I don't normally do breaking news, but today's announcement by PG&E and a coalition of environmental groups on retiring the Diablo Canyon nuclear power plant in California within 8-9 years merits immediate comment.
Given the enormous social and political challenges PG&E faced in undertaking the re-licensing of the facility when its current operating licenses expire in 2024 and 2025, this action is understandable, though regrettable. I lived in California when Diablo Canyon was planned and built. It was sufficiently controversial in the 1970s, and the environment has only become more contentious. Extending the operating licenses of nuclear power plants to 60 years has become typical elsewhere, but the utility's board must have concluded that it was a non-starter in today's California.
However, we should not be misled by press-release language about replacing "power produced by two nuclear reactors...with a cost-effective, greenhouse gas free portfolio of energy efficiency, renewables and energy storage." Under California's extremely aggressive renewable energy and storage targets, the alternative energy mentioned here was coming, anyway, but it was intended to replace higher-emitting sources like out-of-state coal and in-state natural gas generation. Until there is an overall surplus of zero-emission energy--when?--the energy mix is a zero sum game.
This agreement--perhaps the best deal possible under the circumstances--thus represents the net loss of 18 billion kilowatt-hours (kWh) per year of zero-emission electricity. That's equivalent to 9% of all utility-scale electricity generated in California last year. The state went through a similar event in 2013 with the permanent shutdown of the San Onofre Nuclear Generation Station between L.A. and San Diego. As I noted at the time:
How much emissions will increase following the shutdown depends on the type of generation that replaces these units. If it all came from renewable sources like wind and solar, emissions wouldn’t go up at all, but that’s impractical for several reasons. Start with the inherent intermittency of these renewables, and then compound the challenge by its scale. Even in sunny California, replacing the annual energy contribution of the SONGS units would require around 7,200 MW of solar generating capacity, equivalent to nearly 2 million 4-kilowatt rooftop photovoltaic (PV) arrays. That’s over and above the state’s ambitious “Million Solar Roofs” target, which was already factored into the state’s emission-reduction plans.
Grid managers from the state’s Independent System Operator indicated that in the near term much of the replacement power for SONGS will be generated from natural gas. Even if it matched the mix of 71% gas and 29% renewables added from June 2012 to April 2013, based on “net qualifying capacity”, each megawatt-hour (MWh) of replacement power would emit at least 560 lb. more CO2 than from SONGS. That’s an extra 4 million metric tons of CO2 per year, or 8% of California’s 2010 emissions from its electric power sector and almost 1% of total state emissions. If gas filled the entire gap, or if the natural gas capacity used was not all high-efficiency combined cycle plants, the figure would be closer to 6 million metric tons, equivalent to the annual emissions from about 1.5 million cars.
So far, the state's environmental data supports this conclusion. Although offset by larger imports of low-emission power from out-of-state, there was a noticeable uptick in greenhouse gas emissions from in-state generation from 2013 to 2014. (See Figure 8 in the 2016 California GHG Inventory.)
California will get more renewables either way, but shutting down Diablo Canyon when it still has decades of useful life left represents a net loss to California consumers, PG&E shareholders, and to the global environment.
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Tuesday, June 21, 2016
Thursday, June 16, 2016
Could the Hydrogen Economy Run on Ethanol?
- Plans for a fuel cell car running on ethanol look like a clever way to circumvent the obstacles faced by other fuel cell vehicles.
- However, it is not clear that ethanol's perceived logistical benefits or emissions profile would give Nissan an edge in the competitive market for green cars.
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.
Posted by Geoffrey Styles at 2:06 PM 2 comments:
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