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The economics of the transition to fuel cell vehicles with natural gas, hybrid-electric vehicles as the bridge
Research in Transportation Economics 52 (2015) 65e71
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Research in Transportation Economics journal homepage: www.elsevier.com/locate/retrec
The economics of the transition to fuel cell vehicles with natural gas, hybrid-electric vehicles as the bridge Andrew Burke*, Lin Zhu Institute of Transportation Studies, University of California, One Shields Ave., Davis, CA 95616, USA
a r t i c l e i n f o
a b s t r a c t
Article history: Available online 21 November 2015
Detailed comparisons are made between various types of light-duty vehicles fueled with natural gas and hydrogen. Natural gas vehicles are designed as charge sustaining hybrid vehicles (HEV) and hydrogen fueled vehicles (FCV) are powered by a fuel cell. All the vehicles have a range of 400 miles between refueling stops. This paper is concerned primarily with the near-term time period in which the fuel cell technology is maturing and the hydrogen infrastructure is being constructed both with respect to refueling stations and the source of the hydrogen being distributed. Detailed computer simulations are presented for vehicle classes from compact cars to mid-size SUVs. Energy (MJ) and volume (L) of fuel storage required to meet the 400 mile range target for each vehicle using natural gas and hydrogen are compared. Costs of the vehicles simulated are projected for 2015e2030. Cost results indicate that the costs of ownership of the natural gas HEVs and the hydrogen fuel cell vehicles become close in the 2025 e2030 time period. CO2 emissions from natural gas fueled hybrid and fuel cell vehicles are calculated and compared for hydrogen and electricity from natural gas. Ways in which the introduction of the natural gas fueled vehicles could be a bridge to the mass marketing of fuel cell vehicles are discussed. © 2015 Published by Elsevier Ltd.
JEL classification: Q2 Q3 Q4 Keywords: Natural gas Hydrogen Hybrids Fuel cells Costs Markets Transitions
1. Introduction There is considerable interest (Cannon, 2012; Hefner, 2009; Nuboer, 2010; Wokaun and Wilhelm, 2011) in increasing the use of natural gas as a fuel in the transportation sector primarily because it has a lower carbon intensity (gmCO2/MJ) than either gasoline or diesel fuel. Presently (2014) most of the activity in this area in the United States is concerned with the use of natural gas in heavy- and medium duty trucks and transit buses. However, there is much greater interest in using natural gas for light-duty passenger cars, SUVs, and pick-up trucks in Europe and Asia as a means of reducing tail-pipe emissions such as CO, HC, and particulates. This has resulted in the European car manufacturers providing a number of models that can operate on natural gas and gasoline depending on which fuel is available. Italy has provided financial incentives for car buyers to purchase natural gas fueled vehicles (LeFevre, 2014). As a result, Fiat markets a relatively large number of models that are natural gas fueled and Italy has over 75% of the natural gas cars in Europe. There are presently less than 600 natural
* Corresponding author. Tel.: þ1 530 752 9812. E-mail address: [email protected] (A. Burke). http://dx.doi.org/10.1016/j.retrec.2015.10.005 0739-8859/© 2015 Published by Elsevier Ltd.
gas refueling stations in the United States and over 4000 stations in Europe. There is, however, considerable discussion of the use of hydrogen fuel cells in light-duty vehicles in North America, Europe, and Asia. In fact, several auto manufacturers are planning (Baker, 2015; Pfanner, 2015) to begin marketing fuel cell vehicles in 2015. One of the impediments to marketing fuel cell vehicles is the lack of an extensive infrastructure for the hydrogen fuel. In addition, there is uncertainty regarding the acceptance of the public of the use of a gaseous fuel in their vehicles. In the past, there has been considerable discussion (Parish, 2005; Pfanner, 2015) of the use of natural gas in light-duty vehicles as a bridge to the use of hydrogen in vehicles. One of the reasons this discussion has not been taken seriously in the United States has been the lack of success in the marketing the few natural gas vehicle models that have been offered for sale. Annual sales of the Honda Natural Gas (GX) Civic were only 2198 vehicles in 2013 and only 781 in 2014. This leads Honda to discontinue sales of the GX Civic after 2015. These vehicles were retrofits of gasoline fueled Honda Civic models to accommodate natural gas as the fuel. Because the volume of the natural gas tank is much larger than the gasoline tank, part of the trunk of the retrofitted vehicle is taken up by the natural gas tank. Even then, the range of the natural gas vehicle is significantly less
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than that of the gasoline fueled model. In addition, the price of the natural gas model was significantly higher ($5e6 K) than the standard gasoline model. Hence it was not surprising that sales of the natural gas model were very low. The questions addressed in this paper are whether light-duty vehicles designed from the ground-up to use gaseous fuels could be marketed successfully as natural gas vehicles and further how they would compare in the near-term with hydrogen fuel cell vehicles using the same chassis design to accept hydrogen storage tanks. In this way, natural gas vehicles could serve as a bridge to public acceptance and the mass marketing of fuel cell vehicles in the United States and Europe as their price becomes lower and the hydrogen infrastructure is developed. The wide availability of natural gas and its projected relatively low price (U.S. EIA, 2013) into the future compared to gasoline makes the strategy of marketing natural gas vehicles a reasonable possibility. As discussed in Cannon (2012), Hefner (2009), Parish (2005), Lee, Zinman, and Logan (2012), there are synergies between fueling stations for compressed natural gas and hydrogen, which should reduce the cost of providing the hydrogen infrastructure especially in the early stages of the introduction of fuel cell vehicles. For example, both stations would require the delivery via a pipeline of natural gas and a means of compressing and storing the gaseous fuel at high pressure. In this paper, detailed comparisons are made between various types of light-duty vehicles fueled with natural gas and hydrogen. The natural gas vehicles are designed as charge sustaining hybrid vehicles (HEV) and the hydrogen fueled vehicles (FCV) are powered by a fuel cell. All the vehicles have a range of 400 miles between refueling stops. Schematics of the powertrain of the CNG hybrid and hydrogen fuel cell vehicles are shown in Fig. 1. Both vehicles are electrified and use a small battery to increase the driveline efficiency. In the charge sustaining hybrid vehicle, the battery state-ofcharge is maintained in a near range do to charging from the
generator connected to the engine. Hence both vehicles are fueled by the gaseous fuels and not from the wall-plug. The paper discusses the on-board storage of natural gas (3600 psi) and hydrogen (10,000 psi) in terms of the volume, weight, and cost of the tanks required and how fuel storage affects the vehicle design. Detailed computer simulations of the vehicles are presented for several driving cycles and the energy (MJ) and volume (L) of fuel required to meet the 400 mile range target for each vehicle using natural gas and hydrogen are compared. The costs of the vehicles simulated are projected for 2015e2030. The differences between the costs of the natural gas hybrid vehicles and the fuel cell vehicles are calculated for the various vehicle types as the cost of the fuel cells, batteries and other powertrain components decrease in the future. The annual ownership costs of the vehicles are also calculated. The CO2 emissions from the CNG hybrid and hydrogen fuel cell vehicles are determined and compared. As a final step, the ways in which the introduction of the natural gas fueled vehicles could be a bridge to the mass marketing and infrastructure for fuel cell vehicles are discussed. 2. Storage of natural gas and hydrogen Both natural gas and hydrogen are stored on-board the vehicle as a compressed gas. The volumes of the tanks are much greater than the volume of the gasoline tank in a conventional ICE vehicle. The technology for manufacturing storage tanks for compressed natural gas (CNG) is mature and commercial products are available (Worthington, 2015). Both steel and composite carbon fiber tanks are marketed. In the case of hydrogen, the technology for the tanks is still evolving (Dillich, 2009; Hua et al., 2010; Roth, Hu, & Ahluwalia 2013; Wood, 2014) and all the tanks are manufactured using carbon fiber composites. The characteristics of the energy storage tanks for natural gas and hydrogen are summarized in Table 1. The hydrogen is stored at 10,000 psi (680 atm.) and the natural gas at 3600 psi (245 atm.). The tank sizes given in Table 1 are for storing an amount of energy (MJ or kWh) equivalent to that in 5 gallons of gasoline or 5 kg of hydrogen. The tank sizes for storing larger amounts of energy can be calculated from the MJ/L and MJ/kg parameters. Note that the weight and volume of the tanks needed to store hydrogen are significantly greater than to store the same amount of energy with natural gas. This will be true even when the DOE goals for hydrogen storage are met. If both the natural gas and hydrogen tanks are constructed of carbon composite materials, the MJ/L factor for the natural gas tank is about 3x that of the DOE goal for hydrogen. For the same fuel energy storage (MJ), the volume of a natural gas tank is 4x greater and the hydrogen tank 8e9x greater than that of the gasoline tank. The composite hydrogen tanks are of carbon fiber construction and the present cost of the carbon fiber is quite high. However, considerable R&D (Hua et al., 2010; Roth et al., 2013; Wood, 2014) is being done to reduce the cost so it is expected that the cost of the hydrogen tanks will decrease significantly from their present cost of nearly $10/MJ. The natural gas tanks are metal with a carbon wrap and their present cost is about $3/MJ. The cost of all the tanks will also decrease in volume production for passenger cars. 3. Vehicle designs and simulations
Fig. 1. Powertrain schematics of the CNG and fuel cell vehicles. (a) Natural gas charge sustaining hybrid (HEV), (b) Hydrogen fuel cell vehicle.
