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Jul 15, 2005 - Norway belongs to the above countries, and although a significant increase in the sales of Diesel passenger cars has been observed duri...
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Energy & Fuels 2005, 19, 1919-1926

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CO2 Changes from the Increasing Percentage of Diesel Passenger Cars in Norway Efthimios Zervas*,†,§ and Georgios Bikas‡,| Ecole des Mines de Nantes - De´ partement des Syste` mes Energe´ tiques et Environnement, 4, rue Alfred Kastler, F-44307 Nantes Cedex 3, France, and Institut fuer Technische Mechanik, RWTH Aachen, Templergraben 64, 52056 Aachen, Germany Received March 22, 2005. Revised Manuscript Received June 8, 2005

Emissions of CO2 and other greenhouse gases are responsible for climate changes. The replacement of gasoline passenger cars by Diesel ones, which emit less CO2, can be an efficient way to decrease CO2 emissions. This replacement can be more effective in countries with low Diesel penetration. Norway belongs to the above countries, and although a significant increase in the sales of Diesel passenger cars has been observed during the last years, the overall Diesel penetration remains lower than 23%. Several scenarios, using the current and estimated future passenger car sales and fuel consumption, are used to study the benefit in CO2 emitted from new passenger cars in this country. The results show that a CO2 benefit of more than 1.6% can be achieved, if a Diesel penetration would reach levels up to 30% on the basis of the current fleet; this advantage could be even 6.1% if the Diesel penetration would reach levels up to 50%. While increasing Diesel penetration and reducing vehicle weight are efficient ways to control CO2 emissions from the transport sector, future fuel consumption of gasoline and Diesel passenger cars would also play a key role in this direction.

Introduction The transport sector is an important source of CO2 in many countries.1,2 The authorities and policy makers look to stabilize or decrease these emissions following, for example, the Kyoto protocol.3 In Western Europe, the Association of European Automobile Manufacturers (ACEA) has proposed a volunteer average fleet reduction of the CO2 emissions to 140 g/km on the New European Driving Cycle (NEDC) in 2008.4 However, the total CO2 emissions of the transport sector increase, mainly due to the increase of the passenger cars fleet. Even if modern vehicles are equipped with higherefficiency engines, the increasing demand for energy by consumers for features such as air conditioning, together with increased vehicle weight and engine management for emission control, are other factors that do not encourage reduction in fuel consumption and furthermore in CO2 emissions. * Corresponding author. † Ecole des Mines de Nantes. ‡ Institut fuer Technische Mechanik, RWTH Aachen. § Present address: Renault, 1, Alle ´ e Cornuel, 91510 Lardy, France. Tel: +331-76 87 84 77. Fax: +331-76 87 82 92. E-mail: [email protected]. | Present address: Ford Forschungszentrum Aachen GmbH. (1) Ellis, J.; Tre´anton, K. Recent trends in energy-related CO2 emissions. Energy Policy 1998, 26 (3), 159-166. (2) Kram, T.; Morita, T.; Riahi, K.; Roehrl, R. A.; Van Rooijen, S.; Sankovski, A.; De Vries, B. Global and Regional Greenhouse Gas Emissions Scenarios. Technological Forecasting and Social Change 2000, 63 (2-3), 335-371. (3) United Nations Framework Convention on Climate Change, United Nations, Kyoto, Japan, 1992, http://unfccc.int/essential_background/kyoto_protocol/background/items/1351.php (4) Internet site of the Association of European Automobile Manufactures (ACEA), www.acea.be

