Degradation in PEM Fuel Cells and Mitigation Strategies Using System Design and Control

The rapid miniaturization of electronics, sensors, and actuators has reduced the cost of field sensor networks and enabled more functionality in ever smaller packages. Networks of field sensors have emerging applications in environmental monitoring, in disaster monitoring, security, and agriculture. Batteries limit potential applications due to their low specific energy. A promising alternative is photovoltaics. Photovoltaics require large, bulky panels and are impacted by daily and seasonal variation in solar insolation that requires coupling to a backup power source. Polymer electrolyte membrane (PEM) fuel cells are a promising alternative, because they are clean, quiet, and operate at high efficiencies. However, challenges remain in achieving long lives due to catalyst degradation and hydrogen storage. In this chapter, we present a design framework for high-energy fuel cell power supplies applied to field sensor networks. The aim is to achieve long operational lives by controlling degradation and utilizing high-energy density fuels such as lithium hydride to produce hydrogen. Lithium hydride in combination with fuel-cell wastewater or ambient humidity can achieve fuel specific energy of 5000 Wh/kg. The results of the study show that the PEM hybrid system fueled using lithium hydride offers a three- to fivefold reduction in mass compared to state-of-the-art batteries

Mars power system concept definition study. Volume 1: Study results

A preliminary top level study was completed to define power system concepts applicable to Mars surface applications. This effort included definition of power system requirements and selection of power systems with the potential for high commonality. These power systems included dynamic isotope, Proton Exchange Membrane (PEM) regenerative fuel cell, sodium sulfur battery, photovoltaic, and reactor concepts. Design influencing factors were identified. Characterization studies were then done for each concept to determine system performance, size/volume, and mass. Operations studies were done to determine emplacement/deployment maintenance/servicing, and startup/shutdown requirements. Technology development roadmaps were written for each candidate power system (included in Volume 2). Example power system architectures were defined and compared on a mass basis. The dynamic isotope power system and nuclear reactor power system architectures had significantly lower total masses than the photovoltaic system architectures. Integrated development and deployment time phasing plans were completed for an example DIPS and reactor architecture option to determine the development strategies required to meet the mission scenario requirements

Feasibility study of long-life micro fuel cell power supply for sensor networks for space and terrestrial applications

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, June, 2010."May 2010." Cataloged from PDF version of thesis.Includes bibliographical references (p. 87-90).Sensor networks used for activities like border security, search and rescue, planetary exploration, commonly operate in harsh environments for long durations, where human supervision is minimal. A major challenge confronting such devices is providing adequate and reliable power supply required for long durations. This research considers the feasibility of a miniature Proton Exchange Membrane (PEM) fuel cell system coupled with battery to supply power for long life missions. The focus of this research is to prove the feasibility of long-life, self-contained power-supplies using miniature fuel cells for low-power distributed sensor networks. In this research, the performance of fuel cell power-supplies weighing not more than a few hundred grams is studied. The performance of the PEM fuel cell is modeled, analyzed and validated using experimental results. The feasibility of the fuel cell power systems are studied for two reference missions - one on the lunar surface and the other in the desert regions of Negev, Israel. This research analyzes the use of passive methods to achieve thermal, air and water management for PEM fuel cells supplying power to these field sensors. The results of this study suggest that the proposed fuel cell power system is capable of providing power to sensor modules in challenging field conditions with operational lives extending from many months to years. The scope of this concept can be extended to power devices such as micro-robots and small unmanned aerial vehicles operating in extreme environmental conditions for sustained periods of time.by Kavya Kamal Manyapu.S.M

