Drivers of electric cars should avoid excessively slow driving to conserve energy
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In a recent analysis by telematics provider Geotab, over three million electric car trips were evaluated to better understand the factors that affect the range of electric vehicles (EVs). The findings suggest that driving too slowly can lead to a decrease in range, especially on hot summer days.
At low speeds, aerodynamic drag (air resistance) is reduced, which generally improves efficiency compared to high-speed driving. However, the impact of ancillary loads like air conditioning (AC) becomes proportionally more significant at low speeds because the power needed for cooling still consumes considerable energy regardless of speed.
During hot summer days, heavy AC use can markedly decrease range since cooling systems draw substantial battery power. Typical real-world tests show that EV range is often lower in summer conditions because of necessary AC cooling and other factors compared to standardized range tests conducted at moderate temperatures without active climate control.
Air resistance itself grows with speed squared, so driving slower reduces aerodynamic losses. However, if the vehicle speed drops too low, the continual energy draw from AC can dominate overall energy consumption and reduce effective range.
In summary, driving slowly reduces energy loss from air resistance, potentially increasing range compared to high-speed driving. However, on hot summer days, AC use greatly increases energy consumption, which can reduce range even at low speeds. Very slow speeds might mean the AC energy use is a larger fraction of total consumption, decreasing range despite lower drag.
The net effect depends on how much AC is used and the exact speed; thus, driving moderately rather than very slowly might optimize range in hot weather.
Simple tricks such as pre-cooling a vehicle while it's still plugged in, parking in the shade, and using clever air conditioning features like seat cooling and recirculation can help tame summer consumption in electric vehicles.
These findings challenge the common misconception that driving slowly always saves power in electric vehicles. Instead, finding the right balance between speed and energy management is key to efficient driving in electric vehicles.
References:
[1] Geotab, "Electric Vehicle Adoption in the US: Driving Habits and Impact on the Grid," 2021.
[2] U.S. Department of Energy, "Electric Vehicles: Understanding Range," 2020.
[3] National Renewable Energy Laboratory, "Plug-in Electric Vehicle Range and Efficiency," 2019.
The findings suggest that while driving slowly can reduce energy loss from air resistance, the increased energy consumption from air conditioning during hot summer days can potentially outweigh these benefits, limiting the range of electric vehicles. Moreover, balancing speed and energy management through techniques such as pre-cooling, parking in the shade, and smart AC usage can help optimize the range of electric vehicles, contrasting the common misconception that slow driving always saves power in these vehicles.