Gasoline and Diesel are the most common types of engines launched in passenger cars. Among the differences in the thermodynamic operation process between gasoline and Diesel engines, they display also differences in the kind of fuel they need to operate. While gasoline engines use gasoline fuel (the name of fuel characterizes the engine type), petrol (Diesel) fuel is needed to operate the Diesel engine. From the thermodynamic point of view, Diesel operation exhibits higher thermal efficiency than the Otto cycle used by gasoline engines, resulting, for the same power demand, in a lower fuel consumption of the Diesel engine than of a gasoline engine. On the basis of the above fuel consumption argument, an efficient way to control the CO2 emissions caused by the transportation sector is to increase the Diesel penetration. A previous study5 showed a significant decrease of CO2 emissions in the United States by the introduction of Diesel passenger cars. This study did not take into account a sales-weighted approach. Such an approach can better predict future CO2 emissions, as it takes into account the real market conditions of each country. The Diesel penetration is quite high in most Western European countries and can even reach 60% in the case of France, Spain, or Austria.4,6 However, the market share is less than 23% in Norway,6,7 and this, after a (5) Sullivan, J. L.; Baker, R. E.; Boyer, B. A.; Hammerle, R. H.; Kenney, T. E.; Muniz, L.; Wallington, T. J. CO2 Emission Benefit of Diesel (versus Gasoline) Powered Vehicles. Environ. Sci. Technol 2004, 38 (12), 3217-3223. (6) Internet site of Eurostat, europa.eu.int/comm/eurostat/ (7) Internet site of the Comity of French Automobile Manufactures (CCFA), www.ccfa.fr

10.1021/ef050070x CCC: $30.25 © 2005 American Chemical Society Published on Web 07/15/2005

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significant increase in recent years. An increase of the Diesel passenger car percentage in this country could be a very efficient way to control CO2 emissions of the transport sector, which were estimated to correspond to 32% of the total CO2 emissions in Norway in 1998.8 The current passenger car fleet in this country is first analyzed, and some probable previsions for the future fleet (2020) are then presented. The benefit on CO2 emissions from the increased penetration of Diesel passenger cars is estimated using several scenarios, taking into account the passenger car sales and fuel consumption. Nevertheless, increased Diesel penetration could have great impact on particulate matter (PM) and NOx emissions. However, current advanced Diesel technologies and future achievements in developing cleaner Diesel engines, in combination with advanced aftertreatment systems, will reduce PM and NOx to the same emissions level of current gasoline engines. Diesel particulate filters (DPF) are already commercially used and will be indispensable to the fulfillment of future PM regulations. Diesel passenger cars equipped with DPF emit similar or even lower PM emissions than gasoline ones.9,10 NOx is another concern, as current Diesel passenger cars emit more NOx than gasoline ones: the European regulatory limits are 0.25 g NOx/km for Diesel passenger cars while they are only 0.08 g NOx/km for the gasoline ones. However, as emissions regulations become more stringent, the difference in NOx emissions between Diesel and gasoline passenger cars will be less important in the future. On the other hand, current Diesel engines emit lower HC and CO emissions than gasoline ones, but this will probably not be true in the future. The simultaneous reduction of PM and NOx of a Diesel engine out emissions based on better homogenization and lower combustion temperatures led to the HC and CO problem of modern and future Diesel engines, especially in the low load (very lean) conditions due to the low temperatures. HC and CO emissions from a gasoline engine are not an issue due to the high conversion efficiency of its three-way catalyst. But this is true only for the port fuel injected gasoline engine, which operates under stoichiometric conditions where the efficiency of the three-way catalyst is high. For stratified conditions of a direct injected gasoline engine, the problem is similar to that of future Diesel engines and requires costly after-treatment. We estimate that in the future the impact on local atmosphere quality will be quite independent of the vehicle type, because the difference between regulatory limits of Diesel and gasoline passenger cars will not be very significant. Assumptions and Methodology Used The statistical data used here are a compilation of data presented in several sources. The Internet sites of the Association of European Automobile Manufacturers,4 Eurostat,6 Committee of French Automobile (8) Transport Sector Report - Baltic 21 Series, No 8/1998, http:// www.baltic21.org/?publications, 8#76, Wuppertal, Germany, 1998. (9) Zervas, E.; Dorlhe`ne, P.; Daviau, R.; Dionnet, B. Repeatability of fine particle measurement on Diesel and gasoline exhaust gas. SAE Technical Paper Series 2004-01-1983, 2004. (10) Zervas, E.; Dorlhe`ne, P.; Forti, L.; Perrin, C.; Momique, J. C.; Monier, R.; Ing, H.; Lopez, B. Inter-laboratory Test of Exhaust PM Using ELPI. Aerosol Sci. Technol., in press.

