混合动力汽车、纯电动汽车及燃料电池毕业设计翻译原文.pdf

Which energy source for road transport in the future? A comparison of battery, hybrid and fuel cell vehicles J. Van Mierlo *, G. Maggetto, Ph. Lataire Department of Electrical Engineering and Energy Technology (ETEC), Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium Available online 23 March 2006 Abstract The hydrogen era is foreseen following the European research programme in a time horizon of 20202040. But there will be clearly a choice to be made between an electron economy (direct use of the produced electricity) and the so called hydrogen economy which leads to the introduction of an intermediate hydrogen production, transport and distribution process before the fi nal use in an electrical process. This paper considers only passenger car and delivery vans applications. In this fi eld a big time gap is to be fi lled between the situation today, the occurrence of oil shortage in a quite short future and this time horizon 20202040. Todays inter- mediate solutions are clearly based on hybrid electric vehicles and battery electric vehicles. The performances of these solu- tions are putting a lot of questions on the necessity of a hydrogen economy for future transportation. The paper discusses performances of hybrid electric vehicles and battery electric vehicles in comparison of the future hydrogen fuel cell based systems which are now in R Road transport; Battery electric vehicles; Hybrid electric vehicles; Fuel cell electric vehicles 1. Introduction The electric vehicle is an optimum solution for urban mobility as it emits no exhaust fumes. Particularly in cities and in adverse climatic conditions, traffi c-generated emissions are degrading air quality up to the point where the physical health of the population is directly threatened. Several cities have already had to apply repeatedly drastic traffi c restrictions. The electric vehicle is also ideally suited to be integrated into new traffi c management concepts, such as automatic rent-a-car systems and goods distribution centres, or small buses for city-centre services. 0196-8904/$ - see front matter ? 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.enconman.2006.02.004 * Corresponding author. Tel.: +32 2 629 28 04. E-mail addresses: Joeri.van.mierlovub.ac.be (J. Van Mierlo), gmaggetvub.ac.be (G. Maggetto), platairevub.ac.be (Ph. Lataire). Energy Conversion and Management 47 (2006) 27482760 For all these reasons, an increasing number of cities and environmentally concerned companies have intro- duced electric vehicles in their fl eets. Today, there is a clear necessity to generalise the support organised at the European level preparing so the step towards hydrogen electric vehicles. The oil crisis is clearly in an initial development step and is going to take dramatic dimensions 13 calling for an urgent introduction of alternative fuels for road transport with electricity playing a major role. How- ever the electricity, storage remains a key point. The development of alternative battery systems shows the pos- sibility of making a real technical and economic breakthrough in a short or medium term consistent with an important market development. New battery types such as high-temperature batteries, Nickel-metal hydride batteries, and lithium-based batteries are already on the market or will be available in the coming years. Due to their high energy density (70 W h/kg for NiMH and 125 W h/kg for Li compared to 40 W h/kg for Pb and 60 for NiCd 4), they will off er unprecedented vehicle ranges, up to 250 km and even much more through the introduction of range extenders. A powerful public national and European support is still necessary as well as an eff ective marketing approach. The long-range or multi-mission electrically driven vehicle will become a reality through the development of hybrid drive trains. Hybrid vehicles combine electric and other drive systems, such as internal combustion engines, gas turbines and fuel cells. The main advantage of this combination is the permanent interaction between the highly effi cient electric system and the thermal engine or fuel cell. Here too, the power batteries or other power boosters such as super capacitors play a key role. A number of reliable vehicles are coming on the market today with a large spectrum of hybridisation ratios (from start and stop systems to full hybrid power train). Due to the inbuilt dual function hybrid vehicles have a longer range than battery electric vehicles. They can off er the option of running on electricity alone in urban environments so being locally zero emission at this time. Some of these vehicles can be plugged-in using conventional or renewable sources of energy to produce electricity in an eff ective way. The hybrid technology is now particularly favoured for heavy-duty vehicles such as city-buses and leads to 2030% reduction in both energy consumption and associated emissions. Several studies have investigated the well-to-wheel energy consumption of vehicles using alternative fuels or drive trains 58. Several pathways to produce hydrogen and other fuels and to use it in several internal com- bustion engines, hybrid drive trains or fuel cell vehicles are compared in these studies. However a comparison with battery electric vehicles is mostly omitted in these studies. The objective of this paper is comparing the battery and hybrid electric vehicles with conventional vehicles and fuel cell electric vehicles on the basis of energy consumption. The duality between battery electric vehicle and fuel cell electric vehicle will be extensively demonstrated in the following sections. 2. Facts related with the mobility of people and goods Let us highlight some facts about the mobility of people and goods. 