LIFE CYCLE ASSESSMENT OF ELECTRIC AND CONVENCIONAL CARS IN PORTUGAL

Transcription

1 Energy for Sustainability 2013 Sustainable Cities: Designing for People and the Planet Coimbra, 8 to 10 September, 2013 LIFE CYCLE ASSESSMENT OF ELECTRIC AND CONVENCIONAL CARS IN PORTUGAL Pedro Marques*, Rita Garcia and Fausto Freire ADAI-LAETA, Department of Mechanical Engineering University of Coimbra Polo II Campus, Rua Luís Reis Santos, Coimbra, Portugal pedro.marques@dem.uc.pt, rita.garcia@dem.uc.pt, fausto.freire@dem.uc.pt web: Keywords: Battery electric vehicles, electricity generation, environmental impacts, internal combustion engine vehicles. Abstract The displacement of conventional vehicles (gasoline and diesel) by electric vehicles stirs much scientific and public interest. Some studies assessed this displacement but most have focused only on energy and greenhouse gas (GHG) emissions, neglecting other environmental categories. Furthermore, the results of these studies can be contradictory and very dependent on vehicle characteristics (including the battery type), scenarios adopted and the electricity generation system. This paper presents a comparative environmental Life Cycle Assessment (LCA) of conventional and electric passenger cars for Portugal. This study aims at comparing 3 technologies for passenger cars: battery electric vehicle (BEV), gasoline and diesel conventional internal combustion engine vehicles (ICEV), assuming that each vehicle runs for km ( km/year). Four scenarios for the Portuguese electricity mix (2004, 2009, 2010, and 2011) were assessed in order to address recent changes. Life cycle impact assessment results for 5 impact categories (climate change (CC), ozone layer depletion (OLD), terrestrial acidification (TA), freshwater eutrophication (FET), marine eutrophication (MET)) are presented for the 3 passenger car technologies. In the years 2010 and 2011, BEV shows lower impacts than ICEVs in the categories: CC, OLD and TA, while for 2004, BEV had lower impacts only for OLD. In 2011 the reduction was: CC (21%), OLD (52%) and TA (7%). Concerning TA impacts, the results also show that the installation (in 2008) of desulfurization and denitrification systems in the Portuguese coal power plants was critical for electric vehicles to present lower impacts than conventional vehicles.

2 1. INTRODUCTION The displacement of conventional vehicles (gasoline and diesel) by electric vehicles stirs much scientific and public interest. Most of the studies addressing this issue have focused on energy and greenhouse gas (GHG) emissions only, neglecting other environmental categories (e.g. [1]Samaras and Meisterling 2008; [2]Stephan and Sullivan 2008; [3]Lucas et al. 2011; [4]Gao et al. 2012; [5]Ou et al. 2012; [6]Hawkins et al., 2012; [7]Freire and Marques, 2012;). The results of life-cycle (LC) studies of EV can be contradictory and very dependent on vehicle characteristics (including the battery type), scenarios adopted and the electricity generation system ([1]Samaras and Meisterling, 2008; [8]Frischknecht and Flury, 2011). This paper aims to present a comparative environmental life-cycle assessment (LCA) of conventional and battery electric vehicles for Portugal. LCA is a methodology for assessing the potential environmental impacts of a product system throughout its LC, which includes the extraction of raw materials, production, use and disposal phases (cradle-to-grave). LCA results can be used to identify environmentally preferable solutions and opportunities for improvement. In this paper, LC environmental assessment results were calculated using ReCiPe LC impact assessment (LCIA) method for five impact categories (climate change (CC), ozone layer depletion (OLD), terrestrial acidification (TA), freshwater eutrophication (FET), marine eutrophication (MET)). Four scenarios for the Portuguese electricity generation mix (2004, 2009, 2010, and 2011) based on [9] were assessed, in order to address recent changes in electricity generation technologies. 2. MODEL AND SCOPE The goal of this study is to provide a comparative LCA of a battery electric vehicle (BEV) and two conventional internal combustion engine vehicles (ICEVs) representatives of typical European passenger cars, including all relevant processes and a cross section of relevant impacts. A model of the vehicle LC, including the fuel LC (production and transport of raw materials, production and distribution of fuels and electricity, and fuel combustion in vehicle operation) and the vehicle LC (production of raw materials, manufacturing and distribution of vehicle components and assembly, maintenance and repair of the vehicle throughout its life time, and vehicle end-of-life) was developed, assuming that vehicles circulate in Portugal. The vehicle technologies considered are: gasoline internal combustion engine vehicle (gasoline); diesel internal combustion engine vehicle (diesel); and battery electric vehicle (BEV). The functional unit is km driven. Figure 1 shows the system boundary. A LC inventory (LCI) was compiled for this study based on [10]Spilmann et al. (2007). LCI data for the materials and processes in the background system were taken from the ecoinvent database v2.2 [11]. Battery inventories were adapted from [12]Notter et al. (2010). 2

