Hybrid Electric Vehicles

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Hybrid Electric Vehicles

An alternative for the Swedish market?

Karl-Erik Egebäck

Sören Bucksch

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TITEL/TITLE

Hybrid Electric Vehicle. An alternative for the Swedish market?

FÖRFATTARE/AUTHOR

Karl-Erik Egebäck, Autoemission K-E E Consultant, Sören Bucksch, KFB

SERIE/SERIES KFB-Report 2000:53 ISBN 91-89511-08-5 ISSN 1104-2621 PUBLICERINGSDATUM/DATE PUBLISHED October, 2000 UTGIVARE/PUBLISHER KFB – Swedish Transport and

Communications Research Board, Stockholm KFBs DNR 2000-388

SUMMARY

See page 8

KFB Reports are sold through Fritzes’, S-106 47 Stockholm. Other KFB publications are ordered directly from KFB

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Hybrid Electric Vehicles

An alternative for the Swedish market?

Karl-Erik Egebäck

Sören Bucksch

This report was originally written in Swedish and it has now been updated and translated into English

during July – September year 2000 by

Karl-Erik Egebäck

and

Liz Egebäck Foxbrook

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TABLES

Table 1. Environmentally classified parameters and components in gasoline in Sweden (MK1)....23

Table 2. Environmentally classified parameters and components in diesel oil in Sweden...25

Table 3. Composition of the Danish natural gas from the North See....28

Table 4. Natural gas in the world – resources, production and ventilated/flared, year 1997....28

Table. 5. The composition of purified biogas according to an analysis....33

Table 6. Summary of physical and chemical characteristics of various engine fuels....34

Table 7. Emission Standards for light duty vehicles EU. Source: Auto/Oil II....37

Table 8. EU-Standards for passenger cars and other light-duty vehicles....40

Table 9. EU-standards for heavy-duty diesel fueled engines. Source: EU Directive 1999/96/EC....40

Table 10. EU-standards for heavy-duty diesel fuelled and gaseous fueled engines....41

Table 11. Comparison between different types of fuel cells....51

Table 12. Anode and cathode reactions of SOFC...52

Table 13. Anode and cathode reactions in a fuel cell with PEM....53

Table 14. The mass of the fuel cell and an estimation of how the mass can be reduced....55

Table 15. Development of lead acid batteries EU. Source: Cooper and Moseley, 1998....63

Table 16. Vehicle manufacturers and their choice of battery....64

Table 17. Comparison between a series hybrid and a conventional drive system. (Source: Mercedes (Abthoff et al., 1998)....79

Table 18. Fuel consumption (as gasoline) for Toyota Prius and some other vehicles with low fuel consumption..82 Table 19. Some particulars for a number of hybrid buses and some trucks with hybrid systems....88

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Table 21. The effect of charging strength on the working efficiency of charging and on the durability...109

Table 22. Japanese 10–15 mode emission standards and emissions for Toyota Prius....117

Table 23. Result from emission tests according to the US EPA FTP-75 test procedure....118

Table 24. Result from emission tests according to the US EPA HFET test procedure....118

Table 25. Estimation of the cost levels for various details in the hybrid system/vehicle....121

Table 26. Evaluation of various batteries....122

Table 27. Estimate of risks for yearly incidence of cancer associated with air pollution.....124

Table 28. Unit risk factors. Cancer mortality risks from life-long exposure to 1 µg/m3*_...128

FIGURES

Figure 1. Series hybrid system. (Source: DOE, USA)....18

Figure 2. Parallel hybrid system. (Source: DOE, USA)....19

Figure 3. Specific energy used in a gasoline fuelled car and a series hybrid when driven on road (Iwai, 1998)...20

Figure 4. Estimation concerning the use of various fuels in a fuel cell. Source: Sasaki, 1999....35

Figure 5. The relationship between the displacement of the engine and its efficiency....38

Figure 6. The specification (left) of the engine shown in the figure (right)....39

Figure 7. Diagram for control of engine, DIATA. Source: Breida 1998....43

Figure 8. The HPCR fuel system with its components. Source: Breida 1998....44

Figure 9. Typical torque curve and power curve respectively for a Stirling engine....46

Figure 10. Stirling engine. Source: USCAR, 1999....47

Figure 11. GM’s gas turbine. Source: USCAR, 1999....48

Figure 12. Basic principals of fuel cells. Source: US Department of Defence....51

Figure 13. The three sections of a fuel cell: fuel processor, stack of fuel cell and DC/AC transformer. Source: US Department of Defence....52

Figure 14. Fuel cell with solid oxides (ceramic). Source. US Department of Defense....53

Figure 15. Components of a fuel cell system....54

Figure 16. Organization for the development of batteries. Source: Sutula et al., 1998....59

Figure 17. Specific effect respective to specific energy for various batteries....65

Figure 18. Mussel diagram over fuel consumption for a 1.25 liter gasoline engine, modified by Ecotraffic (Sweden). Source: (Menne et al., 1996)....67

Figure 19. The Japanese 10-15 mode cycle....71

Figure 20. Different cases for calculation of the braking energy recovery (0-0.15g)....71

Figure 21. Improvement of fuel consumption for a series hybrid when tested according to the...72

Figure 22. Potential for different automotive system. Source: NRC, 98....73

Figure 23. Mercedes hybrid car Necar 3, equipped with fuel cells....79

Figure 24. Mercedes hybrid car Necar 3, equipped with fuel cells....80

Figure 25. Schematic configuration of the hybrid system from Toyota....81

Figure 26. Schematic picture of Ford’s hybrid car(”LSR”). Source: Automotive Engineering International/February 1999). Reference: (Buchholz, 1999)...83

Figure 27. Ford’s hybrid system PTH with gasoline engine. Source: Buschhaus et al, 1998....84

Figure 28. Scematic configuration of the hybrid system from Nissan. Kitada et al., 1998....85

Figure 29. Nova Transit Bus. Source: Whartman, 1998....90

Figure 30. Volvo hybrid delivery truck....91

Figure 31. Power unit (APU) for hybrid vehicle....93

Figure 32. Control systems, internal combustion engine and the emission control system. Source: Monrad och van der Weijer, 1998....94

Figure 33. Mitsubishi aerial working truck. Source: (Horii et al., 1998)....95

Figure 34. Efficiency improvement by hybrid strategy. (Source Takaoka et al., 1998)....101

Figure 35. Comparison of fuel consumption at different driving modes....102

Figure 36. Mitsubishi service truck. Comparison of energy used between a hybrid truck and a diesel truck. Source: Horii et al., 1998....104

