Introduction:
An electric vehicle (EV) is an automobile that makes use of one or more electric power system to propel the vehicle. The electric vehicles are powered by the energy stored in a collector system of an extravehicular source. Even they could be powered independently by using a battery (every so often charged with the aid of solar panels, or with the aid of changing gasoline to energy the use of gasoline cells or a generator).
Electric vehicles comprise street and rail motors, submerged vessels, electric-powered spacecraft, and planes. Electric vehicles were first introduced in the late nineteenth century, while energy became a few of the desired strategies for motor automobile propulsion. Internal combustion engines have been the main propulsion technique for automobiles for the last hundred years, whereas, electric-powered energy has remained common in different automobiles like trains and smaller motors.
Different Types of Electric Vehicles are:
1. Battery Electric Vehicles (BEV):
A battery unit charged by electricity solely powers the battery electric vehicle. The battery electric vehicles entirely depend on the electricity stored in the battery, for power to run the vehicles and there is no internal combustion engine to propel or give power to the wheels of these vehicles.
The battery electric vehicles are charged by plugging into an electric power source at home or the charging station.
Figure 1 Battery Electric Vehicle
Component of Battery Electric Vehicle:
1. Electric Motor:
Electric motor is the primary propulsion system in the battery electric vehicle. The electric motor converts battery electrical energy into mechanical energy to the wheel of the vehicle.
2. Battery Pack:
The battery pack is the collection of individual cells that store electrical energy. These cells are usually lithium-ion batteries. The size and capacity of the battery pack determine the range of vehicles.
3. Power Inverter:
In electrical vehicles, the alternating current (A.C) powers the electric motor. The direct current (DC) from the battery is converted into alternating current by the power inverter.
4. Charging Port:
In battery-electric vehicles, there is a charging port, which is provided to recharge the battery through an external power source. There may be different types of connectors depending on the charging infrastructure.
5. Onboard Charger:
The onboard charger converts the AC power from the external source into DC power suitable for charging the battery.
6. Thermal Management System:
The thermal management system is essential for maintaining optimal operating temperatures of both the battery and the electric motor. This system helps to ensure the long life and effectiveness of electrical components like the battery and the motor.
7. Vehicle Control Unit (VCU) and Battery Management System (BMS):
The vehicle control unit manages various vehicle functions and the battery management system monitors and manages the state of charge, temperature, and the overall health of the battery.
Working Principles of Battery Electric Vehicles:
The working principles of battery electric vehicles can be described as explained below:
1. Charging:
The battery electric vehicle is charged by plugging it into an external power source. The onboard charger converts AC power from the source into DC power to charge the battery.
2. Battery Storage:
The battery stores the electrical energy into chemical form. The energy is later converted back to electricity to power the electric motor.
3. Discharging:
When the driver accelerates the vehicle, the VCU (Vehicle Control Unit) sends signals to the power inverter, which converts DC power from the battery into AC power for the electric motor.
4. Propulsion:
The electric motor uses this electrical energy to generate mechanical energy, driving the wheels and propelling the vehicle.
5. Regenerative Braking:
During braking. The electric motor can act as a generator, converting kinetic energy back into electrical energy. This energy is then fed back into the battery, enhancing the overall efficiency.
2. Fuel –Cell Electric Vehicle (FCEV):
A fuel-cell electric vehicle is an electric vehicle that uses a fuel cell to generate electricity on board. These vehicles generate electricity through a chemical reaction between hydrogen and oxygen in a fuel cell.
The hydrogen and oxygen in water produce electricity and release heat as a byproduct. A fuel cell vehicle also known as a hydrogen fuel cell vehicle operates on a different principle compared to battery electric vehicles.
The most common type of fuel cell used in FCEVs is the proton exchange membrane (PEM) fuel cell.
Figure 2.a. Hydrogen Fuel Electric Vehicle Layout
Figure 2.b Fuel Cell Electric Vehicle Block Diagram.
Component of Fuel Cell Electric Vehicles:
1. Fuel Cell Stack:
The fuel cell stack is the heart of an FCEV. It consists of multiple individual fuel cells that use a chemical reaction between hydrogen and oxygen to produce electricity. The most common type of fuel cell for FCEVs is the proton exchange membrane (PEM) fuel cell.
The chemical reaction is 2H₂ + O₂ → 2H₂O + electrical energy.
2. Hydrogen Tank:
The fuel cell electric vehicles store compressed gas in high-pressure tanks. The hydrogen is then delivered to the fuel cell stack when needed.
3. Power Control unit:
The power control unit manages the flow of electrical power between the fuel cell stack and the electric motor. It may include power electronics to regulate the voltage and current for optional performance.
4. Electric Motor:
These fuel vehicles are equipped with an electric motor that is powered by the electricity generated in the fuel cell stack. This motor drives the wheel of the vehicle.
5. Battery (optional):
In some FCEVs, a small battery can be included to store excess energy generated by the fuel cell stack. This battery can provide additional power during acceleration or other high–demand situations.
6. Air Intake:
For the electrochemical reaction with hydrogen, the FCEVs pull the atmospheric air through the air intake system to provide the necessary oxygen to the fuel cell.
7. Water Vapour Release:
The byproduct of the chemical reaction in the fuel cell is water vapor, which is released as part of the vehicle’s emissions.
Working Principles of Fuel Cell Electric Vehicles:
1. Hydrogen Intake:
Compressed hydrogen gas is taken from the high-pressure storage tank and fed into the fuel cell stack.
2. Electrochemical Reaction:
In the fuel cell stack, hydrogen reacts with oxygen from the air to produce electricity, water vapor, and heat. The generated electricity that powers the electric motor.
