How Biofuels Can Contribute to Sustainable Mobility? - Assessment ...
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How Biofuels Can Contribute to Sustainable Mobility? - Assessment from Vehicle Technology Side Yuki Kudoh National Institute of Advanced Industrial Science and Technology 16-1 Onogawa, Tsukuba 305-8569 Japan [email protected] Keywords: Biofuels, Fuel Consumption, Well to Wheel, Sustainable Mobility
ABSTRACT Since biofuels can contribute to contribute to energy diversity from fuel to other energy resources and mitigate CO2 emissions and other air pollutants, they have been attracting attention from all around the world as alternative automotive fuel that can be used with internal combustion engine vehicles. This paper put main focus upon the fuel consumption of vehicle using biofuels by various driving condition. Well to Wheel CO2 emissions are estimated for various kinds of vehicle including biofuel vehicles in Japanese condition. How biofuels can contribute for sustainable mobility will be discussed from the viewpoint of LCA. INTRODUCTION Since the conventional automotive fuels strongly depend upon oil, GHGs and other air pollutants are emitted from the tailpipe to drive a vehicle by combusting fuel in the engine. In order to diversify automotive fuels from oil to other kinds of energy resources and reduce GHGs and air pollutants in automotive sector, the combination of automotive fuel and powertrain is required for the vehicle technology side. Under these situation, vehicle makers have been carrying out R&Ds for various kinds of alternative fuel vehicles (AFVs) and low emissions vehicles. However, there are lots of problems remain to be solved for the widespread of AFVs: the new infrastructures are usually required for filling unconventional automotive fuel for vehicles: electric vehicles are indeed environmentally friendly in terms of GHG emissions but the energy density of electricity that can be charged in the state-of-the-art battery is much smaller than internal combustion engine vehicles (ICEVs) and therefore the available cruising distance after charging the battery once is still very short for the pure battery electric vehicles. Attentions have been paid to utilization of biofuels as one of the automotive all over the world owing to the following reasons: biofuels are regarded as carbon neutral and CO2 released by biofuel combustion is balanced by the CO2 absorbed during its production: biofuels can be applied to existing ICEVs, either in neat form or blended with conventional fuel, with little or no modification to ICE: biofuels can be quite easily supplied to vehicles in current filling stations. Various studies have been carried out to evaluate the enviromental effect of utilization of automotive fuels from LCA perspective. In this paper, main focus will be put upon driving stage of biofuel vehicles. Fuel consumption of vehicle using biofuels will be assessed by various
conditions and CO2 emissions from AFVs in Japanese condition will be calculated by summing up the emissions from driving stage and automotive fuel production stage. And finally how biofuels can contribute for sustainable mobility will be discussed from the viewpoint of LCA. FUEL CONSUMPTION OF BIOFUEL VEHICLES Fuel consumption and accordingly GHG emissions of a vehicle varies by the assumed precondititons. In this section, focus will be put upon fuel of biofuel vehicles and conventional ICEV as reference in driving stage by various conditions. Some of the tailpipe air pollutants, e.g. CH4 or N2O, are accounted for GHG emissions but this paper only focuses upon the CO2 emissions by fuel combustion. In some of the references, only the fuel economies in MPG (mile per gallon) or km/l unit are given. In such cases, they are converted to fuel consumption in MJ-LHV/km unit by considering fuel properties. Simulation based assessment In the Well to Wheel (WtW) analysis carried out for EU and US conditions, which is a framework to evaluate environmental emissions and energy consumption over the entire energy chain cycle of automotive fuel, simulation models are used to evaluate the environmental performace of vehicles. The assumed preconditions are as follows: EU[1]: Simulation model ADVISOR is used, NEDC (New European Driving Cycle) driving schedule has been applied to, baseline vehicle is typical 2002 model year compact size 5 seater-sedan with 1.6 litres displacement port injected spark ignition (PISI) engine. US[2]: Simulation model PSAT developed by Algonne National Laboratory is used, FTP (Federal Test Procedure) driving schedule has been applied to, baseline vehicle is
