12 March 2017

The future of the car in 2050




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FIRSTLY LOOK IN SHORT


The car of the future will be economical in its use of available resources. It will be designed to have as little impact on the environment as possible. It will also be safer, as it will incorporate a level of artificial intelligence that enables it to compensate for driver error. The car of the future will be networked with other vehicles in the vicinity, and this will extend its range of perception far beyond that of its own on-board sensors. By 2020, the introduction of completely new technology, and the further development of that which is already tried and tested, will make the car into far more than just a means of getting from A to B. 

The motor car is, and will remain, a product with an emotional appeal, the character and design of which must accord with the lifestyle of the user. However, this does not mean that it makes sense, for example, to explicitly label a car that is especially suitable for older drivers as ‘OAP-friendly’. Accordingly, the car of the future will not be able to sell itself purely by virtue of its many innovative features or by how environmentally friendly it is – it will be the complete package that counts. Engine and drive technology Drive technology will be the decisive factor in bringing about significant changes in the future of the car. The ongoing development of the internal combustion engine has been steady rather than spectacular, but the potential is there for lower fuel consumption and for making it more environmentally friendly in the foreseeable future. 

Refinements in fuel injection technology are raising engine efficiency and reducing harmful emissions. There are also indications that the classic petrol engine can be married to the more positive characteristics of the diesel engine.  Both petrol and diesel will have to be replaced by alternative fuels, if only because our reserves of oil are finite. For that reason, the blending of biofuels with oil-based fuels in the European Union is set to increase from the current 5% level to 20% by 2020. The task of research today is to discover how we can produce biofuels in the quantity needed and what precise effect these have on the combustion process.  The efficient use of given energy resources must not be left to the traditional combustion engine alone. 

Electric drive motors are being introduced in cars, initially to supplement the internal combustion engine in so-called hybrid cars, and in due course, as stand-alone propulsion units in ‘zero-emissions vehicles’, which emit no harmful substances during on-road use. Electric motors have the additional advantage of generating a high level of torque from a standing start, so that handling during acceleration does not give the impression of driving some sort of ‘ecomobile’ where compromises have been made on performance. The electric motor, which also acts as an electrical generator, regains some of its ki netic energy during braking, and this increases its efficiency, particularly under urban driving conditions. 

The electric drive system stands or falls by the issue of how it manages to store energy. In this regard, durable and powerful rechargeable batteries of a high capacity are indispensable. One promising candidate is the lithium-ion battery, but its energy density and operational safety will have to be significantly improved before it can be used successfully in the motor car. A flexible ceramic separator for lithium-ion batteries developed in Germany promises further possibilities in the future. 


Another means of propulsion holding out prospects for the long term is the use of hydrogen to generate electric power in on-board fuel cells. Therefore the ‘hydrogen car’ is really also an electric car – although there is also the possibility of using hydrogen directly as a fuel for the internal combustion engine. Apart from pure water, the fuel-cell car emits virtually no harmful substances at all and is frequently seen as the ‘Holy Grail’ of automotive development. There is still a long way to go, as fuelcell technology falls far short of being suitable for daily use and is not cost-effective in the medium term, even in large-scale production. 

Moreover, a suitable hydrogen distribution infrastructure with extensive coverage would have to be set up, something that is unlikely to happen until such time as it becomes apparent that fossil fuel reserves are close to running out. In any case, hydrogen itself is a fuel which has first to be extracted from other forms of energy.  Since electrical power is already extensively available from every mains socket, a high-quality battery is already a good alternative to hydrogen as a means of storing energy. So-called supercapacitors carried on board can supplement the battery, as they store and discharge electrical power very quickly. But supercapacitors too require considerable further research and development.  The mechanics of the motor car Modern combustion engines are gradually becoming more efficient, a fact that we might expect to see signs of in falling fuel consumption. 

With few exceptions, however, vehicles are getting heavier, which in turn calls for increased engine performance. This increase in weight is mainly due to increasingly complex specifications and more stringent safety requirements. Mechanical components are required to compensate for this. Above all, the requirements of passive safety need to be met through improved lightweight construction in the area of bodywork, i.e. a ‘weightneutral’ solution. Lightweight materials such as aluminium, magnesium and fibre-reinforced plastic (FRP) can help to reduce the mass of the vehicle. Even steel has potential here – for example through the recent development of ‘Twinning-Induced Plasticity (TWIP) Steel’, which absorbs the deforming energy of a collision.  

In the future, ‘by-wire’ technology will transform chassis construction. Full electrical control of steering and braking will reduce the proportion of mechanical and hydraulic components. The advent of the all-electric car will also drive forward the reduction in the use of hydraulics. But at the same time, there will be a need to design and approve for general use redundant systems that are effective under all operating conditions. Electronics Vehicle electronics are increasingly setting the pace as regards new technological development. The sophisticated use of electromechanical actuators for valve control will make it possible to produce a cam-free engine. 

