CC BY-NC-ND
0ELSEVIER
ISEHP 2016. International Symposium on Enhancing Highway
Transportation Research Procedía
Volume 15, 2016, Pages 749-760
Performance
Life Cycle Emissions and Cost Study of Light Duty
Vehicles
Panos D. Prevedouros1 and Lambros K. Mitropoulos1
1 University of Hawaii at Manoa, Honolulu, Hawaii, USA pdp@hawaii. edu, lampros@hawaii.edu
Abstract
The growth of vehicle sales and use world-wide requires the consumption of significant quantities of energy and materials. Advanced propulsion systems and electric drive vehicles have substantially different characteristics and impacts. For a comprehensive comparison of advanced and traditional light duty vehicles, a model is developed that integrates external costs, including emissions and time losses, with societal and consumer life cycle costs. Life cycle emissions and time losses are converted into costs for seven urban light duty vehicles. The results, which are based on vehicle technology characteristics and transportation impacts on environment, facilitate vehicle comparisons and support policy making in transportation. More sustainable urban transportation can be achieved in the short term by promoting policies that increase vehicle occupancy. In the intermediate term, more sustainable urban transportation can be achieved by increasing the share of hybrid vehicles in traffic. In the long term, more sustainable urban transportation can be achieved with the widespread use of electric vehicles. A sensitivity analysis of life cost results revealed that vehicle costs change significantly for different geographical areas depending on vehicle taxation, and the pricing of gasoline, electric power and pollution. Current practices in carbon and air quality pricing favor oil and coal based technologies. However, increasing the cost of electricity from coal and other fossil fuels would increase the variable cost for electric vehicles, and would favor the variable cost of hybrid vehicles.
Keywords: vehicle emissions, life cycle cost, alternative fuel vehicles, societal cost.
The growth of vehicle sales and use internationally requires the consumption of significant quantities of energy and materials, and contributes to the deterioration of air quality and climate conditions. In 2011, the transportation sector accounted for 28% of carbon dioxide (CO2) equivalent emissions produced by fossil fuels; the majority of these emissions came from light duty vehicles (EPA, 2012). In 2008, cars accounted for 55% of the 247 million light duty vehicle fleet in the U.S. (Davis et al., 2012). The high demand for personal mobility leads to a high consumption of petroleum distillates. Petroleum is a non-
Selection and peer-review under responsibility of the Scientific Programme Committee of ISEHP 2016 749
© The Authors. Published by Elsevier B.V.
doi: 10.1016/j.trpro.2016.06.062
1 Introduction
renewable source; it accounted for 92.8% of all transportation energy sources in 2011 (Davis et al., 2012). These facts highlight the connections among mobility, environment and energy.
Two promising factors that have the potential to alter the increasing trend of energy consumption and emissions are improvements in fuel economy due to high fuel prices and regulations, and electric drive systems for light duty vehicles. Between 1998 and 2008, vehicle fuel economy improved every year by an average of 0.5% in the U.S. (Davis et al., 2011) and the trend accelerated after the long (2009-2010) economic recession and the oil price "spike" of 2008-2009. CAFE, the Corporate Average Fuel Efficiency requirement, set a pre-target of 35.5 miles per gallon by 2016 (Gehm, 2012). While CAFE regulations aim to diminish fuel consumption and environmental impact from road vehicles, the reduced cost of driving (i.e., fuel expenditures) may lead to increased vehicle utilization.
Sustainable transportation planning should integrate CAFE regulations with a policy package of pricing measures, which are dynamically linked to vehicle characteristics and transportation impacts on environment (climate change and air quality), and reflect the full cost of driving to society.
In 2014, 100,000 plug-in electric vehicles were sold; nearly twice as many as sold during 2012. The introduction of electric and alternative fuel vehicles in metropolitan areas necessitates study and comparison of these vehicles with traditional gasoline and diesel vehicles. Subsidies and preferential treatment for certain types of vehicles should be supported by analysis that reveals the full impact on society. An assessment of transportation efficiency should include both monetary costs and external costs in the social and environmental domains (Lawrence and Kornfield, 1998). To this end, an accounting model that integrates vehicle life cycle emissions and costs is developed. Life cycle emissions and cost analysis reveal the impacts of different light duty vehicles on society.
