IIT alumnus technique may help harness bodys heat to recharge cell-phones

January 11th, 2008 - 1:12 pm ICT by admin  

Washington, January 11 (ANI): An Indian Institute of Technology, Bombay (IIT-B) alumnus has developed a technology that may make it possible to create personal power-jackets which may harness heat from the human body to recharge cell-phones and other electronic devices.

Professor Arun Majumdar, who is currently jointly associated with the University of California at Berkeley and the US Department of Energys Lawrence Berkeley National Laboratory (Berkeley Lab), says his technique is based on the synthesis of silicon nanowires.

He claims that his synthesized silicon nanowires can help harness the energy that is usually lost as heat during the production of electricity.

The researcher says that during experiments, rough silicon nanowires synthesized by his team demonstrated high performance thermoelectric properties even at room temperature when connected between two suspended heating pads. While one pad served as the heat source, the other as the sensor, he adds.
This is the first demonstration of high performance thermoelectric capability in silicon, an abundant semiconductor for which there already exists a multibillion dollar infrastructure for low-cost and high-yield processing and packaging, Nature magazine quoted him as saying.

Weve shown that its possible to achieve a large enhancement of thermoelectric energy efficiency at room temperature in rough silicon nanowires that have been processed by wafer-scale electrochemical synthesis, said chemist Peidong Yang, the other principal investigator behind this research, who also holds a joint Berkeley Lab and UC Berkeley appointment.

The researchers call their unique method of synthesizing arrays of silicon nanowires electroless etching. Here, the nanowires are synthesized in an aqueous solution on the surfaces of wafers that can measure dozens of square inches in area.

The technique involves the galvanic displacement of silicon through the reduction of silver ions on a wafers surface, they add.

While other synthesis techniques yield smooth-surfaced nanowires, the electroless etching method produces arrays of vertically aligned silicon nanowires with exceptionally rough surfaces, which are believed to be critical to the surprisingly high thermoelectric efficiency of the silicon nanowires.

The rough surfaces are definitely playing a role in reducing the thermal conductivity of the silicon nanowires by a hundredfold, but at this time we dont fully understand the physics. While we cannot say exactly why it works, we can say that the technique does work, said Majumdar.

Majumdar pointed out that the worlds electrical power is generated by heat engines, giant gas or steam-powered turbines that convert heat to mechanical energy, which is then converted to electricity. However, much of this heat releases into the environment, approximately 15 trillion Watts, he added.

According to him, even if a small fraction of the lost heat could be converted into electricity, its might have a huge impact on the energy situation.

Thermoelectric materials, which have the ability to convert heat into electricity, potentially could be used to capture much of the low-grade waste heat now being lost and convert it into electricity, said Majumdar.

This would result in massive savings on fuel and carbon dioxide emissions. The same devices can also be used as refrigerators and air conditioners, and because these devices can be miniaturized, it could make heating and cooling much more localized and efficient, he added.

The Berkeley Lab researchers are now seeking industrial partners to further develop and commercialise their technology. (ANI)

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