Kevin M. Myles

Oxide-ion conductivity of bismuth aluminates

Abstract Novel compounds in the Bi-Al-O and La-Bi-Al-O systems were prepared and tested for conductivity at high temperatures (500–800°C) in an oxygen gradient cell. The purpose is to develop an electrolyte material that will permit operation of a solid oxide fuel cell at 500–800°C instead of the 1000°C now used. The Bi-Al-O and La-Bi-Al-O compounds were found to have conductivities of about 10 −2 ohms −1 cm −1 and 10 −1 ohms −1 cm −1 at 800°C, respectively, in an oxygen gradient and ma y have the needed conductivity and stability toward humidified hydrogen for use as fuel cell electrolytes.

Fundamentals of fuel cell system in integration

Abstract Fuel cells are theoretically very efficient energy conversion devices that have the potential of becoming a commercial product for numerous uses in the civilian economy. We have analyzed several fuel cell system designs with regard to thermal and chemical integration of the fuel cell stack into the rest of the system. Thermal integration permits the use of the stack waste heat for the endothermic steps of fuel reforming. Chemical integration provides the steam needed for fuel reforming from the water produced by the electrochemical cell reaction. High-temperature fuel cells, such as the molten carbonate and the solid oxide fuel cells, permit this system integration in a relatively simple manner. Lower temperature fuel cells, such as the polymer electrolyte and phosphoric acid systems, require added system complexity to achieve such integration. The system economics are affected by capital and fuel costs and technical parameters, such as electrochemical fuel utilization, current density, and system complexity. At todays low fuel prices and the high fuel cell costs (in part, because of the low rates of production of the early prototypes), fuel cell systems are not cost competitive with conventional power generation. With the manufacture and sale of larger numbers of fuel cell systems, the total costs will decrease from the current several thousand dollars per kW, to perhaps less than US

Reformers for the production of hydrogen from methanol and alternative fuels for fuel cell powered vehicles

100 per kW as production volumes approach a million units per year.

Monolithic solid oxide fuel cell development

The objective of this study was (i) to assess the present state of technology of reformers that convert methanol (or other alternative fuels) to a hydrogen-rich gas mixture for use in a fuel cell, and (ii) to identify the R D needs for developing reformers for transportation applications. Steam reforming and partial oxidation are the two basic types of fuel reforming processes. The former is endothermic while the latter is exothermic. Reformers are therefore typically designed as heat exchange systems, and the variety of designs used includes shell-and-tube, packed bed, annular, plate, and cyclic bed types. Catalysts used include noble metals and oxides of Cu, Zn, Cr, Al, Ni, and La. For transportation applications a reformer must be compact, lightweight, and rugged. It must also be capable of rapid start-up and good dynamic performance responsive to fluctuating loads. A partial oxidation reformer is likely to be better than a steam reformer based on these considerations, although its fuel conversion efficiency is expected to be lower than that of a steam reformer. A steam reformer better lends itself to thermal integration with the fuel cell system; however, the thermal independence of the reformer from the fuel cell stack is likely tomorexa0» yield much better dynamic performance of the reformer and the fuel cell propulsion power system. For both steam reforming and partial oxidation reforming, research is needed to develop compact, fast start-up, and dynamically responsive reformers. For transportation applications, steam reformers are likely to prove best for fuel cell/battery hybrid power systems, and partial oxidation reformers are likely to be the choice for stand-alone fuel cell power systems.«xa0less

Removal of Alkali Vapors by a Fixed Granular-Bed Sorber Using Activated Bauxite as a Sorbent

Abstract The monolithic solid oxide fuel cell performance and fabrication are summarized and specific applications are highlighted for this promising power source.