Societal and consumer life cycle cost (LCC) studies and life cycle emissions estimations for various transportation vehicle types formed the foundation of the proposed methodology. Ogden et al. (2004) and Delucchi (2003) considered alternative vehicle technologies, including engine and fuel options. An essential undertaking of these studies was the level of detail of vehicle components for performing life cycle analysis. Ogden et al. (2004) formulated strategies towards the car of the future by estimating societal LCCs. They compared alternative fuel vehicles with a base vehicle and accounted for uncertainty using a range of possible conditions. Goedcke et al. (2007) focused on internal combustion engine, hybrid electric vehicles, and different fuel types to estimate societal and consumer LCC for Thailand by providing estimates relative to a base vehicle. Delucchi (2003) and Goedcke et al. (2007) defined societal LCCs as the sum of vehicle initial cost and fuel cost excluding tax, and external costs from pollution. Ogden et al. (2004) added oil supply insecurity.
This paper describes a dynamic model for estimating life cycle emissions and costs for existing different vehicle types. The model provides a detailed life cycle analysis of vehicles and explicitly associates emissions with travel at different urban speeds. Both direct and indirect costs are modeled separately as societal and consumer life cycle costs or LCC. In this model LCC are broadened to include indirect costs such as damage to health through air pollution (a societal cost) and loss of productivity through loss of time for users (a consumer cost). Time loss for maintaining and fueling/charging vehicles differs between vehicle technologies and it is often neglected in the comparisons of transportation vehicles. To explore different policy effects and technological improvements, users can control variables such as the loss of time.
The model focuses on seven urban light duty vehicles and three fuel types, including gasoline, electricity and hydrogen. A sensitivity analysis on variables with the largest impact on societal and consumer LCC is conducted to test the sensitivity of the results to assumptions. The method is useful not only for research but also for guiding short, intermediate and long term decision making for sustainable transportation planning.
2 Estimation of Life Cycle Emissions and Costs
The methodology for estimating societal and consumer LCC of urban light duty vehicles is summarized in Figure 1.
Figure 1. Methodology for estimating societal and consumer life cycle costs
The rationale for estimating the social and consumer LCC per vehicle type differ; therefore the total values cannot be considered cumulatively. Societal LCC include the present value of i) Vehicle first cost, ii) Lifetime operation costs including fueling, insurance and maintenance costs. Taxes for operational costs are excluded. Lifetime external costs include air pollutants and GHG emissions.
Consumer LCC include the present value of i) Vehicle retail cost including tax, ii) Lifetime operation cost from the time of vehicle purchase to the time of scrapping, including fueling, maintenance, taxes, insurance, registration and driving license costs, and iii) Time losses for vehicle refueling and maintenance.
Oil supply security costs are not included in the model as these vary widely by geography and various temporary influences. The base year of costs and vehicle characteristics is 2011 and all conversions were based on the U.S. Consumer Price Index.
2.1. Vehicle Assumptions
This study uses specific vehicle characteristics to estimate the absolute life cycle emissions and costs of seven vehicle types. Vehicle type refers to vehicle propulsion technology (e.g., internal combustion or electric), and basic functionality (e.g., car, van, light-truck.) The estimation of absolute LCC provides a more detailed comparison among light duty vehicles. The life cycle analysis for emissions and costs provide the model for estimating the total impact in monetary terms of any fleet mix scenario containing the following seven vehicle types: 1) Internal Combustion Engine Vehicle or (ICEV) , 2) Hybrid Electric Vehicle (HEV), 3) Fuel Cell Vehicle (FCV), 4) Electric Vehicle (EV), 5) Plug-In Hybrid Electric Vehicle (PHEV), 6) Gasoline Pickup Truck (GPT), 7) Gasoline Sports Utility Vehicle (GSUV). The most representative vehicle of each type was selected, i.e., the vehicle with the highest annual sales in its
category. Identifying specific vehicles was necessary for extracting impacts based on specific vehicle characteristics. A summary of vehicle parameters and assumptions is shown in Table 1 (Edmund's, 2011; Nissan, 2014; Toyota, 2014; EIA, 2012).
