Exploratory Efforts 2006
Advanced Thermionic Energy Converters
Mark Cappelli, Associate Professor; Nalu Kaahaaina, Research Engineer; Mechanical Engineering, Stanford University
Researchers will perform systems analysis and small-scale experimental performance verification of an optically modulated thermionic energy converter (OMTEC). Thermionic energy converters (TEC) can function as topping cycle devices for combustion systems or serve as the primary heat engine for a solar-thermal system. Current methods to maintain high plasma density between TEC electrodes produce ohmic and scattering loss mechanisms which dramatically affect current density. The work will indicate the feasibility of using a low power, continuous wave diode laser to excite an electronic resonance mode of cesium to produce the dense plasma. This method has the potential to dramatically increase TEC efficiency and power density.
Nanotube Networks as Transparent Electrodes for Solar Cells
Michael McGehee, Assistant Professor, Department of Material Science & Engineering; David Goldhaber-Gordon, Assistant Professor, Department of Physics, Stanford University
This activity explores the use of transparent electrodes made of carbon nanotube (CNT) networks in organic photovoltaics (PVs). CNT-based electrodes have several potential advantages over standard transparent electrodes (such as Indium Tin Oxide) including an extraordinarily large electron mobility, increased contact area, and higher flexibility. This group will study the influence of film roughness on charge collection, film adhesion on the polymer layer, and film work function of the polymer-based PVs. Novel high spatial resolution microscopy techniques will be used to determine limiting factors of film conductivity. The experiments will strive to understand basic causes of low-conductivity found in current CNT films. These measurements will guide the fabrication of future CNT films, as well as provide leads on other forms of graphitic carbon nanostructures that enhance or outperform nanotubes. In addition, the development of scanning probe techniques for the transparent electrodes used here may assist in the investigation of other fundamental processes in excitonic solar cells, such as diffusion and recombination in the active layers.
Integration of Coal Energy Conversion with Aquifer-Based Carbon Sequestration (Stanford University)
R. Mitchell, Associate Professor, Mechanical Engineering, Stanford University
The primary objective of this activity is to begin a collaborative research effort on coal energy conversion using supercritical water conditions with aquifer-based carbon sequestration. The efforts of the Stanford and Brigham Young University/University of Utah groups will be combined to promote synergistic effects between research activities. Exploratory efforts by the Stanford group will include a preliminary thermodynamic analysis of one option of the energy conversion process wherein mass and energy balances for each process unit will be determined along with first and second law efficiencies. Scenarios using either oxygen or hydrogen peroxide as the oxidizer will be compared to determine which is best suited to yield a synthesis gas with the desired properties.
Integration of Coal Energy Conversion with Aquifer-Based Carbon Sequestration (Brigham Young University)
L. Baxter, Professor, Chemical Engineering, D. Tree, Associate Professor, Mechanical Engineering, Brigham Young University
This activity is conducted in parallel with Stanford’s collaborative research project for coal energy conversion. This activity investigates the feasibility of supercritical water coal oxidation and saline aquifer injection of effluents as a means of decreasing global warming impacts from coal-based power generation. A preliminary life cycle analysis will determine system and performance over a range of parameters such as fuel time, operation regime, and injection conditions. Initial thermodynamic models will be developed to predict gas (mainly CO2) solubilities in saline water as a function of temperature and pressure. Additionally computational fluid dynamic models will be developed for preliminary reactor design and facilities specifications.