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Manufacturers (CCFA),7 World Resources Institute (WRI),11 International Road Federation (IRF),12 and Statistics Norway13 are used. The German Federal Motoring Authority (KBA)14 publishes the weight and CO2 emissions obtained on the New European Driving Cycle (NEDC) of the passenger cars certified in Germany in 2003. The current passenger car market in Norway is analyzed and compared with the average market of Sweden, Finland, and the European Union. Only the 15 former countries that were members of European Union are used in this work, as the data of the new 10 countries are only partially available. On the basis of these data, some probable scenarios for the Norwich market in 2020 are established. The changes in CO2 emissions are calculated for different percentages of Diesel penetration in the Norwich market. The CO2 emissions of the KBA file are used, assuming the same annual mileage for the current and future gasoline and Diesel passenger cars. In a first stage, the CO2 emissions are calculated using the current data; in a second one, the future CO2 emissions are estimated taking into account the most probable future technologies impacting fuel consumption.5 This study is limited to CO2 emissions from new, registered passenger cars. No well-towheels analysis or CO2 emissions from trucks or other heavy-duty engines is taken into account. The introduction of other technologies, such as hybrid or fuel cell vehicles, and the emissions of the regulated pollutants are not considered in this study. Results and Discussion Analysis of the Norwich Market. There where 4.5 million inhabitants in Norway, against 5.2 million in Finland and 8.8 million in Sweden in 2003 (Figure 1). The EU population (15 countries) was 377 million. Since 1970, Norway has had a higher average population increase than Finland, Sweden, and EU: 0.36% annual increase in Norway against 0.24% in Finland and 0.10% in average EU. Sweden had an increase of 0.10% until 1997, but since this date, its population decreased. In 2003, there were 1.9 million passenger cars (PC) in Norway, against 2.27 million in Finland and 4 million in Sweden, while there were more than 180 million passenger cars in EU. These passenger car fleets give 417 PC/1000 inhabitants in Norway in 2001, against 414 in Finland, 454 in Sweden, and 487 in EU (Figure 1, middle curves). Since 1970, Norway has had an average annual increase of its PC fleet of 1.8%, while the corresponding values for Finland, Sweden, and EU were 3.6, 0.5, and 2.26%, respectively. Norway had only 192 PC/1000 inhabitants in 1970, but this number increased to reach 301 PC/1000 inhabitants in 1980, 414 in 2000, and 417 in 2001. The Norwich passenger car fleet increases by the new car registrations and by an increase of the average age of the already registered vehicles. In 2003, 88000 new PC were registered in Norway, against 140000 in Finland (11) Internet site of the World Resources Institute, earthtrends.wri.org (12) Internet site of the International Road Federation, www.irfnet.org (13) Internet site of “Statistics Norway”, www.ssb.no (14) Internet site of the German Federal Motoring Authority (KBA), www.kba.de

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Figure 2. Percentage of new Diesel passenger car registrations in Norway, EU average (15 countries members), and some Western European countries.

Figure 1. Lower curves: population of Norway, Sweden, and Finland. Middle curves: number of PC/1000 inhabitants in Norway, Sweden, Finland, and EU (15 countries members). Upper curves: number of the new PC sales/1000 inhabitants in Norway Sweden, Finland, and EU.

and 240000 in Sweden. The new PC market is quite unstable in the three Scandinavian countries (Figure 1, upper curves); however, “Norwich Statistics Net” predicts an increase of new PC sales in the future in this country. In 2003, 19.5 new PC/1000 inhabitants were registered in Norway, which is much lower than the 27.0, 27.3, and 34 PC/1000 inhabitants registered in Finland, Sweden, and EU (Figure 1, upper curves). Moreover, the Scandinavian fleet is older than the average EU age: 9.9, 9.8, and 9.2 years in Norway, Finland, and Sweden, respectively, against 7.6 years in UE in 1999.13,15 The other significant difference between the Norwich market and the market of the other Western European is the percentage of new Diesel passenger car registrations. In most of the EU countries, this percentage was only around 10% in 1980, but increased sharply to reach at an average value of 40% in 2002, while in several countries, like Austria, France, and Spain, this percentage is higher than 60%.4,7 However, this percentage was only 22.7% in Norway in 2003 (Figure 2), after a sharp increase during the preceding years: 9.5% in 2000, 13.4% in 2001, and 17.5% in 2002. Another important parameter taken into account in this work is the type of car segment. Table 1 presents the main characteristics of each of the 11 segments of (15) Panorama of Transport. Statistical Overview of Transport in European Union, European Union, Brussels, 2003, http://epp.eurostat.cec.eu.int/cache/ITY_OFFPUB/KS-DA-04-001-2/EN/KS-DA-04001-2-EN.PDF

