Warning: techno-engineering speak ahead
Amory Lovins is rightfully admired by environmentalists. But nobody is right all the time, and the hydrogen path is one of his few mistakes. He summarizes his argument for hydrogen in Twenty Hydrogen Myths (PDF). More extensive discussion is embedded in his book Winning the Oil Endgame (book-length PDF).
His basic proposal:
Since most gas stations already have access to natural gas, put natural gas reformers in enough stations to make sure everyone has access to hydrogen within 25 miles. For stations without natural gas, they can reform hydrogen from LPG or ethanol — or use off peak electricity.
Build hypercars to run on this hydrogen. (Hypercars combine carbon fiber or other low-weight body design, electric drive, aerodynamic design to reduce wind resistance, and low rolling resistance tire to make them much more efficient than conventional cars of the same weight.) According to Amory, gas-powered hypercars run about three times more efficiently than conventional gasoline vehicles, while hydrogen-powered hypercars use about one fifth the BTUs (in hydrogen fuel) per mile that a conventional car of the same size does. (He also points out that while running a conventional automobile on hydrogen would require absurdly expensive fuel cells and storage, the small average and peak power requirements of a hydrogen hypercar would allow it to be made at the same price or less than an conventional car — if the fuel cells were mass produced.) So you pay more for the fuel, but get five times as many miles out of each unit — thus coming out ahead.
What about carbon? Lovins points out that running our cars this way, even with carbon released by natural gas reformers, yields lower carbon than our existing automobiles. But he also suggests we can attain truly low-carbon transport either by using wind electricity transmitted over long high-voltage lines to electrolyze water, or by building carbon pipelines to ship the CO2 from natural gas to sequestration sites. (This makes sense compared to usual hydrogen advocates. CO2 is a lot less expensive to ship than hydrogen.)
What is wrong with all this? To start with, system efficiency of hydrogen hypercars is not five times the system efficiency of gas-powered hypercars. Reasonably priced reformers for converting natural gas to hydrogen recover about 70%-75% of the energy in the natural gas. While fuel cells with high efficiency can be built, the ones that currently could be mass produced for $200-$250 per KW average 50% to 55%.
That gives an overall system efficiency of 35%-41%. Applied to natural gas with 20% less carbon content than oil, that means cars fueled by natural gas without sequestration will put about half the carbon into the air conventional cars do — if that was the end of the story. However, natural gas requires a lot less energy to transport and refine than oil. Overall, therefore, hypercars powered by hydrogen from natural gas may (at best) break even on carbon emissions with hypercars powered by gasoline. We can do better.
Hypercars powered by batteries and charged from our current grid can get almost four times as many miles from a unit of fossil fuel as conventional cars. If the grid were converted to mainly wind and sun, eliminating thermal losses would increase that efficiency advantage to eight times conventional automobiles.
Lovins dismisses electric cars as “cars for carrying mainly batteries — but not very far and not very fast.” But he is making the same mistake some of his less informed critics make with hydrogen cars — not taking into account the lower power needs of more efficient vehicles. He is also making a system analysis error — not taking into consideration the number of miles most people actually drive. A hypercar powered with NiMH batteries of the sort often used in conventional hybrids will have a 200 mile range. That is not as great as the 400+ miles a conventional car gets on a tank of gas. But half the population never drives more than 40 miles a day total. And a huge percent never drives more than 200 miles in a single day.
For the five to ten percent of the population who did not find that a sufficient range, we could make plug-in hybrid hypercar electric vehicles (PHHEV) comparable to PHEV (plug-in hybrid electric vehicles). One could drive the first 60 miles or so on battery, at 90-200 mpg carbon equivalent (depending on how decarbonized the grid was), and drive any remaining distance on biofuel — ethanol or biodiesel (though there are good reasons a hypercar might not use the latter). With an automobile/light truck fleet of mostly EV hypercars, plus a few PHEV hypercars, we could reduce fuel use in the passenger fleet by 95% to 99%. Biofuels use could be quite sustainable in that quantity.