Figure 37. Mitsubishi working truck. Comparison of energy used between a hybrid truck and a diesel truck. Source: Horii et al., 1998....105

Figure 38. Energy efficiency of same important component of a HEV. Source: Horii et al., 1998....105

Figure 39. Tests with parallel hybrid vehicle developed at the University of California Davis. Source: Duoba, M. and Larsen R., 1998...111

Figure 40. Tests with series hybrid vehicle developed at the West Virginia University. Source: Duoba ,M. and Larsen R., 1998...112

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Figure 42. Emissions for Mercedes series hybrid vehicle (prototype)....117

Figure 43. Cost of various driving systems. Source Mercedes Benz....120

Figure 44. Exemple of relevant aldehyds. Source: Egebäck and Westerholm, 1997....126

Figure 45. Examples of relevant alkenes. Source: Egebäck and Westerholm, 1997....126

Figure 46. Examples of relevant alkyl nitrites. Source: Egebäck and Westerholm, 1997....127

Figure 47. Examples of relevant Monoaromatic compounds....127

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1 SUMMARY

According to the Swedish National Encyclopaedia the word hybrid comes from the Latin

word (h)i’brida, hy’brida which means “cross” or “bastard” and its origin is the Greek word

“bastard”. If one continues to the phrase hybrid vehicle the encyclopaedia describes this

as “a vehicle which is fitted with more than one type of energy transformer and energy storage system for its propulsion, and where the drive or the regulating system of the vehicle determines which type shall be used. The energy converter can, for example, be a heat engine, a hydraulic engine, an electric engine or a fuel cell. Energy storage can be carried out by means of a chemical, kinetic, electric or hydrostatic energy storage system or by means of heat storage. In the future the development of hybrid electric vehicles will be of special interest since they provide an intermittent freedom of exhaust gases”.

The object of this report, which has been produced within The Swedish Transport and Communications Research Board’s (KFB’s) Electric and Hybrid Vehicle Program, is to assemble information on and describe the situation for the development of hybrid vehicles and various alternatives within this field of development. In the report the description is concentrated mainly on the combination of combustion engine and electric battery, which is the most common combination in present day hybrid vehicles. In order to take a glimpse into the future even the combination of fuel cells and electric battery is described.

Among the important factors for vehicle owners are the cost of the vehicle, the fuel and the use of the vehicle. For alternative vehicles the cost of the vehicle is usually higher than for an “ordinary” vehicle, quite simply because the alternatives are manufactured in smaller series. For the vehicle manufacturer and even for the buyer of the vehicle it can therefore be of great importance that as large a market as possible is obtained for the alternative vehicle, for example electric vehicle or hybrid vehicle. One way for the vehicle manufacturer to quickly create a large market can be to sell the cars at a lower than usual price, for a period of time. Examples of this are electric vehicles, which are manufactured by Ford and GM and the hybrid car Prius, which is manufactured by Toyota. One can ask the question as to whether the environmental advantages would be a sufficient reason for paying the higher price, if the vehicles were not subsidized or if the running costs had not been decreased by alterations in taxation.

In present day hybrid systems one of the energy converters consists of electric batteries. A continued, comprehensive development of batteries is required in order to improve the technique and to reduce the costs. One important reason for introducing hybrid vehicles is to improve fuel economy, so that a considerable part of the report is devoted to this. The distribution of fuel and electricity is described briefly. The costs are also described briefly due to the fact that techniques of hybrid vehicles are so new that there is not yet sufficient information on which to base a clear picture of the costs. This can also be said of the testing methods for the hybrid vehicles in question, since no standardized testing methods have yet been determined. The effect on emissions is not completely clear, but present day development certainly seems to be leading in the right direction.

It is obviously not especially difficult to find problems in a technique development which has not yet been tested on the open market other than on a small scale. The report suggests which are judged to require further technical development. The real barrier to a speedy introduction of the hybrid system is probably the cost.

There are several questions, concerning vehicles, which have been in the limelight for the last 30 to 40 years, namely emissions, fuel consumption and safety. When we discuss running

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hybrid vehicles and the possible advantages of them, it is chiefly the following points which give rise to a problem of greater or lesser magnitude.

Vehicle emissions

Energy conversion and fuel savings Battery development

Costs

The assessment which has been carried out and is presented in this report has provided a basis for the evaluation of some different lines of development for hybrid systems. In the short term (0-5 years) the picture is relatively clear since it takes time and money to develop and present new ideas. It seems clear that in the case of light-duty vehicles a continued effort will be put into developing the hybrid system, to some extent. In the case of heavy-duty vehicles there is a certain degree of uncertainty as far as the development of hybrid busses is concerned, due to the fact that it is generally private bus companies who carry out the development. Certainly this development generally takes place in conjunction with the manufacturers, but the question is how strongly the manufacturers are engaged in the development work. Under these circumstances strong support from the authorities is required in order for the development work to be carried out, since such activities are generally expensive.

The light-duty hybrid electric vehicles that have hitherto been developed are mainly parallel hybrids. If the development of hybrid systems takes place it will most certainly concern light-duty vehicles, and these will be parallel hybrids equipped with an otto or a diesel engine, depending on which of these the manufacturers wish to back.

The requirement for energy efficiency is easier to meet with a diesel engine in the hybrid system. Of all the hybrid systems which have been studied for this report, it is Ford’s parallel hybrid with a diesel engine which takes top place as far as energy is concerned. Generally speaking diesel engines have experienced a period of positive development, especially during the last decade. This is due, to a great extent, to the fact that diesel oil has been successively improved, and this is particularly true for Sweden. It now remains to be shown that the current development of purification techniques for the reduction of nitrogen oxides and particulate emissions will provide a system with such a good durability that it can be accepted for use during a long period. If such a development can be demonstrated and the development of diesel oil continues to give good results then the diesel engine can prove to be a suitable alternative for, amongst others, vehicles with hybrid systems (both light-duty and heavy-duty).

The efficiency of the otto engine will not reach the efficiency level of the diesel engine. However, continuous development of the otto engine is taking place in order to improve the fuel efficiency. The fuel consumption of an advanced otto engine with direct fuel injection is somewhere between that of the diesel engine and of the conventional otto engine.

Where the emission of exhaust gases and noise are concerned one can reverse the argument. In the short term it can be difficult to achieve the same emission requirements for diesel driven vehicles as for petrol driven ones. Unfortunately the direct injected otto engines developed up to the present day have shown a higher level of the emissions of oxides of nitrogen and particles than their conventional counterparts. Vehicles with direct injected otto engines will also probably achieve the same emission performance as the vehicles fitted with conventional otto engines in the not too distant future.

