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News Article | April 28, 2017
Site: cen.acs.org

To exploit zinc’s useful properties in next-generation batteries, researchers have prepared zinc electrodes in a porous spongelike structure. Batteries with such electrodes could be long-lasting, energy dense, and inherently safe, according to a study (Science 2017, DOI: 10.1126/science.aak9991). The relatively low cost of zinc coupled with its wide availability and favorable electrochemical properties should give zinc-based batteries a competitive advantage over other battery chemistries. In particular, Zn batteries could be safer than lithium-ion batteries because Zn ones use aqueous electrolytes instead of the flammable organic kinds standard in Li-ion batteries. But aqueous Zn-based batteries fail quickly. Upon recharging, the metal forms wiry dendrites that can grow uncontrollably and pierce the separator between the electrodes. The dendrites can then connect the positive and negative electrodes and short-circuit the battery. Scientists at the Naval Research Laboratory (NRL) in Washington, D.C., have shown that those problems can be bypassed by using zinc electrodes with a spongelike structure instead of conventional pressed powder electrodes. The team, which includes Joseph F. Parker, Debra R. Rolison, and Jeffrey W. Long, prepared the zinc sponges by adding zinc powder to an emulsion of oil and water and then allowing the mixture to dry overnight. The sponge structure leads to more uniform oxidation of the zinc metal during discharge and, consequently, a more uniform coating of the discharge product, zinc oxide, on the sponge anode. Likewise, the structure makes the reverse reaction during charging—ZnO reduction to metallic Zn—more uniform. Even when 90% of the zinc is oxidized during discharge, Parker notes, the sponge retains a metallic zinc core. The core causes electric currents to be distributed uniformly throughout the sponge, making it physically difficult to form dendrites, he adds. The team found that the sponge electrodes protected a Ni-Zn battery when it cycled repeatedly between charging and discharging under demanding current conditions that induce dendrite formation in reference batteries. It also enabled the battery to withstand tens of thousands of cycles required for “start-stop” microhybrid vehicles. “For quite some time, this team and others have been attempting to use 3-D structured electrodes to enhance rechargeable battery performance,” says Paul V. Braun, professor of materials science and chemistry at the University of Illinois, Urbana-Champaign. Braun notes that the NRL team “has found a particularly compelling system, where the 3-D electrode structure provides high power, as expected, but perhaps surprisingly, results in dendrite suppression and thus very good long term cycling.” He adds “this discovery is particularly useful because it is accomplished with an intrinsically safe, earth abundant, and relatively high-energy-density nickel-zinc chemistry.”


News Article | April 28, 2017
Site: www.greencarcongress.com

« Technion team devises method for on-demand H2 production from water and aluminum for aviation applications | Main | Ford introduces new Intelligent Speed Limiter in Europe » Researchers at the US Naval Research Laboratory’s (NRL) Chemistry Division have demonstrated that the use of zinc formed into three-dimensional sponges for use as an anode boosts the performance of nickel–zinc alkaline cells in three areas: (i) > 90% theoretical depth of discharge (DOD ) in primary (single-use) cells; (ii) > 100 high-rate cycles at 40% DOD at lithium-ion–commensurate specific energy; and (iii) the tens of thousands of power-demanding duty cycles required for start-stop microhybrid vehicles. Joseph Parker, Jeffrey Long, and Debra Rolison from NRL’s Advanced Electrochemical Materials group are leading the effort to create an entire family of safer, water-based, zinc batteries. With 3-D Zn, the battery provides an energy content and rechargeability that rival lithium-ion batteries while avoiding the safety issues that continue to plague lithium. The research appears in the journal Science. The present energy-storage landscape continues to be dominated by lithium-ion batteries despite numerous safety incidents and obstacles, including transportation restrictions, constrained resource supply (lithium and cobalt), high cost, limited recycling infrastructure, and balance-of-plant requirements—the last of which constrains the energy density of Li-ion stacks. Despite these disadvantages, Li-ion batteries are widely used because they provide high energy density, high specific power, and long cycle life—attributes that must also be met by any alternative battery system in order to compete for market share. The family of zinc-based alkaline batteries (Zn anode versus a silver oxide, nickel oxyhydroxide, or air cathode) is expected to emerge as the front-runner to replace not only Li-ion but also leadacid and nickel–metal hydride batteries. This projection arises because Zn is globally available and inexpensive, with two-electron redox (Zn0/2+) and low polarizability that respectively confer high specific capacity and power. The long-standing limitation that has prevented implementing Zn in next-generation batteries lies in its poor rechargeability due to dendrite formation. We bypass this obstacle to cycling durability by redesigning the Zn electrode as a monolithic, porous, aperiodic architecture in which an inner core of electron-conductive metallic Zn persists even to deep levels of discharge...In primary 3D Zn–air cells, this “sponge” form factor (3D Zn) discharges >90% of the Zn, a 50% improvement over conventional powder-bed composites. When cycling Zn sponges at the demanding current densities that otherwise induce dendrite formation in alkaline electrolyte—typically greater than 10 mA cm–2—the 3D Zn restructures uniformly without generating separator-piercing dendrites. Zinc-based batteries are widely used for single-use applications, but are not considered rechargeable in practice due to their tendency to grow conductive dendrites inside the battery, which can grow long enough to cause short circuits. With the benefits of rechargeability, the 3-D Zn sponge is ready to be deployed within the entire family of Zn-based alkaline batteries across the civilian and military sectors. NRL’s work is funded by the Office of Naval Research and the Advanced Research Projects Agency-Energy.


