Rough Silicon Nanowires for Heat Harvesting and Cooling Applications


- Heat harvesting - Electricity for internal automobile use, i.e. heating, windows - Conversion of automotive exhaust into supplemental power for hydrogen fuel cell-powered cars - Power jackets using heat from human body to power electronic devices - Thermoelectric cooling - Refrigeration - Air-conditioning - Cooling of computer chips and electronic devices - Thermoelectric power generation

- Conversion of wasted heat into electricity, whether on a small or large scale - High ZT values of 0.8 at room temperature and > 1 at higher temperatures - High performance at low cost, given wide availability of silicon - Easily manufactured using existing silicon-based processing facilities, unlike bismuth telluride alloys - Conserves energy and reduces carbon dioxide emissions - Could replace mechanical power generation and refrigeration systems - Miniaturization makes possible efficient, localized heating and cooling

Arun Majumdar, Peidong Yang, and colleagues at Berkeley Lab and the University of California at Berkeley have devised a new procedure using silicon nanowires to capitalize on the wasted energy produced not only by combustion engines but even by the human body. The unusually rough surfaces of the nanowires are produced on large wafers through an "electroless etching" manufacturing process. Their excellent thermoelectric properties at room temperature open the way for high-performance and inexpensive thermoelectric materials for everyday applications, both miniaturized and on a large scale.

The new materials have achieved ZT values of 0.8 at room temperature and > 1 at higher temperatures in wires of approximately 75 nanometers in diameter, and with optimal doping, diameter reduction and roughness control, this figure could rise even higher. Values of 1 have been achieved with films of bismuth telluride and its alloys, but these are difficult to work with and expensive to produce.

Bulk silicon, by comparison, is plentiful, and any commercial exploitation could make use of the extensive infrastructure already in place for manufacturing semiconductors. Although silicon is a poor thermoelectric material at room temperature, the exceptionally rough surfaces of the new nanowires substantially reduce thermal conductivity, efficiently scattering phonons without significantly reducing electrical conductivity. Thermal conductivity can be reduced even further at lower temperatures.

The electrochemical process synthesizes arrays of silicon nanowires in aqueous solution on the surfaces of large wafers, through the reduction of silver ions on the wafer surface. The large-area arrays of vertically aligned nanowires can be placed between two electrodes for thermoelectric power generation or thermoelectric cooling.

Combustion engines using fossil fuels typically operate at only 30 to 40 percent efficiency. The capacity to convert their low-grade waste heat to electricity could realize both significant fuel savings and a reduction in carbon emissions.

Inventor(s): Arun Majumdar, Peidong Yang

Type of Offer: Licensing

Next Patent »
« More Energy Patents

Share on      

CrowdSell Your Patent