As indicated in the Introduction, the gas fueled vehicles being compared are charge sustaining hybrid-electric CNG vehicles and fuel cell hydrogen vehicles. All the vehicles were simulated using the ADVISOR vehicle simulation program that has been extensively modified at UC Davis (Burke and Van Gelder, 2008; Burke, Zhao, & Van Gelder, 2009). ADVISOR models in detail the driveline components and the vehicle road load and calculates the sec-by-sec
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Table 1 Summary of gaseous fuel energy storage characteristics. Source or requirement
Fuel
Gasoline equivalent Gal.
Tank volumea L
Tank weighta kg
MJ/Ltank
MJ/kgtank
$/MJ
Present status DOE goal 2015 (new) Available composite Available metal with carbon wrap
H2b H2 CNGc CNG
5a 5 5 5
230 128 80 63
130 92 33 65
2.6 4.7 7.5 9.6
4.6 6.5 18.2 9.3
8.86 4.71
a b c
3.0
600 MJ fuel energy stored, 5 gal gasoline tank 20 L, 30 MJ/L. Hydrogen stored at 10,000 psi. CNG stored at 3600 psi.
operation of the vehicle for various driving cycles. The input parameters used in the simulations for the various classes of vehicles are given in Table 2. In the case of the hybrid-electric vehicles, a single-shaft arrangement with a double clutch transmission was used as the driveline. The control strategy utilized all-electric drive if the power demand could be met with the electric motor and operation of the engine at higher power demands by charging the battery as needed. In this way, the engine was operated near peak efficiency most of the time. The fuel cell vehicles were also hybrids with a large electric motor and a battery to meet the peak power demands. The fuel cell recharged the battery and provided steady power demand for cruising and hill climbing (Burke & Zhao, 2010; Zhao & Burke, 2009). The batteries used in both drivelines were high power lithium batteries that would give long life (at least 10 years) for shallow state-of-charge cycling. In this case, the battery state-of-charge varies by less than 10% (for example between 55 and 65%) as the car is driven. Ultracapacitors could be used in both the HEV and FC drivelines in place of the batteries (Burke & Miller, 2009; Burke, 2009). The engine map used in the CNG HEV simulations is given in Fig. 2. This is a spark-ignited engine operating near stoichiometric air-fuel ratio with a three-way catalyst. The simulation results for the CNG HEV and H2 FCV are summarized in Table 3. In all cases, the average fuel economy of the CNG HEV was about 60% higher than a comparable gasoline car. The fuel economies are given in terms of gasoline equivalent mpg which allowed the simple calculation of MJ for the required 400 mile range for all the vehicles except the delivery vehicle which has a 100 mile range. The fuel economy used for in the energy calculations was the average of the city and highway values. For the tank volumes shown in Table 3, it was assumed that the CNG vehicles used steel tanks with carbon fiber wrap and the H2 fuel cell vehicles used carbon composite tanks presently available (2.6 MJ/L). For all the vehicle classes, the volume of the hydrogen tanks was about 2x that of the CNG tank. Even if/when the DOE hydrogen energy storage goal (4.7 MJ/L) is met, the volume of the CNG tanks would be slightly smaller (about 15%) than the hydrogen tanks for the 400 mile vehicle range. Note in Table 3 that the equivalent fuel economy of the corresponding fuel cell vehicle is about 1.5x that of the CNG vehicle. In the cost analysis in the next section, it will be assumed that the chassis and body for the CNG and H2 vehicles in each class are essentially identical. The vehicles, of course, will differ in terms of driveline and fuel storage tanks, but it is assumed that these components can be installed with minimal change in the chassis.
Fig. 2. Engine map used in the CNG HEV simulations.
4. Cost of CNG hybrid and fuel cell vehicles (2015e2030) In this section, the present and future costs of the CNG and H2 vehicles will be calculated/projected. As noted previously, it is assumed that all the vehicles are ground-up designs such that the installation of the driveline and the fuel storage tanks do not detract from their utility and styling compared to corresponding gasoline fueled vehicles. In the past, the CNG tanks have been retrofitted into the trunk of the vehicle significantly reducing the trunk space. Fig. 3 shows the advantages of a ground-up design in storing gaseous fuels onboard vehicles. The acceleration performance of the CNG and H2 vehicles will be at least as good as the corresponding gasoline vehicles. Further it is expected that the drivability of the alternative fueled vehicles will be more desirable than the gasoline vehicles due to their electric drivelines. A relatively simple approach was followed to estimate the vehicle costs. A baseline price of the vehicle without the driveline and storage tank was estimated by taking the present price (2015) of the corresponding gasoline vehicle and subtracting the estimated cost of the engine/transmission unit ($40/kW). Next the total cost of the driveline components and storage tanks for each vehicle was calculated and their showroom price determined assuming a mark-
Table 2 Input parameters for the ADVISOR vehicle simulations. Vehicle type
CDA m2
fr
Weight kg
Engine kW
Electric motor kW
Battery kWh
Fuel cell kW
Electric motor kW
Battery kWh
Compact Mid-size Full-size Small SUV Mid-size SUV Delivery truck
.6 .68 .71 .72 .75 4.7
.008 .008 .008 .008 .008 .008
1388 1617 1890 1700 2100 7430
97 125 160 140 150 200
15 25 50 25 40 75
1.0 1.5 2.0 1.5 2.0 3.0
60 75 100 85 100 125
95 110 140 120 125 200
1.0 1.5 2.5 1.5 2.0 4.0
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A. Burke, L. Zhu / Research in Transportation Economics 52 (2015) 65e71
Table 3 Comparisons of the storage requirements (Liters) for CNG in an HEV and H2 in a fuel cell vehicle. H2 FCV
CNG HEV Vehicle type
EPA mpg, ICE vehicle
City mpg, Gasoline equiv.c
HW mpg, Gasoline equiv.
CNG storage for 400 miles La
City mpg, Gasoline equiv.
HW mpg, Gasoline equiv.
H2 storage for 400 Ratio of mpg FC miles Lb to HEV
Compact car Mid-size car Full-size car Small SUV Mid-size SUV UPS delivery truck
28/39 27/36 25/36 22/30 17/24
52.8 49.4 44.3 47.3 40 12.0
59.3 53.1 51.3 51.9 46 11.3
106 116 124 120 158 128 L for 100 mile range
75 71 67 69 62 19
88 79 75 80 70 16.4
224 244 258 246 277 258
a b c
1.46 1.47 1.48 1.50 1.50 1.52
CNG at 3600 psi, 8 MJ/L (steel tank). H2 at 10,000 psi, present technology 2.6 MJ/L. Gasoline energy content 119 MJ/gal.
