汽车专业毕业设计翻译.doc

Seminar of the Assembly of European Regions on
Renewable and Alternative Sources of Energy,
1-2 July 2005, Porjus, Norrbotten (S)

WORKSHOP 3: CLEAN VEHICLE AND CITY CENTRE TRANSPORT SOLUTIONS

Interest in cleaner, less polluting vehicles and fuel has grown rapidly over recent years. This interest has been spurred by three factors:
* Increasing awareness and concern regarding the environmental effects of vehicle use
* The financial savings that vehicle operators can make by switching to cleaner vehicles
* Increasingly stringent emissions legislation.

Biomass is the only renewable source of transportation fuels. These renewable fuels, called biofuels, produce fewer emissions than petroleum fuels. The European Union is promoting the marketing of greener cars via a combination of binding and non-binding measures.

'Clean vehicles' include low emission conventionally fuelled vehicles as well as those powered by alternative fuels. The production of such vehicles, generating less CO2 emissions, requires innovation in fuels, alternative power-train technology, noise reduction and new materials. Overall, the European Union’s aim is to reach - by 2010 at the latest - an average CO2 emission figure of 120 g/km for all new passenger cars marketed in the Union.
Presentation of the most important technologies and fuels is given below.

Source: www.smile-europe.org

§ European car industry and future challenges

With 42% of global production coming from the EU in 2002, the region has the largest single market for passenger cars in the world and is well positioned to leverage economies of scale and scope. But one major challenge lies in the advantage Japanese car makers have gained in developing environmentally friendly technologies, “most prominently the development of new technologies/fuel combinations, including fuel cells” According to the Commission’s 2004 competitiveness report: Dutch Presidency: Results of the competitiveness Council – Competitiveness package and automative industry (nov 25th, 2004)
. As a consequence, the report notes, “R&D objectives in the automative industry should be directed towards developing environmentally friendly vehicles”, in particular finding the “adequate technology/fuel solutions” to ensure long-term security of supply.

§ Biofuels (I): market share and making process

- Biofuels currently represent around 0.3 percent only of diesel and gasoline consumption in the EU.
In May 2003, the Commission adopted a draft directive which requires Member States to take the necessary measures to increase the market share of biofuels. The Member States must ensure that the minimum share of biofuels sold on their markets is 2 per cent by 31 December 2005 at the latest, and 5.75 per cent by December 2010. Any Member State setting lower objectives will have to justify this on the basis of objective criteria. The Commission estimates that an effective implementation of the 2003 Biofuels Directive could save 19 million tonnes of oil by 2010.

- Technically speaking, biofuels can be prepared from plants according to two three major methods based either on the use of 1) glucides or cellulose or of 2) fats or of 3) any organic material .

In the first method, the starch contained in the tuber (beetroot, potato) or the seed (cereals) as well as the glucose contained in the sap (cane sugar) undergo various chemical processes – hydrolysis possibly and alcohol transformation. The main biofuels prepared using this method are ethanol and ethyl tertiary butyl ether (ETBE), which both can be mixed with petrol in a higher proportion than ethanol However – according to EU legislation, mixtures containing 5 – 30 % ethanol are prohibited. Higher and lower blends than this are allowed. (Directives 1998/70/EC, 2003/17/EG and 2003/30/EG). Researchers are investigating technologies for making ethanol from the cellulose (fiber) component in biomass, like municipal solid wastes and agricultural residues left in the field after harvest. A pilot plant is operating in Sweden since more than a year. Technically this is an excellent method, though still too expensive. This type of Ethanol made from organic feedstock is sometimes called bioethanol to distinguish it from ethanol made from oil. Bioethanol reduces exhaust emissions from carbon monoxide and hydrocarbons. In addition, by displacing gasoline components such as sulfur, bioethanol helps reduce the emissions of toxic effluents from automobiles. Most important is that bioethanol reduces emissions of climate gases (CO2) with 70 – 95 %, depending on production methods.

