heat exchangers. Compressed dry air is used as the working fluid in the heat engine. This thesis develops prototyping of the MHE with two different mechanical configurations of the transmission system. Furthermore, thermodynamic analysis is carried out to calculate the heat engine power output, as well as energy and exergy efficiencies under various operational conditions. A heat transfer model is developed to predict the transient temperature behaviours of the heat exchangers for different flow regimes and temperatures. The results from the model are validated against the available data in the open literature and then compared with experimental results from the present MHE prototype. The average difference between the heat transfer model and the measured data from the MHE prototype is about 10 K. Life cycle assessment is applied to identify CO2 emissions of the MHE during the manufacturing and maintenance processes. The heat source and heat sink temperatures for this case study are assumed to be 281 K and 370 K, respectively. In a developed case study, it is found that the amount of CO2 released as a result of manufacturing and maintenance of the system is about 52 g CO2-quivalent per kWh. Results from the exergoeconomic analysis are used to determine the required changes in MHE design parameters for the purpose of improving the cost effectiveness of the overall system. Energy and exergy efficiencies of the MHE are evaluated under various operating conditions. It is shown that the maximum exergy efficiency of the MHE reaches, at most, 18% of the Carnot efficiency. The maximum value of the exergoeconomic factor is found to be 0.45, and that the heat exchangers are the major sources of exergy destruction within the system. To improve the system performance, the major sources of heat and mechanical losses are identified and addressed. This research proposes four new heat exchanger designs that can be applied to future designs of the MHE units. The strength of the effect of each proposed design on the system performance is also discussed.
Investigation of energy storage options for thermal management in hybrid electric vehicles
(2013-01-01) Javani, Nader; Dincer, Ibrahim; Naterer, Greg F.
Electric and hybrid electric vehicles could have a significant role in the sustainable transportation. Higher power density lead to extra heat generation and thermal runaway in the Li-ion cells. Therefore, a successful thermal management system is required to prevent temperature increase and non-uninform distribution in the battery pack. In the current study, integration of a phase change material (PCM) in the cell and sub-module levels is investigated by using a finite volume based software. The first considered scenario is to use the phase change material in different thicknesses around the Li-ion cells. The simulation results show that the maximum temperature in the cell and temperature excursion in the sub-module are reduced when phase change material is applied. In addition, for the case when PCM is introduced in between the cells through a porous foam, up to a 7.7 K temperature decrease is observed in the sub-module compared with the case without phase change material. The second scenario is to design and optimize a shell and tube latent heat energy storage system to integrate with the active cooling system of the vehicle to decrease the cooling load. Energy and exergy analyses have also been conducted for a new cooling system of the vehicle, in which the passive latent heat storage thermal management system is integrated with the active refrigeration cycle. The overall exergy efficiency of the system with PCM presence is 31%. In addition, results obtained by sing EES program show that an increase in PCM mass fraction results in an increased exergy efficiency of the system which is mainly due to the decrease of compressor work. In order to improve the thermal conductivity of n-octadecane as the selected phase change material, carbon nano-tubes and graphene nano-platelets are introduced with different mass concentrations. Morphological structure of pure and technical grade PCMs mixed with nano-particles is studied through the transmission and reflection optic microscopic methods. Results show that 6% concentration of carbon nano-tube has better effect in increasing the effective thermal conductivity of the PCM. Furthermore, partial agglomeration of the nanoparticles is observed in the experiments.
Intelligent fault diagnosis of gearboxes and its applications on wind turbines
(2013-02-01) Hussain, Sajid; Gabbar, Hossam A.
