cars and fuels for tomorrow a comparative assessment

8/7/2019 Cars and Fuels for Tomorrow a Comparative Assessment

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Natura l ResourcesFORUMPERGAMON Natural Resources Forum 25 (2001) 109-120

www elsevier.codocatdnatresfor

Cars and fuels for tomorrow: a comparative assessmentMax h m a n , Lars J. Nilsson, Bengt Johansson

Uepurtment ofEnvironmenfal and Energy Systems Studies, Lund U niversity. Lund, weden.E-mail: [email protected](M.Ahman)

AbstractLight duty vehicles, i.e. passenger cars and light trucks, account for approximately half of global transportation energy

demand and, thus, a major share of carbon dioxide and other emissions from the transport sector. Energy consumption in thetransport sector is expected to grow in the future, especially in developing countries. Cars with alternative powertrains tointernal combustion engines (notably battery, hybrid and fuel-cell powertrains), in combination with potentially low carbonelectricity or alternative fuels (notably hydrogen and methanol), can reduce energy demand by at least 50%, and carbondioxide and regulated emissions much further. This article presents a comparative technical and economic assessment ofpromising future fuelhehicle combinations. There are several promising technologies but no obvious winners. However, theelectric drivetrain is a common denominator in the alternative powertrains and continued cost reductions are important fo rwidespread deployment in future vehicles. Development paths from current fossil fuel based systems to future carbon-neutralsupply systems appear to be jlexible and a gradual phasing-in of new powertrains and carbon-neutral jluid fuels or electricityis technically possible. Technology development drivers and vehicle manufacturers are found mainly in industrialised coun-tries, but developing countries represent a growing market and may have an increasingly important role in shaping the future.0 2001 United Nations. Published by Elsevier Science Ltd. All rights reserved.Keywords: Energy efficiency; Vehicles; A lternative fuels; Sustainable transport; Energy secunty

1. IntroductionMobility and transport play a central role in achieving

social and economic development goals in most countries.The growth of the transport sector has, however, alsoresulted in increasing negative impacts on the environment[such as emissions of hydrocarbons (HC), nitrogen oxides(NO,), particulate matter (PM), carbon monoxide (CO) andcarbon dioxide (CO,)], congestion and noise. A near totaldependence on oil makes the transportation sector vulner-able to fluctuations in the petroleum fuel market. Concernsfor energy security and environmental protection have beenthe main driving forces for research and development effortsinto new vehicle technology and new fuels, but economicrestrictions and market trends have so far, in most countries,hindered the introduction and diffusion of fundamentallynew vehicle technologies and alternative fuels.

While limited oil reserves have motivated the search foralternative fuels for many decitdes, it was the 1973 and 1979oil crises that focused the worlds attention on the issue ofoil dependence. In OECD countries, 97% of the transportsector uses petroleum-based fuels. This sector aloneaccounts for 54% of the OECDs overall oil use (Peake0165-0203/01/$20.000 2001 United Nations. Published by Elsevier Science IPtI: S0 65 0203 ( 0 0 ) 004 8-9

and Schipper, 1997). Light duty vehicles use 49% of thetotal transport energy demand, trucking uses another 30%,with the remaining 21% divided equally among air, rail andmaritime transport (World Energy Council, 1998).

North American, Western European and Pacific OECDcountries accounted for 64% of the total world energydemand for transport in 1995 (WEC, 1998). By 2020, thisfraction is expected to decrease to 5 3 % , with a growingshare taken up by non-OECD countries in Asia and thePacific (WEC, 1998). The major growth in energy demandfor transport is projected to come from developing countries(see, for example, Schafer and Victor, 1999).

The two oil crises brought about policy interventions inmost countries, either in the form of fuel taxes or raised fuelefficiency standards for vehicles, such as the corporate aver-age fuel economy (CAFE) standard in the United States,aimed at improving fuel economy. Considerable researchand development efforts were devoted to the developmentof, for example, electric vehicles and alcohol-based fuels.Studies into possible future scenarios conducted at the timeof the oil crises suggested that large-scale exploitation ofunconventional oil resources (e.g. tar sands and oil shales)and coal liquefaction technology would become necessary

,td. Al l righ ts reserved.


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I10 M. Ahman et ul. /N ut ur d Resources Forum 25 (2001) 109-120in 2030 to meet projected demand for liquid transportationfuels (International Institute for Applied Systems Analysis,1981).

In the mid-I980s, with the fall of oil prices, the focus oftransport energy policy shifted somewhat from security ofsupply and fuel economy to environmental concerns. Onemanifestation of this shift is the California Air ResourcesBoard (CARB) 1990 mandate for various low- and zero-emission vehicles in response to local air-quality concerns.The climate change issue was effectively put on the globalpolitical agenda at the I992 Earth Summit in Rio de Janeiroand has since received increased attention. The need toreduce greenhouse gas (GHG) emissions has promotedincreased efforts to develop low-carbon emitting transporta-tion systems, although policy initiatives have occurredmainly in response to industrial competitiveness and a desireto reduce dependence on petroleum fuels (Chapman, 1998).

In the last two to three decades, the automotive industryhas substantially reduced exhaust emissions in new vehiclesfor regulated pollutants, such as CO, HC, NO,, PM and lead,in response to progressively tighter environmental regula-tions. However, these gains have been partly offset byincreases in total transport demand. Thus, between 1970and 1997, freight and passenger transport doubled in Europe(European Conference of Ministers of Transport, 1999).Between 1980 and 1995, fuel intensity normalised to enginepower in new cars fell by approximately 40%, but newautomobile fuel economy remained roughly constant, asthe efficiency improvements were largely absorbed bymore powerful engines and heavier cars (Schipper andMarie-Lilliu, 1999; Greene and DeCicco, 2000).

