Components of Electric Power Vehicle Systems

Introduction

The electric vehicles are the best solution for driving in the city due to less pollution (Van Mierlo et al. 2006, p.1). Mierlo et al. (2006, p.1) also claim that emissions from traditional fuel vehicles cause poor air quality which threatens the population physical health. Therefore, the primary concern in many developing countries is air pollution (German 2011, p.1). The definition of an electric vehicle -according to the Oxford dictionary (1993)- is defined as “a motor car powered by an electric motor rather than an internal-combustion engine.” Carley (2017, p.50) points out that electric vehicles can divide into three types as follows: battery electric vehicles (BEV), hybrid electric vehicles (HEV), and plug-in hybrid electric vehicle (PHEV). The electric vehicles are environmentally friendly, however, the reliability and the systems may not good enough for customers. Therefore, a move toward electric propulsion has several challenges but the most significant challenge is battery recycling because it impacts the environment and human health.

This essay describes the main components and three types of electric vehicles power systems, and the main discussion illustrates the engineering challenges that a move toward electric propulsion poses to electric vehicle: battery recycling, system stability and a motor generator.

Electric vehicles system

First, this paper will describe the main components of power systems of electric vehicles and after that will discuss the power system of each electric vehicle: battery electric vehicles (BEV), hybrid electric vehicles (HEV), and plug-in hybrid electric vehicle (PHEV) respectively.

There are four main components of an electric car such as batteries, electric motor, controller, and regenerative brakes (Florian et al. 2016, p.6). The battery is a part that stores electric energy for electric vehicles (Florian et al. 2016, p.11). The battery has several types, but the most famous type of battery  which uses in electric vehicles is lithium‑ion battery (Florian et al. 2016, p.11). Florian et al. (2016, p.11) claim that lithium‑ion battery is famous because it is better than other types, for example, high-energy storage and long lifespans. On the other hand, lithium‑ion battery also has some drawback: heavy and costly (Florian et al. 2016, p.11). Electric motor uses electric energy that is stored in the battery (Florian et al. 2016, p.11). Electric motor not only gives a power to the wheels to drive the vehicles, but it also acts as a generator for producing electricity  (Florian et al. 2016, p.11). Florian et al. (2016, p.11) found that the controller is a part that controls the efficiency of the electric motor and the amount of power to supply the motor. Regenerative brakes systems will only work when the driver brakes the vehicle (Florian et al. 2016, p.13). Florian et al. (2016, p.13) present that this system converts an initial kinetic energy to electric energy. This energy is stored in a battery for propulsion or energy support when needed (Richardson 2010, p.2).

Next part will discuss the system of each electric vehicle. Battery electric vehicles release zero air pollution and use one hundred per cent electric power which is a renewable source (Alternative Fuels Data Center 2018a, p.1; Beyond Zero Emissions 2016, p.18). Carley (2014, p.3) presents that battery electric vehicles use an electric motor instead of an internal combustion engine and they also use a large battery pack to store the energy. BEVs only have a battery to energy storage then, the range of BEVs directly depends on the capacity of the battery (Un-Noor et al. 2017, p.3). Therefore, typically BEVs model have ranges around 100km to 250 km, and some high performance models can go from 300km to 500 km (Un-Noor et al. 2017, p.3). The battery pack of BEV can only be charged by plugging into an external power source at home or the station (Carley 2014, p.3). Although there are many advantages of BEVs such as zero air pollution, low noise, and convenience, BEVs still have some drawbacks, for example, shorter range than gasoline vehicles, expense, and long charge time (Un-Noor et al. 2017, p.3; Carley 2014, p.3; Seai 2015, p.4). In this part describe the hybrid electric vehicles. Richardson (2010, p.1) demonstrated that hybrid electric vehicles use both internal combustion engines and electric motors. The system and function of HEVs can divide into six types: series HEV, parallel HEV, power split HEV, plug-in hybrid electric vehicles (PHEV), micro-hybrids and kinetic hybrid system (Richardson 2010, p.1). Richardson (2010, pp.1–2) identifies the primary functions for propulsion of HBVs, for example, engine start & stop, and electric boost & electric drive. The engine starts when the driving requirements are higher than the capacity of the electric drive or there is an extra demand that needs more energy to support (Richardson 2010, p.1). In contrast, when the engine does not need to support the power engine stops working (Richardson 2010, p.1). The electric boost and electric drive make the engine have a potential to downsize and improve performance because both electric boosts and an electric drive use renewable source: electric power (Richardson 2010, p.2). However, the electric drive still has problems with low speed and low power (Richardson 2010, p.2). The final part describes the plug-in hybrid electric vehicles. The plug-in hybrid electric vehicle is one type of hybrid vehicles then the system is similar to the hybrid electric vehicles (Richardson 2010, p.2). Plug-in hybrid electric vehicles use twin power engines which the primary source is petrol or diesel engine and the second source is electric power same as hybrid electric vehicles and using a large battery pack to store energy (Alternative Fuels Data Center 2018b, p.1). Alternative Fuels Data Center (2018b, p.1) shows that the plug-in hybrid electric vehicle can reduce the energy wasted during the traffic by using electric power and when regularly drive system automatically switches over to use an internal combustion engine for speed acceleration. Furthermore, batteries can be charged by a plug-in charge or regenerative braking (Alternative Fuels Data Center 2018b, p.1). The plug-in hybrid electric vehicle has both drawbacks and benefit. Although there are a lot of advantages such as less dependence on fossil fuels and use less energy because the equipment is built from light materials but PHEVs also have disadvantages as high maintenance costs (Seai 2015, p.5).