The development of condition monitoring and fault diagnosis systems for wind turbines has received considerable attention in recent years. With wind playing an increasing part in Canada’s electricity demand from renewable resources, installations of new wind turbines are experiencing significant growth in the region. Hence, there is a need for efficient condition monitoring and fault diagnosis systems for wind turbines. Gearbox, as one of the highest risk elements in wind turbines, is responsible for smooth operation of wind turbines. Moreover, the availability of the whole system depends on the serviceability of the gearbox. This work presents signal processing and soft computing techniques to increase the detection and diagnosis capabilities of wind turbine gearbox monitoring systems based on vibration signal analysis. Although various vibration based fault detection and diagnosis techniques for gearboxes exist in the literature, it is still a difficult task especially because of huge background noise and a large solution search space in real world applications. The objective of this work is to develop a novel, intelligent system for reliable and real time monitoring of wind turbine gearboxes. The developed system incorporates three major processes that include detecting the faults, extracting the features, and making the decisions. The fault detection process uses intelligent filtering techniques to extract faulty information buried in huge background noise. The feature extraction process extracts fault-sensitive and vibration based transient features that best describe the health of the gearboxes. The decision making module implements probabilistic decision theory based on Bayesian inference. This module also devises an intelligent decision theory based on fuzzy logic and fault semantic network. Experimental data from a gearbox test rig and real world data from wind turbines are used to verify the viability, reliability, and robustness of the methods developed in this thesis. The experimental test rig operates at various speeds and allows the implementation of different faults in gearboxes such as gear tooth crack, tooth breakage, bearing faults, iv and shaft misalignment. The application of hybrid conventional and evolutionary optimization techniques to enhance the performance of the existing filtering and fault detection methods in this domain is demonstrated. Efforts have been made to decrease the processing time in the fault detection process and to make it suitable for the real world applications. As compared to classic evolutionary optimization framework, considerable improvement in speed has been achieved with no degradation in the quality of results. The novel features extraction methods developed in this thesis recognize the different faulty signatures in the vibration signals and estimate their severity under different operating conditions. Finally, this work also demonstrates the application of intelligent decision support methods for fault diagnosis in gearboxes.
Model based simulation of broaching operation: cutting mechanics, surface integrity, and process optimization
(2013-04-01) Hosseini, Sayyed Ali; Kishawy, Hossam A.
Machining operations are widely used to produce parts with different shapes and complicated profiles. As a machining operation, broaching is commonly used for the machining of a broad range of complex internal and external profiles either circular or non-circular such as holes, keyways, guide ways, and slots on turbine discs having fir-tree shape. Broaching is performed by pushing or pulling a tapered tool through the workpiece to remove the unwanted material and produce the required profile. Broaching is also acknowledged because of its high productivity and attainable surface quality in comparison to the other machining processes. The objective of this thesis is to simulate the broaching operation and use the results to present a methodology for optimum design of the broaching tools. In the course of the presented thesis, a new B-spline based geometric model is developed for broaching cutting edges followed by model validation using 3D ACIS modeller. To study the mechanics of cutting and generated cutting forces during broaching operation, an energy based force model is presented which can predict the cutting forces based on the power spent in the cutting system. An experimental investigation is conducted in order to confirm the estimated forces. The integrity of the broached surface is also investigated by focusing on surface roughness, subsurface microhardness, and subsurface microstructure as three major parameters of surface integrity. An optimization procedure for broaching tools design is presented in this thesis. A mathematical representation of broaching tooth geometry is also presented which is used to simulate the tooth as a cantilevered beam subjected to a distributed load. The beam is solved considering the given design constraints to achieve optimum geometric parameters for maximum durability and performance.
Design, analysis and optimization of novel photo electrochemical hydrogen production systems
(2013-04-01) Rabbani, Musharaf; Dincer, Ibrahim
Hydrogen is a green-energy carrier with a high heat of combustion. If obtained from renewable sources, it could be the ultimate and environmentally benign solution for the future energy requirements. This thesis presents the candidate’s research on the photochemical hydrogen production cycle, motivations and objectives, literature survey, thermodynamic modeling, exergoeconomic modeling, electrochemical modeling, statistical modeling and preliminary results of the photochemical research. The process selected for the present study is known as the “chloralkali process”. The main objective of this research is, in this regard, to develop a hybrid system that produces hydrogen by photo chemically splitting water and neutralizing the by-products (i.e. hydroxyl ions) into a useful industrial process. To be more specific, the objective of this present study is to develop a system that combines photochemical hydrogen production with electrochemical chlorine and sodium