What to know about the potential of hybrid technology in two-wheelers in India?
We gave a webinar on fuel consumption reduction technologies for the two-wheeler fleet in India back in April, and a lively discussion followed. Questions that arose concerned original equipment manufacturer (OEM) views and readiness for a mix of internal combustion engine (ICE) and electric two-wheeler models in their portfolios, and expectations about future fuel consumption standards. Additionally, of particular interest was the mild hybrid configuration used for our analysis. Attendees wondered about the CO2 benefits and costs of other hybrid architectures possible for two-wheelers compared with mild hybrids (see slide 9 of the presentation here).
Our webinar presentation also explored different levels of a fuel consumption standard that could be met with possible electric two-wheeler market penetration, all within the context of affordable prices for Indian consumers. In this blog, though, we’ll focus on the potential of hybrids.
A full hybrid has the ability to propel the vehicle from standstill and provide pure electric driving for some distance; it also has stronger acceleration assist. “Mild” hybrid, meanwhile, is an undefined term mostly applied to hybrid systems that do not have all the functionalities of a full hybrid. In both mild and full hybrid vehicles, the CO2 reduction potential is strongly linked with the ability to recapture and reuse energy lost during braking. This is known as regenerative braking. Hybrids also include cost-effective start-stop systems that shut off the engine at idle and restart it during drive. The CO2 benefits can be further boosted by shutting off the engine during coasting and deceleration, commonly called advanced start-stop, and by using motor assist during acceleration to operate the engine at lower speeds for higher efficiency. The regenerative braking energy is stored in lithium-ion batteries and that energy is best utilized to restart the engine or to provide propulsion power to the wheels.
There are two types of “full” hybrids, parallel hybrids and series hybrids, and studies show that both can reach as high as 50% in CO2 reduction benefits. In a parallel hybrid system, the ICE and the electric motor can be used to power the vehicle together or independently. The ability of the electric motor to increase the CO2 benefits of the parallel hybrid vehicle at low engine speeds is dependent on the size of the electric motor and battery. In a series hybrid system, though, the electric motor is used as the sole source of vehicle propulsion and the ICE is used to charge the on-board battery or provide power to the electric motor.
The latest market trends show that some OEMs are unveiling parallel type scooters with mild hybrid capabilities in India. Yamaha recently launched a hybrid two-wheeler with regenerative braking, electric power assist, and idle start-stop that it says provides a 16% CO2 reduction. To increase CO2 benefits, OEMs could launch future hybrid scooters that include more advanced hybrid functionalities such as advanced start-stop and electric motor drive functionality. Most current mild hybrid systems replace the conventional alternator with a more powerful hybrid motor, commonly referred to as P0 architecture. Yamaha brands its hybrid system as Smart Motor Generator and it has an electric motor integrated into the engine crankshaft. In a passenger car, such a system is called P1 architecture. (Details of different passenger car hybrid architectures will be discussed in an upcoming ICCT paper on mild hybrids.)
P2, P3, and P4 architectures can be lumped together for two-wheelers, as their impacts are fairly similar and differ primarily in how the electric motor is integrated into the transmission. P2 and P3 architectures require redesign of the transmission, but would offer roughly twice the CO2 reduction benefit of P0 and P1 architectures at a more cost-effective price. India’s largest two-wheeler manufacturer, Hero MotorCorp, has announced a series hybrid scooter; it’s powered by an 8 kW permanent magnet AC motor that provides power to the wheels, while the conventional 124cc gasoline engine charges the lithium-ion battery pack.
Note that the maximum CO2 benefits of a full parallel hybrid are achieved only if all efficiency features are used in the vehicle. So far, most of the two-wheeler parallel hybrid models are only adding technologies such as start-stop and limited power assist and regeneration functions. ICCT’s recent assessment of two-wheelers considered a 48V mild hybrid system with idle start-stop and engine assist features that provide a CO2 reduction benefit of 17%. We also included an advanced start-stop functionality that provided an additional 8% benefit to reach a CO2 reduction benefit of 25%. However, the electric drive functionality and ability to improve ICE efficiency that a full hybrid provides in a vehicle was not explored in the analysis.
The opportunities for fuel consumption reduction from two-wheelers are plentiful. While mild hybrid two-wheelers do not offer zero tailpipe emissions like electric two-wheelers, they do allow for CO2 reductions compared to ICE two-wheelers. Hybrids are an incremental technology pathway to reduce fuel consumption during the expected transition to electric two-wheelers. No matter which pathways of technologies are chosen by manufacturers, setting stringent and ambitious fuel consumption standards for two-wheelers would bring these available technologies to market faster and accelerate the transition to electrification.