Objective

Integrating carbon sequestration objectives into traditional agricultural practices has the potential to provide dramatic short-term offsets in carbon emission. Managed wetlands, rice paddies in particular, represent a promising distributed carbon sink; if the average carbon content within the upper meter were increased by a few percent, the total annual carbon dioxide release from the burning of fossil fuels could be offset. It is conceivable that we could double the carbon content over a ten-year period, reaching an average total soil carbon content of 4-8%. This project will test the hypothesis that microbial methanogenesis can be minimized while simultaneously limiting carbon mineralization rates through control of water levels, periods of inundation, rates of both flooding and draining, and specific iron(III) mineral availability within rice paddies. The objectives of the exploratory study are: 1. to examine current organic carbon and iron mineral phase contents within existing wetlands under different historic management practices; and 2. to conduct a pilot study wherein the operative microbial metabolisms are controlled to limit carbon mineralization rates (relative to aerobic rates) while restricting methane production.

Objective
This project explores a novel photovoltaic cell architecture using a network of PbSe nanowires combined with PbS nanocrystals. The aim of this project is to use the proposed structure to achieve both high photon absorption through impact ionization processes in the nanocrystals, and efficient charge transport through both the nanowire network and the nanocrystal arrays filling the void space in the nanowire scaffold. This concept is a new approach to the realization of high-efficiency thin film photovoltaics, and will require the exploration of fundamental questions, many of which will also benefit other innovative thin film technologies.

Objective
This study explores innovative approaches for using zinc-based oxide materials as transparent conductive films in photovoltaic devices. The proposed strategy consists of depositing a planar network of doped ZnO nanowires from solution and annealing it by laser to form a continuous film. This approach promises better conductivity and transparency properties than in unannealed nanowire networks, in addition to the advantages associated with solution processing. Laser annealing of highly-doped ZnO nanowires is a novel technique that will be investigated for the first time in this project.

Investigator
Mark A. Cappelli, Mechanical Engineering, Stanford University

Objective
In this project, the effects of plasma injection on the operation of a fuel cell will be studied. A nonequilibrium plasma will be generated in the inlet gases of the fuel cell via dielectric barrier discharge. Ionized gas-phase species may alter the reaction pathways at the catalytic solid-gas interface in a way that affects significantly the activation losses. Through bench top experiments and systems-level modeling, this research will determine whether the resulting change in operational efficiency can overcome the power needed to generate the plasma. The applications of plasma to fuel cells extend beyond mere efficiency gains; plasma enhancement may also be used simultaneously for internal fuel reforming.

Investigator
Fritz B. Prinz, Mechanical Engineering and Materials Science and Engineering, Stanford University

Objective
This project envisions solar conversion systems where light is converted to electricity via charge separation and transfer through a solid-state electrolyte. The latter occurs through an ultra-thin solid state electrolyte which is capable of conducting redox couples that carry both positive and negative charges without allowing them to recombine within the confinements of the film electrolyte.

To effectively screen feasible material alternatives for this project, efficient computational tools are needed for the down selection process. Therefore this project also aims to develop a computational tool to calculate the electronic structure including the band gap of nano-scale devices with practical computational resources. The simulation tool under development will use a tight binding method that is shown to be fast enough to evaluate relevant systems with reasonable accuracy.

Objective
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.

Objective
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.

Objective
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.

Objective
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.