News Article | April 28, 2017
Site: www.rdmag.com

Researchers at the U.S. Naval Research Laboratory's (NRL) Chemistry Division have developed a safer alternative to fire-prone lithium-ion batteries, which were recently banned for some applications on Navy ships and other military platforms. Joseph Parker, Jeffrey Long, and Debra Rolison from NRL's Advanced Electrochemical Materials group are leading an effort to create an entire family of safer, water-based, zinc batteries. They have demonstrated a breakthrough for nickel-zinc (Ni-Zn) batteries in which a three-dimensional (3-D) Zn "sponge" replaces the powdered zinc anode traditionally used. With 3-D Zn, the battery provides an energy content and rechargeability that rival lithium-ion batteries while avoiding the safety issues that continue to plague lithium. Their research appears in the April 28th, 2017 issue of Science, the premiere journal of the American Association for the Advancement of Science. Additional contributors to this research article include former NRL staff scientist, Christopher Chervin, National Research Council postdoctoral associate, Irina Pala, as well as industry partners Meinrad Machler and CEO of EnZinc, Inc., Michael Burz. "Our team at the NRL pioneered the architectural approach to the redesign of electrodes for next-generation energy storage," said Dr. Rolison, senior scientist and principal investigator on the project. "The 3-D sponge form factor allows us to reimagine zinc, a well-known battery material, for the 21st century." Zinc-based batteries are the go-to global battery for single-use applications, but are not considered rechargeable in practice due to their tendency to grow conductive whiskers (dendrites) inside the battery, which can grow long enough to cause short circuits. "The key to realizing rechargeable zinc-based batteries lies in controlling the behavior of the zinc during cycling," said Parker, lead author on the paper. "Electric currents are more uniformly distributed within the sponge, making it physically difficult to form dendrites." The NRL team demonstrated Ni-3-D Zn performance in three ways: extending lifetime in single-use cells; cycling cells more than 100 times at an energy content competitive with lithium-ion batteries; and cycling cells more than 50,000 times in short duty-cycles with intermittent power bursts, similar to how batteries are used in some hybrid vehicles. With the benefits of rechargeability, the 3-D Zn sponge is ready to be deployed within the entire family of Zn-based alkaline batteries across the civilian and military sectors. "We can now offer an energy-relevant alternative, from drop-in replacements for lithium-ion to new opportunities in portable and wearable power, and manned and unmanned electric vehicles," said Dr. Long, "while reducing safety hazards, easing transportation restrictions, and using earth-abundant materials."


