Background Essay Peer Review
2
How “Green” Are the Electric Cars？
How “Green” Are the Electric Cars？
Introduction
With the development of battery technology, electric cars have been developed as a solution to the energy and environmental crisis. Because electric cars do not consume fossil fuels, they enjoy great benefits compared to the traditional combustion engine automobiles. However, few are aware of the fact that the production and disposal of batteries can also lead to environmental pollution. The essay presents the context of the electric cars as well as the environmental influences of electric cars.
Historical Background of Electric Cars
Fossil fuel is a type of unsustainable energy source that plays a crucial role in human society. According to Shafiee & Topal (2009)’s prediction, in 2009, the reserve depletion time for oil, coal, and gas are 35, 108 and 37 years respectively (p.181). At the same time, automobiles consume large amounts of gasoline or petrol, direct products of crude oil. Because of the incomplete combustion of gas, automobiles release atmospheric pollutants such as CO and NOx. Together with heavy oil consumption, fuel engine cars have placed significant pressure on the environment.
Everyday life practicability of most electric cars was created by certain key battery technologies, such as modern lithium-ion battery technology. With the development of fuel cell technology, electric cars are developed as a solution to environmental problems and energy crisis. First, electric cars do not directly consumer fossil fuel energy. Moreover, as electric cars do not use petrol as the energy source, they do not release residue to the environment. Also, the electric cars also have higher energy transformation ratio. As Kaleg, Hapid & Kurnia (2015) introduced, comparing to the internal combustion engine, which has a maximum energy efficiency of 38%, electric cars can take advantage of 80% of the energy provided by the batteries (p.446). However, these environmental benefits do not mean that electric cars are 100% green. The possible environmental impact may be generated by the production and disposal process of electric car batteries.
As Chen and Sun (2005) introduced, the four kinds of new energy cars include battery electric vehicle (BEV), hybrid electric vehicle (HEV), Plug-in Hybrid Electric Vehicle (PHEV) and fuel cell electric vehicle (FCEV) (p.24). Secondary batteries such as lithium-ion battery, lead-acid battery, nickel-metal hydride battery, and nickel-cadmium battery generate energy for BEVs and power their electric engine. Since internal combustion engines are entirely replaced by electric motors and motor controllers, BEVs do not emit any pollutant at all. By contrast, HEVs use both an internal combustion engine and electric engine. PHEVs adopt a similar system with an extra external charging capacity. The internal combustion engines either generate electricity directly for the electric engine or recharge the car batteries for HEVs and PHEVs (Chen & Sun, 2005, p.26). PHEVs and HEVs are considered transitional creations for their partial reliance on gasoline and their emission of pollutants into the environment. The third type of electric car is FECV, which uses a fuel cell or a combination of fuel cells to power the electric motor. Energy for fuel cells is generated by combining compressed hydrogen and oxygen, which only emit water and vapor.
The Environmental Benefits of Electric Cars
Due to the characteristics of electric cars, their environmental benefits mainly lie on three aspects, including the reduced consumption fossil fuel, an improvement in energy transportation ratio and a cut on the exhaust.
First, All-electric cars such as BEVs and FECV do not use fossil fuel to generate energy. Compares to traditional cars driven by internal combustion engines (ICE), HEVs and PHEVs still consume much less fuel due to their use of batteries. Argonne National Lab calculated the reduction of crude oil consumption by electric vehicles. The results ranged from 51% to 71%. As road transportation accounts a large proportion of oil consumption, it imposes a considerable environmental burden. For example, in the EU, 47.5% of the total oil is consumed by road transportation (Mu and Zhou, 2008, p.66). Switching to electric cars can significantly reduce the consumption of fossil fuel.
Second, the energy transformation ratio is significantly higher in electric cars. To the largest, the energy transformation ratio for ICE cars is about 38% (Kaleg, Hapid & Kurnia, 2015, p.446). The average transformation ratio is between 17% to 21% (Sun, 2006, p.45). However, the energy efficiency of an electric motor ranges from 80% to 90%, which means that most of the electricity provided to the motor will be put into efficient work (Sun, 2006, p.45). A higher transformation ratio indicates less waste of energy, which is of great benefit to the environment.