Future transportation systems must be compatible withmultiple policy objectives, including reliability, safety,clean air, low-carbon emissions and affordable prices. Thus,increasingly stringent environmental regulations are to beexpected, as exemplified by the forthcoming TIER I1 require-ments issued by the US Environmental Protection Agency(EPA). The automotive industry must also meet consumerdemands and preferences for performance and comfort.

Priorities and needs vary between countries and regions. Inlow-income developing countries, affordable public transportis essential for increasing access to markets and otheramenities for the poor, not least women (World Bank, 1996;Swedish International Development Cooperation Agency,1999). Cities in rapidly motorising countries, notably MexicoCity and Bangkok, are among the most polluted i n the world,although vehicle ownership is significantly lower than inindustrialised countries (World Bank, 1996). Several coun-tries in the fast motorising regions in the developing world,e.g. Mexico, Brazil and Chile, have in recent years adoptedstricter emissions standards for new vehicles and establishedinspection and maintenance programmes for older vehicles, toprotect their fast deteriorating air quality (Faiz et al., 1996).Stricter emission standards, closer to standards used in certainindustrialised countries, will be necessary in developing coun-tries i n the future if air quality is to be improved. Reducing air

pollution is a goal for both industrialised and developing coun-tries, although in industrialised countries the focus is currentlyshifting towards COZ mitigation to a greater extent than indeveloping countries. A shift from todays internal combus-tion engine vehicles (ICEV) to a new generation of vehicles,including battery-powered electric vehicles (BPEV), hybridelectric vehicles (HEV) and fuel-cell electric vehicles(FCEV), in combination with low-carbon electricity andother fuels, can make a substantial contribution towards meet-ing these goals.

2. Framework for analysing future optionsThe need to reduce health and environmental impacts from

transportation is taken as a starting point for the analysispresented here. In particular, transport is an important sourceof air pollution through engine and evaporative emissions ofC02,CO, HC, NO.,, PM and lead. In addition, there are emis-sions from upstream vehicle manufacture and fuel supply.Other impacts include land use, noise, accidents, etc. Focus-ing here on vehicle emissions, including greenhouse gases,there are essentially six strategies for reducing emissions:

using demand management to reduce transportation needs(e.g. through regional and city planning and communica-tions technology);increasing the relative use of low-polluting transportmodes (e.g. rail vs road transport);increasing utilisation factors (i.e. number of passengers ortonnes of goods per vehicle);improving driving behaviour and vehicle maintenance;increasing the usage of more energy-efficient and low-using alternative fuels or electricity.polluting vehicles; and

These strategies are to some extent interdependent. Forexample, road planning measures, such as speed bumps androundabouts instead of crossings, influence driving beha-viour, reduce emissions, and improve safety (Ericsson,2000). The analysis presented in this article, as illustrated i nFig. 1, focuses on an assessment of energy-efficient and low-polluting future vehicles in combination with alternative fuelsand electricity as final energy, thus concentrating on the lasttwo strategies above.2. I. Anulysing future vehicles un d fuels

Several fuel-vehicle combinations are technically possible(see Fig. I ) . Options analysed should be comparable in termsof performance. A reasonable benchmark is to meet futuresafety requirements, noise limitations, and consumer prefer-ences in terms of speed, acceleration, size and comfort. Theprospect of meeting these requirements is important whenassessing the long-term potential for the different combina-tions of fuels and vehicles. Energy use and the associatedpotential greenhouse gas emissions are the critical factors


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M. Ahman et ul. /Nutura l Resources Forum 25 (20 01) 109-120 1 1 1

fuel production& distribution

-rimary electricity

idling, heating etc.Benefits ofregenerative braking

Fig. 1. Possible pathways f o r energy from primary resource to final end use.Note: solid lines represent analysed vehicle and fuel combinations. Dottedlines indicate combinations that are possible but not analysed here, forexam ple, feeding grid electricity to HE V an d FCEV.

from a resource, environmental and technology perspectiveand consequently at the centre of the analysis. Not only arehard technical measures important, such as performance,emissions, and efficiency, but it is also important to assessthe viability of implementation, which depends on factorssuch as cost effectiveness, development path, energy securityand other socio-economic aspects.

Fuel supply, from primary energy source to final energy,can be analysed with respect to energy conversion efficien-cies, technology development prospects, and resourceconstraints. For biomass, important features are high yieldsper hectare and low inputs of energy in cultivation andharvesting. Local environmental impact of biomass utilisa-tion, such as nutrient leakage, soil degradation, and erosion,are also important factors when assessing biomass options.Further, the fuel produced should be suitable for use inhighly efficient and low polluting powertrains.

When comparing BPEVs with other transportation tech-nologies, the environmental impact and cost of the electri-city supply can be calculated using current average powermix, current marginal power or similar mixes from anassumed future power system. To analyse the effect ofsignificant long-term changes in the system, i t is reasonableto use a marginal perspective and assume that the electricityconsumption, emissions and cost resulting from the use ofBPEVs are the difference in electricity demand, emissions

and cost between an electricity system which includessupply to electric vehicles and a system without this supply(Johansson and Mktensson, 2000). This does not, however,mean that each consumer should be responsible for emis-sions or cost from marginal production as the developmentof the electricity system depends not only on the introduc-tion of electric vehicles but on the increased use of otherelectric devices in society and the implementation of (or thereluctance to implement) energy efficiency technologies.

