There is much agreement that hydrogen is the probable energy carrier of the future—there is little agreement on how exactly that hydrogen will come to be. Unlike wood, coal or petroleum, hydrogen isnt sitting waiting to be harvested, mined or pumped. Rather, it needs to be produced.
The diagram at the right (Click to enlarge) illustrates the major pathways of hydrogen production. The vast majority of current hydrogen (which is not an insignificant amount, used for making ammonia, for petroleum fuels production, and other industrial uses) currently comes from fossil (hydrocarbon) fuels: natural gas, oil itself, and coal. Basically, the gas is produced by splitting the hydrogen out of the original hydrocarbon structure (and then somehow disposing of the leftover carbon).
In cleaner scenarios, the carbon would be sequestered; in other scenarios, it is an exhaust gas (CO2) that would contribute to climate change.
Biomass is a possible feedstock for hydrogen. The other primary hydrogen feedstock could be water: H2O. The only current production method based on water as a feedstock that even registers on a global scale is electrolysis: the use of electricity to split the hydrogen and oxygen.
Using water to generate hydrogen is capturing a great deal of research interest, particularly in association with renewable sources of energy to fuel the production process, and particularly for more distributed production of the gas. (Generating hydrogen right at the fueling station, in other words, rather than trucking it in from a mega refinery. An example of this in practice is the electrolysis station BP plans to build in Singapore as part of its trial.)
There is work on using sunlight (photolysis) to generate hydrogen from water, either through organic means or through electrochemical. There is also work on thermo-chemical means—using extreme heat, produced from sources such as solar or nuclear energy, along with chemical catalysts. (Earlier post on a solar thermo-chemical process here.)
So where to place your bets? On multiple sources. James Winebrake from RIT gave a terrific background presentation on hydrogen basics to a DOE workshop in June. (Slides here.)
As an example, how could we fuel half of the current LDV fleet with hydrogen?
- Current consumption in the light-duty market is 16 quads [a quad is one quadrillion BTUs—the energy of approximately 8 billion gallons of gasoline]
- Assume a 2x increase in efficiency with hydrogen fuel cell vehicles
- For half of the fleet, we need 4 quads
- This is about 40 million tons of hydrogen per year (4 times the current domestic hydrogen production)
Using only ONE domestic resource, can we make this much hydrogen?
For 40 million tons/year of hydrogen, we would need:
95 million tons of natural gas (current consumption is around 475 million tons/year in all energy sectors)
310 million tons of coal (current consumption is around 1,100 million tons/year)
400-800 million tons of biomass (availability is 800 million tons/year of residue plus potential of 300 million tons/year of dedicated energy crops with no food, feed or fiber diverted)
The wind capacity of North Dakota (class 3 and above)
3,750 sq. miles of solar panels (approx. footprint of the White Sands Missile Range)
In other words—on any useful scale, hydrogen for transportation is going to come from more than one source. (And that doesnt address transportation or storage.)Pragmatically, what this means as we build up to a hydrogen platform, assuming thats the winner that will emerge, is that we will have expanded dependence on natural gas. If there is a natural gas supply and price crunch as some foresee, that will result in additional emphasis being placed on coal as a source of hydrogen.
From a power generation point of view, the problem with electrolysis in the short term is that it would rely primarily on fossil fuels (coal, natural gas) to generate the electricity to split the water. Its when renewable electricity generation comes to play (wind, solar, hydro) that the whole scene starts looking really green.
Im looking to the trials, and especially to the mini-neworks proposed by Jeremy Bentham to provide some field perspective on what works and what doesnt in hydrogen generation and fueling. And Im looking to the researchers in biotech and nanotech to discover more efficient means for bio- and solar-generated H2.
The vision of the distributed hydrogen economy is compelling; it will just take awhile to get there on a mass scale. In the meantime, we have emissions and energy supply issues that we must address through a variety of solutions, tactical and strategic. One danger in this whole arena is siloing—getting so wrapped up in one particular avenue or discipline that one becomes blind to everything else. This is a complex arena, requiring solutions from multiple fields. The trials and the mini-networks are excellent mechanisms for gathering data, but those results should be shared broadly.