You would have known what an electric vehicle is, and why it is important in the modern automotive industry. In this post, we are going to discuss Electric vehicle efficiency.
An electric vehicle uses one or more electric motors to convert the electric energy to mechanical energy. The energy conversion is more efficient in electric vehicle than that in an IC engine vehicle where the IC engine converts chemical energy to mechanical energy.
We would come across a few questions about the efficiency of the electric vehicles whenever a comparison to IC engine vehicles happen.
- Which is the most efficient vehicle – EV or conventional vehicle?
- Does an EV really save energy?
- etc.
We are going to read answers to some of the important questions about EV efficiency.
What does the efficiency of an electric vehicle mean?
The efficiency of the system can be defined as the ratio of energy consumption at the output to the consumption at the input.
For example, if an electric motor supplies 1kW of energy by consuming 1.2kW from the power supply, the efficiency of the motor is 1/1.2 = 0.833.
That is 83.33%.
The motor could convert 83.33% of the power input to mechanical energy. What happened to the remaining 0.2 kW?
The power dissipated as mechanical loss, core loss, copper loss, hysteresis loss, etc.
If an electric vehicle, the energy conversion happens from the battery to the wheels of the vehicle.
The chemical energy stored in the battery is converted into electrical energy and then the motor converts electrical energy to mechanical energy.
The possible energy losses during the conversion are in
- Battery (thermal losses)
- Motor (mechanical, hysteresis, core loss, copper loss, etc.)
- Inverter (switching losses in IGBTs, copper losses, etc.)
- Transmission (Mechanical loss, friction loss, etc.)
- Wheel (Mechanical loss, thermal loss, friction loss, etc.)
In addition to the above list, there is energy consumption to overcome aerodynamic drag.
From the user point of view, the more sensible way to express the efficiency of an electric vehicle would be the KWh consumption per kilometer.
For a designer, the efficiency of the inverter, motor, transmission, friction, etc. matter.
But the customer of electric vehicle checks only how long he can travel with a fully charged battery (or kWh energy).
Why does the efficiency of electric vehicle matter?
Electric vehicle consumes energy stored in a battery for propulsion. It’s clear that the higher the efficiency lower the losses.
The efficiency of the whole system is the product of individual components. If the efficiency of Motor is 85%, the inverter is 98%, and all other components is 90%, the total efficiency would be 0.85*0.98*0.90 = 0.7497 ie. 74.97%.
Since an electric vehicle is battery-powered, reduced power loss improves the distance that could travel.
Internal combustion engine has maximum efficiency around 25 – 50% [wiki]. It’s far lower than that of an electric motor.
How to calculate the energy consumption of an electric vehicle?
The total energy consumed by an electric vehicle to travel is the sum of energy to overcome aerodynamic drag, friction, electrical losses, energy to accelerate the vehicle.
You can read the detailed post
Whether efficiency of electric vehicle related to the range?
The total distance traveled by an electric vehicle depends on the energy stored in the battery. The more capacity to the battery the more distance the vehicle travels.
If the battery has the same capacity vehicle with more efficient components travels longer distances.
The vehicle manufacturers focus to minimize the energy consumption of the electric vehicles.
How to improve the efficiency of an electric vehicle?
How to improve the efficiency of an electric vehicle? Vehicle manufacturers can optimize the vehicle control unit to minimize the energy consumption of an Electric Vehicle.
Each component of an electric car can be individually optimized to reduce energy loss.
For example
- Proper control algorithm reduces inverter switching losses
- Minimize heat loss
- Use high-efficiency transmission
- Use CVT at optimal efficiency region
- Operates motor at high-efficiency load
- Reduce friction loss in tire
Conclusion
The efficiency of the electric vehicles affects the total distance that can be traveled by the vehicle with a fully charged battery. Compared to internal combustion engine vehicles, electric vehicles have higher efficiency.
Since the energy density of batteries is lesser than fossil fuels, it’s important to have higher efficiency for the EVs so that they travel more distance.
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Key points
- Energy efficiency is important in electric vehicle
- Higher efficiency means more range
- Electric vehicles are more efficient than IC engine vehicles