2.2. Energy eficiency an d emissionsVehicles produce a number of emissions, such as NO,,HC, CO and PM, which are regulated pollutants in most

countries due to their effect on air quality. C 0 2 emissionsare currently not regulated anywhere, in a strict sense. Theemissions of regulated pollutants are an important factorwhen assessing future fuel-vehicle combinations. PresentC 0 2emissions are inherently linked to the use of petrol andthus also become linked to the overall energy resourcepolicy. From a fueltvehicle technology perspective, energyefficiency is a key strategy for mitigating C 0 2emissions.

Energy efficiency can be analysed at three different levels:powertrain, vehicle, and primary energy efficiency (Fig. 2).

W, is the primary energy, WCis the energy supplied to thevehicle, WBis the energy supplied to the powertrain, and WAis the useful energy at the wheels.Powertrain efficiency Vpowenmin = WA/WBVehicle efficiency qvehicle = WAIWCPrimary energy efficiency qprimaryWA/W,

The powertrain efficiency is calculated from theefficiencies of the different components included in thepowertrain. To calculate the vehicle efficiency, the power-train efficiency is corrected for losses due to the powerrequired for heating and for the benefits when no energyis required during idling and the use of regenerative braking.The primary energy efficiency includes the energy used forenergy extraction, conversion, distribution and storage. Theenergy embodied in plants, buildings and vehicles was notincluded in the calculations for this article.

Most studies analysing the benefits of alternative power-trains have compared only one of the alternatives with the

IInergy system I Vehicle TIPowertrain

Losses due to:WD 4 WC 4 WE ,/Losses during: Losses from:I I I

Fig. 2. Definitions of primary energy efficiency, vehicle efficiency and drivetrain efficiency.


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I1 2 M . Ahman et al . /Na t ura l Re s ourc e s Forum 25 (2001) 109-120conventional powertrain. When comparing powertrainsusing the same energy carrier (petrol) there is no need toconsider the primary energy efficiency (see, for example,Cuddy and Wipke, 1997; Amann, 1998; comparing HEVswith ICEVs, focusing on fuel economy). When differentenergy carriers with different losses in fuel production anddistribution are used, analysing the energy losses all the wayfrom the well to the wheel becomes necessary (see, forexample, DeLuchi and Ogden, 1993; Ecotraffic, 1992;Wang and DeLuchi, 1992).

Further improvements in energy efficiency can also bemade by reducing road loads, in addition to increasingpowertrain efficiency. Road loads are comprised of approxi-mately one-third each of aerodynamic drag resistance (fric-tion from air proportional to speed squared), rollingresistance (friction between the wheels and the groundproportional to speed), and kinetic energy, being mainlyenergy losses from braking proportional to speed squaredand a function of the driving cycle (see, for example,Amann, 1998; DeCicco and Ross, 1993).2. 3. Co st effectiveness

When analysing the cost effectiveness of different technol-ogies within the transportation sector, life-cycle costs or costper passenger-km or cost per vehicle-km become relevantmeasures (Johansson, 1999). These indicators should prefer-ably include not only direct vehicle and fuel costs but alsoindirect costs, such as environmental costs. Furthermore,when designing environmental policies across differentsectors, it is important to relate the cost to the environmentalimpact of the strategy, for example, by using cost per unit ofCO? reduction as an indicator. If the measures have an impacton several environmental problems, methods have to be usedthat include all these impacts.2.4. Resource constraints and environmental risks

The risk of creating a new problem while solving anothershould be borne in mind. Large-scale use of a new technol-ogy may deplete resources not in demand today or createnew environmental problems caused by the circulation ofnew materials in the technosphere (Karlsson et al., 1996).The consequences of new flows of materials due to newtechnologies have to be analysed as well as the risksinvolved in depleting scarce resources.2.5. Development paths

The perceived potential for attaining specified goalsusually determines which technology is to be developed.For actors on a free market, future business opportunitiesare crucial, but for governments, other issues, such as globalenvironment, air quality, social equity and energy securityare equally important, calling for careful policy interven-tions to monitor development. Available development pathsneed to be thoroughly understood and evaluated, including

their consequences for policy and technology. In particular,the risk of lock-in effects and the consequences of path-dependence need to be taken into account (Cowan andHultin, 1996). New vehicles and fuels may eventuallyexclude other technologies, especially in terms of the choiceof fuel infrastructure. Technology flexibility will be impor-tant in order to meet and anticipate new knowledge, techni-cal breakthroughs and changing consumer preferences.2.6. Energy security

Security of supply has been the main driver in the searchfor alternative fuels, based on primary energy sources otherthan oil. Import dependence is a major issue, not least indeveloping countries, where oil imports as a share of exportearnings may be 20-40% or even higher (Rogner andPopescu, 2000). From the perspective of security of supply,new fuels should not rely on a single primary resource,especially if this resource is geographically concentrated,if it tends to increase import dependence, or if i t is sensitiveto environmental changes or other risks.

3. Primary energy sources and future conversion andvehicle technologies3.1. Primary energy and conversion technologies

The shift away from oil as the dominant primary resourcefor transportation fuels is not likely to be driven by resourceconstraints. A reserve to consumption ratio of about 45 yearsis often cited, but if the total resource base is taken intoaccount, including oil shale, tar sands and heavy crude oil,and divided by present consumption, the ratio is about 230years. Thus, occurrences of oil already known and underexploitation can cover the total global demand likely tooccur in the 21st century (Rogner, 2000). Although oil isthe primary resource for nearly all transportation fuelstoday, natural gas and coal can also be used. A shift awayfrom these fuels is not likely to be resource driven either. Thetotal resource base divided by present consumption is close to600years for gas and more than 2000 years for coal. Althoughthese potentials may be reduced by economic, security andenvironmental considerations, they start out at a high level.