(To get the lower number, we would need to encourage use of true EVs. Again, we need to use Lovins’ own type of system analysis. Of people who need a range of more than 200 miles, most need it seldom — for vacations and such. Put in incentives for those people to own EVs and rent PHEV hypercars for occasional use.)
Let’s look more closely at the means Lovins suggests for completely decarbonized hydrogen.
If you remember, one proposal was to pipe the carbon to someplace where it could be sequestered. This would increase the cost and lower the system energy efficiency of hydrogen still further.
Alternatively he suggests using wind-generated electricity. Well, up until the plug, system efficiencies for hydrogen and battery power are identical in this scenario. But round-trip efficiency of electricity from plug to battery and out again to drive the car is 70% to 75% (compared to 35% – 45% for near-term hydrogen).
Of course more research could lower the cost of fuel cells and improve sequestration technologies — probably quite quickly. But then again, more research could probably lower the cost of lighter batteries with longer lifecycles too.
In short, both hydrogen- and battery-powered cars could be produced and fueled on a large scale with today’s technology at a price comparable to today’s cars; both would benefit from likely improvements. But battery power would be less expensive and help lower carbon use faster; battery power would also use electricity from a decarbonized grid more effectively than hydrogen.
Both would require infrastructure improvements. A hydrogen path would require reformers or electrolyzers in gas stations (along with carbon pipelines for the former, or long-distance transmission lines to allow wind to fuel the latter). An electric car path would require chargers in garages and in rental unit and residential street parking. (Chargers at work and while shopping would be nice, but not absolutely necessary, since charging while you sleep will take care of most people’s needs, and charging with off-peak power puts less strain on the grid in any case. Put the basics in and the market probably will take care of demand beyond that. Please note that capacity for this appears to be available, and we want to replace our existing generation with renewable sources as quickly as possible in any case.)
Although this post focuses mainly on the automobile and light truck fleet, I will briefly cover other issues:
- Buildings are one of the many things Amory is 100% right on. There are a large number of ways we can improve efficiency in both existing and new buildings. This applies to appliances as well. Decarbonization of the grid will also contribute greatly to reducing carbon emissions in residential and commercial buildings. While hydrogen does not make sense in cars, it probably does make sense in buildings. In cold climates, in residential buildings, waste heat from fuel cells could provide hot water and space heating. In warm climates, you can similarly drive chillers with waste heat. This shrinks the efficiency differences between hydrogen and battery storage. Some of the flow battery storage I suggested for a wind powered grid could be replaced by such hydrogen systems — at lower capital costs if a large capacity was need. (You need to add more flow batteries to add capacity to a flow battery-based system; hydrogen need only be sized for peak use — additional capacity is added by installing more hydrogen storage. So in buildings, where you can use almost all of the hydrogen energy with combined heat and power systems, the capital costs can make up for shrunken difference in storage losses. For this to work, you might need thermal mass (possibly in the form of PCM or natural zeolite thermal storage) so that the waste heat could be time shifted to when needed.)
- The best thing we can do with heavy trucks is replace most freight-ton truck miles with freight-ton rail miles. Beyond this, most of Lovins’ suggestions for improving truck efficiency (PDF) in Winning the Oil Endgame make sense. These include regulatory changes, better feedback, and technical improvements. One technical improvement he overlooks that can easily be retrofitted into existing engines is the injection of about 10% propane or CNG into the engine. Diesel fuel that is normally not burned is consumed — improving mileage and decreasing emissions by at least 30%. (This would work with hydrogen as well.)
- As Lovins says, medium trucks can use either the same technology as heavy trucks or the technology light vehicles use.
- Lastly, dealing with industry, Amory is right on efficiency. Various means can cut industrial power consumption a good deal. Much of what remains can be switched partially or entirely to electricity. (Many industrial process that are fundamentally not electrical in nature can be replaced by others that accomplish the same thing. For example, electric arc furnaces process most scrap steel these days.) What remains could run on biofuels — or even hydrogen, if the waste heat can be fully utilized.
As you can see, there is a place for hydrogen. But until costs are lowered and system efficiency improved, that place is where the hydrogen can be generated where consumed, and almost all the waste heat used, and where it is cost competitive with other means of electricity storage even after carbon disposal costs are counted.