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2005 model year gasoline vehicle with PISI engine. According to the results for Tank to Wheel (TtW) stage, in other words driving stage, it is assumed for biofuel vehicles that, whether they are used in neat form or in blends, the fuel consumption upon energy basis would remain the same as for the base fuel (gasoline or diesel). Catalogue based assessment The joint US EPA and DOE FuelEconomy.gov website[3] offers detailed information on vehicle fuel economy. You can find fuel economy of E85 flex fuel vehicles (FFVs) either using gasoline or E85 in the website. Usually, the fuel economy of a vehicle in mile per gallon (MPG) unit has been provided in city mode measured by FTP driving schedule, highway mode by HWFET (Highway Fuel Economy Test) driving schedule and combined mode, which has been calculated by weighted average of 55% of city mode and 45% of highway mode, in mile per gallon (MPG) unit. However, the provided fuel economy in the website is called “the EPA’s New MPG”, which has been estimated by reflecting the effects of faster speeds and acceleration, air conditioner use and colder outside temparature towards the fuel economy. The EPA’s New MPG of 332 FFVs, whose model years are from 2000 until 2008, has been collected from the website on 25th July, 2008. Fig.1 shows the distribution (boxplot) of rate , which can be calculated as = fuel consumption of E85 [MJ/km] / fuel consumption of gasoline [MJ/km]. The boxplot is consisted of the smallest non-outlier value (min), lower quartile (Q1), median (Q2), upper quartile (Q3) and largest non-outlier value (max) and the outlier is plotted circle. It can be confirmed from Fig.1 that median of is 96.2% and more than 3/4 of the fuel consumption of 332 FFVs using E85 would be less than those using gasoline. Measurement based assessment In this subsection, focuses are put upon the results acutually measured in Thailand and Brazilian condition. PTT Research and Technology Institute has carried out tests to evaluate the effects on emission and fuel consumption of vehicles using E10 gasohol in Thailand. According to their test[4], the average fuel consumption for vehicles using gasoline is 2.16 MJ/km; whereas that for E10 gasohol is 2.17 MJ/km, which are almost the same. In Brazil, E25 is usually used for automotive fuel but high density hydrous ethanol E93, which contains 7% of water in volume, is also available and FFVs that can use E93 are now in market. Giroldo et al.[5] have developed a 1.6 litres FFV “Fiesta Flex” whose vehicle attributes such as performace and fuel economy should be prioritized for E93 fuel usage, with no degradation in E25 fuel usage when compared to the
Fig.1 Boxplot of Table 1 Difference of fuel consumption of FFV using E25 and E93 in Brazil E93 fuel E25 fuel consumption consumption [MJ/km] [MJ/km] Fiesta 1.6l 2.16 (baseline) Fiesta Flex 2.13 2.22 Competitor 1 2.43 2.50 Competitor 2 2.41 2.47 Competitor 3 2.41 2.47 Competitor 4 2.19 2.45 baseline engine. They have compared the fuel economy measured in Brazilian norm NBR7024 driving schedule between the developed FFV and its competitors in the market. Table 1 shows the difference of fuel consumption. Owing to the water contents in E93 fuel, the fuel consumption of FFVs using hydrous E93 will be higher than FFVs using E25. WTW CO2 EMISSIONS IN JAPANESE CONDITION This section deals with the WtW CO2 emissions from various kinds of passenger vehicles in Japanese condition. The objective vehicles are gasoline vehicles with PISI engine (GV), hybrid vehicles with gasoline PISI engine (HV), diesel vehicles (DV) and battery electric vehicles (BEV) and objective fuels are conventional gasoline (CG), E3, E10, conventional diesel (CD), B5, neat BDF and electricity. In Japan, it is said that the vehicles using blend biofuels can achieve the same fuel consumption performace in actual use as the base fuel. Therefore it is assumed in this section that the vehicles using biofuels can achieve the same fuel consumption performace as the base fuels, in the same manner as references [1] and [2]. WtW CO2 emissions in driving test cycle Fig. 2 depicts the WtW CO2 emissions in Japanese norm 10•15 mode driving schedule. Both Well to Tank (WtT), or fuel supply stage, and TtW results are based upon reference
