Berkeley Achieves New Highs in Thermophotovoltaic Efficiency

Dean Sigler Announcements, Electric Powerplants, Solar Power, Sustainable Aviation Leave a Comment

Researchers at University of California at Berkeley announced a record in thermophotovoltaic efficiency, now at 29 percent, but with a few tweaks, soon to be at 50 percent.  This is great news for small drones, which could stay up for days, but possibly not a be-all, end-all for larger, more conventional electric aircraft.  Let’s examine the potential and the pitfalls involved. The researchers’ “groundbreaking physical insight” and “novel design” applies thermophotovoltaic principles that are “an ultralight alternative power source.”  Eli Yablonovitch, professor of electrical engineering and computer science (EECS), wrote in a paper published in the Proceedings of the National Academy of Sciences, ““Thermophotovoltaics are compact and extremely efficient for a wide range of applications, from those that require as little as 100 watts, [such as] a lightweight unmanned aerial vehicle, to 100 megawatts, [providing] electricity for 36,000 homes. In comparison, a 100-megawatt combined cycle power plant is massive,” Expanding on work he and his students published in 2011, Yablonovitch …

Sustainable Aviation Symposium 2019

Dean Sigler Announcements, SAS, Sustainable Aviation Leave a Comment

The 2019 Sustainable Aviation Symposium is moving to a new date and location – and a new inclusiveness. The University of California, Berkeley Institute for Transportation Studies (ITS) will host the 2019 Sustainable Aviation Symposium (SAS) on October 7-8 of 2019.  SAS 2019 is focused on safe, quiet, electric aviation solutions to the most pressing problems of our age: climate change, urban surface gridlock, and the need for integrated community and urban planning to enable high proximity aviation at meaningful scale. Dr. Jasenka Rakas, founder and head of the Airport Design Studio at the University of California at Berkeley, and Sustainable Aviation Foundation founder and President Dr. Brien Seeley will co-chair the meeting that will present a challenging review of aviation’s green future. This year’s symposium will convene thought leaders to answer these core questions: Which systems will win a dominant share of the market and why? How will “urban air vehicles” be made “airline-safe” and autonomous? What new technologies are …

Rumpled Cathodes Benefit Lithium Sulfur Batteries

Dean Sigler Batteries, Sustainable Aviation Leave a Comment

We like to think of things inside batteries as neatly organized, but Pennsylvania State University researchers may have come up with a less tidy way of making cathodes. Researchers synthesized “highly crumpled” nitrogen-doped graphene (NG) sheets with “ultrahigh pore volume” and large surface area (1,158 square meters– 12,465 square feet or about one-third the area of a football field) per gram.  This large area and high porosity “enable strong polysulfide adsorption and high sulfur content for use as a cathode material in Li-sulfur batteries.”  Interwoven rather than stacked, the wrinkled material provides ample room for “nitrogen-containing active sites.” The batteries, according to the researchers, “achieved” a high capacity of 1,226 milliamp-hours per gram and 75-percent capacity retention after 300 cycles.  This demonstrated capacity and longevity is something other experimenters with lithium sulfur batteries have tried unsuccessfully to achieve. Green Car Reports quotes Jiangxuan Song, one of the researchers on the techniques used. “Lithium–sulfur battery cells using these wrinkled graphene sheets …

Dendrites Grow Like Kudzu

Dean Sigler Electric Powerplants, Sustainable Aviation Leave a Comment

Getting your fiber is a good idea for digestion and general health, but what if those fibers get you first?  Or at least destroy your battery?  This is the situation as described by a report from the U.S. Department of Energy (DOE)’s Lawrence Berkeley National Laboratory (Berkeley Lab), in which the writer tells us that dendrites are hairy little lithium fibers that “sprout from the surface of the lithium electrode and spread like kudzu across the electrolyte until they reach the other electrode.” These 3D reconstructions show how dendritic structures that can short-circuit a battery form deep within a lithium electrode, break through the surface and spread across the electrolyte. Besides resembling a fast-growing invasive plant, the dendrite bridge across the electrodes can cause an internal short circuit and possible fires in the battery, making dendrites extremely unwanted intruders. Because they pop up from the surface of electrodes, dendrites might easily have been understood as a surface phenomenom.  Nitash Balsara, …

Lithium-Sulfur Achieves New Highs

Dean Sigler Electric Powerplants, Sustainable Aviation Leave a Comment

Allen Chen at the University of California at Berkeley reports that researchers at the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) “have demonstrated in the laboratory a lithium-sulfur (Li/S) battery that has more than twice the specific energy of lithium-ion batteries, and that lasts for more than 1,500 cycles of charge-discharge with minimal decay of the battery’s capacity,” the longest cycle life reported so far for any lithium-sulfur battery. Working on the premise that if electric vehicles are to have a 300-mile range, researchers explain that batteries will need to provide a cell-level specific energy of 350 to 400 Watt-hours per kilogram (Wh/kg), roughly double that of lithium-ion batteries. They should also manage at least 1,000, and preferably 1,500 charge-discharge cycles before showing noticeable power loss. Elton Cairns, of the Environmental Energy Technologies Division (EETD), is a professor at Berkeley in the The Berkeley Energy Storage and Conversion for Transportation and Renewables (BESTAR) Program.  Part of their purpose …