New driver assistance systems have been introduced using highperformance electronics complemented by appropriate sensors. Active safety systems can already correct driver error to prevent accidents. Laser scanners and cameras survey the area around the car to give warning of potential collision during a lane change manoeuvre. In the future, onboard cameras with three-dimensional imaging will even keep an eye on traffic emerging from side roads and at junctions. They will be able, for example, to alert drivers in real time to approaching cyclists who would otherwise be out of the range of vision. 

We can expect to see driver assistance systems playing a much greater role in steering and braking. The long-term aim is the autonomous car, in which the driver can concern himself during the journey with activities other than controlling the vehicle. However, before this vision can become a reality, complex questions of driver psychology need to be addressed – such as how he will react to being ‘nannied’ – and various legal questions must also be clarified, including who bears responsibility if the technical systems make a wrong decision? 

Currently, a driver observes only the immediate surroundings of the vehicle. Night vision equipment and the laser scanners and cameras mentioned above can support him in this. Vehicle telematics such as traffic alerts on the radio and warnings of traffic jams broadcast on data channels and evaluated by satellite navigation systems extend our perception of what is happening on motorways and major roads over a wider surrounding area. Still missing, however, is an information source about traffic events in the immediate vicinity and in every street. This is where car-to-car communication comes into its own, broadcasting information gathered by individual vehicles to other vehicles in the immediate vicinity over the radio without having to go through a central agency such as a traffic management centre. 

In this way, warnings about unexpected black ice a few hundred metres ahead or a traffic jam over the brow of a hill or around a corner can be transmitted to other road users. In respect to networked car-to-car communication, though, we have to ask ourselves the fundamental question whether it would not be possible to achieve precisely the same positive effect by consistently adapting our driving to the road conditions. Nonetheless, it is easier to influence this technical development than the driving habits of the all too human road user.  Conclusion There will not be a single ‘car of the future’. 

Already, the designs emerging from the drawing boards of the various car manufacturers range across a broad spectrum, from mini models which, by their very nature, are environmentally friendly, up to luxury limousines with fuel consumption comparable to that of the current mid-range car. Development proceeds slowly, notably in the field of fuel consumption, since other factors offset progress in engine technology. As both German and European manufacturers have been unable to live up to their voluntary undertakings to reduce fuel consumption over the last ten years, the European Union plans to make the target figure they laid down compulsory by 2015. Parallel to all of these ongoing improvements are a number of other innovations that are not only taking hold in vehicle technology but also require a change in mindset. 



The European automobile industry is not overly fond of the hybrid car but is nonetheless pursuing this goal assiduously. The next step is the introduction of fuel cells in place of the combustion engine, but this would involve the construction of a hydrogen distribution network. Before this can happen, there will have to be a fundamental change in the general situation – for example, in the price and availability of crude oil and biofuels. If significant advances can be made over the next few years in battery technology, it may be possible to bypass the costly concepts of both the full hybrid and the fuel-cell powered car. In their place, there could be cars which run entirely on electricity, with batteries that are charged by plugging into a mains socket, or possibly while the vehicle is on the road by means of an on-board combustion engine running at a constant speed consistent with optimum efficiency. Whether established vehicle manufacturers will be prepared to change their way of thinking and follow this line of development remains to be seen. 

It would be an attractive option, given the political will to crack down on vehicle CO2 emission levels. Having its own electric-powered models significantly reduces a manufacturer’s average emission figures for its entire production range. So in the next few years, we may well see the future of the motor car being significantly influenced by factors which have nothing to do with traditional automobile technology. Steady improvements in current technology and an openness to new ideas will be the key to securing our future mobility.


INTRODUCTION


‘The future of the car’ is a public status report from the Association of German Engineers (VDI), describing current trends over the next ten to fifteen years together with their various implications. The term ‘car’ is to be understood as meaning vehicles in general. Beyond the remit of this report are any wider policy considerations such as the role of the car within the relevant infrastructure, e.g. increasing traffic efficiency through the use of telematic systems or the relationship between private and public transport. Car manufacturing and engineering will also not be addressed. The automobile industry is reliant on society’s need for transport and mobility and road use is the basis of its existence. 



Every seventh job in Germany is directly or indirectly dependent on the car. In addition, the automobile sector is still seen today, as it has in the past, as the leading dynamic force for technological progress in Germany – German automobile technology takes its place amongst the best in the world. Freeflowing traffic is also a fundamental requirement for the functioning of the economy and of society, as it guarantees the mobility these require. The volume of movements by individual carriers is closely linked to the growth of the national product. A smoothly functioning traffic system and an efficient transport distribution network provide the basis for the success of the third-largest sector in the German economy: logistics. Employing 2.6 million people and generating an overall turnover of more than 150 billion euros, it represents about 7% of gross domestic product. 

In the future, an annual growth rate of up to 6% is expected in the turnover of the sector overall. Against the background of Germany’s growing importance as a transit country, it will be even more important in the future to improve the competitiveness of the German vehicle and transport industry, to reduce the impact of traffic and to ensure safe and reliable transport options for the whole population. The United Nations estimates that world-wide vehicle ownership is set to double by 2030, from the current figure of 750 million to around 1.5 billion private and commercial vehicles. The driving force behind this development is the sharply increasing demand for cars in the rapidly expanding markets of China, India, Korea, Brazil and Russia. The increasing standard of living of the populations of these regions will lead to a greater desire for enhanced personal mobility and this in turn will lead to increased car sales and to more frequent usage.