Table 4 Assumed component costs in the cost analysis.
Fig. 3. Gaseous fuel storage in retrofitted and ground-up designed passenger cars. (a) Honda GX CNG Civic, (b) Gaseous fuel storage in a ground-up fuel cell vehicle.
up of 1.5. The OEM costs assumed for the various components are given in Table 4 for the period between 2015 and 2030. Cost information for alternative fueled vehicles is also given in (NRC, 2013; Ogden, Yang, Nicholas, &,Fulton, 2014). There is considerable
Component
2015
2020
2025
2030
Fuel cell system $/kW Electric motor/elect. $/kW Lithium battery $/kWh H2 storage $/kWh CNG storage $/kWh Engine/trans. $/kW
70 45 600 20 9 42
60 35 450 15 7 42
50 30 400 12 6 42
45 27 375 10 5 42
uncertainty regarding these costs because the sales volumes of the vehicles and thus the production volumes of the components needed to assemble them are difficult to assess especially as they will vary significantly over time. The component costs given in Table 4 assume relatively high sales volumes especially in the years beyond 2020, but lower sales volumes in prior years. During the early years of sales of both the CNG and H2 fueled vehicles, the vehicle sale prices are likely to be determined as much by future sales expectations as actual component costs. This will be particularly true of the fuel cell vehicles. The results of the price calculations for the CNG HEV and H2 FCV are given in Table 5. The projected prices of fuel cell powered midsize cars determined in this study are compared with those in a recent study (Ogden et al., 2014) by Ogden in Table 6. The prices from the two studies are in good agreement. The results in Table 5 indicate that the showroom prices of the CNG hybrid vehicles will be significantly lower than those of the fuel cell vehicles early in the period being considered, but the cost differences will narrow by the later years. It seems likely that the cost differences will be even greater in the early years than shown in Table 5 when the production and sales volumes of fuel cell vehicles are being ramped up. The cost differences indicate that CNG HEVs can offer an opportunity to familiarize the public with the fueling and operation of gaseous fuel vehicles during the period when fuel cell technology is maturing. As noted previously, the differences in the prices of the CNG and H2 fueled vehicles are likely to be determined more by the sales strategies for the fuel cell vehicles than by the actual component costs. The ownership costs of the vehicles also have been calculated from the initial purchase price and fuel economy results given in Tables 3 and 5. It is assumed that the vehicles are purchased using a 5 year loan at a 3.5% interest, the fuel prices change as shown in Table 7, and the vehicles travel 14,000 miles/year. The cost of natural gas is assumed to increase slowly and cost of the hydrogen is assumed to decrease markedly in the future. Both assumptions are favorable for the introduction of the gaseous fueled vehicles in the United States. It is likely the costs of the two fuels will be linked for much of the future period under consideration.
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Table 5 Results of the price calculations for the CNG HEV and H2 FCV. Vehicle type
Baseline vehicle price $
Vehicle price W/o driveline $
Compact CNG HEV H2 FCV Mid-size CNG HEV H2 FCV Full-size CNG HEV H2 FCV Small SUV CNG HEV H2 FCV Mid-size SUV CNG HEV H2 FCV
19,000
14,800
25,000
2015
2020
2025
2030
26,514 33,275
25,231 29,510
24,646 27,540
24,161 25,690
33,805 40,900
32,215 36,490
31,495 34,190
30,925 31,985
42,603 48,775
40,548 43,790
39,595 41,200
38,868 39,550
35,605 43,165
33,813 38,305
33,010 35,817
32,377 33,393
42,570 52,418
40,508 46,860
39,570 44,043
38,847 41,265
19,000
31,000
23,500
25,000
19,000
33,000
24,750
Table 6 Projected prices (2014$) of fuel car powered mid-size cars. Year
Present study
Ogden, etc. (Burke & Zhao, 2010)
2010 2015 2020 2025 2030
41 37 34 32
49 43 39 35 31
K K K K
K K K K K
Table 7 Projected fuel costs (2015e2030).
ownership cost of the fuel cell vehicles are less than the natural gas hybrids. Depending on the difference in the cost of natural gas and gasoline in $/GGE, the ownership cost of the natural gas hybrid could be less than that of the conventional gasoline model of each vehicle type. The results in Table 8 indicate that the vehicle price differences will be in ranges that modest purchase incentives and variations in registration fees and fuel taxes can have significant effects on the relative sales of the two types of vehicles. This seems to be the case for all the vehicle classes. It is certainly true that the costs are uncertain, but it does seem likely that the differences in the costs for the two types of gaseous fueled vehicles are relatively small over much of the time period being studied.
$/GGE Fuel
2015
2020
2025
2030
Natural gas Hydrogen
2.4 6
2.6 4
2.8 3
3.0 2.5
The differences in the total 5-year ownership costs for the natural gas hybrid and the hydrogen fuel cell vehicles are shown in Table 8. The cost differences are significant for vehicles purchased in the early years when the fuel cell vehicles are first introduced, but by 2030 the difference are small and in some cases the
5. Energy efficiency and CO2 emissions for alternative vehicles using natural gas as the source energy It is of interest to compare the efficiency (mi/kWh nat. gas) of using natural gas in various alternative vehicles-namely HEVs, EVs, and fuel cell vehicles. The calculation of the different natural gas efficiencies requires assumptions regarding the conversion of natural gas to electricity and hydrogen and the efficiencies (mpg gasoline equiv.) of the vehicles of interest. The following assumptions have been made in this example:
Table 8 Total difference in the ownership cost between the hydrogen fuel cell and natural gas hybrid vehicles over the first five years of ownership. $ over 5 years Vehicle type Compact CNG HEV H2 FCV Mid-size CNG HEV H2 FCV Full-size CNG HEV H2 FCV Small SUV CNG HEV H2 FCV Mid-size SUV CNG HEV H2 FCV
Fuel economy
Gal. Fuel equiv/Year (1)
56.1 81.5
250 172
51.3 75
2020
2025
9530
4855
2235
95
273 187
10,065
4850
1920
200
47.8 71
293 197
9120
3660
605
1185
49.6 74.5
282 188
10,495
4995
1930
770
43 66
326 212
10,375
6925
3400
395
Fuel cost $/GGE CNG H2 (1) Annual mileage 14,000 miles, 50% city, 50% highway.
2015
2.4 6
2.6 4
2.8 3
2030
3.0 2.5
70
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Natural gas to electricity 40% Natural gas to hydrogen 70% EV 250 Wh/mi of electricity from the wall plug CNG HEV 50 mpg gasoline equivalent H2 FCV 75 mpg gasoline equivalent The resulting natural gas efficiencies (mi/kWh nat. gas) are the following: EV 1.6 mi/kWh nat. gas HEV 1.52 FCV 1.59 These values do not include the energy required to distribution the electricity or natural gas and the energy required to compress the natural gas and hydrogen for use in the vehicles. According to references (Adams & Horne, 2010; Gardiner & Burke, 2002), the compression of natural gas and hydrogen use 2.3% and 7.2%, respectively, of the energy content of the gases. In most cases, the compressors used to compress the gases are driven by electric motors. It is assumed in this example that the efficiency of the compressor/motor system is 70%. This means, for example, that the energy required to generate the electricity from natural gas to compress the hydrogen is 7.2%/.7.4 or 25.7%. The corresponding energy for the compression of natural gas is 8.2%. If the loss in the distribution of the electricity is 10%, the compression energy values for natural gas and hydrogen become 9.1% and 28.5%, respectively. The charging efficiency of the EV battery is assumed to be .9. Hence the natural gas efficiencies (mi/kWh nat. gas) for the three alternative vehicles become EV 1.44 mi/kWh nat. gas HEV 1.38 FCV 1.14 These values indicate that including the gas compression energy and the electrical distribution losses in the calculation has a significant effect on the efficiency of utilizing natural gas to power vehicles. The results also indicate that the efficiencies for utilizing natural gas for hybrid and battery powered electric vehicles are essentially the same and that the efficiency for using hydrogen reformed from natural gas is about 20% lower. Next consider the CO2 emissions from the FCV, HEV, and EV vehicles assuming all the hydrogen and electricity are generated from natural gas. The CO2 emissions can be calculated from the energy efficiency (mi/kWh nat. gas) values for each of the vehicles by using the factors 1 kWh nat. gas ¼ .0766 kg nat. gas 1 mol CH4 / 1 mol CO2 or 1 kg nat. gas / 2.75 kgCO2 Hence EV .146 kgCO2/mi HEV .153 kgCO2/mi FCV .185 kgCO2/mi The CO2 emissions of the EV and HEV are nearly the same and the FCV has about 25% higher emissions than the other electrified vehicles when the hydrogen is obtained from reforming natural gas. In the near-term, it is likely this will be the case, but for longer term more of the hydrogen will be obtained from renewable sources and the resultant CO2 emissions for the FCV would be much lower.
