Alternative Green Technology for Power Generation Using Waste-Heat Energy And Advanced Thermoelectric Materials

NASA is interested in advancing green technology research for achieving sustainable and environmentally friendly energy sources. Thermo-electric power generation (TEPG) has exceptionally rich potential to fulfill this need. A TEPG module requires (1) material that can provide high figure of merit while still providing efficient heat control; (2) low resistance ohmic contacts that operate at high temperature; and (3) efficient heat sink material to provide optimal temperature difference between hot and cold junctions. In Phase I, we addressed all of these issues. We successfully produced device quality n-type and p-type, single crystalline and bulk nano-composite PbTe material suitable for TEPG device fabrication. We also developed a novel electrical contact technology having low electrical resistance and capability to withstand significantly elevated temperatures (>800 degree C). And we developed a light weight, highly thermal conductive (50 to 60 % better than copper) heat sink material with tailored low coefficient of thermal expansion (CTE). These improvements allowed us to develop the design and technique for fabrication of large scale TEPG on a manufacturing level. In Phase II we will expand upon these developments and implement them. We will fabricate TEPG devices using the nano-composite materials. These devices will utilize the ohmic contacts and the heat sink technology that we developed. We will also utilize another approach that we developed in which two materials (PbTe and (Bi-Sb)2(Se-Te)3 based alloys) are segmented into a two-part material that has high efficiency over the entire temperature range from 200-500 degreeC, PbTe being at the hot end and the (Bi-Sb)2(Se-Te)3 based material at the cold end. Our ultimate goal will be to build a TEPG module using such segmented devices to demonstrate the generation of 1kWatt of power. We will develop the technology of fabricating these modules at a large scale manufacturing level, at low cost.

The product of the proposed research is nanostructured bulk thermoelectric materials that have higher efficiency than conventional materials so that high levels of power can be produced in an environmentally clean (pollution free) manner. The manufacturing technology developed during this program will not only be applicable to the proposed materials but to any thermoelectric material with suitable modifications. This will result in manufacturing of thermoelectric power generation and cooling devices with high efficiency and at economically viable cost. NASA anticipates the need for advanced power generation and conversion that goes well beyond the capabilities of the current level of technology for the success of its future missions. Systems are needed that provide significantly better conversion efficiency, higher specific power and enhanced operational capabilities. Thermo-electric power generation (TEPG) has exceptionally rich potential to contribute to electrical power generation in space based applications, and the potential of enabling large-scale electric power generation.

The materials and devices that will result from this research will be useful for both power generation and cooling applications. Major commercial application is in the area of vehicle waste heat recovery (generally from the exhaust pipe) and is very attractive to auto makers in the country. Government agencies like DOD and DOE have a need for thermoelectric power generation for specialized applications. TEPG modules built from suitable thermoelectric materials can be used to build self-powered water and space heating systems, to retrieve the waste heat emitted from incinerators, power plants, or other similar sources, to promote the practice of green building, and even to generate power using human body heat. Development of TEPG materials will advance the state-of-the art in systems and components by reducing / replacing the use of fossil fuels in a cost effective manner.

This is early/mid-stage (TRL 6) — the most realistic path in is NASA SBIR/STTR, which funds small businesses and research institutions to develop technology aligned with NASA's needs (equity-free, phased funding). Check whether a current SBIR/STTR solicitation topic overlaps with this project's technology area, or contact the project directly (above) to ask.

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