Real Prospects for Energy Efficiency in the United States (2010) / Chapter Skim
Currently Skimming:
3 Energy Efficiency in Transportation
3 Energy Efficiency in Transportation
Pages 121-184
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 121... ...
Reflecting the charge to the Panel on Energy Efficiency Technologies, the transportation technologies covered here are described in terms of their perfor mance (improvements in energy efficiency and fuel consumption) , their costs, and their effects on the environment (mainly reductions in greenhouse gas emissions)
|
From page 122... ...
Note that fuel-efficiency improvements do not necessarily result in increased fuel economy, as they are often offset by the negative effects of increases in vehicle power and weight. Thus, fuel efficiency is related to the amount of use ful work that is derived from the combustion of fuel.
|
From page 123... ...
Similarly, energy use in air transportation is influenced by air-traffic-management requirements. The degree to which the underlying systems operate effectively, therefore, can fosteror in some cases, hinderenergy efficiency.
|
From page 124... ...
For the early period of its assessment (through 2020) , the panel focused primarily on opportunities to improve the energy efficiency of mainstream power trains and vehicles.
|
From page 125... ...
The results are discussed in Section 3.3. Finally, Section 3.7 outlines the challenges that will have to be met and the impediments that will have to be overcome to improve energy efficiency in trans portation, and Section 3.8 presents the panel's findings for the sector.
|
From page 126... ...
, defined as passenger cars and light trucks, are the pri mary users of gasoline. Heavy-duty vehicles (HDVs)
|
From page 127... ...
Lifetime operating costs, and thus energy efficiency, are important to companies supplying passenger and freight transportation. The commercial transportation sector is so highly competitive that even small cost differentials among firms can have a major influence on their relative profitability and growth.
|
From page 128... ...
The average fuel economy of new light duty vehicles in Europe today approaches 40 miles per gallon (mpg) , 60 percent higher than in the United States.5 Vehicle fuel economy in Japan is similar to that in Europe.
|
From page 129... ...
. As a result, average new-vehicle fuel-economy levels have stagnated for nearly two decades, and total vehicle fleet use and greenhouse gas emissions have increased steadily owing to the increasing fleet size and vehicle-miles traveled (VMT)
|
From page 130... ...
3.3.2 Light-Duty VehiclesTechnologies Long-standing concern with oil imports and greenhouse gas emissions has led to several studies by the National Research Council (NRC) , examining ways to reduce both of these.
|
From page 131... ...
A survey of recent technology assessments shows that the above technologies have the potential to reduce vehicle fuel consumption, on average, by approximately 10–15 percent in the new-vehicle sales mix11 in the nearer term (by 2020) and by 9Note that this review does not cover the effects of biofuels on petroleum consumption.
|
From page 132... ...
gasoline engines, improving energy efficiency and contributing to meeting future fuel-economy standards. Diesel Compression-Ignition Engine Owing to their high compression ratios and reduced pumping losses, turbocharged diesel engines currently offer approximately a 20–25 percent efficiency benefit over gasoline SI engines when adjusted for the higher energy density of diesel fuel.
|
From page 133... ...
. The corresponding reduction in greenhouse gas emissions depends on the greenhouse gas intensity of the electricity used to charge the battery.
|
From page 134... ...
The next generation of batteries, based on lithium-ion chemistry, is widely deployed in consumer electronic devices. Of course, the power and energy storage requirements of these devices are much smaller than those of electric vehicles.
|
From page 135... ...
has established a set of long-term performance goals for electrochemical energy storage devices: • The target for PHEV batteries is an energy storage capacity of 11.6 kWh with an energy density of 100 Wh/kg and a unit cost of stored energy of $35/kWh. • The target for BEV batteries is an energy storage capacity of 40 kWh with an energy density of 200 Wh/kg and a unit cost of stored energy of $100/kWh.
|
From page 136... ...