News Article | May 4, 2017
Site: www.theengineer.co.uk

Researchers in the US claim to have developed a safer alternative to fire-prone lithium-ion batteries, which were recently banned for some applications on US Navy ships. Joseph Parker, Jeffrey Long, and Debra Rolison from the US Naval Research Laboratory’s (NRL) Advanced Electrochemical Materials group are leading the effort to create an entire family of safer, water-based, zinc batteries. They are said to have demonstrated a breakthrough for nickel-zinc (Ni-Zn) batteries in which a 3D zinc “sponge” replaces the powdered zinc anode traditionally used. With 3D zinc, the battery provides an energy content and rechargeability that are claimed to rival lithium-ion batteries while avoiding safety issues associated with lithium. Their research appears in Science. Additional contributors include former NRL staff scientist, Christopher Chervin, National Research Council postdoctoral associate, Irina Pala, as well as industry partners Meinrad Machler and CEO of EnZinc, Inc., Michael Burz. “Our team at the NRL pioneered the architectural approach to the redesign of electrodes for next-generation energy storage,” said Dr. Rolison, senior scientist and principal investigator on the project. “The 3D sponge form factor allows us to reimagine zinc, a well-known battery material, for the 21st century.” Zinc-based batteries are the go-to global battery for single-use applications, but are not considered rechargeable in practice due to their tendency to grow dendrites inside the battery, which can cause short circuits. “The key to realising rechargeable zinc-based batteries lies in controlling the behaviour of the zinc during cycling,” said Parker, lead author on the paper. “Electric currents are more uniformly distributed within the sponge, making it physically difficult to form dendrites.” The NRL team demonstrated Ni-3-D Zn performance in three ways: extending lifetime in single-use cells; cycling cells more than 100 times at an energy content competitive with lithium-ion batteries; and cycling cells more than 50,000 times in short duty cycles with intermittent power bursts, similar to how batteries are used in some hybrid vehicles. With the benefits of rechargeability, the 3D zinc sponge is ready to be deployed within the entire family of Zn-based alkaline batteries across the civilian and military sectors. “We can now offer an energy-relevant alternative, from drop-in replacements for lithium-ion to new opportunities in portable and wearable power, and manned and unmanned electric vehicles, while reducing safety hazards, easing transportation restrictions, and using earth-abundant materials,” said Long. On April 14, 2017 the US Navy issued a statement saying that it was banning e-cigarettes aboard ships, submarines, aircraft, boats, craft and heavy equipment. The policy was introduced in response to continued reports of explosions of so-called Electronic Nicotine Delivery Systems (ENDS) due to overheating lithium-ion batteries.


News Article | April 28, 2017
Site: www.aimgroup.com

On May 1, Joe Powell, managing director of Seek Education in Australia, will start at global sports technology firm Catapult (ASX: CAT) as chief executive officer (CEO). Seek hasn’t announced the successor of Powell at Seek Education yet. The managing director of Seek Education oversees Seek’s various education businesses (Seek Learning, Catho Education in Brazil, JobStreet Learning in Malaysia, OCC Education in Mexico and Online Education Services (Swinburne Online)). Powell joined Seek (ASX:SEK) ten years ago, first as the managing director of employment in Australia and New Zealand, a position he held for six years, and then as managing director of Seek Education. Powell drove the expansion of the Seek Education brand throughout Australia and internationally. More specifically, to the Seek businesses in Brazil, Southeast Asia, and Mexico. According to Catapult, the technology is used by most teams in the NFL, NBA, NHL and college sporting teams around the U.S., as well as all of Australia’s AFL, NRL and super rugby teams. It’s also expanded into elite soccer and rugby in Europe. Powell said he saw strong parallels between the growth opportunity at Catapult now and the Seek platform ten years ago. Seek co-founder and chief executive Andrew Bassat told the Age that he backed Powell’s appointment. “Throughout his time at Seek, it was clear Joe was an outstanding leader. He has great people skills, a keen grasp of strategy, and a great ability to execute,” Bassat said. Prior to joining Seek, Powell worked at Australian telco Optus for 11 years, where he held various positions, after a career as an accountant at PriceWaterhouseCoopers. Powell is the director of the Richmond Football Club in Victoria and remains a board member of Online Education Services, the Seek-controlled joint venture with Swinburne University. He gained a bachelor’s degree in commerce from the University of Tasmania and attended Harvard Business School’s advanced business management program. Powell had been an advisor to Holthouse and the Catapult board since September. Angela is a writer and journalist based in Sydney, Australia. She has extensive knowledge of the Australian real estate industry, having started her career in real estate advertising at News Limited newspapers, where she worked across a number of different mastheads in Sydney. She s also worked in television, magazines and online, and regularly contributes feature articles to The Sydney Morning Herald, MiNDFOOD and The Newcastle Herald. Angela also works as a content writer, creating written content for a number of SMEs across an array of industries, including real estate, education, technology and digital media.


