74 research outputs found

    Man-portable power generation devices : product design and supporting algorithms

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    Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2006.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Includes bibliographical references (p. 351-380).A methodology for the optimal design and operation of microfabricated fuel cell systems is proposed and algorithms for relevant optimization problems are developed. The methodology relies on modeling, simulation and optimization at three levels of modeling detail. The first class of optimization problems considered are parametric mixed-integer linear programs and the second class are bilevel programs with nonconvex inner and outer programs; no algorithms exist currently in the open literature for the global solution of either problem in the form considered here. Microfabricated fuel cell systems are a promising alternative to batteries for manportable power generation. These devices are potential consumer products that comprise a more or less complex chemical process, and can therefore be considered chemical products. With current computational possibilities and available algorithms it is impossible to solve for the optimal design and operation in one step since the devices considered involve complex geometries, multiple scales, time-dependence and parametric uncertainty. Therefore, a methodology is presented based on decomposition into three levels of modeling detail, namely system-level models for process synthesis,(cont.) intermediate fidelity models for optimization of sizes and operation, and detailed, computational fluid dynamics models for geometry improvement. Process synthesis, heat integration and layout considerations are addressed through the use of lumped algebraic models, general enough to be independent of detailed design choices, such as reactor configuration and catalyst choice. Through the use of simulation and parametric mixed-integer optimization the most promising process structures along with idealized layouts are selected among thousands of alternatives. At the intermediate fidelity level space-distributed models are used, which allow optimization of unit sizes and operation for a given process structure without the need to specify a detailed geometry. The resulting models involve partial differential-algebraic equations and dynamic optimization is employed as the solution technique. Finally, the use of detailed two- and three-dimensional computational fluid dynamics facilitates geometrical improvements as well as the derivation and validation of modeling assumptions that are employed in the system-level and intermediate fidelity models. Steady-state case studies are presented assuming a constant power demand;(cont.) the methodology can be also applied to transient considerations and the case of variable power demand. Parametric programming provides the solution of an optimization problem, the data of which depend on one or many unknown real-valued parameters, for each possible value of the parameter(s). In this thesis mixed-integer linear programs are considered, i.e., optimization programs with affine functions involving real- and integervalued variables. In the first part the multiparametric cost-vector case is considered, i.e., an arbitrary finite number of parameters is allowed, that influence only the coefficients of the objective function. The extension of a well-known algorithm for the single-parameter case is presented, and the algorithm behavior is illustrated on simple examples with two parameters. The optimality region of a given basis is a polyhedron in the parameter space, and the algorithm relies on progressively constructing these polyhedra and solving mixed-integer linear programs at their vertices. Subsequently, two algorithmic alternatives are developed, one based on the identification of optimality regions, and one on branch-and-bound. In the second part the single-parameter general case is considered,(cont.) i.e., a single parameter is allowed that can simultaneously influence the coefficients of the objective function, the right-hand side of the constraints, and also the coefficients of the matrix. Two algorithms for mixed-integer linear programs are proposed. The first is based on branch-and-bound on the integer variables, solving a parametric linear program at each node, and the second is based on decomposition of the parametric optimization problem into a series of mixed-integer linear and mixed-integer nonlinear optimization problems. For the parametric linear programs an improvement of a literature algorithm for the solution of linear programs based on rational operations is presented and an alternative based on predictor-continuation is proposed. A set of test problems is introduced and numerical results for these test problems are discussed. The algorithms are then applied to case studies from the man-portable power generation. Finally extensions to the nonlinear case are discussed and an example from chemical equilibrium is analyzed. Bilevel programs are hierarchical programs where an outer program is constrained by an embedded inner program.(cont.) Here the co-operative formulation of inequality constrained bilevel programs involving real-valued variables and nonconvex functions in both the inner and outer programs is considered. It is shown that previous literature proposals for the global solution of such programs are not generally valid for nonconvex inner programs and several consequences of nonconvexity in the inner program are identified. Subsequently, a bounding algorithm for the global solution is presented. The algorithm is rigorous and terminates finitely to a solution that satisfies e-optimality in the inner and outer programs. For the lower bounding problem, a relaxed program, containing the constraints of the inner and outer programs augmented by a parametric upper bound on the optimal solution function of the inner program, is solved to global optimality. For the case that the inner program satisfies a constraint qualification, a heuristic for tighter lower bounds is presented based on the KKT necessary conditions of the inner program. The upper bounding problem is based on probing the solution obtained in the lower bounding procedure. Branching and probing are not required for convergence but both have potential advantages.(cont.) Three branching heuristics are described and analyzed. A set of test problems is introduced and numerical results for these test problems and for literature examples are presented.by Alexander Mitsos.Ph.D

