By 2050, most vehicles will need to be electrically propelled, with a battery to store energy or an on-board hydrogen fuel cell to generate electricity
27 Oct 2014 | 3701 Views | By Autocar Professional Bureau
By 2050, most vehicles will need to be electrically propelled, with a battery to store energy or an on-board hydrogen fuel cell to generate electricity, if emission targets set by governments are to be met. That’s the conclusion of an expert team responsible for penning Towards Sustainable Road Transportpublished by ...
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By 2050, most vehicles will need to be electrically propelled, with a battery to store energy or an on-board hydrogen fuel cell to generate electricity, if emission targets set by governments are to be met. That’s the conclusion of an expert team responsible for penning Towards Sustainable Road Transportpublished by Elsevier.
The three authors are senior research chemists who have spent their professional careers working in the fields of energy and electrochemistry. More than 300 pages packed with information describe the growth and technical development of road vehicles during the 20th century, and the state-of-the-art power sources and advanced vehicle designs now needed to meet the 80 percent reduction required in global emissions over the next 35 years, and needed to protect the next generation.
“Over the past 25 years, the auto industry has reduced its greenhouse gas emissions by 20 per cent from a 1990 baseline, which is less than 1 per cent a year,” says Patrick Moseley, president emeritus of the Advanced Lead–Acid Battery Consortium (ALABC). “Over the next 35 years, the industry will have to sustain the 2 to 3 percent annual reduction that it is now achieving. That’s a tall order.”
Moseley’s co-authors are Ronald Dell, former head of applied electrochemistry at the UK Atomic Energy Authority and David Rand, a former chief research scientist of the Commonwealth Scientific and Industrial Research Organisation (CSIRO) of Australia. Their first edition book focuses attention on road transport, a key aspect of human activity among the many sectors – including agriculture, industry and power – that require attention if sustainable development on a global scale is to be achieved.
“Our work examines the prospects for an evolution of the global transport system, which currently consumes irreplaceable resources and degrades the environment, towards one with a modus operandi that will be both supportable and benign,” says Dell. “This is a considerable challenge. The global fleet of motor vehicles of all types, including two-wheelers, is now around one-and-a-half billion, of which one billion are cars. This is expected to reach two billion soon after 2020, with a rapid increase in the number of internal combustion engine vehicles (ICEVs) anticipated in China and India, which is an understandable increase given the aspirations of these two enormous populations.”
“Automotive manufacturers face the conflicting demands of customers for vehicles with ever-improved performance, safety and comfort – but without any appreciable increase in cost,” says Rand. “This is being resolved through advances in vehicle design and in particular through refinement in propulsion technology. The trend is towards smaller internal combustion engines augmented by intelligent electrification with no decrease in power; this combination being especially effective in reducing both emissions and fuel consumption.”
All three authors have been heavily involved throughout their careers in electrochemistry and the development of advanced battery designs and power sources. So not surprisingly they express their views on numerous advanced battery chemistries and supercapacitors being considered for use in road vehicles.
“Batteries in different categories of road vehicle are required to perform widely disparate duty cycles,” says Moseley. “In a conventional ICEV, the starting, lighting and ignition battery is maintained at almost a full state-of-charge (SoC) of between 85 and 90 percent. In battery electric vehicles (BEVs), the SoC of the cells declines throughout the journey from 100 to 20 per cent, and once their chemical energy is depleted they have to be recharged for the next journey. In hybrid electric vehicles (HEVs) such as the Toyota Prius and especially the new breed of low-voltage (48V) super hybrids from Audi and Kia and other carmakers, the batteries are subject to a critical high-rate partial state-of-charge (HRPSoC) operation of between 50 and 70 percent.”