2.1. Employmenteconomy The European transport industry is an important economy sector as stated by the following data (for the 15 EU member states): 14 million workers or employees (i.e. 10% of the active population) where less than 6 mil- lion in the transport services, 2 million in the equipment sector and 6 million in transport connected activities. Fourteen percent (14%) of families revenue are devoted to transport. The modal distribution of the people mobility expressed in passenger kilometers (p.km) sounds as follows: 79% by car, 8% by bus, 7% by air, 6% by rail and less than 1% by tram or underground. The modal distribution of goods transport formulated in ton kilometers (ton.km) show a diff erent picture: 43% by road, 41% by sea, 9% by rail, 4% by land water- ways and 3% by pipelines. The total added value (EU15) of the automotive industry is around 290 BEuro. However there are also important external eff ects due to our mobility like pollution, congestion and safety. The total external cost is estimated to have the same order of magnitude as this added value, namely 225 BEuro. J. Van Mierlo et al. / Energy Conversion and Management 47 (2006) 274827602749 2.2. Growth The growth of the European transport is forecast as follows: between 1998 and 2010 a growth of passenger kilometers of 24% and good transport (ton.km) of 38%. The most important expansion in passenger transport is expected in air transport (90%) and for good transport in road transport (50%) 9. The growth of the number of cars worldwide is more worrying (see Fig. 1). At the 2030 horizon the number of road vehicles in the OECD countries (800 million vehicles) will be the same as in the rest of the world, which means doubling the todays worldwide vehicle number. This is also corresponding with a 65% growth in the OECD countries resulting from a 2% annual growth. 2.3. Energy The energy effi ciency of the diff erent transportation means is strongly varying as a result of thermodynamic laws, type of technology and power level. Knowing that the energy effi ciency of a car in the city falls below 15% does not worry anybody (but 80% of the cars are driven in the cities!) notwithstanding the fact that this means that from a 50 l fuel tank only 7.5 l are useful and the remaining 42.5 l are transformed in heat and pollutants. Among the todays fuels, diesel is the most effi cient followed by gasoline and the gaseous fuels (natural gas and LPG). For the evaluation of the energy consumption of any transport means caution is a must. Indeed an empty vehicle is wasteful and there is a clear necessity to evaluate its effi ciency with regard to its function i.e. moving people or goods. Taking the following fi lling rate as a reference: 35% for cars (1.4 person per vehicle), 40% up to 70% for trains, 60% for intercity buses and also 60% for national fl ights, the comparative results listed hereunder are obtained. This analysis is based on the well-to-wheel energy consumption for the trip between several German cities 12. For passenger transport (W h/passenger.kilometer): the train will use 15% up to 50% less primary energy than the car; the intercity bus, lighter than the train, will reach about 70% of the energy consumption of the latter and 42% of the car consumption; Fig. 1. Motor vehicle fl eet, OECD and the rest of the world, 19902030 10,11. 2750J. Van Mierlo et al. / Energy Conversion and Management 47 (2006) 27482760 the airplane will be at 60% of the car but at 300% of the fast train (not valid for high-speed trains); but for airplanes time plays an important economic role; in the city, the underground will easily have 50% consumption less than the car; For goods transportation mass and volume have to be considered (W h/ton.kilometer): the boat used for inland transport can reach 200% of the rail because of its diesel motorisation; rail transport will reach 4050% of the road transport consumption. Whichever transportation example is considered, it is necessary to take the energy consumption of all trans- portation means used between origin and destination into account. For the economic evaluation of a trip its duration will have a non-negligible importance. The above given data are only indicative as they are resulting from a number of typical trip. They are dem- onstrating the necessity to analyse the trips per category as well as the necessity to compare the potential energy benefi t of the diff erent transportation means. The benefi t coming from the rail (tram, underground) is the result of the combination of two important factors: the transport capacity and the use of electric energy thanks to the effi ciency of the electric drive system (power electronics and electric motor). The comparison is based on a well-to-wheel approach and hence includes the energy losses corresponding to electricity production and transport. Long distance transportation (more than 2000 km) is to be considered diff erently because of the choice of the transportation means in function of the object that has to be transported: 90% of the export trade of the EU (referring to the volume of goods) is performed by maritime transport which covers also 41% of the EU internal goods transportation. The use of energy by todays transport systems is far off ering the demonstration of a poorly effi cient use. 2.4. Evolution of the EU energy supply The energy dependence of the EU has evolved from 40% in 1990 down to 35% in 2000. This could reach 60% within 2030 years correspondin g with 80% for oil, 70% for natural gas and 50% for coal 13. Very recently oil companies have revised their oil reserve forecasting an end to cheap oil (or oil as energy source?) against 20302040. This is confi rmed by other independently published data. Referring to the IEA, see Fig. 2, a maximum of oil production could be reach within 1015 year naturally followed by a production decrease and a demand exceeding the off er. Fig. 2. Oil demand and supply. Source: Fossil fuel implications of climate change mitigation responses, Jonathan Pershing, International Energy Agency. J. Van Mierlo et al. / Energy Conversion and Management 47 (2006) 274827602751 Other forecasts indicate even shorter time delays. Consequently, price increase is to be expected together with geopolitics tensions. Even the exploitation of less accessible and or lower quality reserves will not clear up this situation. For natural gas the conditions prevailing are the same but with a somewhat longer delay (10 20 year). 