When determining the development of hybrid driven heavy-duty vehicles it should be remembered that there are clear differences between light-duty and heavy-duty vehicles. One difference is that the heavy-duty vehicles have, as a rule, more space available for additional and heavier equipment than have passenger cars. However there is no absolute solution,

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especially for busses in city centers, which have a limited space unless some passenger space is sacrificed. The general opinion is, however, that heavy-duty vehicles can carry a relatively heavier packet of batteries than a passenger car. Providing that one can charge the batteries from the mains, this could mean that a system with series hybrids is advantageous. But it is not completely certain that this is a correct conclusion for all types of heavy-duty vehicles. If one considers the whole scale of heavy-duty vehicles, from light trucks to busses, there can be many cases where a parallel hybrid is a better alternative than a series hybrid. The recommendation is therefore that each type of vehicle and each possible use of the vehicle should be considered when choosing a hybrid system.

In the long term it is not easy to foresee the development but in the case of hybrid electric vehicles some possible scenarios are already in sight, and these could be achieved during the coming 5 to 15 years:

1. Parallel hybrids will come to be the dominant system for light-duty vehicles and possibly even for certain other groups of vehicles.

2. Series hybrids will come to be used solely for heavy-duty vehicles.

3. The present day development of fuel cells will lead to more manufacturers paying greater attention to electric or hybrid vehicles with fuel cells.

The development of fuel cells will most probably continue, at least at the present day level. Technical speaking it is likely that vehicles fitted with fuel cells will function satisfactorily until mass production is begun. A hinder for the development of a larger market is however the cost. Will the average vehicle owner be able to afford such a vehicle?

A vehicle powered by a fuel cell can be considered to be an electric vehicle. If the fuel cell continues to be developed at the same pace as at present, so that a reasonable price level will be achieved on the market, the market for electric vehicles will also be favored.

In the report the use of series hybrid vehicles is estimated to be limited to heavy-duty hybrid vehicles. Hybrids will not be likely to be relevant for heavy-duty vehicles, with the exception of those trucks which operate in city centers, i.e. trucks which are used for the distribution of goods to shops, as garbage vehicles and as certain types of working vehicle for service purposes. Continued development of the hybrid system for busses seems uncertain for various reasons. It is chiefly local bus companies and private contractors who develop hybrid busses, leading to uncertainty in the continuance of the development.

If there is a technical breakthrough in the manufacture of batteries and simultaneously the manufacturers increase their efforts to develop hybrid vehicles, the situation can be changed so that there is a speedier introduction of hybrid systems for heavy-duty vehicles.

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2 INTRODUCTION

According to the Swedish National Encyclopaedia the word hybrid comes from the Latin word (h)i’brida, hy’brida which means “cross” or “bastard” and its origin is the Greek word

“bastard”. If one continues to the phrase hybrid vehicle the encyclopaedia describes this as “a

vehicle which is fitted with more than one type of energy transformer and energy storage system for its propulsion, and where the drive or the regulating system of the vehicle determines which type shall be used. The energy converter can, for example, be a heat engine, a hydraulic engine, an electric motor or a fuel cell. Energy storage can be carried out by means of a chemical, kinetic, electric or hydrostatic energy storage system or by means of heat storage. In the future the development of hybrid electric vehicles will be of special interest since they provide an intermittent freedom of exhaust gases”. The hybrid vehicles described in this report are hybrid electric vehicles (HEVs) – a commonly used definition of a hybrid electric propulsion system vehicle equipped with an internal combustion engine as one power source and electric traction motor as the other power source.

Today there are in principal two types of hybrid system the “series hybrid” and “parallel hybrid”, see section 4 for a detailed description of these two systems. In this report the presentation about hybrid systems will primarily be concentrated to the combination internal combustion engine and electric motor which is today the most common combination for hybrid vehicles. However, when looking into the future, even the combination fuel cells and electric batteries will be described. A question that seems to be difficult to answer is what type of hybrid system will be the dominant one on the market for light-duty hybrid vehicles. Today it is likely that the development of hybrid systems for light-duty vehicles will be concentrated to the parallel system. However, this does not necessarily mean that series hybrid systems will be an uninteresting alternative in the long run. For heavy-duty vehicles it is likely that the series hybrid system will be the commonly used system. There are also other systems of types which can be seen to lie somewhere between series and parallel hybrids. Since the number of hybrid vehicles is limited and since some of them are only prototypes – except, possibly, in the case of Japan – the car owners are generally not familiar with this type of vehicles. It can also be said that long term testing of hybrid vehicles is so far rather limited. The fuel to be used in hybrid vehicles (and also in fuel cell vehicles) is a question of high importance since one strong motive for the use of the hybrid technology (and electric vehicles) is to reduce the emissions and to improve the fuel economy. In one section of this report dealing with the fuel cycle it is shown that the technology used for reforming the fuel in the vehicle will have a significant influence on the fuel economy. However, in this case, the practical possibility of storing fuel in the vehicle may be seen to be more important than energy efficiency. The classical example concerning the storage, distribution and use of gaseous fuels as fossil gases (natural gas and others) contra storage, distribution and use of liquid fuels is valid even in the case of fuel cells.

Some of the key questions for the car owner are of course the cost of the vehicle when purchased, the fuel and the use of the vehicle. For alternative vehicles the of purchasing the vehicle is generally higher than for the commonly used commercial vehicles since the alternative vehicles are mostly produced in low quantities. For the car manufacturer but even for the purchaser of the vehicle it will be an advantageous to create a large market for an alternative such as the electric vehicle or the hybrid. One possibility for the manufacturer to create a larger market may be to sell the vehicles at a lower price during the introduction of the actual vehicle, resulting in a reduced profit. Examples which can be mentioned are the

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electric vehicles manufactured and sold in the USA and the hybrid vehicle Prius manufactured by Toyota, Japan. It can also be asked whether the desire of the buyers of alternative vehicles to keep the pollution as low as possible would be strong enough for them to buy such vehicles if the costs of the purchasing and using these vehicles were to be subsidized. These and related questions are discussed in some papers which are referred to in this report.