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[6]. In the WtT results for biofuels and electricity, the following fuel paths have been assumed: ethanol from sugar cane imported from Brazil and ethanol from waste wood in Japan: BDF from palm oil imported from Malaysia and BDF from waste oil in Japan: Japanese grid average electricy, electricity by photovoltaics (PV) and wind power. The TtW results are evaluated by the simulation model GREEN (General Research for Energy Efficiency of New Technology Vehicles) developed by Japan Automobile Research Institute. From Fig.2, it can be said that WtW CO2 emissions from GVs using bioethanol can be reduced compared with those using CG but it depends on the assumed fuel path of bioethanol. If it is produced from waste wood in Japan, WtW CO2 emissions may increase. In Japan, technologies and strategies are required for production and supply of bioethanol with low CO2 emissions in WtT stage and stable supply so that they can contribute to both CO2 reduction and energy diversity from oil in automotive sector. The emissions from DVs using either CD or B5 are indeed less than those from GVs. However, the number of DVs in Japan had rapidly decreased from 9% in 1990 to 4% in 2007 of the total number of registered passenger vehicles owing to the negative image for tailpipe emissions. In order to shift from GVs to DVs, our government has settled a plan to diffuse the clean DVs that can reduce both tailpipe and CO2 emissions. We already have various types of HVs in Japanese market. After the first commercial HV has put into market in 1997, the number of HV are steadily growing owing to their high fuel economy performance and the number of passenger HVs account for 337,740 at the end of March 2007. And Japanese vehicle makers are planning to put BEVs into market by 2010. From Fig.2, it can be said that these electric vehicles have advantages in term of WtW CO2 emissions in Japanese conditon compared with ICE vehicles, either using conventional fuel or biofuels. WtW CO2 emissions in actual use In this paper, most of the fuel consumption of vehicles in TtW stage is assumed to be simulated or measured in vehicle test cycles. However, it is quite a well-known fact that the fuel consumption of vehicles in actual use depends upon driver behaviour, traffc conditions, climate and carcare habits and there exists a gap between fuel consumption of vehicles measured by driving test cycle and in actual use. Author has been analysing the fuel consumption of gasoline-fuelled and electric vehicles in actual use[7][8]. In this subsection, focus will be put upon the WtW CO2 emissions in actual use. Fig.3 show the difference of WtW CO2 emissions in actual use by average travel velocity. The objective vehicles are GV, HV and BEV and objective fuels are CG, E3 and electricity by Japanese grid average. The WtT CO2
Fig.2 WtW CO2 emissions in Japanese condition
Fig. 3 WtW CO2 emissions in actual use emissions of objective fuels are cited from reference [6]. It is assumed for GV using E3 that the fuel consumption performace is exactly the same with that using CG upon energy basis. In urban areas where stop-and-goes occur frequently and average velocity is low, WtW CO2 emissions of electric vehicles (HV and BEV) prevail over GV owing to recovery of regenerated electricity, whereas in rural areas where traffic is smooth and average velocity is high, the gap between WtW CO2 emissions of GV and electric vehicles becomes smaller than in urban areas. SUMMARY AND DISCUSSIONS In this paper, main focus has been put upon driving stage of biofuel vehicles. Be reviewing various references, the fuel consumption of vehicles fuelled with blended biofuels can be expected to be exactly or almost the same as using base fuels upon energy basis but it would be smaller if it is fuelled with hydrous ethanol. Then the WtW CO2 emissions from various kinds of vehicles are estimated for Japanese condition, both in vehicle driving test cycle and in actual use. The results show that CO2 emissions from vehicles might be reduced by using blended biofuels if the biofuels can be produced and supplied by low WtT CO2 emissions but cannot reduce more than by using electric vehicles. WtW CO2 emissions have average velocity dependence and they would be different by the places we drive even if we are using the same vehicle or fuel. It is true that electric vehicles can reduce CO2 emissions
