Bulletin of the American Physical Society
APS April Meeting 2013
Volume 58, Number 4
Saturday–Tuesday, April 13–16, 2013; Denver, Colorado
Session J6: Invited Session: Low Carbon Transportation |
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Sponsoring Units: GERA FPS Chair: Valerie Thomas, Georgia Institute of Technology Room: Governor's Square 15 |
Sunday, April 14, 2013 1:30PM - 2:06PM |
J6.00001: Electricity as Transportation ``Fuel'' Invited Speaker: Michael Tamor The personal automobile is a surprisingly efficient device, but its place in a sustainable transportation future hinges on its ability use a sustainable fuel. While electricity is widely expected to be such a ``fuel,'' the viability of electric vehicles rests on the validity of three assumptions. First, that the emissions from generation will be significantly lower than those from competing chemical fuels whether `renewable' or fossil. Second, that advances in battery technology will deliver adequate range and durability at an affordable cost. Third, that most customers will accept any functional limitations intrinsic to electrochemical energy storage. While the first two are subjects of active research and vigorous policy debate, the third is treated virtually as a given. Popular statements to the effect that ``because 70{\%} of all daily travel is accomplished in less than 100 miles, mass deployment of 100 mile EVs will electrify 70{\%} of all travel'' are based on collections of one-day travel reports such as the National Household Travel Survey, and so effectively ignore the complexities of individual needs. We have analyzed the day-to-day variations of individual vehicle usage in multiple regions and draw very different conclusions. Most significant is that limited EV range results in a level of inconvenience that is likely to be unacceptable to the vast majority of vehicle owners, and for those who would accept that inconvenience, battery costs must be absurdly low to achieve any economic payback. In contrast, the plug-in hybrid (PHEV) does not suffer range limitations and delivers economic payback for most users at realistic battery costs. More importantly, these findings appear to be universal in developed nations, with labor market population density being a powerful predictor of personal vehicle usage. This ``scalable city'' hypothesis may prove to a powerful predictor of the evolution of transportation in the large cities of the developing world. [Preview Abstract] |
Sunday, April 14, 2013 2:06PM - 2:42PM |
J6.00002: SUNgas: Thermochemical Approaches to Solar Fuels Invited Speaker: Jane Davidson Solar energy offers an intelligent solution to reduce anthropogenic emissions of greenhouse gases and to meet an expanding global demand for energy. A transformative change from fossil to solar energy requires collection, storage, and transport of the earth's most abundant but diffuse and intermittent source of energy. One intriguing approach for harvest and storage of solar energy is production of clean fuels via high temperature thermochemical processes. Concentrated solar energy is the heat source and biomass or water and carbon dioxide are the feedstocks. Two routes to produce fuels using concentrated solar energy and a renewable feed stock will be discussed: gasification of biomass or other carbonaceous materials and metal oxide cycles to produce synthesis gas. The first and most near term route to solar fuels is to gasify biomass. With conventional gasification, air or oxygen is supplied at fuel-rich levels to combust some of the feedstock and in this manner generate the energy required for conversion to H$_{2}$ and CO. The partial-combustion consumes up to 40{\%} of the energetic value of the feedstock. With air combustion, the product gas is diluted by high levels of CO$_{2}$ and N$_{2}$. Using oxygen reduces the product dilution, but at the expense of adding an oxygen plant. Supplying the required heat with concentrated solar radiation eliminates the need for partial combustion of the biomass feedstock. As a result, the product gas has an energetic value greater than that of the feedstock and it is not contaminated by the byproducts of combustion. The second promising route to solar fuels splits water and carbon dioxide. Two-step metal-oxide redox cycles hold out great potential because they the temperature required to achieve a reasonable degree of dissociation is lower than direct thermal dissociation and O$_{2}$ and the fuel are produced in separate steps. The 1$^{st}$ step is the endothermic thermal dissociation of the metal oxide to the metal or lower-valence metal oxide. The 2$^{nd}$ exothermic step is the hydrolysis of the reduced metal to form H$_{2}$ and the corresponding metal oxide. Two promising options for 2-step cycles, the Zn/ZnO and non-stoichiometric ceria redox cycles, will be compared with a focus on efficiency and state of the art achievements. [Preview Abstract] |
Sunday, April 14, 2013 2:42PM - 3:18PM |
J6.00003: Biofuels and technology/policy tradeoffs for light-duty vehicles Invited Speaker: Todd West |
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