Electric Freight Transport’s Benefits Depend on Grid Decarbonization!
While much of the debate around cleaning up the transportation sector has focused on the types of cars you and I drive, one of the big sources of local and global air pollution is the big rig trucks shipping the stuff you and I consume around the country. There are roughly two million truck drivers on the road. And the average class 8 truck drives five times the mileage in a year compared to an average personal car. Further, these trucks are largely powered by diesel, which is a notoriously dirty transportation fuel, especially when it is burned in older trucks without modern emissions controls. So in summary, we have a large fleet of really dirty and heavy vehicles blowing diesel pollution into the air that people living near highways breathe. As I have written about before, California is trying to address this issue by decarbonizing heavy trucks. You might wonder how much decarbonizing this sector actually improves things.
In a paper hot off the presses, we (Fan Tong, Corinne Scown, Derek Wolfson, Alan Jenn and I) try to answer this question in a very specific way. We ask what would happen if we replaced the fleet of class 7 and 8 trucks with electric trucks and compare the consequential health and global warming damages to those from a fleet of modern diesel trucks. This turns out to be one of those ideas that seemed simple in the beginning and turned out to be brutally hard in the end. In order to spare you the details of what we did, let me draw you a picture.
We built a so called integrated assessment model, where we modeled:
- The flow of goods between origin and destination pairs
- The dispatch of trucks over different hours of the day
- Regulations of how long drivers can drive before they need to rest.
- Future electric battery & truck technology
- Future diesel truck technology and emission controls
- A future grid with varying degrees of integration of renewables and the resulting emissions
- Health and global warming damages from the resulting emissions
So we model a system that soup to nuts goes from being largely powered by diesel trucks to one that is fully powered by different types of electric trucks. Then we compare it to a system that is powered by modern diesel trucks with all the emissions control technologies required today, plus a little bump in fuel economy. This is different from the economics literature (e.g. this paper) that has tried to answer the question of whether a single electric vehicle is “better” than its internal combustion counterpart. That literature has used the marginal emissions from the current grid and not really modeled the consequences of additional load due to charging that vehicle.
What we are doing here is the large scale exercise of adding a bunch of electric trucks onto the grid, which is a massive increase in load across the country. We also acknowledge that a future grid is likely cleaner than the current grid and use Alan Jenn’s very cool model to do just that. So what did Max learn that he didn’t know before (which is a lot)?
- Electric trucks consume less energy than diesel trucks, assuming most of that electricity isn’t generated with fossil fuels. The end-use energy savings could be as high as 1 Quad (1015 BTU). This is largely due to the large inefficiency of the combustion engine in translating fuel into the energy to move the truck around.
- The health and climate impacts of electric trucks depend critically on the composition of the US electric grid. If we charge our future electric truck fleet on something resembling the current grid, most places in the United States are worse off in terms of health and global warming damages. This is largely due to the fact that the marginal power plants that come online for the significant additional load, are relatively dirty. As you can see in the figure above, damages are higher (red) for electric trucks for the status quo grid over most of the US (the West is, of course, best).
- However, with a high-renewable electric grid, the avoided damages from electric trucks exceed $5 billion annually, 80% lower than future diesel trucks. This is significant as this is what economists call “making the world a better place”. If the grid is AOC clean, plugging in a ton of trucks is better than shipping your Amazon boxes around in diesel trucks. You can see that in the same figure above, where the bottom right map is now mostly blue instead of red.
- There is an interesting opportunity here related to the belly of the duck. Trucks are dispatched (most commonly in the early morning) and drive long distances. Batteries aren’t yet cheap and light enough for electric trucks to last a full day on one charge, so drivers will have to stop during their trip and plug in. Yes, on a trip level there is much uncertainty about congestion and when trucks get where, but on average, one could manage a massive fleet of trucks to charge at times when there are excess renewables generated, that are cheap at the time. Combined with the right pricing structure, this could be a win win! Take the excess renewables off the grid operators’ hands and make sure little Betsy gets her new millennium falcon lego set on time! Or in fancy speak, the expected midday peak in charging loads according to our modeling could facilitate renewables integration, particularly in the Southeast and Mid-Atlantic regions where loads are highest.
Now, is our paper the final answer to this question? God no! It’s a tiny first step in a large number of papers that should be written. Here are a few questions that we do not answer, that are of key importance:
- What is the change of freight patterns due to electrification or other emerging technologies (e.g., truck automation, cashier-less stores, and further penetration of e-commerce)?
- What are the impacts of weather and aging on battery performance?
- How is growing urban traffic congestion going to affect health benefits from electrification?
- How much heterogeneity is there by commodity type, region, and by season?
- What are the (private) economics of electric trucks?
- How do you optimally roll out charging infrastructure?
There are of course many more. I am keenly interested in the role of hydrogen in long haul trucking and may write another blog post in a year or two, should we take a stab at this question. But to close, I think trucking is a vastly understudied area in energy economics and change is afoot. If we want change in the right direction, we better start answering some of these big questions!!!
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Suggested citation: Auffhammer, Maximilian. “Electrifying Big Rigs?” Energy Institute Blog, UC Berkeley, June 28, 2021, https://energyathaas.wordpress.com/2021/06/28/electrifying-big-rigs/
Maximilian Auffhammer is the George Pardee Professor of International Sustainable Development at the University of California Berkeley. His fields of expertise are environmental and energy economics, with a specific focus on the impacts and regulation of climate change and air pollution.