Fossil fuels can be converted to attractive energy carriers(such as dimethyl ether, methane, methanol, hydrogen andelectricity) for future vehicles, facilitating near-zero or zerotailpipe emissions of regulated pollutants. In particular,near-zero emission of both regulated pollutants and green-house gases can be achieved with electricity and hydrogenas energy carriers i n BPEVs and FCEVs respectively.Although several uncertainties remain, i t is technicallypossible to recover and use the energy content of fossil-fuels while preventing carbon dioxide from being releasedinto the atmosphere. This can be done by separating out thecarbon dioxide and sequestering it, for example, in geo-logical formations or in the deep ocean (Williams, 2000).


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M. hman et a l . /Nat ura l Resources Forum 25 (2001) 109-120 I1 3Renewable energy sources supplied 1 - 16% of world

energy use in 1998. Traditional use of biomass, often ininefficient and polluting ways, account for about three-quar-ters of this total. The available flow of renewable energy isseveral thousand times greater than present global energyuse. It follows, therefore, that there is no primary resourceconstraint on increasing its use, although the potentials maybe constrained by competition over land use or environmen-tal, economic and other considerations. Modem renewableenergy technologies can convert these flows into attractivefu id fuels and electricity for transportation. Conversion ofsolar energy to electricity in photovoltaics and electrolysisof water to produce hydrogen is often advanced as a promis-ing option. However, producing hydrogen through electro-lysis of water using primary electricity from renewables (forexample, hydropower, wind, or solar), or nuclear power, islikely to be more expensive, at least in the foreseeablefuture, than making i t from fossil fuels, even with carbonsequestration (Williams, 2000). One reason is that electro-lysis and subsequent transport and storage involve consider-able conversion losses.

The most promising renewable source of primary energyfor fluid transportation fuels is biomass. The potential long-term contribution from biomass to world energy is high: onthe order of 300 exajoules per year, corresponding to 75%ofpresent global energy use or more (Rop er , 2000). Biomasscan be converted into electricity, and various liquid andgaseous hydrocarbons suitable for transportation. Biogas(i.e. methane from anaerobic digestion) from variousorganic wastes is a promising fuel, but it depends on theavailability of relatively limited waste streams since usingdedicated crops for biogas production is less efficient andless economical than pursuing other conversion routes. Lowor negative cost biomass in various waste streams are likelyto be used first, before more costly dedicated energy planta-tions arc widely used. In addition, cultivating perennialcellulosic energy crops typically results in lesser environ-mental impacts than annual crop cultivation, and may evenofler environmental benefits in terms of reducing nitrogenrun-off, etc (Borjesson, 1998).

In order to be competitive, biomass-based transportationfuels should be produced with efficient processes that use, asa feedstock, residues or biomass produced with high yieldsper hectare and low inputs of energy in cultivation andharvesting. Further, the fuel produced should be suitablefor use i n highly efficient and low polluting powertrains.

Esters from oil-rich plants, such as rape seed, typicallyhave less favourable energy balances (i.e. energy output asfuel divided by energy input in cultivation etc.) than otherbiomass-based fuels, partly due to the intensive farmingrequired (Johansson, 1996). In addition, the resulting fueloffers few advantages over diesel in terms of efficiency andemissions.

Ethanol from sugar-rich or starch-rich plants is a well-established technology, but thc economics and energy yieldsare not convincing, particularly in the case of typical starch-

rich plants suitable for temperate climates. Ethanol fromsugar cane in favourable climate conditions is more promis-ing, as illustrated by the Brazilian PRO-ALCOOLprogramme. Ethanol production from cellulosic biomass(e.g. wood) through hydrolysis techniques may also becomecost competitive in the future (Wyman et al., 1993). Ethanolwas not included as a potential fuel in this comparativeanalysis since it has no clear cost or efficiency advantagesover methanol; also it is less flexible i n terms of its primaryresource, and less suitable for use in FCEVs (Johansson,1996).

Thermal gasification offers a relatively high efficiencyconversion route from cellulosic biomass to methanol andhydrogen; fuels that can be used i n efficient and low-pollut-ing thermal engines or fuel cells. The gasification process isrelatively insensitive to the quality of the feedstock. Metha-nol and hydrogen are perhaps the most promising biomass-based fluid transportation fuels that can be considered andare the only ones included in the present analysis. In addi-tion, they can be produced from a variety of feedstocks,including fossil fuels, offering the advantage of flexibilityconcerning primary resource, thus facilitating a gradualphase-in process.3.2. Vehicle technology

Future powertrain technologies for BPEVs, HEVs andFCEVs are analysed for typical medium-size passengercars that, in principle, offer the same performance as presentconventional cars in terms of speed, acceleration, size andcomfort. An analysis of the potential future performance ofICEVs is included for comparison.

The common denominator for all alternative powertrainsstudied here is the electric drivetrain, consisting of an elec-tric motor and power electronics for control. The electricdrivetrain has attained the technical requirements for marketintroduction, but its cost remains a major barrier (Chan andChau, 1997; Xu, 1999). Cost targets for market introductiondiffer between US$11-2O/kW (Donitz, 1998; NationalResearch Council, 1999). Medium-term cost projectionssuggest large-scale production costs for currently advancedelectric drivetrain technology at US$20-25/kW (Delucchi,1999; NRC, 1999). The lower cost targets seem unrealisticunless technical breakthroughs make new production tech-nologies available (NRC, 1999).3.2.1 . Internal combustion engine vehicles (ICEV)

There are a number of possible options for improving themean efficiency in an ICEV, such as variable valve timing,shut off during idling, higher compression ratio, variabledisplacement and continuously variable transmission(DeCicco and Ross, 1993). HEVs with an IC-engine canalso benefit from most of these efficiency gains. The onlyoption not to be fully utilised in a HEV is variable compres-sion, targeted at improving efficiency at partial load. Most ofthe improvements listed above are well known technologies


