"CSIRO TO POWER AUSTRALIA’S "ECOCAR"
CSIRO is to partner the Australian automotive industry in a plan to build an Australian hybrid-electric car for the 21st century.
The revolutionary car is intended to halve motorists’ fuel bills, slash city air pollution, boost exports of Australian car technology and put local industry at the leading edge of the world trend to "green" vehicles.
Building on the success of the aXcessAustralia car unveiled in 1998 to showcase Australia’s will have twice the fuel efficiency and emit a tenth of the pollution of a normal vehicle," says Mr David Lamb, director of CSIRO’s Australian Automotive Technology Centre (AATC).
CSIRO is currently working on two hybrid cars – one in partnership with a leading car corporation and the other with a consortium of more than 80 Australian car component firms.
"Apart from being essential to make our cities cleaner and healthier, the "EcoCar" is intended to prove to the world that Australian industry is competitive when it comes to the next major step in automotive technology.
"As well as its unique power system, the car will be packed with Australian innovations, " Mr Lamb promises.
These will include several CSIRO technologies, including:
- the hybrid petrol-electric power train
- a surge power unit (or supercapacitor) providing extra boost to the electric motor to enable the car to accelerate swiftly
- a sophisticated computerised energy management system for optimum efficiency
- new electric traction motors using switched-reluctance technology
- novel lead acid battery technology.
"Our primary aim is to prove to the Australian motoring public that a hybrid power train can deliver the same performance you’d expect of a conventional petrol engine – using far less fuel, costing less to run and with a spectacular reduction in emissions."
Mr Lamb says it is important for Australia to develop its own hybrid vehicle, in order to maintain local jobs and support the industry’s goal of achieving $6 billion in exports.
"If we don’t look ahead at the sort of cars we’ll be driving early in the 21st century, we may find they are mostly manufactured overseas and imported," he warns. "Overseas car companies usually don’t use foreign suppliers in these kinds of projects. If there was no local manufacture of hybrid power units, Australian industry could miss out in future.
"As it stands, our component industry has a depth to it far greater than the size of the aXcessAustralia car, unveiled in 1998 to showcase the industry’s technological capability – and which has since been a key factor in landing several major export contracts.
More information:
David Lamb, CSIRO AATC 0417 302 230 or 03 9662 7787
Wilna Macmillan, CSIRO Manufacturing Science &Technology 03 9545 2804
The aXcessaustralia Low Emission Vehicle Drive Train
Introduction
Vehicles cause between 70% and 90% of Australian urban air pollution and transportation contributes approximately 17% of total Australian greenhouse emissions . Therefore, any serious attempt to reduce or prevent worsening air pollution or greenhouse gas emissions has to include reducing car emissions.
The first aXcessaustralia project was a conventionally powered car that displayed Australian innovation, the car was well received around the world and this has encouraged a second project. This second aXcessaustralia project, the LEV or Low Emission Vehicle, provides the opportunity to show recent technological developments and demonstrates how to build an exciting, affordable, less-polluting car.
This second project was possible because Australia’s national research agency, CSIRO, has developed a number of key technologies for hybrid and electric vehicles, namely:
1. Valve-regulated, lead-acid batteries.
2. Super-capacitors.
3. Switched-reluctance, electric motors.
All these technologies are characterised by excellent performance, ruggedness, and low cost, they are therefore ideal for automotive use.
The paper provides an overview of the innovative approach taken for the drive train and how the drive train is integrated with the storage systems to provide a particularly low-cost, series, hybrid vehicle.
The problem
The aXcessaustralia LEV is a series hybrid with three sources of electrical energy:
1. Petrol, via a combustion engine and a generator.
2. Stored energy from a battery pack.
3. Stored energy from a capacitor bank.
Petrol provides the power for the vehicle, supplemented by electrical charging of the batteries from the mains supply. The usage of petrol is minimised by providing energy storage. The ideal energy storage would have a large capacity and be capable of fast charging and discharging. This is difficult to achieve with only one type of storage. The aXcessaustralia LEV overcomes this problem by using batteries to provide a large capacity and capacitors to provide the high power charge and discharge capability.
To optimise the generator and the transmission of energy from the generator a voltage of at least 200 V is necessary at high powers and a lower voltage at lower powers. However, for the batteries a much lower, approximately constant, voltage of around 60 V is the optimum. For the capacitors a high voltage of over 200 V is optimum when they are fully charged, but the voltage falls (unlike a battery) when they are discharged. There are therefore three conflicting voltage requirements for the car. In a conventional solution to these conflicting voltages a number of compromises are made, namely:
1. The generator voltage is regulated to a constant high voltage of over 200 V and does not vary with engine power.
2. The battery design is compromised and a high voltage of over 200 V is used to be compatible with the generator voltage.
3. A DC to DC converter is used to convert the changing capacitor voltages to the same, constant, high voltage.
The aXcessaustralia LEV overcomes these limitations using a unique design of transmission and therefore considerably reduces the cost of the vehicle. This novel transmission is the subject of this paper.
Hybrid-electric vehicle (HEV) battery packs are subjected to multiple charge- discharge cycles at high rates and are required to operate for many cycles below a full state-of-charge. At present, lead-acid batteries are the only cost-effective option for use in mass-produced HEVs. State-of-the-art, commercial lead-acid batteries, however, require improvement if they are to tolerate the harsh conditions of HEV duty. In response to this, the Novel Battery Technologies Group has developed a new design of valve-regulated lead-acid battery specifically for use in HEVs. The new battery, called the ‘double impact’, has current takeoffs at both ends of the positive and negative plates and has been shown to significantly outperform state-of-the-art commercial batteries under both HEV and electric vehicle (EV) conditions.
The operating temperature of the double-impact battery under HEV and EV conditions is much reduced compared to that of commercial equivalents. This simplifies the cooling requirements of the battery pack, improves system safety and reduces both degradation of the expander used in the negative plate and corrosion of the positive grid. Moreover, it minimises electrolyte dryout, a condition that can increase the internal resistance of the battery and lead to problems with charge acceptance later in life.
The reduction in operating temperature can be attributed directly to the dual-tab design of the battery. In traditional units, which have only one current takeoff or tab per plate, there is a significant increase in current density, or ‘current concentration’, towards the tab during high-rate charge or discharge. As heating within the battery is related to both the square of the current and the resistance of the battery (i.e., I 2R), high, localised current densities can result in large heating effects in these regions. The inclusion of a second current takeoff decreases the current density at each tab and considerably reduces heating effects.
The capacity and cycle-life under HEV and EV conditions is also much improved compared to commercial designs. Once again, this is a direct result of the dual-tab design. Capacity increases are a result of the battery plates operating at a uniform temperature, which allows ‘even active-material utilisation’ throughout the unit. Improvements in cycle-life are a result of lower operating temperatures which act to slow down normal degradation processes, and also improvements in positive grid design which reduces corrosion wihin the battery.
Overall, the double-impact battery is safer to use and provides improved cycle life and capacity under both HEV and EV duty, relative to that of current commercial units."
