Performance Simulation of the GM EV1

In Section 7.3.3 we gave the MATLAB script file for simulating the acceleration from a standing start of an electric scooter. In Section 7.3.4 we turned our attention to the groundbreaking GM EV1, and developed some equations for its performance. The script file for modelling the acceleration of that vehicle is quite similar to that for the scooter, and is given below. Simulates the WOT test of the GM EV1 electric car. t linspace(0,15,151) 0 to 15 seconds, in 0.1 sec. steps v zeros(1,151) 151...

Importing and Creating Driving Cycles

An important part of range modelling is the use of standard driving cycles, as explained in Section 7.4.1. When using MATLAB these driving cycles must be set up as one-dimensional arrays which contain successive values of velocity. There are many ways of doing this, including methods involving directly reading files. However, the easiest way to do the task is to simply set up a matrix by cutting and pasting in the data as text into a file, as follows. Let us imagine a very simple driving cycle...

28 Battery Charging

The issue of charging batteries is of the utmost importance for maintaining batteries in good order and preventing premature failure. We have already seen, for example, how leaving a lead acid battery in a low state of charge can cause permanent damage through the process of sulphation. However, charging them improperly can also very easily damage batteries. Charging a modern vehicle battery is not a simple matter of providing a constant voltage or current through the battery, but requires very...

29 The Designers Choice of Battery

At first glance the designer's choice of battery may seem a rather overwhelming decision. In practice it is not that complicated, although choosing the correct size of battery may be. Firstly the designer needs to decide whether he she is designing a vehicle which will use batteries that are currently available either commercially, or by arrangement with battery manufacturers for prototype use. Alternatively the designer may be designing a futuristic vehicle for a client or as an exercise,...

75 Simulations a Summary

We have seen in this chapter how to begin the simulation or modelling of the range and performance of electric vehicles. With most vehicles the simulation of performance, by which we usually mean acceleration, is fairly straightforward. Mathematical software such as MATLAB or EXCEL lend themselves very well to this. In the case of the classical battery powered electric vehicle, and fuel cell vehicles using stored hydrogen, the modelling of range, though considerably more complex, is not...

210 Use of Batteries in Hybrid Vehicles

There are many combinations of batteries, engines and mechanical flywheels which allow optimisation of electric vehicles. The best known is the combination of IC engine and rechargeable battery, but more than one type of battery can be used in combination, and the use of batteries and flywheels can have advantages. 2.10.2 Internal combustion battery electric hybrids Where IC engine efficiency is to be optimised by charging and supplying energy from the battery, clearly a battery which can be...

Contents

1.1 A Brief 1.1.1 Early days 1.1.2 The relative decline of electric vehicles after 1910 3 1.1.3 Uses for which battery electric vehicles have remained popular 5 1.2 Developments Towards the End of the 20th Century 5 1.3 Types of Electric Vehicle in Use Today 1.3.1 Battery electric 1.3.2 The IC engine electric hybrid 1.3.3 Fuelled electric 1.3.4 Electric vehicles using supply 1.3.5 Solar powered 1.3.6 Electric vehicles which use flywheels or super capacitors 18 1.4 Electric Vehicles for the 2.2...

93 Design of the Controls

Traditional mechanical controls can be used in a traditional way, i.e. steering wheel, and floor mounted accelerator and brake (there is no need for a clutch with an electric vehicle). However some modern vehicles, such as the GM Hy-wire (shown in Figure 8.16) use more sophisticated modern systems using 'drive by wire'. This is a system which has come from the aircraft industry where it is know as 'fly by wire'. In this system the controls are effectively movement transducers that convert...

103 Vehicles Pollution a Quantitative Analysis

Energy for electric vehicles clearly has to come from somewhere. If battery electric vehicles are widely introduced the vast majority will have to be charged from the mains grid, where at present most electricity production comes from burning fossil fuels. At present sustainable sources of energy currently provide less than 10 of the energy used in the grid, so most of the electricity used for charging electric vehicles would be obtained from burning fossil fuels, including coal, gas and oil,...

43 Fuel Cell Thermodynamics an Introduction

4.3.1 Fuel cell efficiency and efficiency limits One of the attractions of fuel cells is that they are not heat engines. Their thermodynamics are different, and in particular their efficiency is potentially greater as they are not limited by the well-known Carnot limit that impinges on IC and other types of fuel burning engines. However, as we shall see, they do have their own limitations, and while fuel cells are often more efficient than IC engines, the difference is sometimes exaggerated....

42 Hydrogen Fuel Cells Basic Principles

We have seen that the basic principle of the fuel cell is the release of energy following a chemical reaction between hydrogen and oxygen. The key difference between this and simply burning the gas is that the energy is released as an electric current, rather that heat. How is this electric current produced To understand this we need to consider the separate reactions taking place at each electrode. These important details vary for different types of fuel cell, but if we start with a cell based...