In the second method, vegetal oils from rape oil meal, or even from sunflower, which are mainly triglycerides, lead, after esterification, to diesters which are also used as biofuels. This is commonly known as biodiesel. Biodiesel reduces emissions of carbon monoxide, hydrocarbons and climate gases, but increases the emissions of particulates (PM10) and nitrogene oxide NOx dramatically. Particle filters can cure the particle emissions, but there is yet no commercially available method to reduce NOx. Hence biodiesel is best used in areas not suffering from other high NOx -emissions

In the third method, organic material like sewage from water treatment plants, restaurant waste, offals from slaughteries, surplus crops etc are fermented anaerobically to produce methane and carbon dioxide (CO2). This is currently commonly practised in most European cities. After taking the CO2 away (by e.g. water scrubber), this is called Biogas and is the cleanest fuel that is commercially available. Biogas emits almost no health hazardous or climate gases at all.

§ Biofuels (II): presentation of the various fuels and technologies

- Liquified Petroleum (LPG)

LPG is mostly propane and is used extensively where portable gas is required. It is produced during the oil refining process. LPG is a gas at room temperature and pressure, but is stored as a liquid under pressure both on-board vehicles and at depots. Apart form the fuel storage and delivery mechanisms, LPG engines are very similar to petrol engines, and deliver similar performance. In fact, most LPG vehicles are bi-fuel, allowing the driver to change from LPG to petrol and vice versa.
In motor vehicles, it addresses, to some extent, the problems of pollution as an alternative, mainly to petrol. Although it is not renewable and is still based on fossil fuels, LPG is claimed to be cleaner. For example, the UK government is encouraging its use by large tax concessions and subsidies for converting some petrol cars.

The Vauxhall Vectra Dualfuel

Source: www.clean-

- Natural gas

Apart from being a clean source of energy, natural gas offers the advantage of ensuring security of supply. It is approximately 92% methane, with the reminder being a mixture of nitrogen, ethane, propane and other gases. Natural gas, unlike LPG, does not liquefy easily, so is stored on board vehicles either in compressed or liquefied form. Hence it is an excellent engine fuel, but neither form of on-board fuel storage is as convenient as the storage of petrol or diesel. For this reason the majority of natural gas vehicles are heavy-duty trucks and buses, as larger and heavier fuel tanks pose less of a problem for these vehicles.
The 2003 Report of the high level experts on Alternative Fuels for the Commission comes to the conclusion that natural gas is the only alternative fuel with potential for significant market share well above 5% by 2020 which could potentially compete with conventional fuels in terms of the economics of supply in a mature market scenario. (They were not totally up-dated – see under Ethanol and Biogas) "Natural” gas could gain a broader market share if supported by long-term tax and excise duty advantages, providing stable conditions until a broad market has developed. Mature vehicle technology is available, but diversity of products and services still need to be improved," says the report. To support a broader commercialisation of natural gas vehicles at European level, the report recommends that codes and standards should be harmonised for the use of natural gas as a motor vehicle fuel. 

Biogas

Most of the characteristics for natural gas also applies for biogas. Technically biogas is the same gas as Natural gas – though renewable – and all vehicles that can use natural gas, can also use biogas.

Opposite to what is said above – both in Europe and globally there are much more light-duty vehicles in operation than Heavy-duty. Furthermore - all modern biogas/natural gas light-duty vehicles are dual-fuels, with one tank for gas and one for petrol, giving the possibility to drive also in areas where the fuelling infrastructure is not fully developed

Furthermore – produced in reasonable scale, biogas is economically competitive with diesel.

According to Swedish and Finnish studies biogas has the potential to substitute about 10 % of the current energy used for transport. Biogas is currently used as transport fuel in Sweden, France and Switzerland. Netherland and Polen are about to start within a few years.

Ethanol

Ethanol is the most common vehicle biofuel in the world – more than 6 million cars drive on ethanol today, most of them in Brazil and in USA.

As pure ethanol may give starting problems during cold conditions, 100 % ethanol is only used under controlled circumstances (e.g. in bus fleets) or in hot climates. Normally ethanol is blended with 15 % petrol to avoid this problem.

All ethanol cars can also run on petrol, or any mixture of ethanol and petrol, meaning that you can choose to fill your car with petrol if there is no ethanol station at hand.

