Lawrence Livermore National Laboratory (LLNL) material scientists have created thermoelectric generators that can harvest waste heat from previously inaccessible sources, such as pipes with complex geometries.
Thirteen quadrillion (3600 terawatt-hours) BTUs of energy is lost annually through waste heat by U.S. industry.
The team cold-sprayed a bismuth-telluride powder on substrates ranging from stainless steel to aluminum silicate and quartz. The sprayed material had a randomly oriented microstructure largely free from pores and the cold-spray deposition was achieved without substantial compositional changes.
A ZT of 0.3 can probably only recover 2-4% of the heat as electricity, but it will be from places where we could recover nothing before
A new application of cold-spray deposition has been demonstrated that can fabricate bulk pieces of thermoelectric Bi2Te3 on a wide variety of substrates, without loss of structural integrity. By entraining particles in a supersonic gas flow, millimeter-thick blocks can be built up on flat or curved surfaces in a matter of seconds, providing a pathway to waste heat recovery from narrow pipes or other, more complicated, shapes. The sprayed material is composed of randomly oriented crystallites that match the chemical composition of the precursor billet and is > 99.5% dense. The Seebeck voltage and thermal conductivity are comparable to or better than bulk Bi2Te3, while the as-deposited resistivity is an order of magnitude higher. A simple annealing treatment at 400°C removes defects and decreases resistivity, increasing ZT to ~ 0.3 at operating temperatures of 80°C. Integrated TEG measurements of Bi2Te3 sprayed on copper flats or pipes suggest performance comparable to simple devices fabricated from blocks of the bulk material, demonstrating that cold spray is a viable alternative to traditional manufacturing approaches for thermoelectric materials.
SOURCE – LLNL, Advanced Processing and Additive Manufacturing of Functional Magnetic Materials
Written By Brian Wang, Nextbigfuture.com