Hanover Trade Fair 2001, Germany.
The Department for Energy Technology at the Fraunhofer-Institute - cradle of MP3 and MIT's opposite number in Germany - has presented a solar solution for powering PDAs without the need to externally recharge the battery. They soon could apear on the mass market, as Casio, Siemens and others have their hands on the technology.
The problem facing tehcnologists is the shortage of space in the casing of a cellphone or PDA to allow integration of another power source like fuel or solar cells, Fraunhofer researchers told ZDNet. And it's a race against time: as mobile electronic devices shrink, at the same time they're becoming more powerful, continually forcing manufacturers of solar cells to raise the efficiency of their products. There are special types cells where energy efficiency has almost reached 25, but they are still too expensive for the mass market (See Cell Phone runs on alcohol ZDNet, Decmeber 31st 1998)
Researchers at the Fraunhofer Institute for Solar Energy Systems ISE in Freiburg, Germany, have now managed to find a workable combination of these hitherto conflicting factors. Their high-performance solar module (which will be shown in Hall 18 on the same fair ground where, some weeks ago CeBIT took place, from next week on) is integrated in the lid of a Casio palmtop, and makes the device completely autonomous of external electricity supply.
The prototype is a genuine innovation in this category of devices. "The decisive factor," emphasizes Dr. Christopher Hebling, head of the Micro-Energy Technology group at the ISE, "is that the device can run on solar power alone even under low lighting levels. At a normal workplace, you have only three percent of the energy of direct sun light. Even down to a level of one percent, the electrical voltage provided by our solar module remains virtually constant; in conventional cell types it would have long since broken down." The high output rating of over 35 milliamps per square centimeter in direct sunlight is attributable to the solar module's special design. Hebling explains: "The fourteen individual cells of single-crystal silicon overlap like roof tiles. They cover the busbar, where no electricity is actually generated. In this way, the cells make optimum use of the limited available space, and achieve an efficiency of more than twenty percent."
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