TECHNOLOGICAL DEVELOPMENTS AND TRENDS



One of the challenges facing those designing the car of the future is the development of environmentally friendly vehicle technologies. These include lightweight construction, new drive concepts such as hybrid drives and fuel cells and alternative fuels such as hydrogen and biogenic fuels. One further focus is on the development of innovative driver assistance systems that are intended to make driving more comfortable and, above all, safer.

2.1 Bodywork Over the past 15 years, the weight of the average family car has increased by around 30%. An analysis of new vehicle registrations in Austria shows that, in the years from 2000 to 2005 alone, the weight of the average vehicle increased by 11%. Despite weight savings in engine blocks and bodywork made of light alloys, modern cars are getting heavier and heavier. This is happening because of the addition of new electronic components, above all in safety technology (for example ABS, ESP, seat belt tensioners, active steering and four-wheel drive) and because of the increasing popularity of comfort features (air-conditioning, electric windows and seats). But the more a vehicle weighs, the more fuel it will consume and the more pollutants it will emit. 

As a rule of thumb, reducing the weight of a vehicle by 100kg will reduce fuel consumption by around 0.5 litres per 100 km. By 2010, it is intended that there should be a 17% reduction in vehicle weight, i.e. equivalent to an average 250kg per vehicle. [VDI 05] There is certainly a conflict between, on the one hand, the tendency to add on more and more safety and comfort features, all of which make the vehicle heavier, and on the other, the general need to shed weight. This dichotomy can, however, be resolved by the use of weight-saving materials in conjunction with customised construction and manufacturing technologies on the assembly line. 

The choice of material depends very much on properties that are in part complementary, such as weight, stiffness and ductility, failure limits, manufacturing and processing characteristics, availability, whether it can be recycled and above all on price. New joining techniques in automobile construction are supplementing classic (laser) welding processes and making the joining together of diverse materials possible. Modern gluing technologies are being developed for steel, aluminium, magnesium, glass, plastics and bonded fibre materials as well as hybrid materials, thus increasing the torsional rigidity of the bodywork, reducing vibration and protecting from corrosion.

Lightweight construction Lightweight construction materials such as aluminium, magnesium and bonded fibre materials should help to reduce weight and allow shorter manufacturing times, without compromising safety, comfort or reliability. Successful lightweight construction ideas are based on specific expertise in many areas of materials technology and engineering science and on ‘systemic’ thinking. Robust processes in lightweight construction go hand in hand with applied research into materials, configuration, process development and qualification of procedures, and with associated modelling and simulation. 

The multi-material construction method is seen as key to super lightweight construction. For each individual element in the construction of the vehicle, those materials are chosen which best meet the requirements with a minimum amount of weight. For small series production vehicles, the multi-material approach is already a reality; as regards volume and medium series production, though, there have as yet been only a few hesitant steps towards such a systematic combination of diverse materials in structural bodywork. The task of developing a multi-material construction method that can also be applied cost-effectively to high-volume cars is being researched at present in various development projects. [Sah 06] In the past, manufacturers have primarily pinned their hopes on the light metal aluminium, as this substance has a low mass and does not rust. 

In the year 2000, around 100kg of aluminium were used in the manufacture of the average car, according to figures from the European Aluminium Association. This rose to 132kg in 2005. The fact that aluminium is being used more and more in vehicle construction can also be attributed to laser technology. Some years ago, processes were developed that make possible the welding of aluminium components by laser.

Magnesium is even lighter than aluminium. This substance has a density of only 1.8 g/cm³. By comparison, aluminium weighs 2.7 g/cm³ and steel just under 8 g/cm³. Magnesium is available in almost limitless quantities and it can be easily processed and recycled. For these reasons, this light metal is becoming a favourite amongst lightweight construction materials. 

In the new Golf, the gearbox housing is made from magnesium and weighs around 25% less than the aluminium version, which was already lightweight. Magnesium is also to be found in the rear hatch of the VW Lupo, in the dashboard mounts of the Opel Vectra and in the housing of a seven-speed automatic gearbox developed by Mercedes-Benz. In the Passat, 14kg of the light metal are already used as standard. And yet, no matter how great the advantages of magnesium may be, it still has disadvantages. Research and industry will both own up to gaps in their knowledge. Under what forces and in which places do magnesium components fail in an accident? How can magnesium be joined without flaws? How can it be protected from corrosion?

Magnesium is also suitable for the injection moulding process known as thixomoulding for manufacturing high-precision components with a wall thickness of 0.5mm. This has not been possible up to now with conventional injection moulding techniques. For thixomoulding, the magnesium is heated to a temperature of around 100 degrees Celsius below its melting point of 650 degrees. It changes to a ‘thixotropic’ state in which, subjected to sheering forces, the viscosity of the material is lowered. Just like a form of dough, the metal can then be very precisely shaped using relatively little pressure. 

