T E C H N O L O G Y EMIS SIONS
LIFETIME CO 2 EMISSIONS IN DIFFERENT INDIAN VEHICLES There has been a lot of talk around green electric cars globally. Awareness about them is steadily growing in India too, especially amongst the environment-conscious patrons. This study by Altigreen Propulsion Labs focuses on understanding the truth about the lifetime CO2 emissions of different vehicles available in India.
AUTHOR
VISHESH MEHRA is Deputy Manager, Business Development at Altigreen Propulsion Labs in Bengaluru (India)
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INTRODUCTION
Most studies and analysis on automobile emissions are simply restricted to direct exhausts from the vehicle, without much consideration to the lifetime emissions. A vehicle’s lifecycle is often distributed into three phases – the first stage includes extraction, fabrication, transportation, manufacturing and assembly of materials. The second stage is the use phase, while the third constitutes the vehicle’s end-oflife stage.
In this study, lifetime emissions are split into three components – manufacturing emissions, indirect emissions and direct tailpipe emissions. For electric vehicles, a fourth component is added for transmission losses from the power plants to the use points. We have compared the net emissions across different vehicle categories, both within the same fuel technology as well as across different fuels. When EVs are introduced to the mix, the results get pretty interesting, and at times shocking. www.autotechreview.com
This study is limited to CO2 emission only, as generally this provides a reliable estimate for other kinds of emissions as well. We have used different private and public reports for arriving at our conclusions.
ventional fuel vehicles, we have used fuel parameters like density [3], [4], [7] and calorific value [4], [5], [6], [7] as well as the mileage for different Indian vehicles. For electric vehicles, the numbers have been calculated using the split of Indian electricity generation, according to the source of generation [8].
MANUFACTURING EMISSIONS
INDIRECT EMISSION
These fuel lifecycle emissions are also called WTT (Well-to-Tank) emissions and include emissions from transport, refining, purification and conversion from primary fuel to usable forms. For our study, we have taken these numbers on energy per gigajoule (GJ) basis [2], and then converted these to a per km basis for different vehicles. To come up with the numbers for conautotechreview
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DIRECT EMISSIONS
These are emissions from the vehicle exhausts. Numbers are based on actual tests done by the ARAI [9]. For EVs, these numbers are based on the range of EVs as well as the emissions from different kinds of power plants in India [8]. We have completed our analysis by using two performance numbers for EVs – 4.7 km/ kWh (as per EPA standards for Nissan Leaf) and 8 km/ kWh (as per reviews of Indian elec-
TRANSMISSION LOSSES
This number is taken into account only for EVs and compensates for the electricity lost while transmitting from the generation plant to the point of use. We have assumed transmission losses to be ~ 27 %, a number consistent with most world bodies.
RESULTS
Lifetime emissions for different petrol vehicles (based on their engine size and body size) are listed in ➊. In ➋, a com-
Petrol Vehicle Emissions
Vehicle Segment
Entry level hatchback (Less than 1000cc)
174
Premium hatchback (1000-1300cc)
216
Mid level sedan (1400-1600cc)
221
Entry level sedan (1200-1400cc)
232
0
50
100
150
200
250
Co2 Emissions (g/KM) Manufacturing
Indirect
Direct
➊ Types of carbon emissions by petrol vehicles of different segments Diesel Vehicle
Vehicle Segment
Depending on the expected lifetime of the vehicle in terms of kilometres driven, these numbers provide a rough estimate about the emissions during the manufacturing process of the vehicle. The manufacturing emissions for petrol vehicles are estimated to be around 4-7 kg CO2e/kg curb weight of vehicle. CO2e is the carbon dioxide equivalent. The manufacturing emission numbers used in this study for different categories of vehicles are listed below [1]: :: Petrol vehicles: 40 g CO2/ km :: Diesel vehicles: 20 g CO2/ km :: LPG vehicles: 40 g CO2/ km :: CNG vehicles: 40 g CO2/ km :: Electric vehicles: 70 g CO2/ km We have assumed a net lifetime of 200,000 km for petrol vehicles. The numbers are lesser for diesel vehicles because of their longer lifetime of around 500,000 km (use of diesel vehicles as taxis in India significantly increase their yearly usage). The manufacturing emissions for CNG and LPG vehicles are assumed to be same as that of petrol vehicles. As can be seen, the numbers are quite high for EVs. This is due to lesser lifetime in terms of kilometres driven as well as energy intensive manufacturing processes. Battery production (lithium-ion) alone contributes around 35 % to this number, with inverters and battery cooling system contributing around 16-18 % [1].
tric car users). The point to be noted is that these electric cars are comparable in size to an entry level hatchback (under 1,000 cc for conventional fuel types).
