Hydrogen Economy - An Opportunity for Chemical Engineers?

Fossil fuels have provided a convenient and plentiful energy source, and have been used profitably in all sectors of the global economy. However, continued reliance on fossil resources must take note of, and may even be placed in jeopardy by several factors. First, worldwide oil demand continues to increase, and replacing the produced oil is technically and politically demanding and very capital intensive. Second, known fossil reserves are concentrated in only a few regions of the world. Oil and natural gas reserves, in particular, are in regions geographically separate from those undergoing the most rapid economic growth. Third, the widespread use of oil in the transportation sector contributes to environmental disturbances, such as air pollutants and CO2. Various demand-side solutions have been proposed to address the continued, increasing reliance on oil. The perennial solution of improving energy efficiency by way of vehicle fuel economy would curb demand for oil. Major auto manufacturers have entered the hybrid electric vehicle market. Hybrids and fleet-wide fuel economy standards may reduce the growth of oil demand, but fuel substitution in the transportation sector offers another type of solution. One such possibility is the widespread adoption of light-duty electric vehicles (EVs), which could displace substantial oil demand, but which will depend on successful research and development (R&D) on high-energy density battery technology. Also, if the electricity is produced from coal, there is potential for increased CO2 emissions. Another possible fuel substitution and end-use combination is the hydrogen (H2) fuel-cell vehicle (FCV). The major automakers have rolled-out H2-fueled concept cars coupled to proton exchange membrane (PEM) propulsion systems. As with EVs, there remain substantial cost and technological barriers to the commercial deployment of FCVs. While there are strong supporters of H2, it also invokes strong reactions from those who believe that H2 is unlikely to meet the requirements of an alternate energy source.1,2 These differences in opinion stem from the fact that like electricity, H2 is simply an energy carrier. Despite its abundance in nature, H2 is not available in the free form and must be produced from another energy source. Moreover, H2 needs to be transported, delivered and stored at the point of end use. All these steps can potentially consume energy. Use of H2 as an energy carrier is pollution-free and efficient as long as all the steps involved in its production, transportation and use chain are also pollutionfree and efficient. Moreover, for H2 to be a long term alternative, it must be produced from an energy source whose supply is unlimited or sufficiently abundant to last for centuries. The nonbelievers in the H2 economy conclude that the supply and use chain of H2 is more inefficient, costly and, furthermore, it is generally more polluting if H2 were to be produced from a fossil fuel. This article will focus on the key barriers to assembly of an H2 infrastructure, and the pros and cons associated with various methods of producing inexpensive H2. In the long-term, H2 could be produced in large, central plants and delivered via pipelines to filling stations. In transition to this end-state, a system of distributed production sites, i.e., small production units located at filling stations-could obviate the need for Correspondence concerning this article should be addressed to R. Agrawal at agrawalr@purdue.edu. The opinion expressed in this article does not necessarily reflect those of RA’s previous employer – Air Products and Chemicals.