Calorimetric measurements on electrochemical cells with Pd-D cathodes

Studies have been conducted to develop a fixed granular-bed sorber for the removal of alkali vapors in a pressurized fluidized-bed combustion (PFBC) combined-cycle system. A laboratory-scale pressurized alkali-vapor sorption test unit was used to characterize activated bauxite, the most effective sorbent identified earlier, for its alkali vapor sorption capability in a gas stream with temperature (≤900°C), pressure (10 atm absolute), and composition closely simulating the actual PFBC flue gas. A scale-up of laboratory tests is being conducted in a 15.2-cm-dia (6-in.-dia) PFBC system to demonstrate the granular-bed sorber concept. The NaCl-vapor sorption chemistry of activated bauxite is described. The extent of alkali-vapor evolution from the activated bauxite bed itself is discussed, along with an evaluation of the significance of its alkali vapor contribution to a downstream gas turbine. Details of the design of a high-temperature/high-pressure alkali sorber system for the demonstration of the sorber are presented.Copyright

Development of high-performance Na/NiCl/sub 2/ cell

Two series of experiments were performed to determine the conditions of cell operation that produce sufficient excess heat to be useful for the production of energy. In the first series, the results from a differential temperature analysis of identical light- and heavy-water electrochemical cells were too ambiguous and, thus, not suitable for evaluating excess heat effects. In the second series, two Pd-D/LiOD-saturated D2O/Pt cells were operated at current densities between 12.5–500 mA/cm2 in a constant-heatloss-rate twin calorimeter for 460 hours. Water loss measurements during the experiments indicated that the recombination reaction (2D2 + O2 → 2D2O) did not occur. The D/Pd ratio was determined gravimetrically during the experiments. No excess heat was found within the sensitivity (0.13 W, 0.082 W/cm3 of Pd, 0.013 W/cm2 of Pd) and precision (±0.3 W) of the calorimeter.

Application of the monolithic solid-oxide fuel cell to space power systems

The performance of the Ni/NiCl/sub 2/ positive electrode for the Na/NiCl/sub 2/ battery has been significantly improved by lowering the impedance and increasing the usable capacity through the use of chemical additives and a tailored electrode morphology. The improved electrode has excellent performance even below 200 degrees C and can be recharged within one hour. The performance of this new electrode was measured by a conventional galvanostatic method and by a newly developed power dynamic method. These measurements were used to project the performance of 40- to 60-kWh batteries built with this new electrode combined with the already highly developed sodium/ beta -alumina negative electrode. These calculated results yielded a specific power of 150-400 W/kg and a specific energy of 110-200 Wh/kg for batteries with single-tube and bipolar cell designs. This high performance, along with the high cell voltage, mid-temperature operation, fast recharge capability, and short-circuited failure mode of the electrode couple, makes the Na/NiCl/sub 2/ battery attractive for electric vehicle applications.<<ETX>>

Materials innovations in the development of energy storage systems

The monolithic solid‐oxide fuel cell (MSOFC) is a promising electrochemical power generation device that is currently under development at Argonne National Laboratory. The extremely high power density of the MSOFC leads to MSOFC systems that have sufficiently high energy densities that they are excellent candidates for a number of space missions. The fuel cell can also be operated in reverse, if it can be coupled to an external power source, to regenerate the fuel and oxidant from the water product. This feature further enhances the potential mission applications of the MSOFC. In this paper, the current status of the fuel cell development is presented—the focus being on fabrication and currently achievable performance. In addition, a specific example of a space power system, featuring a liquid metal cooled fast spectrum nuclear reactor and a monolithic solid oxide fuel cell, is presented to demonstrate the features of an integrated system.

Fuel cell system for transportation applications

The principal function of energy storage technology in the energy program is to permit more efficient and more economic use of intermittent energy sources, e.g., solar, wind, and off-peak electrical power, for applications in which there is a mismatch in timing of energy supply and demand. Another important function of energy storage technology is to permit more extensive use of waste heat through efficient heat storage and transport. As in many other parts of the energy program, the development of new and improved materials is a vital if not critical part of the energy storage R&D effort. Examples of key projects in which significant progress has been made recently are media for thermal energy storage, hydrides and containment materials for chemical energy storage, composite materials for flywheels, high current conductors for superconducting magnetic energy storage, and a multitude of new materials for batteries and other electrochemical devices. Special emphasis is now being given to storage components for electric and hybrid vehicles. Batteries with flywheels for regenerative braking offer attractive options for power systems and emerging opportunities for materials R&D specialists.