. Although several models of BEVs are being introduced into the market today in limited production volumes, in the near-term those BEVs that are commercially viable are likely to be small cars with modest performance capabilities, such as "city BEVs." Hydrogen Fuel-Cell Vehicle Fuel-Cell Vehicle Cell Fuel-cell technology, in a hybrid system with hydrogen as the fuel, offers the promise of significantly higher propulsion system efficiency than that of ICE tech nology, as well as zero vehicle tailpipe greenhouse gas emissions.
|
From page 137... ...
allows the engine to operate near its maximum efficiency, the estimated efficiency of CVTs is lower than the corresponding estimate for six- and seven-speed automatic transmissions.12 CVTs have been in low-volume production for well over a decade. 3.3.2.3 Nonpropulsion System Improvements Vehicle Weight and Size Reduction Reducing vehicle weight is one obvious way to reduce fuel consumption.
|
From page 138... ...
and weight reduction due to vehicle redesign are usually assumed to occur when a vehicle is redesigned, so the cost is assumed to be small. Rolling Resistance Reduction A recent NRC report on tires and passenger-vehicle fuel economy (NRC, 2006)
|
From page 139... ...
. 3.3.2.4 Summary of Potential LDV Efficiency Improvements: Performance and Environmental Impacts Table 3.2 shows the panel's estimates for the potential reductions in petroleum consumption and greenhouse gas emissions that could result over the next 25 years from the adoption of both the evolutionary and the new-vehicle technologies discussed above.
|
From page 140... ...
average electricity grid mix in 2035. Greenhouse gas emissions from hydrogen production are estimated for hydrogen produced from natural gas.
|
From page 141... ...
For PHEVs, BEVs and HFCVs, the well-to-tank emissions produced during the generation of electricity and hydrogen determine the full potential for these vehicle technologies to reduce greenhouse gas emissions. Efficiency improvements in the vehicles themselves, together with low- or zero-emissions generation of the electricity and hydrogen that they require, offer the potential for dramatic reductions in total greenhouse gas emissions.
|
From page 142... ...
The greenhouse gas emissions for HFCVs are based on the assumption that, in this transition timeframe (through 2035) , hydrogen is produced by steam reforming of natural gas, currently the most eco nomic and developed hydrogen production process.
|
From page 143... ...
, and moderate reductions in tire rolling resistance and aerodynamic drag. They have the same size and performance as those of today's vehicles.
|
From page 144... ...
. The estimates are based on an extensive review of existing studies assess ing the costs and fuel-consumption benefits of future vehicle technologies.
|
From page 145... ...
As noted earlier, efficiency improvements can be directed toward reducing actual fuel consumption or toward moderating the increase in fuel consumption that would otherwise accompany increased vehicle size and power. An estimate of the full cost of reducing fuel consumption would account for how changes in vehicle attributes such as fuel efficiency, power, and size affect the value that consumers derive from these products.
|
From page 146... ...
The estimates in Table 3.3, when combined with the estimated fuel-consump tion reductions in Table 3.2, indicate that evolutionary improvements in gasoline ICE vehicles are likely to prove the most cost-effective choice for reducing petro leum consumption and greenhouse gas emissions. These vehicles will be sold in large quantities in the near term, so if the overall cost of reducing fuel consump tion and greenhouse gas emissions from motor vehicles is to be kept as low as possible, it is critical that efficiency improvements in these vehicles be used pri marily to reduce on-the-road fuel consumption.
|
From page 147... ...
A recent NRC report (NRC, 2008c) concludes that, although "the maximum practicable number of HFCVs that could be on the road by 2020 is around two million," it would take decades -- e.g., until 2050 -- for this technology to have a major impact on oil use and greenhouse gas emissions.
|
From page 148... ...
3.3.5 Total Light-Duty Vehicle Fleet Fuel ConsumptionEstimates As stated above, the Energy Independence and Security Act of 2007 requires that the corporate average fuel economy standard be 35 mpg in 2020. The panel examined two scenarios to explore how the deployment of the advanced technologies listed in Table 3.2, together with vehicle efficiency improve ments (such as reductions in vehicle weight, aerodynamic drag, and tire rolling
|
From page 149... ...
Note that these scenarios are not predictions or forecasts of what the future vehicle fleet would be like, but instead are intended as illustrative examples of the degree of change to the vehicle fleet required to improve fleet average fuel economy. In these scenarios, the panel examined the effects on fleet fuel consumption of the fuel-economy improvements that may be achieved by 2020.
|
From page 150... ...