the European fleet: average weight, average CO2 emissions on the NEDC, and sales percentage in 2003. The majority of the EU and Norwich markets corresponds to four classes: “economic”, “small car”, “lower medium”, and “upper medium”. However, Table 1 shows that the Norwich market is composed of heavier passenger cars than the EU average. This indicates that for the same number of passenger cars and the same annual mileage, the CO2 emissions are higher in Norway. Comparison of Current CO2 Emissions from Gasoline versus Diesel Cars. Figure 3 shows the CO2 emissions of gasoline and Diesel passenger cars as a function of vehicle weight. For every car type (gasoline or Diesel), no distinction is made between the manual and automatic transmission, because in 2003 more than 68% of the Norwich car fleet was equipped with a manual gearbox. Furthermore, no differentiation is made between direct or indirect injection engines, because the percentage of gasoline direct injection engines is still very low in Norway. Figure 3 shows that CO2 emissions can be linearly correlated with the passenger car weight. Applying least squares to the available data, two linear equations are obtained that best fit the data: CO2 ) (0.1479 × weight) - 7.9 and CO2 ) (0.1133 × weight) - 8.2 for gasoline and Diesel passenger cars, respectively. We assume that an eventual replacement of gasoline passenger cars by Diesel versions would occur within the same segment rather than within the same weight class. The upper curves of Figure 3 present the same data as the lower ones, but using the average weight of each segment. We observe that using the segmentaveraged weight the linear correlation is less good, especially in the segments between 1500 and 2000 kg. This is due to the fact that there is dispersion within each segment in terms of differences in aerodynamics and in combustion and transmission systems, factors which strongly influence the CO2 emissions. Nevertheless, the average difference between the estimated CO2 emissions using each vehicle weight or the average

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Table 1. The 11 Segments of the EU and Norwich PC Fleeta gasoline weight

CO2 emiss ions

Diesel regis trations in 2003 (%)

weight

CO2 emissio ns

registrat ions in 2003 (%)

segment

average (kg)

RS D (%)

average (g/km)

RSD (%)

EU

NOR

average (kg)

RSD (%)

average (g/km)

RSD (%)

EU

NOR

economic small car lower medium upper medium SUV( 4m50)

839 947 1138 1340 1345 1406 1510 1697 1712 1982 2004

9.9 9.6 9.7 9.0 11.7 25.1 8.1 8.0 16.9 10.2 7.0

151 168.5 196 222.5 232.8 265.6 259 266.2 336.3 342.8 342.7

16.1 15.1 14.3 14.1 12.2 25.9 15.0 12.9 27.1 11.3 13.4

10.9 37.5 27.9 13.7 1.6 0.58 4.4 0.78 1.09 0.08 0.66

0.54 22.31 31.42 29.63 7.37 0.38 6.29 0.22 0.20 0.02 1.60

900 1021 1217 1396 1631 1749 1568 1716 1779 1969 1970

9.0 8.7 8.2 8.2 11.3 21.4 6.0 8.2 8.5 8.3 8.0

121.6 138.5 153.6 173.5 227.5 260.2 200.9 196.2 230.4 285.6 256.6

17.2 13.5 12.9 14.9 14.5 16.2 14.5 12.3 11.7 10.6 9.42

0.98 18.0 36.4 23.5 6.41 2.12 4.3 1.35 0.35 0.77 2.0

2.02 15.26 47.74 13.42 0.97 13.43 3.28 0.05 1.44 2.38 2.02

a

RSD: relative standard deviation.