    Energy Efficiency in Communications and Networks

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    The topic of "Energy Efficiency in Communications and Networks" attracts growing attention due to economical and environmental reasons. The amount of power consumed by information and communication technologies (ICT) is rapidly increasing, as well as the energy bill of service providers. According to a number of studies, ICT alone is responsible for a percentage which varies from 2% to 10% of the world power consumption. Thus, driving rising cost and sustainability concerns about the energy footprint of the IT infrastructure. Energy-efficiency is an aspect that until recently was only considered for battery driven devices. Today we see energy-efficiency becoming a pervasive issue that will need to be considered in all technology areas from device technology to systems management. This book is seeking to provide a compilation of novel research contributions on hardware design, architectures, protocols and algorithms that will improve the energy efficiency of communication devices and networks and lead to a more energy proportional technology infrastructure

    Sewage Treatment Plants

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    Sewage Treatment Plants: Economic Evaluation of Innovative Technologies for Energy Efficiency aims to show how cost saving can be achieved in sewage treatment plants through implementation of novel, energy efficient technologies or modification of the conventional, energy demanding treatment facilities towards the concept of energy streamlining. The book brings together knowledge from Engineering, Economics, Utility Management and Practice and helps to provide a better understanding of the real economic value with methodologies and practices about innovative energy technologies and policies in sewage treatment plants

    CIRCULAR ARCHITECTURE: MODELS AND STRATEGIES TO REUSE AND RECYCLE BUILDINGS

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    How we design, construct and live in our houses as well as go to work can mitigate carbon dioxide (CO2) emissions and global climate change. Furthermore, the complex world we live in is in an ongoing transformation process. The housing shortage problem is increasing as the world population and cities are increasingly growing. Thereby, we must think of all the other issues that come along with population growth, such as increased demand for built space, mobility, expansion of cities into green areas, use of resources, and materials scarcity. Various projects from history have used alternatives to solve the problem of social housing, such as increasing density in cities through housing complexes, fast and low-cost constructions with prefabricated methods and materials, and modularisation systems. However, the current architecture is not designed to meet users’ future needs and reduce the environmental impact. A proposal to change this situation would be to go back to the beginning of architecture’s conception and to design it differently. In addition, nowadays, there is an increasing focus on moving towards sustainable and circular living spaces based on shared, adaptable and modular built environments to improve residents’ quality of life. For this reason, the main objective of this thesis is to study the potential of architecture that can reconfigure spatially and temporally, and produce alternative generic models to reuse and recycle architectural elements and spaces for functional flexibility through time. To approach the discussion, a documentary research methodology was applied to study the modular, prefabricated and ecological architectural typologies to address recyclability in buildings. The Atlas with case studies and architectural design strategies emerged from the analyses of projects from Durant to the 21st century. Furthermore, this thesis is a part of the research project Eco-Construction for Sustainable Development (ECON4SD), which is co-funded by the EU in partnership with the University of Luxembourg, and it presents three new generic building typologies. They are named according to their strong characteristics: Prototype 1 - Slab typology, a building designed as a concrete shelf structure in which timber housing units can be plugged in and out; Prototype 2 - Tower typology, a tower building with a flexible floor plan combining working and residential facilities with adjacent multi-purpose facilities; and Prototype 3 - Block typology, a structure characterised by the entire disassembly. The three new typologies combine modularity, prefabrication, flexibility and disassembly strategies to address the increasing demand for multi-use, reusable and resourceefficient housing units. The prototypes continually adapt to the occupants’ needs as the infrastructure incorporates repetition, exposed structure, central core, terrace, open floors, unfinished spaces, prefabrication, combined activities, and have reduced and different housing unit sizes, in which parts can be disassembled. They also densify the region that they are being implemented in. Moreover, the new circular typologies can offer more generous public and shared space for the occupants within the same building size as an ordinary building. The alternative design allows the reconversion of existing buildings or the reconstruction of the same buildings in other places reducing waste and increases its useful lifespan. Once the building is adapted and reused as much as possible, and the life cycle comes to an end, it can be disassembled, and the materials can be sorted for reusable or recyclable resources. The results demonstrate that circular architecture is feasible, realistic, adapts through time, increases material use, avoids unnecessary demolition, reduces construction waste and CO2 emissions and extends the useful life of the buildings

