This book covers the development of electric cars, from their early days, to new hybrid models in production. Most of the coverage is focused on the very latest technological issues faced by automotive engineers working on electric cars, as well as the key business factors vital for the successful transfer of electric cars into the mass market.
Inspec keywords: battery chargers; hybrid electric vehicles; fuel cell vehicles
Other keywords: vehicle numbers; battery development; automotive engineers; electric car; substantial improvements; hybrid cars; electric vehicle; fuel-cell cars
Subjects: Power convertors and power supplies to apparatus; Fuel cells; Transportation
This book has been written to provide a comprehensive picture of the history, current status and the likely future development of electric cars, as it is seen at the beginning of the second millennium. I have chosen to write about electric cars rather than electric trucks and buses as it seems to me that the success of electric cars in the market place will be the clearest signal of the technology reaching maturity. The category of cars includes such vehicles as taxis and light delivery vehicles but not trucks and buses. The book is intended both for those working on all aspects of electric vehicle development and use, as well as for those members of the general public who have an interest in the technology and the future of personal transportation. It should also be of interest to those concerned by the pollution currently caused by the internal combustion engine and who see the electric car as one of the ways by which this pollution can be reduced.
The history of electric cars is the story of how the development of practical methods of storing electrical energy combined with the invention of methods of converting electrical to mechanical energy provided the possibility of a new, quiet and clean method of propulsion. This history also describes how that method of propulsion experienced a brief period of ascendancy at the beginning of the twentieth century, before being over taken by the internal combustion engine. The reasons for the reappearance of electric cars in the last two decades of the twentieth century are also discussed and give a lead into the subject matter in the remainder of this book.
This chapter describes the way these different categories of motor operate and their advantages and disadvantages when used in electric vehicles. The switched reluctance motor, the brushless DC motor and the disc motor are also described and their possible application in future electric vehicles considered.
If an electric vehicle is to operate efficiently and effectively it is essential that the total vehicle system is optimised at all times to ensure that the energy available is used as effectively as possible. The amount of energy available is normally much less than that in a gasoline-powered vehicle, but the performance needs to be comparable if the electric vehicle is to operate on the road system at the same time as conventional vehicles.
This chapter has covered all the battery types at present being seriously considered for use in electric and hybrid vehicles. The dramatic improvements in performance demonstrated through the coordinated work of ALABC on valve-regulated lead-acid (VRLA) batteries has made the lead-acid battery once again a contender in the battle to become the battery of choice for the electric vehicle. Its role as a low-cost, well-understood, immediately available power source capable of being fast charged when required, must make it a strong candidate for the low-cost electric and hybrid cars likely to attract the public in the short term. Also in the short term nickel-metal hydride seems likely to take over the role of nickel-cadmium as the higher-power, higher-cost option, with its advantages in longer life and safer disposal. The high-temperature batteries offer significant performance improvement if the vehicle manufacturer is prepared to design systems capable of maintaining battery temperature under the wide range of conditions under which a car can be operated. Of the high-temperature batteries available sodium-nickel chloride seems to have advantages in having a slightly lower operating temperature, better freezing characteristics and failure to a short circuit condition, so making chains of cells and batteries practical. In the longer term the metal-air batteries offer considerable improve ments in performance, but the special requirements of replacing the metal electrodes and/or circulating the electrolyte need to be shown to be fully practical in the vehicle situation. The most exciting developments are likely to be in lithium-solid polymer and lithium-ion batteries with their high-energy density, potential for low cost and flexibility of installation, but volume production still seems to be some years away.
Of the non-battery methods of providing power for an electric car, only fuel-cell generation and flywheel storage provide sufficient power to operate an electric car over a commercially useful range. Recent developments in fuel-cells make them a more likely power source for the shorter term than flywheels. The proposals for fuel-cells which can run directly on methanol or gasoline, rather than as at present having to use reformers to convert these fuels to hydrogen, make fuel-cells a potentially more attractive short-term proposition than hitherto. If this development is successful we could see significant numbers of electric vehicles using this technology within ten years. The successful development of an infrastructure for supplying clean hydrogen direct to vehicles could, however, change the emphasis to the use of hydrogen storage on the vehicle. These issues are discussed. Flywheels still have a large safety hurdle to overcome. Before they can be accepted in production vehicles it will have to be shown conclusively that the flywheel containment system can cope with all the accidental failure mechanisms which can occur in a vehicle in use on the public roads, and that the gyroscopic effects both in normal use and in a catastrophic failure do not increase the danger to the user. The other energy sources described in this chapter cannot, with perhaps the exception of compressed air storage, store sufficient energy to propel a vehicle over a distance great enough to be of interest. However, because of their generally high power density, they can be very useful when hybridised with other energy storage methods such as chemical batteries, which have a high-energy density but low power density (for example metal-air batteries); or with other primary power sources such as internal combustion engines. The use of these technologies in hybrid vehicles is discussed in more detail.
The charging and recharging of electric vehicle batteries is a critical part of the energy cycle in an electric vehicle. Although less attention is usually paid to charging than to the vehicle batteries and the electric motors that they drive, the availability of efficient, and where appropriate fast, recharging of batteries is a vital factor in deciding whether a particular electric vehicle is of practical use for regular transportation.
So far in this book we have described the various subsystems which go to make up an electric vehicle but, with the exception of the hybrid electric vehicle, have not considered how all these systems come together to make a complete vehicle. This approach was necessary to enable the reader to understand the functions of the various subsystems sufficiently well to appreciate the limitations they impose on overall vehicle design.
In this chapter the author have brought together all the information available on the current (2001) production, prototype and experimental battery electric cars developed by the major manufacturers together with more detailed descriptions of four of the production vehicles which the author consider to be of major significance. This information is given. The technical details given have been provided directly by the manufacturers except in a few cases where information has been obtained from published papers and press reports. Specialist niche manufacturers of electric vehicles such as Bombardier and Solectria are not included, as it is my view that it is essential for the major automotive manufacturers to commit to electric vehicles for them to succeed. It is therefore the developments introduced by the major manufacturers that we should concentrate on if we are to understand where electric car development is heading.
Any vehicle that has more than one power source can be classified as a hybrid electric vehicle (HEV), but most frequently the term is used for a vehicle which combines electric drive with a heat engine using a fossil-fuel energy source. This chapter provide a discussion on the hybrid system configuration, all-electric hybrid vehicles, electrochemical hybrid vehicles, heat engine-electric hybrid vehicles, the concepts of HEV, production of hybrid cars, and prototype and experimental hybrid cars.
In this chapter we will consider how the hydrogen essential for the operation of a PEM fuel-cell can be provided in the car, how it can be stored, and what the implications for the fuel infrastructure will be. All the information currently available on the prototype and experimental fuel-cell cars being developed by the major automotive manufacturers is also given in Table 11.1.
If the electric vehicle and particularly the electric car is ever to compete effectively with conventional internal combustion-engined vehicles, the price at which it can be profitably built and sold to the public must be similar to that for a conventional vehicle having a similar feature level. A small premium may be acceptable for the electric vehicle providing it offers a significant reduction in emissions and in the case of fuel-cell and hybrid electric vehicles, a significant reduction in fossil-fuel consumption.
In this book I have tried to describe the current state of electric vehicle technology at the beginning of the year 2001. It seems clear to me that before the first 20 years of this century are over, increasing pressure on the environment will result in increasingly severe regulation of emissions from vehicles in urban areas. This, together with the rocketing cost of hydrocarbon fuels, will ensure that personal transport needs will have to be met by a mixture of highly economical, relatively low-performance gasoline or diesel-fuelled cars and by a range of electric cars of various types.