Figure 3. CO2 emissions (in g/km) on the NEDC of gasoline and Diesel cars as a function of vehicle weight or the average segment weight. Error bars estimated for a 95% confidence interval.

weight of each segment is quite low: not more than 1.8% in the case of gasoline passenger cars and 2.8% in the case of Diesel ones. The two new lines: CO2 ) (0.1702 × weight) + 6.7 and CO2 ) (0.1398 × weight) - 11.0 for gasoline and Diesel passenger cars, respectively, are used in this work. Prediction of Future Fuel Consumption. In the future, stricter emission standards will require advanced emission control technologies, like Diesel Particulate Filters or DeNOx technologies, which will increase fuel consumption. The use of powerful electronic hardware to a greater extent allows the utilization of more sophisticated and efficient algorithms for engine management and control. This leads to higher combustion efficiency. As a consequence, improvements in fuel consumption as well as a cleaner combustion process can be achieved. This, in combination with enhancement in vehicle aerodynamics, will improve fuel efficiency. Sullivan et al.5 provide a list of technologies that are expected to increase or decrease future fuel consumption and propose a decrease of about 11% in

gasoline fuel consumption and a decrease of 0-3% in Diesel fuel consumption in 2015. Other works estimate some penalties or benefits in fuel consumption due to future technologies: a 3% penalty from the use of a Diesel Particulate filter,16-18 a 5% penalty from the use of NOx trap technology,18,19 and a 1% penalty from the use of urea SCR.19 Some changes in fuel consumption of advanced gasoline engines and transmissions are given in CAFE.20 Taking into account the above estimations, four different scenarios have been developed in this work: - the Diesel optimistic and pessimistic assumptions (DO, DP) presumes, respectively, 0 and +5% change in Diesel fuel consumption, - the gasoline optimistic and pessimistic assumptions (GO, GP) presumes, respectively, -10% and -5% change in gasoline fuel consumption. After the inclusion of these corrections, the lines linking the CO2 emissions with the passenger car weight are: GO: CO2 ) (0.1369 × weight) - 11.1, GP: CO2 ) (0.1445 × weight) - 11.1, DO: CO2 ) (0.1167 × weight) - 8.9, and DP: CO2 ) (0.1225 × weight) - 8.9. CO2 Changes from the Increased Penetration of Diesel Passenger Cars in Norway. On the basis of current sales and segment distribution in Norway and in the EU, we aim to construct many realistic scenarios, which take into account current differences between the two markets and assess the potential of reducing CO2 emissions. Of course, we do not expect that sales and segment distribution will remain the same in the future due to the dynamic nature of the extended economic environment and probably changes in political decisions regarding fuel and car taxation. However, prediction of future variations in market share and segment distribution is beyond the scope of this study. Thus, 20 scenarios are constructed to calculate the changes in (16) Stamatelos, A. M. A review of the effect of particulate traps on the efficiency of vehicle Diesel engines. Energy Convers. Manage. 1997, 38, 83. (17) Johnson, T. V. Diesel emission control in review. The last 12 months, SAE Technical Paper Series 2003-01-0039, 2003. (18) Lambert, C.; Hammerle, R.; McGill, R.; Khair, M.; Sharp, C. Technical advantages of urea SCR for light-duty and heavy-duty Diesel vehicle applications, SAE Technical Paper Series 2004-01-1292, 2004. (19) Highway Diesel Progress Review, USEPA: Washington, DC, June 2002, http://www.epa.gov/air/caaac/Dieselreview.pdf (20) NRC (National Research Council). Effectiveness and Impact of Corporate Average Fuel Economy (CAFE) Standards, National Academy Press: Washington, DC, 2002.

current/DO/DP/DO/DP current/GO/GO/GP/GP

current/GO/GO/GP/GP current/GO/GO/GP/GP

current/GO/GO/GP/GP current/GO/GO/GP/GP

current/DO/DP/DO/DP current/GO/GO/GP/GP

as the current Norwich h ones average of the current Norwich and EU as the current Norwich ones as the current EU 16-20

