The Transportation Transition to Electric
The Transportation Industry is presently undergoing the most significant transformation since its inception over a century ago. The drive to electrify light- and heavy-duty vehicles will require monumental supply chain developments from mining, materials processing, manufacturing and end-of-life recycling. In addition, monumental changes are also required in the power generation, storage and distribution sectors to decarbonize, build out and reinforce utility grid distribution to support the charging of vehicles.
What is the Difference Between Vehicle Electrification and an Electric Vehicle?
Vehicle electrification is a process in which mechanically powered accessory components and drive systems are combined or replaced with electrically powered ones to improve energy efficiency and reduce greenhouse gas (GHG) emissions.
The highest level of efficiency can be found in a fully electric vehicle in which all power is provided by either a battery and/or fuel cell to one or more electric motors to drive the vehicle and to power its control (i.e. steering and brakes, etc.) and on-board accessory systems (interior heat and air conditioning, electronics, etc.). An electric vehicle is said to employ full vehicle electrification.
There are also other electrified powertrains types that integrate an increasing number of electric components and systems to increase conventional internal combustion vehicle efficiency. These are commonly referred to as electrified or hybrid vehicles and come in a variety of forms, from the simplest engine management controls and stop-start systems employed on conventional internal combustion (IC) engines to increasingly more efficient hybrid systems that supplement and/or replace IC engine power with an electric motor drive. Hybrid vehicles will play an important role in the electric transition as they offer significantly improved efficiency while utilizing relatively modest battery capacities.
The key attributes of electrified vehicles are shown in Table 1 and Figure 1. These include the presence of an internal combustion engine, an all-electric drive mode capability, the need to plug-in to recharge or fuel with hydrogen.
Table 1. Electric Vehicle Types and Primary Features
Figure 1. Levels of Vehicle Electrification
Electric Vehicles offer the highest level of vehicle efficiency.
A Battery Electric Vehicle (BEV) employs a large battery of typically at least 50 kWh, charged from the grid to power one or more electric motor(s) to drive the vehicle. The driving range of a BEV is typically 250 to 400 miles before it requires recharging. The current challenges of BEVs typically include supply chain development, purchase price, vehicle availability and access to private and public charging infrastructure.
A Fuel Cell Electric Vehicle (FCEV) generates electricity from a fuel (most commonly hydrogen) to efficiently charge a battery and power the motor(s) to drive the vehicle. The on-board battery serves to provide intermittent higher power levels when needed that the fuel cell cannot provide by itself. FCEVs typically have greater ranges than BEVs but are still reliant on access to a hydrogen re-fueling infrastructure as well as the challenges of battery electric vehicles.
Electrified Hybrid Vehicles
An Extended Range Electric Vehicle (EREV) employs a moderately sized battery (typically 20 to 35 kWh) to provide all-electric vehicle operation over moderate distances of up to 125 miles on a full charge. After that distance, a small internal combustion engine operating under steady-state, peak efficiency conditions, serves as a generator to charge the battery allowing it to maintain power to the electric motor to extend the vehicle’s operating range. The internal combustion engine does not provide direct power to the drivetrain. EREVs can offer all-electric efficiency for many drivers over their normal daily travel needs without range anxiety. The Chevrolet Volt and BMW i3 are examples of EREVs.
A Plug-in Hybrid (PHEV) employs a significantly smaller battery capacity (typically 8 to 20 kWh) than a pure BEV while retaining the ability for all-electric vehicle operation over moderate distances up to 42 miles on a full charge. Under the California Advanced Clean Cars II regulation, PHEVs will require an all-electric range of at least 50 miles to receive manufacturer credit values.
Depending upon the size and number of the electric motor(s) and powertrain controls, some PHEVs may still engage the internal combustion engine under periods of higher-than-normal power demand. When the all-electric range capability is depleted, a PHEV will operate as a HEV. PHEVs can offer all-electric efficiency for many drivers over most of their routine daily travel needs without range anxiety.
A Hybrid (HEV) powertrain employs an electric motor(s) and a modestly sized battery of only 1 to 2 kWh, integrated with an internal combustion engine that allows for brief periods of all-electric drive, various forms of combined ICE and electric drive, or engine-only operation depending on the power demand. HEVs can feature downsized engines or engines that operate under more efficient operation modes with advanced transmissions that are supplemented by the electric motor. A HEV also features improved regenerative braking (relative to a mild-hybrid) to recover more energy when the vehicle is coasting or braking. HEVs are also commonly called full hybrids or strong hybrids.
A Mild Hybrid (MHEV) represents the simplest intermediate form of vehicle electrification which includes the addition of engine stop-start with a small electric motor and battery integrated with an internal combustion engine (ICE) that allows for very short periods of electrically assisted acceleration from a standing stop or sailing which provides small power to retain a constant speed, and energy recovery through regenerative braking. The electric motor and battery in MHEV powertrains generally do not have sufficient power to provide an independent all-electric drive mode capability. In addition, a MHEV employs electric power steering and power brake systems to ensure vehicle control during coasting and braking periods when the engine may be turned off.