Road traffic is one of the major consumers of energy, particularly in western industrialized countries, and globally it exhibits the highest growth rate in energy consumption of all sectors. In the Organisation for Economic Cooperation and Development (OECD) countries, more than 33% of the total final energy consumption goes into the transportation sector, amounting to more than 11% of the world’s total primary energy consumed. Virtually all of these vehicles are operated with internal combustion engines (ICEs) fueled with gasoline, diesel, or – to a very lower extent – different kinds of gases (compressed natural gas (CNG), liquefied petroleum. | Hybrid Electric Vehicles Overview H Kabza University of Ulm Ulm Germany 2009 Elsevier . All rights reserved. Introduction Road traffic is one of the major consumers of energy particularly in western industrialized countries and globally it exhibits the highest growth rate in energy consumption of all sectors. In the Organisation for Economic Cooperation and Development OECD countries more than 33 of the total final energy consumption goes into the transportation sector amounting to more than 11 of the world s total primary energy consumed. Virtually all of these vehicles are operated with internal combustion engines ICEs fueled with gasoline diesel or - to a very lower extent - different kinds of gases compressed natural gas CNG liquefied petroleum gas liquefied natural gas or biomass-based fuels bio-diesel ethanol or vegetable oil . The combination of two factors made this enormous quantitative development possible within a century on the one hand the robustness and easy scalability of the thermodynamic conversion process from heat to mechanical energy in the ICE on the other the extremely favorable properties of liquid hydrocarbons as energy carriers that is their unparalleled energy density in terms of weight and volume easiness to handle and the seemingly abundant availability from oil wells. Only the problems associated with the enormous input and output quantities and their implications on a global scale bring the deficiencies of the ICE more clearly into view today it exhibits an only very small operational regime with optimum efficiency and this optimum efficiency is rather poor approximately between 35 and 45 cf. Figure 1 . Moreover in practical applications this optimum efficiency regime is used only occasionally if at all and there are undesirable emissions associated with the combustion process. In addition as ICEs do not provide any torque at zero speed they need an electric motor EM for starting and there are more or fewer idling phases depending .