6. Natural gas-hydrogen bridge considerations The success and timing of marketing hydrogen fuel cell vehicles will depend both on the technology developed and the availability of a hydrogen fueling infrastructure. As indicated in Joseck (2014), NRC. (2013), Ogden et al. (2014), good progress has been made in the technology area and in reducing the cost of fuel cell vehicles. Providing the hydrogen infrastructure on a national basis is proving to be more difficult (Fuel Cell Today, 2013). Whether natural gas fueled vehicles can be a bridge to the mass marketing of hydrogen fuel cell vehicles has been discussed in the literature (Cannon, 2012; Hefner, 2009; Nuboer, 2010; Wokaun & Wilhelm, 2011) since the 1990s and those discussions have been primarily concerned with how natural gas vehicles and their associated refueling infrastructure can be employed to make it less difficult to provide the hydrogen refueling infrastructure needed for fuel cell vehicles. This is thought to be the case because both vehicles use gaseous fuels with similar infrastructure and refueling practices. Hence it should be possible and economical to combine the fueling for natural gas and hydrogen in the same station especially during the early introductory period of the fuel cell vehicles in order to reduce the cost of providing their infrastructure. The cost of both types of stations is high, especially for fast fueling of the vehicles (Centerpointenergy, 2013; Fuel Cell Today, 2013; NGVAMERICA, 2014; NREL, 2005; Melina & Pennev, 2013). In the case of the natural gas refueling station, the cost is about $1 million (Centerpointenergy, 2013; NGVAMERICA, 2014) for a station that can refuel 15 light-duty/ 15GGE vehicles in a 1-hr. peak period. To add hydrogen refueling to the natural gas station would require the addition of a Steam Methane Reformer (SMR) unit to produce the hydrogen from natural gas and a compressor to increase the pressure to 10,000 psi. The cost of these components is likely to be $1e1.5 million (Melina & Pennev, 2013; NREL, 2005) to dispense 450 kgH2/da. The natural gas and electrical power for the reformer and compressor would be available as part of the initial natural gas station. The vehicle cost analysis indicates that the cost of the CNG HEV vehicles of the various classes will be lower than the corresponding FCVs. The cost differences will be significant (at least $5e10 K) before 2020 and narrow gradually in later years. Cost incentives could be offered by the Federal and State governments to reduce the cost differences in the early years. These incentives could be comparable to those currently be offered for plug-in electric vehicles. As indicated in (Alan, Azevedo, & Ferreira, 2013; Collantes & Eggert, 2014), these incentives have had a large effect on the sales of battery-electric and plug-in hybrid vehicles and can be expected to have a similar effect on the sales of CNG and H2 vehicles. The present (2014) cost of natural gas is relatively low making fuel expenditures for the CNG HEV vehicles less than for comparable gasoline fueled vehicles. Since natural gas is a “natural” fuel and hydrogen is a “processed” fuel, it seems reasonable to assume that CNG will always be lower cost ($/MJ) than H2. This and the fact that CNG is less difficult and expensive to store onboard vehicles should result in natural gas vehicles remaining marketable even after fuel cell vehicle technology is mature. The analysis of the CO2 emissions indicates that the emissions of the EVs and CNG HEVs are nearly the same and that the emissions of the FCVs using hydrogen from natural gas are about 20% higher. Hence during the early years after the introduction of FCVs, CNG HEVs would not result in higher GHG emissions (neglecting methane leakage which is uncertain at the present time) than FCVs. When hydrogen from renewable sources becomes available and the public is as familiar with gaseous fueled vehicle as they are now with liquid fueled vehicles, the stage will be set for the mass marketing of FCVs and the movement to sustainable personal transportation using hydrogen.
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References Adams, R., & Horne, D. B. (2010). Compressed natural Gas (CNG) transit bus experience survey-April 2009eApril 2010. National Renewable Energy Laboratory Report, September 2010, Subcontract report NREL/SR-7A2e48814. Alan, J., Azevedo, I. L., & Ferreira, P. (2013). The impact of federal incentives on the adoption of hybrid-electric vehicles in the United States. Energy Economics, 40, 936e942. Baker, D. (2015). Hydrogen-fueled cars face uncertain market in California, web article on June 1, 2014 indicating Hyundai and Toyota plan to market fuel cell cars by late 2015. Burke, A. F. (2009). Ultracpacitor technologies and applications in hybrid and electric vehicles. International Journal of Energy Research, 34(2), 133e151. Burke, A. F., & Miller, M. (2009). Electrochemical capacitors as energy storage in hybrid-electric vehicles: Present status and future prospects, EVS-24, Stavanger, Norway, May 2009 (paper on the CD of the meeting). Burke, A. F., & Van Gelder, E. (2008). Plug-in hybrid-electric vehicle powertrain design and control strategy options and simulation results with lithium-ion batteries. paper presented at EET-2008 European Elec-Drive Conference, Geneva, Switzerland, March 12, 2008 (paper on CD of proceedings). Burke, A. F., & Zhao, H. (2010). Projected fuel consumption characteristics of hybrid and fuel cell vehicles for 2015-2045. paper presented at the Electric Vehicle Symposium 25, Shenzhen, China, November 2010. Burke, A. F., Zhao, H., & Van Gelder, E. (2009). Simulated performance of alternative hybrid-electric powertrains in vehicles on various driving cycles, EVS-24, Stavanger, Norway, May 2009 (paper on the CD of the meeting). Cannon, J. S. (2012). Energy futures, Inc., natural gas: An essential bridge to hydrogen fuel cell vehicles. Centerpointenergy.com. (2013). Presentation on natural gas vehicles and refueling stations, February 2013. Collantes, G., & Eggert, A. (2014). The effect of monetary incentives in sales of advanced clean cars in the United States: Summary of the evidence. UC Davis Policy Institute for Energy, Environment, and Economy, September 1, 2014. Dillich, S. (2009). Hydrogen storage, 2009 DOE hydrogen program and vehicle technologies program. Presentation at the Merit Review, May 19, 2009. Fuel Cell Today. (2013). Hydrogen infrastructure developments in the USA. November 20, 2013, available on the Internet. Gardiner, M., & Burke, A. F. (2002). Comparisons of hydrogen storage technologies: a focus on energy required for hydrogen input. Fuel Chemistry Division Preprint 2002, 47(2), 794 (available on the internet). Hefner, R. A. (2009). The grand energy transition. Wiley. Hua, T., Ahluwalia, R., Peng, J-K., Kromer, M., Lasher, S., McKenney, K., et al. (2010). Technical assessment of compressed hydrogen storage tank systems for automotive applications. Argonne Laboratory Report, ANL-10/24, September 2010.