Diesel engine powered light-duty vehicles were not considered in this sustainability assessment due to the low penetration of such vehicles in the U.S. market. Light-duty diesel vehicles total approximately 800,000 compared with 2.3 million hybrid vehicles (Paula 2013). Hybrid vehicles are only about 3% of the U.S. light-duty vehicle fleet. Serendipitously this decision saved us the embarrassment of reporting unrealistic estimates for diesel light duty cars because the VW Golf/Jetta are the most popular model in this category. They would have been the chosen representative vehicle in our sustainability assessment. In September 2015 it was revealed that millions of VW diesel vehicles were equipped with "defeat devices" that managed engines for low pollutant generation in static government tests; e.g., NOx emissions were up to 35 times higher in actual driving conditions (Wikipedia, 2015).
Table 1. Vehicle characteristics
units ICEV HEV FCV EV PHEV GPT GSUV
Weight lbs 3,307 3,042 3,582 3,500 3,781 5,319 4,509
Average occupancy passengers 1.15 1.15 1.15 1.15 1.15 1.10 1.41
Average lifetime years 10.6 10.6 10.6 10.6 10.6 10.6 10.6
Average annual usage miles 11,300 11,300 11,300 11,300 11,300 11,300 11,300
Fuel efficiency mpg (city)1 22 48 72 94 35 15 17
Fuel price2 $ per U.S. gallon $3.48 $3.48 $5.413 $0.124 $3.48 $3.48 $3.48
Fuel taxes $ per U.S. gallon $0.41 $0.41 $1.10 $0.00 $0.41 $0.41 $0.41
Vehicle occupancy rates were adjusted to reflect vehicle occupancy in urban environments (TRB, 2010). For consistency in calculating annual fuel consumption and LCC, all vehicles are assumed to operate in an urban environment and have the same annual mileage and lifetime.
2.2. Vehicle First, Retail and Operation Costs
The term vehicle first cost is defined as the sum of vehicle body and drive train cost (Ogden et al., 2004). Vehicle first cost estimation for each vehicle type is based on the percentage of first cost to the vehicle retail cost for mass production. The estimated first costs for an ICEV, a HEV and a FCV based on the literature (Ogden et al., 2004) account for 14.3%, 17.6% and 17.7%, respectively of their final retail cost in 2011$. Therefore, the factors of 0.14 and 0.18 were used to convert final retail costs to first costs for gasoline based and alternative fuel vehicles, respectively.
The final retail cost that is used as a fraction of vehicle consumer LCC is equal to the Manufacturer Suggested Retail Price (MSRP) plus the shipping cost, multiplied by the average sales tax rate. A 6% tax rate for all vehicle types was assumed in this analysis; it includes all state and local taxes. The shipping cost (destination charge) is based on vehicle weight using a shipping cost of 0.22$/lb in 2011$.
For fuel cell technology, the Honda Clarity FCV is available for leasing only, at a cost of $600 per month for 36 months including maintenance and insurance. Since a final retail cost is not available for a FCV, its market price, when it will be mass produced, is estimated by matching the lease cost of the FCV
1 Miles per gallon equivalent (mpge) is used to describe the fuel efficiency of alternative fuel vehicles (i.e., FCV, EV and PHEV); U.S. gallons.
2 Fuel prices include taxes and are based on U.S. average prices for the year 2011 (EIA, 2012).
3 Hydrogen cost is given in $ per kg. FCV is 2.5 times as efficient as the ICEV under average driving conditions (Ogden et al., 2004).
4 Electricity cost is given in $ per kWh. Electricity is not taxed, at least in the near-term, because is considered clean fuel (Davis et al., 2012).
to a conventional vehicle with both leasing and purchasing options. The resultant MSRP is $39,000 in 2011$.
2.3. Emission Costs
The life cycle emissions of light duty vehicles are monetized by using recognized external costs. External costs are extracted from the European Commission's study Externalities of Energy (ExternE, 2004) which converts external effects into monetary units of external costs.
ExternE calculates the damage attributable to each emitted pollutant. Economic evaluation of air pollutants was made based on two sets of variables, urban and rural external costs. Rural external costs were used to estimate the cost of manufacturing and fuel chain-related air pollutants because these emissions usually occur away from urban areas. The ratio of rural-to-urban values was estimated based on an extension of the ExternE study (Lane, 2006). The average values from ExternE for the European Union were used to evaluate the external cost of air pollutants.
