Mr. Green Energy Efficiency Observation-The Impact of Climate on the Range of Electric Vehicles

Electric vehicles (EVs) are a key part of many governments' plans to reduce carbon emissions. As more electric vehicles are deployed across a wider range of climates, we are learning about the impacts of these climates on electric vehicles. This article will look at the impact of climate on electric vehicle performance, the problems it can create and some of the solutions being deployed.

Ambient temperature affects cruising range

While all vehicles are affected by temperature, electric vehicles are particularly susceptible because of their battery-centric powertrains. Batteries work through a chemical reaction that slows down at lower temperatures, resulting in less efficiency.

Another more important issue is warmth. Electric vehicles do not have an internal combustion engine (ICE) to generate heat and need to draw energy from the battery to heat the cabin. Cold temperatures mean windows fog up, requiring the use of electric defoggers. In winter, when the days are short and the nights are long, headlights need to be used longer. Rolling resistance increases when tires are cold and when driving in snow and mud. Using air conditioners on hot days requires more power from the battery. In the event of extreme temperatures, even a battery thermal management system must go all out. All these situations will increase the power consumption of the battery and reduce the power of the vehicle.

Outside temperature can have a huge impact on range

Electric vehicle manufacturers only release range data at nominal temperatures, but there have been some studies examining the impact of climate on available range.

A recent UK study on electric vehicles showed that cold weather can reduce driving range by up to 30%. A 2019 study conducted in the United States by AAA tested five models at temperatures of 20°F (-6.7°C) and found that range was reduced by 12% without heating in the cabin. In the case of heating, it further dropped to 41%.

The US magazine Consumer Reports (CR) studied multiple short trips (2019) and highway driving (2023). Short-distance trip tests showed that the range dropped by 50% due to repeated heating of the cabin. Highway driving test results showed range was reduced by 30 to 35 percent at an ambient temperature of 16°F (-8.9°C). Testing in hot weather of 95°F (35°C) showed that range dropped by 4% without air conditioning and by 17% with air conditioning.

These tests show that cold weather is more of a concern than warm weather. Heating and cooling are the main culprits, reducing range by 30% in moderately cold areas and 50% in colder areas.

Challenges facing buses

Electric buses weigh more and run longer than electric passenger cars, making them an excellent case study for studying weather challenges faced by battery-powered vehicles.

Ideally, buses are used almost all day long. Buses also have greater heating (or cooling) needs because every time the bus stops and the doors open, acclimated air is lost and a new batch of air needs to be heated or cooled. A full bus benefits from the body heat emitted by passengers in the winter, but in summer this heat puts additional stress on the climate control system.

Let’s look at the lessons learned from some case studies of electric bus solutions in colder climates, as cold weather has a greater impact on electric vehicles than warm weather.

More charging stations

In Chicago, average winter daily temperatures range from 25°F to 35°F (-3.9°C to 1.7°C), with a low of -9°F (-22.8°C) in 2022, according to the Chicago Transit Authority (CTA) in 2014 It will begin trials of electric buses in 2019 and plans to have an all-electric fleet by 2040.

CTA has built fast charging stations at both terminals of the Route 66 bus line, which can be plugged into the roof of the bus for charging. The driver will constantly monitor the battery level to prevent it from running out of charge and stranding the bus.

Route 66 is a 10-mile one-way trip, and an electric bus loses about 8% of its battery energy for each trip. In the winter, they have a range of about 100 miles on a full charge, and drivers need to recharge when the bus battery drops below 50%. This means a bus can make about six one-way trips between charges. With enough charging stations, electric buses could cover all routes.

more heaters

It's no surprise that the CTA report points to heating as the main cause of battery drain. To solve this problem, older vehicles have been retrofitted with small diesel engines to provide extra heat during extreme weather, taking some of the load off the batteries. The new buses being ordered are equipped with newer, more efficient heat pumps so they do not require additional heaters.

alternative planning

The city of Juneau, Alaska also plans to switch to all electric buses. The new buses ordered by the city have larger batteries and a range of 282 miles, which is expected to drop to 182 miles in the winter but is still enough to cover all of the city's bus routes. The city plans to use its older electric buses, which have a more limited range, on commuter routes that only run during peak hours.

Technical Improvement

Companies such as Letanda, an electric bus manufacturer in Quebec, Canada, are developing buses designed for cold climates. The buses feature lightweight aluminum construction that reduces condensation through heated surfaces and floor heating to increase passenger comfort while minimizing energy consumption.

Electric heat pumps are replacing traditional heaters not only in buildings but also in large vehicles, and are up to four times more efficient. Power Integrations offers AEC-Q100 compliant InnoSwitch3-AQ and LinkSwitch-TN2Q offline switch IC products that enable simple and efficient heat pump power supply designs.

future outlook

With cities like Oslo, Norway, planning to convert their entire public transport fleet to electric vehicles by the end of 2023, there is ample opportunity for innovation and growth in the industry. While the initial capital outlay for new buses and charging stations is large, operating costs for electric buses are much lower, even in extreme weather. For example, the CTA calculates that operating a 40-foot electric bus costs $2.01 per mile, compared with $3.08 for a diesel bus and $2.63 for a diesel-electric hybrid.

Transport authorities are also banking on electric bus prices falling sharply as sales increase. At the same time, climate-related challenges must be understood and addressed to ensure a successful transition to a greener future. By focusing on solutions and embracing technological advancements, electric buses can become a reliable and environmentally friendly form of public transportation, no matter the weather.

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