At the present time, however, it is only possible to handle masses of up to 3kg at a time. Machines able to process up to 6kg of material are only just beginning to come onto the market. Because of the lower temperatures applied, the finished item shrinks less and is also less porous. Magnesium thixomoulding is also more environmentally friendly than injection moulding because it requires less heat energy input. Thixomoulding is not yet used for working aluminium because in its liquid state this metal behaves more aggressively than magnesium and can therefore only be worked with expensive ceramic tools. [Tec 07] Fibre-reinforced materials such as fibre-reinforced plastics can also contribute to lightweight construction. The original field of application for fibre-reinforced materials is mainly in the aerospace industry. Current examples of use in aircraft construction are the Airbus A380, which consists of around 35% of these lightweight construction materials, and the new long-haul aeroplane, the Boeing 787 Dreamliner, with up to 50% fibre-reinforced materials. The replacement of the conventional aluminium in the fuselage and wings reduces weight and gives a fuel saving in the order of 20% in the case of the Boeing 787.

However, fibre-reinforced plastics are rarely to be found in the mass production of cars, as the manufacture of this material is very complex and expensive. But new production processes are now making the material more attractive for use in compact and medium-sized vehicles too. In a pilot project for the BMW 3 series, a bracket was ‘tailor made’ from a Long Fibre Thermoplastic (LFT) compound. This hidden component carries the headlights, the bonnet locking mechanism and the fan shroud. It is 30% lighter than its counterpart in aluminium. [FhG 07] More components made from fibre-reinforced materials are being developed for future generations of vehicles. Carbon-fibre reinforced plastic is already used in the BMW M3 CSL. Here, this material dramatically reduces the sports car’s weight – the M3 CSL weighs in at 1,385kg, a good 110 kilograms less than its series-production equivalent.


BASF is already working on the production of bodywork parts made completely of plastic, which no longer need painting. Coated or pigmented plastic films ensure that the plastic body parts are indistinguishable from steel panels. Take the Smart car, for example. Its roof is the first large exterior body part in which glass and plastic appear to merge into each other. Its plastic roof is half the weight of a comparable steel panel.

Studies assume that in 2010 every car will have a plastics content of 19% to 20%. Today, the figure already hovers around the 13% mark. One further option for lightweight construction is metal foam. Researchers at the Fraunhof Institute for Manufacturing Technology and Applied Materials Research in Bremen have discovered a process whereby a porous and yet hard foam structure can be made from metal powders. 

A kind of ‘metal yeast’, a special compound of metal and hydrogen, is critical for this procedure. It ensures that, when baked in an oven, the powder will swell like foam. The foaming agent must first be mixed with the metal powder and compacted in a press. The size and number of the pores will vary according to the amount of foaming agent used and the length of time of the reaction. In an extreme case, the structure consists of 90% air and 10% metal, e.g. aluminium. A ready-made lump of this material is lighter than water and can be sawn like wood. And just as easily, you can drive a nail into it. These metal foams can be used, for example, to save weight, whilst giving rigidity to structures used in automobile construction. One welcome side-effect is that, as a result of its cavities, cellular aluminium has very good insulation characteristics. Its sound-deadening qualities are five to eight times that of normal aluminium or steel.


PASSIVE SAFETY


 In Germany, there are more than 200,000 car accidents every year. Manufacturers are devoting technical resources to technologies aimed at affording better protection to drivers and passengers. Along with the construction design of the vehicle, the steel used for the bodywork also plays a central role. In an accident, enormous forces act on the car and its occupants. As the engine bay deforms, it absorbs a large part of the impact and thus protects the passengers in the passenger compartment. The bodywork must be able to deform and yet be rigid, two properties that are in fact mutually contradictory. Scientists at the Max Planck Institute for Iron Research in Düsseldorf have developed a new type of steel to serve both functions from a mixture of manganese, silicon, aluminium and iron. 

In a collision, this TWIP steel (Twinning Induced Plasticity) activates its expansion reserve and begins to deform. Each steel point deforms by a certain predefined amount only. It then stiffens again and distributes the remaining energy to the surrounding material. This spreads the energy over the entire surface of the metal. The impact forces are evenly distributed. In a few years, this new steel will be built into car wings and side doors. These are the areas most at risk of being hit in a collision.

Further examples of materials with ‘deformation intelligence’ are the TRIP (Transformation-induced Plasticity) steels developed some years ago, which become stiffer as the material deforms. Through the addition of alloys, energetically favoured crystal lattice structures are formed, which have an improved balance between stiffness and deformability.



ENGINE AND DRIVE TECHNOLOGY



 Manufacturers and engineers are pursuing various avenues of research to come up with the drive technology of the future. Whilst the trend in Europe is towards clean diesel engines that bear relatively little resemblance to traditional diesel technology, developers in the USA and Asia already see the hydrogen solution as a realistic prospect for the near future. 