The air quality external cost is calculated directly from the emissions inventory of air quality pollutants and their cost per unit, as follows:
Caq is the air quality external cost in $ per mile, p, is the emission of pollutant i in grams per mile, e, is the external cost of emission of pollutant i in $ per gram. Damages associated with direct vehicle emissions from a typical new car over its lifetime were estimated to be $2,464.
CO2 contributes to global warming; damages due to global warming are referred to as the social cost of carbon emissions. Three pollutants were combined to show the impact of GHGs: CO2, methane (CH4) and nitrous oxide (N2O). Estimation of climate change damage costs includes large uncertainties. By considering different discount rates and goals, lower and upper damage cost estimates are around $12 per metric ton of carbon (tC) and $350 per tC (ExternE, 2004).
The marginal damages caused by a metric ton of CO2 emissions in the near future were estimated at $5-$125 per tC (Tol, 2005). Muller et al. (2011) used an estimate of $27 per tC as a central value for the U.S. economy. In our analysis the value of $27 per tC was adopted for CO2 and other GHGs.
Global Warming Potential (GWP) factors have been used to assign weights to GHGs in units of CO2 emissions. The GHG external cost is calculated by multiplying the emissions inventory associated with GHGs and their unit costs as follows:
CGHG is the GHG external cost in $ per mile, pj is the emission of GHG pollutant j in grams per mile and ej is the external cost of GHG pollutant j in $ per gram. ej is estimated by multiplying the GWP of GHG pollutant j by the external cost of CO2 emissions in $ per gram.
2.4. Fueling and Maintenance Time Costs
Trip time is an important factor in mode choice with social and economic impacts, as shown in studies that monetized user time loss during congested conditions (CE Delft, 2008) and road construction works or incidents. Introduction of advanced vehicle technologies with improved fuel consumption such as hybrids, fuel cell or electric vehicles reduce the fueling frequency and require different type of fuels and infrastructure to accomplish refueling. In past studies, the fueling or charging time usually is not considered in the estimation of the total user time to use a vehicle over its lifetime. Fueling time is a criterion that is used in our analysis. The time cost refers to the time a vehicle user spends to fuel or charge a vehicle over its lifetime. Time loss reflects the loss of productivity. The fueling frequency is calculated as follows:
(eq. 1)
(eq. 2)
Lifetime miles traveled .
Fueling frequency =--(eq.3)
Fuel tank x Vehicle fuel efficiency
For the estimation of the time loss, it is assumed that it takes an average duration of six minutes for each user to complete the fueling procedure (i.e., to enter the fuel station, wait, fuel, pay and leave the fuel station). In the EV case, the fuel tank is substituted by the Li-Ion battery. Time losses for an EV user are estimated based on the assumption that 26 minutes are required to charge a depleted Li-Ion battery to compete the required trip to a charger at home or work (Nissan, 2014), and this event will occur for 5% of the total charging cycles in urban driving conditions during a year. For the rest of the overnight charging cycles it is assumed that no time is wasted by users for charging batteries.
The maintenance frequency for parts replacement but not inspection of a gasoline vehicle during its lifetime is estimated to be 22 times and each owner is assumed to lose two hours per time for dropping-off and picking-up the vehicle (Toyota, 2014). Maintenance frequency for HEV, FCV, EV and PHEV is 20, 11, 10, and 11 times respectively, due to the reduced number of parts that require replacement for each vehicle type. Time cost is estimated by multiplying time loss by the mean hourly U.S. wage of $21.74 per hour in 2011$.
The estimation of present worth of costs that will take place in future years is made with the present value of an ordinary annuity (PVA), which is the value of expected future payments that have been discounted to a single equivalent value today (Graham, 2010). The nominal interest rate is assumed to be 5.0% and the inflation rate is assumed to be 2.5%.
2.5. Life Cycle Analysis for Vehicle Emissions
The Greenhouse Gases, Regulated Emissions and Energy Use in Transportation (GREET) models, the MOBILE6.2 model and the Economic Input-Output Life Cycle Assessment (EIO-LCA) were used to quantify emissions (CTR, 1998, 2005; EPA, 2003; Hendrickson et al., 2006).
