Till now producing solar cells with this level of efficiency has been prohibitively expensive. Solar cells are coated with an electrically passivating layer of silicon oxide or nitride. This non-conducting material needs to be removed at specific points to allow attachment of the electrical contacts - a hitherto costly multi-phase process. Fraunhofer researchers have arrived at a new solution: A special laser "zaps away" the coating from the designated contact points. This reduces the total number of process steps by eighty percent, making these solar cells a viable alternative to other sources of energy.
The Fraunhofer Department for Energy Technology has also presented another hot solution to power your device: the first functioning micro-gas cell for use in smartphones or PDAs. Four German companies and the Fraunhofer Department based in Plymouth, Michigan, have united in order to develop a series-ripe gas cell system. Like solar cells, fuel cells offer attractive advantages compared to rechargeable batteries: significantly higher storage capacity, long lifetime, flat and variable designs, and extremely low self-discharge.
German and international industry-giants are now demonstrating their innovation in Hall 7 of the fairground with a camcorder that Fraunhofer researchers have equipped with micro-gas cells. It has an output of ten watts, delivered through an 8 volt circuit and it is hardly larger than a matchbox. It consists of 16 bipolar disks. This solution is provided by combining a polymer membrane (PEM) fuel cell with a hydrogen storage unit. The separation of the energy converter (fuel cell) and the storage unit (a hydrogen reservoir) allows energy and power to be dimensioned independently of each other. While the size of the fuel cell remains constant, to achieve longer operating life you only need to enlarge hydride storage unit. Fraunhofer first demonstrated this with a laptop at the Hanover Trade Fair in 1998. Among the development-partners for this prototype were Siemens PC Systems (now Fujitsu Siemens) and Aventis.
The most innovative feature of the fuel cell system is the banded-structure of the membrane. The area is divided into individual cell domains. An integrated series connection over the membrane surface allows the sum of the individual voltages to be drawn at the endplates. To store hydrogen in the smallest possible volume, Fraunhofer uses the well known procedure of hydride formation -- one of the safest known methods. Even at low pressure, high storage densities can be achieved with special metal powders. In addition, this storage medium does not suffer at all from self-discharge and can be refilled with hydrogen many times.
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