The result is that, by 2035, average new-vehicle fuel economy would reach 50 mpgdouble today's value. Conservative Scenario The conservative scenario assumes that the 2020 CAFE target is met 5 years later, in 2025.
|
From page 151... ...
of future cars by power train, assuming that all efficiency improvements go to raising fuel economy. Source: Cheah and Heywood, 2008.
|
From page 152... ...
In this case, the average fuel economy in 2035 reaches 52 mpg, roughly double today's value. cThe conservative scenario achieves the new CAFE target of 35 mpg only in 2025 (5 years later)
|
From page 153... ...
These illustrative scenarios show that substantial changes in vehicle weight and size, significant improvements in the efficiency of ICE power trains, and the increasing production over time of hybrid systems will all be needed to reduce the in-use fuel consumption of the U.S. LDV fleet.
|
From page 154... ...
It also assumes that growth in vehicle travel slows from 0.5 percent to 0.1 percent per year over 25 years, and that any efficiency improvements are fully offset by increases in vehicle performance, size, and weight. 3.3.6 Environmental Impacts of Light-Duty VehiclesLife-Cycle Context A full assessment of the effects on the environment of an LDV would cover energy consumption and all environmental effects, including greenhouse gas emissions, over the entire vehicle lifetime, which includes the vehicle manufacturing and dis posal stages as well as vehicle use.
|
From page 155... ...
These involve reducing emissions of greenhouse gases and other air pollutants, mitigating ecological damage, lowering traffic-related deaths and injuries, reducing noise, easing congestion, and enhancing mobility opportunities. This broader set of challenges is the context in which an assessment of transportation's energy consumption and greenhouse gas emissions must be grounded (WBCSD, 2004)
|
From page 156... ...
In addition to the design of the aircraft themselves, the systems in which they operate have a major influence on energy efficiency. The efficient use of aircraft, along with choosing the most suitable aircraft to fulfill market service requirements, is critical to improving system energy efficiency.
|
From page 157... ...
. Thus, energy efficiency in air transportation must be viewed on a compre hensive, systems basis that considers the energy performance of aircraft designs as well as how they are used.
|
From page 158... ...
. They anticipate energy efficiency improvements of 1–2 percent per year for the next two decades, yielding a total improvement of more than 30 percent over this period.
|
From page 159... ...
3.4.1 Heavy-Duty Vehicles The trucking sector is the main user of heavy-duty vehicles, defined as trucks and buses having gross vehicle weights exceeding 10,000 lb. HDVs consume about 25 percent of the fuel used in the highway sector, the vast majority diesel (Figure 3.7)
|
From page 160... ...
This example shows how high diesel fuel prices create an environment that compels carriers to focus on vehicle efficiency, both in their vehicle purchase decisions and in their fleet maintenance and operations. HDV energy efficiency is a complex issue, however, because trucks perform a wide variety of duties and operate in many environments.
|
From page 161... ...
Likewise, HDVs used mainly for local deliveries and services, such as tanker trucks and refuse and dump trucks, will appear to have low energy efficiency because they operate in congested, stop-and-go environments that are inherently fuel intensive. Many factors influence HDV energy use.
|
From page 162... ...
Greater use of these existing controls could save fuel. Table 3.9 summarizes the potential for fuel efficiency gains in long-haul trucking from various near-term options discussed above, as estimated by the vice president of advanced engineering for Volvo Powertrain.17 Looking farther out in time, the U.S.
|
From page 163... ...
Grezler, vice president of advanced engineering for Volvo Powertrain. Presentation to the Transportation Research Board, May 1, 2008.
|
From page 164... ...
. The measures examined for reducing greenhouse gas emissions by trucks are summarized in Table 3.10.
|
From page 165... ...
Areas of oppor tunity include advanced high-efficiency locomotive engines, reductions in aerody namic drag, track lubricants, lower train weight, regenerative braking, hybrids for switching engines in yards, and higher-efficiency propulsion systems.18 Railroad operations represent another area in which energy efficiency gains can be achieved. Opportunities include increased railcar capacity (from 286,000 to 315,000 lb)
|
From page 166... ...
per ton of freight moved, a 10 percent diversion of freight from truck to rail could produce a 9 per cent energy savings. This is a substantial amount of traffic diverted, however.
|
From page 167... ...