Exploration and utilization of asteroids as interplanetary communication relays

There are more than 17,000 asteroids found near Earth and nearly 2 million asteroids estimated in the main belt between Mars and Jupiter. Asteroid come in diverse forms, some may hold valuable resources such as water, carbon and rare metals that may one day supply a spacefaring civilization. However, asteroids maybe also valuable as relay stations for a permanent high-speed, high-bandwidth interplanetary communication network. Asteroids are typically pock-marked with craters and grooves. Pristine craters resemble a parabolic communication antenna, but without the reflective coating or a receiver/transmitter at the focus. In this work, we evaluate two scenarios, the preliminary feasibility of setting up such a radio antenna on the Martian moon Phobos and Deimos (thought to be captured asteroids) that would act as a communication relay between the Martian system and Earth. Phobos is closer to Mars and is tidally locked. This would require two craters converted to antennas, one perpetually pointing at Mars, another pointing at Earth and a local interconnection between the two. Alternately, the relay on Deimos would need just a single crater relay station. We will then compare this communication relay to the current state-of-the-art, namely the Mars Reconnaissance Orbiter (MRO). The proposed communication antennas would be achieved by landing a swarm of CubeSats onto a crater to form the parabolic reflector. Each CubeSat has a mass of 4 kg and a volume of 3U or 3400 cc with one side forming the surface of the reflector. These CubeSats would hop, roll and fly into the crater and distribute themselves to cover maximum surface area. Each CubeSat has deployable reflectors to fill the gap between adjacent neighbors. A parabolic reflector would be able to reflect radio waves with a gap of one-tenth of the wavelength. A large 12U CubeSat would be positioned at the crater center and extend a deployable tower with a feed antenna to the focus. To achieve the current data rate of MRO, which is 4 Mbps, the power needs of a pair of 20 m(2) aperture antennas on Phobos and the interlink will be evaluated. For Deimos, a single 20 m(2) antenna will be considered. In both cases, the intent is to have an antenna gain of 50 dBi per crater. The analysis will also be extended to a 200 m(2) aperture antenna that can provide a data rate of 40 Mbps and antenna gain of 60 dBi per crater. Our approach to the mission design exploits machine learning to perform formulation, design, planning and operations. The results from these preliminary mission design studies will be used to identify a pathway towards detailed design and field studies in a simulated environment.This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Materials dependencies for dual-use technologies relevant to Europe's defence sector

In order to support the European Commission in the preparation of future initiatives fostering the sustainability of strategic supply chains, this study was commissioned to assess bottlenecks in the supply of materials needed for the development of technologies important to Europe's defence and civil industries. The study focuses on five dual-use technology areas, namely advanced batteries, fuel cells, robotics, unmanned vehicles and additive manufacturing (3D printing). The technologies are preselected on the basis of a previous study (EASME, 2017) that explored the dual-use potential of key enabling technologies in which Europe should strategically invest. In addition, this report examines how these technologies could address specific military needs and their differences in relation to civil needs and identified opportunities for future defence research areas that could potentially serve as a basis for the design of research initiatives to be funded under the future European Defence Fund. Moreover, potential opportunities for common policy actions are also identified, notably: to strengthen Europe's position in the selected technologies’ supply chains; to facilitate collaboration between stakeholders; to increase industry involvement with special emphasis on small and medium-sized enterprises; to improve existent legislation; and increase synergies between civil and defence sectors in order to speed up progress in promising research areas.JRC.C.7-Knowledge for the Energy Unio

Impact of powertrain components size and degradation level on the energy management of a hybrid industrial self-guided vehicle

This paper deals with the design of an energy management strategy (EMS) for an industrial hybrid self-guided vehicle (SGV), considering the size of a fuel cell (FC) stack and degradation of a battery pack. In this context, first, a realistic energy model of the SGV was proposed and validated, based on experiments. This model provided a basis for individual components analysis, estimating energy requirements, component sizing, and testing various EMSs, prior to practical implementation. Second, the performance of the developed FC/battery SGV powertrain was validated under three EMS modes. Each mode was studied by considering four different FC sizes and three battery degradation levels. The final results showed that a small FC as a range extender is recommended, to reduce system cost. It is also important to maintain the FC in its high efficiency zones with a minimum ON/OFF cycle, leading to efficiency and lifetime enhancement of FC system. Battery SOC have to be kept at a high level during SGV operation, to support the FC during SGV acceleration. In order to improve the SGV’s overall autonomy, it is also important to minimize the stop and go and rotational SGV motion with appropriate acceleration and deceleration rate