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Joseck, F. (2014). An overview of the U.S. department of energy hydrogen and fuel cell activities, presentation at the SAE new energy vehicle forum, Shanghai, China. September 24, 2014. Lee, A., Zinman, O., & Logan, J. (2012). NREL, opportunities for synergy between natural gas and renewable energy in the electric power and transportation sectors. LeFevre, C. (2014). The prospects for natural gas as a transport fuel in Europe, published by the Oxford Institute for Energy Studies. OIES Paper: NG 84, March 2014. Melina, M., & Pennev, M. (2013). Hydrogen station cost estimates. NREL Report NREL/ TP-5400e56412, September 2013. NGVAMERICA. (2014). CNG station construction and economics (available on the Internet from NGTNews). NRC. (2013). Transitions to alternative vehicles and fuels. National Research Council report, 2013. NREL. (2005). Strategy for the integration of hydrogen as a vehicle fuel into the existing natural gas vehicle fueling infrastructure of the interstate clean transportation corridor project. NREL Subcontract Report NREL/SR-540e38720, September 2005. Nuboer, M. (2010). The contribution of natural gas vehicles to sustainable transport, energy national energy agency. Ogden, J. M., Yang, C., Nicholas, M., & Fulton, L. (2014). Next steps white paperhydrogen transition. ITS-UC Davis Report UCD-ITS-RR-14e11. Parish, R. (2005). NREL, Strategy for the integration of hydrogen as a vehicle fuel into the existing natural gas vehicle fueling infrastructure of the interstate clean transportation corridor. Pfanner, E. (2015). Toyota shows off fuel-cell automobile, web article on November 20, 2013 indicating Toyota planned to begin selling a fuel cell sedan “around 2015”. Roth, H. S., Hu, T. Q., & Ahluwalia, R. K. (2013). Optimization of carbon fiber usage in type 4 hydrogen storage tanks for fuel cell automobiles. International Journal of Hydrogen Energy, 38, 12795e12802. U.S. EIA. (2013). Annual energy outlook 2013 with projections to 2040. U.S. Energy Information Administration, April 2013. Wokaun, A., & Wilhelm, E. (2011). Transition to hydrogen (pathways toward clean transportation). Cambridge University Press. Wood, D. L. (2014). Hydrogen and electrochemical energy storage at Oak Ridge national laboratory: Enabling widespread fuel cell and battery electric vehicle commercialization, presentation at the SAE new energy vehicle forum, Shanghai, China. September 24, 2014. Worthington Corp. (2015). Web site, specifications for CNG fuel tanks, Type I and Type III. Zhao, H., & Burke, A. F. (2009). Optimum performance of direct hydrogen hybrid fuel cell vehicles. EVS-24, Stavanger, Norway, May 2009 (paper on the CD of the meeting).
Contents lists available at ScienceDirect
Research in Transportation Economics journal homepage: www.elsevier.com/locate/retrec
The economics of the transition to fuel cell vehicles with natural gas, hybrid-electric vehicles as the bridge Andrew Burke*, Lin Zhu Institute of Transportation Studies, University of California, One Shields Ave., Davis, CA 95616, USA
a r t i c l e i n f o
a b s t r a c t
Article history: Available online 21 November 2015
Detailed comparisons are made between various types of light-duty vehicles fueled with natural gas and hydrogen. Natural gas vehicles are designed as charge sustaining hybrid vehicles (HEV) and hydrogen fueled vehicles (FCV) are powered by a fuel cell. All the vehicles have a range of 400 miles between refueling stops. This paper is concerned primarily with the near-term time period in which the fuel cell technology is maturing and the hydrogen infrastructure is being constructed both with respect to refueling stations and the source of the hydrogen being distributed. Detailed computer simulations are presented for vehicle classes from compact cars to mid-size SUVs. Energy (MJ) and volume (L) of fuel storage required to meet the 400 mile range target for each vehicle using natural gas and hydrogen are compared. Costs of the vehicles simulated are projected for 2015e2030. Cost results indicate that the costs of ownership of the natural gas HEVs and the hydrogen fuel cell vehicles become close in the 2025 e2030 time period. CO2 emissions from natural gas fueled hybrid and fuel cell vehicles are calculated and compared for hydrogen and electricity from natural gas. Ways in which the introduction of the natural gas fueled vehicles could be a bridge to the mass marketing of fuel cell vehicles are discussed. © 2015 Published by Elsevier Ltd.
JEL classification: Q2 Q3 Q4 Keywords: Natural gas Hydrogen Hybrids Fuel cells Costs Markets Transitions
1. Introduction There is considerable interest (Cannon, 2012; Hefner, 2009; Nuboer, 2010; Wokaun and Wilhelm, 2011) in increasing the use of natural gas as a fuel in the transportation sector primarily because it has a lower carbon intensity (gmCO2/MJ) than either gasoline or diesel fuel. Presently (2014) most of the activity in this area in the United States is concerned with the use of natural gas in heavy- and medium duty trucks and transit buses. However, there is much greater interest in using natural gas for light-duty passenger cars, SUVs, and pick-up trucks in Europe and Asia as a means of reducing tail-pipe emissions such as CO, HC, and particulates. This has resulted in the European car manufacturers providing a number of models that can operate on natural gas and gasoline depending on which fuel is available. Italy has provided financial incentives for car buyers to purchase natural gas fueled vehicles (LeFevre, 2014). As a result, Fiat markets a relatively large number of models that are natural gas fueled and Italy has over 75% of the natural gas cars in Europe. There are presently less than 600 natural
* Corresponding author. Tel.: þ1 530 752 9812. E-mail address: [email protected] (A. Burke). http://dx.doi.org/10.1016/j.retrec.2015.10.005 0739-8859/© 2015 Published by Elsevier Ltd.