Entry level hatchback (< 1400cc)
297
Mid level sedan ( ~ 1400cc)
202
Premium sedan ( 1800-2000cc)
183
Mid level SUV (2400-2600cc)
181 0
50
100
150
200
250
300
350
Co2 Emissions (g/KM) Manufacturing
Indirect
Direct
➋ Types of carbon emissions by diesel vehicles of different segments
Vo lu m e 4 | Is su e 10
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T E C H N O L O G Y EMIS SIONS
Vehicle Segment
Comparison Across Fossil Fuel Technologies
CNG
178
LPG
171
DIESEL
petrol hatchback in India, the percentage of electricity generated from renewable source needs to grow by 200 % (for a performance level of 4.7 km/kwh) and over 100 % (for a performance level of 8 km/ kwh). Again, we have not taken into account any improvement in the efficiency of conventional vehicles, which might happen during this period.
202
PETROL
232
0
50
100
150
200
250
Co2 Emissions (g/KM) Manufacturing
Indirect
Direct
➌ Carbon emissions of various fossil fuels
Comparison Across Technologies 350
289
Co2 Emissions (g/KM)
300
250
199 200
174
171
183
180
180
178
150
Transmission 100
Direct Indirect
50
Manufacturing
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[1] [1] Hawkins T.; Singh B.; Majeau G.; Strømman A.: Comparative Environmental Life Cycle Assessment of Conventional and Electric Vehicles, Journal of Industrial Ecology, 2012. [2] Department for Environment Food & Rural Affairs, UK: 2013 Government GHG Conversion Factors for Company Reporting, UK, July 2013 [3] Central Pollution Control Board: Status of the vehicular pollution control program in India, India, 2010 [4] http://www.ces.iisc.ernet.in/energy/paper/alternative/calorific.html (Numbers from the Energy and Wetland Research group of IISC Bangalore) [5] http://www.acea.be/news/article/differences-between-diesel-and-petrol (European Automobile Manufacturers Association) [6] http://www.gailonline.com/final_site/faq. html#13 (GAIL India) [7] https://en.wikipedia.org/wiki/Liquefied_petroleum_gas [8] Ministry of Power (Government of India): CO 2 Baseline Database for the Indian Power Sector, New Delhi, India, December 2014 [9] The Automotive Research Association of India: Air Quality Monitoring Project- Indian Clean Air Programme (ICAP), ARAI Pune
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REFERENCES
Vehicle Type
➍ Types of carbon emissions across vehicle segments
parison for different kinds of diesel vehicles is shown. These numbers only take into account CO2 emissions and do not provide an indication about the quality of emissions (diesel expected to emit more particulate matter). In order to compare the emissions across different fuel types, we have chosen an entry level sedan and have analysed the numbers for different variants of the vehicle (petrol, diesel, LPG and CNG), ➌. As mentioned earlier, for stacking up EVs with conventional fuel technologies, we have used two different performance levels for the electric vehicles. ➍ shows the huge dependence of emissions from EVs on their performance numbers. EVs have a separate factor added for transmission losses.
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CONCLUSIONS
Our study found CNG-powered vehicles to be the least emitters, followed by LPG, diesel and then petrol. Electric vehicles actually emit a lot more than conventional petrol or diesel vehicles of the same category. Most of these emissions come from the electricity generation at the power plants, the majority of which are fuelled by fossil fuels, in the case of India. Emissions from electric vehicles are highly dependent on their mileage. There is a difference of almost 100 gCO2/ km between the two performance levels used for this study. Back calculating from the emissions, we have found out that for electric vehicles to emit lesser than an entry level
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