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114 M . Ahman et al. / N a t u r a l Resources Forum 25 (2001) 109-120and could become available on the market with the nextgeneration of vehicles.3.2.2. Battery powered electric vehicle (B PE V)Th e BPEV consist of an electric drivetrain with a batteryas energy storage. One of the major advantages of the BPEVis that it produces no tailpipe emissions, as emissions areproduced at the power plant. The main barrier to introduc-tion of the BPEV is that the range attained with currentlyavailable batteries is too short and the price is too high forthis technology to be competitive on the market. Newbattery technology, e.g. lithium-ion, lithium metal-polymerand NiMH bat teries, could give the BPEV enough range,150 miles, for introduction on the m arket, but the qu estionremains whether batteries will reach the cost target ofUS$lSO/kWh (NR C, 1998a). Le ada cid bat teries are rela-tively cheap, but have poor energy storing capacity andcould provide an interim solution until long-term lithiumor NiM H batteries b ecome cost-co mpetitive . Future projec-tions for NiMH currently project a large-scale productioncost at US$200-250/kWh (Lipm an, 1999). Th e onlybatteries thought to have a possible long-term potentialbelow US$lSO/kWh are leadacid and l i thium metal-poly-mer batteries (Rand et al., 1998; S t Pierre et al., 1999), butthe realisation of this technology is highly uncertain. Large-scale use of BPE Vs would requ ire a new electric infrastruc-ture, such as home charging appliances and public fast-char-ging stations. The cost of this infrastruc ture could be high ,but it can be introduced gradually ; Californ ia Air Resourc esBoard (C ARB ) (2000) does not consider cost a major obsta-cle to an eventual large-scale BPEV deployment in Califor-nia. BPEV s may a lso be integrated into the electricity gridand used for load managem ent (Kempton, 199 7).3.2.3. Hybrid electric vehicle (HEV)In the HEV, an electric drivetrain and a battery arecombined with a generator, an internal combustion engine,IC-engine, and a fuel tank. The IC-engine charges thebattery, or takes ov er the drive from the electric drivetrainwhen the battery is discharged. The technology for HEVswith a dvanced and en ergy efficient TC-engines is availableon the market today, examples are Toyota Prius and HondaInsight.New IC -engines will have to manage both low emissionsand high efficiency which might, in the future, excludediesel engines as an al ternat ive (NRC, 2000). The actualcost of HEVs are not disclosed, but it is a fair assumptionthat the HEVs available on the market today are not yetprofitable for the companies producing them. Toyota claim sthat the company will make no loss at the end of the Priusproduction series, but admits initial losses of US$lS,OOO-20,000 per vehicle (Am stock, 1999). Th e HEV uses petrol,but can easily use methanol o r ethanol, and with som e effortalso hyd rogen. Th is fuel flexibility is a benefit as is the factthat the vehicle uses the same fuel infrastructure as theICEVs. However, large-scale use of methanol or ethanol

would require a partly new fuel infrastructure (Wang etal., 1997).3.2.4.Fuet-cell electric vehicle (FCEV)Th e main advantag e of the FCEV is its potential for high-energy efficiency and tailpipe em issions consisting on ly ofwater vapour. Th e most interesting fuel cell for automotiv epurposes is the proton exchang e membra ne (PEM ) fuel cell.Advances in recent years have made the PEM fuel cel ltechnically competitive; however, some further develop-ment is needed to integrate the system (Kalhammer et al.,1998). Serial production based on current state-of-the-artFCE Vs wil l begin at the earl iest in 2004 (D aimler-Chrysler,1999 ), but serial production of develop ed FCE Vs, fullyexploiting their potential, could probably not start until2010. An important barrier to FCEV development is thelong-term cost of the fuel cell itself. Cost projections forlong-term, large-scale production of the fuel-cell systemrange between US$50-300/kW (James et al., 1997; Kalham -mer et al . , 1998; Rogner, 1998; NRC , 2000). The fuel cel lstill needs considerable developm ent in order to bring cos tsdown to a competitive level of US$SO/kW (NRC, 1998a;Appleby, 1999). An important feature of the fuel-cellsystem is that it uses pure hydrogen for fuel, which requ iresa new fuel infrastructure and a complicated hydrogenstorage facility on board th e vehicle. In order to be ab le touse exist ing infrastructure and storage technology, a hydro-gen carrier, like methanol o r even petrol, can be reformedand used on board the vehicle instead. Using a hydrogencarrier lo wers the energy efficiency and add s to the weightand cost of the vehicle. So far, auto manufacturers preferreformin g methanol or petrol on board the vehicle instead ofusing hydrogen directly (see conclusions in Kalhammer etal., 1998). Petrol, methanol or natural gas can be used astransitional hydro gen carriers during the interim before ahydrogen infrastructure h as been establish ed.3.3. Energy ejicie ncy and emissions

Studies show that future vehicles can meet more stringen temission standards, such as Tier I1 (Egeback et al . , 1997;Energy and Environmental Analysis Inc., 1997). The stan-dard of the California zero-emission vehicle ( ZEV ) can onlybe met by BPEVs and FCEVs. It is reasonable to assumethat all vehicles studied here can meet future standards asexemplified by Tier 11, and therefore control l ing C 0 2emis-sions will be the key challenge to developing a sustainabletransportation system.3.3.1. Powertrain and vehicle ejiciencyPowertrain and vehicle efficiencies are given in Fig. 3.Th e battery driven powertrain re aches the highest efficiency.The two hybrid powertrains and the fuel-cell powertraindriven by metha nol have appro ximately the sam e efficiency.

