Fleet managers and vehicle owners are rapidly adopting more sustainable forms of mobility to meet organizational sustainability goals or to simply lessen one’s carbon footprint. This includes the use of renewable fuels such as biodiesel and renewable diesel, but it also means increasing the adoption of battery electric vehicles (BEV) and hydrogen fuel cell electric vehicles (FCEV). New owners of these alternative powertrain vehicles are having to grapple with unexpected challenges associated with moving away from combustion, while having to deal with new cold weather operability issues. Any vehicle owner or fleet operator who experiences freezing temperatures can tell you that winter weather can have an impact on the performance of a vehicle. Properly managed, high quality biodiesel blends are successful in the coldest of climates. Just like regular petroleum diesel, biodiesel (B100) will gel in cold temperatures. However, if handled appropriately biodiesel blends up to B20 have virtually no impact on cold weather operability.
Alternatively, for owners of light-duty gasoline powered passenger vehicles, cold weather means mornings spent pre-heating your car and lower fuel economy. In fact, the U.S. DOE estimates a conventional gasoline car’s gas mileage is roughly 15% lower at 20°F than it would be at 77°F.1 But lower fuel economy is not just an internal combustion engine issue, this loss of fuel economy and thus range also impacts electric vehicles, which is to be expected but is not readily acknowledged. However, we are learning this loss in efficiency and range can be far greater than that of a traditional diesel vehicle in a similar climate. This loss of efficiency in extreme ambient temperatures not only has a significant impact on the day-to-day operation of the vehicle, requiring it to run shorter routes and charge more frequently, but it will also have significant impacts on the economic and environmental characteristics of an electric fleet.
For example, we know electric vehicles can have a significant cost premium over traditional internal combustion engines, costing up to 2.2 times more per vehicle according to NREL2. However, fleet managers are often sold on the idea that these cost premiums will be rapidly paid back due to higher fuel economy and lower maintenance cost. This may often be true when electric vehicles fuel economy is compared to a standard diesel vehicle such as a bus operating in relatively mild conditions. In fact, the assumed increase in fuel economy is imperative if fleets are hoping to reduce their cost of operation given the premium both on the vehicle and the fuel; electricity and hydrogen is more expensive than diesel and biodiesel on a BTU basis.
However, as battery electric and fuel cell buses are making it out of the pilot stage and into the real-world, we are seeing that benefits calculated in pilots conducted in Los Angles, the Bay Area, and other mild climates may not translate one-for-one to areas like Duluth, MN, Ames, IA, or even central Florida. A recent study by Cleveland State University and the Center for Transportation and Environment3 showed, based on a sample of convenience that a deviation in temperature from 65° F can significantly reduce the fuel economy of a an electric or fuel cell bus. Furthermore, a report entitled Charge the North4, conducted by FleetCarma showed that in the winter months EV’s evaluated as part of their study drove fewer miles, but consumed more energy than in warmer times of the year, strongly implying a correlation between temperature and efficiency. This is likely due to two factors, first the vehicle itself was less efficient at converting energy to work, and second a significant amount of additional energy was required for climate control (cabin heating). This problem of heating is significant, so much so that Tesla recently moved away from electrical reistance heating to air source heat pumps in their Model Y.5
These first studies highlight the need for additional research into the relationship between of ambient temperature and the efficiency of alternative powertrains such as fuel cell and battery electric.
Understanding this relationship will help fleet managers and policymakers better understand the environmental and economic performance of electric vehicles compared to the traditional combustion and vehicle counterparts. Biodiesel and renewable diesel are better than other fuel alternatives, cleaner for the environment, and ready for consumers now in all climates.
2 https://www.nrel.gov/docs/fy19osti/72864.pdf (NREL reports a cost of $1,053,689 and $459,935 for electric and diesel buses respectively.)