LCA에 기반한 전기차의 발전원별 환경효과 분석 = Analysis on environmental effects of electric vehicles for Korea electricity mix based on LCA

다국어 초록 (Multilingual Abstract)

In September 2017, the Korean government announced its New Comprehensive Plan on Fine Dust, which set the goal of seeing an accumulated two million eco-friendly vehicles on the road by 2022. Korea’s domestic market for electric cars is still in its infancy, with 15,247 units distributed so far as of June 2017. In keeping with the global trend of suppressing the sales of internal combustion vehicles and promoting the use of eco-friendly cars, Korea has also been implementing policies for strengthening its electric car market through subsidies and building necessary infrastructure such as electric car charging stations. Furthermore, as it is expected that electric vehicles will become more common in the future, more attention is being given to the changes in the electricity mix.
In Korea, coal-fired power generation and nuclear power generation are the primary sources of power. However, according to the country’s 8th Basic Plan for Electricity Supply and Demand, by 2030, Korea will be reducing its dependency on nuclear and coal-fired power plants to increase the ratio of new renewable energy to 20%. This goal to change the electricity mix makes it necessary to assess how such changes will affect the environmental impact of electric vehicles, which are expected to increase in number. This study, therefore, conducts the life cycle assessment of the environmental impact of electric vehicles from the viewpoint of Well to Wheel (WTW) based on the forecasts on electric car supply and the changes in the electricity mix. Also, we analyzed environmental impact of electronic vehicle compared with gasoline vehicle. Then we were confined to small gasoline cars as a comparison.
According to the previous studies on Korea’s domestic electric vehicles, 90% of the electric cars distributed so far were pure-electric vehicles, and the rest were plug-in hybrid vehicles (PHEV). The official fuel efficiency of pure-electric vehicles is 5.57km/kWh while that of PHEV is 5.43km/kWh, although the perceived fuel efficiencies are slightly higher. According to the life cycle assessments in existing literature, most electric vehicles are more environmentally friendly than internal combustion vehicles, but their specific environmental assessments differed greatly depending on the electricity mix. When the proportion of fossil fuel-based power generation such as coal-fired and petroleum power generation is higher, the level of pollutants emitted by electric vehicles during their life cycle was found to become similar to that of internal combustion vehicles.
In this study, TOTAL 5.0, the life cycle assessment software specifically designed for the environmental product declaration system, was used to evaluate the life cycle of electric vehicles. The inventories of fuels used by the vehicles and the energy sources were taken from on the national LCI database. Also, for comparison, the life cycle of gasoline vehicles were assessed using the petroleum production inventory of the national LCI database, and the amount of pollutants emitted while driving was estimated using the emission coefficient of the environmental product declaration and the Regulation on the Method for Calculating the Total Pollutant Emissions of Vehicles. The emission coefficient for calculating the particulate matter (PM 10, PM 2.5, etc., hereafter PM) produced by tire wear during driving was based on the GREET data. The environmental impact categories reviewed in this study covered the eight categories provided by the Ministry of Trade, Industry and Energy (MOTIE), with a focus on global warming, resource depletion, and acidification.
Analysis results showed that in the global warming category, electronic vehicles of bituminous coal-fired thermal power generation had the largest environmental impact, followed by gasoline vehicles and the electricity mix in 2017 (hereafter 2017 electricity mix). The large environmental impact of bituminous coal-fired thermal power generation was attributed to the CO₂ emitted to the atmosphere during the electricity production stage. On the other hand, the cause of the high environmental impact of gasoline vehicles was found in the exhaust gas emitted from the vehicles during driving rather than the fuel production stage.
The impact on resource depletion was found to be the highest for internal combustion vehicles, which can be attributed to the extraction of crude oil during the fuel production stage. In the case of acidification, the environmental impact of bituminous coal-fired thermal power generation was again the largest, followed by the 2017 electricity mix and the 2030 electricity mix. Here, the significant environmental impact of bituminous coal-fired power generation seems to be caused by the emission of SOx and NOx into the atmosphere during the power generation stage, and it was the high dependency on bituminous coal-fired thermal power generation that led to be high environmental impacts of the 2017 and 2030 electricity mixes. Another notable finding was that the amount of PM generated during driving was very small compared to the amount created during the power generation stage.
Assessment of the weighted impact of the eight environmental impact categories showed that the changes in the electricity mix would reduce the environmental impact in 2030 compared to 2017. Considering that bituminous coal-fired thermal power generation is the critical cause of degradation in many environmental impact categories, it is vital to reduce the proportion of coal-fired power generation and increase the amount of new renewable energy generation in the future.
The results of the analysis on the environmental impact of the PM produced from internal combustion and electric vehicles based on our data (Table 1) revealed a gasoline vehicle creates a total of 3.181 g/km of PM, among which 3..181 g/km of PM, among which 3.167 g/km (99.6%) is emitted during the fuel production stage. Meanwhile, the amount of PM produced by the electricity production stage was found to be greatest when the energy source used is 100% bituminous coal-fired thermal power, in which case 0.13 g/km of PM is produced in total, and 89% (0.115 g/km) of the PM is emitted during the power generation stage. When the energy source is the 2017 electricity mix, the total PM produced by an electric vehicle is 0.117 g/km, which is only 3.7% of that by an internal combustion engine.
The environmental impact caused by increasing of electronic cars and replacing gasoline cars with electric vehicles, using the changes in greenhouse gas (GHG) emissions as the indicator. Electric vehicles were found to emit 3.18 g/km of GHGs more than gasoline vehicles during the vehicle manufacturing and disposal stages. Also, assuming that the increase in electric vehicles will necessitate a 0.003% increase in electric power generation, this additional power generation will produce 0.0029 g/km of GHGs. When taken together, it became possible to predict a 61.7 g reduction in GHG emissions. This translates to a decrease of 7,024,452 tons of GHG emissions if one million electric vehicles are distributed and put into use by 2030, assuming 120,000 km of driving per each electric vehicle.
The measurements of greenhouse gas (GHG) emissions by energy source conducted in this study were compared to the results of previous studies (Table 3). There are some discrepancies between the results as the inventory used in this study reflects the data of domestic power generation facilities while those of previous studies are based on foreign cases (GREET, The Greenhouse Gases, Regulated Emissions, and Energy Use in Transportation Model of the United States), however, the levels of GHG emissions were largely similar. The GHG emissions of nuclear power plants and solar power generation measured in this study differ from those of previous studies because the present study takes into account the environmental impact during the construction of power generation facilities, while the GREET and MOTIE studies do not include the impact of the construction factor.
The GHG emissions of electric vehicles by energy source calculated by this study was compared with the findings of a previous study on Japan’s case (Table 4). The comparison showed that despite this study’s inclusion of the impacts during the facility construction stage, the GHG emissions from a 1km-drive were found to be lower than the case of Japan.
The 8th Basic Plan for Electricity Supply and Demand aims to reduce the share of coal-fired power generation in the electricity mix by 2030 to 36.1%. This is a significant decrease compared to the current share of thermal power generation (45.3%), but the 2030 target still places the highest dependency on thermal power generation. Thus, greater efforts are required to make the shift to a more environmentally-friendly electricity mix. Also, since the PM from indirect emission accounts for 72% of the total amount of PM generated, additional measures should be implemented to reduce the environmental impact of acidification at the power generation stage.