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but the problem is that if they are driven only with the charged battery, the cruising distance after charging the battery once will be shorter than ICEVs. Therefore infractructures to charge battery is required for electric vehicles except for hybrids. On the other hand, the CO2 reduction effect of biofuel vehicles may be smaller than electric vehicles but biofuels have the merits that they can be used in the conventional ICEVs without making major modifications and that they can be quite easily supplied to vehicles in current filling stations. Population density is high in Japanese urban areas and because of the frequent occurunce of traffic congestions, average travel velocity is low compared with rural areas. However, accessibility is high owing to the well provided public transport service and dense town structure and average trip length to access points is relatively short in urban areas. On the other hand, it is financially difficult to provide public transport in rural areas since the operation of public transport is based upon self-supporting principles in Japan and therefore automobiles are used as the main means of daily transport. Because the average trip length to access points is longer than in urban areas, infrastructures should be provided densely if AFVs with short crusing distance after charging fuels are used in rural areas. Considering these situations in Japan, the result of WtW CO2 emissions in actual use, as shown in Fig.3, implicates that the powertrain and automotive fuel selection for reducing CO2 emissions effectively should be different urban and rural areas: BEVs can be used in urban areas: conventional vehicles such as ICEVs with low fuel consumption and HVs are effective in rural areas. In the rural areas, biofuels can also be used to reduce CO2 emissions based upon local production for local consumption basis. Toyota say in their sustainability report[9] that they are planning to solve energy and environmental issues by developing and producing cars that can together reduce CO2 emissions and make the air cleaner based upon the concept of “the right vehicle at the right time in right place”. The concept can be also applied to achieving sustainable mobility, for the needs for traffic, traffic condition, urban structure, the current and future energy supply condition or the other aspects surrounding transport are different by countries and regions, or they would be different even within the same country or region. Successive studies for using AFVs including biofuels to achieve sustainable mobility are required regarding consumers’ way of vehicle use and their preference for AFVs, etc. REFERENCES [1] EUCAR/CONCAWE/JRC: “Tank-to-Wheels Report of Well-to-Wheels analysis of future automotive fuels and powertrains in the European context”, Version 2c, March 2007.
http://ies.jrc.ec.europa.eu/uploads/media/TTW_Report_010 307.pdf [2] Algonne National Laboratory: “The Greenhouse Gases, Regulated Emissions, and Energy Use in Transportation (GREET) Model”, Version 1.8b, September 2008. http://www.transportation.anl.gov/modeling_simulation/GR EET/index.html [3] US EPA and DOE: “FuelEconomy.gov”, http://www.fueleconomy.gov/ [4] PTT Public Company Limited: http://www.pttplc.com/en/ptt_core.asp?page=ps_pr_fu_gs_ 08 [5] Giroldo, M. B. et al: “Development of 1.6L Flex Fuel Engine for Brazilian Market”, SAE Paper, 2005-01-4130, 1-9, 2005. [6] JHFC Total Efficiency Study Group, Japan Automobile Research Institute: “JHFC Final Report on Well to Wheel Efficiency” (in Japanese), March 2006. [7] Yuki Kudoh, et al: “Environmental Impacts of Introducing FCEVs and BEVs within Road Traffic System of Tokyo”, The 21st Worldwide Battery, Hybrid and Fuel Cell Electric Vehicle Symposium & Exhibition, 2005. (Proceedings: CD-ROM.) [8] Yuki Kudoh, et al: “Analysis of Existing Variation in Fuel Consumption of Hybrid Electric Vehicles”, EVER Monaco 2007. (Proceedings: CD-ROM.) [9] Toyota Motor Corporation: “Sustainability Report 2008”. http://www.toyota.co.jp/en/csr/report/08/download/pdf/sust ainability_report08.pdf