Since many of the articles and some reports of investigations in papers give somewhat similar information, a selection of the information has been carried out done (not systematic, however) in order to reduce the number of references. The fact that some of the information in the papers may old or not relevant for hybrid vehicles and therefore not valid for this report has been considered when selecting the literature references. The development of batteries is one of the subjects which are not easy to describe since there is a great number of report and other information to take notice of and that there may be a difference between the requirement for batteries for hybrid vehicles compared with requirements for batteries to be used in electric vehicles. In hybrid vehicles charging and discharging of the battery occurs in continuously repeated cycles during driving in traffic. This is true to some extent even for electric vehicles using regenerative braking (the energy released during decelerations – “braking”- is recycled to the battery) and this recharging must certainly be taken into account when developing batteries for hybrid vehicles and also for electric vehicles using a system for regenerative braking. One difference between a electric vehicle and a hybrid vehicle is that even the capacity for depth-of-discharge (DOD) may have to be larger for a battery used in an electric vehicle than for a battery used in a hybrid vehicle. A drawback for hybrid vehicles (and to a higher extent for electric vehicles) is that the cost of the battery is high. This is especially so for light batteries with high energy density; (in one case the cost of the battery pack was higher than purchase price of the vehicle). It seems therefore to be necessary to reduce the cost of the battery in order to use it in a vehicle produced in a large quantity. This should be made possible by an improvement in the production of the batteries.

The USA constitutes a large part of the global market for vehicles and during the last decade the development of alternative vehicles has to a large extent been influenced by the program Partnership for a New Generation of Vehicles (PNGV) started 1994. The program is based on an agreement between the US Government (including 12 Departments) and Chrysler, Ford and General Motors. The program is directed towards passenger cars and the goal of the project is to improve the fuel economy of these vehicles to 80 MPG (approximately 3 liters /100 km). Further aims are as follows:

The first goal is to: ”Significantly improve national competitiveness in manufacturing”. This

means an improvement of the productivity of the US base for manufacturing by an significant upgrading of the US manufacturing technology, including adoption of agile and flexible manufacturing and reduction of costs and lead times, while reducing environmental impact and/or improving quality.

The second goal is to: ”Implement commercially viable innovation from ongoing research on

conventional vehicles”, which among other things means to pursue advances in vehicles

leading to improvements in fuel efficiency and emissions while pursuing safety advances to maintain safety performance. The car industry will commit itself to applying those commercially viable technologies that are expected to significantly increase vehicle fuel efficiency and improve emissions.

The third goal is to: ”Develop a vehicle to achieve up to 3 times the fuel efficiency of today’s

comparable vehicle”. This is a “fuel efficiency improvement of up to three times the average

of Concorde/Taurus/Lumina, with equivalent customer purchase price of today’s comparable sedans type of vehicles adjusted economics”. The requirement for fuel economy is 80 MPG

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(approx. 3 l/100 km). Other requirements include emission standards as Tier II, which are; 0.125 for HC, 1.7 for CO and 0.2 for NOx, in g/mile at the odometer reading of 100 000 miles,

which is equal to HC: 0.078, CO: 1.06 and NOx: 0.124 in g/km at the odometer reading of 160

000 km. According to PNGV at least 80 % of the vehicle has to be recyclable or to quote ”Achieve recyclability of at least 80 %”.

This report is prepared for The Swedish Transport and Communications Research Board (KFB) and is based on the results and experiences which have been presented in the international literature. The impression is that there is a great optimism, especially about the development of fuel cells. Unfortunately this optimism may be misplaced since the barriers are described as fewer than those which will have to be solved in reality. This optimism may lead to the time frame for the remaining development of fuel cells being shortened unrealistically. Fuel cells are certainly not a new invention, but the application to our commonly used passenger cars requires that they be produced at a reasonable cost and that they can be proven to be efficient energy transformers without having negative effects on the environment or causing other problems.

The aim of this report, which has been prepared within KFBs program for electric and hybrid vehicles, was to combine and describe the situation concerning the development of hybrid vehicles and the different alternative for this development. This report will constitute one of the reports on which the final report for the electric and hybrid vehicle will be based.

The disposition of this report is as follows: firstly there will be a discussion of the complexity of the development and introduction of reformed or new automotive fuels and new technologies for propelling motor vehicles. After this there will be an introductory description of two different hybrid systems according to the terminology used for such systems. Since both gasoline and diesel oil and even alternative fuels may be used for the actual energy transformers, the internal combustion engine or fuel cells, a rather extensive description of the different fuels is given. In the case of the above mentioned two types of energy transformers, it is expected that a considerable development will occur in addition to that which has already occurred. Since this will also have an impact on the development of the vehicles, the expected changes will be discussed in two of the sections. In present day hybrid systems one of the energy transformers is the battery and in order to increase their life cycle, and thereby even the costs, further extensive research and development has to be carried out. An important aim of the introduction of hybrid vehicles is to improve the fuel economy and this will be discussed rather extensively in this report. The distribution of fuels and electricity will be briefly described, as will the costs, since the technology of hybrid vehicles is quite new and there is, so far, no clear information concerning costs. This also applies to testing methods for relevant hybrids, since no standardized methods have been determined. The effect of the emissions has not been thoroughly mapped out, but the trend seems to be decidedly positive. It must be mentioned that Peter Ahlvik, Ecotraffic, has supplied valuable contributions to the report and has also checked the report in its final stages, which is highly appreciated.

The authors of the report, Karl-Erik Egebäck, Autoemission K-E E Consultant AB, tel. +46 (0)155 28 24 44 and Sören Bucksch, Sören Bucksch AB, tel. +46 (0)8 580 33 330 would like to thank Liz Egebäck Foxbrook for the help with the translation from Swedish to English and the languish check. A thanks is directed also to KFB, who has financed this work.

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3 THE COMPLEXITY OF THE DEVELOPMENT OF FUELS

AND VEHICLES

During recent years there has been much activity in the development of both conventional vehicles, engines such as direct injected otto engines (GDI) and alternative vehicles such as electric vehicles, hybrid vehicles in which the electricity has been generated by fuel cells. Even concerning fuels much development has taken place. The conventional fuels, gasoline and diesel oil, are reformed in different ways. For example in the case of gasoline, in order to use more environmentally friendly components there has been a reduction in the content of benzene, an addition of an alcohol to the gasoline, a reduction in the vapor pressure etc. The improvements of diesel oil mean primary that the content of both sulfur and aromatics are reduced and that the cetane number is increased to the level of 48 to 50 or higher. Despite these changes of gasoline and diesel oil the fuels must of course still be of such quality that they can be used in existing vehicles on the market. The owners of the vehicles must as far as possible be kept indemnified and therefore it is important that no changes in the fuels are realized that will create a problem for the car owner.

The gasoline must have a sufficiently high octane number in order to not cause knocking in the engine. After the introduction of lead-free gasoline, during the second part of 1980s, there has been a requirement that a gasoline with a lubricating additive should be available for the older cars in order to protect the valves in their engines. On the other hand it has been of great importance that the “lead-free” gasoline should not contain lead of such amount that there is deterioration of the emission control system.

