203 research outputs found

    Automatic fault detection and diagnosis in refrigeration systems, A data-driven approach

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    BS News

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    Open Data and Models for Energy and Environment

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    This Special Issue aims at providing recent advancements on open data and models. Energy and environment are the fields of application.For all the aforementioned reasons, we encourage researchers and professionals to share their original works. Topics of primary interest include, but are not limited to:Open data and models for energy sustainability;Open data science and environment applications;Open science and open governance for Sustainable Development Goals;Key performance indicators of data-aware energy modelling, planning and policy;Energy, water and sustainability database for building, district and regional systems; andBest practices and case studies

    INTELLIGENT DEMAND SIDE MANAGEMENT OF RESIDENTIAL BUILDING ENERGY SYSTEMS

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    Building energy performance has emerged as a major issue in recent years due to growing concerns over costs, resource limitations, and the potential impact on climate. According to the 2011 Buildings Energy Data Book (prepared by D&R International, Ltd. for the US Department of Energy, March 2012), the built environment demands about 41% of primary energy in the United States [1]. Given the emergence of modern sensing technologies and low-cost data-processing capabilities, there is a growing interest in better managing and controlling consumption within buildings. Estimates suggest that the simple act of continuous monitoring can lead to improvements on the order of 20% [118]. To further reduce and better control energy consumption, one can turn to the use of real-time energy-performance modeling. This thesis adopts the view that smaller buildings (i.e. homes and smaller commercial facilities), which represent more than half of the sector’s consumption, provide a rich opportunity for low-cost monitoring solutions. The real advantage lies in the growth of so-called smart meters for demand monitoring and advanced sensing for improved load control. In particular, this thesis considers the use of a small sensor package for the creation of autonomously developed, data-driven thermal models. Such models can be used to predict and control the consumption of space heating and cooling equipment, which currently represent about 50% of residential consumption in the United States. The key contribution of this work is the real-time identification of thermal parameters in homes using only two temperature sensors, solar irradiance measurements, and a power meter with load-tracking capabilities. The proposed identification technique uses the Prediction Error Method (PEM) to find a Multiple Input Single Output (MISO) state-space model. Two different models have been devised, and both have been field tested. The first focuses on energy forecasting and enables various diagnostic features; the other is formulated for more advanced capacity controls in vapor-compression air conditioners. A Model Predictive Control (MPC) scheme has been implemented and shown in simulation to yield energy reductions on the order of 30% over typical thermostatic control schemes. Similarly, the diagnostic model has been used to detect capacity degradation in operational units

    Predictive and Diagnostic Method for Vapor Compression Chiller

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    Ph.DDOCTOR OF PHILOSOPH

    14th International Conference on Turbochargers and Turbocharging

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    14th International Conference on Turbochargers and Turbocharging addresses current and novel turbocharging system choices and components with a renewed emphasis to address the challenges posed by emission regulations and market trends. The contributions focus on the development of air management solutions and waste heat recovery ideas to support thermal propulsion systems leading to high thermal efficiency and low exhaust emissions. These can be in the form of internal combustion engines or other propulsion technologies (eg. Fuel cell) in both direct drive and hybridised configuration. 14th International Conference on Turbochargers and Turbocharging also provides a particular focus on turbochargers, superchargers, waste heat recovery turbines and related air managements components in both electrical and mechanical forms

    Aeronautical engineering: A continuing bibliography with indexes (supplement 193)

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    This bibliography lists 682 reports, articles and other documents introduced into the NASA scientific and technical information system in October 1985

    Fault Tolerant Power Electronics Systems

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    Research work reported in this Ph.D. thesis is in the area of power electronics systems, specifically in the sector of electrical drives. A trustworthy operation of power electronics systems in critical applications like electric vehicles, aircrafts, satellites, and so on, has pushed engineers to develop fault-tolerant solutions. Indeed, in such applications it is necessary for the system to continue its operation, possibly with downgraded performance, even under faulty case. Present thesis reports the studied solutions to make fault-tolerant a class of electric drives under faulty conditions. It has initiated by addressing the need and importance of the usage of power electronic systems in the field of transportation sector, in particular in the automobile and aerospace industry. Permanent magnet (PM) brushless (BL) drives have become very popular thanks to their higher torque-per-ampere capabilities. Among the two different types of PM BL drives, namely those with sinusoidal back-emf (BLAC) and those with trapezoidal back-emf (BLDC), the latter ones are preferred for light-duty propulsion such as minicars and scooters, and in aeronautics as control-surface actuators. However, some concern have emerged on the use of electrical drives in such applications with regard to the fault tolerance and the power capability per volume unit. A way to effectively cope with these concerns is the adoption of multiphase drives. In this sense, a five-phase drive is a promising solution as it is the most simple multiphase structure of practical interest. The thesis starts with the study of the phase current and torque behavior in three-phase PM BLDC drive in healthy conditions. To validate the mathematical findings, a study case is used, represented by an electrical drive with in-wheel motor utilized for the propulsion of a city car. Afterwards, various types of faults in voltage source inverter (VSI) of a three-phase PM BLC drive are considered, such as one leg open, one switch open and one switch shorted. Remedial control strategies for the faults of the VSI are envisaged, that enable the three-phase PM BLDC drive to continue to operate even if in a degraded way. The resulting performance is calculated in terms of developed torque and torque ripple. The mathematical findings are substantiated with graphs obtained by simulation. A five-phase PM BLDC drive is successively considered. First, its operation and its torque capabilities are investigated in healthy conditions under ideal square-wave current supply. The torque capabilities are compared to the three-phase counterpart; torque comparison is carried out by keeping motor size constant and by considering two hypotheses: equal phase back-emf and equal phase rms current. Then, the torque available from a five-phase drive is determined under various supply modes, characterized by the conduction of a reduced number of phases; the torque available is determined by imposing an rms phase current equal to the nominal one. Moreover, the current behavior during the phase commutations for the five-phase PM BLDC drives is analyzed as they exhibit some differences with respect to the three-phase counterpart. The outcomes of the current analysis are used to derive the effective torque developed by the drive and the torque ripple exhibited as a function of the motor speed. The base speed of the drive is also determined. Also for the torque results, the differences from the well-known characteristics of the three-phase PM BLDC drives are pointed out. Lastly, an algebraic approach is developed to describe the operation of a five-phase PM BLDC drive in healthy conditions. The approach has led to the formulation of a model of the phase current supply of the motor in healthy conditions. Further, the model has been suitably adjusted to derive the mode (scheduling and magnitude) of current supplying the survival phases in the case of one or more motor open phase faults. The cases of one /two/three open phase faults have been examined and, in the case of two and three faulty phases, the cases of adjacent and non-adjacent faulty phases. For each case, the current magnitude has been found by imposing that the rms value of the current in the most solicited phase is equal to the nominal value, and the torque that the drive is able to develop as well as the maximum value of the torque ripple have been calculated. The obtained results indicate that the reduction in the motor torque as well as the extent of the torque ripple is depending, besides on the number of the faulty phases, on the relative location of the faults. The thesis work also address the evolution of electrical power generation and conversion methodologies in more electric aircraft, fault-tolerant solutions under faulty Hall sensors, and the concepts of dependability and safety aspects. The thesis work has been carried out at the Laboratory of “Electric systems for automation and automotive” headed by Prof. Giuseppe Buja. The laboratory belongs to the Department of Industrial Engineering, University of Padova, Italy
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