lectric Vehicles and their Impact on CO2 Emission, Power Grid, and Battery Range

Today, more people are becoming conscious of climate change and turning to electric cars as a more eco-friendly option. These vehicles ushered a solution to the issue of greenhouse gas emissions and the reduction in the usage of fossil fuels, hence air pollution, and global warming.  Electric vehicles only require the recharging of their batteries for energy.  However, upstream, the process of recharging increases the demand on the power grid.  In the power grid, there are two types of power plants: those that produce more greenhouse gas and those that are zero-emission.  Electric vehicles’ dependency on the power grid is an ecological issue mostly when the power plant generates greenhouse gas which accentuates global warming.  This paper analyzes three key issues of electric vehicles: the increased CO2 emission and load on the power grid, and the battery range.

Electric Vehicles and CO2 Emission  

            Electric vehicles (EVs) shift energy dependency from gasoline to electricity.  In electric vehicles, the absence of an internal combustion engine fueled by fossil fuel makes them eco-friendly and zero-emission.  However, EVs still rely on an external power source to recharge their batteries and accumulators (Darabi & Ferdowsi 2012).  The reliance on external power source means EVs still indirectly increases CO2 emission when the upstream power plants emit greenhouse gases into the atmosphere in the process of power generation.  Power plants that use fossil fuels and other combustibles emit greenhouse gas, degrading the environment.  In contrast, power plants that generate electricity from renewable energy such as wind, solar and hydraulic sources emit little or no gas (Holmberg & Erdemir, 2019).  Hence, the amount of emission produced by the power plants depends on the energy source. If the energy is from a non-renewable source (i.e. combustibles such as coal, fossil, and nuclear fuels),  the CO2 emissions are significantly higher compared to using renewable/clean sources of energy ( i.e. non-combustible sources such as solar, wind and hydraulic sources).  Holmberg and Erdemir (2019) conducted a study to compare the CO2 emission from combustible and non-combustible sources to charge electric vehicles. They found that when charging the car from a source using coal, the emission is 180 g/km, from oil 151 g/km, from natural gas 84 g/km, compared to 8 g/km for solar photovoltaics and geothermal energy and  1–3 g/km, when the electricity source is biomass, nuclear, wind, hydro or concentrated solar power. Even though the amount of emission produced depends on the material used to generate the energy, coal still accounts for roughly 25% of the world energy supply and 40% of the carbon emissions (Nejat, Jomehzadeh, Taheri, Gohari, & Abd Majid, 2015).  As about two-thirds of the world’s total electric power is generated from fossil fuels, electric cars ultimately consume mostly fossil fuels (M. S., & Thomas, I. L. 2001).  

To mitigate the increased load on power plant and the resultant CO2 emission, the integration of renewable energy sources for power production and a Regenerative Braking System in EVs will go a long way to reduce the dependency on non-renewable energy sources. Regenerative braking is an efficient technology that improves the efficiency of electric vehicles. Substantial energy savings are in fact achievable, from 8% to as much as 25% of the total energy use of the vehicle, as demonstrated by Xu, Li, Xu, & Song (2011). The system utilizes an electric motor, providing negative torque to the driven wheels and converting kinetic energy to electrical energy when brakes are applied. The electrical energy produced in the process is then used to recharge the battery. 

 Electric Vehicles: Load on the Power Grid

The load on power grids increases as more people switch to EVs.  An increase in EVs means more recharging activities, which increases the power demand on the power grids, and potentially a need for additional power plants to bear the load.  A study conducted by Van Vliet and Faaij (2011), shows that at 30% switch to EVs, uncoordinated charging would increase the national peak load by 7% and household peak load by 54%, which may exceed the capacity of existing electricity distribution infrastructure. This could increase the operational cost of power plants which will then be transferred to the consumer.  However, this problem can be remediated if off-peak charging is successfully introduced. The notion of off-peak charging is one in which the charging of EVs is done during the period when the demand on the grid from other items such as offices and industries is low. The time of the day when off-peak charging is optimally efficient is typically at night.  By opting for off-peak charging, additional generation capacity will not be required from the grids for driving electric, even in case of 100% switch to electric vehicles.

Electric Vehicles and Battery Range

Most people assume that EVs can take them to about anywhere they want to be.  The reality is that the battery of the EV has to be charged almost every 150 miles, highlighting the relatively short battery range of electric EVs.  In addition, it takes a long time to recharge it, usually for several hours.  The long charging time and short range of the battery are major drawbacks.  For short distance driving, this is not a major issue, but for long-distance driving, it is a major one (Adler, Mirchandani, Xue, & Xia,2014).

To overcome the long charging time and short range of the batteries, EV industries have come up with a new concept of battery “swapping stations” (Mak, Rong, & Shen, 2013). At this swapping stations, the users are able to exchange their drained batteries for a fully recharged one during a long trip.  However, these swapping stations need to be strategically located to make this system more efficient.  For this purpose, they have to be located between the origin and destination of the traveler (i.e along the trip trajectory)  to avoid unnecessary and long detours when the users need to swap their batteries.

Conclusion

In conclusion, the perception of conventional electric cars as eco-friendly is demystified by their high dependency on power plants and the CO2 emission that results from the increased load on those power plants.  They also have a relatively short battery range, which implies their limitation when it comes to long trips.

References

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