hydroxide production in a photo electrochemical chloralkali process. Initially, a series of experiments are performed by using an electric power supply. These initial experiments are followed by photo electrochemical experiments, experiments with salt water, experiments without hole scavenger material and solarium experiment. The results of electrochemical experiments show that the concentration of brine in the anolyte compartment and the concentration of electrolyte in the catholyte compartment do not affect the rate of chlorine and hydrogen production. The applied voltage, reactor temperature, and current density have a significant effect on the rate of hydrogen production. The optimal brine concentration is 225 g/L and the optimal electrolyte concentration is 25g/450ml. The increasing temperature reduces the solubility, thus increasing the rate of hydrogen production. Also, increasing the electrode surface area in contact with the working fluid increases the rate of hydrogen production. During the photo electrochemical experiments, three different process parameters are studied, namely light intensity, catalyst concentration, and applied voltage. Using statistical models and experimental data, correlations for the production rate of products are developed. Energy and exergy efficiencies are calculated to assess the performance. An optimization study for photo electrochemical experiments is performed in order to find the optimal catalyst concentration. Using the optimal catalyst concentration from the photo electrochemical experiment results, experiments with salt water in catholyte are performed. The results show that salt concentration does not have any significant effect on the rate of hydrogen production. During the photo electrochemical experiments, it is observed that applied voltage has a significant effect on the rate of photochemical hydrogen production. This fact is further explored by performing experiments without hole scavenger material. The results show the continuous production of hydrogen. Ultimately, this means that a solid electrode can replace the hole scavenger material. Energy, exergy, and exergoeconomic models for a heliostat based hybrid system are developed. A radiation model is coupled with a thermodynamic model in order to predict the rate of hydrogen, chlorine, and sodium hydroxide production for a given light intensity at a particular time. The parameters of the radiation model are set to simulate two varied weather conditions-namely a clear sky and a turbid sky environmental setting. Toronto is assumed to be a place where photo electrochemical chloralkali plant is located. The result shows that the maximum intensity occurs at noon time with the surface angle of 22° in an environment with a clear sky. The cost of hydrogen is calculated from the exergoeconomic model. The average annual cost for the hydrogen based on this model is calculated to be 0.7$/kg for a clear sky environment and 1.3$/kg for a turbid sky environment. To find the minimum required potential, the electrochemical model is developed. The parametric study of different processing parameters shows that the brine concentration and electrolyte concentration do not have significant effect on required cell potential. Current density, temperature, and distance between electrodes, however, have a significant effect on cell potential. The results of the electrochemical model are consistent with the electrochemical experimental results.
Investigation of energy storage options for sustainable energy systems.
(2013-08-01) Hosseini, Mehdi; Dincer, Ibrahim
Determination of the possible energy storage options for a specific source of energy requires a thorough analysis from the points of energy, exergy, and exergoeconomics. The main objective of this thesis is to investigate energy storage options for sustainable energy systems. A technology description and illustration of concerns regarding each system is presented. Moreover, the possibility of implementing each option into different sources of energy is investigated. Thus, integrated energy systems are developed, utilizing energy storage options with the aim of achieving more efficient systems. Energy and exergy analyses are performed for three novel, integrated renewable energy-based systems. Energy storage methods investigated here include hydrogen storage, thermal energy storage, compressed air energy storage, and battery. Solar, wind, and biomass are the energy sources considered for the integrated systems. In this research, a discussion on various energy storage systems is presented, and the potential of each storage option in the current and future energy market is studied. Each of the integrated systems is described and its operating strategy is presented. The components of the integrated systems are first modeled to obtain their operating characteristics. The energy, exergy, and exergoeconomic equations are applied to the components to calculate the rates of energy and exergy flows. The efficiencies are subsequently calculated. The results of energy and exergy analyses are combined with exergoeconomic equations to report the unit exergy cost of flows in the components. System 1 consists of a PV system, a water electrolyser and a fuel cell to generate electricity for a house. Hydrogen and thermal energy storage are considered as the storage options. The results show that the capacities of the components depend on weather data and electric power demand. In System 1, the PV electric power output exceeds demand during months with high-solar irradiance. The results of a case study based on the weather data in Toronto, Canada, and the electricity demand pattern of a Canadian house (5.74 kW maximum demand) are presented. The photovoltaic system capacity and the electrolyser nominal hydrogen production rate are 37.17 kW and 4.5 kg/day, respectively. The economic investigation of the hybrid system reports an average cost of electricity of 0.84 $/kWh based on 25 years of operation. The optimal nominal capacity of the fuel cell is found to be 1.5 kW, according to the optimization results. The optimal exergy efficiency varies