See Ogden (1999) for a more elaborate discussion of this aspect.


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Fig. 3. Powertrain and vehicle efficiencies.Source: Derived from h m a n (1 999).

The fuel-cell powertrain is about 20% more efficient whenfuelled with pure hydrogen gas than with methanol. Further-more, there is considerable potential for improvement in theconventional powertrain.

There is only a minor difference between vehicle effi-ciency und powertrain efficiency (see Fig. 3) , but vehiclesusing electric drivetrains show a small relative advantagecornpared with vehicles using conventional powertrains, asthey incur no idling losses and benefit from regenerativebraking. A disadvantage for the electric drivetrain is theuse of electricity for accessories, e.g. interior heating, asvehicles using alternative powertrains can only partiallyutilise engine heat losses for this purpose. This aspect isincluded in the present evaluation.

3.3.2.Primary energy eficiericyPrimary energy efficiencies for energy carriers based on

fossil fuels are given in Fig. 4. The fossil fuels used areassumed to be crude oil or natural gas for fluid fuels andnatural gas for marginal electricity generation.Of the alternatives studied, the BPEV has the highestprimary energy efficiency i n the long term. The advan-tage with regard to the emission of COz is even higherdue to lower carbon contcnt per unit of energy fornatural gas compared to petrol. HEVs with advancedIC-engines are twice as efficient as the conventionalvehicles of today. FCEVs have lower efficiencies thanHEVs due to losses when converting natural gas tohydrogen or methanol.

The primary energy efficiencies for vehicles using energycarriers based on biomass tire given in Fig. 5. The BPEV hasthe highest potential for primary energy efficiency. Onereason for this, apart from the high BPEV efficiency, isthe conversion loss when producing liquid and gaseous

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-BFossil fuels7

Fig. 4. Primary energy efficiency from fossil fuels. BPEV fuelled withelectricity from natural ga s powerplant, HE V with ICE, FCEV with hydro-ge n derived from natural gas.Source: Derived from Ahman (1999).

fuels from biomass. The various HEVs and FCEVs allhave similar efficiencies.

Finally, the primary energy efficiencies for vehicles usingprimary electricity are given in Fig. 6. In this case onlyBPEVs and FCEVs were considered. Hydrogen for thefuel cell is produced through electrolysis of water. The effi-ciency of producing primary electricity is set to 100%for allthe alternatives.

About 30% of the energy is lost when converting elec-tricity to hydrogen and back to electricity again in theFCEV. For this reason, the most efficient alternativewould be to use the electricity directly in a BPEV. Hydrogenis, however, easier to store than electricity and may be amore practical energy carrier than electricity in a very long-term scenario, using hydrogen produced with solar energy.

Further efficiency improvements, not affecting the choiceof future fuel-vehicle combinations, can be achieved byreducing road loads. The principal strategies for this involvediminishing the vehicles frontal area and the use of aero-dynamic designs, slimmer wheels, and lighter vehicle over-all weight. Such measures can reduce road loads by roughly30-40% compared to standard ICEVs today, while main-taining overall comfort and vehicle performance, resultingin approximately the same reductions in fuel consumption(Ahman, 1999). Much larger reductions may be possible inthe longer term (Lovins, 1996).

3.4. Cost effectivenessAlternative fossil fuels, such as natural gas, are already

economically competitive to petrol and diesel today in citytraffic, if environmental costs are considered (Johansson,1999).The future cost of biofuels is principally governed by theprice of the feedstock (Pilo, 1996). The most competitive,


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Fig. 5 . Primary energy efficiency from biom ass. HEVs fuelled with metha-nol and FCEV s fuelled with hydrogen derived from biomass.Source: Derived from Ahman (1999).

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Primaryelectricity

Fig. 6. Primary energy efficiencies from primary electricity. FCEV fuelledwith hydrogen derived from electrolysis o f water.Source: Derived from Ahman (1999).

for most OECD countries, are cellulosic feedstocks (Reddyet al., 1997; International Energy Agency/Automotive FuelsInformation Service, 1999). However, in order for biomass-based fuels from cellulosic feedstocks to become reallycompetitive, an increased valuation of C02 emissions incombination with the development of more cost-effectivefuel production will be required (Johansson, 1999; Intema-tional Energy Agency/Automotive Fuels InformationService, 1999). In countries where biomass can be produced

at a lower cost, the cost-effectiveness of renewable fuels isgenerally better and other feedstocks can compete withcel ~ o s e .

Renewable electricity in BPEVs provides an opportunityto lower energy and environmental costs (Johansson andMhtensson, 2000), but the high battery cost is a majorbarrier. Even with major cost reductions, it seems very diffi-cult for BPEVs to compete economically with ICEVs orHEVs (Johansson and Ahman, 2000). The same goes forfossil-based electricity, since the difference in productioncosts between fossil fuel based electricity and renewableelectricity (a difference that continues to decrease) hasonly a minor effect on the life-cycle costs of BPEVs.Solar electricity has enormous global potential, but majorcost reductions are necessary for it to become competitive.The conversion of electricity to hydrogen causes both effi-ciency losses (Fig. 6) and extra costs. Solar hydrogen will,even with major cost reductions in all technologiesinvolved, be significantly more expensive than hydrogenor other fuels from biomass and fossil fuels (Ogden andNitsch, 1994; Grondalen, 1998).

