EVS 24 Stavanger , Norway , May 13-16 , 2009 Full life cycle analysis of market penetration of electricity based vehicles

The main objective of the present study is to analyze the impact of the market share increase of different vehicle technologies in terms of energy consumption and CO2 emissions in the Portuguese mainland region. An extensive characterization of how road vehicle technologies energy consumption and CO2 emissions compare in a full life cycle perspective was attained. The main conclusions are that plug-in hybrid, electric and fuel cell vehicles can have the potential to reduced energy consumption (up to 9%) and CO2 emissions (up to 19%) in a full life cycle analysis.


Introduction
Portugal imports around 70% of its final energy consumption in the form of oil based fuels [1].Around 35% of this foreign oil consumption goes to the transportation sector, mainly road transportation.In terms of greenhouse gas (GHG) emissions, namely CO 2 , which are associated with climate change issues [2], the transportation sector was responsible for 21% of the total emissions, in 2005.Particularly, road transport accounted for 93% of the global emissions of the transport sector.The urge for energy security of supply, air quality improvement in urban areas and CO 2 emissions reduction are pressing decision makers/manufacturers to act on the road transportation sector, introducing more efficient vehicles on the market and spanning the energy sources.For that reason, it is expected in the near future that the market share of hybrid vehicles will raise and that, in the long term future, the market share of hybrid plug-in vehicles will be significant.Accordingly, this paper intends to exploit the benefits of introducing plug-in hybrid, electric vehicle and fuel cell technologies in the light-duty vehicle market for the Portuguese mainland region.In order to evaluate the environmental impacts of these options, a life-cycle approach was considered for the Portuguese fleet, covering the materials cradle-to-grave life-cycle (including vehicle assembling, maintenance, dismantling and recycling) and fuel life-cycle: Well-To-Tank (WTT) and Tank-To-Wheel (TTW).The materials life-cycle energy consumption and CO 2 emissions are spread along the vehicle expected lifetime (in this case around 12 years).WTT accounts for energy consumption and CO 2 emissions from primary energy resource extraction through the delivery of the fuel/energy source to the vehicle tank, while TTW accounts for the emissions and fuel consumption resulting from moving the vehicle through its drive cycle [3].Additionally, in order to assess the impact of the penetration of plug-in hybrid, electric vehicle and fuel cell technologies in the Portuguese light-duty vehicle fleet, three distinct scenarios with increasing substitution ratios were evaluated, in this life-cycle analysis framework.

Portuguese light-duty fleet characterization
The Portuguese fleet characterization in terms of diesel/gasoline distribution, weight and engine displacement vehicles' distribution is presented in Table 1 [4].To estimate the Portuguese fleet fuel consumption and derived emissions COPERT 4 [5] was used, which is an European tool for estimating the emissions and fuel consumption of specific fleets (with conventional vehicle technologies).A typical annual and daily mileage of respectively 12800 and 35 km was assumed [4].For COPERT a mix of urban (24 % of total distance), rural (57 % of total distance) and highway (19 % of total distance) driving was considered.The results obtained for the conventional fleet fuel consumption and annual emissions of carbon dioxide (CO 2 ), carbon monoxide (CO), hydrocarbons (HC), nitrogen oxides (NO x ) and particulate matter (PM) are presented in Table 2, according to the categories of vehicle considered.Table 2 shows the results of energy consumption for 2005 and emissions at vehicle usage stage (TTW).Summarizing, the light-duty conventional road transport sector consumes 167×10 3 TJ of fossil fuel energy and is responsible for a global annual CO 2 emission of 12×10 3 kton and for a local emission of 141 kton of CO, 20 kton of HC, 46 kton of NO x and 3 kton of PM.These vehicles have a total power-to-weight ratio of 55 W/kg since this is representative of the top sales of new vehicles sold in Portugal, with whom these new technologies will compete when they start entering the market.Additionally, it guarantees that similar vehicle performances are being compared.The designed scenarios for the electric, plug-in hybrid and fuel cell vehicles are the following: A real measured driving cycle was used, representing a mix of urban (24 % of km, speed below 50 km/h), rural (57 % of km, speed between 50 and 90 km/h), and highway (19 % of km, speed higher than 90 km/h) driving.Figure 1 shows the journey driving cycle [8], which corresponds to an experimentally measured real world driving cycle.

Fuel life cycle
In order to understand how road vehicle technologies energy consumption and CO 2 emissions compare, the fuel life cycle analysis and materials cradle-to-grave cycle was performed.The program ADVISOR [7] was used to simulate the fuel consumption and emissions of each vehicle in the specified driving cycle (see Figure 1).Table 4 shows the obtained results for the inuse emissions of HC, CO, NO x and PM, that are important regarding local air quality.Table 5 shows the in-use energy consumption and CO 2 emissions (Tank-to-Wheel part -TTW -of the fuel life cycle).For the fuels production and distribution stage part of its life cycle "Well-to-Tank" analysis WTT, a database [9] [10] was used for the calculation of the energy spent and CO 2 emissions for different fuels and different pathways.The fuel cycle has been defined as the energy spent to bring the fuel to the vehicle, not including the energy of the fuel itself.For each type of fuel a path was defined since its acquisition or production until it as available for use in the vehicles.The fuels used were gasoline, diesel, electricity and hydrogen from central natural gas reforming plants with steam co-generation.Table 4 shows results for complete fuel life cycle.Table 6 shows the materials life cycle ("cradle-tograve") results including tire, battery and fluids maintenance throughout 150000 km useful life.Figure 2 shows the combination of tank-to-wheel with well-to-tank for the fuel life cycle with the materials cradle-to-grave for selected vehicles.
For the total life cycle only the combustion of fossil fuels produces CO 2 (Figure 3).Otherwise, the more the vehicle travels the more the electric vehicles, fuel cell and plug-in hybrids gain relevance compared to conventional ones.Plug-in hybrids have the advantage of requiring a less complex infrastructure than hydrogen vehicles and of having higher autonomies than pure electric vehicles.