    Clean Energy Systems and Experiences

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    This book reports the latest developments and trends in "clean energy systems and experiences". The contributors to each chapter are energy scientists and engineers with strong expertise in their respective fields. This book offers a forum for exchanging state of the art scientific information and knowledge. As a whole, the studies presented here reveal important new directions toward the realization of a sustainable society

    An energy, water and disease disaster management module: a technoeconomic feasibility analysis

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    Intermittent energy and water supply are current challenges faced by many residents in South Africa. South Africa is one of the more water scarce countries in the world; this coupled with the lack of infrastructure makes it challenging to provide every citizen with their right to basic water and sanitation. With millennium development goal 7C not being addressed in many areas, residents experience sub-standard living conditions, which drastically increases the vulnerability of marginalised groups to epidemics. In the sustainable development goals improving sanitation and drinking water has been identified as one of the most effective and least expensive means of reducing fatalities and increasing public health. There is a need for a mobile laboratory that demonstrates power and water self-sufficiency, which is capable of on-site diagnosis and water treatment. The unit will have the ability to perform independent compliance monitoring of municipal water supply, treat inadequate water and provide surplus electricity to surrounding areas. A literature-based study was performed utilizing several scientific databases to identify current methods of power and water production in previous disaster management and humanitarian relief situations. Based on findings three example laboratories were theoretically designed; structural modelling, systems simulation and optimization and sensitivity analyses were performed with HOMER Pro, PackVol and SketchUp. A cost benefit analysis was performed with the social return on investment methodology. Novel human waste processing was performed with fly ash and simulated faeces. Bacterial species identification in ice samples was performed with the API 20E protocol and limited equipment as a proof of concept for field deployment. A hybrid system consisting of PV panels, a wind turbine and biomass generator showed promise for displaced humanitarian relief camps; with every 1 ZAR capital invested resulting in 3.13 ZAR social benefit. A system consisting of PV panels and a battery bank proved to have the least environmental impact and the grid supply laboratory showed a cheaper cost of energy alternative for needs provision. Fly ash showed potential as in nutrient recovery and as a fertility aid to soil. The units developed function as a means to increase disaster preparedness and humanitarian relief as well a means to improve quality of life for rural marginalize populations

    Undergraduate engineering and built environment project conference 2017: book of abstracts - Toowoomba, Australia, 18-22 September 2017

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    Book of Abstracts of the USQ Undergraduate Engineering and Built Environment Conference 2017, held Toowoomba, Australia, 18-22 September 2017. These proceedings include extended abstracts of the verbal presentations that are delivered at the project conference. The work reported at the conference is the research undertaken by students in meeting the requirements of courses ENG4111/ENG4112 Research Project

    Infrastructure Regulation: Promises, Perils and Principles

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    For much of the 20th century and in most countries, network utilities, such as telecommunications, electricity, natural gas, railroads, and water supply, were vertically and horizontally integrated state monopolies under ministerial control. This approach often led to extremely weak infrastructure services, especially in developing and transition economies. Common problems included low productivity, high costs, poor quality, chronic revenue shortages and falling investments, long waits for and shortages of services, and nonpayment for and theft of services. As a result of these problems, public policies toward infrastructure have undergone profound changes over the past two decades. This report evaluates the privatization of network utilities in developing and transition economies using three criteria: the resulting levels of investment (and thus service expansion), operating (technical) efficiency, and allocative efficiency (as indicated by the rebalancing of tariffs). This report also assesses the distributional consequences of reforms, especially their effects on basic services for poor households and other disadvantaged groups. The report suggests designing pricing policies that strike a balance between economic efficiency and social equity, developing rules governing access to bottleneck infrastructure facilities, and finding new ways to increase poor people's access to services.Regulatory Reform, Other Topics
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