News Article | May 17, 2017
Site: phys.org

The Solar Photovoltaic and Autonomous Soaring Base Program and the U.S. Marine Corps' Expeditionary Energy Office (E2O) want to improve the ability of unmanned platforms to support a 24-7 information, surveillance, and reconnaissance (ISR) mission. By doing so, the warfighter will greatly benefit because it will reduce the amount of batteries or fuel they must carry into battle, and improve the availability of continuous coverage of ISR assets. "NRL has twice flown our solar UAV [based on the SBXC sailplane] over 10 hours using a combination of solar photovoltaics and autonomous soaring as part of the 'solar-soaring' research program," said Dr. Dan Edwards, aerospace engineer. "This research is investigating the value of combining autonomous soaring algorithms and solar photovoltaics for capturing energy from the environment to extend flight endurance and mission operations of an aircraft." A photovoltaic array, custom built in NRL's Vehicle Research Section and Photovoltaic Section, is integrated into the center wing panel of the PV-SBXC aircraft as a drop-in replacement to the original wing. A power management and distribution system converts the power from the solar arrays into direct current (DC) voltage, which the electric motor can use for propulsion, or recharge a 'smart battery.' Additionally, an autonomous soaring software algorithm—that would typically monitor the local vertical winds around the aircraft—commands the aircraft to orbit in any nearby updrafts, very similar to soaring birds. However, the algorithm was disabled for the two solar flights in order to assess the solar-only performance. Passive soaring—meaning no specific maneuvers are attempted to catch thermals—was still allowed, to let the aircraft turn the motor off if altitude increased because of an updraft along the aircraft's pre-defined flight path. The autonomous soaring software was tested extensively in previous flight demonstrations in late October 2015. The UAV with solar arrays built at NRL using SunPower Inc. solar cells, flew for 10 hours, 50 minutes on October 14, 2016. Takeoff occurred at 7:20 a.m. at 95 percent battery state of charge and landing occurred at 6:10 p.m. with the battery at 10 percent state of charge. Thermal activity was very good in the middle of the day and 40 percent of the flight was spent with the motor off, and the solar array partly recharged the battery while the motor was off. The UAV equipped with solar wings incorporated PV arrays from Alta Devices, Inc. It flew for 11 hours, 2 minutes on April 19, 2017. Takeoff occurred at 7:46 a.m., approximately an hour after sunrise, with the battery's state of charge at 90 percent. Landing occurred at 6:48 p.m., approximately an hour before sunset, with the battery's state of charge at 26 percent. Thermal activity was very weak and almost all of the flight was spent running the motor. Near solar noon, the solar array provided sufficient power to cruise on solar power alone. The power management system for both flights was provided by Packet Digital, Inc., as part of a grant from the North Dakota Renewable Energy Council. "The experiments confirm significant endurance gains are possible by leveraging thermal updrafts and incident solar radiation, rather than ignoring these free sources of energy," Edwards said. "Future testing will focus on quantifying the trade space between improvements in solar cell efficiency and combining with autonomous soaring for improved solar-recharging." The Vehicle Research Section at NRL conducts research to develop technologies for autonomous, affordably expendable, unmanned systems that carry a wide variety of payloads for numerous mission scenarios. The Section is composed of aeronautical, aerospace, electrical, and mechanical engineers, scientists, and technicians dedicated to advancing the state-of-the-art in unmanned systems technology. The Photovoltaics Section at NRL conducts research to develop photovoltaic (solar cell) technologies to enable logistics free, renewable, portable, power sources for the warfighter. The Section is composed of physicists, electrical engineers, and chemists dedicated to advancing the state-of-the-art in PV power sources and systems. Explore further: NRL tests cooperative soaring concept for sustained flight of UAV sailplanes