The above duty cycles explain why lithium-ion batteries, with their high-voltage cells and high specific energy (Watt-hours per kilogram), are currently utilised for pure electric vehicles despite their high cost and need for cooling, while the recent breakthrough of advanced lead-carbon batteries is better suited to both stop-start and 48V vehicles. The book’s co-authors confirm that even though the search for more advanced battery chemistries continues, there appears to be little prospect in the short term of finding a battery system that can provide a BEV driving range between charges of much more than 150 miles (240 km), while withstanding rapid recharging for a satisfactory life and being manufactured at a competitive cost.
“It could be 20 years before possible next-generation lithium-air batteries make it out of the laboratory and into the car,” says Rand.
Given the limitations of BEVs and doubts about developing an entirely new and affordable battery with satisfactory performance and safety, the book describes why the automotive and transport industry meanwhile has turned its attention to hybrid vehicles, in which a battery powered motor-generator is combined with a heat engine to provide a more efficient propulsion system without subjecting motorists to ‘range anxiety’.
“Hybrids do not eliminate tailpipe emissions, but they do reduce them by making use of the hydrocarbon fuel more efficiently and, crucially, the vehicles do not suffer from the range limitations that beset BEVs,” says Dell. “Hybrids are also in tune with progressively tighter emissions legislation, because there is a full range of designs available from the simplest stop-start and 48 volt forms, with the least additional cost, through to the most expensive hybrids. Thus it is possible to introduce vehicles with increasing degrees of electrification and cost/benefit improvements.”
The book also refers to David Rand’s involvement in more than 20 years of research undertaken by CSIRO that has contributed to the improvements gained in the performance, power capability and cycle-life of valve-regulated lead-acid (VRLA) batteries. Recently, CSIRO has provided a means for overcoming the problems of the HRPSoC duty cycle through the invention of a radical new design of VRLA battery, in which the negative plate is protected from the deleterious effects of high-rate charge and discharge by sharing the current with an integrated supercapacitor. The innovative configuration of the CSIRO UltraBattery combines a VRLA cell with an asymmetric supercapacitor in a single unit without the need for extra electronic control.
“This technology is less costly, is more compact and occupies less volume than the combination of a conventional battery in parallel with a conventional supercapacitor,” says Moseley. “As part of its continuing research programme, the ALABC has fitted prototype units constructed by the Furukawa Battery Company in Japan to a Honda Insight, which successfully completed 100,000 miles (160,000km) at Millbrook proving ground in the UK.
“Interestingly, an increase in the quantity of carbon in the negative active-material can promote a significant increase in battery life under HEV duty. An extensive test on East Penn’s licensed design of UltraBattery™ was able to reach 167,000 miles (267,000km) in the laboratory. The ALABC has since completed another 150,000 miles of real world driving in Arizona in a Honda Civic hybrid – a particularly demanding HRPSoC operation – and continues to run the vehicle to determine the full lifetime of the batteries. So far, they show no performance degradation and remarkably the individual battery voltages of the pack are beneficially converging as they age – though as yet we know not why.”
Several major car companies are now actively working towards introducing lead-carbon batteries into the abovementioned stop-start and 48V mild super hybrids. For instance, Kia has announced its preference for this new battery chemistry over a lithium-ion alternative because: ‘lead-carbon cells require no active cooling, are more readily recycled at the end of the vehicle’s life, and can function more efficiently at sub-zero temperatures’.
The assistance of Dr Jacquie Berry, Professor Dame Julia King and Sir Robert Watson in the preparation of this comprehensive tome is acknowledged by the three authors.
“For students young and old interested in the science and engineering of the automotive sector, this is a valuable read,” says Dame Professor Julia King, Vice-Chancellor of Aston University, who in 2007 was appointed by Gordon Brown, the then UK Chancellor of the Exchequer, to lead a review of future vehicle and fuel technologies that could help to reduce carbon emissions from road transport. “This in-depth book provides a comprehensive historical context, from the early 19th century, with the discovery and development of the steam engine and the advent of railways, through to the 21st century and the crucial role to be played by governments now, and over the next 35 years, if the global targets for the reduction of CO2 and NOx emissions are to be met.”