The ecological credentials of this form of energy are, however, still questionable, since in its role as energy transfer medium it is itself a great consumer of energy.  During a transitional period, internal combustion technology could be combined with electrical technology to make ‘hybrid’ engines. The first models employing this technology are already on the market.  The aim is to make the motor car more economical. Following the failure of the German and indeed the whole of the European automotive industry to adhere to its self-imposed obligations over the last ten years, the European Parliament in early 2008 argued in favour of a maximum permissible emission level of 125g CO2 per kilometre with effect from 2015 instead of the 120g limit from 2012 proposed by the European Commission. [Web 08] In 1998, European car manufacturers had agreed to target an average emission level of 140g CO2 per kilometre by the end of 2008. By 2002, they had almost managed to achieve an average level of 160 grams but their efforts have stalled since then, mainly because of the increase in engine performance of European new models.

National governments are also aiming to curb both consumption and CO2 emissions. Since the beginning of 2008, purchasers of new vehicles in France have had to pay extra duty on cars that pump out more than 160 grams of CO2 per kilometre. This has pushed up the prices of models such as the Porsche 911, BMW 740i, Audi Q7 and Mercedes S-Class 420 CDI by around 2,600 euros, according to calculations by specialist consultants B&D Forecast. 

There is, however, a strong possibility that the EU will overrule this French decision as anti-competitive. [Cro 07b] In the USA, there are also moves to cut average consumption for new vehicles. By 2020, this is supposed to fall to 6.72 litres per 100km (35mpg). Up to now, the limit that applied was the one introduced in 1984 of 8.6 litres for saloon vehicles and 10.5 litres for off-road vehicles. Individual states, including California, would even like to set a limit of 6.39 litres by 2016 to apply not just as an average across a manufacturer’s annual range of models but to each individual vehicle. For the moment, however, this proposal has been overruled by Washington.


INTERNAL COMBUSTION ENGINE


 The rationale behind the internal combustion engine at the heart of every motor vehicle is its convenient use of liquid fuel that is easy to handle and has a high energy density. In addition to these advantages, there is a national and international infrastructure already in place, so that distances of 500 to 1000 kilometres can easily be covered. We tend to take all of this for granted until we start to compare alternative fuels such as natural gas or alternative technologies such as electrically powered engines. 


In these alternative scenarios, refuelling opportunities are scarce and involve circuitous journeys or recharging that lasts several hours and thus takes the vehicle off the road for an unacceptable length of time. Internal combustion technology is already highly advanced, yet still capable of further development. One significant indicator is the way that the diesel engine has become increasingly economical to run over the past few years, though in the long term, the automotive industry is eyeing up the potential of the ‘Diesotto’: a petrol engine that combines the benefits of the low-emission petrol (Otto) engine with the fuel economy of diesel. 

The performance of petrol engines has been enhanced by direct injection systems, such as the one first fitted in 2000 by VW to their Lupo FSI. They are a complex package in technical terms but nonetheless provide payback in the form of reduced fuel consumption on low throttle. Electromagnetically controlled fuel injectors have so far played a major role here. Combustion takes place either in the classic stoichiometric proportion – i.e. precisely the right quantity of air to burn the injected fuel – or in a lean burn process with surplus air so that all the fuel is burnt without residue. In the part-load operational range, lean burn allows increased efficiency with a corresponding reduction in fuel consumption, especially under routine operating conditions. 

However, it also presents two challenges: on the one hand, it is necessary to fit an additional NOx absorbing catalytic converter as the nitrogen oxides cannot be dealt with by the standard three-way catalytic converter; and on the other hand, the initial practice of wall-controlled injection did not really lead to the desired level of fuel economy because lean burn requires fuel stratified injection (FSI) for the air-fuel mix in the vicinity of the spark plug to be capable of ignition at all. Attention is now shifting towards spray-guided systems using ultra-fine atomisation, which, however, requires high pressures of around 200 bar. One such spray-guided system went into series production in 2006. 

However, this is based on complex and costly piezo technology. Researchers at Bosch and Siemens VDO are working to achieve high pressures with less complicated multi-hole fuel injectors. These would help direct fuel injection to make inroads into the mass market and to make engines more fuel economical on a broad front. [Bar 07] Direct injection is state-of-the-art with diesel engines: high injection pressures with correspondingly fine atomisation make for an efficient engine operating on lean burn – except when it is at full throttle. Here we are seeing a switch from pump-jet technology to ‘common rail’. 

Whereas with common-rail injection the feedline shared by all the cylinders is at a pressure of around 1500 bar, with pump-jet technology it is only the jet for each cylinder which raises it above 2000 bar. A disadvantage of pump-jet injection is that it is mechanically driven by the camshaft. This means that the injection intervals are fixed, resulting in less efficient operation at low speeds and reduced throttle. For this reason, major supplier Bosch withdrew from further development of diesel engines with pumpjet injection, and Volkswagen will discontinue production of cars fitted with this system in 2010. [Sch 07] Already in series production since 1997, common rail continues to dominate the market – from the 0.8-litre 30kW diesel engine of the Smart to the 6-litre 370kW Audi Q7. 

