SCIENCE BOND

The historic drought that parched Brazil over the last two years was not just a water-supply problem — it was also a power problem. The nation's heavy use of hydroelectricity, which had made it a model of renewable energy, contributed to an increased risk of rolling blackouts in some of Brazil's largest cities during severe droughts. Now, Princeton researchers are joining with colleagues at a Brazilian university to help the operator of Brazil's electric grid and the country's major utilities develop a system to better manage their electric system when hydropower dries up.  Warren Powell, a professor of operations research and financial engineering, will join colleagues at the University of Campinas to analyze plans for integrating new types of renewable energy into the Brazilian electric grid. Powell, whose work focuses on optimization and uncertainty, has done extensive research on electricity distribution systems. Among other topics, Powell has analyzed the PJM ...

Lithium-air cells can store energy much more densely than today's lithium-ion batteries, making them particularly promising for electric cars.  The design, published in Science, uses a spongy graphene electrode and a new chemical reaction to drive the cell.  It loses much less energy and can be recharged many more times than previous attempts at lithium-air batteries.  The hope for lithium-air batteries is that they will take in regular air to fuel the chemical reaction that releases electricity: lithium ions move from the positive electrode to the negative one, where they are oxidised.  At present the engineers behind the new effort, at the University of Cambridge, have only made laboratory test units which operate in pure oxygen, rather than air. In a first, however, the prototypes can operate when that oxygen is  moist.  "What we really want is a lithium-air battery - one that just takes in air, without having to remove CO2, nitrogen and water,"...