Google (NASDAQ:GOOG) continues trying to whet the public's appetite for information on its Project Loon airborne Internet project with informational videos detailing the effort. In its latest video, the company highlights challenges involved in keeping Project Loon's batteries warm enough to operate properly in the sub-freezing temperatures of the stratosphere.
Each balloon runs on solar power during daylight, switching to power from a lithium ion battery pack at night. "Staying warm is a top priority to keeping the battery from losing its effective energy capacity," said Jim Morash, one of the project's electrical engineers, who noted the stratospheric temperatures can be as low as the -70° C range.
The entire power system is insulated to reflect and trap heat that is emanated by the balloon's electronics. Project Loon engineers currently rely upon multi-layer insulation made of shiny silver space blanket material similar to that used on NASA spacecraft.
Some of the first designs relied upon Styrofoam beverage coolers for insulation, but the performance at altitude was found lacking. "Styrofoam is an insulator that mostly prevents conduction and convection, and heat transfer in the stratosphere is mostly through radiation," Morash said.
The project has dabbled with using other materials for better cold temperature performance but found that those can create "a tradeoff in terms of the achievable energy density in the battery," according to Morash. Therefore, Google engineers have engaged in an iterative process to create new prototypes to test each month as they seek better solutions.
Stratospheric conditions are far from the only challenges faced by Project Loon, which aims to create a "flock" of high-altitude balloons filled with helium and air that can be floated at different heights in the stratosphere to deliver consistent broadband service coverage to earthbound users via unlicensed 2.4 and 5.8 GHz ISM bands. Aside from skepticism regarding Google's plan to keep each balloon aloft for 100 days, the company's effort faces questions regarding political issues, spying concerns and a lack of funding to supply end-user devices such as laptops and smartphones to potential users in developing countries.
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Article updated Nov. 12, 2013, to correct a quotation.