How Biofuels Can Contribute to Sustainable Mobility? - Assessment from Vehicle Technology Side Yuki Kudoh National Institute of Advanced Industrial Science and Technology 16-1 Onogawa, Tsukuba 305-8569 Japan [email protected] Keywords: Biofuels, Fuel Consumption, Well to Wheel, Sustainable Mobility
ABSTRACT Since biofuels can contribute to contribute to energy diversity from fuel to other energy resources and mitigate CO2 emissions and other air pollutants, they have been attracting attention from all around the world as alternative automotive fuel that can be used with internal combustion engine vehicles. This paper put main focus upon the fuel consumption of vehicle using biofuels by various driving condition. Well to Wheel CO2 emissions are estimated for various kinds of vehicle including biofuel vehicles in Japanese condition. How biofuels can contribute for sustainable mobility will be discussed from the viewpoint of LCA. INTRODUCTION Since the conventional automotive fuels strongly depend upon oil, GHGs and other air pollutants are emitted from the tailpipe to drive a vehicle by combusting fuel in the engine. In order to diversify automotive fuels from oil to other kinds of energy resources and reduce GHGs and air pollutants in automotive sector, the combination of automotive fuel and powertrain is required for the vehicle technology side. Under these situation, vehicle makers have been carrying out R&Ds for various kinds of alternative fuel vehicles (AFVs) and low emissions vehicles. However, there are lots of problems remain to be solved for the widespread of AFVs: the new infrastructures are usually required for filling unconventional automotive fuel for vehicles: electric vehicles are indeed environmentally friendly in terms of GHG emissions but the energy density of electricity that can be charged in the state-of-the-art battery is much smaller than internal combustion engine vehicles (ICEVs) and therefore the available cruising distance after charging the battery once is still very short for the pure battery electric vehicles. Attentions have been paid to utilization of biofuels as one of the automotive all over the world owing to the following reasons: biofuels are regarded as carbon neutral and CO2 released by biofuel combustion is balanced by the CO2 absorbed during its production: biofuels can be applied to existing ICEVs, either in neat form or blended with conventional fuel, with little or no modification to ICE: biofuels can be quite easily supplied to vehicles in current filling stations. Various studies have been carried out to evaluate the enviromental effect of utilization of automotive fuels from LCA perspective. In this paper, main focus will be put upon driving stage of biofuel vehicles. Fuel consumption of vehicle using biofuels will be assessed by various
conditions and CO2 emissions from AFVs in Japanese condition will be calculated by summing up the emissions from driving stage and automotive fuel production stage. And finally how biofuels can contribute for sustainable mobility will be discussed from the viewpoint of LCA. FUEL CONSUMPTION OF BIOFUEL VEHICLES Fuel consumption and accordingly GHG emissions of a vehicle varies by the assumed precondititons. In this section, focus will be put upon fuel of biofuel vehicles and conventional ICEV as reference in driving stage by various conditions. Some of the tailpipe air pollutants, e.g. CH4 or N2O, are accounted for GHG emissions but this paper only focuses upon the CO2 emissions by fuel combustion. In some of the references, only the fuel economies in MPG (mile per gallon) or km/l unit are given. In such cases, they are converted to fuel consumption in MJ-LHV/km unit by considering fuel properties. Simulation based assessment In the Well to Wheel (WtW) analysis carried out for EU and US conditions, which is a framework to evaluate environmental emissions and energy consumption over the entire energy chain cycle of automotive fuel, simulation models are used to evaluate the environmental performace of vehicles. The assumed preconditions are as follows: EU[1]: Simulation model ADVISOR is used, NEDC (New European Driving Cycle) driving schedule has been applied to, baseline vehicle is typical 2002 model year compact size 5 seater-sedan with 1.6 litres displacement port injected spark ignition (PISI) engine. US[2]: Simulation model PSAT developed by Algonne National Laboratory is used, FTP (Federal Test Procedure) driving schedule has been applied to, baseline vehicle is
