Analysis of the fuel economy benefit of drivetrain hybridization

Parallel- and series-configured hybrid vehicles likely feasible in next decade arc defined and evaluated using NREL's flexible ADvanced VehIcle SimulatOR ADVISOR. Fuel economics of these two diesel-powered hybrid vehicles are compared to a comparable-technology diesel- powered internal-combustion-engine vehicle. Sensitivities of these fuel economies to various vehicle and component parameters are determined and differences among them are explained. The fuel economy of the parallel hybrid defined here is 24% better than the internal- combustion-engine vehicle and 4% better than the series hybrid

Challenges and Potential Solutions for Reducing Climate Control Loads in Conventional and Hybrid Vehicles

The National Renewable Energy Laboratory, a U.S. Department of Energy national laboratory, is collaborating with U.S. automotive manufacturers to develop innovative techniques to reduce national fuel consumption and vehicle tailpipe emissions by reducing vehicle climate control loads. A new U.S. emissions test, the Supplemental Federal Test Procedure (SFTP), will soon begin measuring tailpipe emissions with the air conditioning system operating. Modeled results show that emissions of oxides of nitrogen (NOx) and carbon monoxide (CO) more than double during the air conditioning part of the SFTP. Reducing the transmittance of the glazing can have a greater impact on the cabin soak temperature than ventilating the vehicle during a hot soak. Reducing the amount of outside air can decrease cooling and heating loads but requires that the recirculated air be cleaned. We discuss a photocatalytic oxidation air-cleaning process for removing volatile organic compounds and bioareosols. We conclude with an example of modeling the thermal comfort of the occupants. An auxiliary load increase of only 400 Watts (W) results in a 0.4 km/L (1 mpg) decrease for a conventional 11.9-L/100-km (28-mpg) vehicle. If every vehicle in the United States were to save only 0.4 km/L (1 mpg), $4 billion (U.S. dollars) would be saved annually in gasoline and oil costs. Further information can be found at http://www.ctts.nrel.gov/auxload.html

Using an advanced vehicle simulator (ADVISOR) to guide hybrid vehicle propulsion system development

An advanced vehicle simulator model called ADVISOR has been developed at the National Renewable Energy Laboratory to allow system-level analysis and trade-off studies of advanced vehicles. Because of ADVISOR`s fast execution speed and the open programming environment of MATLAB/Simulink, the simulator is ideally suited for doing parametric studies to map out the design space of potential high fuel economy vehicles (3X) consistent with the goals of the Partnership for New Generation of Vehicles (PNGV). Five separate vehicle configurations have been modeled including 3 lightweight vehicles (parallel, series, and conventional drivetrains) along with 2 vehicles with 1996 vehicle weights (parallel and conventional drivetrains). The sensitivity of each vehicle`s fuel economy to critical vehicle parameters is then examined and regions of interest for the vehicles mapped out through parametric studies. Using the simulation results for these vehicles, the effect of hybridization is isolated and analyzed and the trade-offs between series and parallel designs are illustrated

The detection efficiency of Type Ia supernovae from the Zwicky Transient Facility: limits on the intrinsic rate of early flux excesses

International audienceSamples of young Type Ia supernovae have shown ‘early excess’ emission in a few cases. Similar excesses are predicted by some explosion and progenitor scenarios and hence can provide important clues regarding the origin of thermonuclear supernovae. They are, however, only predicted to last up to the first few days following explosion. It is therefore unclear whether such scenarios are intrinsically rare or whether the relatively small sample size simply reflects the difficulty in obtaining sufficiently early detections. To that end, we perform toy simulations covering a range of survey depths and cadences, and investigate the efficiency with which young Type Ia supernovae are recovered. As input for our simulations, we use models that broadly cover the range of predicted luminosities. Based on our simulations, we find that in a typical 3 d cadence survey, only ∼10 per cent of Type Ia supernovae would be detected early enough to rule out the presence of an excess. A 2 d cadence, however, should see this increase to ∼15 per cent. We find comparable results from more detailed simulations of the Zwicky Transient Facility surveys. Using the recovery efficiencies from these detailed simulations, we investigate the number of young Type Ia supernovae expected to be discovered assuming some fraction of the population comes from scenarios producing an excess at early times. Comparing the results of our simulations to observations, we find that the intrinsic fraction of Type Ia supernovae with early flux excesses is |$\sim 28^{+13}_{-11}{{\ \rm per\ cent}}$|⁠

The detection efficiency of Type Ia supernovae from the Zwicky Transient Facility: limits on the intrinsic rate of early flux excesses

Samples of young Type Ia supernovae have shown ‘early excess’ emission in a few cases. Similar excesses are predicted by some explosion and progenitor scenarios and hence can provide important clues regarding the origin of thermonuclear supernovae. They are, however, only predicted to last up to the first few days following explosion. It is therefore unclear whether such scenarios are intrinsically rare or whether the relatively small sample size simply reflects the difficulty in obtaining sufficiently early detections. To that end, we perform toy simulations covering a range of survey depths and cadences, and investigate the efficiency with which young Type Ia supernovae are recovered. As input for our simulations, we use models that broadly cover the range of predicted luminosities. Based on our simulations, we find that in a typical 3 d cadence survey, only ∼10 per cent of Type Ia supernovae would be detected early enough to rule out the presence of an excess. A 2 d cadence, however, should see this increase to ∼15 per cent. We find comparable results from more detailed simulations of the Zwicky Transient Facility surveys. Using the recovery efficiencies from these detailed simulations, we investigate the number of young Type Ia supernovae expected to be discovered assuming some fraction of the population comes from scenarios producing an excess at early times. Comparing the results of our simulations to observations, we find that the intrinsic fraction of Type Ia supernovae with early flux excesses is ∼28+13−11 per cent⁠