For the diesel oil it is important that its density is kept within specified limits so as not to have an undue influence on the engine power set by the engine manufacturer. It is also important that the diesel oil has such a lubricating quality that the wear of the engine and especially the fuel injection system does not increase.

The introduction of a new technology not only requires certain changes in society, for example a new infrastructure if a new alternative fuel is to be introduced, but it will also have an impact on the user of the new technology. This is true not least in the area of automotive vehicles and the reason may be that the ownership and use of a motor vehicle is costly both for the private person and society, but also because of the fact that new technologies are linked to feelings of uncertainty when they are introduced. If we keep to area of automobiles the experiences are that even small problems in the introduction of a new technology can change a positive attitude within the car owners to a negative attitude. Of course the cost of the new technology is an important factor in this case. The above discussion indicates that the complexity of even small and positive changes will have an effect on the car owner and use of his or her vehicle. The improvement of the environmentally related quality of the fuel or the introduction of renewable fuels will probably be accepted as something positive for most of us including the car owner. In the case of the introduction of lead-free gasoline, which was a success in Sweden without causing any great problems, it was important that there was a good degree of co-operation between the authorities and the oil and car industry.

Usually the car owner does not suffer if there are changes in the style or function of the car or if there are changes in the fuel composition unless there is an increase in the cost of purchasing the car and in running it. The latter may, however, be a problem for many car owners. Fortunately some changes can be advantageous even if they lead to higher costs for the car owner. One such advantage can be that a vehicle with high environmental qualities may be accepted for use in areas where the use of cars is restricted.

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There may be advantages with some types of vehicles despite their being “odd”, provided they function well and especially if they are more fuel efficient than other vehicles. The reduction in the cost of using these cars may balance the higher cost for the purchase of the car. However, it is not easy to find such cases though progress in this direction can be expected to occur in the long term. If the interest in hybrid vehicles remains as keen as it has been, they may be interesting objects for purchasers of new cars. However, success for hybrid vehicles depends in the end on whether the car manufacturers make an effort to develop such reliable, well performing and not too costly hybrid concepts as will be attractive for the purchasers. During a transitional period it seems necessary for governments or governmental authorities in the progressive countries to financially or by other means support at least some part of the development and introduction of the hybrid vehicles. Such support was given for example in Sweden at the end of the 1980’s, on the introduction of the present-day efficient emission control system for light duty vehicles. One problem concerning hybrid vehicles is that the costs of developing these vehicles and the batteries to be used in them will be on a much higher level than for the above mentioned emission control system.

The competition for customers and the increasing requirements concerning the emissions and fuel economy has led to the use of large resources among the car manufacturers and engine manufacturers in the search of new solutions for new types of engines and vehicles. Such trials may on the other hand lead to a shortness of resources, which require different priorities within the actual industry. For the car industry there may also be a dilemma that there are many alternatives to study in order to take the right decision and to maintain sound priorities. The shortness of resources and today’s focusing on fuel cells and the development of fuel cell vehicles may lead to a shortage in resources for the development of electric- and hybrid vehicles as compared to the case without this focusing on fuel cells. This focusing on fuel cells may also obstruct the development of alternative fuels for internal combustion engines since a successful development and introduction of alternative fuels is more closely related to a lower cost of these fuels, and especially biobased fuels, than it is to their having a potential for lowering the emissions of harmful substances. In the case of hybrid vehicles there is a possibility that the car manufacturers see these vehicles as transfer technology up to fuel cell vehicles, and that the only main change to be carried out is to use a stack of fuel cells instead of the internal combustion engine.

Returning to the subject of hybrid vehicles, there is a question as to whether renewable fuels will be one of the possible alternatives, especially as improvements of gasoline and diesel oils have resulted in a higher potential for these fuels to meet the requirements concerning health and environment, except in the case of the so-called greenhouse gases carbon dioxide, methane, nitrous oxide etc. However there do not seem to be any technical obstacles to the use of renewable fuels for hybrid vehicles and, as has already been underlined, there is an obvious advantage in the reduction of greenhouse gases when using renewable fuels and even, in some respects, in the form of a reduction in the emission of NOx and particles. The latter is true also

for other alternative fuels such as natural gas.

Since the development of hybrid vehicles is taking place in the car manufacturers’ plants all over the world, the description of the hybrid vehicles is based on information found in the international literature and obtained through communication with different persons working in the field of development of hybrid systems. One problem is that the information from the car manufacturers is restricted and it is difficult to obtain information about the status of the development. In the meantime, from the start of a report like this many new inventions have been presented by the car manufacturers but not officially published and some new prototypes or other types of hybrid vehicles have been presented on the market. Unfortunately some of this information, which may be important, has not been included in this report.

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So far most of the development of hybrid vehicles has occurred chiefly in Japan but even in the USA. So far there are only one or two prototypes of hybrid vehicles which have been presented by the European car manufacturers to the knowledge of the authors of this report. One of these is a Renault Kangoon and this vehicle will be available on the market year 2001. .

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4 HYBRID SYSTEMS

As has been described above the conception “hybrid”, related to motor vehicles, is a vehicle equipped with more than one energy transformer. By this definition it is not stated which type of energy transformers are used in the hybrid system. However, this does not mean that the number and types of energy transformers are unlimited when looking at practical, technical and economical possibilities. Fuel cells may, for example, be used in hybrid vehicles and such vehicles are already presented as prototypes, but are not today either so technically well developed or economically feasible as to be introduced on the market. The aim here is to describe the main alternatives of hybrid systems in greater detail, in order to provide information for those readers who are familiar with the hybrid technology for motor vehicles. It is usual today to have an internal combustion engine connected to an electric generator used as one of the (or the main) energy transformer system and a battery in combination with an electric motor as the other energy transformer system. The engine can most commonly be an otto engine or a diesel engine but other alternatives are possible such as sterling engines, gas turbines etc. The different types of engine are presented in Section 6.

There are many different types of battery available such as special lead (acid) batteries, a valve regulated lead accumulator (VRLA), nickel metal hydride batteries (NiMH), natrium (sodium)-nickel chlorine batteries (named ZEBRA), zinc air batteries, lithium-ion and lithium-polymer batteries respective and some others. The use of capacitors and especially ultra-capacitors constitutes an important possibility of storing electric energy. The ongoing development of batteries is discussed in Section 7.