from 9.91 to 9.94%. System 2 consists of a wind park, a PV-fuel cell and a biomass-fuel cell-gas turbine system. This integrated renewable energy-based system is developed for baseload power generation and utilizes wind, solar and biomass energy resources. For a 64 bar compressed air storage system, and a 36 bar gas turbine inlet air pressure, 356 wind turbines are required. The lower the pressure difference between the compressed air in the cavern and the gas turbine inlet air pressure, the fewer the number of wind turbines required in the Wind-CAES system. The results also show that 5.4×105 PV modules (covering 0.66 Mm2 of land) are required to generate 5 MW of baseload electric power. Optimization of System 2 provides a range of optimal points at which the exergy efficiency and the total purchase cost of the system are optimum. At an optimal point, the overall exergy efficiency of the integrated system is reported as 36.85%. At this point, the optimal values of compression ratio, gas turbine expansion ratio, and CAES storage capacity are 8, 6.5, and 240 h, respectively. System 3 consists of a biomass gasifier integrated with a gas turbine cycle (biomass-GT). As another sub-part of System 3, a PV-electrolyser module is integrated with a compressed air energy storage system. The overall hybrid system supplies 10 MW baseload electric power, and 7730 MWh thermal energy. The PV is accountable for 56% of the annual exergy destruction in the hybrid system, and 38% of the annual exergy destruction occurs in the biomass-GT system. The overall energy and exergy efficiencies of System 3 are 34.8 and 34.1%, respectively. The hybrid PVbiomass system is sensitive to some parameters such as the steam-to-carbon ratio of the biomass gasifier, and the gas turbine inlet temperature and expansion ratio. A 29% increase in energy and exergy efficiencies is reported with the increase in SC from 1 to 3 mol/mol. The related specific carbon dioxide emission reduction is from 1441 to 583 g/kWh.
Modeling, analysis and optimization of integrated energy systems for multigeneration purposes
(2013-08-01) Ahmadi, Pouria; Dincer, Ibrahim
Energy use is directly linked to well-being and prosperity across the world. Meeting the growing demand for energy in a safe and environmentally responsible manner is an important challenge. There are around seven billion people on Earth and population growth will likely lead to an increase in energy demand, which depends on the adequacy of energy resources. In addition, increasing population and economic development in many countries have serious implications for the environment, since energy generation processes (e.g., generation of electricity, heating, cooling, and shaft work for transportation and other applications) emit pollutants, many of which are harmful to ecosystems. Utilizing advanced technologies to mitigate global warming and increase the efficiency of energy systems are key objectives, with ways to meet them proposed and tested in many countries. Among these technologies, multigeneration processes stand out as a possibility for making important contributions due to their potential for high efficiencies as well as low operating costs and pollution emissions per energy output. In this PhD thesis, three novel multigeneration energy systems are considered, analyzed and optimized. The aim is to consider both renewable- and non-renewable-based multigeneration systems. A non-renewable-based multigeneration system is composed of a gas turbine as a prime mover, a double pressure heat recovery steam generator, a single effect absorption chiller, a domestic water heater, an ejector cooling system and PEM electrolyzer. This proposed multigeneration system can produce electricity, heating, cooling, hot water and hydrogen simultaneously. The overall exergy efficiency of the system is 60%, which is 30% higher than the power generation system. Observations show that shifting from a conventional power generation system to a multigeneration cycle leads to a decrease in CO2 emissions of approximately 120 kg/kWh, providing significant motivation to convert to multigeneration cycles. For renewable-based multigeneration systems, biomass-based and integrated ocean thermal energy conversion (OTEC)-based were selected as candidates to meet the requirements of producing electricity, heating, cooling, hot and fresh water and hydrogen. The biomass-based multigeneration system is composed of a biomass combustor, an ORC cycle for producing electricity, a double-effect absorption chiller for cooling, a heat exchanger for heating, a proton exchange membrane (PEM) electrolyzer for producing hydrogen, a domestic water heater for producing hot water and a reverse osmosis (RO) desalinator for producing fresh water. Pine sawdust is used as the biomass fuel and burned in a biomass combustor. This multigeneration system increases the exergy efficiency by about 20% and reduces CO2 emissions by about 3500 kg/MWh compared to a conventional power generation system.The last multigeneration energy system examined is an ocean thermal energy conversion (OTEC)-based system integrated with a PV/T solar collector and a single-effect absorption chiller to provide the cooling load of the system. An OTEC system utilizes low-grade energy and has a low energy efficiency. This integrated system uses warm surface seawater to evaporate a working fluid like ammonia or a Freon refrigerant, which drives an ORC turbine to produce electricity, which in turn is used to drive a PEM electrolyzer to produce hydrogen. A reverse osmosis (RO) desalination unit is used to produce fresh water. The exergy efficiency of this integrated system is 37%, which is higher than single generation systems and, in addition, this integrated system has no emissions as it uses ocean energy instead of fuel. Multigeneration processes can make important contributions due to their potential for high efficiency as well as low operating costs and pollution emissions per energy output. Issues such as fossil fuel depletion and climate change amplify the advantages and significance of efficient multigeneration energy systems.