3 Figure 1. System boundary of the life-cycle model. Table 1 shows the specifications of the three vehicles (BEV, gasoline and diesel). All vehicles were assumed to be compact family cars and the Volkswagen Golf was selected as a reference. The vehicles have similar dimensions but different weights. Similar material composition for the glider (chassis, car body parts, wheels, interiors, safety devices, acclimatization devices) for electric and conventional vehicle technologies was assumed since components are similar ([12]Notter et al., 2010; [1]Samaras and Meisterling, 2008). Based on these specifications, we assumed that the selected vehicles are built on a similar platform and that the differences are caused by different powertrain components. For the BEV, we assumed one battery pack replacement, i.e. a total of two battery packs (LiMn 2 O 4 ) during the 10-year vehicle lifetime. Table 1. Vehicle main characteristics. Car Technology BEV Gasoline Diesel Weight (battery incl.) [kg] Gasoline Diesel consumption [l/km] 0,052 0,045 Electricity consumption [Wh/km]* 188 * based in [13] Perujo & Ciuffo (2009) 3. RESULTS AND DISCUSSION This section presents and discusses the contribution of each LC stage to the selected environmental impact categories for the three vehicles (gasoline, diesel and BEV) and electricity generation mix scenarios. Figure 2 shows the LCIA results per total vehicle life ( km, left Y-axis) and per km (right Y-axis). For all scenarios analysed, the use phase was responsible for the majority of the impacts on CC, OLD, TA and MET, either directly or indirectly by fuel use or indirectly by electricity production. As can be seen, for CC and TA, the ranking of technologies depends on the electricity generation mix used to charge the BEV. When powered by the Portuguese electricity mix for year 2011, the BEV was found to reduce CC (by 26% compared to the gasoline and by 21% relatively to the diesel), OLD (by 55% compared to the gasoline and by 52% relatively to the diesel) and TA (by 7% compared to the gasoline and by 8% relatively to the diesel), assuming a vehicle lifetime of km. 3

4 Figure 2. LCIA results per total vehicle life ( km, left Y-axis) and per km (right Y-axis) The impact on CC of BEV production was estimated to be 31 g CO 2 eq/km, which is roughly twice the 16 g CO 2 eq/km associated with ICEV production. Battery production contributed about 30% to the impacts on CC from the BEV production phase and 10-15% to the total life cycle impact (2 battery packs). As can be seen, the BEV presented the lowest impacts in OLD, independently of the electricity mix. Moreover, the vehicle operation stage was responsible for the largest contribution to impacts in this category (BEV 70-76%, gasoline 94%, diesel 93%). For TA, the results show a high variation for BEV with slight lower impacts in 2010 and 2011 compared to ICEVs. From 2004 to 2009 mix, there was a significant reduction (52%) in the TA impacts of BEV due to electricity use, which mainly resulted from the installation (in 2008) of desulfurization (48% reduction) and denitrification (4% reduction) systems in the Portuguese coal power plants. In FET, the BEV presented significantly higher impacts (about 5 to 6 times higher) than the ICEVs for all electricity mix scenarios. This is mainly due to higher impacts (6 to 9 times) of vehicle operation in the BEV compared to the ICEVs. Additionally, BEV production had also higher impacts (4 times higher than the ICEVs), as a result of the production of batteries. For BEV, the vehicle production phase contributed more to the FET impacts than the vehicle operation phase (between 53-64%). Analogously to the FET results, the BEV presented higher MET impacts compared to ICEVs for all electricity mix scenarios. For 2010 and 2011 mix scenarios, the production of BEV (vehicle + 2 battery packs) had similar impacts to the use phase. ICEVs had lower MET impacts in the production phase than in the use phase. The gasoline was the vehicle which presented the best environmental performance in this category. 4. CONCLUSIONS A comparative environmental life cycle assessment of conventional and electric passenger cars for Portugal was presented. Five impact categories from the Recipe LCIA method were considered: Climate Change (CC); Ozone Layer Depletion (OLD); Terrestrial Acidification (AC); Freshwater Eutrophication (FET) and Marine Eutrophication (MET). Results showed that BEV passenger car can reduce life cycle impacts in CC, OLD and 4