Manufacturing. Manufacturing emissions and energy in GREET include vehicle materials, batteries, fluids and vehicle assembly. Specific input assumptions related to each vehicle and its components are extracted from the manufacturer specifications of each vehicle. Additionally, two battery replacements are included for the ICEV, the GPT and the GSUV, one for the HEV and none for the EV, the FCV and the PHEV to reflect FreedomCAR Program Research and Development goals of a 15 year lifetime with one battery (CTR, 2006).
Fueling. GREET is used for the fuel life cycle. The model estimates the emissions and energy associated with primary energy production (feedstock recovery), transportation and storage, and with fuel production, transportation, storage and distribution. The fuel production option for conventional gasoline and low sulfur diesel is petroleum. Gaseous hydrogen is produced from natural gas via steam methane reforming at refueling stations. For electricity generation the following mix is assumed: Coal 50.4%, nuclear power 20.0%, natural gas 18.3%, residual oil 1.1%, biomass 0.7%, other 9.5% (i.e., hydro, solar, wind and geothermal).
Operation. MOBILE 6.2 and GREET were used to obtain estimates for all vehicle types in the stage of operations (i.e., usage.) The average speed of 28 miles per hour was used for passenger vehicles used on U.S. city streets and highways (TTI, 2009). GREET was used to estimate emissions for alternative fuel vehicles (i.e., FCV, EV and PHEV).
Idling emissions were estimated based on the assumption that the 2.5 mph emission factors can be applied to the entire idling time. Our study assumed that the average light duty vehicle idles for 7.5 minutes per day (EPA, 2003).
Fixed costs for vehicle usage include insurance, license fees and taxes. EIO-LCA estimates the required materials and energy resources, and the environmental emissions resulting from activities in the economy. Finance charges were assumed to have negligible impacts to the environment. The annual
insurance cost for an ICEV is estimated to be $974 (AAA, 2011). Insurance cost is included in both societal and consumer LCC calculation. License, registration and taxes costs include all governmental taxes and fees payable at time of purchase, as well as fees due each year to keep the vehicle licensed and registered. Vehicle annual registration, driving license, and taxes for an ICEV are estimated to be $591 (AAA, 2011). These costs are not included in societal LCC calculation. Insurance, annual registration, driving license, and taxes costs for other vehicle types are extrapolated from vehicle weights. Maintenance. Vehicle maintenance includes the maintenance and disposal of vehicle parts. GREET models the emissions associated with vehicle disposal processes including vehicle recycling. EIO-LCA models the emissions inventory associated with automotive mechanical repair and maintenance and tire manufacturing services based on costs. The maintenance costs of the passenger vehicles are estimated based on ICEV maintenance cost of $0.0432 per mile (2011$). The EV's maintenance requirements are 50% less than the costs for an ICEV (Delucchi, 2000), thus it estimated to be $0.0216 per mile. It is estimated that the maintenance cost for an HEV is $0.0396 per mile (Duvall, 2002). The maintenance cost for a PHEV based on scheduled maintenance costs using average driving schedule and night charging is estimated to be $0.0304 per mile (Duvall, 2002). The maintenance costs of the FCVs are assumed to be equal to the EV maintenance costs when FCVs become mass produced. Tire cost for ICEV, HEV, FCV, EV and PHEV is $0.0113 per mile (2011$). Per mile maintenance and tire cost for the GSUV and the GPT is $0.0488 and $0.0127, respectively (AAA, 2011).
3 Results and Discussion 3.1. Life Cycle Emissions
Life cycle emissions are weighted per passenger mile travel (PMT) as shown in Table 2 to account for urban vehicle occupancy and people trips. Accounting by PMT is critical when carpools and buses are compared. The results show that GSUV emissions are approximately equal to ICEV emissions due to GSUV's higher vehicle occupancy. The analysis shows that transportation policies which focus on increasing vehicle occupancy have the potential to reduce the emissions per PMT significantly while supporting personal mobility. Such policies include carpooling, car sharing, high occupancy vehicle (HOV) and high occupancy toll (HOT) lanes. Vehicle occupancy related policies may be implemented at a faster pace than shifting to alternative fuel vehicles.
