Aramco, KAUST team finds hybrid gasoline compression-ignition architecture can reduce GHG 26-55% vs. conventional SI
Researchers from Saudi Aramco and KAUST (King Abdullah University of Science and Technology), with a colleague from Shanghai Jiao Tong University in China, assessed the effects of adopting 4 hybrid architectures on the life-cycle GHG emissions of a novel high-reactivity fuel in an advanced compression-ignition engine (GCI). Their paper appears in the journal Applied Energy.
They contrasted 4 hybrids against conventional fuels/engines and a comparable battery electric vehicle using regionally-explicit power mixes in the 3 biggest automotive markets worldwide (China, US and Europe).
WTW GHG reduction ranges afforded by the different GCI hybrid architectures. Abdul-Manan et al.
At a high level, they found that:
Gasoline Compression-Ignition (GCI) hybrids reduce WTW GHG emissions by 7–43% versus unhybridized GCI.
GCI hybrids reduce WTW GHG emissions by 26–55% versus conventional SI.
WTW GHG reduction for BEV depends on the availability of cleaner power.
The use of larger batteries enabled higher degrees of electrification with potentially lower overall emissions. However, they found diminishing returns for every kWh of increasing battery size: a mild hybrid resulted in more than 50% GHG reduction per kWh of battery, whereas an electric vehicle only reduced emission by 4% per kWh given its much larger battery requirement.
The effectiveness of every kg of lithium (left) and cobalt (right) in reducing the WTW GHG emissions of a passenger car reduces with increasing battery size. The WTW GHG emissions reductions were calculated relative to conventional SI engine. Abdul-Manan et al.
For the study, the team used a typical medium-sized European C-segment passenger car that is equipped with a GCI engine platform, and capable of achieving 95 gCO2/km, consistent with the EU requirements for 2021.
GCI engines combine the benefits of diesel compression-ignition and gasoline spark-ignition; unlike a diesel compression-ignition engine, a GCI engine can operate with a lower-reactivity fuel for better fuel mixing time and thereby produce lower emissions of NOx and particulates.
They used four hybrid architectures in their evaluation:
- 48V mild hybrid (P0 & P2)
- Parallel hybrid (full hybrid)
- Series hybrid (full hybrid)
- Parallel/series 2-mode hybrid (full hybrid)
Four reference vehicles were equipped with:
- gasoline spark-ignition (SI) engine
- diesel compression ignition (CI) engine
- non-hybridized GCI engine running on a new high-reactivity fuel, and
- fully electrified battery electric vehicle (BEV)
Amir F.N. Abdul-Manan, Hyun-Woo Won, Yang Li, S. Mani Sarathy, Xiaomin Xie, Amer A. Amer (2020) “Bridging the gap in a resource and climate-constrained world with advanced gasoline compression-ignition hybrids,” Applied Energy, Volume 267 doi: 10.1016/j.apenergy.2020.114936