The number of injections per cycle is electronically controlled, for example up to eight times at 2000 bar in the case of piezo injectors. Magnetic valves go up to 1800 bar. The injection pressure of common rail injection systems will be increased up to 2400 bar by the year 2011; there are even systems with a top pressure of 3000 bar at the development stage and, in the long term, these could make catalytic converters or particle filters superfluous. 

[Win 08] It is only common-rail technology that will enable compliance with the strict exhaust emissions standards Euro 5 (from 2009) and Euro 6 (from 2014), as well as the American standard US07 Bin5. Together with the drastic reduction in the sulphur content of diesel fuel that has been in force in the USA since 2006, the diesel engine may at some future stage measure up to the petrol engine hybrid vehicles that are selling so well in the American market at the moment. Of the 16 million cars sold during 2006 in the USA, around 500,000 had diesel and 250,000 hybrid engines.


Along with injector technology, research is going on into lightweight materials such as ceramic valves and light alloys for engine manufacture with the aim of improving fuel economy. All-aluminium diesel engines are expensive to manufacture and are generally reserved for top-end models – with a few exceptions such as Honda’s 2.2-litre CTDi engine for their Accord and Civic models.

One further advance with the petrol engine has been the GCI (Gasoline Compression Ignition) process. Honda have already achieved ignition without spark plugs in a two-stroke motorbike engine; during the next few years, VW and Daimler would also like to extend this technology to the four-stroke engine. This involves the addition of up to 80% exhaust gases to the air intake. Once the level of compression necessary for selfignition has been reached, the mixture ignites throughout the whole combustion chamber simultaneously. 

The high exhaust gas content acts as a brake on the explosive process and thus avoids the generation of nitrogen oxides. Volkswagen have called this engine technology the ‘Combined Combustion System’; Mercedes have gone for the catchier name ‘Diesotto’. In both cases, we are witnessing the triumph of electronics over mechanics: the camshaft which has traditionally operated the inlet and outlet valves in a purely mechanical fashion has given way to electromechanical actuators that control each valve individually. This builds on the concept of variable valve operation, first introduced by BMW under the patented name of ‘Valvetronic’, whereby the valve lift can be varied by means of an actuator. 

With this totally camshaft-free engine, it is possible to shut down cylinders temporarily and to hold them in reserve for bursts of full throttle. The Diesotto provides adequate torque from low fuel consumption and is not as expensive to manufacture as a diesel engine. Volkswagen are additionally optimising their ‘Combined Combustion System’ to operate on synthetic fuels. [Nie 01] These developments show that the internal combustion engine still has plenty of potential for powering the car of the future. However, the steady work being done here goes on outside the spotlight currently being shone on to the rising star of the automotive world – the hybrid engine.


HYBRID-ELECTRIC POWERTRAIN



 Together with the continual improvement of combustion engine technology, the use of hybrid drive vehicles can contribute greatly to a reduction in fuel consumption and CO2 emissions. However, as regards driving performance and driving comfort, hybrid vehicles must have the same versatility and durability as conventional vehicles if they are to have a chance in the market place. The development of power train technologies for hybrid vehicles must address these criteria. The potential for innovation lies particularly in a significant reduction in fuel consumption, in further applied research into key components and in the safe interaction of the drive system as a whole. In order to gain rapid acceptance, the research results must be shown to be in step with actual practice and vehicles developed that are suitable for everyday use.


In recent years, automobile manufacturers around the world have developed cars that get their energy from an electric motor with a battery as well as from an engine driven by petrol, diesel or natural gas. The latest models of these hybrid cars have vastly improved batteries and other features that put their predecessors in the shade. These latest hybrid cars could in future be the vehicle of choice for motorists, not just in Japan and America but worldwide.

Their main advantage is that they are environmentally friendly due to their low levels of carbon dioxide emissions. At the same time, the driver does not have to recharge the batteries himself by plugging into the mains, as is the case with traditional electric vehicles. The energy for the battery comes from an internal combustion engine and from the regenerative braking system. In 1997, Japan’s biggest car manufacturer, the Toyota Motor Corporation, began to sell the first mass-produced hybrid car in Japan, the Toyota Prius, which since the year 2000 has also been marketed in Europe and North America. In 1999, the Honda Motor Corporation introduced the futuristic-looking two-seater Honda Insight. Subsequently, a hybrid version of the Civic was made available.

Together with its Lexus brand, Toyota sold a million hybrid drive units between 1997 and 2007, and Honda for their part over 100,000, mainly Honda Civic IMAs.


By combining petrol and electric motor, the Toyota Prius achieves an official fuel consumption of 4.3 litres per 100km, a respectable figure for a medium-sized vehicle. Big savings in consumption are made above all in stop-go city traffic, as here the regenerative braking system and highly efficient drive combination really come into their own. In this full hybrid concept, the drive is either from the petrol engine or from the electric motor, the power trains being linked together by a differential planetary gearbox and by a complex drive management system. This means that, over short distances and at low speeds, drive is possible using just the electric motor.