3. Electricity Generation:
The electric motor uses the generated electricity to propel the vehicle. The electric motor works like that of battery electric vehicles.
4. Water Vapor Release:
The only emission from a fuel cell vehicle is water vapor, making it a clean and environmentally friendly option.
5. Regenerative Braking:
Similar to battery electric vehicles, some Fuel cell electric vehicles incorporate regenerative braking, where the electric motor acts as a generator during braking to recover energy and charge the battery if present.
Fuel Cell Electric Vehicles are considered environmentally friendly because they produce zero emissions at the tailpipe, and their only byproduct is water vapor. However, challenges include the development of a hydrogen infrastructure for refueling and the energy-intensive process of producing hydrogen.
3. Plug-In Hybrid Electric Vehicle:
A plug-in hybrid vehicle is a type of hybrid vehicle that combines features of both traditional internal combustion engine vehicles and battery electric vehicles. Plug-in hybrid vehicles have the ability to operate on electric power alone for a certain distance and can also use an internal combustion engine for longer journeys. The key feature of a PHEV is its ability to be charged by plugging into an external power source.
Figure 3 Plug-in Hybrid Electric Vehicle
Component of Plug-In Hybrid Electric Vehicles
1. Electric Motor:
PHEVs are equipped with an electric motor that can propel the vehicle using electricity stored in a battery. The electric motor works in tandem with the internal combustion engine.
2. Battery Pack:
PHEVs have a larger battery pack compared to traditional hybrids, allowing them to store more electrical energy for extended electric-only driving. The battery is typically charged by plugging into an electric power source.
3. Internal Combustion Engine:
PHEVs also have a traditional internal combustion engine, usually powered by gasoline or diesel, which provides additional range when the battery is depleted.
4. Charging Port:
PHEVs are equipped with a charging port that allows the vehicle to be connected to an external power source, such as a standard electrical outlet or a dedicated charging station.
5. Onboard Charger:
The onboard charger converts AC power from the external source into DC power suitable for charging the battery.
6. Power Control Unit (PCU):
The PCU manages the power flow between the electric motor, the battery, and the internal combustion engine, optimizing efficiency and performance.
7. Regenerative Braking:
PHEVs often feature regenerative braking, where the electric motor acts as a generator during braking to convert kinetic energy back into electrical energy, which is then used to charge the battery.
Working Principle of Plug-In Hybrid Electric Vehicles:
1.Electric-Only Mode:
In electric-only mode, the PHEV operates using electricity stored in the battery. This mode is suitable for shorter trips and can be used for commuting or driving in urban areas.
2. Hybrid Mode:
When the battery charge is depleted or additional power is needed for high-demand situations, the internal combustion engine kicks in, and the vehicle operates in a hybrid mode. In this mode, both the electric motor and the internal combustion engine work together to provide power to the wheels.
3. Charging:
PHEVs can be charged by plugging into an electric power source. The battery can be charged overnight using a standard electrical outlet or more quickly using a dedicated charging station.
4. Fueling:
For longer trips or when the battery is depleted, PHEVs can be fueled like traditional vehicles at gas stations, using gasoline or diesel.
PHEVs offer a balance between the benefits of electric-only driving and the flexibility of a traditional internal combustion engine, making them a suitable choice for drivers who want to reduce their fuel consumption and emissions without sacrificing the convenience of longer driving ranges.
3. Mild Hybrid Electric Vehicle
A Mild Hybrid Electric Vehicle (MHEV) is a type of hybrid vehicle that incorporates a small electric motor to assist the internal combustion engine. Unlike full hybrid or plug-in hybrid vehicles, MHEVs cannot operate on electric power alone for an extended period; instead, the electric motor provides support to the conventional engine. The primary purpose of the electric motor in MHEVs is to improve fuel efficiency and reduce emissions.
Figure 4 full Hybrid and mild hybrid vehicles
Components of Mild Hybrid Electric Vehicle:
1. Electric Motor:
MHEVs have a small electric motor that assists the internal combustion engine during acceleration and other high-demand situations. This motor is generally not powerful enough to propel the vehicle on its own.
2. Battery:
MHEVs feature a small battery, typically with a lower capacity than the batteries in full hybrid or plug-in hybrid vehicles. The battery stores energy captured during braking and deceleration, which is then used to assist the engine.
3. Start-Stop System:
Many MHEVs are equipped with a start-stop system, where the internal combustion engine turns off when the vehicle is stationary, such as at traffic lights. The electric motor helps restart the engine quickly and smoothly when needed.
4. Regenerative Braking System:
MHEVs often employ regenerative braking, similar to full hybrid vehicles. The electric motor acts as a generator during braking, converting kinetic energy into electricity, which is then used to charge the small battery.
5. Power Assistance:
The electric motor provides additional power during acceleration, reducing the load on the internal combustion engine and improving overall fuel efficiency.
Working Principle of MHEVs:
1. Idle Start- Stop:
When the vehicle comes to a stop, the internal combustion engine is automatically turned off to save fuel. The small electric motor helps restart the engine quickly when the driver releases the brake or presses the accelerator.
2. Acceleration Assistance:
During acceleration, the electric motor provides additional power to assist the internal combustion engine, reducing fuel consumption.
3. Regenerative Braking System:
When the driver applies the brakes, the electric motor acts as a generator, capturing energy during deceleration. This energy is used to charge the small battery.
4. Battery Assistance:
The stored electrical energy in the small battery is used to provide additional power to the electric motor during acceleration or other situations where extra power is required.
MHEVs offer fuel efficiency benefits without the need for external charging. They are often positioned as a cost-effective and simpler alternative to full hybrids or plug-in hybrids, providing some of the advantages of electrification without significant changes to the vehicle’s overall design or driving experience.