112Rechargeable Battery Vehicles

Rechargeable battery vehicles can also be divided into several different categories. For example, there are electric bicycles, secondly there are the low speed vehicles (LSVs) which form a class of vehicle in the USA and Canada, with maximum speeds of 40 kph (25 mph), and thirdly conventional road vehicles using rechargeable batteries. In addition there are special purpose delivery vehicles and vehicles such as fork lift trucks. There are also the small four-wheeled carriages used by the infirm...

84 Transmission Efficiency

All vehicles need a transmission that connects the output of the motor to the wheels. In the case of an internal combustion engine vehicle the engine is connected to a clutch which in turn connects to a gear box, a prop shaft, a differential (for equalising the torque on the driving wheels) and an axle. All of these have inefficiencies that cause a loss of power and energy. The transmission of electric vehicles is inherently simpler than that of IC engine vehicles. To start with no clutch is...

Symbols

Letters are used to stand for variables, such as mass, and also as chemical symbols in chemical equations. The distinction is usually clear from the context, but for even greater clarity italics are use for variables, and ordinary text for chemical symbols, so H stands for enthalpy, whereas H stands for hydrogen. In cases where a letter can stand for two or more variables, the context always makes it clear which is intended. Amphour capacity of a battery OR capacitance of a capacitor Amphour...

22 Battery Parameters

All electric cells have nominal voltages which gives the approximate voltage when the cell is delivering electrical power. The cells can be connected in series to give the overall voltage required. Traction batteries for electric vehicles are usually specified as 6 V or 12 V, and these units are in turn connected in series to produce the voltage required. This voltage will, in practice, change. When a current is given out, the voltage will fall when the battery is being charged, the voltage...

82 Aerodynamic Considerations

It is well known that the more aerodynamic is a vehicle, the lower is its energy consumption. Bearing in mind the high cost of onboard electric energy, the aerodynamics of electric vehicles is particularly important, especially at high speeds. Let us first consider the effect of aerodynamic drag. As seen in Chapter 7, the drag force Fad on a vehicle is and the power Padw (Watts) at the vehicle wheels required to overcome this air resistance is Padw Fadw X V pACdV3 (8.2) where p is density of...

87 General Issues in Design

Before anyone sits down to design anything, including an electric vehicle they should write a design specification outlining precisely what they want to achieve. There are books devoted to the subject of writing specifications but it is worth briefly looking at the implications. For example, is the vehicle required for high speed motorway driving, or is it simply for delivering people or loads about town at low speeds This fact alone will lead to great differences in the shape of the vehicle....

36 Supply Rails

Electrical supply rails date from the 19th century and are an old and well tested method of supplying electric vehicles. Originally they were used on railed vehicles and later on trolley buses. The advantage of supply rails is that an electrical vehicle can be used without the need for an onboard battery. This enables clean, non-polluting vehicles to be used that can have an almost infinite range. This is ideal for underground trains for example. Originally the London underground used steam...

92Heating and Cooling Systems

There is little point in producing the ultimate energy-efficient electric vehicle, light, aerodynamic and with high motor and transmission efficiencies, and then waste precious energy by passing current directly through a resistance to heat the vehicle. With IC engine vehicles, copious waste heat will quickly warm the vehicle, although starting off on a cold morning may be unpleasant. For fuel cell vehicles or hybrids with internal combustion engines waste heat is also available, but with...

27 Metal Air Batteries

The metal air batteries represent an entirely different development, in the sense that the batteries cannot be recharged simply by reversing the current. Instead the spent metal electrodes must be replaced by new ones. The metal electrodes can thus be considered as a kind of fuel. The spent fuel is then sent to a reprocessing plant where it will be turned into new 'fuel'. The battery electrolyte will also normally need to be replaced. This is not a dissimilar concept to conventional IC engine...

86 Electric Vehicle Chassis and Body Design

Figure Eight Chassis

This section is intended to give guidance on the design of chassis for electric vehicles. Chassis design should be carried out in conjunction with other texts on chassis design, not to mention computer packages that specialise in this area. Nevertheless a basic understanding of what the chassis should do and other parameters related to electric vehicle chassis is needed. In the early cars chassis and bodies were separate items. The chassis gave the basic strength of the vehicle while the body...

61 The Brushed DC Electric Motor

6.1.1 Operation of the basic DC motor Electric vehicles use what can seem a bewildering range of different types of electric motor. However, the simplest form of electric motor, at least to understand, is the 'brushed' DC motor. This type of motor is very widely used in applications such as portable tools, toys, electrically operated windows in cars, and small domestic appliances such as hair dryers, even if they are AC mains powered.1 However, they are also still used as traction motors,...