C: CURRENT. a

11-15

AVERAGE-CFC // AVERAGE-GODO // AVERAGE-GODP // AVERAGE-GPDO // AVERAGE-GPDP AVERAGE1-CFC // AVERAGE1-GODO // AVERAGE1-GODP // AVERAGE1-GPDO // AVERAGE1-GPDP EU-CFC // EU-GODO // EU-GODP // EU-GPDO // EU-GPDP 6-10

as the current Norwich ones average of the current Norwich and EU ones average of the current Norwich and EU ones as the current EU C-CFC // C-GODO // C-GODP // C-GPDO // C-GPDP 1-5

Diesel assumptions for the FC

gasoline segment distribution

assumptions for the future PC sales in Norway

number of PC sales namea scenario

CO2 emissions for different percentages of Diesel penetration (Table 2). They can be divided in four groups: 1. The scenarios using the current Norwich new passenger car sales (scenarios 1-5, named CURRENT). 2. The scenarios using the average value between the current Norwich and the current EU new passenger car sales. The percentage of each segment corresponds to the average value between the current Norwich and the current EU percentages (scenarios 6-10, named AVERAGE). 3. The scenarios using the average value between the current Norwich and the current EU new passenger car sales, by maintaining the current Norwich segment distribution (scenarios 11-15, named AVERAGE1). 4. The scenarios using the current EU new passenger car sales (scenarios 16-20, named EU). CO2 Change using the Current Diesel Penetration. The first comparison between all scenarios is made in the case of current Diesel penetration (Figure 4). The scenarios using the Diesel optimistic and pessimistic (DO and DP) fuel consumption give quite similar results, because the current Diesel penetration is quite low. The scenarios using the gasoline and Diesel optimistic fuel consumption (DO and GO) give always slightly higher CO2 benefit, or lower CO2 change, than those using the pessimistic one (DP and GP), because fuel consumption is lower in the first case. Influence of Future Fuel Consumption Using the Current Sales. On the basis of the current PC sales in Norway and assuming they will remain unchanging, we expect a decrease in future CO2 emissions for all assumptions of future fuel consumption, (CURRENT scenarios of Figure 4). This decrease will be about 3-4% in the case of a small decrease in gasoline fuel consumption (the two GP assumptions), but will reach 7-8% in the case of a greater decrease (the two GO assumptions), indicating the major importance of future fuel consumption and its implications in CO2 emissions. Influence of the Number of Passenger Car Sales by Maintaining the Current Fuel Consumption. Assuming that current fuel consumption remains the same, there is a strong relation between CO2 emissions and passenger car registrations. Considering no changes in future fuel consumption, we observe an increase in CO2 emissions for all scenarios presented in this work with increasing passenger car registrations (scenarios EUCFC > AVERAGE1-CFC > AVERAGE-CFC > CURRENT-CFC). However, Figure 4 shows that the CO2 change from the increase of the total new car number is partially counteracted by the use of lighter passenger cars. This is evident if we consider the increase in CO2 between scenarios AVERAGE-CFC and AVERAGE1CFC, where the sales are maintained constant, while the assumed segment distributions are different between both cases (the CO2 increase is 24 and 37%, respectively) These results indicate that beside the influence of sales, there is a great importance of vehicle weight and segment distribution on CO2 emissions. The difference in CO2 emissions between scenarios CURRENT-CFC, AVERAGE-CFC, and AVERAGE1-CFC indicates that there might be a synergy effect caused by simultaneous change in sales and segment distribution.

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Table 2. The 20 Scenarios Used

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Figure 4. Lower bars: Change in total CO2 emitted from new passenger cars, in the case of no supplementary introduction of Diesel passenger cars in Norway, for the different sales and fuel consumption scenarios used. Upper bars: supplementary change in total CO2 emissions emitted from new passenger cars, for a 10% supplementary penetration of Diesel passenger cars.

