1.1 Introduction
Energy is used in all aspects of life, and it is considered an essential part of the existence of the ecosystem and human civilization. Thus, energy-related issues are one of the most important problems that we face in the twenty-first century. With the onset of industrialization and globalization, the demand for energy has increased exponentially over the past decades. Especially with a population growth of faster than 2% in most countries, along with improvements on lifestyles that are linked to energy demand, the need for energy is ever-increasing. Based on the current global energy consumption pattern, it is predicted that the world energy consumption will increase by over 50% before 2030. Thus, based on this pervasive use of global energy resources, energy sustainability is becoming a global necessity and affects most of the civilization (Dincer, 2010).
Currently, the world relies heavily on fossil fuels such as oil, natural gas and coal, which provide almost 80% of the global energy demands, to meet its energy requirements. It is estimated that most of large-scale energy production and consumption of energy causes degradation of the environment as they are generated from these sources. It is believed that climatic changes driven by human activities (especially greenhouse gas emissions) have significant direct negative effects on the environment and contribute to over 160,000 deaths per year from side effects associated with climate change, which is estimated to double by 2020. Moreover, the nominal prices of retail gasoline have increased approximately five times more between the years of 1949 and 2005 (Asif and Muneer, 2007; Shafiee and Topal, 2006). These aforementioned reasons have motivated researchers, scientists, engineers and technologists to look for more efficient, cheaper and ecofriendly options for energy usage. As the transportation sector is a major contributor to this problem, several alternatives to conventional vehicles are developed which can be competitive in many aspects, all while being significantly more efficient and environmentally benign. Among these alternatives are electric and hybrid electric vehicles, which are two of the leading candidates to replace conventional vehicles in the future.
Over the last few decades, concerns over the dependence and ever-increasing prices of imported oil, as well as environmental pollution and global warming, have led scientists to conduct more proactive research on vehicles with alternative energy sources. Today, approximately 15 million barrels of crude oil per day are used in the United States alone. About 50% of this crude oil is used in the transportation sector, a sector where 95% of the energy supply comes from liquid fossil fuels (Kristoffersen et al., 2011). Moreover, the increasing demand and relatively static supply for petroleum and stricter pollutant regulations have caused an increase and instability in crude oil prices. Furthermore, since the majority of the crude oil reserves are located in a few countries, some of which have highly volatile political and social situations, it presents a problem for diversified energy supply and potential cause for political conflict. In addition, the conventional vehicles using these fossil fuels cause excessive atmospheric concentrations of greenhouse gasses (GHG), where the transportation sector is the largest contributor in the United States with over a quarter of the total GHG emissions.
It is important to note that electric vehicle (EV) and hybrid electric vehicle (HEV) technologies have been improved significantly, due to recent enhancements in battery technology, and they now compete with conventional vehicles in many areas. They offer solutions to key issues related to today's conventional vehicles by diversification of energy resources, load equalization of power, improved sustainability, quiet operation as well as lower operating costs and considerably lower emissions during operation without significant extra cost. Especially, with plug-in hybrid electric vehicles (PHEVs), it has become possible to achieve further energy consumption and emission reductions as well as potential applications for performing ancillary services by being able to draw and store energy from the electric grid and utilizing it in the most efficient operational modes for both the engine and the motor. Thus, hybrid and electric vehicles are currently considered some of the best alternatives for conventional vehicles.
1.2 Technology Development and Commercialization
It would be agreed by many experts in the industry that the history of EV and/or HEV is composed of three main periods. At the dawn of mechanic traction, until the beginning of twentieth century: steam, internal combustion and electric motors (EMs) had very similar market penetration. At the time, EVs had various advantages compared to the alternatives since steam vehicles were highly dangerous, dirty and expensive, and internal combustion vehicles were newly developed and still had certain technical issues. Moreover, since the cities were considerably smaller with a very small percentage of paved roads, electric range was not a significant limitation to the users. However, with the extension of the modern road networks and large distribution of petrol stations along with mass production; internal combustion technology become significantly cheaper and the predominant technology in the vehicle market.
First HEVs were developed as early as 1899 by Porsche due to the higher efficiencies that can be achieved when internal combustion motors are operated with combination of electric traction motors. Moreover, the second resurge is triggered with the development of power electronics. The research of ...
