In the context of the acceleration of global green transportation, electric vehicles, especially electric buses, are regarded as the key path to replace traditional fuel vehicles due to their low emissions and high energy efficiency. However, a recent study released by Cornell University has sparked a new round of discussion about the winter performance of electric vehicles. Studies have shown that the energy consumption of electric buses increases significantly in cold climates, with an increase of up to 48% in some scenarios. This not only reveals the current performance bottleneck of electric vehicles in low-temperature environments, but also poses new challenges to the sustainable operation of electric public transport systems.
Ⅰ. Research Background: Real road conditions reveal grim realities
In 2021, a two-year electric bus pilot program funded by the U.S. federal government and led by Tompkins and Regional Transportation (TCAT) was launched in Ithaca, New York. Seven electric buses will be used on 41 bus routes, covering urban cores, mountain roads and remote suburbs. The project focuses on assessing the energy consumption and operational performance of electric buses in extreme weather and terrain conditions.
The research team combined a large number of measured data to develop an energy consumption model called "Optimal Temperature Zone (OTZ)". It was found that the energy efficiency of electric buses was optimal in the ideal temperature range of 16°C to 30°C. However, when the outside temperature drops to -4°C to 0°C, the energy consumption increases by 48% compared to the model estimate. With an extended temperature range of -12°C to 10°C, energy consumption still increases by an average of 28.6%.
The study shows that the impact of cold weather on EV energy consumption is much higher than existing industry projections, posing significant operational challenges for public transport systems in high-latitude or mountainous cities.
Image: The energy dilemma of electric buses: energy consumption soars by 48.0% in the cold winter
Ⅱ. Analysis of multiple triggers for soaring energy consumption
The sharp increase in energy consumption of electric buses in cold weather is due to the combination of several systemic factors:
1. The battery preheating mechanism increases the burden
The optimal operating temperature of an electric vehicle battery is about 24°C. In winter environments, the battery must be warmed up to an operational state by a heating system, a process that consumes a lot of electricity and significantly reduces the vehicle's range.
2. The energy consumption of the cabin heating system is high
In winter operations, the demand for a comfortable temperature for passengers requires the heating system to operate continuously. On the short-distance urban routes, the heating system is forced to "restart" due to the frequent opening and closing of the doors, and the continuous entry of cold air into the cabin, which has become another major reason for the increase in energy consumption.
3. The efficiency of the kinetic energy recovery system decreases
The cold environment leads to uneven temperature distribution inside the battery, especially on platforms with high battery capacity and bulkiness, such as electric buses. The temperature difference interferes with the chemical reaction rate of the battery, making it difficult for the kinetic energy recovery system to efficiently convert electrical energy during braking or downhill processes.
4. The thermal management system of the whole vehicle is more challenging
Compared with private electric vehicles, electric buses need to cope with more passenger loads and more complex operating conditions, resulting in more complex thermal management system design. In winter, existing heat pump systems or PTC heating methods are often inefficient, increasing the energy consumption of the whole vehicle.
Ⅲ.Systemic impacts on electric bus systems
1. Rising operating costs
The increase in the energy consumption of electric buses directly leads to an increase in electricity bills. According to an estimate by the American Transportation Research Center, the average energy consumption per kilometer of electric buses in the cold winter season is 30%~50% higher than that in summer. Taking a city bus company as an example, the operating electricity cost in winter increased by about 35% month-on-month, and it needed to increase the additional shift charging time, which indirectly increased the dispatch and labor costs.
2. Range anxiety returns
Although modern electric buses have a range of 250~300 km in ideal conditions, in cold weather, this value can drop to 180 km or even lower. "Endurance anxiety" in extreme weather has begun to affect user trust and operation scheduling. For example, in the winter of 2024, a suburban bus line in Minnesota was forced to urgently deploy diesel vehicles due to the lack of electric bus life, which caused widespread public attention.
3. Infrastructure is under pressure
The decreasing charging efficiency of electric vehicles in winter also puts pressure on charging infrastructure in terms of capacity and scheduling. In order to ensure the normal operation of electric buses, urban traffic management departments need to deploy more high-power charging piles and intelligent dispatching systems in advance. For example, the City of Toronto, Canada, will deploy 50 new DC fast charging piles in the winter of 2024, and plans to build 10 heated vehicle parking and charging garages in the next three years, with an overall investment of about $30 million.
Ⅳ.Coping strategies and forward-looking solutions
1. Short-term operational optimization measures
* Night Parking Optimization: Park electric buses in heated garages or areas with thermal insulation functions to reduce the cost of starting preheating in the morning rush hour;
* Dynamic scheduling strategy: Prioritize the use of electric buses on short-term or low-frequency routes in low-temperature weather to reduce the energy consumption risk caused by long-distance operation;
* Door management modification: Minimize heat loss while ensuring safety by installing secondary sealing doors or reducing the frequency of pick-ups.
2. Medium- and long-term infrastructure and technological innovation
* Battery technology iteration: Accelerate the research and development of energy storage technologies with better low-temperature performance, such as solid-state batteries and high-nickel ternary or sodium-ion batteries;
* Heat pump system upgrade: research and development of dual-source heat pump system suitable for cold zone environment to improve the efficiency of thermal management in the vehicle;
* Construction of intelligent preheating platform: The cloud platform and big data technology are used to realize the linkage preheating scheduling of the battery, the cabin and the heating system, and improve the integration efficiency of the vehicle system.
3. Policy and industry coordination
The government can support the seasonal adaptation of the electric bus system through financial subsidies and carbon credit mechanisms. For example, the U.S. Department of Transportation proposed a draft "Clean Bus Plan" to provide a total of $800 million in subsidies for adaptive technology upgrade projects in the winter of 2025~2027. In addition, mainstream battery and vehicle manufacturers should also accelerate the industrialization of low-temperature adaptation products.
Ⅴ. Conclusion: Towards truly green smart electric mobility
Cornell's research is a wake-up call for the industry that electrification is not a one-time thing, especially in complex climates, where there is still a need to make up for the "energy shortfall". However, it also provides a clear direction for technological improvement and market opportunities for the electric vehicle industry. Through forward-looking planning, infrastructure adaptation and key technological breakthroughs, we hope to solve the dilemma of energy consumption in winter, make electric buses truly green, efficient and intelligent, and contribute China's wisdom and global strength to the future of global low-carbon transportation.