The combination fuel cell and battery is a possible and attractive long-term alternative combination in hybrid vehicles. However, an even more attractive alternative would be a vehicle where the fuel cell is directly connected to the electric motor as the fuel cell can itself be regarded as a battery. The problem associated with such a system seems to be that electric energy is commonly not stored in a fuel cell system, such as the one mentioned, and therefore the fuel cells must rapidly convert the chemical energy in the fuel to electric energy, since the fuel cells has to produce a variably flow of electricity. The question is whether such a vehicle should be called a hybrid or an electric vehicle and one such vehicle is presented in Section 8.2.2. However, the energy efficiency of such a vehicle can exceed quite considerably that of a vehicle having both a fuel cell and a battery. The fuel cells are presented in Section 6.

As already described there are two main types of hybrid systems, classified as series hybrids and parallel hybrids. There seems also to exist systems which could be classified as being of a type somewhere between series hybrids and parallel hybrids. However, in this report we are concentrating our description to the two main systems.

4.1 Series hybrid systems

By definition one can classify a series hybrid as a vehicle where an internal combustion engine (or some other type energy transformer) is placed in series with an electric motor (or more than one electric motor) for the traction of the vehicle. This implies in practice that the main function of the internal combustion engine is to generate electricity for the battery which in turn feeds the traction motor (or electric motor) either directly or by the battery, via a generator. In this manner there is no direct mechanical connection between the internal combustion engine and the driving wheels.

Simply expressed one can also say that a series hybrid vehicle is basically powered by two sources. A common layout for a series hybrid system is shown in Figure 1.

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The internal combustion engines used in a series hybrid system are usually rather small (compared with conventional traction system) and rarely deliver more than 50 % of the maximum power needed for propelling the vehicle*. Since there is no direct mechanical connection between the engine and the driving wheels, the engine in the most extreme case can be run more or less at constant load and speed. The condition - that the engine does not have to follow a certain dynamic driving cycle – means that the chances of obtaining low emission levels are good if for example an otto engine with a three-way catalyst system is used in the series hybrid system.

Figure 1. Series hybrid system. (Source: DOE, USA).

In series hybrid vehicles an electric motor (or more than one motor) is used for the traction of the vehicle. Series hybrid systems are usually designed to be used in heavy-duty vehicles. In the case of buses where more than one electric motor is used these motors may be placed close to the driving wheels. One drawback of the series hybrid vehicle is that it has to be equipped with a rather powerful battery with a high energy density since all or at least 50% of the power may in extreme cases have to be delivered from the battery for the traction of the vehicle. The large batteries are heavy and add a considerable weight to the vehicle and are also considered to be costly.

4.2 Parallel hybrid systems

The traction equipment of the parallel hybrid type of system is powered by two energy transformers, which work parallel with each other. In this case the internal engine is mechanically connected to the driving wheels via a gearbox and the electric motor supports the engine when more power is needed than can be delivered by the engine. Commonly the engine is larger and more powerful than in the series hybrid system while the electric motor is smaller and consequently less powerful. The internal combustion engine has to follow the type of dynamic driving conditions of the vehicle because of the mechanical connection to the driving wheels and this will somewhat reduce the potential for low emission levels. However, the impact of heavy transients can be a little less if a certain leveling by “peak shaving” is used in the hybrid system. One advantage with the parallel hybrid system is that the battery used is smaller and consequently lighter and less costly compared with the battery for series hybrids.

A layout for a parallel hybrid system is shown in Figure 2.

*_{The most extreme variant of a series hybrid is an electric vehicle equipped with an auxiliary engine in order to}

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Figure 2. Parallel hybrid system. (Source: DOE, USA).

4.3 Further developed hybrid systems

Today the development of hybrid vehicles seems to be towards the use of series hybrid systems, especially in heavy-duty vehicles and primarily in buses, while parallel hybrid systems are being developed for light duty vehicles. As has been pointed out earlier, the control of the internal combustion engine of a series hybrid vehicle involves a less varied load cycle than that is used for the engine of a parallel hybrid vehicle. Due to the less varied load of the engine a higher efficiency is achieved for an engine used in a series hybrid vehicle than for an engine in a parallel hybrid vehicle. This is discussed in more detail in section 6 and 8. Naturally it would be an advantageous in terms of fuel economy if the internal combustion engine in a parallel hybrid vehicle could be run in an area of the load cycle where the efficiency if the engine is highest. Areas with low loads should be avoided especially for otto engines since the efficiency of this type of engines drastically drops as the specific fuel consumption increases at low loads of the engine, which can be seen in Figure 3. In the figure different lines are shown for cases where the efficiency of the electric drive system (generator, charging/ discharging of the battery and the converter) is 77 % and 60 % resp. and where the maximum efficiency of the engine is as high as 35 %.

In order to reduce the fuel consumption as far as possible the parallel hybrid system can, first of all, be designed according to the following characteristics:

The internal combustion engine is switch off at the limit of low power needed for the traction of the vehicle. The battery is then used as the only energy source.

The internal combustion engine switches off when the vehicle is stopped. The energy released during braking is fed back to the battery.

The size of the internal combustion engine is adjusted to a lower requirement of power, as necessary. For acceleration and some other driving conditions, when the power of the internal combustion engine not is sufficient there will be support from the electric motor. Matching of the internal combustion engine with regard to the most fuel economic driving

conditions by the use of a continuous variable transmission (CVT).

Figure 3 shows the specific fuel consumption for a minivan and a series hybrid vehicle (SHEV*) system equipped with an internal combustion engine with an efficiency of 35 % and

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a generator. The specific fuel consumption was measured when driving on an even horizontal road. The SHEV exceeded the gasoline-fueled vehicle without hybrid system in fuel economy, i.e. in used energy under the following provisions;

• when the efficiency of electric generation/charging/discharging of the battery is at least 60 %;

• when the speed of the vehicle is less than 50 km/h;

• when the efficiency of the electric generation/charging/discharging of the battery is at least 77%** and the speed of the vehicle is below 80 km/h.

The performance of the SHEV was significantly better, concerning the use of energy, when the vehicle speed was less than 20 km/h.

Iwai (Iwai, 1998) point out that a vehicle equipped with a parallel hybrid system (SPHV)*** has the best fuel economy i.e. energy efficiency at both low load and high load by driving the system as a SHEV at low load and as an internal combustion engine alternative at high load. According to Iwai it requires that the engine in a SHEV be propelled with high efficiency and an efficiency of at least 77 % and 60 % respectively for the electric drive system, for the SHEV to be able to surpass a gasoline fueled vehicle without hybrid system in the question of efficiency.

Figure 3. Specific energy used in a gasoline fuelled car and a series hybrid when driven on road (Iwai, 1998).