Electric motors work efficiently throughout the engine speed range and produce high torque on start-up. These factors are very much in their favour. In these respects, they are superior to the combustion engine. In addition, the electric motor works as a dynamo when braking or travelling downhill and charges the on-board battery so that the car does not need an external power source and the mechanical brake is largely redundant because of the electric brake. At present, only around half of the braking energy can be recovered, since the battery cannot store the energy thus generated quickly enough. Supercapacitors, which can be charged in seconds, can increase efficiency still further. The cylinder capacity of the petrol engine can be reduced, as its workload is shared with the electric motor (downsizing). Also, petrol engines in full hybrid vehicles can operate for the most part within an efficient range, as the engine’s output is distributed either to the drive train or to the generator.


The weak points of the full hybrid concept – and this also applies to the wholly electric-powered car – are the increased vehicle weight caused by the electrical motor plus batteries and the higher production costs. The success of the Prius may also stem from the fact that Toyota essentially designed the vehicle afresh as a hybrid, and by giving it, for example, a good aerodynamic shape, they latched onto other potential savings in costs that are not part and parcel of the power train system. For the first time in a mass-production vehicle, the air conditioning has an electric compressor that will work even when the engine is switched off. In other words, the Prius went into production as a special car, easily distinguishable from all other conventionally powered models. Had it been unsuccessful it would have been consigned to the history books. All other motor manufacturers, however, are focusing on adapted models, which are already on the market and which are not distinguishable simply by looking at them. Consequently, their owners do not get the ‘halo effect’ from being an innovator or early adopter; a Swiss marketing study has indeed shown that Prius owners are less interested in the potential for fuel savings than in the unique, modern technology. It is barely possible for other manufacturers to reproduce this customer feeling.

Whilst the full hybrid attracts the most attention, there are likewise diluted versions to be found on German roads. The production vehicle Honda Civic IMA is classified as a ‘mild hybrid’. Its electric motor is placed as a starter motor coupled to the crankshaft between the engine and automatic gearbox. Here too, braking energy is recovered, but drive using the electric motor alone is not possible – it works in tandem with the engine.

Since 2007 BMW have been pursuing the concept of the ‘micro hybrid’ in the 1 series. An automatic start-stop function comes into play when the driver declutches and puts the car into neutral. As soon as the clutch pedal is operated, the engine starts immediately. Alternator and starter motor have been replaced with a special starter generator from Bosch. Fuel can be saved, especially in city traffic, by switching off the engine when the vehicle is stationary. The alternator charges the battery with energy from braking. In full hybrid vehicles, by the way, the engine is switched off as the brakes are applied.

Whilst all varieties of hybrid drive are being manufactured in high volumes – and yet remain niche products – development continues with different emphases. European and American car manufacturers are working in collaboration to get their full and mild hybrid concept cars ready for volume production. Apart from the Japanese manufacturers, only Ford in America with its Ford Escape already have a hybrid vehicle in their lineup. Daimler, BMW and General Motors are working together, as are the suppliers ZF,and Continental. Bosch are doing research for VW, Audi and Porsche. The companies are trying to catch up and promote diesel drive combined with hybrid technology to satisfy the European market. The French PSA group would like to offer both the Citroen C4 as well as the Peugeot 308 as hybrid versions from 2010. Elsewhere, premium limousines such as the VW Touareg, Audi Q5, Mercedes GL, BMW X5 and Porsche Cayenne are also lined up for the "hybrid treatment". With these models, fuel consumption can be reduced from a high base level, a route previously taken only by Toyota with its premium brand Lexus.

Hybrid vehicles can seamlessly continue to use the existing infrastructure: they can use petrol or diesel and, contrary to initial stereotypes, do not need an external power source. And yet Toyota are planning to introduce, amongst other things, the next generation Prius as a ‘plug-in hybrid’ in 2010. Such plug-in hybrids continue to generate current from the engine and from regenerative braking, but as an option, they can be recharged from the mains as well, in order to be able to cover greater distances using just electrical power right from the outset. This is made possible by the development of new lithium-ion batteries which have a greater storage capacity. In the long term, it is even conceivable that plug-in hybrid cars could make sensible use of the nightly power station base load by tapping into inexpensive off-peak electricity.

In order to control the ever-increasing performance on board a hybrid vehicle, silicon carbide high-performance switches are currently being developed. The silicon technology currently employed needs a separate cooling circuit for the power electronics because they are sensitive to high temperatures. Silicon carbide technology can reduce the weight of hybrid vehicles.


ELECTRIC POWERTRAIN


 Besides hybrid technology, there has also been a renaissance of vehicles driven by electric power alone. This was already planned in the 90s, when zero-emissions regulations emerged in the American state of California. The need for such vehicles disappeared after the rules were relaxed. In the meantime, several electrically powered models are again being developed. The most prominent example is the roadster from Tesla Motors. With a top speed of 200km/h and an acceleration from 0 to 100km/h in 4 seconds plus a range of over 350km, this vehicle will not primarily appeal to buyers who have the environment at heart.

