The automotive future is electric, but what sort of electric? Will it be based on today’s hybrids or totally battery-powered vehicles? Or will it be fuel cells powered by hydrogen? This is the challenge facing executives in the automotive industry, which, after over a century of focus on the internal combustion engine, is going through a major technological upheaval. We should not forget, however, that electric vehicles have been with us for roughly the same length of time, but when fossil fuel reserves are dwindling and climate change threatens the planet, their day is truly dawning.
According to a 2010 report by the UK’s Royal Academy of Engineering, pure and hybrid electric cars may account for 5-10% of the European automotive market by 2020. However, this is only likely to be achieved if governments help to overcome the financial hurdles of infrastructure, such as charging points that can cost around €6000 each, and cross-border standards for plugs and billing. ‘There is no obvious source of funding for such infrastructure,’ says the report.
In the US and China, the infrastructure issue is well understood. In the US, Pike Research, a market research firm specialising in clean technology, forecasts that there will be at least 15m charging points in major cities across the continent by 2015, while the Thomson Reuters newswire Planet Ark reports that the Chinese government is said to be planning to install at least 10m charging stations by 2020. Like other countries, the Chinese government is offering incentives to purchase electric cars and estimates that domestic production of electric cars will reach 1m by 2010.
But which of the various types of electric vehicles is likely to be the winner? Despite rapid developments in the battery field, there are still the major drawbacks of range and charging time; although vehicles with lithium batteries can offer ranges of up to 100 miles, like, for example, Nissan’s Leaf, or Leading Environmentally-friendly points in major cities across the continent by 2015, while the Thomson Reuters newswire Planet Ark reports that the Chinese government is said to be planning to install at least 10m charging stations by 2020. Like other countries, the Chinese government is offering incentives to purchase electric cars and estimates that domestic production of electric cars will reach 1m by 2010.
But which of the various types of electric vehicles is likely to be the winner? Despite rapid developments in the battery field, there are still the major drawbacks of range and charging time; although vehicles with lithium batteries can offer ranges of up to 100 miles, like, for example, Nissan’s Leaf, or Leading Environmentally-friendly Affordable Family car, expected on the streets of Japan and the US early in 2011, and the UK in March 2011. However, this range can fall in cold weather, with up to a 45% power loss due in part to the need to heat the vehicle interior as well as the cold’s effect on battery performance and a full charge will take up to 11 hours. Faster charging can reduce this time to eight hours but this also potentially reduces battery life.
Another key factor in the development of automotive batteries is sustainability, particularly the future availability of various rare earth metals used in their construction. The Royal Academy report, however, notes: ‘the diversity of possible battery chemistries [lithium, nickel, sodium and zinc-based] suggests that a shortage of battery materials is unlikely…in the foreseeable future.’
The development of battery materials is therefore focused on nanomaterials. US researchers at the Rensselaer Polytechnic Institute, Tory, New York, are working on ‘nanoscoops’, so-called because they resemble a wafer cone with a scoop of ice cream on the top. Formed from a carbon nanorod base topped with a thin layer of nanoscale aluminium and a nanoscale silicon nanoscoop, the material is flexible and able to accept and discharge Li ions at extremely fast rates without sustaining significant damage when used as the anode in a Li-ion battery (Nano Letters, DOI: 10.1021/nl102981d).
The anode of a Li-ion battery physically grows and shrinks as the battery charges and discharges, increasing in volume as Li ions are added and shrinking as the battery discharges. This can result in internal stress leading to battery failure. In current Li-ion batteries, the charging rate is kept low deliberately to avoid this problem. The nanoscoop technology exploits the different expansion rates of the materials to relieve the stress and can therefore increase charge/discharge rates Ford by 40 to 60 times, compared with conventional batteries, while maintaining a comparable energy density.
‘Charging my laptop or cell phone in a few minutes, rather than an hour, sounds pretty good to me,’ says Nikhil Koratkar, a professor in the department of mechanical, aerospace and nuclear engineering at Rensselaer. ‘Moreover, this technology could potentially be ramped up to suit the demanding needs of batteries for electric automobiles.’
Batteries for electric vehicles have to deliver high power densities as well as high energy densities. In conventional electric vehicles supercapacitors are used to perform power-intensive functions, like starting the vehicle and rapid acceleration, in conjunction with conventional batteries that deliver high energy density for normal driving. Koratkar believes the nanoscoop approach may enable these two systems to be combined into a single, more efficient battery.
The current limitation of the nanoscoop approach is the relatively low total mass of the electrode. Kortkar says his team is therefore looking at the possibility of growing longer scoops with greater mass and the development of a method for stacking the nanoscoops on top of each other on large flexible substrates. Another possibility being explored is the growth of nanoscoops on large flexible substrates that can be rolled or shaped to fit the contours or chassis of an automobile.
Potential shortages of rare earth metals affect the production of electric motors as well as batteries. Japan’s Toyota is seeking an alternative to motors based on rare earth metals. The company is said to be developing a device based on the inexpensive induction motors used in household appliances and sees the development of motors without magnets as part of the evolution of electric motors. But Toyota is not the first company to look at such alternatives. In the US, a start-up company Novatorque launched its first motor based on conventional iron rather than rare earth magnets in 2010, but, in this case, it was designed for industrial equipment applications, although the company believes the technology can be scaled up for larger applications, possibly including cars.
The Novatorque technology uses a conical design for the central hub that increases the surface area and therefore the magnetic flux transmission, meaning ferrite magnets can be used instead of rare earth materials. In addition, the amount of copper required for the motor coils is reduced, thereby offering a second cost saving.