5 TA, but the reduction in CC is extremely dependent on the generation electricity Portuguese mix. For TA, the desulfurization and denitrification systems installed in Portuguese power plants were critical to the reduction of impacts. For FET and MET, conventional vehicles presented the best environmental performance with higher benefits in FET. ACKNOWLEDGEMENTS The authors would like to thank Fundação para a Ciência e a Tecnologia (FCT) for support under the projects MIT/SET/0014/2009, MIT/MCA/0066/2009, and PTDC/SEN- TRA/117251/2010. Rita Garcia gratefully acknowledges financial support from FCT through grant SFRH/BD/51299/2010. This work has been framed under the Energy for Sustainability Initiative of the University of Coimbra and supported by the R&D Project EMSURE (CENTRO FEDER ). REFERENCES [1] Samaras C. and Meisterling K. (2008). Life cycle assessment of greenhouse gas emissions from plug-in hybrid vehicles: implications for policy. Environmental Science and Technology, 42(9), [2] Stephan C. H. and Sullivan J. (2008). Environmental and energy implications of plugin hybrid-electric vehicles. Environmental Science and Technology, 42(4), [3] Lucas A., Alexandra Silva C., and Costa Neto R. (2012). Life cycle analysis of energy supply infrastructure for conventional and electric vehicles. Energy Policy, 41, [4] Gao L. and Winfield Z. C. (2012). Life Cycle Assessment of Environmental and Economic Impacts of Advanced Vehicles. Energies, 5(3), [5] Ou X., Yan X., Zhang X. and Liu Z. (2012). Life-cycle analysis on energy consumption and GHG emission intensities of alternative vehicle fuels in China. Applied Energy, 90(1), [6] Hawkins T. R., Gausen O. M. and Strømman A. H. (2012). Environmental impacts of hybrid and electric vehicles a review. International Journal of Life Cycle Assessment, 17(8), [7] Freire F. and Marques P. (2012). Electric vehicles in Portugal: An integrated energy, greenhouse gas and cost life-cycle analysis. IEEE International Symposium on Sustainable Systems and Technology (ISSST), 6 pages. [8] Frischknecht, R., & Flury, K. (2011). Life cycle assessment of electric mobility: answers and challenges Zurich, April 6, International Journal of Life Cycle Assessment, 16(7), [9] REN (2013). Tecnical data. Available at: cos.aspx. Accessed 21 January [10] Spielmann M., Bauer C., Dones R. and Tuchschmid M. (2007) Transport Services. e- coinvent report No. 14. Swiss Centre for Life Cycle Inventories, Dübendorf. 5

6 [11] Ecoinvent Centre. (2010). ecoinvent data and reports v2.2. Dübendorf, Switzerland: Swiss Centre for Life Cycle Inventories. [12] Notter D. A., Gauch M., Widmer R., Wäger P., Stamp A., Zah R. and Althaus H. J. (2010). Contribution of Li-ion batteries to the environmental impact of electric vehicles. Environmental Science and Technology, 44(17), [13] Perujo A. and Cieffo B. (2009). Potential Impact of Electric Vehicles on the Electric Supply System. Commission Joint Research Centre, Institute for Environment and Sustainability. 6