The idea of using an electric powertrain especially for sports cars is obvious, as electric motors can develop maximum torque on start-up. Neither manual nor automatic transmission is needed. Moreover, wheelmounted drive trains make possible four-wheel drive with variable transmission of power to each wheel. They are very efficient and take up little room.

More classic vehicle designs, such as the Chevrolet Volt from General Motors, are also to be offered with electric drive technology. In addition to the power socket connection, however, the Volt will have a small petrol engine on board, which can be used to recharge the lithium-ion battery during the journey. In this way, the petrol engine will always operate within its most efficient speed range.

The former CEO of the software giant SAP, Shai Agassi, is starting an ambitious project. He would like to build up an extensive network of 500,000 charging stations in Israel and Denmark, with some offering a direct battery exchange service. In 2011, Renault and its Japanese subsidiary Nissan are to commence series production of electric cars.

Electric motors are ahead of combustion engines as they have inherently good tractive power even at low speeds. So they make a good addition to combustion engines, which always suffer from a lack of efficiency except when they are working at optimum engine speeds. This raises the question, why aren’t there any all-electric powered vehicles on the market? The answer lies in the energy storage for the two different propulsion methods. With more than 10kWh/kg, the energy density of petrol and diesel is greater than the storage capacity of today’s batteries by a factor of 50 and more. Lithium-ion batteries attain a respectable 0.2kWh/kg, which is nonetheless still modest by comparison. Although the efficiency of combustion engines is not even half that of electric motors, this by no means outweighs the 50-fold difference in energy density between liquid fuels and batteries.

All types of rechargeable batteries are thus judged first and foremost by their energy density. Of secondary importance is the power density, which is critical for the car’s actual performance characteristics. However, it is not possible to set both energy and performance density to their highest values simultaneously. The lithium-ion batteries already mentioned achieve a power density of 0.8kW/kg. Supercapacitors with a power density of 10kW/kg make an interesting addition, even though they have a modest energy density of less than 0.01kW/kg. Since supercapacitors, unlike batteries, can be charged and discharged within seconds, they complement sluggish electrochemical batteries well and are particularly suited to the short-term storage of recovered braking energy.

All types of rechargeable batteries are thus judged first and foremost by their energy density. Of secondary importance is the power density, which is critical for the car’s actual performance characteristics. However, it is not possible to set both energy and performance density to their highest values simultaneously. The lithium-ion batteries already mentioned achieve a power density of 0.8kW/kg. Supercapacitors with a power density of 10kW/kg make an interesting addition, even though they have a modest energy density of less than 0.01kW/kg. Since supercapacitors, unlike batteries, can be charged and discharged within seconds, they complement sluggish electrochemical batteries well and are particularly suited to the short-term storage of recovered braking energy.


Nanostructure materials have the potential to improve the electrical characteristics of lithium-ion cells: examples are nanophosphate, nanoporous carbon as electrode material and nanostructured solid electrolytes. Ceramic membranes improve the temperature stability of the whole system and thus avoid problems that might arise from overheating of the cells due to powerful currents.

There is a further alternative suitable for use in motor vehicles: the sodium-nickel-chloride high-temperature battery. This works at temperatures of around 300°C, the electrodes being in liquid form. This temperature is achieved through the reaction heat of the cells and can be maintained for several days in thermally insulated containers. If the battery subsequently becomes too cold, then it has to be ‘reinitialised’ by an external current source. It has the dual advantage that there is absolutely no memory effect, meaning that the battery can be charged and discharged as required in any operating condition, and that energy management is non-critical, since cells in series do not behave individually. In addition, the operating temperature of the module makes it independent from external climate conditions. This is why sodium-nickel-chloride hightemperature batteries are particularly attractive for electric vehicles, despite their only average energy density (0.15 kWh/kg) and performance density (0.25 kW/kg): In London, a hundred electrically driven Smart cars are using the so-called ZEBRA (Zero Emission Batteries Research Activity) battery, and thus avoiding the city congestion charge.

Supercapacitors or ‘supercaps’ are especially adept in the rapid buffering of energy stores in highly dynamic systems. They get their ultra-high capacity from a dielectric only several atoms thick and from an extensive electrode material – it is possible to have a specific surface of over 1000m² per gram of electrode material. Here the focus is on new materials such as carbon aerogels and ceramics sintered from nanopowders of the nitrides and carbides of transition metals. All the same, these new materials are still expensive and require processing stages that are not yet fully understood. However, since the correlation between pore size of the electrode surface, choice of electrolyte and electrical characteristics is now known, the development of supercapacitors with an even higher capacity and modest performance density cannot be too far away.


AFTERWORD


The car of 2050 might be relatively easy to recognise, which might not be true for the phone or computer. This is because a car is a car is a car – it is supposed to transport people and goods and as long as people continue to be as tall as they are cars won’t look too much different. But the personal automobile as we know it will have much competition: from remote-controlled, on-demand pod and personalised public transportation. And in our livable cities, good old-fashioned walking and cycling, too.

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CREDIT FOR PICS
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[2]bbc.com
[3]youtube.com
[4]concept-supercars.com
[5]psipunk.com

CREDIT FOR AFTERWORD
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