Third, electric cars emit much less pollutant to the environment. The ICE powered vehicles account the main source of atmospheric pollution. The exhaust caused by gas-powered cars includes HC, CO, CO2, SO2, NOx, and PM. By contrast, BEVs and FCEVs do not emit any greenhouse gasses. Since HEVs and PHEVs only partially rely on fossil fuel, their emission is also much lower. According to Mu and Zhou (2008), electric vehicles cut greenhouse gas emission by 40% to 100% (p.67). Therefore, electric vehicles can be seen as powerful tools to reduce the greenhouse effect and other atmospheric pollution.
The Environmental Issues Raised by Electricity Generation
However, electric cars are not entirely ‘green’ as well. There is an environmental burden derived from the generation of electricity. There are three factors that influence the environmental aspects of electricity generation for electric cars, which include the pollution generated in producing electricity, the intensification of the peak-valley gap and the increase in load on the national power grid.
Although electricity is cleaner as an energy source than fossil fuels, its cleanness is heavily determined by the means to generate electricity. The dirty energy sources for producing electricity include oil, natural gas, and coal whereas the renewable sources range from hydropower, wind, solar power and nuclear power. However, as most of the electricity in the U.S. is generated by natural gas and coal (Fig.2.), while using electricity as the energy source, electric vehicles can be “more detrimental to the environment” than ICE cars due to the pollution caused by electricity generation ("Electric cars can harm the environment", 2017). As Cao (2011) identified with the electricity produced by coal power plants, electric vehicles can cause 3.6 times of air pollution compares to driving ICE cars (p.2).
Moreover, while a great number of electric vehicles enter the power grid, they can impose a significant load on the energy grid. Because users generally recharge their cars at various locations with different lengths of time, there is a high degree of unpredictability in EV charging. The unpredictability is demonstrated by the nonlinear pattern on power grid loads. Suffering from nonlinear loads, electric devices would produce harmonic waves that have an impact on the quality of electricity (Niitsoo et. Al, 2015).
On the other hand, with electric vehicle users charge their cars at an undetermined time and location, the peak load also sees a dramatic increase. As Fig.3. indicates, with 50% of ICE cars replaced by electric cars, the peak load can increase by 30% in Australia. Similarly, in Germany, it is estimated that 42 million conventional cars will be replaced by electric vehicles in 2030, which will double the peak loads (Bora Önen & Umurkan, 2017, p.255). Such dramatic increment in the peak-valley gap can influence the normal power transmission and even damage the utilities of the power grids (Gao and Zhang, 2011, p.128).
Conclusion
The essay introduced the historic background of the the development of electric cars as well as the environmental influences of them. It raised a research question that what are the positive and negative environmental impacts of electric vehicles? Because a lack of understanding of the environmental influence of electric cars, it is often assumed that electric cars are either entirely green or much greener than traditional cars. The research will explore both the positive and negative influence of electric cars, which will not only inform the overall environmental influence of new energy cars, but also point directions for the further development of electric vehicles.
Reference
Bora, Y., Önen, U., & Umurkan, N. (2017). A Review Of Electric Vehicles And Their Impacts On Grid.
Cao, B., (2011). Electric Vehicle Technology Progress and Development Trend, Journal of Xi'an Jiaotong University, 2004(1), 1-5.
Shafiee, S., & Topal, E. (2009). When will fossil fuel reserves be diminished?. Energy Policy, 37(1), 181-189. http://dx.doi.org/10.1016/j.enpol.2008.08.016
Kaleg, S., Hapid, A., & Kurnia, M. (2018). Electric Vehicle Conversion Based on Distance, Speed and Cost Requirements.
Sun, F., (2006). Electric Vehicle Development Status and Trend, Scientific Chinese, 2006(8), 44-47.
Chen, Q. & Sun, L., (2005). Present Status and Future Trends of electric vehicles, Science Technology, 23(4), 24-28.
Gao, C. & Zhang L., (2011). Impact of Electric Vehicle Charging on Power Grid, Grid Technology,2011(02), 127-131.
Mu, L., Zhou, Q. (2008). The Status Quo of Electric Vehicles in the World. China Academic Journal Electronic Publishing House, 2008(2), 66-72.
Electric Cars Can Harm Environment. (2017). Nature, 541(7638), 438-438.
Niitsoo, J., Taklaja, P., Palu, I. and Kiitam, I. (2015). Modelling EVs in Residential Distribution Grid with Other Nonlinear Loads. 2015 IEEE 15th International Conference on Environment and Electrical Engineering (EEEIC).