混合动力汽车丰田普锐斯外文文献

ANALYSIS Does the hybrid Toyota Prius lead to rebound effects Analysis of size and number of cars previously owned by Swiss Prius buyers Peter de Haan Michel G Mueller Anja Peters Swiss Federal Institute of Technology Department of Environmental Sciences HES NSSI 8092 Zurich Switzerland Received 14 May 2005 received in revised form 4 August 2005 accepted 17 August 2005 Available online 5 October 2005 Abstract Hybrid powertrains are considered being a promising technology to decrease fuel consumption of passenger cars Sales numbers of hybrid cars are expected to rise considerably until 2010 However the introduction of more efficient products is often accompanied by rebound effects which counteract the positive effect of increased efficiency We investigate two kinds of direct rebound effects that could possibly occur when buying hybrid cars i people could tend to switch from small and or already fuel efficient cars to the new hybrid car and ii the average vehicle ownership could increase if the hybrid car is often purchased without disposing of an already owned vehicle A survey was conducted with all 367 buyers of the Toyota Prius 2 in Switzerland in the first nine months after market entry Returnratereached82 6 withoutsendingoutreminders Thesurvey basedapproachdoesnotallowustoinvestigatewhether hybriddriverswillinthefuturedrivemore theclassicalexampleofthedirectreboundeffect Detaileddataonthecarreplacedby the Prius and on the other cars owned by the household were collected Our analysis shows that average CO2 emissions dropped from 210 g km for the previously owned vehicles to 104 g for the Prius Empty vehicle weight curb weight increased by 9 kg only which isbelow the market trend A constant population averaged vehicle ownership still allows for a certain amount offirst timecarpurchasesandforincreasingvehicleownershipforindividualhouseholds astheseadditionalcarsarecompensatedforby other households disposing of a vehicle We present a new vehicle ownership model which assesses whether the vehicle transaction behavior of a sample of new car buyers corresponds on average to constant or increasing vehicle ownership It is based on disaggregated data from the Swiss travel behavior micro census Model results are consistent with market data and data from literature Model results show that if ca 20 of car purchases do not replace a vehicle for a population with an age distribution identical to Prius buyers this still allows for constant average household vehicle ownership Only 13 7 of the surveyed Prius buyers did not replace an old car Hence neither of the two rebound effects investigated could be found though the sample would have been large enough to do so vehicle size did not increase nor did average household vehicle ownership D 2005 Elsevier B V All rights reserved Keywords Hybrid cars Direct rebound effect Survey Fuel consumption Vehicle size Vehicle ownership Vehicle transaction Energy efficiency 0921 8009 see front matter D 2005 Elsevier B V All rights reserved doi 10 1016 j ecolecon 2005 08 009 Corresponding author Tel 41 44 632 49 78 fax 41 44 632 10 29 E mail address dehaan env ethz ch P de Haan Ecological Economics 58 2006 592 605 1 Introduction The increasing consumption of primary energy worldwide is of increasing concern because of the greenhouse effect of CO2 emissions and because con ventional oil and natural gas supplies are expected to decline in the not too distant future IEA and OECD 2003 This leads to greater interest in energy efficient technologies as technology still is the most important source for energy saving Berkhout et al 2000 Her ring 2006 The reshaping of existing patterns of energy consumption strongly affects the transportation sector which accounts for 21 8 of total primary energy consumption worldwide in 2000 and will account for ca 34 in 2050 OECD countries 28 1 and 40 respectively IEA and OECD 2003 Road transport is the second largest sector of energy consumption right after energy needed for HVAC heating ventilation air conditioning In the European Union EU emissions of green house gases from transport excluding international aviation and maritime shipping increased by 19 between 1990 and 2000 contributing a fifth of total greenhouse gas emissions in 2000 CO2 is the main contributor to transport greenhouse emissions 97 and road transport is in turn the largest contributor to these CO2 emissions 92 in 2000 The voluntary agreements of the car manufacturers with the EU commission to reduce average CO2 emissions from new cars help to slow the growth of car transport emissions in the EU EEA 2002 and technological progress is expected for future decades MacLean and Lave 2003 Still road transport and domestic avia tion are the fastest growing contributors to transport CO2 emissions with increases of 20 and 29 respectively between 1990 and 2000 For the near future hybrid powertrains are con sidered being a promising option to decrease fuel consumption of passenger cars Bitsche and Gutman 2004 The few hybrid car models currently avail able have increasing sales numbers and most large car manufacturers have announced hybrid cars for the coming years In 2004 8 vehicle models utiliz ing hybrid electric powertrains were on the U S market and had sales of 88 000 units 0 52 market share JDP LMC 2005 forecasts that by 2011 38 models will total to 535 000 sold units and 3 of U S sales Hybrid cars are an energy efficient technology however the introduction of more efficient products is often accompanied by rebound effects which counteract the positive effect of increased efficiency The definition identification and quantification of rebound effects are areas of ongoing research Green ing et al 2000 Grepperud and Rasmussen 2004 The rebound effect is also called take back effect or backfire effect Its definition varies among research ers but the common denominator is that if a product or service becomes more efficient regarding energy use or the use of some other