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2005 model year gasoline vehicle with PISI engine. According to the results for Tank to Wheel (TtW) stage, in other words driving stage, it is assumed for biofuel vehicles that, whether they are used in neat form or in blends, the fuel consumption upon energy basis would remain the same as for the base fuel (gasoline or diesel). Catalogue based assessment The joint US EPA and DOE FuelEconomy.gov website[3] offers detailed information on vehicle fuel economy. You can find fuel economy of E85 flex fuel vehicles (FFVs) either using gasoline or E85 in the website. Usually, the fuel economy of a vehicle in mile per gallon (MPG) unit has been provided in city mode measured by FTP driving schedule, highway mode by HWFET (Highway Fuel Economy Test) driving schedule and combined mode, which has been calculated by weighted average of 55% of city mode and 45% of highway mode, in mile per gallon (MPG) unit. However, the provided fuel economy in the website is called “the EPA’s New MPG”, which has been estimated by reflecting the effects of faster speeds and acceleration, air conditioner use and colder outside temparature towards the fuel economy. The EPA’s New MPG of 332 FFVs, whose model years are from 2000 until 2008, has been collected from the website on 25th July, 2008. Fig.1 shows the distribution (boxplot) of rate , which can be calculated as = fuel consumption of E85 [MJ/km] / fuel consumption of gasoline [MJ/km]. The boxplot is consisted of the smallest non-outlier value (min), lower quartile (Q1), median (Q2), upper quartile (Q3) and largest non-outlier value (max) and the outlier is plotted circle. It can be confirmed from Fig.1 that median of is 96.2% and more than 3/4 of the fuel consumption of 332 FFVs using E85 would be less than those using gasoline. Measurement based assessment In this subsection, focuses are put upon the results acutually measured in Thailand and Brazilian condition. PTT Research and Technology Institute has carried out tests to evaluate the effects on emission and fuel consumption of vehicles using E10 gasohol in Thailand. According to their test[4], the average fuel consumption for vehicles using gasoline is 2.16 MJ/km; whereas that for E10 gasohol is 2.17 MJ/km, which are almost the same. In Brazil, E25 is usually used for automotive fuel but high density hydrous ethanol E93, which contains 7% of water in volume, is also available and FFVs that can use E93 are now in market. Giroldo et al.[5] have developed a 1.6 litres FFV “Fiesta Flex” whose vehicle attributes such as performace and fuel economy should be prioritized for E93 fuel usage, with no degradation in E25 fuel usage when compared to the
Fig.1 Boxplot of Table 1 Difference of fuel consumption of FFV using E25 and E93 in Brazil E93 fuel E25 fuel consumption consumption [MJ/km] [MJ/km] Fiesta 1.6l 2.16 (baseline) Fiesta Flex 2.13 2.22 Competitor 1 2.43 2.50 Competitor 2 2.41 2.47 Competitor 3 2.41 2.47 Competitor 4 2.19 2.45 baseline engine. They have compared the fuel economy measured in Brazilian norm NBR7024 driving schedule between the developed FFV and its competitors in the market. Table 1 shows the difference of fuel consumption. Owing to the water contents in E93 fuel, the fuel consumption of FFVs using hydrous E93 will be higher than FFVs using E25. WTW CO2 EMISSIONS IN JAPANESE CONDITION This section deals with the WtW CO2 emissions from various kinds of passenger vehicles in Japanese condition. The objective vehicles are gasoline vehicles with PISI engine (GV), hybrid vehicles with gasoline PISI engine (HV), diesel vehicles (DV) and battery electric vehicles (BEV) and objective fuels are conventional gasoline (CG), E3, E10, conventional diesel (CD), B5, neat BDF and electricity. In Japan, it is said that the vehicles using blend biofuels can achieve the same fuel consumption performace in actual use as the base fuel. Therefore it is assumed in this section that the vehicles using biofuels can achieve the same fuel consumption performace as the base fuels, in the same manner as references [1] and [2]. WtW CO2 emissions in driving test cycle Fig. 2 depicts the WtW CO2 emissions in Japanese norm 10•15 mode driving schedule. Both Well to Tank (WtT), or fuel supply stage, and TtW results are based upon reference