gas refueling stations in the United States and over 4000 stations in Europe. There is, however, considerable discussion of the use of hydrogen fuel cells in light-duty vehicles in North America, Europe, and Asia. In fact, several auto manufacturers are planning (Baker, 2015; Pfanner, 2015) to begin marketing fuel cell vehicles in 2015. One of the impediments to marketing fuel cell vehicles is the lack of an extensive infrastructure for the hydrogen fuel. In addition, there is uncertainty regarding the acceptance of the public of the use of a gaseous fuel in their vehicles. In the past, there has been considerable discussion (Parish, 2005; Pfanner, 2015) of the use of natural gas in light-duty vehicles as a bridge to the use of hydrogen in vehicles. One of the reasons this discussion has not been taken seriously in the United States has been the lack of success in the marketing the few natural gas vehicle models that have been offered for sale. Annual sales of the Honda Natural Gas (GX) Civic were only 2198 vehicles in 2013 and only 781 in 2014. This leads Honda to discontinue sales of the GX Civic after 2015. These vehicles were retrofits of gasoline fueled Honda Civic models to accommodate natural gas as the fuel. Because the volume of the natural gas tank is much larger than the gasoline tank, part of the trunk of the retrofitted vehicle is taken up by the natural gas tank. Even then, the range of the natural gas vehicle is significantly less
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A. Burke, L. Zhu / Research in Transportation Economics 52 (2015) 65e71
than that of the gasoline fueled model. In addition, the price of the natural gas model was significantly higher ($5e6 K) than the standard gasoline model. Hence it was not surprising that sales of the natural gas model were very low. The questions addressed in this paper are whether light-duty vehicles designed from the ground-up to use gaseous fuels could be marketed successfully as natural gas vehicles and further how they would compare in the near-term with hydrogen fuel cell vehicles using the same chassis design to accept hydrogen storage tanks. In this way, natural gas vehicles could serve as a bridge to public acceptance and the mass marketing of fuel cell vehicles in the United States and Europe as their price becomes lower and the hydrogen infrastructure is developed. The wide availability of natural gas and its projected relatively low price (U.S. EIA, 2013) into the future compared to gasoline makes the strategy of marketing natural gas vehicles a reasonable possibility. As discussed in Cannon (2012), Hefner (2009), Parish (2005), Lee, Zinman, and Logan (2012), there are synergies between fueling stations for compressed natural gas and hydrogen, which should reduce the cost of providing the hydrogen infrastructure especially in the early stages of the introduction of fuel cell vehicles. For example, both stations would require the delivery via a pipeline of natural gas and a means of compressing and storing the gaseous fuel at high pressure. In this paper, detailed comparisons are made between various types of light-duty vehicles fueled with natural gas and hydrogen. The natural gas vehicles are designed as charge sustaining hybrid vehicles (HEV) and the hydrogen fueled vehicles (FCV) are powered by a fuel cell. All the vehicles have a range of 400 miles between refueling stops. Schematics of the powertrain of the CNG hybrid and hydrogen fuel cell vehicles are shown in Fig. 1. Both vehicles are electrified and use a small battery to increase the driveline efficiency. In the charge sustaining hybrid vehicle, the battery state-ofcharge is maintained in a near range do to charging from the
generator connected to the engine. Hence both vehicles are fueled by the gaseous fuels and not from the wall-plug. The paper discusses the on-board storage of natural gas (3600 psi) and hydrogen (10,000 psi) in terms of the volume, weight, and cost of the tanks required and how fuel storage affects the vehicle design. Detailed computer simulations of the vehicles are presented for several driving cycles and the energy (MJ) and volume (L) of fuel required to meet the 400 mile range target for each vehicle using natural gas and hydrogen are compared. The costs of the vehicles simulated are projected for 2015e2030. The differences between the costs of the natural gas hybrid vehicles and the fuel cell vehicles are calculated for the various vehicle types as the cost of the fuel cells, batteries and other powertrain components decrease in the future. The annual ownership costs of the vehicles are also calculated. The CO2 emissions from the CNG hybrid and hydrogen fuel cell vehicles are determined and compared. As a final step, the ways in which the introduction of the natural gas fueled vehicles could be a bridge to the mass marketing and infrastructure for fuel cell vehicles are discussed. 2. Storage of natural gas and hydrogen Both natural gas and hydrogen are stored on-board the vehicle as a compressed gas. The volumes of the tanks are much greater than the volume of the gasoline tank in a conventional ICE vehicle. The technology for manufacturing storage tanks for compressed natural gas (CNG) is mature and commercial products are available (Worthington, 2015). Both steel and composite carbon fiber tanks are marketed. In the case of hydrogen, the technology for the tanks is still evolving (Dillich, 2009; Hua et al., 2010; Roth, Hu, & Ahluwalia 2013; Wood, 2014) and all the tanks are manufactured using carbon fiber composites. The characteristics of the energy storage tanks for natural gas and hydrogen are summarized in Table 1. The hydrogen is stored at 10,000 psi (680 atm.) and the natural gas at 3600 psi (245 atm.). The tank sizes given in Table 1 are for storing an amount of energy (MJ or kWh) equivalent to that in 5 gallons of gasoline or 5 kg of hydrogen. The tank sizes for storing larger amounts of energy can be calculated from the MJ/L and MJ/kg parameters. Note that the weight and volume of the tanks needed to store hydrogen are significantly greater than to store the same amount of energy with natural gas. This will be true even when the DOE goals for hydrogen storage are met. If both the natural gas and hydrogen tanks are constructed of carbon composite materials, the MJ/L factor for the natural gas tank is about 3x that of the DOE goal for hydrogen. For the same fuel energy storage (MJ), the volume of a natural gas tank is 4x greater and the hydrogen tank 8e9x greater than that of the gasoline tank. The composite hydrogen tanks are of carbon fiber construction and the present cost of the carbon fiber is quite high. However, considerable R&D (Hua et al., 2010; Roth et al., 2013; Wood, 2014) is being done to reduce the cost so it is expected that the cost of the hydrogen tanks will decrease significantly from their present cost of nearly $10/MJ. The natural gas tanks are metal with a carbon wrap and their present cost is about $3/MJ. The cost of all the tanks will also decrease in volume production for passenger cars. 3. Vehicle designs and simulations
Fig. 1. Powertrain schematics of the CNG and fuel cell vehicles. (a) Natural gas charge sustaining hybrid (HEV), (b) Hydrogen fuel cell vehicle.
As indicated in the Introduction, the gas fueled vehicles being compared are charge sustaining hybrid-electric CNG vehicles and fuel cell hydrogen vehicles. All the vehicles were simulated using the ADVISOR vehicle simulation program that has been extensively modified at UC Davis (Burke and Van Gelder, 2008; Burke, Zhao, & Van Gelder, 2009). ADVISOR models in detail the driveline components and the vehicle road load and calculates the sec-by-sec
A. Burke, L. Zhu / Research in Transportation Economics 52 (2015) 65e71
67
Table 1 Summary of gaseous fuel energy storage characteristics. Source or requirement
Fuel
Gasoline equivalent Gal.
Tank volumea L
Tank weighta kg
MJ/Ltank
MJ/kgtank
$/MJ
Present status DOE goal 2015 (new) Available composite Available metal with carbon wrap
H2b H2 CNGc CNG
5a 5 5 5
230 128 80 63
130 92 33 65
2.6 4.7 7.5 9.6
4.6 6.5 18.2 9.3
8.86 4.71
a b c
3.0
600 MJ fuel energy stored, 5 gal gasoline tank 20 L, 30 MJ/L. Hydrogen stored at 10,000 psi. CNG stored at 3600 psi.
operation of the vehicle for various driving cycles. The input parameters used in the simulations for the various classes of vehicles are given in Table 2. In the case of the hybrid-electric vehicles, a single-shaft arrangement with a double clutch transmission was used as the driveline. The control strategy utilized all-electric drive if the power demand could be met with the electric motor and operation of the engine at higher power demands by charging the battery as needed. In this way, the engine was operated near peak efficiency most of the time. The fuel cell vehicles were also hybrids with a large electric motor and a battery to meet the peak power demands. The fuel cell recharged the battery and provided steady power demand for cruising and hill climbing (Burke & Zhao, 2010; Zhao & Burke, 2009). The batteries used in both drivelines were high power lithium batteries that would give long life (at least 10 years) for shallow state-of-charge cycling. In this case, the battery state-of-charge varies by less than 10% (for example between 55 and 65%) as the car is driven. Ultracapacitors could be used in both the HEV and FC drivelines in place of the batteries (Burke & Miller, 2009; Burke, 2009). The engine map used in the CNG HEV simulations is given in Fig. 2. This is a spark-ignited engine operating near stoichiometric air-fuel ratio with a three-way catalyst. The simulation results for the CNG HEV and H2 FCV are summarized in Table 3. In all cases, the average fuel economy of the CNG HEV was about 60% higher than a comparable gasoline car. The fuel economies are given in terms of gasoline equivalent mpg which allowed the simple calculation of MJ for the required 400 mile range for all the vehicles except the delivery vehicle which has a 100 mile range. The fuel economy used for in the energy calculations was the average of the city and highway values. For the tank volumes shown in Table 3, it was assumed that the CNG vehicles used steel tanks with carbon fiber wrap and the H2 fuel cell vehicles used carbon composite tanks presently available (2.6 MJ/L). For all the vehicle classes, the volume of the hydrogen tanks was about 2x that of the CNG tank. Even if/when the DOE hydrogen energy storage goal (4.7 MJ/L) is met, the volume of the CNG tanks would be slightly smaller (about 15%) than the hydrogen tanks for the 400 mile vehicle range. Note in Table 3 that the equivalent fuel economy of the corresponding fuel cell vehicle is about 1.5x that of the CNG vehicle. In the cost analysis in the next section, it will be assumed that the chassis and body for the CNG and H2 vehicles in each class are essentially identical. The vehicles, of course, will differ in terms of driveline and fuel storage tanks, but it is assumed that these components can be installed with minimal change in the chassis.