resource it will also become cheaper which might give rise to increased demand Generally three different rebound effects might be induced Berkhout et al 2000 increased demand for the same service as it has become cheaper direct rebound effect increased demand for other services as money i e purchasing power has become available indirect rebound effect also called secondary rebound effect and structural effects on larger parts of the economy due to changed demand production and distribution patterns macro scale rebound effect also called economy wide rebound effect For example if the energy efficiency of a car is increased by technological innovations 100 km can be driven with less fuel and hence at a lower cost This lower cost could have the conse quence that people drive more and longer because mobility has become cheaper Identification of occur rence and if present quantification of rebound effects are generally not straightforward Most work has been done on the effects of the introduction of energy saving technologies e g space heating Haas and Biermayr 2000 Rebound effects induced by costs savings were the first to be investigated and originate in economics especially energy economics In close analogy also time savings and the reduction of socio psychological costs of ownership might be regarded as possible drivers for rebound effects As example for the latter it may well be not the financial but the socio psycho logical cost of ownership due to neighborhood pres sure norms of a peer group etc that prevents people from buying sport utility vehicles SUV However this could change as soon as SUVs with hybrid powertrain enter the market The present paper aims at identifying the occur rence and if present at quantifying direct rebound P de Haan et al Ecological Economics 58 2006 592 605593 effects accompanying the introduction of hybrid vehi cles Are hybrid cars which are an energy efficient technology effective as well We investigate two kinds of direct rebound effects that could possibly occur when buying hybrid cars i people could tend to switch from small and or already fuel efficient cars to the new hybrid car and ii average household vehicle ownership HVO could increase if people either tended to purchase the hybrid car as additional household vehicle without disposing of an already owned vehicle or because the availability of hybrid cars could make the decisive difference for a house hold to purchase a vehicle for the first time At present hybrid cars are more expensive than their conven tional counterparts but have lower fuel costs Driving factors for the rebound effects under investigation could be of both socio psychological and economic origin Whereas size and fuel efficiency of previously owned cars can easily be obtained and analyzed using survey data assessment of possible increases in average HVO is challenging A constant popula tion averaged HVO still allows for a certain amount of first time car purchases and for increasing vehicle ownership for individual households as these addi tional cars are compensatedfor by households decreasing their vehicle ownership reduction of car fleet after grown up children leave parental home or by elderly people due to health reasons etc We present a new vehicle ownership model which assesses whether the vehicle transaction behavior of a sample of new car buyers corresponds to a con stant or an increasing population averaged HVO The paper is structured as follows Section 2 pre sents research objective and hypotheses The study area purchasers of the second generation Toyota Prius in Switzerland in the first 9 months after market entry and the method chosen mail back survey are introduced in Section 3 Section 4 presents the results of the survey and investigates the presence of the first rebound effect mentioned above Section 5 introduces our household car ownership and car transaction model and investigates with its help the presence of the second rebound effect Section 6 discusses our findings in detail and Section 7 presents our conclud ing remarks with regard to rebound effects the effec tiveness of environmental policies promoting hybrid car ownership and consequences for future research 2 Rebound effects and purchase of new cars 2 1 Economic rebound effects When cars become more fuel efficient three levels of rebound effects can possibly occur direct indirect and macro level effects Berkhout et al 2000 Increased fuel efficiency means lower fuel costs and hence lower costs for transportation services Accord ing to the text book if the use of a car costs less people will use more car services They prefer the car to public transport drive longer trips or do not bother to switch off the idling engine when waiting for a train to cross the road This is called the direct rebound effect e g Binswanger 2001 which is if present always negative In addition the reduced fuel bill increases purchas ing power This leads to more expenditure for other commodities among which most also require energy use for construction and or operation This is called the indirect rebound effect It is often not possible to tell what other commodities show an increase Hert wich 2005 One solution is to assume an average linearrelationshipbetweenenergy intensityand money or between energy intensity and time Jalas 2002 The indirect or secondary rebound effect may be either positive or negative depending on the fact whether the service which has become cheaper more efficient previously had an above average or a below average energy intensity i e energy need per cost unit The third rebound effect could occur on a macro level It is also denoted as the economy wide rebound effect The shift of spending patterns of households and companies by the first order effects direct and indirect rebound effects leads to a shift of the sales pattern of the production sector a structure effect Grepperud and Rasmussen 2004 The structure effect has consequences for energy demand The net effect can