It is assumed that alternative powertrains will only comeon the market if they meet commercial cost criteria. Citedcost targets for crucial components, such as fuel-cell- andelectric battery drivetrains, used in this analysis are mainlythose stated by PNGV' and USABC4 The commercialisa-tion targets are cost reductions considered necessary by automanufacturers and analysts in order to make market intro-duction possible. Long-term cost targets are based on life-cycle cost analysis considering that the higher purchaseprice is offset by a lower per mile energy price (NationalResearch Council (NRC), 1998b). However, the cost targetshave been criticised fo r not being ambitious enough, thusmaking further cost reductions necessary in order for alter-native vehicles to become fully competitive (Delucchi,1999).

Both HEVs and FCEVs will have lower energy andenvironmental costs than ICEVs, as their energy efficiencyis higher and emissions are lower. The value of these lowercosts is, however, not sufficient to allow for more than a fewpercent (less than 10%) increase in investment costs forsuch vehicles (Johansson and Ahman, 1999). Thus, costreductions are necessary for all alternative powertrainstoday. Maintenance costs and length of serviceable life areother important factors that affect life-cycle costs. Somestudies suggest that these factors will act to the advantageof HEVs, BPEVs and FCEVs (DeLuchi and Ogden, 1993).However, final conclusions regarding these effects are diffi-cult to draw at present since only a small number of alter-native powertrain vehicles are on the road in normal use.

' For production of ethanol from sugar cane in Brazil, see, for example,' PNG V: Partnership for a New Generation of Vehicles.' USABC: United States Advanced Battery Consortium.

Reddy et al. (1997).


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M . Ahman et al. /Na tura l Resources Forum 25 (2001) 109-120 1173.5. Resource constraints and environmental risks

Many of the components in alternative powertrainscontain rare or toxic metals. From this perspective, themost sensitive technologies are the batteries for BPEVsand the fuel cells. Lithium, leadacid or NiMH batteriesmay come into large-scale production if they meet targetedperformance; this would utilise large quantities of lithium,lead and nickel respectively. Fuel cells currently requirerelatively large amounts of platinum, which is a scarcemetal. However, if the metal intensities estimated for cost-competitive solutions are reached, then there seems to be nolong-term resource constraint for platinum for fuel cells(Ride, 2000) or for lithium and nickel for batteries (Rideand Anderson, in press).In thc mid-1990s there was a heated debate as to whetherlarge-scale introduction of BPEVs would cause environ-mental damage from circulating into the technospherelarge amounts of lead, assumed to be used in the leadacidbatteries (see, for example, Kellog, 1995; Lave et al., 1995;Socolow and Thomas, 1997). The problems with metal leak-age etc, seem to be manageable, but the debate has empha-sised the importance of recycling systems for large-scale useof metals (Socolow and Thomas, 1997). This issue has alsoreceived increased attention due to the high cost of scarcemetals.

3.6. Development pathsThe rationale for developing alternative powertrains isthe search for high energy efficiency, low or even zero

tailpipe emissions, and energy-resource flexibility. TheICEV does not have the same potential for high energyefficiency, but it can achieve very low tailpipe emissionsand it i s relatively flexible with respect to fuels. Futurecost reductions, and to some extent technical break-throughs (notably for the BPEV), will determine whetheralternative powertrains will become competitive with theICEV.

The buy-down of cost for the electric drivetrain, thecommon denominator for these alternative powertrains,through development and deployment, is the key factor tothe success of alternative vehicles. Currently, the leastcostly way of deploying the electric drivetrain is in HEVswith IC-engines. Major battery manufacturers today areshifting their focus away from BPEV batteries to HEVbatteries, as they see a greatcr and more immediate marketpotential (Anderman et al., 2000).For HEVs, leadkid battcries could be the lowest-costalternative, with NiMH, lithium-ion or lithium-polymerbatteries as long-term options. NiMH can fulfil the require-ments of an HEV, but it is not an attractive long-term optionfor a BPEV and has only smnll benefits over leadacid as anHEV battery in the medium term. However, leaaacid,NiMH o r lithium batteries may well fulfil the requirementsfor smaller sized BPEVs with limited range, e.g. neighbour-

hood electric vehicles (NEVs), which would provide a start-up market for batteries (CARB, 2000). The current HEVshave a relatively large IC-engine with a small batterybecause of high battery cost. As both batteries and electricdrivetrains become less expensive, the IC-engine can bereduced in size from 60 kW to optimally 20-35 kW; thiswould transfer more load variations to the electric drivetrainand thus increase vehicle efficiency.

HEVs with petrol or alcohol fuels can meet Califor-nias SULEV5 requirements (e.g. Honda Insight), butzero tail-pipe emission can only be met by BPEVs andFCEVs. If California and other states maintain the ZEV(zero-emission vehicle) mandate, this may force BPEVsor FCEVs onto the market. BPEVs have a somewhathigher overall primary energy efficiency than FCEVs,but the difference is small except when energy comesfrom primary electricity (Fig. 6 ) . It is uncertain whichtechnology will eventually have the greatest potentialfor market breakthrough. Both the FCEV and theBPEV need further research before wide-scale marketintroduction will be possible. It is thus reasonable tokeep the door open for both alternatives. For commercialcompetitiveness, the BPEV depends on a low-cost batterywith high specific energy. Developing such a batteryrequires further basic research. The only batteries thatat present seem likely are the lithium based ones, i nparticular the lithium-polymer battery. The FCEV is ina slightly different position. The PEM fuel cell isexpected to be technically competitive within a coupleof years, with a major challenge being cost reduction.The most transparent cost assessments suggest that it ispossible to reach a competitive cost, provided that criticaltechnical improvements or breakthroughs are made, suchas reducing the need for platinum.

