Papers

AVS2004 Session TS-ThA: Fuel Cells for Clean Power, Hydrogen Storage

Thursday, November 18, 2004 2:00 PM in Room 303D

Thursday Afternoon

Start	Invited?	Item
2:00 PM		TS-ThA-1 Fuel Cells for Clean and Efficient Power Generation S.C. Singhal (Pacific Northwest National Laboratory) Fuel cells provide a low- or no-pollution technology to electrochemically generate electricity at very high efficiencies using a variety of fuels. Use of hydrogen produced from renewable sources as fuel or direct use of biomass-derived fuels in fuel cells for transportation and power generation can contribute significantly to a truly sustainable global economy. In addition, fuel cell-based technologies that include carbon dioxide capture and sequestration are being developed to produce electricity with zero greenhouse gas emissions even with the use of hydrocarbon fuels. Several types of fuel cells have been under development in the last three decades for clean and efficient power generation; most prominent among these are the proton exchange membrane (PEM) and the solid oxide (SOFC) fuel cells. This presentation reviews the materials and performance of these two types of fuel cells and discusses the differences between them, particularly with respect to the fuel requirements. Status of these two types of fuel cells and key challenges associated with materials and electrochemistry are discussed, and directions for future research and development are presented.
2:40 PM		TS-ThA-3 Hydrogen Storage-A Critical Challenge to the Hydrogen Economy R.H. Jones (Pacific Northwest National Laboratory) Vehicle range on a single tank of hydrogen is critical for the economic viability of hydrogen fueled vehicles. A range of 500 kilometers is projected for economic viability and this requires the storage of 4 kg of H₂. Compressed H2 tanks with a capacity of about 2 kg of H₂ stored at 350 bar of pressure have been certified while tanks with higher capacity stored at 700 bar are being developed. Liquidified H2 tanks can store more H₂ in a vehicle than compressed H₂ but liquifying H₂ requires considerable energy and boil-off of the liquid H₂ is a concern, especially in enclosed spaces. Storage of H₂ in bulk hydrides or on the surface of carbon or boron nitride nanotubes are attractive because of the low pressures involved. Recent studies have shown that NaAlH₄ can be reversibly charged and discharged with H2 100’s of times but the capacity of this hydride material is only about 1/2 of that needed. Storage of H2 on the surfaces of carbon nanotubes has shown great promise but verification of the storage capacities has not occurred. However, carbon nanotubes have the potential to store about 80% of the desired quantity of H₂ so it remains a viable storage material. Generation of H₂ by chemical reaction of a hydride such as LiH with water to produce H₂ is also attractive because of the significant amounts of H₂ that can be generated by this process. The key issues for this process of generating H₂ is the need to reprocess the reaction products and the cost associated with transportation and reprocessing this product. There are several options for storing hydrogen on-board a vehicle but as summarized above considerable development work is needed before the hydrogen economy can be realized. Critical materials issues associated with H₂ storage will be presented.