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[6]. In the WtT results for biofuels and electricity, the following fuel paths have been assumed: ethanol from sugar cane imported from Brazil and ethanol from waste wood in Japan: BDF from palm oil imported from Malaysia and BDF from waste oil in Japan: Japanese grid average electricy, electricity by photovoltaics (PV) and wind power. The TtW results are evaluated by the simulation model GREEN (General Research for Energy Efficiency of New Technology Vehicles) developed by Japan Automobile Research Institute. From Fig.2, it can be said that WtW CO2 emissions from GVs using bioethanol can be reduced compared with those using CG but it depends on the assumed fuel path of bioethanol. If it is produced from waste wood in Japan, WtW CO2 emissions may increase. In Japan, technologies and strategies are required for production and supply of bioethanol with low CO2 emissions in WtT stage and stable supply so that they can contribute to both CO2 reduction and energy diversity from oil in automotive sector. The emissions from DVs using either CD or B5 are indeed less than those from GVs. However, the number of DVs in Japan had rapidly decreased from 9% in 1990 to 4% in 2007 of the total number of registered passenger vehicles owing to the negative image for tailpipe emissions. In order to shift from GVs to DVs, our government has settled a plan to diffuse the clean DVs that can reduce both tailpipe and CO2 emissions. We already have various types of HVs in Japanese market. After the first commercial HV has put into market in 1997, the number of HV are steadily growing owing to their high fuel economy performance and the number of passenger HVs account for 337,740 at the end of March 2007. And Japanese vehicle makers are planning to put BEVs into market by 2010. From Fig.2, it can be said that these electric vehicles have advantages in term of WtW CO2 emissions in Japanese conditon compared with ICE vehicles, either using conventional fuel or biofuels. WtW CO2 emissions in actual use In this paper, most of the fuel consumption of vehicles in TtW stage is assumed to be simulated or measured in vehicle test cycles. However, it is quite a well-known fact that the fuel consumption of vehicles in actual use depends upon driver behaviour, traffc conditions, climate and carcare habits and there exists a gap between fuel consumption of vehicles measured by driving test cycle and in actual use. Author has been analysing the fuel consumption of gasoline-fuelled and electric vehicles in actual use[7][8]. In this subsection, focus will be put upon the WtW CO2 emissions in actual use. Fig.3 show the difference of WtW CO2 emissions in actual use by average travel velocity. The objective vehicles are GV, HV and BEV and objective fuels are CG, E3 and electricity by Japanese grid average. The WtT CO2
Fig.2 WtW CO2 emissions in Japanese condition
Fig. 3 WtW CO2 emissions in actual use emissions of objective fuels are cited from reference [6]. It is assumed for GV using E3 that the fuel consumption performace is exactly the same with that using CG upon energy basis. In urban areas where stop-and-goes occur frequently and average velocity is low, WtW CO2 emissions of electric vehicles (HV and BEV) prevail over GV owing to recovery of regenerated electricity, whereas in rural areas where traffic is smooth and average velocity is high, the gap between WtW CO2 emissions of GV and electric vehicles becomes smaller than in urban areas. SUMMARY AND DISCUSSIONS In this paper, main focus has been put upon driving stage of biofuel vehicles. Be reviewing various references, the fuel consumption of vehicles fuelled with blended biofuels can be expected to be exactly or almost the same as using base fuels upon energy basis but it would be smaller if it is fuelled with hydrous ethanol. Then the WtW CO2 emissions from various kinds of vehicles are estimated for Japanese condition, both in vehicle driving test cycle and in actual use. The results show that CO2 emissions from vehicles might be reduced by using blended biofuels if the biofuels can be produced and supplied by low WtT CO2 emissions but cannot reduce more than by using electric vehicles. WtW CO2 emissions have average velocity dependence and they would be different by the places we drive even if we are using the same vehicle or fuel. It is true that electric vehicles can reduce CO2 emissions
