Electrifying Automobiles: The Subtle Differences Between the Full Hybrid and Plug-in Hybrid Electric Vehicles
In early September, Xin Guobin, China’s vice-minister of industry and information technology, told a forum of automakers held in Tianjin that the government would ban the production and sale of fossil fuel cars. Although no timetable has been formally announced, it is another example of increasing legislation to curb carbon emissions and control greenhouse gases. China now joins Norway, France, the UK, and India in the ban of future petrol and diesel vehicles.
This announcement follows an announcement from earlier this year when China’s industry minister, Miao Wei, imposed legislation requiring all automakers to sell a specific quota of zero and low emission vehicles, starting at 8% of overall sales by 2018. This target would rise to 10% in 2019, and 12% in 2020. More specifically, to meet these standards, car manufacturers need to produce two key vehicle architectures: battery electric and full hybrid vehicles.
In this quest to reduce emissions to meet government mandates, global automakers have developed several powertrain options with the next levels of powertrain technologies having various levels of electrification built into each one.
As with any form of technology, each has its advantages and shortfalls. All of them; however, offer significant CO2 reduction opportunities to meet requirements around the world. Integrating various degrees of electrification with the standard internal combustion engine (ICE) offers automakers a selection of hybrid powertrain options. As car companies consider all of these options, the most successful example to-date has been the iconic Toyota Prius, or the full hybrid. (For an overview of the various electrification options being employed today, up to and including the fully-electric, zero-emissions category please see my previous article Electrifying Automobiles: The Multiple levels of Vehicle Electrification.)
What is a full hybrid?
A full hybrid vehicle, such as the Toyota Prius, uses an internal combustion engine to drive the vehicle, which is complimented by an electrical system to provide additional power when needed. In addition, full hybrids can use the electric motor as the sole source of propulsion for low-speed, low-acceleration driving, such as in stop-and-go traffic, or for backing up. This electric-only driving mode can further increase fuel efficiency and significantly decrease CO2 emission under some driving conditions.
Much like with the mild hybrid system, the full hybrid’s internal combustion engine stops when at idle, and while coasting, disconnecting itself from the transmission. In addition, the hybrid’s generator converts the vehicle’s kinetic energy into electrical energy during braking and deceleration, and the system, incorporating the starter generator and ICE, boosts engine torque and power. As mentioned earlier, the vehicle can propel itself in full electric mode with the assistance of the generator, in tandem with the ICE, or simply the ICE itself.
What is a plug-in hybrid electric vehicle (PHEV)?
A variation of the full hybrid is the plug-in hybrid electric vehicle, which shares all the same components, with the addition of an electrical outlet or charger, which can be used to charge the vehicle when not in use. Now a feature on newer Toyota Prius models, the plug-in feature provides the opportunity for the vehicle to operate in full electric mode more often and can be powered directly by the electrical grid. The addition of this charger is at a minimal cost. Thus, it is expected that the industry will shift towards the plug-in hybrid over the standard full hybrid much like the Toyota Prius did recently.
Vehicles equipped with a full or plug-in hybrid system can achieve CO2 reduction of 18-22% over a conventional ICE. However, such a reduction comes at a considerable cost – on average, $3,200-$3,600 for a vehicle today with a very limited electric driving range. Vehicles such as a PHEV-40, with a higher range like 40 miles (which represents the distance the vehicle can travel on battery power alone) will have an incremental cost today of more than $6000. Most industry forecasts expect the plug-in hybrid battery cost to drop by 50% over the course of the next 10 years, resulting in a $2000 less-expensive system.
China is the largest auto market in the world, with more new vehicle sales per year than any other country. The government’s announcement is a major shift in direction and a significant turning point in the electrification of passenger vehicles around the world. The move sees China joining the UK, France, and others in establishing national goals for the phase-out of internal combustion vehicles. Until this phase-out can be achieved, full hybrids and plug-in electric vehicles will be critical solutions for car companies in this quest to reduce emissions and greenhouse gases.