The car manufacturers, for example Ford and Toyota, use the possibilities described by Iwai for the control of their hybrid systems. To be more specific, Ford uses them partly and Toyota uses them nearly full out. There are naturally further technical possibilities for improving the energy efficiency in the hybrid systems. Different hybrid vehicles are presented in Chapter 8. The above described study of the possibilities for further development and the two mentioned hybrid electric vehicles Toyota and Ford have shown that there is a potential for further improvements of hybrid systems.

**_{Iwai has then calculated that the efficiency of the generation of electricity of 90 %, 95 % for the rectifier.} ***_{Series-Parallel-Hybrid-Vehicle.}

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5 FUELS

When developing the internal combustion engine for a hybrid vehicle the choice of fuel is an important question, because this is decisive for the type of engine to be used. The choice of fuel is also decisive for the efficiency of the engine as an energy transformer and its performance concerning the emissions of exhaust gases and noise. The question is then whether the hybrid vehicle should be optimized for high efficiency or low emission performance. This is decided, among other things, by the choice of fuel and the type of internal combustion engine to be used, but also by other components in the hybrid system and the interaction between these as directed by a control system. The authors of this report do not take any position concerning the choice of strategy regarding the best efficiency and the best emission performance by the hybrid system but have given some views about the role of fuel and engines in the coming sections. Hopefully the selection of the “right” fuel may contribute to achieving the goal of both an excellent efficiency and a good emission performance.

The fuels which are actual for hybrid vehicles are the conventional fuels, gasoline and diesel oil, and those which are called alternative fuels. Of the latter the following may be used: Fossil fuels/fossil-based fuels (also called alternative fuels) such as natural gas (for example

CNG or LNG), liquefied petroleum gas (LPG), dimethyl-ether (DME) synthetic gasoline and diesel oil and methanol based on natural gas.

Bio-based fuels such as alcohols (ethanol and methanol), bio-gas and fatty oil esters (commonly called FAME).

Hydrogen.

It is technically possible to use different fuels, and therefore it is firstly a question as to whether a sufficient amount of fuel can be supplied, whether the fuel can be efficiently distributed and if the fuel is reasonable priced. However, the critical question is whether there is sufficient interest in investing in an alternative fuel. Which fuel will be elected to be used for fuel cells in the long run is, so far, an open question even if it from the point of energy should turn out that a gaseous fuel would be more efficient than methanol, which is a popular fuel for one of the popular fuel cells (PEM), see section 6.4. For hybrid vehicles gasoline or diesel oil commonly is used but for heavier vehicles, such as buses, gaseous fuels or an alcohol is used in some cases instead of diesel oil, see section 8.

Fuels produced from either fossil-based material or bio-based materials are called flexible fuels in this report. In order to show one advantages of such a fuel, methanol can be taken as an example. In order to reduce the emission of the greenhouse gas CO2, it can be argued that

methanol can be used in the long run, since it can be produced from natural gas to start with and later on from a bio-based material if an efficient and reliable method has been developed. However, there are various disadvantages of this, amongst others the risk that the introduction of bio-based methanol will be delayed many years if the cost of this fuel is regarded as being too high.

In the following the discussion will be concentrated on gasoline, diesel oil, LPG, natural gas, bio-gas, ethanol, methanol, DME and two other synthetic fuels. Hydrogen will be mentioned as one alternative and then as a fuel for fuel cells but also as an energy carrier for other purposes. It can be of interest to mention that the government of Island has signed an agreement with the DaimlerChrysler-Ballard group, which may result in the production of hydrogen in Island, if the agreement is realized.

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5.1 Fossil fuels

As has already been pointed out, there are many fuels within the fossil fuel group. However, in this context, it is of interest to primarily discuss gasoline and diesel oil, since these two fuels are commercially available in different countries all over the world. It seems also that they will be the primary fuels on the market for the transport sector, for a long time in the future. Natural gas and methanol based on natural gas are alternatives on an international market and they are therefore clearly objects of interest in this discussion.

The development of automotive fuels in Sweden and even internationally has resulted in the present day situation where it is difficult to clearly define the over-all availability of the different gasoline blends and the different types of diesel oil. As a consequent, the specifications of these fuels changes from time to time since the increasingly severe emission standards not only affect the development of new vehicles but also of better fuels. In addition the specifications allow that the composition of fuels may show a variation not only from one country or group of countries to another group of countries – for example between the USA and Europe – but of course also between different classes of gasoline and diesel oil. In Sweden for example there is so far no requirement that all gasoline must contain a certain percentage of oxygenates, but on the other hand it not been explicitly declared that it is forbidden to blend gasoline with a certain amount of an alcohol or for instance MTBE or some other ether.

Concerning MTBE the use of this oxygenate in gasoline is forbidden in California since there are evidence that the groundwater has been contaminated with MTBE in certain areas. Also in the federal USA a discussion has started as to whether MTBE should be fazed out from gasoline or whether the use of MTBE should be limited. These actions can result in the use of other ethers being questioned in the USA and California. It can be added that no similar actions have been taken in Europe on the EU level but a discussion has started which may also influence the use of MTBE in Sweden. However, to sum up the results of the development of gasoline and diesel oil, it is clear that both of these fuels have been improved during the last decade both in the USA and Europe and further improvements will be seen.

5.1.1 Standardization of gasoline, diesel oil and some other fuels

Neither gasoline nor diesel oil is a uniform mixture. Gasoline is produced by blending different hydrocarbons in order to meet the required specification primarily arrived at in co-operation between the car manufacturers and the oil industry. In Sweden this co-co-operation is organized by the Standards Institute (SIS-STG), which is also administratively responsible for the work, for the organization of meetings, for setting up the protocols and to printing and publishing the agreed standards. Authorities in Sweden such as the Environmental Protection Agency propose requirement for certain components in the fuel, especially if the fuel is going to be environmentally classified. In this case representatives for the agency or fuel experts usually participate in the work of preparation of standards.

For a long time an extensive co-operation for international standardization of fuels for automobiles has been in existence. In Europe this work is organized within an organization called CEN (European Committee for Standardization). Experience has shown that there is an advantage in a co-operation within CEN, even if the requirements concerning some of the components or parameters in the fuel can differ from country to country. In areas with variable climatic conditions, such as the south of Europe and the Nordic countries, it is natural that the requirements for the automotive fuel differ. The connection between the composition of the fuel and health effects is briefly discussed in section 14.

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5.1.2 Gasoline

In Sweden gasoline is classified environmentally. Some years ago there was no highest class MK1, i.e. a gasoline specified so as to have the best environmental quality, but today such gasoline exists on the Swedish market. The different classified parameters can be seen in the following summary, see Table 1.

