Hydrogen: An End-State Solution for Transportation?

Abstract

There is presently no global consensus on how our human society might ultimately transform from a hydrocarbon, fossil fuel-based energy economy to an alternative low-carbon, or zero-carbon economy. The same is true for alternative fuel options for transportation. Hydrogen fuel cell vehicles are highly promising in that their well-to-wheel carbon dioxide profile is very good and compare favorably against either battery electric vehicles or plug-in hybrid electric vehicles, since many national energy grids (e.g. China and the USA) are so dirty. These fuel cell vehicles have ranges similar to gasoline vehicles, e.g. the Honda Clarity has a range of some 250 miles. In that regard, many countries view the development and dissemination of hydrogen and fuel cell technologies as core technologies for a future sustainable economy which could contribute to environmental impact reduction, energy diversity and energy independence as well as new industry creation. However, the attraction of “competitor” electric vehicles is that much of the underlying infrastructure and technology already exists; national grids are in place with the right support infrastructure for scale-out across countries. When it comes to hydrogen, this is simply not the case. It is clear that this alternative technology is not yet ready for mass market and the infrastructure is not in place to support these vehicles. Thus the economics of a transition is difficult. These types of considerations led the US, for example, in 2009 to announce a significant reduction in research and development funding into automotive hydrogen fuel cells, arguing that a focus on areas such as plug-in vehicles has the potential to make the quickest impact on environmental issues. However, the long-term potential of hydrogen fuel cells is recognized while understanding the pressing scientific and technological and socio-economic challenges. As well as the vexing issue of the absence of any national infrastructure for hydrogen, these challenges center on the cost and durability of vehicle fuel cells; the current inability to store large volumes of hydrogen fuel onboard transport vehicles and the absence of large-scale processes to the manufacture of carbon-free hydrogen. In part of our contribution, we present a brief overview on the current states of hydrogen and fuel cell technologies, covering several of the key challenges of what one might see as a future hydrogen economy. But we stress that hydrogen can also fulfill an even broader, pivotal role in renewable energy capture and conversion. A variety of renewable or sustainable energy sources can be used to produce molecular hydrogen, which can then be used in multiple energy applications: as a fuel for personal transportation, in the conventional vision of a hydrogen transport economy; as an energy store in static applications, particularly as a buffer in energy generation; or in a fuel, using hydrogen as a feedstock in the synthesis of oxygenated fuels such as methanol or ethanol or even hydrocarbon fuels such as diesel. This complementary approach of using hydrogen for the synthesis of hydrocarbon-based liquid fuels at-a-stroke removes the burgeoning requirement noted earlier for large-scale infrastructure changes that are necessary in the use of molecular hydrogen as a fuel. Furthermore, the use of carbon dioxide (atmospheric or industrial by-product) as the source of carbon for the synthesis of liquid hydrocarbon fuels with hydrogen has the potential to reduce emission of fossil carbon into the atmosphere. Hydrogen generation as a buffer or energy store, using energy that would otherwise not be matched to load in the electricity grid, can be regarded as a potential key ally of renewable energy generation from intermittent natural sources including wind, wave, tide and solar power. Scientists and policy-makers should thus keep in mind a variety of possible “hydrogen economies”.