SOx and PM10 emissions are higher for the EV compared with all other vehicles, mostly due to the sources and raw materials used to produce electricity. Alternative fuel technologies, including the PHEV and the EV, have higher SOx emissions than gasoline vehicles. This is due to the fabrication of materials for the traction motor, electronic controller and generator.
Table 2. Total Emissions per Vehicle Type in grams per PMT
ICEV HEV FCV EV PHEV GPT GSUV
CO2 534.2 278.1 260.0 334.4 466.3 762.0 532.6
CH, 0.806 0.503 0.942 0.641 0.622 1.185 0.815
N2O 0.018 0.015 0.004 0.006 0.016 0.022 0.016
GHGs 559.5 295.0 284.3 351.9 486.4 797.8 557.6
VOC 0.945 0.848 0.088 0.082 0.848 1.711 0.824
CO 6.854 6.800 0.419 0.388 6.874 11.376 6.182
NOx 0.856 0.725 0.248 0.393 0.793 1.520 0.848
PM!0 0.166 0.131 0.195 0.479 0.273 0.246 0.169
SOx 0.352 0.331 0.445 0.940 0.531 0.523 0.357
Note: Carbon dioxide (CO2), Methane (CH4 ), Nitrous oxide(N2O), greenhouse gas (GHG), Volatile organic compound (VOC), Carbon monoxide (CO), Nitrogen oxides (NOx), Particle matter with diameter less than 10 ^m (PM10), Sulphur oxides (SOx)
3.2. Societal and Consumer Life Cycle Costs
The absolute values for the societal and consumer LCCs for each vehicle type are presented in Table 3. Externalities account for 14% of the societal LCC of a GPT (highest share) and 6% for the FCV (lowest share). Vehicle rankings based on externality costs may change when low externality costs are considered. Relative values on externalities, most of which are determined by society, will likely influence vehicle choice, and transportation policies that aim to promote alternative fuels and low pollution sources of energy. The high externality costs for gasoline fueled vehicles suggest that additional taxes should be applied to these vehicle types for driving them in urban environments where low pollution alternatives are both available and competitive. Externalities for the PHEV account for 13% of its societal LCC. Its environmental impact is affected in large part by emissions generated during the fuel cycle of gasoline production and electricity generation. Utilization of low pollution sources to generate electricity for PHEV and EV reduces their externalities.
Table 3. Societal (top) and consumer (bottom) life cycle costs in 2011$
ICEV HEV FCV EV PHEV GPT GSUV
First cost 3,378 4,976 7,421 6,636 7,375 3,630 4,428
Fuel cost excl. tax 14,503 6,647 7,460 3,131 4,465 21,271 18,768
GHGs 1,797 947 907 1,129 1,563 2,462 2,195
Air quality 2,464 2,391 806 1,764 2,653 3,805 2,814
Operation cost excl. tax 14,219 13,176 12,627 12,418 15,198 14,616 14,616
Societal Life Cycle Costs 36,361 28,137 29,220 25,078 31,255 45,784 42,821
ICEV HEV FCV EV PHEV GPT GSUV
Retail cost 24,164 28,866 34,771 30,644 34,892 25,962 31,674
Fuel cost 16,446 7,538 9,384 3,131 5,359 24,121 21,284
Operation cost 20,571 19,025 19,330 18,973 22,393 22,863 22,863
Time cost 1,387 1,152 1,340 899 1,375 1,449 1,585
Consumer Life Cycle Costs 62,569 56,581 64,825 53,647 64,019 74,396 77,405
Note: Estimations are based on vehicle lifetime of 10.6 years and annual mileage of 11,300.
Although the first cost of gasoline fueled vehicles (i.e., ICEV, HEV, GPT and GSUV) is lower compared with alternative fuel vehicles, the cost of externalities is lower for the FCV, the EV and the HEV. Additionally, the fuel cost before taxes increases for gasoline fueled vehicles due to their mechanical decay and corresponding loss of fuel efficiency over time. The FCV has higher fuel costs compared with the HEV.
