Book Description

The US EPA and NHTSA jointly adopted greenhouse gas emission and fuel economy regulations for medium- and heavy-duty trucks. In the regulations, detailed advanced technology options are described with corresponding fuel economy and Greenhouse Gas (GHG) emission improvement goals. Alternative fuel/powertrains are the primary options available to satisfy the regulations.In this thesis, natural gas, electricity, and hydrogen fuels, as well as diesel-hybrid electric powertrains, are evaluated with respect to their fuel economy and cost. Detailed vehicle models were constructed for use with the ADVISOR models and typical driving cycles were used to simulate heavy-duty and medium-duty truck operation in urban and long haul applications. Breakeven fuel prices for various fuel/powertrain combinations were calculated and compared with reference fuel prices, in order to determine the economic attractiveness of each combination. Scenario based on Model Year (MY) 2010-2013 and projected MY 2025-2030 were developed in order to evaluate the current and future market potential for each fuel/powertrain combination. Using today's vehicle attributes (MY 2010-2013) for Class 8 trucks, the results indicated that CNG vehicles were more economically attractive than LNG vehicles for both conventional powertrains and hybrid-electric powertrains. For similar driving distances, CNG vehicles had slightly lower fuel economy than their LNG counterparts but a much lower initial cost difference because of the lower cost of CNG on-board gas storage. For medium-duty trucks, the economics results indicated that CNG conventional trucks are attractive in most urban applications for a broad range of VMT and payback time combinations. CNG-hybrid vehicles were attractive for annual travel less than 26,000 miles and paybacks of less than three years. The other fuel/powertrain combinations were not attractive because the fuel cost savings with fuels other than diesel did not compensate for the high initial cost differentials associated with the alternative powertrains. However, those EVs emit least GHG, reducing 35% and 45% CO2 emission compared to baseline vehicles, for heavy-duty and medium-duty vehicles, respectively.In the future scenarios (MY 2025-2030), future Class 8 trucks achieve 74% better fuel economy on average than today's vehicles (MY 2010-2013). The most economically attractive option for Class 8 trucks in the 2030 scenario was the diesel hybrid-electric. The natural gas conventional and natural gas hybrid-electric vehicles were also generally superior to the updated diesel technology, with the CNG SI vehicles being somewhat more attractive than the LNG vehicles. The fuel cell vehicles are attractive for most applications if the cost of hydrogen is less than about $5/kg. All the powertrains having low speed, electric drive capability are attractive for the port applications. For the medium-duty delivery trucks in 2030, the economics analyses indicated that most of the fuel/powertrain combinations were attractive with the advanced technologies, primarily due to the reductions in the component costs. The fuel cell trucks are economically attractive for almost all applications if the cost of hydrogen is less than about $6/kg. The CNG conventional and hybrid-electric trucks are also attractive under a number of circumstances especially in urban applications. Even the battery powered trucks are economically viable for a three year payback and electricity less than about 12 cents/kWh in urban applications. These results indicate that it is valuable to start investing in alternative fueled vehicles now with a view toward the future. Natural gas vehicles, especially those using compressed gas storage, are good alternative options in the short-term. Given expected technology and cost improvements in batteries and fuel cells, in the long run electric and fuel cell vehicles are the most promising future fuel/powertrain options.