News Article | May 17, 2017
Site: www.sciencedaily.com

Researchers at the U.S. Naval Research Laboratory (NRL), Vehicle Research Section and Photovoltaic Section are building on the proven concept of autonomous cooperative soaring of unmanned aerial vehicles (UAVs). Their research investigates the presence of solar photovoltaics (PV) to the cooperative autonomous soaring techniques, which enables long endurance flights of unmanned sailplanes that use the power of the sun. The Solar Photovoltaic and Autonomous Soaring Base Program and the U.S. Marine Corps' Expeditionary Energy Office (E2O) want to improve the ability of unmanned platforms to support a 24-7 information, surveillance, and reconnaissance (ISR) mission. By doing so, the warfighter will greatly benefit because it will reduce the amount of batteries or fuel they must carry into battle, and improve the availability of continuous coverage of ISR assets. "NRL has twice flown our solar UAV [based on the SBXC sailplane] over 10 hours using a combination of solar photovoltaics and autonomous soaring as part of the 'solar-soaring' research program," said Dr. Dan Edwards, aerospace engineer. "This research is investigating the value of combining autonomous soaring algorithms and solar photovoltaics for capturing energy from the environment to extend flight endurance and mission operations of an aircraft." A photovoltaic array, custom built in NRL's Vehicle Research Section and Photovoltaic Section, is integrated into the center wing panel of the PV-SBXC aircraft as a drop-in replacement to the original wing. A power management and distribution system converts the power from the solar arrays into direct current (DC) voltage, which the electric motor can use for propulsion, or recharge a 'smart battery.' Additionally, an autonomous soaring software algorithm -- that would typically monitor the local vertical winds around the aircraft -- commands the aircraft to orbit in any nearby updrafts, very similar to soaring birds. However, the algorithm was disabled for the two solar flights in order to assess the solar-only performance. Passive soaring -- meaning no specific maneuvers are attempted to catch thermals -- was still allowed, to let the aircraft turn the motor off if altitude increased because of an updraft along the aircraft's pre-defined flight path. The autonomous soaring software was tested extensively in previous flight demonstrations in late October 2015. The UAV with solar arrays built at NRL using SunPower Inc. solar cells, flew for 10 hours, 50 minutes on October 14, 2016. Takeoff occurred at 7:20 a.m. at 95 percent battery state of charge and landing occurred at 6:10 p.m. with the battery at 10 percent state of charge. Thermal activity was very good in the middle of the day and 40 percent of the flight was spent with the motor off, and the solar array partly recharged the battery while the motor was off. The UAV equipped with solar wings incorporated PV arrays from Alta Devices, Inc. It flew for 11 hours, 2 minutes on April 19, 2017. Takeoff occurred at 7:46 a.m., approximately an hour after sunrise, with the battery's state of charge at 90 percent. Landing occurred at 6:48 p.m., approximately an hour before sunset, with the battery's state of charge at 26 percent. Thermal activity was very weak and almost all of the flight was spent running the motor. Near solar noon, the solar array provided sufficient power to cruise on solar power alone. The power management system for both flights was provided by Packet Digital, Inc., as part of a grant from the North Dakota Renewable Energy Council. "The experiments confirm significant endurance gains are possible by leveraging thermal updrafts and incident solar radiation, rather than ignoring these free sources of energy," Edwards said. "Future testing will focus on quantifying the trade space between improvements in solar cell efficiency and combining with autonomous soaring for improved solar-recharging." The Vehicle Research Section at NRL conducts research to develop technologies for autonomous, affordably expendable, unmanned systems that carry a wide variety of payloads for numerous mission scenarios. The Section is composed of aeronautical, aerospace, electrical, and mechanical engineers, scientists, and technicians dedicated to advancing the state-of-the-art in unmanned systems technology. The Photovoltaics Section at NRL conducts research to develop photovoltaic (solar cell) technologies to enable logistics free, renewable, portable, power sources for the warfighter. The Section is composed of physicists, electrical engineers, and chemists dedicated to advancing the state-of-the-art in PV power sources and systems.