Fleet results
For the TTW stage, the Portuguese fleet's annual fuel consumption according to the vehicle type and the considered scenarios is presented in Table 7.As expected, the conventional fuels consumption decreases along the three scenarios (from 7% to 40%) while the hydrogen and electricity consumption increases.Global TTW energy consumption decreases from 4% to 29%.By analyzing Table 8, it is possible to conclude that the replacement of older vehicles by less polluting ones allows a significant reduction in terms of local pollution, with 11%-26% reductions for CO, 30-35% for HC, 15-17% for NO x and 17-60% for PM.After combining the materials cradle-to-grave with the fuel TTW and WTT, the following energy and CO 2 emissions distributions were obtained.A clear shift from the magnitude of TTW to the WTT results is observed with the increasing penetration of hydrogen and electricity based vehicles.Additionally, as the number of these vehicles increases the materials stage also gains importance, since fuel cell, plug-in and electrical vehicles manufacturing is more energy intensive.

Conclusions
An extensive full life cycle vehicle technologies study was performed.The main focus was the introduction of plug-in hybrid, electric and fuel cell vehicle technologies.These technologies have the potential to decrease the TTW energy consumption (4-29% in the considered scenarios).However, these technologies represent a new concept for the road transportation, since the energy and CO 2 are shifted to the WTT stage.In these vehicles' substitution scenarios, the WTT energy consumption increases (26-115%), as do the materials cradle to grave energy consumption (

For assessing the impact
of the different vehicles technologies on the light-duty fleet energy consumption and emissions, the following representative vehicles were considered [6]: • Plug-in hybrid (PH): Ni-MH battery of 6 kWh (dischargeable to 45% of its capacity), electric motor of 60 kW, internal combustion engine of 40 kW; generator of 40 kW and total weight of 1120 kg; • Medium size electric vehicle (EV1): Ni-MH battery of 12 kWh, electric motor of 65 kW, total weight 1214 kg; • Large size electric vehicle (EV2): Ni-MH battery of 24 kWh, electric motor of 75 kW, total weight 1393 kg; • Hybrid (FC-HEV) : fuel cell vehicle with a 75 kW electric motor, Li-ion 6 Ah 267 V battery, 50 kW fuel cell and a total weight of 1388 kg; • Plug-in hybrid (FC-PHEV): plug-in series hybrid with fuel cell.Fuel cell stack 50 kW, electric motor 75 kW, battery Ni-MH 45 Ah 335 V and a total weight of 1315 kg.

Figure 2 :
Figure 2: Full life cycle energy for selected vehicles.

Figure 3 :
Figure 3: Full life cycle CO 2 for selected vehicles.

Figure 4
Figure 4  analyses the influence of distance travelled on CO 2 emissions (and energy consumption).If the vehicle is always parked in the garage, than energy consumption and CO 2 emission are those of the vehicle manufacturing/recycling.If in its total life the vehicle travels distances below 50000 km, conventional ICE vehicles are good choices.Otherwise, the more the vehicle travels the more the electric vehicles, fuel cell and plug-in hybrids gain relevance compared to conventional ones.Plug-in hybrids have the advantage of requiring a less complex infrastructure than hydrogen vehicles and of having higher autonomies than pure electric vehicles.

Figure 4 :
Figure 4: Influence of the distance travelled on full life cycle CO 2 emissions per vehicle.

Figure 5 :
Figure 5: Annual fleet's life cycle results for materials, WTT and TTW regarding energy consumption in the considered scenarios.

Figure 6 :
Figure 6: Annual fleet's life cycle results for materials, WTT and TTW regarding CO 2 emissions in the considered scenarios.

Table 1 :
Fleet characterization in terms if fuel distribution and engine displacement.

Table 2 :
Annual TTW characterization for the Portuguese light duty fleet in terms of fuel consumption and emissions.
a in m 3 of liquid propane gas per 100 km.b gasoline equivalent.

Table 3 :
Designed scenarios for the penetration of fuel cell vehicles.

Table 4 :
In-use tailpipe emissions (local air quality).

Table 5 :
Fuel life cycle energy and CO 2 WTW.

Table 6 :
Materials energy and CO 2 cradle-to-grave.
5 to 23%).Combining the different stages, in the overall full life cycle analysis, these aggressive scenarios of new vehicle technology introduction, energy and CO 2 emissions reduction reach 9 and 19% respectively.Considering environmental impacts, introducing the considered vehicle technologies has a clear advantage in terms of local air quality (with up to 60% emission reductions of HC, CO, NO x and PM).In terms of global environment impact, CO 2 emissions can be reduced by up to 40% when running the vehicles, but this percentage is only 19% if a full cradle-to-grave analysis is accounted for.