Hydrogen and Transportation
The transportation sector presents unique challenges to modeling and analysis. Because so much of the cost of providing transportation services is attributable to non-energy costs, the development of new technologies for this sector is crucial to any cost-effective strategy to address the risks of climate change. The transportation sector is today almost entirely dependent on the direct combustion of fossil fuels (with high levels of greenhouse gas emissions). Transforming the core technology of this sector from one that is freely emitting to one that is carbon-free represents an immense challenge. Furthermore, the transportation system is a set of interrelated technologies rather than a single technology. The provision of transportation services entails the production of primary energy, transport of primary energy forms, the refinement of primary energy forms into usable fuels, storage and transport of fuels to the point of distribution, the distribution system, the vehicles which employ the fuels, and the infrastructure which supports the vehicles, and, in a carbon-constrained world, another set of systems to move carbon.
The transition to a transportation sector less dependent on carbon based fuels is already underway with automakers now marketing hybrid electric and gasoline powered cars like this Toyota Prius.
The PNNL team has already begun the process of developing a transportation module that incorporates a set of components appropriate to assessing the demand for and supply of transportation services. It disaggregates transportation services into freight and passenger. It models the competition among the variety of modes of transport within each of these markets, and it links those modes to their associated final-energy markets. For example, a conventional passenger vehicle is modeled as an investment in capital that provides mobility services to its owner. The cost of mobility, however, is more than just the cost of capital, operation and maintenance cost and fuel for any specific vehicle type or mobility model. Because the efficiency of transport (in terms of elapsed time) becomes increasingly valuable with higher income levels, different modes of transport gain and loose market share with changing incomes. This module is complete for the United States, but needs to be extended to the rest of the world. For much of the world today, the transition may be from non-motorized to motorized transportation systems.
There are many ways advanced transportation technology can affect greenhouse gas emissions. One of the most interesting is the development of vehicles that employ hydrogen as a fuel source. While this is usually thought to imply the use of fuel cells (Kinsey et al. 1998) hydrogen could also be used in an internal combustion engine. But a hydrogen economy requires a source of hydrogen, a mechanism for its transport and distribution, and in a carbon-constrained world, a means of controlling the emissions of any associated carbon. Since fossil hydrocarbons presently appear to be the cheapest source of hydrogen, their employment would provide both a new market for fossil fuels and a substantial source of carbon.
The GTSP team is beginning an examination of all of the potential pathways by which a hydrogen economy could come into being. The integrated assessment model framework will be extended to include the detail of a hydrogen market and related interactions with other energy markets, with hydrogen supplies potentially produced using fossil fuels, commercial biomass or electrolysis. The employment of commercial biomass in conjunction with carbon capture and disposal creates a technology combination with negative emissions of carbon, i.e., that technology combination would effectively scrub carbon from the air. The model is set up to readily address demands for hydrogen derived both from the demand for transportation services and the demand for residential and industrial services. It already contains technology options for the capture and disposal of carbon. As a consequence, very substantial progress can be anticipated in GTSP Phase II in understanding pathways by which hydrogen could enter the economy and the technology and cost requirements for that to happen. Much of the future work will focus on developing more detailed descriptions of potential system configurations and their associated costs. An important area of research will be to understand the timeframes and costs at which advanced technologies may realistically transition into existing or developing transportation infrastructures, in the US and in different regions of the world. A significant challenge is to understand and be able to articulate how the present transportation systems of the world may evolve.