Gasoline has since long been regarded as a cleaner fuel than diesel oil. This judgment is certainly linked to the exhaust emissions from diesel-fueled vehicles. These have been seen as more dangerous from the health point of view than the exhaust emissions from gasoline fueled vehicles. The diesel vehicle exhaust has been shown to contain a greater mass of polycyclic aromatic hydrocarbons (PAH) than the gasoline vehicles. The greater mass of PAH is also linked to a higher mutagenic activity caused by the diesel vehicle exhaust when compared with gasoline vehicle exhaust. The diesel vehicle exhaust also contains a larger mass of particles which leads to a higher health risk when compared with gasoline vehicle exhaust. To this should be added that the smell of diesel vehicle exhaust is experienced as more unpleasant than the exhaust from gasoline fuelled vehicles.

It is likely that many of these results and experiences can be referred to the difference in combustion process between the spark ignition engine (otto engine) and the compression ignition engine (diesel engine). On the other hand there are, or at least were, emissions which could be linked to components in the fuel. Not many years ago there were compounds with lead in gasoline in Sweden and additives are still used in gasoline in many other countries. It can also been underlined that gasoline contains benzene and other harmful hydrocarbons of which benzene is regarded as a carcinogen. Therefore it is wise to handle gasoline as a poison and also to be careful so as not to let gasoline touch the skin or to breathe gasoline vapor. Table 1. Environmentally classified parameters and components in gasoline in Sweden

(MK1).

Parameter Unit MK 1 ”temporary blend of gasoline” 1998 - 2000

MK 1 from year 2000 (the date when EU spec. 2000 was implemented)

Benzene Max. vol.-% 2.0 1.0

Aromatic index Max. 5.5

-Aromatic content Max. vol.-% - 42

Sulfur Max ppm (mass.) 100 50

Olefins Max. vol.-% 15 13

Evaporated at150 °C1 _{Min. vol-%} _75.0 _75.0

Additives Not ash forming Not ash forming

Source: STATOIL, Sweden.

The organic lead components belong to a group of additives which are regarded as the most poisonous components in gasoline. The existence of these organic lead pollutants in the environment was the main reason in Sweden for reducing lead additives in gasoline from 0.80 to 0.85 g/liter before 1970 to 0.70 from 1970, 0.40 from 1973, 0.15 g/liter 1980/81. “Green” (i.e. unleaded) regular gasoline was introduced year 1986 and 1995 the use of lead in gasoline was forbidden. Similar actions has been taken also in many other countries around the world. Later on the lead was faced out completely in the so called lead-free gasoline because lead was proven to be a poison for catalysts. Up to around the middle of the 1990’s there were one

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or two blends of “green” gasoline in Sweden containing approximately 0.07 g/liter of lead additives. After that time another additive not containing lead (as used of lead was forbidden) has been used (see the second paragraph after this).

Concerning the lead-free gasoline it can be of interest to know that even this gasoline may contain small amount of lead as long as leaded gasoline is distributed, due to the a risk for contamination during distribution of the fuel. The distribution lines for unleaded gasoline may not have been completely separated from those used for leaded gasoline. Therefore the concept “lead-free” is not relevant - a more adequate concept should be “unleaded gasoline”. Commonly the requirement for the non-leaded gasoline was that it should not contain more than 0.013 g lead per liter gasoline. Since no leaded gasoline exists in Sweden the blend of unleaded gasoline of today may be completely lead-free.

There were two reasons for using lead-additives in gasoline of which one was that the octane number was increased and the second was that the valves in the engine were lubricated by lead. When the oil companies in Sweden decided to not use lead-additives in gasoline this additive was replaced with other additives – containing sodium or potassium - of which potassium was preferred since sodium gave high-temperature corrosion in the engine’s turbo aggregate. The opinion in the oil industry is that most of the cars in Sweden do not need any special lubrication for the valves and therefore they have decided to stop the blending of lubricating additive in gasoline. The replacement this time will be bottles containing a potassium additive, available at gas stations, which the owners of old cars can use when filling up gasoline.

As already mentioned gasolineconsists of a mixture of different hydrocarbons as can be seen in Table 1. One of the requirements for a good function of gasoline is that the motor octane number and the research octane number are high. For the Swedish unleaded (green) gasoline the research octane number has to be at least 95. For some years the oil companies in Sweden have provided the market with a premium gasoline with a research octane number of 98. Since the use of octane-increasing lead-components in the gasoline for catalyst cars introduced at the end of the 1980s was not allowed, oil companies had to use high octane components, such as isomerized hydrocarbons, at a higher rate than earlier. Aromatic hydrocarbons such as benzene and others also have a high octane number. The content of these hydrocarbons tended to increase and especially when 98 octane unleaded gasoline was introduced. This was also a consequence of a higher rate of the cracking of larger and heavier hydrocarbon molecules in order to have access to lighter hydrocarbon components for the production of gasoline. As can be seen in Table 1 the content of benzene is limited to 1% by volume according to EU specifications for gasoline which is an advantage.

Since a high content of aromatics in gasoline is not desirable, when striving towards a blend of environmentally friendly automotive fuels, the content of aromatics and especially benzene (in gasoline) should be kept as low as possible. However, it is obvious that there is a correlation between certain hydrocarbons and the physical performance of the fuel such as between aromatics and the octane number of gasoline. Therefore other hydrocarbons, which do not expected to give negative health effects, should be used even if alternative production methods have to be used. In the case of aromatics the technology for production of other hydrocarbons such as alkylates is available but certainly more expensive and alkylates do not increase the octane number as aromatics do. According to information (Lindberg, 2000) the content of aromatics in the EU gasoline have to be reduced to 35% from year 2005.

In Table 1 the difference can be seen between MK1 as “the transition quality” and gasoline according to the EU specification (the present day MK1 gasoline in Sweden) which has a maximum content of 42 % by volume (a rather high value). As noted above, benzene is a

Hybrid Electric Vehicles

Hybrid Electric Vehicles

An alternative for the Swedish market?

Karl-Erik Egebäck

Sören Bucksch

SUMMARY

See page 8

Hybrid Electric Vehicles

An alternative for the Swedish market?

Karl-Erik Egebäck

Sören Bucksch

CONTENTS

TABLES

FIGURES

1 SUMMARY

2 INTRODUCTION

3 THE COMPLEXITY OF THE DEVELOPMENT OF FUELS

AND VEHICLES

4 HYBRID SYSTEMS

4.1

Series hybrid systems

4.2 Parallel hybrid systems

4.3

Further developed hybrid systems

5 FUELS

5.1

Fossil fuels