31 October 2011
The 17th DEER (Directions in Engine-Efficiency and Emissions Research) Conference was held this year on October 3-6 in Detroit, MI. The focus of the conference—organized by the US Department of Energy (DOE)—has been shifting from diesel emissions to engine efficiency, including both diesel and gasoline powertrains. This change in focus reflects global concerns with energy supply and climate change, as well as the current priorities of the US DOE in the area of engine and vehicle technologies. The conference included about 80 presentations and about 60 posters, as well as an exhibition by sponsors. With about 900 registered participants, the conference maintained its high level of attendance.
Regulations and Technology Trends. The stage for the conference was set by a plenary session “A View from the Bridge”, devoted to priorities in government policy, regulations, and technology trends in the transportation sector. Regulations and global technology trends were also the subject of a panel discussion, “The Role for ICEs in Our Energy Future”, that opened the second day.
World's transportation has become addicted to petroleum, which currently represents 94% of global fuel consumption [D. Sandalow, DOE]. The United States, a net oil importer since 1950, has become the world's largest importer of crude oil. Driven by energy security, sustainability and climate change, new priorities have been adopted in the US energy policy, as outlined in the recent First Quadrennial Technology Review by the US DOE. In the transport sector, the priorities are: (1) to deploy alternative hydrocarbon fuels, (2) to electrify vehicle fleet and (3) to increase vehicle efficiency. While it is expected that the internal combustion engine will remain the main type of powerplant to be used in transportation for at least several decades, a rapid evolution is envisioned in fuel, engine and vehicle technologies. The development of these new technologies will be supported by US government funding.
A big energy efficiency potential exists in global transport, according to Oak Ridge researchers [D. Greene]. Energy efficiency of the main modes of transportation, including road, air, water and rail, could be improved by 70%, 60%, 50% and 50%, respectively, by 2050. In light-duty vehicles, an 80% reduction of GHG emissions is possible by 2050, making LDVs the only sector of the US economy capable of such a reduction. Other speakers, however, pointed out that the path towards global ultra low carbon transportation will be challenging, as the world's vehicle fleet is predicted to double (from 1 to 2 billion) and the world's population is expected to grow from 7 to 9 billion over 2010-2050 [J. Simmick, BP].
In August, the United States adopted first-ever greenhouse gas and fuel economy regulations for heavy- and medium-duty trucks. This rulemaking was discussed by B. Bunker [US EPA]. Under the regulations, the heaviest trucks used in combination tractors will have to reduce fuel consumption by 9 to 23% (depending on the type of truck) by 2017. The program is expected to bring an overall cost benefit to truck operators due to the fuel savings. According to EPA/NHTSA estimates, the cost increases will be paid within 2 years for small trucks and within only one year in heavier trucks, including Class 7/8 tractors—which raises a shadow of a doubt whether the regulation was at all necessary.
Design trends in light-duty powertrains include engine downsizing, boosting, cylinder pressure feedback and variable valve trains, while dilute combustion is envisioned for gasoline engines [A. Taub, GM]. The currently dominating 4-cylinder designs are predicted to be replaced by 3-cylinder engines [H. Blaxill, Mahle]. Following the recent announcement about the diesel version of Chevrolet Cruze coming to the North American market, General Motors also acknowledged that diesel engines will play a role in their light-duty vehicles—a change in direction that may be linked to the new GHG/CAFE fuel economy targets.
Electric vehicles are predicted to remain limited to niche applications, due to the low energy density of electric batteries (two orders of magnitude lower than liquid hydrocarbon fuels) and slow refueling rates, as well as economic factors. Component and powertrain electrification, however, will be increasingly introduced in vehicles powered by internal combustion engines. The Chevrolet Volt is an extreme example of a highly electrified vehicle featuring an innovative powertrain architecture. The Volt powertrain includes an internal combustion gasoline engine, a battery pack with power electronics, a smaller electric motor/generator unit and a larger, main electric motor. The wheels are powered via a planetary gear device which replaces a transmission. The main electric motor is permanently connected to the planetary gear, while the motor/generator unit can be connected (using clutches) to the ring of the planetary gear and/or to the IC engine. With both clutches engaged, mechanical torque from the IC engine can be passed via the planetary gear to the wheels. This powertrain defies conventional classifications: depending on the level of battery charge and on driving conditions, the vehicle operates as a battery electric car, a series hybrid, or as a parallel hybrid. When the IC engine is operated, it can usually work in its “sweet spot”, high efficiency region. This type of application opens the door for new, future internal combustion engine concepts.
Efficiency is also the new front in heavy-duty engine and vehicle development [A. Greszler, Volvo]. The heavy-duty diesel engine has entered a path to increase its thermal efficiency from the current 43% to 50%. Waste heat recovery cycles are one of the new technologies to be adopted in heavy-duty engines. Engine components will be also electrified, when possible, but heavy-duty, long-haul applications present less opportunity for vehicle electrification compared to light-duty vehicles.
The DOE focus on alternative hydrocarbon-based fuels has been supported by the fuel industry. ConocoPhillips [K. Wright] expressed their preference for "drop-in" alternative fuels, as opposed to such alternative fuels as ethanol or FAME biodiesel. Drop-in fuels are defined as being compatible with (1) existing vehicles and (2) existing infrastructure, and as having the same (3) energy content and (4) molecules as petroleum fuels. Examples include GTL synthetic diesel or hydroprocessed vegetable oils, which are expected to increasingly displace petroleum in the future.