Gasoline hybrids to dominate the electric vehicle sector
Despite these developments, in the short term the Royal Academy of Engineering believes that gasoline hybrids, eventually using biofuels, will continue to dominate the electric vehicle sector due to their flexibility, extended range and independence from a charging network, as General Motors is currently demonstrating with its Volt – to be known as the Ampera in Europe.
The Volt was recently selected as American Car of the Year at the Detroit Motor Show: another accolade to add to its 2011 Green Car of the Year award and Motor Trend magazine’s Car of the Year award.
Toyota’s Prius, which mostly uses fossil fuel power topped up with electrical power produced mainly from regenerative braking, has been the first generation standard bearer for the hybrid concept but GM’s Volt/Ampera is a second generation hybrid – and it takes just three hours to recharge its battery pack, which alone will give a range of around 40 miles, sufficient for a day’s commute but not a longer journey. Together with the output from its small gasoline engine, the Volt is claimed to offer a range of 375 miles between fill-ups.
However, Ford’s recently announced electric Focus has approached this charging issue from another direction. While the Focus’ battery will at 23kWhr be slightly smaller that the 24kWhr battery in Nissan’s Leaf, the car will feature an onboard 6.6kW charger, compared with the 3.3kW charger fitted on other vehicles. Coupled with the 32A stationary charging station that Ford recommends, the Focus can be charged in three to four hours. The Li-ion battery system, developed in cooperation with Korea’s LG Chem, uses an active liquid heating and cooling system for thermal management, cooling the battery on hot days and heating it on cold days, to maximise battery life and driving range.
Another problem to be overcome is that electric vehicles are not lightweight, despite the elimination or downsizing of the conventional gasoline drive train. While battery developers have made some headway in making them lighter – they still weigh 400lb or more – they also require a heavy inverter to convert their direct current to alternating current to drive the electric motors in the drive train.
Weight reduction, long the focus for conventional fossil fuel vehicles, has therefore received another impetus along with the search for new materials for batteries than can be charged faster without the damage experienced today. Weight improvement can also be achieved by replacing metal parts with plastic components, while necessary metal parts can be made lighter and stronger through the use of nanotechnology.
Bayer MaterialScience, for example, has begun combining different functions into one moulding with its BayVision tailgate prototype, shown for the first time at K 2010. The single-part tailgate moulded in Makrolon polycarbonate has a seamless outer skin incorporating an integrated backlite. The non-transparent areas are either backprinted in a dark colour or back-injected with a black frame material using two-component injection moulding, which is also used for the relevant fixings and guides for all the lighting components that are located behind the outer skin. Light sensors for opening and closing the tailgate can also be incorporated behind this skin, eliminating the need for separate handles and locks.
A fully polycarbonate tailgate would not be sufficiently stiff to meet automotive load requirements so a new concept based on plasticmetal composite technology has been developed. Reinforcing ribs of polycarbonate or its blends with acrylonitrile butadiene styrene (ABS) are moulded on the inside of the tailgate module with strips of sheet metal inserted in the grooves between the ribs and bonded with adhesive, which also evens out differences in heat expansion between the metal and plastic. The metal inserts can be used as mountings for locks, hinges and gas struts to hold the tailgate open.
Conducting polymers can reduce the amount of metals used for everything from electrical cabling to printable electronic circuitry. Polymers can also be used for glazing applications – the day of the plastic windscreen is not that far off. Plastic windscreens, and other glazing components like the panoramic roof, may also be capable of acting as an aerial for the in-car entertainment; include heating elements to clear ice and snow; and be able to change colour depending on the level of sunlight. These same glazing components incorporating solar cells might also be used to generate electricity to charge the batteries. Safety, as well as sustainability, is a key driver for materials development. Although the massproduced plastic car body still has to be achieved, many exterior panels and trim are already polymer-based. The 2010 European Pedestrian Impact Phase 2 standard, for example, will encourage the use of malleable materials, foams and other energy-absorbing materials in bumpers designed to meet pedestrian lower-leg impact requirements.
A workshop organised in 2010 by Suschem, the European Technology Platform for Sustainable Chemistry that seeks to boost chemistry, biotechnology and chemical engineering research, development and innovation, identified the need for the development of a ‘mono-material solution’ car or a car with fewer material types for ease of recycling as one of its material research goals, along with lightweight natural fibre composites and green tyres to reduce rolling resistance. The EU End of Life vehicle legislation, which will increase recyclability requirements from 80 to 85% in 2015, will be a key driver behind such developments.
But are electric vehicles any real improvement over their fossil fuel predecessors in terms of sustainability? To begin with, the electricity to charge them has to be produced somehow, but will renewable sources like wind and solar power or biomass be able to satisfy the demand? And of course, there is clean coal or nuclear but the sequestration of carbon dioxide from coal-fired power stations is still in its infancy while nuclear power still remains under the shadow of waste fuel disposal and its overall potential hazard.
Certainly Ford is claiming improvements in sustainability for its new Focus. The US assembly plant to produce both the gasoline and electric versions of the car will have one of Michigan’s largest solar power generation systems, while the home charging station developed jointly with North American producer of electrical devices Leviton, will have an outer shell formed from up to 60% post-consumer recycle plastic. Inside the Focus, seat cushions will be produced from 8% soya-based foams, while a material called Lignotock, derived from 85% wood fibres, will be used behind the door cloth to give a weight reduction as well as sound-deadening benefits, compared with conventional glass-reinforced thermoplastics.
For the chemical industry, the drive to the electric automobile presents a new range of challenges and will increase demand for more plastics and novel materials, with new functionalities, as well as new adhesives and printed electronics. This electric future is certainly charged with potential.