In analyzing measures that can be taken to improve energy efficiency, Kromer and Heywood (2008) estimated the potential gains in energy efficiency in marine shipping to be 20–30 percent by 2020.
|
From page 168... ...
The issue of fuel energy density is especially critical in the longer term for jet aircraft. Also, in a broader, life-cycle context, the energy consumed and the greenhouse gas emissions released during fuel production affect the overall energy and emissions impacts of the total vehicle-plus-fuels system.
|
From page 169... ...
, and uncertainty as to whether a secondary market for reselling natural gas vehicles used by fleet operators would develop. Based on the available evidence, the panel's overall assessment of natural gas as a transportation fuel is that the drawbacks of a gaseous fuel (e.g., lower specific engine power, reduced driving range, a significant energy penalty for compression in vehicle fueling, the loss of vehicle interior space owing to fuel-storage tanks, extra cost, and methane emissions)
|
From page 170... ...
, biodiesel and, potentially, gasoline- and diesel-like fuels. Also important are the life-cycle greenhouse gas emissions that result from growing and harvesting the biomass and producing and distributing the specific biofuels.
|
From page 171... ...
From a broader perspective, the critical question is the life-cycle greenhouse gas emissions that result from growing and harvesting the biomass and producing and distributing the specific biofuels produced, and whether the advantageous characteristics of the fuel (e.g., ethanol with its greater knock resistance, which could be used to increase the engine compression ratio) can be used to improve efficiency.
|
From page 172... ...
It concludes that reductions in petroleum use and greenhouse gas emissions could grow steadily over the 2020–2050 timeframe but that substantial government actions and assistance would be needed for this to happen. Establish ing a hydrogen production, distribution, and refueling system that provides a suf ficiently widespread availability of the fuel so as not to impede the growth in fuel cell vehicle deployment is a challenging (but doable)
|
From page 173... ...
, smart car sharing, smart parking, and so on. These services have the potential for significant reductions in vehicle use and therefore in energy use and greenhouse gas emissions.
|
From page 174... ...
For more personal service, smart paratransit, real-time car pools, and car-sharing services could reduce VMT.19 ITS and other advanced technologies may be used to create broader system changes with potentially much larger energy and greenhouse gas emission benefits. When transportation and land use are considered together, it is possible to imagine how new transportation systems could be developed that bring about improve ments in energy efficiency.
|
From page 175... ...
• Low-priced energy led to consumer purchasing behavior, vehicle designs, and operating decisions that emphasized convenience, style, and speed over fuel economy in automobiles and light trucks, and with added emphasis on cost-effectiveness in medium- and heavy-duty trucks, ocean shipping, and the air transport of passengers and freight. • The primary barriers to realizing greater energy efficiency in the trans portation sector are the expectations of individuals and companies about future energy prices, fuel availability, and government policies.
|
From page 176... ...
. The overall energy use and greenhouse gas emissions (and other environmental effects)
|
From page 177... ...
Major additional issues are the full greenhouse gas and other environmental impacts of aviation fuel use at high altitude and of growing airline travel; the potential for using biomass-based fuels in jets; and whether the use of low-grade residual fuel in oceangoing vessels will continue. T.8 Most transportation efficiency studies and proposals have focused on the considerable energy efficiency gains that could be achieved with
|
From page 178... ...
hybrid electric vehicles. SAE Technical Paper 2004-01-0572.
|
From page 179... ...
2007. Update for Advanced Technologies to Improve Fuel Economy of Light Duty Vehicles.
|
From page 180... ...
2008. Putting Policy in Drive: Coordinating Measures to Reduce Fuel Use and Greenhouse Gas Emissions from U.S.
|
From page 181... ...
2005. Energy efficiency, fuel economy, and policy implications.
|
From page 182... ...
2006. Tires and Passenger Vehicle Fuel Economy.
|
From page 183... ...
1999. Effects of fuel ethanol use on fuel-cycle energy and greenhouse gas emissions.
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.