News Article | May 17, 2017
Site: www.eurekalert.org

WASHINGTON -- Researchers at the U.S. Naval Research Laboratory (NRL), Vehicle Research Section and Photovoltaic Section are building on the proven concept of autonomous cooperative soaring of unmanned aerial vehicles (UAVs). Their research investigates the presence of solar photovoltaics (PV) to the cooperative autonomous soaring techniques, which enables long endurance flights of unmanned sailplanes that use the power of the sun. The Solar Photovoltaic and Autonomous Soaring Base Program and the U.S. Marine Corps' Expeditionary Energy Office (E2O) want to improve the ability of unmanned platforms to support a 24-7 information, surveillance, and reconnaissance (ISR) mission. By doing so, the warfighter will greatly benefit because it will reduce the amount of batteries or fuel they must carry into battle, and improve the availability of continuous coverage of ISR assets. "NRL has twice flown our solar UAV [based on the SBXC sailplane] over 10 hours using a combination of solar photovoltaics and autonomous soaring as part of the 'solar-soaring' research program," said Dr. Dan Edwards, aerospace engineer. "This research is investigating the value of combining autonomous soaring algorithms and solar photovoltaics for capturing energy from the environment to extend flight endurance and mission operations of an aircraft." A photovoltaic array, custom built in NRL's Vehicle Research Section and Photovoltaic Section, is integrated into the center wing panel of the PV-SBXC aircraft as a drop-in replacement to the original wing. A power management and distribution system converts the power from the solar arrays into direct current (DC) voltage, which the electric motor can use for propulsion, or recharge a 'smart battery.' Additionally, an autonomous soaring software algorithm -- that would typically monitor the local vertical winds around the aircraft -- commands the aircraft to orbit in any nearby updrafts, very similar to soaring birds. However, the algorithm was disabled for the two solar flights in order to assess the solar-only performance. Passive soaring -- meaning no specific maneuvers are attempted to catch thermals -- was still allowed, to let the aircraft turn the motor off if altitude increased because of an updraft along the aircraft's pre-defined flight path. The autonomous soaring software was tested extensively in previous flight demonstrations in late October 2015. The UAV with solar arrays built at NRL using SunPower Inc. solar cells, flew for 10 hours, 50 minutes on October 14, 2016. Takeoff occurred at 7:20 a.m. at 95 percent battery state of charge and landing occurred at 6:10 p.m. with the battery at 10 percent state of charge. Thermal activity was very good in the middle of the day and 40 percent of the flight was spent with the motor off, and the solar array partly recharged the battery while the motor was off. The UAV equipped with solar wings incorporated PV arrays from Alta Devices, Inc. It flew for 11 hours, 2 minutes on April 19, 2017. Takeoff occurred at 7:46 a.m., approximately an hour after sunrise, with the battery's state of charge at 90 percent. Landing occurred at 6:48 p.m., approximately an hour before sunset, with the battery's state of charge at 26 percent. Thermal activity was very weak and almost all of the flight was spent running the motor. Near solar noon, the solar array provided sufficient power to cruise on solar power alone. The power management system for both flights was provided by Packet Digital, Inc., as part of a grant from the North Dakota Renewable Energy Council. "The experiments confirm significant endurance gains are possible by leveraging thermal updrafts and incident solar radiation, rather than ignoring these free sources of energy," Edwards said. "Future testing will focus on quantifying the trade space between improvements in solar cell efficiency and combining with autonomous soaring for improved solar-recharging." The Vehicle Research Section at NRL conducts research to develop technologies for autonomous, affordably expendable, unmanned systems that carry a wide variety of payloads for numerous mission scenarios. The Section is composed of aeronautical, aerospace, electrical, and mechanical engineers, scientists, and technicians dedicated to advancing the state-of-the-art in unmanned systems technology. The Photovoltaics Section at NRL conducts research to develop photovoltaic (solar cell) technologies to enable logistics free, renewable, portable, power sources for the warfighter. The Section is composed of physicists, electrical engineers, and chemists dedicated to advancing the state-of-the-art in PV power sources and systems. The U.S. Naval Research Laboratory provides the advanced scientific capabilities required to bolster our country's position of global naval leadership. The Laboratory, with a total complement of approximately 2,500 personnel, is located in southwest Washington, D.C., with other major sites at the Stennis Space Center, Miss., and Monterey, Calif. NRL has served the Navy and the nation for over 90 years and continues to advance research further than you can imagine. For more information, visit the NRL website or join the conversation on Twitter, Facebook, and YouTube.