64 Motor Cooling Efficiency Size and Mass

It is clear that the motor chosen for any application should be as efficient as possible. How can we predict what the efficiency of a motor might be It might be supposed that the type of motor chosen would be a major factor, but in fact it is not. Other factors are much more influential than whether the motor is BLDC, SR or induction. An electric motor is, in energy terms, fairly simple. Electrical power is the input, and mechanical work is the desired output, with some of the energy being...

102Vehicle Pollution the Effects

Before we look at solving environmental problems it is worth pausing to look at precisely what environmental problems are caused by vehicles. Electric Vehicle Technology Explained James Larminie and John Lowry 2003 John Wiley & Sons, Ltd ISBN 0-470-85163-5 There are two main problems caused by conventional vehicles. Firstly they ruin the immediate environment with noise and pollutants. Secondly they burn irreplaceable fossil fuels producing carbon dioxide which is a major cause of global...

34 Flywheels

Flywheels are devices that are used for storing energy. A plane disc spinning about its axis would be an example of a simple flywheel. The kinetic energy of the spinning disc is released when the flywheel slows down. The energy can be captured by connecting an electrical generator directly to the disc as shown in Figure 3.2, power electronics being required to match the generator output to a form where it can drive the vehicle motors. The flywheel can be re-accelerated, acting as a regenerative...

References

Bolognesi P., Conte F.V., Lo Bianco G. and Pasquali M. (2001) Hy-Sim a modular simulator for hybrid-electric vehicles. Proceedings of the 18th International Electric Vehicle Symposium, (CD-ROM). Chan C.C. and Chau K.T. (2001) Modern Electric Vehicle Technology, Oxford University Press, Oxford. Larminie J. and Dicks A. (2003) Fuel Cell Systems Explained, 2nd Edn, Wiley, Chichester. Shnayerson M. (1996) The Car that Could, Random House, New York. Wipke K., Cuddy M., Bharathan D., Burch S.,...

65 Electrical Machines for Hybrid Vehicles

The motors and alternators used in hybrid electric vehicles are in principle no different from those described above. Indeed in many cases there is no significant difference between the motors used in hybrid vehicles than any other type. The basic principles of some types of hybrid vehicle were described in Chapter 1. In the series hybrid vehicle there is really nothing different about the electrical machines from those used in a host of other applications. The traction motor, for example, will...

73 Modelling Vehicle Acceleration

7.3.1 Acceleration performance parameters The acceleration of a car or motorcycle is a key performance indicator, though there is no standard measure used. Typically the time to accelerate from standstill to 60 mph, or 30 or 50kph will be given. The nearest to such a standard for electric vehicles are the 0-30 kph and 0-50kph times, though these times are not given for all vehicles. Such acceleration figures are found from simulation or testing of real vehicles. For IC engined vehicles this is...

23 Lead Acid Batteries

The best known and most widely used battery for electric vehicles is the lead acid battery. Lead acid batteries are widely used in IC engine vehicles and as such are well known. However for electric vehicles, more robust lead acid batteries that withstand deep cycling and use a gel rather than a liquid electrolyte are used. These batteries are more expensive to produce. In the lead acid cells the negative plates have a spongy lead as their active material, whilst the positive plates have an...

74 Modelling Electric Vehicle Range

Quando Ocorrr Ebulicao Agua

It is well known that the range of electric vehicles is a major problem. In the main this is because it is so hard to efficiently store electrical energy. In any case, this problem is certainly a critical issue in the design of any electric vehicle. There are two types of calculation or test that can be performed with regard to the range of a vehicle. The first, and much the simplest, is the constant velocity test. Of course no vehicle is really driven at constant velocity, especially not on...

Motor Efficiency Plots

In Chapter 6 the question of efficiency plots of electric motors was addressed. An example was given in Figure 6.7. It is very useful to be able to print this sort of diagram, to see the operating range of electric motors, and where they operate most efficiently. Furthermore, this can be done very effectively and quickly with MATLAB . The script file is given below. A program for plotting efficiency contours for electric motors. The x axis corresponds to motor speed w , x linspace 1,18 0 speed,...

211 Battery Modelling

2.11.1 The purpose of battery modelling Modelling or simulating of engineering systems is always important and useful. It is done for different reasons. Sometimes models are constructed to understand the effect of changing the way something is made. For example, we could construct a battery model that would allow us to predict the effect of changing the thickness of the lead oxide layer of the negative electrodes of a sealed lead acid battery. Such models make extensive use of fundamental...

13 Types of Electric Vehicle in Use Today

Developments of ideas from the 19th and 20th centuries are now utilised to produce a new range of electric vehicles that are starting to make an impact. There are effectively six basic types of electric vehicle, which may be classed as follows. Firstly there is the traditional battery electric vehicle, which is the type that usually springs to mind when people think of electric vehicles. However, the second type, the hybrid electric vehicle, which combines a battery and an IC engine, is very...