Fuel cells have long promised a different and potentially superior path to electrifying automobiles, compared to battery-electric vehicles (EVs) with their limited range and relatively long recharging times. One of the biggest obstacles has always been the lack of infrastructure and supply–hydrogen must first be liberated from water, methane or other compounds–and the problems of storing sufficient quantities of it on board. I’ve driven prototype fuel-cell vehicles (FCVs) and found the experience pretty similar to driving a regular car, as long as you have a hydrogen filling station handy.
Nissan makes the case that ethanol (chemical formula C2H6O) is much easier to source and distribute than gaseous hydrogen, and the process for making it give up its hydrogen is routine, at least under laboratory conditions. However, as the alternative energy research subsidiary of my former employer, Texaco Inc., found in pursuing a similar concept with gasoline, it’s one thing to do this in a bench-scale device and quite another to do it in a size and shape that will fit easily and safely in a car and run as reliably as an internal combustion engine. I suspect Nissan’s engineers have their work cut out for them for the next four years.
The bigger questions about this approach are more basic: Does it make sense from an economic, energy and environmental perspective, and can it find a large enough market? Consumers already have a wide range of green alternatives from which to choose, ranging from Prius-type hybrids (gasoline only), plug-in hybrids (gasoline + electricity) and battery EVs, not to mention the continuous improvement of non-electric cars.
Nissan didn’t include many numbers in the documents accompanying its press release, but the chemistry and math involved are pretty simple. At 100% efficiency, a gallon of ethanol could produce just under 0.8 kilograms (Kg) of hydrogen (H2) using the standard steam-reforming process
. The best efficiency I could find for this ethanol-to-hydrogen conversion was around 90%
, so in the real world that gallon of ethanol would yield around 0.7 Kg of H2–enough to take Toyota’s Mirai FCV about 46 miles
. That’s pretty good, considering that same gallon in a Chrysler 200 equipped as a flexible fuel vehicle (FFV) would drive an average of just 21 miles
. Fuel cells are much more efficient than internal combustion engines.
The economics of operation don’t look bad, either. If we use today’s average US price for E85 (85% ethanol + 15% gasoline) of $1.87/gal
. as a proxy for an ethanol retail price, that equates to around 4 ¢/mile, using the Mirai’s published fuel economy data
. That’s about 15% cheaper than a Prius on regular gasoline at this week’s US average
of $2.40/gal., but it’s also around 10% more expensive than a Nissan Leaf
using off-peak electricity
in northern California.
Emissions are trickier to assess. There’s a lively and growing controversy
about whether biofuels produced from crops can truly be considered carbon-neutral
, even in places like Brazil where the yields from sugar cane are so high. There’s much less controversy that the production of most US ethanol from corn is anything but a net-zero-emission endeavor
. Corn requires fertilizer sourced from natural gas, and ethanol refineries consume gas (or coal) and electricity in their production process. In any case, when Nissan characterizes their planned ethanol FCV as having “nearly no CO2 increase whatsoever
“, they are either oversimplifying a very complex discussion or taking a large leap of faith.
We can count the CO2
coming out of the tailpipe of such a car, and it would need a tailpipe because the onboard ethanol converter would emit about 12.5 lb. of CO2
for every gallon of ethanol converted to pure H2, plus some CO2
from the ethanol burned to heat the unit. My back-of-the envelope calculation gives a figure of 135 grams of CO2
per mile, or 20% lower
than a Toyota Prius on gasoline. It would not be a Zero Emission Vehicle (ZEV), though of course an EV running on average grid electricity isn’t really a ZEV, either, except in isolated regions or at specific times of day.
Even if there aren’t any deal-killers here, I’m skeptical about Nissan’s fundamental assumption that the ethanol infrastructure for their FCV would be that much easier to develop than the H2 infrastructure other FCVs require. That’s because of the cost and ownership structure of the retail fuels business, which as I’ve argued previously
helps explain why your corner gas station is unlikely to sell E15 (85% gasoline, 15% ethanol) any time soon, despite the EPA having approved it for newer cars
At least in the US, most gas stations are owned by small businesses, not by the oil companies whose brands they display. Margins are slim, and these folks don’t have deep pockets, so adding a new fuel like pure ethanol or the ethanol-water mix that Nissan suggests
, poses a difficult business decision: Do you take over an existing tank and stop selling diesel fuel, or premium gasoline with its high margins? Or do you rip up the forecourt to add a new tank, which entails being out of business for months–or even longer if you discover that one of your existing tanks is leaking? Either way, the investment costs and disruption to current customers are significant, in exchange for selling what at first would certainly be a low-volume product. When I was in the fuels supply & distribution business, we would have called that kind of decision a “no-brainer.”
If Nissan can’t encourage enough service stations to add ethanol or an ethanol/water blend–E85 would not work–to their product mix, do they start their own service station network? That seems unlikely. And if you buy one of these cars in a few years, should you carry a case of vodka in the trunk as an emergency range-extender? That’s only half-facetious.
I give Nissan credit for pursuing a novel option for making fuel cell cars more viable, as an alternative to today’s range-limited EVs. Ethanol looks like a cost-competitive source of hydrogen, and it is at least easier to store than H2 gas or liquid H2. However, they face practical and marketing challenges that might well offset most of the advantages the company claims to see. The ethanol FCV could encounter the same chicken-and-egg dynamic as FCVs running on hydrogen, or indeed any new model requiring a fuel that is not distributed at scale today. It will be interesting to watch their progress.