System integration and optimization of copper-chlorine thermochemical cycle with various options for hydrogen production
(2013-08-01) Aghahosseini, Seyedali; Dincer, Ibrahim; Naterer, Greg
The Copper-Chlorine (Cu-Cl) thermochemical water splitting cycle is one of the most attractive alternative thermochemical cycles for clean hydrogen production due to its lower temperature requirement and better overall efficiency. CuCl electrolysis is considered a key process in the Cu-Cl cycle of hydrogen production where H2 gas is produced by oxidation of CuCl particles dissolved in concentrated HCl solution. A lower electrochemical cell voltage than water electrolysis is a significant advantage of CuCl electrolysis and makes this process attractive for hydrogen production. Nevertheless, an integration of both hydrolysis and electrolysis processes is one of the most important engineering challenges associated with the Cu-Cl cycle of hydrogen production. The kinetics of the hydrolysis reaction indicates the reversibility of this process. This requires H2O in excess of the stoichiometric quantity which significantly decreases the overall thermal efficiency of the Cu-Cl cycle. Moreover, the HCl concentration in the produced gas mixture of H2O and HCl in the hydrolysis reaction is in much lower concentration of the electrolysis reaction requirement for an effective electrolytic cell performance. In this PhD thesis, an integrated process model of the hydrolysis and electrolysis processes is simulated by introducing intermediate heat recovery steam generator (HRSG) and HCl-H2O separation process consisting of rectification and absorption columns. In the separation processes, the influence of operating parameters including reflux ratio, mole fraction of HCl in the feed stream, solvent flow rate and temperature, and column configuration variables, such as the location of feed stage and number of stages on the heat duty requirements and the composition of products are investigated and analyzed. It is shown that the amount of steam generated in the HRSG unit satisfies the extra steam requirement of the hydrolysis reaction up to 14 times more than its stoichiometric value and the separation process effectively provides HCl acid up to the concentration of 22 mol% for the electrolysis reaction. In order to achieve an effective integration of the electrolysis process with hydrolysis and decomposition reactions of the Cu-Cl cycle, a lab-scale CuCl electrolysis unit is designed, fabricated and tested. The influences of operational factors on the cell performance are then investigated. In the experiments, the effects of operating parameters, including HCl and CuCl concentrations, applied current density, temperature and solution flow rate on the cell potential and hydrogen production rate are experimentally investigated and analyzed. A fractional factorial design is performed, based on design of experiment methods, to find a correlation between cell voltage and operation factors. The present model predicts the effects of various operating variables on the cell voltage to provide new insight into an integration of the electrolysis process. A close agreement of the measured and theoretical hydrogen production rate confirms the accuracy of measurements and reliability of the experimental studies. An innovative integration of gasification process and Cu-Cl cycle, which can effectively contribute to hydrogen production with higher efficiency and lower environmental impact, is also studied and evaluated. In this study, the effects of using oxygen instead of air in the gasification process, where it is produced and supplied by the integrated Cu-Cl cycle is investigated. It is shown that using oxygen instead of air in the gasification process increases the gasification temperature and helps to eliminate NOx emissions. It is demonstrated that increasing the equivalence ratio (ER) from 0.1 to 0.4 improves the gasification exergy efficiency by about 10%. The influence of ER on the iv syngas composition is also studied. The gasification products rely on specific syngas compositions and could potentially provide a precursor to the combined cycle for power generation in an Integrated Gasification Combined Cycle (IGCC) power plant. The process model of a gasification process is simulated based on the industrial Texaco IGCC plant in which the heat of syngas cooling process is utilized to supply extra steam requirement of the hydrolysis reaction in the Cu-Cl cycle. The effects of steam recovery in the hydrolysis reaction on energy and exergy efficiencies of the Cu-Cl cycle are analyzed and discussed.