Fig. 2. Engine map used in the CNG HEV simulations.
4. Cost of CNG hybrid and fuel cell vehicles (2015e2030) In this section, the present and future costs of the CNG and H2 vehicles will be calculated/projected. As noted previously, it is assumed that all the vehicles are ground-up designs such that the installation of the driveline and the fuel storage tanks do not detract from their utility and styling compared to corresponding gasoline fueled vehicles. In the past, the CNG tanks have been retrofitted into the trunk of the vehicle significantly reducing the trunk space. Fig. 3 shows the advantages of a ground-up design in storing gaseous fuels onboard vehicles. The acceleration performance of the CNG and H2 vehicles will be at least as good as the corresponding gasoline vehicles. Further it is expected that the drivability of the alternative fueled vehicles will be more desirable than the gasoline vehicles due to their electric drivelines. A relatively simple approach was followed to estimate the vehicle costs. A baseline price of the vehicle without the driveline and storage tank was estimated by taking the present price (2015) of the corresponding gasoline vehicle and subtracting the estimated cost of the engine/transmission unit ($40/kW). Next the total cost of the driveline components and storage tanks for each vehicle was calculated and their showroom price determined assuming a mark-
Table 2 Input parameters for the ADVISOR vehicle simulations. Vehicle type
CDA m2
fr
Weight kg
Engine kW
Electric motor kW
Battery kWh
Fuel cell kW
Electric motor kW
Battery kWh
Compact Mid-size Full-size Small SUV Mid-size SUV Delivery truck
.6 .68 .71 .72 .75 4.7
.008 .008 .008 .008 .008 .008
1388 1617 1890 1700 2100 7430
97 125 160 140 150 200
15 25 50 25 40 75
1.0 1.5 2.0 1.5 2.0 3.0
60 75 100 85 100 125
95 110 140 120 125 200
1.0 1.5 2.5 1.5 2.0 4.0
68
A. Burke, L. Zhu / Research in Transportation Economics 52 (2015) 65e71
Table 3 Comparisons of the storage requirements (Liters) for CNG in an HEV and H2 in a fuel cell vehicle. H2 FCV
CNG HEV Vehicle type
EPA mpg, ICE vehicle
City mpg, Gasoline equiv.c
HW mpg, Gasoline equiv.
CNG storage for 400 miles La
City mpg, Gasoline equiv.
HW mpg, Gasoline equiv.
H2 storage for 400 Ratio of mpg FC miles Lb to HEV
Compact car Mid-size car Full-size car Small SUV Mid-size SUV UPS delivery truck
28/39 27/36 25/36 22/30 17/24
52.8 49.4 44.3 47.3 40 12.0
59.3 53.1 51.3 51.9 46 11.3
106 116 124 120 158 128 L for 100 mile range
75 71 67 69 62 19
88 79 75 80 70 16.4
224 244 258 246 277 258
a b c
1.46 1.47 1.48 1.50 1.50 1.52
CNG at 3600 psi, 8 MJ/L (steel tank). H2 at 10,000 psi, present technology 2.6 MJ/L. Gasoline energy content 119 MJ/gal.
Table 4 Assumed component costs in the cost analysis.
Fig. 3. Gaseous fuel storage in retrofitted and ground-up designed passenger cars. (a) Honda GX CNG Civic, (b) Gaseous fuel storage in a ground-up fuel cell vehicle.
up of 1.5. The OEM costs assumed for the various components are given in Table 4 for the period between 2015 and 2030. Cost information for alternative fueled vehicles is also given in (NRC, 2013; Ogden, Yang, Nicholas, &,Fulton, 2014). There is considerable
Component
2015
2020
2025
2030
Fuel cell system $/kW Electric motor/elect. $/kW Lithium battery $/kWh H2 storage $/kWh CNG storage $/kWh Engine/trans. $/kW
70 45 600 20 9 42
60 35 450 15 7 42
50 30 400 12 6 42
45 27 375 10 5 42
uncertainty regarding these costs because the sales volumes of the vehicles and thus the production volumes of the components needed to assemble them are difficult to assess especially as they will vary significantly over time. The component costs given in Table 4 assume relatively high sales volumes especially in the years beyond 2020, but lower sales volumes in prior years. During the early years of sales of both the CNG and H2 fueled vehicles, the vehicle sale prices are likely to be determined as much by future sales expectations as actual component costs. This will be particularly true of the fuel cell vehicles. The results of the price calculations for the CNG HEV and H2 FCV are given in Table 5. The projected prices of fuel cell powered midsize cars determined in this study are compared with those in a recent study (Ogden et al., 2014) by Ogden in Table 6. The prices from the two studies are in good agreement. The results in Table 5 indicate that the showroom prices of the CNG hybrid vehicles will be significantly lower than those of the fuel cell vehicles early in the period being considered, but the cost differences will narrow by the later years. It seems likely that the cost differences will be even greater in the early years than shown in Table 5 when the production and sales volumes of fuel cell vehicles are being ramped up. The cost differences indicate that CNG HEVs can offer an opportunity to familiarize the public with the fueling and operation of gaseous fuel vehicles during the period when fuel cell technology is maturing. As noted previously, the differences in the prices of the CNG and H2 fueled vehicles are likely to be determined more by the sales strategies for the fuel cell vehicles than by the actual component costs. The ownership costs of the vehicles also have been calculated from the initial purchase price and fuel economy results given in Tables 3 and 5. It is assumed that the vehicles are purchased using a 5 year loan at a 3.5% interest, the fuel prices change as shown in Table 7, and the vehicles travel 14,000 miles/year. The cost of natural gas is assumed to increase slowly and cost of the hydrogen is assumed to decrease markedly in the future. Both assumptions are favorable for the introduction of the gaseous fueled vehicles in the United States. It is likely the costs of the two fuels will be linked for much of the future period under consideration.
A. Burke, L. Zhu / Research in Transportation Economics 52 (2015) 65e71
69
Table 5 Results of the price calculations for the CNG HEV and H2 FCV. Vehicle type
Baseline vehicle price $
Vehicle price W/o driveline $
Compact CNG HEV H2 FCV Mid-size CNG HEV H2 FCV Full-size CNG HEV H2 FCV Small SUV CNG HEV H2 FCV Mid-size SUV CNG HEV H2 FCV
19,000
14,800
25,000
2015
2020
2025
2030
26,514 33,275
25,231 29,510
24,646 27,540
24,161 25,690
33,805 40,900
32,215 36,490
31,495 34,190
30,925 31,985
42,603 48,775
40,548 43,790
39,595 41,200
38,868 39,550
35,605 43,165
33,813 38,305
33,010 35,817
32,377 33,393
42,570 52,418
40,508 46,860
39,570 44,043
38,847 41,265
19,000
31,000
23,500
25,000
19,000
33,000
24,750
Table 6 Projected prices (2014$) of fuel car powered mid-size cars. Year
Present study
Ogden, etc. (Burke & Zhao, 2010)
2010 2015 2020 2025 2030
41 37 34 32
49 43 39 35 31
K K K K
K K K K K
Table 7 Projected fuel costs (2015e2030).
ownership cost of the fuel cell vehicles are less than the natural gas hybrids. Depending on the difference in the cost of natural gas and gasoline in $/GGE, the ownership cost of the natural gas hybrid could be less than that of the conventional gasoline model of each vehicle type. The results in Table 8 indicate that the vehicle price differences will be in ranges that modest purchase incentives and variations in registration fees and fuel taxes can have significant effects on the relative sales of the two types of vehicles. This seems to be the case for all the vehicle classes. It is certainly true that the costs are uncertain, but it does seem likely that the differences in the costs for the two types of gaseous fueled vehicles are relatively small over much of the time period being studied.