Societal LCC can be reduced by either vehicle hybridization or by shifting to alternative fuel vehicles. A shift from ICEV to HEV would be less costly in the short term because hybrid technology already exists and additional fueling infrastructure is not needed. For policy makers, HEV is the most attractive vehicle as it provides personal mobility with the lowest societal LCC. In the long term, if the costs of alternative fuel vehicles and hydrogen decrease, then the EV and FCV have the potential to lower the societal LCC significantly.
The consumer LCCs presented in Table 3 show that the most attractive vehicles for consumers are the EV, the HEV and the ICEV. Due to the low cost of electricity (average national price), the EV is ranked first among the seven vehicle types. However, the high purchase cost and the lack of widespread infrastructure for charging result in low penetration rates. The low consumer LCC of the EV reveals its potential to be the car of the future when the infrastructure is in place. The assumption that the EV requires 5% of the total charging cycles per year to occur at an intermediate location increases its time cost. If EVs are used exclusively for short trips, and if the battery pack efficiency is enhanced, then time cost will be minimized and EVs will increase their lead in consumer LCC.
Although the FCV has a very low environmental impact, the lack of infrastructure for fueling, the expensive components that are required for its manufacturing and the price of hydrogen make it a less competitive vehicle in the short term. When the consumer LCC are combined with emissions costs, the FCV is estimated to cost $292 less than the ICEV. The fuel efficiency and lower emissions of the FCV compensate for its retail cost. For the FCV to compensate the consumer LCC and emission cost of a HEV, the price of hydrogen would have to be below $1.70 per kg, or the price for carbon emissions would have to be higher.
Since LCC appears to be less significant than retail cost to consumers when buying a vehicle, the objective should be to decrease the retail cost for vehicles with low environmental impact and LCC, including the FCV, the PHEV, the EV, and the HEV. This objective can be pursued with incentives including tax credits, fuel vouchers, parking policies, or high occupancy toll lanes and congestion or green zone pricing exemption. All of these are present in a number of cities to a varied degree.
4 Sensitivity Analysis
Estimated results in this study include a number of limitations in the proposed method. The estimates are based on published research and on built-in assumptions and equations in GREET, MOBILE and EIO-LCA models. A sensitivity analysis revealed how changes in the assumed parameters of vehicles (i.e., fuel consumption, emission costs, etc.) can change the final outcome. Monetary estimates include uncertainty and account for a (large) portion of the environmental and social impacts. The variables with the largest impact on societal and consumer LCC were identified and a sensitivity analysis was conducted to test the robustness of the conclusions, and the sensitivity of the results to stated assumptions.
4.1. Sensitivity of Emissions Cost
Emissions are monetized by using external costs that have inherent large uncertainties. This is due to the insufficient evidence of the effects of individual components of air pollution (Lane, 2006). Another source of uncertainty is associated with air quality models and the connection of emissions to ambient concentrations (Muller, 2011). Global warming and air quality impacts are estimated based on damage costs which, in turn, are uncertain and increase with increased population density.
Carbon cost Threshold values are approximately five times lower (i.e., $6 per tC) and three times higher (i.e., $65 per tC) than the "Medium" scenario considered in the LCC analysis for this study (Tol, 2005; Muller, 2011). Urban air quality costs in the ExternE study have been estimated for central Europe where the average population density is 80 people per km2. Based on population densities in the U.S., air
quality costs are decreased fivefold for the "Low" scenario and increased threefold for the "High" scenario. Figure 2 shows aggregated externality costs (carbon and air quality costs) for the three scenarios per vehicle type and life cycle stage.
In the "Low" scenario, the difference between the FCV and other gasoline based vehicles is reduced. Gasoline based vehicle are found to be emit most pollutants during the vehicle operation stage. However, alternative fuel vehicles such as the FCV and the EV emit more pollutants during the fuel stage and this is more apparent in the "High" scenario. Higher externality costs set the basis for transportation policies that should support more efficient and cleaner vehicle types. Improved fuel efficiency of gasoline vehicles will result in reduced lifetime emissions that will approach those of EVs or FCVs. The only difference between gasoline and alternative fuel vehicles will be the location and concentration where the pollutants are emitted. Electricity generation from renewable energy sources has the potential to lessen externality costs related to the generation of electricity for the EV and PHEV. EV and PHEV emissions vary based on regional data. For example, while the national average total CO2 emission rate (i.e., including production and distribution of electricity) for an EV is 190 grams per mile, based on Hawaii (HI) and California (CA) data the total CO2 emission rate changes to 260 and 120 grams per mile, respectively (DOE 2015). Differences in carbon pricing and air quality costs clearly affect investments on clean energy and low tC values favor gasoline/coal based technologies.
