Daily Archives March 3, 2016
In the United States, all major automakers are subject to Corporate Average Fuel Economy (CAFE) standards requiring their new vehicle fleets to meet specific fuel economy targets. The standards were established by the Energy Policy and Conservation Act of 1975 in response to the 1973 oil embargo and subsequent oil price shock. Under the act, each manufacturer’s fleet of new vehicles is subdivided into passenger cars and light trucks (including pickup trucks, vans, and sport utility vehicles) and the passenger car fleet is further subdivided into domestic and import vehicles, where vehicles with less than 75% U. S./Canadian content are considered to be imports. Each individual fleet must then meet a separate target...Read More
Fuel cells convert chemical energy directly into electrochemical work without going through an intermediate thermal conversion. Thus, the second law of thermodynamics does not apply, they are not limited by Carnot’s theorem, and, therefore, they offer the potential of very high electrical efficiencies. In a fuel cell, the fuel (H2) and the oxidizer (O2) are supplied continuously (unlike in a battery). A dynamic equilibrium is maintained, with the hydrogen being oxidized to water with electrons going around an external wire to provide useful electrical work. A major limitation of fuel cells is that direct efficient oxidation of natural gas (CH4) is not yet possible...Read More
The most direct way in which to improve LDV fuel economy is to establish clear targets for new vehicle fuel economy or CO2 emissions (although the latter can theoretically be attained partly, or even solely, by switching to lower carbon fuels). In 1974, U. S. automakers voluntarily agreed to achieve a 40% improvement in fuel economy by 1980. This voluntary agreement was superseded by mandatory standards promulgated in 1975, aiming for still higher gains by 1985. Canada followed the U. S. example with a set of voluntary fuel economy targets mimicking the United States’ mandatory ones...Read More
Microturbines follow the same cycle as conventional gas turbines, although they are at a less developed stage of commercial development. Their development has come from the design of small, very high speed turbines (with compressors on the same shaft) rotating up to 100,000 rpm. Additional scaling down of components, particularly nozzles and burners, has been achieved. The marketed size range is 30-500 kWe.
Microturbines use regeneration, with resultant lowered exhaust gas temperatures (~300°C). The unit is air-cooled. Maintenance requirements are reduced due to the elimination of an oil-based lubricating system in favor of air bearings and because the microturbines have no gearbox...Read More
Center for Transportation Research, Argonne National Laboratory Washington, D. C., United States
2. Fuel Economy Standards
3. Fuel Taxes
4. Vehicle Tax Incentives Promoting Higher Fuel Economy
5. Information Programs to Promote Higher Fuel Economy
6. Government Sponsorship of Research and Development
driving cycle A carefully measured trip that is defined by the vehicle speed during every second of the trip over a specified distance; using a driving cycle allows different vehicles to be tested and compared in a consistent manner.
fuel economy A measure of vehicle fuel efficiency expressed as distance traveled divided by fuel consumed (e. g., miles per gallon, kilometers per liter).
hybrid drivetrains (hybrid vehicles) Generally refers to vehicles that ...Read More
Figure 8 presents the WTW CO emissions of the evaluated systems. Internal combustion engines produce a large quantity of CO emissions. Consequently, the technologies powered by these engines have high CO emissions. Also, the two FCV options with onboard fuel processors produce a significant amount of CO emissions. EVs and direct H2 FCVs
have much lower CO emissions than the baseline GVs do.
Figure 9 shows NOx emissions for the 23 vehicle/fuel systems. The differences between total and urban NOx emissions for all technology options are large. Of the seven SI engine vehicle options, all options fueled by alternative fuels achieve significant urban NOx emissions reductions, primarily because of low WTP urban NOx emissions for these fuels...Read More
Figure 7 shows total VOC emissions of the evaluated vehicle/fuel systems. For each technology option, the bottom bar represents total VOC emissions (emissions that occur everywhere), whereas the top bar represents urban emissions (emissions that occur within urban areas). Urban emissions, a subset of the total emissions, are determined by information on locations of facilities within the United States. For vehicle operation emissions, urban emissions are estimated by using the vehicle distance traveled within U. S. urban areas. The separation of criteria pollutant emissions is intended to provide information for potential human exposure to the air pollution caused by these pollutants...Read More
The combination of well-to-pump results and the energy use and emissions associated with vehicle operation (also called the pump-to-wheels stage) results in full well-to-wheels energy and emission results for vehicle/fuel systems. The energy efficiencies of 19 fuel pathways were presented in the preceding section. The well-to-wheels energy use and emissions results for 23 representative vehicle/fuel systems, combined with some of the vehicle technology options listed in Table I, are now considered.
FIGURE 4 Well-to-pump energy efficiencies of fuel production pathways...Read More