$/GGE Fuel
2015
2020
2025
2030
Natural gas Hydrogen
2.4 6
2.6 4
2.8 3
3.0 2.5
The differences in the total 5-year ownership costs for the natural gas hybrid and the hydrogen fuel cell vehicles are shown in Table 8. The cost differences are significant for vehicles purchased in the early years when the fuel cell vehicles are first introduced, but by 2030 the difference are small and in some cases the
5. Energy efficiency and CO2 emissions for alternative vehicles using natural gas as the source energy It is of interest to compare the efficiency (mi/kWh nat. gas) of using natural gas in various alternative vehicles-namely HEVs, EVs, and fuel cell vehicles. The calculation of the different natural gas efficiencies requires assumptions regarding the conversion of natural gas to electricity and hydrogen and the efficiencies (mpg gasoline equiv.) of the vehicles of interest. The following assumptions have been made in this example:
Table 8 Total difference in the ownership cost between the hydrogen fuel cell and natural gas hybrid vehicles over the first five years of ownership. $ over 5 years Vehicle type Compact CNG HEV H2 FCV Mid-size CNG HEV H2 FCV Full-size CNG HEV H2 FCV Small SUV CNG HEV H2 FCV Mid-size SUV CNG HEV H2 FCV
Fuel economy
Gal. Fuel equiv/Year (1)
56.1 81.5
250 172
51.3 75
2020
2025
9530
4855
2235
95
273 187
10,065
4850
1920
200
47.8 71
293 197
9120
3660
605
1185
49.6 74.5
282 188
10,495
4995
1930
770
43 66
326 212
10,375
6925
3400
395
Fuel cost $/GGE CNG H2 (1) Annual mileage 14,000 miles, 50% city, 50% highway.
2015
2.4 6
2.6 4
2.8 3
2030
3.0 2.5
70
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Natural gas to electricity 40% Natural gas to hydrogen 70% EV 250 Wh/mi of electricity from the wall plug CNG HEV 50 mpg gasoline equivalent H2 FCV 75 mpg gasoline equivalent The resulting natural gas efficiencies (mi/kWh nat. gas) are the following: EV 1.6 mi/kWh nat. gas HEV 1.52 FCV 1.59 These values do not include the energy required to distribution the electricity or natural gas and the energy required to compress the natural gas and hydrogen for use in the vehicles. According to references (Adams & Horne, 2010; Gardiner & Burke, 2002), the compression of natural gas and hydrogen use 2.3% and 7.2%, respectively, of the energy content of the gases. In most cases, the compressors used to compress the gases are driven by electric motors. It is assumed in this example that the efficiency of the compressor/motor system is 70%. This means, for example, that the energy required to generate the electricity from natural gas to compress the hydrogen is 7.2%/.7.4 or 25.7%. The corresponding energy for the compression of natural gas is 8.2%. If the loss in the distribution of the electricity is 10%, the compression energy values for natural gas and hydrogen become 9.1% and 28.5%, respectively. The charging efficiency of the EV battery is assumed to be .9. Hence the natural gas efficiencies (mi/kWh nat. gas) for the three alternative vehicles become EV 1.44 mi/kWh nat. gas HEV 1.38 FCV 1.14 These values indicate that including the gas compression energy and the electrical distribution losses in the calculation has a significant effect on the efficiency of utilizing natural gas to power vehicles. The results also indicate that the efficiencies for utilizing natural gas for hybrid and battery powered electric vehicles are essentially the same and that the efficiency for using hydrogen reformed from natural gas is about 20% lower. Next consider the CO2 emissions from the FCV, HEV, and EV vehicles assuming all the hydrogen and electricity are generated from natural gas. The CO2 emissions can be calculated from the energy efficiency (mi/kWh nat. gas) values for each of the vehicles by using the factors 1 kWh nat. gas ¼ .0766 kg nat. gas 1 mol CH4 / 1 mol CO2 or 1 kg nat. gas / 2.75 kgCO2 Hence EV .146 kgCO2/mi HEV .153 kgCO2/mi FCV .185 kgCO2/mi The CO2 emissions of the EV and HEV are nearly the same and the FCV has about 25% higher emissions than the other electrified vehicles when the hydrogen is obtained from reforming natural gas. In the near-term, it is likely this will be the case, but for longer term more of the hydrogen will be obtained from renewable sources and the resultant CO2 emissions for the FCV would be much lower.
6. Natural gas-hydrogen bridge considerations The success and timing of marketing hydrogen fuel cell vehicles will depend both on the technology developed and the availability of a hydrogen fueling infrastructure. As indicated in Joseck (2014), NRC. (2013), Ogden et al. (2014), good progress has been made in the technology area and in reducing the cost of fuel cell vehicles. Providing the hydrogen infrastructure on a national basis is proving to be more difficult (Fuel Cell Today, 2013). Whether natural gas fueled vehicles can be a bridge to the mass marketing of hydrogen fuel cell vehicles has been discussed in the literature (Cannon, 2012; Hefner, 2009; Nuboer, 2010; Wokaun & Wilhelm, 2011) since the 1990s and those discussions have been primarily concerned with how natural gas vehicles and their associated refueling infrastructure can be employed to make it less difficult to provide the hydrogen refueling infrastructure needed for fuel cell vehicles. This is thought to be the case because both vehicles use gaseous fuels with similar infrastructure and refueling practices. Hence it should be possible and economical to combine the fueling for natural gas and hydrogen in the same station especially during the early introductory period of the fuel cell vehicles in order to reduce the cost of providing their infrastructure. The cost of both types of stations is high, especially for fast fueling of the vehicles (Centerpointenergy, 2013; Fuel Cell Today, 2013; NGVAMERICA, 2014; NREL, 2005; Melina & Pennev, 2013). In the case of the natural gas refueling station, the cost is about $1 million (Centerpointenergy, 2013; NGVAMERICA, 2014) for a station that can refuel 15 light-duty/ 15GGE vehicles in a 1-hr. peak period. To add hydrogen refueling to the natural gas station would require the addition of a Steam Methane Reformer (SMR) unit to produce the hydrogen from natural gas and a compressor to increase the pressure to 10,000 psi. The cost of these components is likely to be $1e1.5 million (Melina & Pennev, 2013; NREL, 2005) to dispense 450 kgH2/da. The natural gas and electrical power for the reformer and compressor would be available as part of the initial natural gas station. The vehicle cost analysis indicates that the cost of the CNG HEV vehicles of the various classes will be lower than the corresponding FCVs. The cost differences will be significant (at least $5e10 K) before 2020 and narrow gradually in later years. Cost incentives could be offered by the Federal and State governments to reduce the cost differences in the early years. These incentives could be comparable to those currently be offered for plug-in electric vehicles. As indicated in (Alan, Azevedo, & Ferreira, 2013; Collantes & Eggert, 2014), these incentives have had a large effect on the sales of battery-electric and plug-in hybrid vehicles and can be expected to have a similar effect on the sales of CNG and H2 vehicles. The present (2014) cost of natural gas is relatively low making fuel expenditures for the CNG HEV vehicles less than for comparable gasoline fueled vehicles. Since natural gas is a “natural” fuel and hydrogen is a “processed” fuel, it seems reasonable to assume that CNG will always be lower cost ($/MJ) than H2. This and the fact that CNG is less difficult and expensive to store onboard vehicles should result in natural gas vehicles remaining marketable even after fuel cell vehicle technology is mature. The analysis of the CO2 emissions indicates that the emissions of the EVs and CNG HEVs are nearly the same and that the emissions of the FCVs using hydrogen from natural gas are about 20% higher. Hence during the early years after the introduction of FCVs, CNG HEVs would not result in higher GHG emissions (neglecting methane leakage which is uncertain at the present time) than FCVs. When hydrogen from renewable sources becomes available and the public is as familiar with gaseous fueled vehicle as they are now with liquid fueled vehicles, the stage will be set for the mass marketing of FCVs and the movement to sustainable personal transportation using hydrogen.
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