Mild Hybrid Electric Vehicles: Powertrain Optimization for Energy Consumption, Driveability and Vehicle Dynamics Enhancements

This thesis deals with the modeling, the design and the control of mild hybrid electric vehicles. The main goal is to develop accurate design tools and methodologies for preliminary system and component level analysis. Particular attention is devoted to the configuration in which an electric machine is mounted on the rear axle of a passenger car. The use of such a machine in parallel with the internal combustion engine allows one to exploit different functionalities that are able to reduce the overall fuel consumption of the vehicle. In addition, the indirect coupling between the thermal and the electric machine, realized through the road and not by means of mechanical couplers, together with the position of the latter in the overall vehicle chassis system, enables such an architecture to be efficient both from the energy recovery and the full electric driving point of view. Chapter 1 introduces the problem of fuel consumption and emissions reduction in the overall world context and presents the main hybrid architectures available. Chapter 2 is devoted to the study of the influence of the electric machine position in the powertrain regarding the regenerative braking potentialities concerned. The model considered for the analysis will be described on each of its subcomponents. The braking performance of the vehicle in electric mode is presented considering no losses in the electric powertrain (electric motor, battery, inverter). Chapter 3 is dedicated to the design of an electric machine for a rear axle powertrain. The specifications of such machine are optimized considering both the vehicle and the application under analysis. The design takes into account analytical techniques for the computation of electrical parameters (such as phase and DC currents) and the torque - speed map, as well as numerical ones for its thermal behavior. In Chapter 4 the electrical and thermal characteristics of the designed electric motor are implemented in the model presented in Chapter 2. The overall vehicle model is therefore used both to assess a simple torque split strategy between thermal and electric machine and to perform an optimal sizing of the battery considering all the limitations imposed by the electric powertrain (e. g. maximum currents, maximum temperatures). Chapter 5 makes a step forward and analyzes the different implications that the use of the rear axle electric motor to brake the vehicle has on the vehicle dynamics. Open loop analysis will present a degradation of the vehicle handling comfort caused by the introduction of an oversteering moment to the vehicle. Through the use of a simplified vehicle model, the introduced oversteering yaw moment is evaluated, while a control strategy based on a new stability detector will show how to find a trade off between handling comfort and regenerable energy. At last, Chapter 6 deals with the problem of longitudinal driving comfort. Drivelines and chassis are lightly damped systems and the application of an impulsive torque imposed by the driver can cause the vehicle longitudinal acceleration (directly perceived by the driver) to be oscillating and non smooth. A sensitivity analysis on a conventional powertrain is presented demonstrating which of the different components are more influential in the different modes of vibration, and possible solutions to improve the driveability are proposed. One of these relates to the use of the rear axle electric machine in order to give more responsiveness to the vehicle. Finally, concluding remarks are given in Chapter 7

Analysis of Member States' rules for allocating heating, cooling and hot water costs in multi-apartment/purpose buildings supplied from collective systems

Energy savings achieved through the improvement of metering and billing of individual consumption of heating/cooling and domestic hot water in multi-apartment and multi-purpose buildings can make a contribution to the scaling up of efforts to achieve the energy efficiency targets of the EU in 2020 and beyond. The Energy Efficiency Directive (EED) is the cornerstone of the legal framework for accurate metering and billing of individual consumption of heating/cooling and domestic hot water in multi-apartment and multi-purpose buildings in the EU. It requires the introduction of consumption-based cost allocation and sub-annual informative, consumption based billing of heating, cooling and hot water in multi-unit buildings, subject to certain conditions. Individual meters and billing permit a fairer system of repartition of the energy costs among the occupants of multi-apartment buildings based on actual energy consumption rather than estimation done according to the size of the dwelling, etc. The purpose of this report is to provide a systematic overview of the existing thermal cost allocation rules in Member States, characterising them in term of key features, such as the permitted/recommended ranges of share of variable cost allocated according to readings from individual metering devices, use of correction factors and minimum and maximum thresholds etc. The outcome of this report might be used to guide Member States in designing/revising their thermal energy cost allocation rules.JRC.C.2-Energy Efficiency and Renewable

Synthesis Report on the assessment of Member States' building renovation strategies

The European building stock consumes approximately 40% of primary energy and it is responsible for 36% of the EU greenhouse emissions. A significant reduction of building energy demand is a requisite to meet Europe’s GHG emissions reduction targets. The Article 4 of the Energy Efficiency Directive requires Member States "to establish a long-term strategy beyond 2020 for mobilising investment in the renovation of residential and commercial buildings with a view to improving the energy performance of the building stock. In order to transpose the Directive and to increase the rates and depth of building renovation, the Member States were asked to develop their first renovation strategies and provide them with their third NEEAPs, due by 30th April 2014. The JRC undertook an assessment of 31 national/regional building renovation strategies submitted by the Member States. The present report summarises the assessment performed by JRC on the received strategies. The analysis assessed and evaluated the compliance with all the items of Article 4 and checked if they were adequately addressed in each national renovation strategy.JRC.F.7-Renewables and Energy Efficienc

Influence of design parameters on the short-circuit ruggedness of SiC Power MOSFETs

