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Technologies and Approaches to Reducing the Fuel Consumption of Medium- and Heavy-Duty Vehicles
Finding 3-2. The heavy-duty-truck fuel consumption regulations in Japan, and those under consideration and study by the European Commission, provide valuable input and experience to the U.S. plans. In Japan the complexity of MHDV configurations and duty cycles was determined to lend itself to the use of computer simulation as a cost-effectives means to calculate fuel efficiency, and Japan is not using extensive full-vehicle testing in the certification process.
TECHNOLOGIES AND COSTS OF REDUCING FUELCONSUMPTION
The committee has evaluated a wide range of fuel-saving technologies for medium- and heavy-duty vehicles. Some technologies, such as certain aerodynamic features, automated manual transmissions, and wide-base single low-rolling-resistance tires, are already available in production. Some of the technologies are in varying stages of development, while others have only been studied using simulation models. Reliable, peer-reviewed data on fuel-saving performance is available only for a few technologies in a few applications. As a result, the committee had to rely on information from a wide range of sources, (e.g., information gathered from vehicle manufacturers, component suppliers, research labs, and major fleets during site visits by the committee), including many results that have not been duplicated by other researchers or verified over a range of duty cycles.
There is a tendency among researchers to evaluate technologies under conditions which are best suited to that specific technology. This can be a serious issue in situations where performance is strongly dependent on duty cycle, as is the case for many of the technologies evaluated in this report. One result is that the reported performance of a specific technology may be better than what would be achieved by the overall vehicle fleet in actual operation. Another issue with technologies that are not fully developed is a tendency to underestimate the problems that could emerge as the technology matures to commercial application. Such issues often result in implementation delays as well as a loss of performance compared to initial projections. As a result of these issues, some of the technologies evaluated in this report may be available later than expected, or at a lower level of performance than expected. Extensive additional research would be needed to quantify these issues, and regulators will need to allow for the fact that some technologies may not mature as expected.
The fuel-saving technologies that are already available on the market generally result in increased vehicle cost, and purchasers must weigh the additional cost against the fuel savings that will accrue. In most cases, market penetration is low at this time. Most fuel-saving technologies that are under development will also result in increased vehicle cost, and in some cases, the cost increases will be substantial. As a result, many technologies may struggle to achieve market acceptance, despite the sometimes substantial fuel savings, unless driven by regulation or by higher fuel prices. Power-train technologies (for diesel engines, gasoline engines, transmissions, and hybrids) as well as vehicle technologies (for aerodynamics, rolling resistance, mass/weight reduction, idle reduction, and intelligent vehicles) are analyzed in Chapters 4 and 5. Tables S-1 and S-2 provide the committee’s estimate of the range of fuel consumption reduction that is potentially achievable with new technologies in the period 2015 to 2020, compared to a 2008 baseline.1Figure S-1 provides estimates for potential fuel consumption reductions for typical new vehicles in the 2015 to 2020 time frame.
The technologies were grouped into time periods based on the committee’s estimate of when the technologies would be proven and available. In practice, the timing of their introduction will vary by manufacturer, based in large part on individual company product development cycles. In order to manage product development costs, manufacturers must consider the overall product life cycle and the timing of new product introductions. As a result, widespread availability of some technologies may not occur in the time frames shown.
The percent fuel consumption reduction (% FCR) numbers shown for individual technologies and other options are not additive. For each vehicle class, the % FCR associated with combined options is as follows:
where % FCRtechx is the percent benefit of an individual technology.
The major enabling technologies necessary to achieve these reductions are hybridization, advanced diesel engines, and aerodynamics. Hybridization is particularly important in those applications with the stop-and-go duty cycles characteristic of many MHDVs, such as refuse trucks and transit buses, as well as bucket trucks. Diesel and gasoline engine advancements are helpful in all applications and will include continuing improvements to fuel injection systems, emissions control, and air handling systems, in addition to commercialization of waste heat recovery systems. Essentially all Class 8 vehicles will continue with diesel engines as the prime mover. The third major technology improvement is total vehicle aerodynamics, especially in over-the-road applications like tractor trailers and motor coaches. Other technologies that will play a role in reducing fuel consumption in all vehicle segments include low-rolling-resistance tires, improved transmissions, idle-reduction technologies, weight reduction, and driver management and coaching.
The applications of these technologies can be put into packages and then applied to the seven types of MHDVs analyzed. The resulting fuel consumption reduction for each
More information on the baseline can be found in Chapter 6 and in TIAX (2009).