• Energy Research

Abstract In this study, the thermal management system of a hybrid electric vehicle is optimized using single and multi-objective evolutionary algorithms in order to maximize the exergy efficiency and minimize the cost and environmental impact of the system. The objective functions are defined and decision variables, along with their respective system constraints, are selected for the analysis. In the multi-objective optimization, a Pareto frontier is obtained and a single desirable optimal solution is selected based on LINMAP decision-making process. The corresponding solutions are compared against the exergetic, exergoeconomic and exergoenvironmental single objective optimization results. The results show that the exergy efficiency, total cost rate and environmental impact rate for the baseline system are determined to be 0.29, ¢28 h −1 and 77.3 mPts h −1 respectively. Moreover, based on the exergoeconomic optimization, 14% higher exergy efficiency and 5% lower cost can be achieved, compared to baseline parameters at an expense of a 14% increase in the environmental impact. Based on the exergoenvironmental optimization, a 13% higher exergy efficiency and 5% lower environmental impact can be achieved at the expense of a 27% increase in the total cost.

This paper presents recent Canadian advances in nuclear-based production of hydrogen by electrolysis and the thermochemical copper-chlorine (Cu-Cl) cycle. This includes individual process and reactor developments within the Cu-Cl cycle, thermochemical properties, advanced materials, controls, safety, reliability, economic analysis of electrolysis at off-peak hours, and integrating hydrogen plants with Canada's nuclear power plants. These enabling technologies are being developed by a Canadian consortium, as part of the Generation IV International Forum (GIF) for hydrogen production from the next generation of nuclear reactors.

This article presents new modeling of turbulence correlations in the entropy transport equation for viscous, incompressible flows. An explicit entropy equation of state is developed for gases with the ideal gas law, while entropy transport equations are derived for both gases and liquids. The formulation specifically considers incompressible forced convection problems without a buoyancy term in the y-momentum equation, as density variations are neglected. Reynolds averaging techniques are applied to the turbulence closure of fluctuating temperature and entropy fields. The problem of rigorously expressing the mean entropy production in terms of other mean flow quantities is addressed. The validity of the newly developed formulation is assessed using direct numerical simulation data and empirical relations for the friction factor. Also, the dissipation (ε) of turbulent kinetic energy is formulated in terms of the Second Law. In contrast to the conventional ε equation modeling, this article proposes an alternative method by utilizing both transport and positive definite forms of the entropy production equation.

Abstract This paper presents an overview of the status of Canada’s program on nuclear hydrogen production and the thermochemical copper–chlorine (Cu–Cl) cycle. Enabling technologies for the Cu–Cl cycle are being developed by a Canadian consortium, as part of the Generation IV International Forum (GIF) for hydrogen production with the next generation of nuclear reactors. Particular emphasis in this paper is given to hydrogen production with Canada’s Super-Critical Water Reactor, SCWR. Recent advances towards an integrated lab-scale Cu–Cl cycle are discussed, including experimentation, modeling, simulation, advanced materials, thermochemistry, safety, reliability and economics. In addition, electrolysis during off-peak hours, and the processes of integrating hydrogen plants with Canada’s nuclear plants are presented.

Abstract In this paper, a thermodynamic analysis of a subcritical boiler–turbine generator is performed for a 32 MW coal-fired power plant. Both energy and exergy formulations are developed for the system. A parametric study is conducted for the plant under various operating conditions, including different operating pressures, temperatures and flow rates, in order to determine the parameters that maximize plant performance. The exergy loss distribution indicates that boiler and turbine irreversibilities yield the highest exergy losses in the power plant. In addition, an environmental impact and sustainability analysis are performed and presented, with respect to exergy losses within the system.

Abstract A novel integrated system for the production of hydrogen at a high pressure utilizing steel furnace waste heat is presented and analyzed in this paper. The system utilizes a hybrid thermochemical copper-chlorine (Cu-Cl) cycle. This study integrates the industrial waste heat source with the thermochemical Cu-Cl cycle combined with a hydrogen compression system. The electrical energy required by the system is provided by a supporting Rankine cycle. The hydrogen compression system compresses hydrogen to a pressure of 750 bars. The integrated system is simulated with Aspen Plus software. Energy and exergy analyses are performed for the integrated system. Results from the simulations are presented and discussed. The overall energy efficiency is 38.2% and overall exergy efficiency is found to be 39.8%.

Abstract A comprehensive life cycle assessment (LCA) is reported for five methods of hydrogen production, namely steam reforming of natural gas, coal gasification, water electrolysis via wind and solar electrolysis, and thermochemical water splitting with a Cu–Cl cycle. Carbon dioxide equivalent emissions and energy equivalents of each method are quantified and compared. A case study is presented for a hydrogen fueling station in Toronto, Canada, and nearby hydrogen resources close to the fueling station. In terms of carbon dioxide equivalent emissions, thermochemical water splitting with the Cu–Cl cycle is found to be advantageous over the other methods, followed by wind and solar electrolysis. In terms of hydrogen production capacities, natural gas steam reforming, coal gasification and thermochemical water splitting with the Cu–Cl cycle methods are found to be advantageous over the renewable energy methods.

This article investigates how electromagnetic forces affect fluid friction and thermal energy exchange in microchannels. An externally applied electric field can be used to manipulate charge patterns along the walls of a microchannel, thereby controlling the speed and direction of liquid transport. In this article, uniform non-polarized electromagnetic forces are imparted across a thermal diffusion layer in a rectangular microchannel. Source terms are added to the axial momentum equation to predict spatial effects of electromagnetic forces on the near-wall velocity and temperature profiles. Fluid friction associated with electromagnetic forces along the wall is investigated based on these near-wall profiles. Also, convective energy exchange is studied with both viscous dissipation and Ohmic heating in the thermal energy equation. The analytical formulation of heat transfer considers boundary conditions of a constant wall temperature and constant wall heat flux. Numerical results of fluid velocity, temperature and friction coefficient are presented and compared successfully against past data. Copyright © 2006 John Wiley & Sons, Ltd.

Abstract This article presents an economic analysis of a Cu–Cl pilot plant with an associated parametric study. The analysis takes into account the different types of cost components such as the energy costs, operation, maintenance, fixed charges on capital investment, etc. The cost items with their percentage ranges and factors that affect accuracy and scaling are examined. Through this scaling method, the total capital investment and total cost of a Cu–Cl pilot plant are estimated by scaling against the corresponding costs of an S–I plant as presented by Brown et al. Using a six-tenths-factor rule (scaling method) with a capacity factor of 0.6, the fixed-capital investment and product cost of a Cu–Cl pilot plant are roughly estimated at about US$27.5 M and US$4.6 M for a plant capacity of 5 tons of hydrogen per day, which could be higher due to yet unforeseen factors and costs, not currently available with existing information about the Cu–Cl cycle. The fixed-capital investment and total product cost correspond to the operating and maintenance costs of the plant, respectively. The sensitivity studies show that the costs vary significantly with the size of pilot plant capacity, percentages of cost components and the capacity factor. The parametric studies with variable plant capacities, approximations and capacity factors are performed and results are illustrated in this article. Numerous assumptions and approximations have been used in this paper, in absence of actual equipment cost data for the Cu–Cl cycle. Therefore, the results of this paper cannot be generalized for other specific cases and scenarios.