This work aims to present an investigation on short-circuit (SC) failure behaviour of SiC Power MOSFETs due to the onset of thermal runaway. As inferable from experimental outcomes, it is related to the formation of hotspot, whose exact location is mainly unpredictable and dictated by device structure and design parameters non-uniformities. TCAD simulations were performed to examine the impact of some parameters mismatch on hotspot formation and failure occurrenc

Vehicle Driveability: Dynamic Analysis of Powertrain System Components

The term driveability describes the driver's complex subjective perception of the interactions with the vehicle. One of them is associated to longitudinal acceleration aspects. A relevant contribution to the driveability optimization process is, nowadays, realized by means of track tests during which a considerable amount of driveline parameters are tuned in order to obtain a good compromise of longitudinal acceleration response. Unfortunately, this process is carried out at a development stage when a design iteration becomes too expensive. In addition, the actual trend of downsizing and supercharging the engines leads to higher vibrations that are transmitted to the vehicle. A large effort is therefore dedicated to develop, test and implement ignition strategies addressed to minimize the torque irregularities. Such strategies could penalize the engine maximum performance, efficiency and emissions. The introduction of the dual mass flywheel is beneficial to this end. Nevertheless, its role on the vehicle driveability, as well as that of other driveline components, is not yet so clear. The aim of the present work is to establish which are the main driveline components affecting the filtering behavior of the transmission and how their parameters can be tuned in order to improve the vehicle ability to respond to driver’s different demands without negative impact on his comfort. A complete nonlinear coupled torsional and longitudinal vehicle dynamic model is proposed to this end. The model is validated both in time and frequency domain and allows linearization of its nonlinear components

Energy Consumption and Energy Efficiency Trends in the EU-28 2000-2015

This report aims at showing the present status of energy consumption in the EU-28, in the four main energy consuming sectors: residential, tertiary, transport and industry. During the last years, there have been efforts by the European Union to cut down on energy consumption and improve energy efficiency. From 2000 to 2014, there have been various initiatives that aim at reducing final energy consumption. Therefore, the report demonstrates the energy consumption progress from 2000 to 2015 in the mentioned four sectors.JRC.C.2-Energy Efficiency and Renewable

Review of 50 years of EU energy efficiency policies for buildings

The reduction of energy demand in buildings through the adoption of energy efficiency policy is a key pillar of the European Union (EU) climate and energy strategy. Energy efficiency first emerged in the EU energy policy agenda in the 1970s and was progressively transformed with shifting global and EU energy and climate policies and priorities. The paper offers a review of EU energy policies spanning over the last half century with a focus on policy instruments to encourage measures on energy efficiency in new and existing buildings. Starting from early policies set by the EU in response to the Oil Embargo in the 1973, the paper discusses the impact of EU policies in stimulating energy efficiency improvements in the building sector ranging from the SAVE Directive to the recently 2018 updated Energy Performance of Buildings Directive and Energy Efficiency Directive. The review explores the progress made over the last 50 years in addressing energy efficiency in buildings and highlights successes as well as remaining challenges. It discusses the impact of political priorities in reshaping how energy efficiency is addressed by EU policymakers, leading to a holistic approach to buildings, and provides insights and suggestions on how to further exploit the EU potential to save energy from buildings

A comprehensive study of the short-circuit ruggedness of silicon carbide power MOSFETs

The behavior of Silicon Carbide Power MOSFETs under stressful short circuit conditions is investigated in this paper. Illustration of two different short-circuit failure phenomena for Silicon Carbide Power MOSFETs are thoroughly reported. Experimental evidences and TCAD electro-thermal simulations are exploited to describe and discriminate the failure sources. Physical causes are finally investigated and explained by means of properly calibrated numerical investigations, and are reported along with their effects on devices short-circuit capability

Progress of the Member States in implementing the Energy Performance of Building Directive

Overall, the EPBD policy framework laid down the foundation for:i) setting cost-optimal minimum energy performance standards in new buildings and existing buildings under major renovation;ii) ensuring that prospective buyers or renters are well informed through Energy Performance Certificates and thereby encouraged to choose higher than minimum standards in their decision making processes;iii) speeding up the rate at which investors engage in energy efficiency projectsthrough national long-term renovation strategies and financemechanisms.In accordance with the policy assessment of 2017 it is expected that the EPBD islikely to deliver the expected impacts by 2020, with 48.9 Mtoe additional final energy savings and a reduction of 63 Mt of CO2.However, the new Climate agenda set higher ambition targets and together with the Covid-19 crisis, the scenario has changed consistently and the next decade will be very challenging. The energy renovation of buildings can be a pillar of both the European decarbonisation process and the economic recovery after the pandemic.This report provides a snap shot of the EPBD implementation progresses by Member States over the last years. In particular, the focus is mainly on: cost-optimal calculations to set minimum energy performance requirements, Energy Performance Certificates (EPC), Nearly Zero-Energy Buildings (NZEB), financial incentives and market barriers, Long-term Renovation Strategies (LTRS). In order to contextualize the European scenario, some general trendsare presented and discussed in the introduction