Separator development and testing of nickel-hydrogen cells

The components, design, and operating characteristics of Ni-H2 cells batteries were improved. A separator development program was designed to develop a separator that is resistant to penetration by oxygen and loose active material from then nickel electrode, while retraining the required chemical and thermal stability, reservoir capability, and high ionic conductivity. The performance of the separators in terms of cell operating voltage was to at least match that of state-of-the-art separators while eliminating the separator problems. The separators were submitted to initial screening tests and those which successfully completed the tests were built into Ni-H2 cells for short term testing. The separators with the best performance are tested for long term performance and life

Polyvinyl alcohol membranes as alkaline battery separators

Polyvinly alcohol (PVA) cross-linked with aldehyde reagents yields membranes that demonstrate properties that make them suitable for use as alkaline battery separators. Film properties can be controlled by the choice of cross-linker, cross-link density and the method of cross-linking. Three methods of cross-linking and their effects on film properties are discussed. Film properties can also be modified by using a copolymer of vinyl alcohol and acrylic acid as the base for the separator and cross-linking it similarly to the PVA. Fillers can be incorporated into the films to further modify film properties. Results of separator screening tests and cell tests for several variations of PBA films are discussed

Design principles for nickel-hydrogen cells and batteries

Nickel-hydrogen cells and, more recently, bipolar batteries have been built by a variety of organizations. The design principles that have been used by the technology group at the NASA Lewis Research Center draw upon their extensive background in separator technology, alkaline fuel cell technology, and several alkaline cell technology areas. These design principles have been incorporated into both the more contemporary individual pressure vessel (IPV) designs that were pioneered by other groups, as well as the more recent bipolar battery designs using active cooling that are being developed at NASA Lewis Research Center and under contract. These principles are rather straightforward applications of capillary force formalisms, coupled with the slowly developing data base resulting from careful post test analyses. The objective of this overall effort is directed towards the low-Earth-orbit (LEO) application where the cycle life requirements are much more severe than the geosynchronous-orbit (GEO) application. A summary of the design principles employed is presented along with a discussion of the recommendations for component pore sizes and pore size distributions, as well as suggested materials of construction. These will be made based on our experience in these areas to show how these design principles have been translated into operating hardware

Initial performance of advanced designs for IPV nickel-hydrogen cells

Advanced designs for individual pressure vessel nickel hydrogen cells were conceived which should improve the life cycle at deep depths of discharge and improve thermal management. Features of the designs which are new and not incorporated in either of the contemporary cells (Air Force/Hughes, Comsat) are: (1) the use of alternate methods of oxygen recombination, (2) use of serrated edge separators to facilitate movement of gas within the cell while still maintaining required physical contact with the wall wick, and (3) use of an expandable stack to accommodate some of the nickel electrode expansion. The designs also consider electrolyte volume requirements over the life of the cells, and are fully compatible with the Air Force/Hughes design

Cross-linked polyvinyl alcohol films as alkaline battery separators

Cross-linking methods were investigated to determine their effect on the performance of polyvinyl alcohol (PVA) films as alkaline battery separators. The following types of cross-linked PVA films are discussed: (1) PVA-dialdehyde blends post-treated with an acid or acid periodate solution (two-step method) and (2) PVA-dialdehyde blends cross-linked during film formation (drying) by using a reagent with both aldehyde and acid functionality (one-step method). Laboratory samples of each cross-linked type of film were prepared and evaluated in standard separator screening tests. The pilot-plant batches of films were prepared and compared to measure differences due to the cross-linking method. The pilot-plant materials were then tested in nickel oxide - zinc cells to compare the two methods with respect to performance characteristics and cycle life. Cell test results are compared with those from tests with Celgard

Risk-Based Decision Making Model for the Selection of Flood Mitigation Alternatives

In recent years, there has been a noticeable increase in the frequency of natural disasters such as wildfires, hurricanes and flooding, resulting in big economic, environmental, and social impacts. In the case of flood events, impacts such as community anxiety, loss of life, water pollution, and contamination of agricultural land have been found to be equally, if not more important, than the economic impacts of such events. Nevertheless, the literature shows that flood risk assessment studies incorporating economic, environmental, and societal impacts are limited. In addition, flood mitigation measures are typically compared focusing on economic criteria and not considering stakeholders or the implementation characteristics of the flood mitigation alternatives. This study proposes a holistic framework for watershed flood management that considers economic, social, environmental, and implementation criteria for selecting among flood mitigation alternatives. First, a spatial flood risk assessment framework capable of integrating economic, social, and environmental impacts is introduced in order to assess the possible losses and risks within the communities of a watershed. The risk assessment uses HAZUS software from the Federal Emergency Management Agency (FEMA) and is executed for five different return periods. Second, in order to select from multiple mitigation alternatives, a Decision-Making Models (DMM) is proposed. The first model uses the results from the risk assessment and the mitigation alternatives are evaluated using a Monte Carlo Simulation and probabilistic optimization. The second DMM model incorporates stakeholders characteristics and opinions using stakeholder theory, network analysis, and the Analytical Hierarchical Process (AHP). Two surveys were developed and deployed to public officials of agencies involved in the planning and implementation of flood mitigation alternatives and to the community, respectively. Along with this information, technical aspects of the flood mitigations alternatives are used as implementation criteria. Three alternatives were evaluated in the decision analysis: (1) no action, (2) flood warning system, and (3) levee. The framework is demonstrated with the case study of the Upper Río Grande of Loíza Watershed in the Commonwealth of Puerto Rico. The results showed that both stakeholder\u27s input and implementation criteria can have a significant impact when selecting among flood mitigation strategies. For the case study, when considering economic, social, and environmental criteria, the \u27Levee\u27 was the alternative that minimized the flood risks. The developed framework was shown to be easily implementable and adaptable to Decision-Maker (DM) requirements. In summary, the model can provide DMs with the information they need in order to forecast the flood risks of a community and study the effects of the mitigation alternatives to be implemented. These results could be used for budget forecast, resource allocation and for establishing flood management priorities for a watershed.\u2