4.2. Sensitivity of Fuel Price
Fuel prices make up roughly one third of societal and one quarter of consumer LCC as shown in Table 3, and they are uncertain due to different prices in the various states in the U.S. In this analysis the minimum and maximum fuel prices in the U.S. generate the "Low" and "High" scenarios.
The minimum and maximum values per gallon of gasoline in U.S. were found to be $2.93 and $4.13 (EIA, 2012). The electricity cost of $0.0786 per kWh in Idaho and $0.3656 per kWh in Hawaii were used (EIA, 2012). Hydrogen is estimated to cost $4.63 and $6.05 per kg including taxes for the "Low" and "High" scenarios, respectively (DOE, 2015). All pricing values shown above are for 2011.
Variable costs per vehicle type including operation and fueling are shown in Figure 3 for the "Medium" scenario for the societal and consumer LCC. The range of fuel prices for the "Low" and "High" scenarios are shown with range bars. Low to medium fuel costs favor the EV; however high fuel costs increase the variable cost for EV. In the "High" scenario, the PHEV and the HEV have the lowest cost and they are "the best vehicle" for consumers and policy makers since they do not need an extensive network of infrastructure to support their operation. High fuel costs do not support EV in the market. EVs are among the most environmental friendly vehicles identified in this study; regions with high electricity pricing should reexamine existing policies to minimize their environmental impact.
5 Conclusion
The model presented in this study was used to assess and compare life cycle emissions and costs of seven urban light duty vehicles with different propulsion technology. The method captures the different vehicle life cycle pollutants, and the resultant societal and consumer life cycle costs associated with each vehicle type. Comparisons are enabled by internalizing externalities including emissions and time losses.
Emissions per PMT revealed that reduction of emissions is feasible in the short term without relying solely on alternative fuel vehicles and their infrastructure which is incomplete or non-existent. The EV was found to have the lowest consumer LCC due to the low cost of electricity. The LCC analysis showed that the low cost of FCV externalities was offset by the high vehicle acquisition cost. The HEV has the second lowest societal and consumer LCC compared with all other six vehicle types. Its ranking makes it a strong candidate as a transitional technology. Its low LCC resulted from the low emission impact cost,
the improved fuel efficiency and the low manufacturing cost. In the short term, there are no barriers that should be overcome to increase the penetration of HEV in the market. Such barriers include infrastructure, maintenance and repair shops, and overall awareness and familiarity with alternative fuel systems. In the long term, electric drive vehicles seem to have the potential to reduce environmental impact. Combination of transportation policies and alternative fuel vehicles should support the creation of a sustainable transportation system. Policies should be focused on improving the fuel efficiency of vehicles and on lowering the purchase price of HEV while vehicle technologies advance.
A sensitivity analysis of life cost results revealed that vehicle costs change significantly for different geographical areas depending on vehicle taxation, gasoline, electric power and pollution pricing. Current practices in carbon and air quality pricing favor oil and coal based technologies. Increasing the cost of electricity produced from coal or other fossil fuels will increase the variable cost for electric vehicles, and will favor the variable cost of hybrid vehicles.
Life cycle cost of vehicles and fuels and sensitivity analysis estimate the true cost of transportation by private vehicle. Such analyses are an essential complement to CAFE regulations and other long term policy goals. The findings in this study strengthen the position that transportation policies should be dynamic to reflect changes in vehicle fleet and regional data, to support clean technologies, renewable energy sources and complement existing transportation regulations.
40000 -, -
20000 __ —— MlilM
fN 20000
— 10000
60000 50000 40000 30000 20000 10000
I I I ■ I
o > > > > >
M LL] LL] (_)
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I Fuel cost ■ Operation cost Fue| range
Figure 3. Operation and fuel LCC and fuel cost range per vehicle type.
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