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but the problem is that if they are driven only with the charged battery, the cruising distance after charging the battery once will be shorter than ICEVs. Therefore infractructures to charge battery is required for electric vehicles except for hybrids. On the other hand, the CO2 reduction effect of biofuel vehicles may be smaller than electric vehicles but biofuels have the merits that they can be used in the conventional ICEVs without making major modifications and that they can be quite easily supplied to vehicles in current filling stations. Population density is high in Japanese urban areas and because of the frequent occurunce of traffic congestions, average travel velocity is low compared with rural areas. However, accessibility is high owing to the well provided public transport service and dense town structure and average trip length to access points is relatively short in urban areas. On the other hand, it is financially difficult to provide public transport in rural areas since the operation of public transport is based upon self-supporting principles in Japan and therefore automobiles are used as the main means of daily transport. Because the average trip length to access points is longer than in urban areas, infrastructures should be provided densely if AFVs with short crusing distance after charging fuels are used in rural areas. Considering these situations in Japan, the result of WtW CO2 emissions in actual use, as shown in Fig.3, implicates that the powertrain and automotive fuel selection for reducing CO2 emissions effectively should be different urban and rural areas: BEVs can be used in urban areas: conventional vehicles such as ICEVs with low fuel consumption and HVs are effective in rural areas. In the rural areas, biofuels can also be used to reduce CO2 emissions based upon local production for local consumption basis. Toyota say in their sustainability report[9] that they are planning to solve energy and environmental issues by developing and producing cars that can together reduce CO2 emissions and make the air cleaner based upon the concept of “the right vehicle at the right time in right place”. The concept can be also applied to achieving sustainable mobility, for the needs for traffic, traffic condition, urban structure, the current and future energy supply condition or the other aspects surrounding transport are different by countries and regions, or they would be different even within the same country or region. Successive studies for using AFVs including biofuels to achieve sustainable mobility are required regarding consumers’ way of vehicle use and their preference for AFVs, etc. REFERENCES [1] EUCAR/CONCAWE/JRC: “Tank-to-Wheels Report of Well-to-Wheels analysis of future automotive fuels and powertrains in the European context”, Version 2c, March 2007.
http://ies.jrc.ec.europa.eu/uploads/media/TTW_Report_010 307.pdf [2] Algonne National Laboratory: “The Greenhouse Gases, Regulated Emissions, and Energy Use in Transportation (GREET) Model”, Version 1.8b, September 2008. http://www.transportation.anl.gov/modeling_simulation/GR EET/index.html [3] US EPA and DOE: “FuelEconomy.gov”, http://www.fueleconomy.gov/ [4] PTT Public Company Limited: http://www.pttplc.com/en/ptt_core.asp?page=ps_pr_fu_gs_ 08 [5] Giroldo, M. B. et al: “Development of 1.6L Flex Fuel Engine for Brazilian Market”, SAE Paper, 2005-01-4130, 1-9, 2005. [6] JHFC Total Efficiency Study Group, Japan Automobile Research Institute: “JHFC Final Report on Well to Wheel Efficiency” (in Japanese), March 2006. [7] Yuki Kudoh, et al: “Environmental Impacts of Introducing FCEVs and BEVs within Road Traffic System of Tokyo”, The 21st Worldwide Battery, Hybrid and Fuel Cell Electric Vehicle Symposium & Exhibition, 2005. (Proceedings: CD-ROM.) [8] Yuki Kudoh, et al: “Analysis of Existing Variation in Fuel Consumption of Hybrid Electric Vehicles”, EVER Monaco 2007. (Proceedings: CD-ROM.) [9] Toyota Motor Corporation: “Sustainability Report 2008”. http://www.toyota.co.jp/en/csr/report/08/download/pdf/sust ainability_report08.pdf