News Article | May 17, 2017
Site: www.rdmag.com

Unmanned Aerial Vehicles (UAV) might soon be powered by the sun. Researchers at the U.S. Naval Research Laboratory, Vehicle Research Section and Photovoltaic Section have investigated the presence of solar photovoltaics to the cooperative autonomous soaring techniques to enable long endurance flights of unmanned sailplanes that use solar power. The Solar Photovoltaic and Autonomous Soaring Base Program and the U.S. Marine Corps’ Expeditionary Energy Office have begun to improve UAV’s so they can support a round-the-clock information, surveillance and reconnaissance mission, which would be able to benefit warfighters because it will reduce the amount of batteries or fuel needed to carry into battle and improve the availability of continuous coverage of ISR assets. “NRL has twice flown our solar UAV [based on the SBXC sailplane] over 10 hours using a combination of solar photovoltaics and autonomous soaring as part of the 'solar-soaring' research program,” Dan Edwards, Ph.D., an aerospace engineer, said in a statement. “This research is investigating the value of combining autonomous soaring algorithms and solar photovoltaics for capturing energy from the environment to extend flight endurance and mission operations of an aircraft.” A custom built photovoltaic array is integrated into the center wing panel of the PV-SBXC aircraft as a drop-in replacement to the original wing, while a power management and distribution system converts the power from the solar arrays into direct current voltage, which the electric motor can use for propulsion or to recharge a smart battery. The UAV with solar arrays was able to fly for 10 hours and 50 minutes last October without using the entire charge on the battery. Another UAV took off in April and flew for 11 hours and two minutes while using significantly less battery power. “The experiments confirm significant endurance gains are possible by leveraging thermal updrafts and incident solar radiation, rather than ignoring these free sources of energy,” Edwards said. “Future testing will focus on quantifying the trade space between improvements in solar cell efficiency and combining with autonomous soaring for improved solar-recharging.”