Engineering challenges of hybrid electric and plug-in hybrid electric vehicles.

This paper will explain the engineering challenges of hybrid electric and plug-in hybrid electric vehicles. They have several challenges which still need to be considered but this paper will focus on battery recycling, system stability, and a motor generator.

1. Battery

The battery recycling is one of the challenges. It is the main function of the electric vehicle. United Nations environment program (UNEP) (2003, p.5) explains the definition of a battery as “an electrochemical apparatus which provides electrical energy through the controlled use of chemical reactions.” German (2011, p.24) point out that there are three types of a battery as follows: lead-acid batteries, nickel-metal hydride (NiMH) batteries, and lithium-ion batteries. This paper discusses only lead-acid batteries and lithium-ion batteries. United Nations Environment Program (UNEP) (2003, p.8) presents the chemical materials in a lead-acid cell are lead dioxide (PbO₂) in the positive plate, sponge lead (Pb) in the negative plate and a solution of sulfuric acid (H₂SO₄) as the electrolyte. Lead acid batteries are not only be recharged several times, but they also can be recycled (United Nations Environment Program (UNEP) 2003). Although recycling is a sustainability, waste material from the recycle process that released into land or water can damage food chain and make water contaminated which harmful to human health (World Health Organization 2017, p.4). Although the government can control all the industries that recycle battery need to add an equipment for trap lead before releasing to the environment, in general, the equipment cannot trap 100 percent of lead. In the other word, lead is still released to the environment and damage human health. Lithium-ion batteries have four main components as follows: graphite powder in the positive plate, lithium metal oxide powder in the negative plate, lithium salts and organic solvents as the electrolyte, and microporous membranes as a separator (Lowe et al. 2010, p.15). Lowe et al. (2010, p.16) found that lead-acid and nickel-metal hydride batteries are at less risk of short-circuiting and overcharging than lithium-ion batteries. Both short circuits and overcharges of lithium-ion batteries may cause unsafely of the customer. Lowe et al. (2010, p.16) also explain that short circuit increases temperature hundreds of degrees within second and create a high current of the battery. Overcharge can cause a short circuit and lead to exploration or fire (Lowe et al. 2010, p.16). The short circuit is an uncontrollable situation and the severity of damage depends on the current in the battery. One way to reduce this problem is to decrease the current of the battery but it might have an effect on the performance of vehicles.

2. System stability

Next challenge is system stability. A power switching unit is a part which switches the signals from the automation power system in HEV for the power control (Hannan et al. 2014, p.147). Hannan et al. (2014, p.147) show that power switching is sensitive to the parameters such as temperature, switching-off power electronics, and load variation. Instability of the power system and power quality can harm the customer safety. Power switching unit, loss of the power sources, short circuit, and open circuit may cause this unstable system (Hannan et al. 2014, p.147). Even though electric vehicle emission is less harmful pollution than traditional fuel vehicles, if the system is unstable, it will be more dangerous to people than fossil fuel car. Hannan et al. (2014, p.147) claim that to maintain the stability of the system and to ensure that the system operates at normal power, the energy management system must be well-designed to meet the standard operation of power and distribution system. It is not easy to design a stability system because it includes several electric parts to creating one system which some electric parts work and link together. Therefore, if change parameter of some part, it will affect other part and performance of vehicles. Currently, there are the amounts of EV application types that help customers not only manage power but also find charging point and allow customers to contact with other customers such as Elektromobility (Brener 2018, p.1). This application helps drivers to decide whether switching from fossil fuel power to an electricity by individual driving patterns and customer needs (Brener 2018, p.1).

3. Motor generation

Motor generation uses electric power to propel, and it is the main component of electric vehicles (Hannan et al. 2014, p.148). Hannan et al. (2014, p.148) show that there are several categories of motor generation such as DC motors, AC motors, and permanent magnet motors. Hannan et al.(2014, p.148) also present that although motor has plenty of series, it still has problems such as high torque, complex speed control mechanism, and a small-scale rpm band. These problems cause low performance and a high cost of the vehicle that impacts sellers because the vehicle does not meet with customers’ requirements such as good performance. The motor has only three main components: case, rotor, and stator. Then it is very difficult to improve or develop the motor design.

Conclusion

In conclusion, after looking at three different power systems, it is clear that electric vehicles not only release low harmful pollution but also meet customer requirements instance of speed and low costs of power. On the contrary, it still has several drawbacks. All three of the power systems have significant challenges relating to the battery because it may cause environmental problems, health issues and safety – which is the biggest problems. To reduce the environment, impact the governments should focus on recycling process and missions from recycling processes. In order to electric cars become more popular the battery challenge need to be resolved.