2.5. Emissions The environmental state of the Earth is determined by the superposition of all local emissions. Some are controllable (transport, electricity production, industry, etc.), others totally not (volcanoes, radiance of sun, etc.). Limiting the contribution of transport to pollution can only be performed through local and regional actions, which success is strongly dependent of the awareness of the people concerned. The gradual introduction of the mandatory European emission standards, EURO I, EURO II, EURO III, EURO IV (2005) and EURO V (lorries and other heavy vehicles, 2008) leads to the control of the CO, NOx, hydrocarbons and particulate emissions. They will be reduced in the EU and in the other OECD countries despite the foreseeable increase of the automotive fl eet and covered distance. For the rest of the world an important increase by 45% up to 55% is expected for the diff erent pollutants. The emissions of the electricity production sector are clearly more and more under control which is a very positive situation for most of the public transport systems (trains, trams, underground, trolleybuses, and elec- tric mini- and midi buses). The case of CO2 is totally diff erent due to its proportional connection with the performed passenger.kilo- meter (p.km) for people mobility and ton.kilometer (ton.km) for goods transport. The effi ciency of the internal combustion engines (ICE) can still increase somewhat in the next ten years (but with costly investment), but one is nearing more and more its limits of improvement and consequently working more and more on asymp- totic values. Such situation is also valid for vehicle weight and shaping. In any case it is worth noting that the mean yearly emissions of cars is of 4 up to 5 tons CO2 corresponding with four to fi ve time the mass of a 1000 kg vehicle. The automotive industry (ACEA) has committed itself to reduce the CO2emissions from 190 g/km in 1995 to 120 g/km in 2012 in order to counterbalance the increase of the p.km. For Belgium an IFEU study (that could also be valid as a mean situation for the rest of the EU) is fore- casting an increase by 610% of the CO2emissions between 2000 and 2020 corresponding with an annual increase of 0.30.55% and resulting from the combination of better vehicle performances and an increase of the total number of driven kilometers 14. Between 1998 and 2010 an increase of +27% CO2emissions is foreseen in EU-15 9. In the EU, 28% of the emissions are transport bounded while it is forecast that 90% of the total emissions increase will have the same origin. Worldwide, the forecast increase is even more dramatic: not less than 110120%. The OECD mentions almost 4 billion ton CO2from motor vehicle operation in 1990 and 8 billion ton in 2020 10. 3. Technical evolution of land transport means (excluding lorries) Two important factors infl uencing the future transport means technology are the access to energy and the state of environment 1517. 3.1. A short analysis of propulsion technology The energy chain of a conventional vehicle is composed of a fuel tank (gasoline, diesel or gas), an ICE (elec- tronically controlled), a transmission (also electronically controlled), a diff erential, the wheels. A coupling decoupling system is needed to allow stops or suffi cient torque while starting or changing gear. The energy chain of a battery electric vehicle is composed of a battery, a power electronic converter, an electric motor (or wheel motors), a diff erential and the wheels. A fuel cell system (hydrogen tank or on-board hydrogen production unit feeding a fuel cell) replacing the battery, is in this case a possible future alternative solution. No couplingdecoupling system is needed and maximum torque is developed at starting. 2752J. Van Mierlo et al. / Energy Conversion and Management 47 (2006) 27482760 Energy recovery while braking is a major feature of these electrically driven systems. Furthermore the pres- ence of a battery means the necessity to use an on-board or off -board battery charger. The association of ICEs and electric motors leads to the hybrid systems for which four basic structures are listed hereafter: The series hybrid has only an electric propulsion system (power electronic converter, electric motor(s), dif- ferential, wheels) electrically fed by one two or three sources parallel connected (see Fig. 3). In the thermal series hybrid one of the sources is composed of a fuel tank (diesel, gasoline, and gas), an ICE or gas turbine driving an alternator, a power electronic converter (indicated as charger in Fig. 3). Parallel connected on this source, a battery (and or a power unit like a fl ywheel system or super capacitor) is delivering power while accelerating the vehicle and can also recover the braking energy. When none of these units is pres- ent we have the structure commonly named diesel-electric. The Engine-generator in this confi guration can also be replaced by a fuel cell system. In this case we have a fuel cell hybrid drive train. The parallel hybrid system combines electric traction and ICE traction (see Fig. 4). The system fuel tank- ICE is combining its mechanical output energy with the mechanical energy provided by the battery-power electronic converter-electric motor system both being mechanically coupled at the level of the transmission to drive the wheels. Energy recovery while braking is also a major feature of these systems. The start-stop and the mild hybrid systems are currently not designed for regenerative braking. Combining the series hybrid structure with the parallel structure leads to the so-ca