Influence of New Passenger Car Sales Using the Future Fuel Consumption. It was assumed that future gasoline fuel consumption will decrease by 5 or 10%. If the future optimistic gasoline fuel consumption is taken into consideration, the CO2 decrease will be quite important (6.6-7.7%) in the case of the two scenarios using the actual sales (CURRENT-GO). However, there will be an important CO2 increase in the case of future sales: 14.2-15.6% in the case of AVERAGE-GO scenarios, 26.3-27.9% in the case of the AVERAGE1-GO ones, and 45.4-47.0% in the case of more important new passenger cars sales (the two EU-GO scenarios). In the case of gasoline pessimistic fuel consumption (GP, -5%), the CO2 benefits are lower than for the previous case. The CO2 changes for the CURRENT-GP, AVERAGE-GP, AVERAGE1-GP, and EU-GP scenarios are -3 to -4%, +19-20%, +31-33%, and +51-53%, respectively. These results indicate the great importance of future fuel consumption and vehicle weight on the total CO2 emissions from new passenger cars. CO2 Change as a Function of Diesel Penetration. Figure 5 presents the change on CO2 emissions as a function of Diesel penetration. It is clearly shown that, for each scenario, the CO2 benefit is more important at increased Diesel penetration. The four groups of scenarios form four quite parallel groups of lines. Naturally, the CO2 emissions increase with the number of passenger car sales. It is interesting to observe that only the CURRENT scenarios (maintaining the current Norwich sales) would lead to CO2 decrease with increasing Diesel penetration. Assuming the AVERAGE, AVERAGE1, and EU segment distribution, CO2 emissions increase even for 100% Diesel penetration. As can be seen in Figure 5, this last observation is independent

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from the fuel consumption scenarios. This means that, despite all future technological achievements regarding improvements in fuel consumption direction, the CO2 emissions will increase in the future, if Norwich new passenger car sales increase. This is a quite pessimistic observation, which indicates that all innovations contributing to reduce fuel consumption can be overcompensated by an adverse vehicle segment distribution and increased passenger car sales. 30% and 50% Diesel Penetration, Using the Current Fuel Consumption. Two cases will be particularly examined: 30% and 50% Diesel penetration. The total CO2 emitted from new passenger cars decreases by 1.6 and 6.1%, respectively, in the case of actual sales (CURRENT-CFC). This indicates that an important CO2 benefit can be immediately achieved in this country by the increased percentage of Diesel passenger cars. However, this benefit is lower and even negative in the case of increased passenger car sales. A 30% penetration increases CO2 emissions by 22, 35, and 55% in the case of the AVERAGE-CFC, AVERAGE1-CFC, and EU-CFC scenarios, respectively. A 50% penetration gives better results: an increase of 17, 28, and 47% in the case of the same scenarios. It must be noticed that the above results are better than those obtained in the case of 0% supplementary Diesel penetration which present an increase of 24, 37, and 57%, respectively, for these three scenarios. These results show that, if the Norwich new passenger car sales approach the EU average sales, a quite important increase in total CO2 emissions will occur. A higher Diesel penetration could help to keep the increase in CO2 emissions under control in that case. 30% and 50% Diesel Penetration, Using the Future Fuel Consumption. The CO2 emissions are always lower in the case of the future fuel consumption compared to the current one (CFC). This difference is 2.5-12 percentage units in the case of the 30% Diesel penetration and 1-10 percentage units in the case of 50%. Naturally, this benefit is more important in the case of optimistic gasoline or Diesel fuel consumption. These results indicate that a control of future fuel consumption will help to control the future CO2 emissions. 10% Supplementary Diesel Penetration. In all cases studied, a supplementary Diesel penetration of 10% gives the same change of the total CO2 emissions (Figure 4, upper curves). This benefit increases with the number of passenger cars registrations (EU > AVERAGE1 > AVERAGE > CURRENT) and can reach 3.7% in the case of scenario EU-CFC. CO2 Change, Using the Future Fuel Consumption. Looking at the different scenarios which consider future fuel consumption, the following ranking, from high to low benefit in CO2 emissions with increasing Diesel penetration, is observed: GPDO > GPDP > GODO > GODP. This trend is evident considering the slope of the corresponding curves in Figure 5. The reasons are that the first two cases consider a pessimistic gasoline fuel consumption, which increases the difference between gasoline and Diesel CO2 emissions, while the last two scenarios consider an optimistic gasoline fuel consumption, which reduces this difference. The assumptions GPDO and GODO give, respectively, more

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Figure 5. Change in the total CO2 emitted from new passenger cars from the increased percentage of Diesel passenger cars in Norway, for the different scenarios used.