According to The International Energy Agency IEA, Ethanol has the potential to substitute 10 % of the petrol and 3 % of the diesel by 2020. When the cellulose-based ethanol is economically viable, this potential increases dramatically.

- Battery electric vehicles

Battery electric vehicles produce no emissions themselves and are generally charged from the national grid via standard three pin sockets.
Several different battery technologies exist including lead-acid (now quite dated), nickel-cadmium, nickel-metal hydride, and lithium ion. Most electric vehicles today are Peugeots or Citroens, which use nickel-cadmium cells. With their limited ranges, battery vehicles are not appropriate to replace conventional vehicles for the majority of applications, but they are appropriate for certain niche markets such as urban delivery vehicles.

The electric think car

Source: www.clean-

- Hybrids

The term ‘hybrid’ usually refers to a vehicle that has both an electric motor and an internal combustion engine (ICE). These have traditionally been either ‘series hybrids’ in which the ICE acts as a generator producing electric current for the motor, or ‘parallel hybrids’ in which both the electric motor and the ICE can drive the wheels.
Both the Toyota Prius and the Honda Insight make use of innovative new hybrid technology and produce impressive fuel economy and emissions results.

The Toyota Prius

Source: www.clean-

- Hydrogen and Fuel cells

Hydrogen is a clean and storable energy vector that can be produced from a variety of primary energy sources (including fossil, renewable and nuclear). In September 2003, the Commission presented a Communication proposing the creation of a European Hydrogen and Fuel Cells Technology Partnership in order to promote hydrogen research in Europe. This is regarded as a potentially abundant alternative source of energy. The Commission launched the 'European Hydrogen Platform' in January 2004. Hygrogen's advocates claim that the 'hydrogen economy' would solve environmental problems (such as global warming and pollution) and secure independence of energy supply.
A fuel cell is a conversion device that combines hydrogen fuel and oxygen from the air to produce electricity, heat and water. It was invented way back in the 19th century but has not become popular in the mass market, partly because they are very expensive and the alternatives were more appropriate for their time. In addition they can be large, difficult to operate and the technology is complex. More research and development is needed but nevertheless they are currently being used in a small way. Now that the need for clean energy, with low or zero emission, is urgently recognised it is to be expected that fuel cells will become practical alternatives soon.

Fuel Cell Bus in Germany

Source: www.envocare.co.uk

§ Cleaner petrol and diesel

Emissions from petrol and diesel engines have been significantly reduced over the last ten years, driven mainly by European legislation, and will continue to be reduced in the future. Lower emissions from conventional fuels are achieved by a range of technologies including cleaner formulations of the fuels, after treatment technologies that remove pollutants from the vehicle emissions, and by improvements to fuel delivery and combustion processes.

Sources:
Dutch Presidency: Results of the competitiveness Council – Competitiveness package and automative industry (nov 25th, 2004)
Clean urban transport – results from the research Programme – European Commission – July 2001
www.clean-

FUEL CELLS
While there are different types of fuel cells, proton exchange membrane or "PEM" fuel cells are now used in most prototype fuel cell vehicles.   Each PEM fuel cell uses a thin  catalyst-coated membrane that is enclosed between graphite or ceramic plates.  One side of the membrane acts as an anode, and is exposed to hydrogen gas.  The other side of the membrane serves as the cathode, and is bathed in air to provide oxygen.  At the anode side, a catalytic reaction occurs, causing  the hydrogen to be separated into protons and electrons.  The protons diffuse through the membrane and reach the cathode.  The electrons, however, cannot pass through this membrane and go round the membrane to reach the cathode thus causing an electric current as they travel.  Once the electrons reach the cathode, another catalytic reaction takes place as the recombined hydrogen atoms join with oxygen to produce water.

Individual PEM fuel cells are assembled together to form fuel cell stacks which produce enough electricity to run a car, minivans, sport utility vehicles and transit buses.

Although, fuel cell vehicles emit only water, the source of the hydrogen as fuel can be less pollution free.

There are several methods of supplying hydrogen:  centrally located hydrogen production plants could distribute the hydrogen in liquid form to local fuel stations who could then dispense it to fuel cell vehicles capable of storing the hydrogen in either liquid or gaseous form in tanks on the vehicle.  (Liquid hydrogen mus