be either positive or negative The direct rebound effect is computed simply as the difference between bcalculated savingsQ applying the ceteris paribus assumption i e the amount of services consumed does not increase and actual sav ings obtained through e g observation For example a direct rebound effect of 20 to 30 is reported in the case of more energy efficient space heating Haas and Biermayr 2000 It is more difficult to quantify the indirect rebound effect One possibility is the P de Haan et al Ecological Economics 58 2006 592 605594 approach adopted by Jalas 2002 By means of sta tistical regression a linear relationship between time and energy intensity is derived Any gains in time e g due to higher travel speed are then assumed to be invested in other activities with average energy intensity per time unit Using money instead of time and reduced costs instead of higher travel speed would be straightforward There is a risk of double counting when inconsistent definitions of rebound effects are compared with each other For example the so called indirect rebound effect as investigated by Jalas 2002 in fact is the sum of direct and indirect rebound as used in this paper which are based on Berkhout et al 2000 The macro level rebound effect can hardly be separated from other technologi cal trends and long term changes in the ratio of GDP to energy efficiency Birol and Keppler 2000 Schip per and Grubb 2000 Schipper et al 2001 Laitner 2000 through simulation obtained an estimate of 2 3 On the other hand Brookes 2000 and Saunders 2000 argue that it is likely that this effect does not exist Jaccard and Bataille 2000 also argue that because there is only a weak substitution between capital and energy macro scale rebound effects will also be relatively small 2 2 Socio psychological rebound effects The so called economic rebound effects presented in the preceding section are well known and accepted They are caused by reduction of monetary cost per service like driving a car for one kilometer for example as a result of improved energy efficiency Hertwich 2005 argues that even when price based rebound effects are not to be expected other effects might occur with either positive or negative sign For the present study we also regard what we call socio psychological rebound effects which can be present if the social cost and or the psychological cost attributed to the consumption of a given service is reduced For example in some neighborhoods especially in Europe owning a SUV with high fuel consumption might be accompanied by disapproval from neighbors family members or other peers which might prevent people from buying such vehicles With reversed signs driv ing a particularly fuel efficient vehicle will often go hand in hand with appraisal from part of the social network On the psychological side people might have norms or preferences benvironmental conscienceQ which prevent them from owning vehicles with high fuel consumption It would be possible to define in close analogy to economic rebound effects both direct and indirect socio psychological rebound effects Examples of direct effects would be to drive more frequently and longer with a more fuel efficient car and to purchase a fuel efficient car for example as second car for a household where otherwise no car would have been purchased at all An indirect effect would mean that people use up their social bcreditQ they earned by purchasing a fuel efficient vehicle by pursuing other hobbies which are disliked by public opinion or by the relevant social network like smoking wearing fur hunting heli skiing etc However we would like to leave indirect socio psychological rebound effects for future research by other scientists In the present paper we concentrate on the investigation of direct socio psychological rebound effects only It may seem fruitless at first sight to distinguish between economic and socio psychological rebound effects If somebody buys a new fuel efficient car and drives more than before how to tell whether this is done out of economic reasoning or because social sanctioning and or remorse have decreased But in the case of passenger cars with hybrid powertrain this distinction does make sense as hybrid cars are more expensive and will remain so in the future due to all additional technology needed for hybrid powertrains On the long run hybrid cars if they prove to be successful will have a surplus sales price correspond ing to the savings on fuel costs in the first say five years of car ownership So rationally speaking there is no room for economically justified rebound effects as costs per vehicle kilometer do not change They are only shifted from operation to investment costs So if a rebound effect is observed we argue that its origin is primarily of socio psychological nature 2 3 Research questions The present study aims at investigating whether two direct rebound effects are present and if so can be quantified Direct rebound effect number 1 DRE1 above trend increase in car size P de Haan et al Ecological Economics 58 2006 592 605595 Direct rebound effect number 2 DRE2 increase in average household car ownership Another possibly occurring direct rebound effect increased mileage is not the topic of the present study as a priori statements of car owners on the amount of kilometers they will drive are not reliable Investigation on the presence of DRE1 is straight forward We adopt empty vehicle weight curb weight as surrogate for bcar sizeQ Since roughly 20 years average empty vehicle weight of new car regis trations is increasing in Europe including Switzer land and Northern America A rebound effect can only be considered as present if an increase in empty vehicle weight defined as the weight of the Toyota Prius minus the average weight of the previously owned vehicles which are replaced by the Prius is higher than this general trend The Prius hybrid technology is responsible for some 170 kg of extra weight Using empty vehicle weight as a s