Tuesday, December 19, 2017

The Missing Piece in Plans for an All-Electric Vehicle Fleet: Electricity

The New York Times has a piece today on barriers to the replacement of internal combustion-powered vehicles to an all-electric fleet in the United States.  It talks about production costs, the availability of key minerals and the need for a charging station infrastructure, but it oddly passes over the most obvious impediment, at least from the perspective of climate change, the large increase it would require in electrical generating capacity.

If the goal is, at it should be, rapid decarbonization of the economy, conversion to electric powertrains is worth doing only if it results in the replacement of petroleum by renewable energy sources, so lets look at the arithmetic.

According to the latest version of Lawrence Livermore’s invaluable energy spaghetti diagram, 25.7 quads of energy, in the form of petroleum, were used as inputs to the transportation sector.  (A quad is a quadrillion BTUs, approximately the amount of energy in eight billions gallons of gasoline.)  Electric vehicles vary in their efficiency, and there might be improvements on this front in the future, but lets use the common assumption that EV’s are four times as energy efficient as ICV’s; that means we are looking at about 6.4 quads of added electrical demand.

Electricity output in 2016 was 12.6 quads, which implies we would need a bit over 50% more capacity to accommodate an all-electric fleet.  Of course, the actual expansion would be less than this because EV’s could take advantage of off-peak capacity.  Nevertheless, from a decarbonization perspective, the critical constraint is not capacity as such but energy inputs as fuel.  A natural gas plant might be able to put out more electricity over a 24-hour cycle without additional capital investment, but only by burning more gas.  Those with greater expertise than I can summon can tell us how much efficiency we can squeeze from existing and prospective electrical generating technology.

So somewhat more than 50% additional electricity is needed; how much of this can come from non-carbon sources?  The most optimistic scenario is one in which nuclear energy is included in this (non-carbon) mix, so assume the goal is simply to zero out coal and gas.  These two sources currently account for 62% of inputs into the electrical generating sector.  No doubt we can get significant reductions simply through efficiency measures; think of all those electrically-heated buildings leaking energy through poor insulation.  If for convenience we lump together increases in non-carbon inputs and efficiency savings, this would need to total 23.3 quads, the current delivery of coal and gas to US electrical power stations, if the services provided by electricity use were to remain constant.  If a shift to EV’s boosts electrical demand by, say, 40%, the need for renewable sources and efficiency savings would go up to 38.3 quads (23.3 current carbon input plus 15 new input), an increase of almost two-thirds.  It is difficult see how this could be achieved in the space of a generation or so, which is the timescale we face if we are to meet our declared carbon goals.

The bottom line as I see it is that, while a shift to electrical powertrains is necessary if we are to have motorized vehicles in a post-carbon world, realistic scenarios for the electrical sector require a massive shrinkage of the number of such vehicles we’ll be able to operate, at least for the foreseeable future.  This is unfortunate on two counts—it will make it more difficult to sustain living standards across the transition ahead of us, and it will increase the political barriers to getting the job done—but we won’t make it go away by not seeing it for what it is.


rosserjb@jmu.edu said...


Yes, problem for all electric, but I note that standard hybrids that also have ICEs generate their own electricity entirely on their own.

Peter Dorman said...

But Barkley, a hybrid is a partial transition away from fossil fuels the way partial EV penetration is. It's a step in the right direction, and that's good, but the big question is what it would take to go the distance.

Peter T said...

You're probably right, but then the solution is to look at system-wide changes. EG, more rail with intermodal transfer, more public transport, changes to housing. Maybe more work from home (I'm iffy on this, given the social centrality of work). If the US got to European levels of energy use per capita, what would the picture look like then?

Antoni Jaume said...

And if there was a fuel cell that could be fed some chemical? And I do not mean hydrogen? I read somewhere that there was one that used methanol, one such with ethanol would be quite good