The gradual shift from oil to renewable energy as a domi-nant source of fuel fo r transportation involves phasing innew fuels and new vehicles at the same time. Preferably,fuels should be flexible with respect to primary energysource and suitable for use in vehicles developed in boththe near and long terms, thereby avoiding lock-in effectsdetermined by fuel characteristics. Methanol and hydrogenare fuels that can be used in ICEVs and in many thermalengines for HEVs as well as in FCEVs.

The different powertrains will compete with each otherbut can also be seen as complementary, sharing criticalcomponents, on a trajectory towards new vehicles withhigh primary energy efficiency, low emissions and resourceand technological flexibility.

3.7. Energy security and socio-economic considerations.New vehicle fuels, or electricity, can be based on domestic

resources in many countries. Even if imported, they are lesslikely to suffer from the price volatility seen for oil-based

SULEV: Super Ultra Low Emission Vehicle.


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I18 M . Ahniun et al. /Na tur al Resources Forum 25 (2001 ) 109-120transportation fuels. Similarly, improvements in energy effi-ciency reduce dependence on imported oil. A viable domesticfuel industry can als o serve rural comm unities, and its devel-opment can thus be consistent with other social goals, asillustrated by the case of Brazil (Moreira, 2000). Countriesmay require different strategies, due to variations in geogra-phy, climate and other conditions. However, m ethanolh ydro-gen and electricity are relatively flexible energy carriers withrespect to the primary resource.

4. DiscussionCommunicat ions, mobil i ty and transport are central to

socio-economic development , faci l i tat ing the flow ofinformation, goods and people. New vehicle technolo-gies and al ternat ive fuels can help reduce emissions andenergy use, al thou gh they d o not offer a solut ion to themany non-technical problems facing the t ransportat ionsector. The importance and urgency of regional andci ty planning, public t ransport and other non-vehiclemeasures may be greater in developing countries,having less developed infrastructures, than in industria-l ised countries. Cars infringe on the qual i ty of othermodes of t ransportat ion, such as public t ransport andbicycles, by creat ing congest ion and pol lut ion andmay effect ively crowd out these opt ions. Nevertheless,car ownership is often seen as a token of high socialstatus, and thus at the top of the wish l ist as peoplemove up the income ladder, even i f the car ends up ingridlock.The main drivers (markets, regulat ion and other pol i-cies) and resources (technical and econom ic) for develop-ing new vehicle technologies are found in the industrial isedworld: notably, North America, Europe and Japan. Themanufactu rers are also based in these regions.Curren tly, new veh icle technology is develop ed mainly tomeet increasing demands of comfort, speed and accelera-tion. How ever, high oil prices and increasing enviro nmen talconcerns, together with strategic competitive thinking arepushing car manufacturers and governments in the US,Japan and EU to develop vehicles that use non-petroleumbased fuels, dramatically cut emissions and reduce energydemand. Alternative powertrains are able to achieve thiswhile maintaining vehicle size, speed, acceleration andcomfort. Most likely, alternative vehicles will cost morethan ICEVs and will therefore first be deployed in richcountries, rather than poor countries.In India, for example, the market share for domest i-cal ly produced two and three wheelers represents 65%of the total vehicle market (Faiz and Aloisi de Larderel ,1993). The si tuat ion is similar in many deve lopingcountries with a large share of various types of vehiclesbeing ei ther produced or assembled domest ical ly orregional ly at low cost for a mass market . The marketfor technical ly more advanced and low-pollut ing vehi-

cles is found mainly in urban areas, where purchasingpower is higher and air-qual i ty problems greater than inrural areas. Although much of the advanced technologymay be too cost ly for deployment in developing coun-tries, lower demands for range, speed and accelerat ionmay help speed the introduct ion of technologies such asthe electric drivetrain. Domest ical ly produced bat terypowered two- and three wheelers could thus replacehigh pol lut ing two-stroke engines.6 Policies aimed atreducing vehicle emissions could be l inked to industrialdevelopment , encouraging domest ic producers to adoptmore advanced technologies, thus increasing indigenouscapaci ty. Developing countries may leap-frog the devel-opment in industrial ised countries and avoid a depen-dence on diesel/petrol infrastructure by promotingal ternat ive fuels, e .g. alcohol or natural gas. Thesefuels may be used fi rst in buses, taxis, and other fleetvehicles.The projected growth in car ownership in developingcountries show s that these countries will con stitute increas-ingly important markets in the future. As a growing andpossibly strategically important market for several carmanufacturers and fuel distributors, developing countriescould formulate demands that will help shape technologiessuitable to their specific needs.

5. ConclusionsCombinat ions of new vehicle technologies and fuels, asanalysed here, represent a nexus of technical measu res thatcan reduce air pollution and energy use in the transportsector. Electricity or alternative fuels such as methanol orhydrogen, from either renewable or fossil sources, arepromising energy camers for future vehicles. Vehicleswith new pow ertrains using altern ative fuels can cut energ yuse in half and reach low or near-zero emissions of carbondioxid e and regulated pollutants. T he electric drivetrain is a

common denominator for hybrid, fuel-cel l , and bat terypowered electric vehicles, but substantial cost reductionsare needed for widespread deployment. It appears that aflexible transition with a gradual phase-in of new vehicletechnologies and al ternat ive fuels is technical ly possibleand, it seems, econom ically within reach . The main driversand early mark ets for new vehicle s and alternative fuels arefound in industrialised countries, wh ere supp liers are facingincreasingly tight regulations or other political incentives.Historical improvements in vehicle technology have beeninvested mainly in more powerful engines and bigger cars.Developing countries represent an increasing share of th emarket for vehicles and fu els, and this puts them in a posi-tion to exert increasing pressure on suppliers to offer tech-nical solutions that may better address their needs andpriorities.' Se e Moulton and Cohen (1998) for an example from Nepal.


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