Innovative approach for planning water infrastructure systems under uncertainty

Thesis (S.M. in Technology and Policy)--Massachusetts Institute of Technology, Engineering Systems Division, 2013.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Cataloged from student-submitted PDF version of thesis. Page 75 blank.Includes bibliographical references (p. 67-74).This thesis develops a framework for a flexible design approach to support decision-making in water supply infrastructure planning. It contrasts with a conventional, deterministic planning approach that uses past data or forecasts to anticipate future needs. This thesis surveys current approaches that attempt to consider uncertainty, including scenario planning, decision analysis, sensitivity analysis, real options, dynamic strategic planning, and adaptive management. A flexible design approach builds on current approaches and explores flexibility through infrastructure size and function. The approach intends to be applicable across various water infrastructure systems. This thesis describes real world and theoretical applications of flexible design, including climate change adaptation planning for water utilities, flexible planning for water infrastructure investments, and flexibility in urban drainage systems. The proposed flexible design approach employs probabilistic and simulation methods to anticipate a range of future circumstances and identify top-performing strategies. The engine of the framework is a time-series stochastic analysis that uses simulation in a discounted cash flow Excel model. First, it identifies key inputs and performance metrics, characterizes uncertainty distributions, and defines strategies of varying flexibility. Next, it employs Monte Carlo simulation and compares strategy performance through target curves and multiple criteria analyses. Singapore's water resources system inspires the characteristics of the model. The best-performing flexible approach introduces a cost savings of 15% over a 50-year timespan. To successfully implement a flexible design approach, leaders in the profession must guide the shift to planning methods that explicitly recognize the role of uncertainty in the planning process. While some implementation barriers present difficulties, the proposed flexible design approach enables substantial cost savings and fosters a deeper understanding of a water resources system in the face of future uncertainty.by Melanie Kathleen Wong.S.M.in Technology and Polic

Development of modular real-time software for the TALARIS lunar hopper testbed

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2011.Cataloged from PDF version of thesis.Includes bibliographical references (p. 117-120).Hoppers have recently emerged as a viable means for planetary exploration, and as with any new vehicle, significant testing is required to validate guidance, navigation, and control (GNC) algorithms. Furthermore, the structure, organization, and timing of the real-time software must be planned before software development begins in order to design an architecture which can match the needs and requirements of the vehicle as they evolve throughout its lifecycle. These issues are compounded in an academic environment, where software knowledge is not necessarily present and must be obtained and practiced before it can be applied. In addition, high student turnover rates can result in difficulty retaining institutional knowledge of the working software and causes further development delays while new students are trained. These problems were addressed by the TALARIS software team by implementing a flexible, modular software solution in LabVIEW on the National Instruments Real-Time Input/Output (RIO) board. After a brief introduction to the TALARIS testbed, the theory of flexibility and modularity is described as applied to the TALARIS software. In particular, the unique FPGA + PowerPC architecture and its importance to precise, real-time GNC execution are explored. Various software modules are isolated and analyzed, and several test cases are presented to illustrate the benefits of modular software with regard to development time, testing procedure, and debugging. Examples from software development, actuator characterization, and test campaigns illustrate the gradual evolution of the prototype software. Finally, a discussion of the conclusions from the work and future work is presented.by Christopher J. Han.S.M

Flexible design of urban water distribution systems

Urban water distribution systems (UWDS) are highly inter-connected and under many uncertainties from water demand, pipe roughness, and component failure. Accurate projections of these uncertainties are almost impossible, and thus it may not be a proper method to design the system to meet its performance criteria for the forecasted scenario. The system is designed for the deterministic not for the uncertainties, as a result it may not be efficient or effective to be operated under different future scenarios. Flexible design is shown as a useful strategy to cost-effectively respond to uncertainties because of its consideration of uncertainties in advance, and has been successfully applied in many engineering systems. The objective of flexible design is to identify flexibility sources in UWDS and embed them into the system design to respond to uncertainties. The thesis discussed different terms to define the property of the system to respond to uncertainties and proposed a definition of flexibility for UWDS. It then proposed different measures to indicate flexibility value and introduced an efficient method to handle numerous uncertain parameters in the model. It also develops an efficient method to identify high value flexibility sources based on the Flexibility Index. Finally the thesis presents a flexibility-based optimisation model that enable water engineers to compare different flexible design alternatives and generate optimal solutions. A definition of flexibility in UWDS is proposed to illustrate broadly its property to respond to uncertainties, since it is not so useful, or at least in this thesis to distinguish similar terms to define the property of the system to respond to uncertainties. Identified flexibility sources by the proposed method is not useful for the flexibility-based optimization model to design a system, but it might be a powerful tool to locate the weak points in the system or provide better update options during rehabilitation of the system. The computational efficiency of the proposed flexibility-based optimisation model was demonstrated by dramatic decreasing on the number of the required hydraulic simulation in the case study. Flexible designs in the case study are more expensive than inflexible design, but have better hydraulic performance under uncertainties

AN INTEGRATED MULTI-CRITERIA SCREENING FRAMEWORK TO ANALYZE FLEXIBILITY IN ENGINEERING SYSTEMS DESIGN: APPLICATIONS IN LNG INFRASTRUCTURES

Ph.DDOCTOR OF PHILOSOPH