Introduction to Transportation Electrification

Transportation electrification has been a crucial effort to promote alternative fueled vehicles since the mid-2000s. It typically refers to the use of electricity from external electrical power sources, including the electrical grid for all or most parts of the vehicles. To achieve lower fuel consumption and reduced greenhouse gas emissions, higher efficiency vehicles are required with improved performance. Electrified transportation aims to utilize more electrical energy to power traction and non-traction loads in the vehicle. Read on to learn more about transportation electrification and its basics.

 

Overview

Transportation accounts for 28% of total U.S. energy use and 33% of carbon dioxide emissions. Mobility is one of the most critical parameters to achieve economic growth. Electrification is the most promising solution to enable a more sustainable and environment friendly transportation system [1]. The efficiency of the electrical powertrain, along with the power and energy density of the key components, is crucial to improve the vehicle's electric range. These factors help in attaining peak efficiency while maintaining lower energy consumption with less emissions. A reliable, clean, and sustainable transportation system can only help in enhancing mobility.

Electrification is deemed to be the most promising solution to achieve high efficiency with significantly lower fuel consumption. This is possible by integrating electric energy storage systems, electric machines, and power electronics-based converters. The rise of distributed energy resources (DERs) is an exciting and interesting opportunity for customers but poses a challenge for the utilities and the organizations that regulate them [2]. DERs include distributed generation sources like combined heat power (CHP), wind, solar, and energy storage such as batteries.

 

Basics of Transportation Electrification

Transportation electrification refers to the use of electricity from external sources of electrical power. It is considered to be a potential quadruple win for the electric utilities and the society as it enables companies to support environmental goals while building customer satisfaction, reduce operating costs and assure the future value of existing assets. Utilities can define multiple value streams that will drive the regulatory policy and align staff around a holistic approach through transportation electrification. This can be accomplished by proactively responding to electric vehicle (EV) trends as the EV prices are decreasing while the driving range is increasing.

Electrified transportation is a paradigm shift from conventional internal combustion engine-based vehicles to more efficient and cleaner electrified vehicles. The vision of transportation electrification includes using more electrical energy to power propulsion and non-propulsion loads in vehicles. Conventional internal combustion engine-based vehicles are typically less efficient, and the average efficiency they can achieve is less than 30%. However, electrical systems can offer higher efficiencies and can be controlled easily compared to mechanical systems. Also, electrical energy can be generated using several resources like wind, solar and hydro, which are renewable and carbon-free. The illustration of the degree of electrification along with the typical fuel efficiency improvement and electric traction motor power is shown in Figure 1 [1].

 

Figure 1. Degree of electrification - typical fuel efficiency improvement and electric traction motor power [1]

 

The level of electrification for the given vehicles defines the ratio of electrical power available to the total power. In the current trend, most of the vehicles manufactured have 10 to 20% electrification. These are referred to as more-electric vehicles (MEVs) and employ electrified non-propulsion loads like electrically assisted power steering, electrically driven air conditioning or pumps, fans, and so on [1]. The next set of mild hybrids typically have a higher degree of electrification and provide auto start or stop function along with regenerative braking capability. Full hybrid EVs (HEVs) have an even higher degree of electrification and are estimated to achieve about 20 to 50% reduction in power consumption.

As a general rule of thumb, increasing the degree of electrification increases fuel efficiency. Plug-in HEVs (PHEVs) and extended range EVs (EREVs) possess larger battery packs which help in enabling a longer all-electric drive with plug-in charging. PHEVs are a good choice when the distance traveled is shorter. It is adequate as the statistics show that 85% of the vehicles in the US are driven for less than 100 km a day [1].

In an EREV, the powertrain topology is like a series hybrid, and the engine runs the generator to supply electric power to the traction motor. In all the EVs, traction power is supplied solely from an electric motor and an electric ESS. It is important to note that one of the key concerns in adopting EVs is the limited driving range, which depends on the energy density of the battery cells and the temperature.

 

Key references:

1. Berker et. al., Making the Case for Electrified Transportation, 2015.

2. Report Transportation Electrification: A Guide to Planning, Deployment, and Operations for Utilities