Development, analysis and life cycle assessment of integrated systems for hydrogen production based on the copper-chlorine (Cu-Cl) cycle
(2013-08-01) Ozbilen, Ahmet Ziyaettin; Dincer, Ibrahim; Rosen, Mark A.
The energy carrier hydrogen is expected to help solve many energy challenges we are facing today. Thermochemical water splitting using a Cu-Cl cycle, linked with renewable energy sources and/or the Generation IV nuclear super-critical water cooled reactor (SCWR), is a promising option for hydrogen production. The University of Ontario Institute of Technology (UOIT), Clean Energy Research Lab (CERL) has a research team working on the Cu-Cl hydrogen production cycle to demonstrate the process at the lab scale. This study aims to contribute to the development of hydrogen production using the Cu-Cl cycle by developing integrated multi-generation systems. There are three key elements of the study. First, the Cu-Cl based integrated systems are developed for multi-generation. System I has a solar tower with molten salt energy storage integrated with a steam turbine, organic Rankine cycle and a LiBr-H2O absorption cooling system. System II consists of a Generation IV SCWR integrated with the Cu-Cl cycle and a LiBr-H2O absorption cooling system. System III has a solar tower with molten salt energy storage integrated with the Cu-Cl cycle, LiBr-H2O absorption cooling system and a gas steam combined cycle. All three systems discussed in this thesis produce hydrogen as the main output. All the systems also have the capability of generating electricity and providing cooling, hot water and drying air. A novel configuration of the four-step Cu-Cl cycle is modeled in order to better understand and improve system performance and efficiency. Second, in the analysis section, the Aspen Plus process simulation package is used to evaluate the characteristics of the entire cycle in terms of energy, exergy and cost effectiveness, to support the ultimate development of a pilot plant. Alternative designs for the heat exchanger network using Aspen Energy Analyzer are studied for better thermal management. The Aspen Plus simulation results for the four-step Cu-Cl cycle illustrate that the steam to copper molar ratio can be reduced to 10 from an initial value of 16 by decreasing the pressure of the hydrolysis reactor. Thermodynamic, economic and environmental analyses are then conducted for the simulated four-step Cu-Cl cycle using various engineering tools: exergy, cost analyses, life cycle assessment and exergoenvironmental and exergoeconomic analyses. Based on the conducted research for ii the studied system under the baseline conditions, the total cost rate and environmental impact rate are determined to be 165 $/s and 37.6 Pt/s, respectively. Energy and exergy efficiencies of the four-step Cu-Cl cycle are also calculated to be 55.4% and 66.0%, respectively. Five optimization scenarios with the objective functions of exergy efficiency (single-objective), total cost rate (single-objective), environmental impact rate (single-objective), along with multi-objective exergoeconomic and exergoenvironmental optimizations are performed. Based on the single objective optimizations, it is determined that the exergy efficiency could be increased by up to 3.3% using exergy-based optimization, the cost can be reduced by up to 33% using cost-based optimization, and the environmental impact rate can be reduced by up to 39% using environmental impact-based optimization, at the expense of the nonoptimized objectives. In this regard, multi-objective optimization is conducted. Based on the exergoeconomic optimization, it is concluded that 0.80% higher exergy efficiency and 4.5% lower cost can be achieved, compared to baseline parameters. Furthermore, 0.46% higher exergy efficiency and 30% lower environmental impact rate can be achieved based on the exergoenvironmental optimization. Third, the optimized four-step Cu-Cl cycle is integrated with the novel multi-generation systems. Exergy and exergoeconomic analyses and exergetic life cycle assessment are conducted for the multi-generation systems. Multi-objective optimizations of the present integrated systems are also performed. Multi-objective optimization results show that exergy efficiencies are 45.8%, 45.3% and 46.7% for the three integrated multi-generation systems for hydrogen production. Corresponding energy efficiencies are calculated to be 76.4%, 67.4% and 81.2%, respectively, considering that rejected heat from the systems are utilized as hot water and drying air.

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