News Article | May 19, 2017
Site: news.mit.edu

When he first reported to MIT’s Nuclear Reactor Laboratory (NRL) as an undergraduate in 2002, David Carpenter anticipated a challenging research opportunity. To his surprise, he found his calling. It all began with a project investigating durable new materials for use in reactors. “We were testing silicon carbide, which looked like a good possibility for an accident-tolerant fuel,” recalls Carpenter ’06, SM ’06, PhD ’10. “We were irradiating it inside the reactor — it was the first time anyone had ever done this — and I realized that when we pulled the material out, we would get to see something no one had ever seen before,” he says. After 15 years at the NRL conducting research and earning degrees in nuclear science and engineering, Carpenter’s appetite for scientific discovery remains sharp, as does his commitment to improving both the performance and safety of current and next-generation nuclear reactors. Today, as the group leader for reactor experiments, he juggles projects brought to the facility by industry, government, and academic institutions. Throughout this time, he says he has never lost his appreciation for the NRL as a singular laboratory for scientific discovery. “I see the reactor as a machine that generates radiation for testing, and when you put things inside, you can get knowledge out,” he says. “I also appreciate that I get to work each day with this machine and understand how really unique it is, and to some people, maybe a bit mysterious.” It’s a job that also provides purpose. “I do have a sense of mission, an interest in pushing nuclear engineering to gain more acceptance, developing a real piece of technology for the future that can bring a carbon-free source of substantial energy,” he says. The MIT Reactor (MITR) is a light-water cooled facility and one of the few on-campus reactors of its kind. It operates 24 hours per day, 7 days per week throughout the year, except for planned maintenance and refueling. While a highly-skilled staff operates and monitors the facility, Carpenter’s role means that he is always on call. “If anything happens to the experiment, or if there are any interruptions in reactor operations, I’ll be involved,” he says. On a typical day, Carpenter tends to what he calls “the care and feeding of experiments” which take place in three separate research environments situated in the reactor core. All three rely on the MITR for a radiation environment, but each can be tuned to produce specific pressures and temperatures in gas, water or other media. The MITR serves as an ideal facility for developing and testing materials and instruments that can withstand the most extreme conditions and meet the challenges of nuclear reactor operations. Among the projects Carpenter is shepherding are several with the potential to make critical impacts on the nuclear energy industry. One is the continuation of his silicon carbide research, which was the subject of both his master’s and PhD dissertations, and which triggered significant interest outside of academia. Carpenter’s focus has involved deploying silicon carbide, a type of ceramic, as a first-line containment barrier in reactors. Since the 1950s, Carpenter explains, nuclear reactors have used uranium pellets stacked up in fuel rods made of zirconium alloys. “These rods are the first barrier against the release of radioactive material from the reactor, but as we’ve seen at the incidents at Fukushima and Three Mile Island, they can melt down in certain circumstances.” In contrast, silicon carbide in a reactor “gets really hot and sits there and just takes it, without getting soft and melting,” Carpenter says. Using MITR, he has subjected the material to the kinds of temperatures, water pressures, and chemistries that might be found in a full-power reactor. “We’ve gone through many iterations in a process lasting over 15 years, with many tweaks along the way,” he says. Carpenter believes this research has game-changing potential. “You could retrofit hundreds of existing reactors, making them much safer and more reliable overnight,” he says. But shifting to silicon carbide as an acceptable fuel cladding faces a number of challenges. Government and industry require a degree of certainty about new materials that necessitates more in-reactor testing. “Silicon carbide remains a very promising material, and it’s sitting in our reactor even as we speak,” he says. But there are also concerns that some of the ceramic can dissolve in water and travel downstream, and that the material may not have the necessary level of “elastic forgiveness,” he says, tending to crack and shatter under stress. Nevertheless, for Carpenter, this represents a fascinating engineering challenge. He imagines solutions that might involve weaving silicon fibers to achieve the required ductility, to enable a ceramic material to behave like a metal under some circumstances. As he investigates these possibilities, Carpenter is also invested in novel work on behalf of clients. Among these is a multi-university project funded by the U.S. Department of Energy to develop a high-temperature, salt-cooled reactor. “The design is intrinsically safe because the fuel doesn’t melt, and the salt can withstand high temperatures without requiring thick, pressurized containment buildings,” he says. “You can generate more power, more efficiently, and salt-cooled reactors are inherently much safer,” he says. The challenges to designing this new kind of reactor involve finding optimal construction materials, since super-hot radioactive salt is highly corrosive. Carpenter is tasked with figuring out how to configure the MITR to simulate a reactor operating at 700 degrees Celsius with molten salt. He must also contend with the radioactive tritium that is released when neutron radiation hits salt. “Much of our work involves creating a special environment in the reactor,” he says. “Our job is to help clients figure out a practical way of answering the questions they’re posing.” To perform his job, Carpenter must be a jack of all trades, whether using robot arms to manipulate projects in the reactor hot cells, or performing computational simulations. “I get to have a hand in pretty much everything, from plumbing, electrical work, and programming to conceptual design and installations,” he says. This comes naturally to the former Eagle Scout from Atlanta who also enjoyed assembling scale models of Star Trek’s Starship Enterprise. He says a “bring a parent to school” event helped seed his interest in nuclear energy. “A parent who worked for a nuclear utility company brought plastic fuel pellets to our class, and told us that one actual nuclear pellet represented tons of coal and barrels of oil,” he recalls. “I took that pellet home and taped it to my wall, and the idea that nuclear energy could do that really stuck with me.” When Carpenter arrived at MIT, a classmate easily nudged him toward pursuing nuclear science and engineering as a major. It was a short leap for Carpenter to seek out work at the campus reactor. “I got involved in research I liked, and kept doing it, with different experiments blossoming into my undergraduate thesis, then my graduate thesis, and then it seemed natural to keep working in the same lab,” he says. Though he never intended to stay this long, Carpenter says he is “really happy" with the work going on at the NRL. He says he is seeing a new wave of interest in nuclear technology research, and looks forward to cultivating students who bring the kind of commitment he felt when he first joined. “It would be great to stay long enough to see the silicon carbide materials program grow from sketches on paper to being implemented in reactors,” he says. “I hope I’ll be around to see it.”

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