Electric car efficiency

Importance of electric car

Electric cars are the alternative available to overcome the energy crisis with internal combustion engines. 26% of primary energy in the world scale is consumed on transportation and 23% of greenhouse gas emission is related to energy. Automobiles play an important role in transportation as they are part of street transportation which is part of day-to-day activities. Limiting energy usage from non-renewable sources and finding an alternative for the same functioning in an automobile are very important. Electric cars are the best modes of transportation to replace internal combustion engine cars. Increasing their efficiency for better functioning is a challenging task. The image of an electric car is shown in Fig-1.

Fig-1 Image of electric car [1]

Components of battery-based electric cars

Battery-based electric cars have three main components, they are electric battery, electric motors, and motor controller. The schematic representation of the electric car components is shown in Fig-2. The working of battery-operated electric cars is simpler compared to internal combustion engine-operated cars. The components don’t need a lubrication system, gearbox, cooling system, etc in order to operate. One of the important aspects is charging the battery which gets charged when it is plugged into an external electric source or during braking recuperation. The motor controller allows the power supply as per the loading situations. These motors convert the electrical energy into mechanical to run the drive train.

Fig-2 Components of electric car [2]

The efficiency of batteries in electric cars

Battery charging in electric cars is one of the important factors to be considered to increase their efficiency in saving energy. The efficiency of the charger in today’s market varies from 60% to 90%, where 3% to 40% of energy is wasted as heat in the energy grid. There are various kinds of batteries used in electric cars, such as lead acid batteries, nickel metal hybrids, lithium-ion, and zebra. Starting with lead acid batteries in 1999, the evolution of batteries began for electric car applications. Nickel metal hybrid batteries were used in some Toyota automobiles. To overcome the environmental impact of these nickel hybrid batteries, zebra cell-based batteries were used. Currently, lithium ion-based batteries are popular.

Fig-3 Efficiency of batteries in electric cars [3]

Environmental impact of electric cars

Electric cars affect the environment indirectly through the emission of greenhouse gases as they utilize electricity from various sources. The life-cycle greenhouse gas emissions of electric vehicles depend on the power grid sources and their carbon emission. When electric vehicles are charged, they constitute an additional load in the power grid. The effect of this additional load on the grid, especially on power plant operation and greenhouse gas emissions depends on several factors such as the magnitude of additional load connecting the grid, charging time, loading duration, the structure of the power sectors, and availability of renewable energy resources. To overcome the problems with the CO2 emission with exiting power sectors a few important points to be considered such as an assessment of CO2 impacts assuming load management. This assessment would help to optimize the current power sector of baseload generators (low-carbon, high-carbon) in the respective areas. This also helps in the availability of baseload investment options. Real-world data on the technical feasibility of the shift to night times and consumer acceptance should be generated. The promotion of renewable means of electricity generation should be encouraged.

Fig-4 Energy production by various sources [4]

Improving the efficiency of electric cars by vehicle-to-grid and vehicle-to-house networks

These are the methods of energy integration by considering the energy supply (conventional and renewable power generation) and demand (electric vehicles). The key aspects are to provide ancillary grid services and integrate it with renewable electricity generation, and load management [5].

Vehicle-to-grid (V2G)

It is a concept of energy generation by electric vehicles functioning bi-directionally in terms of load demand and as load supply to the grid whenever there is a need. V2G allows the integration of significant numbers of electric vehicles to improve the local grid quality and thus help in reducing the amount of regulation reserve needed. They provide spinning and regulation up to reserve capacity and reduce the peak load source. They also increase the load factors and reduce the cycling of power plants. Further they provide significant revenues for electric vehicles.

Vehicle-to-house (V2H)

It is a concept of energy generation for electric vehicles by connecting them to houses and helping in reducing the grid demand. These could also be used as emergency generators. Other electric cars could integrate significant amounts of electricity from renewable energy sources such as windmills. They comprehend load management which makes consumer acceptance crucial. Also, battery costs and the number of charging cycles may pose restrictions to the implementation of this concept.

Reference

[1] https://www.theguardian.com/money/2019/oct/05/electric-car-ways-to-charge

[2] Helmers, E. and Marx, P., 2012. Electric cars: technical characteristics and environmental impacts. Environmental Sciences Europe, 24(1), pp.1-15.

[3] https://cleantechnica.com/2020/06/10/this-stunning-chart-shows-why-battery-electric-vehicles-win/

[4] https://www.dw.com/en/how-eco-friendly-are-electric-cars/a-19441437

[5] Hacker, F., Harthan, R., Matthes, F. and Zimmer, W., 2009. Environmental impacts and impact on the electricity market of a large scale introduction of electric cars in Europe-Critical Review of Literature. ETC/ACC technical paper, 4, pp.56-90.