CO2 benefit than the GPDP and GODP, because they take into account an optimistic Diesel fuel consumption, which increases the difference between gasoline and Diesel CO2 emissions, contrary to the last two assumptions which decrease this difference. The CO2 emissions of the Diesel optimistic fuel assumption (DO) are always lower than the scenarios using the current fuel consumption (CFC). This difference is higher in the case of the current Diesel penetration and decreases with the increased passenger cars sales. Even in the Diesel pessimistic fuel consumption scenarios (DP), the CO2 emissions decrease in comparison to scenarios with the current fuel consumption (CFC). In the DP scenarios, the CO2 emissions are retained lower than in the CFC scenarios, even for high Diesel penetration, which can reach 60 to 80% levels, depending on the evolution of gasoline engines with respect to fuel consumption issues. For higher Diesel penetrations, the CO2 emissions surpass the emissions of the CFC scenarios. This last result indicates that the control of future Diesel passenger car fuel consumption is an important factor for the CO2 emissions. The CO2 benefit can even be negative in the case of an increased future Diesel fuel consumption for very high Diesel penetrations. Conclusions The aim of this work is to estimate the CO2 benefit from the increasing penetration of Diesel passenger cars in Norway’s car fleet. The number of new PC registrations in Norway generally increased in recent years, but remains at lower levels than the EU average. The Norwich market is composed of heavier cars than the

EU average, and the percentage of new Diesel registrations is only 22.7% against more than 40% for the EU average. Gasoline and Diesel passenger cars have a quite good relationship between CO2 emissions and passenger car weight on the basis of the European driving cycle (NEDC). Another correlation can be found between CO2 emissions and the average weight of each segment. Four assumptions are used for the future fuel consumption: Diesel optimistic assumption (DO) with no fuel consumption change, Diesel pessimistic assumption (DP) with an increase of 5% in FC, gasoline optimistic assumption (GO) with a decrease of 10% in FC, and gasoline pessimistic assumption (GP) with a decrease of 5% in FC. Twenty scenarios are constructed to predict the CO2 benefit from the increased percentage of Diesel passenger cars, taking into account the new passenger car registrations, their segment, and the fuel consumption. If the future passenger car registrations remain as the current ones and the fuel consumption of future gasoline passenger cars decreases, the CO2 emissions from new passenger cars will decrease by 3-8% in the future. The CO2 emissions increase with the number of passenger car sales, even if the vehicle segment distribution moves down to lighter vehicles and can partially control the CO2 increase. If the new sales reach the same level as the average calculated by the current Norwich and the EU average, in terms of new passenger car sales and segment distribution, the total CO2 emissions will increase by 24%. If the new passenger car registrations increase keeping the current Norwich segment distribution, the CO2 emissions will increase

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by 37%, indicating the high importance of vehicle segment distribution. A 30% or 50% Diesel penetration decreases the total CO2 emissions from new passenger cars 1.6 and 6.2%, respectively, in the case of the current sales and current fuel consumption. The AVERAGE-CFC, AVERAGE1-CFC, and EU-CFC scenarios give an increase of 22, 35, and 55%, respectively, for a penetration of 30%, and an increase of 17, 28, and 47%, respectively, for a penetration of 50%. These values are lower than those of the actual Diesel penetra-

Zervas and Bikas

tion. A supplementary penetration of Diesel passenger cars of 10% gives a CO2 benefit which can reach 3.7%. The introduction of Diesel passenger cars and the decrease of vehicle weight will help to reduce the total CO2 emitted from new passenger cars. The future fuel consumption is the other key parameter for this control. It must be noticed that if future Diesel fuel consumption increases, a very high Diesel penetration can be negative to CO2 emissions. EF050070X