Page - (000007) - in Hybrid Electric Vehicles

Preface Hybrid electric vehicles are a mature technology for road applications and of increasing in‐ terest in other fields including aircraft. They rely on the use of two different forms of energy storage (a fuel and a battery) and try to optimize the energy flows between the correspond‐ ing energy converters (electric machines and thermal engines). Several studies in literature have pointed out the advantages of HEVs versus conventional vehicles in terms of fuel economy and environmental impact. They are mainly due to the flexibility in the choice of engine operating point that allows the engine to be run in its high efficiency region and to be downsized, so obtaining a higher average efficiency. Moreover, the engine can be turned off when the vehicle is arrested (e.g., at traffic lights) or the power request is very low (reduc‐ tion of the idle losses). Compared with battery electric vehicles (BEVs), they have longer driving ranges with smaller (and lighter) batteries and the same possibility of grid recharg‐ ing in the case of plug-in hybrid electric vehicles (PHEVs). BEVs, HEVs, and PHEVs have also the capability of partially recovering energy from brakes by inverting the energy flow from batteries to wheels through the electric machine. This book on hybrid electric vehicles brings out six chapters on some of the research activi‐ ties through the wide range of current issues on hybrid electric vehicles: choice of the best architecture, performance of converters and storage systems, energy management strategies, effect of specific driving conditions, power electronics, etc. Actually, these aspects can be hardly separated; in fact, they must be addressed together in order to fully exploit the po‐ tentiality of HEVs. Nevertheless, the contributions to this book have been separated in two sections. The first section deals with two interesting applications of HEVs, namely, urban buses and heavy duty working machines. The second one groups papers related to the opti‐ mization of the electricity flows in a hybrid electric vehicle, starting from the optimization of recharge in PHEVs through advance storage systems, new motor technologies, and integrat‐ ed starter-alternator technologies. A comprehensive analysis of the technologies used in HEVs is beyond the aim of the book. However, the content of this volume can be useful to scientists and students to broaden their knowledge of technologies and application of hybrid electric vehicles. I would like to thank InTech Publisher for inviting me to be the editor of this volume, Ms. Martina Usljebrka, and the whole Publishing Process Staff for their help in coordinating the reviews, editing, and printing of the book. Teresa Donateo Associate Professor of Fluid Machinery, Energy Systems, and Power Generation Università del Salento, Italy