Panasonic develops thermoelectric tubes for compact geothermal electricity generation and waste heat recovery
Panasonic has developed novel thermoelectric tubes designed for fluid heat sources such as hot water and steam. The tubular shape enables direct and efficient heat transfer without additional heat exchangers, yielding high density of generated power. Panasonic says that its thermoelectric tube is suited for capturing unused or wasted heat from hot springs and factories.
|Panasonic’s thermoelectric conversion tube. Click to enlarge.|
Conventional thermoelectric generators can be complicated in structure and restricted in planar shape, making them difficult to scale-up and implement. Panasonic addressed these issues by using a phenomenon called the transverse thermoelectric effect, which takes place in tilted multilayer made of thermally-resistive thermoelectric materials and thermally-conductive metals. This effect makes it possible to control heat flow and electric current independently in materials, enabling a simple structure without complicated electric junctions and planar substrates.
The thermoelectric tube is constructed by stacking conical rings of bismuth telluride as thermoelectric material and nickel as metal. Panasonic has developed processing technologies in fabricating conical rings of brittle thermoelectric materials and bonding rings with minimum parasitic electric and thermal losses.
The performance of power generation is strongly dependent on many parameters such as size of the tube and amount of heat source. Panasonic says it has developed the simulation technology to optimize the design of the thermoelectric tube in order to maximize the output electric power in accordance with surrounding conditions.
A 10 cm-long fabricated thermoelectric tube using technologies introduced above can generate 1.3 W of electricity by running hot water of 90 °C inside, and cold water of 10 °C outside the tube. The power density corresponds to as high as 10 kW with 1 m3 of volume. Development on system design, optimization in manufacturing and feasibility study are now under way or planned, with a view to realizing compact, efficient, and economical generators fueled by geothermal energy and waste heat in factories.
Panasonic holds 29 domestic patents and 12 overseas patents, including pending applications, on this technology.
This development was partially presented at the Electronic Materials Conference held in Santa Barbara, California on 22 June 2011.