Report

Teaser, summary, work performed and final results

Periodic Reporting for period 1 - INTEGRAL (INitiative to bring the 2nd generation of ThermoElectric Generators into industrial ReALity)

Teaser

Thermoelectric materials have been studied for several decades now. Improved TE materials are emerging with the so-called second-generation thermoelectric (GEN2 TE) materials: silicides and half-Heusler. These materials are low-cost, based on most earth-abundant elements and...

Summary

Thermoelectric materials have been studied for several decades now. Improved TE materials are emerging with the so-called second-generation thermoelectric (GEN2 TE) materials: silicides and half-Heusler. These materials are low-cost, based on most earth-abundant elements and eco-friendly materials, and can impact positively European industry and society by converting wasted heat into electricity.
The aim of the INTEGRAL project is to upscale the GEN2 TE material technology using existing pilot lines and growing SMEs, in order to address mass markets TE needs (automotive, heavy duty trucks, autonomous sensors and industry waste heat recovery). INTEGRAL will allow the industry to step up towards advanced manufacturing and commercialization of systems integrating multifunctional TE materials (on a nano-based approach), through material customization, next techniques for characterization and process control and up-scaled pilot-line demonstrations of reliability, reproducibility and mastered material consumption.

Work performed

THERMOELECTRIC MATERIAL SPECIFICATIONS
Automotive application
It was proposed to implement a TEG with cylindrical design immediately after the catalytic converter, to benefit from highest exhaust gas temperature possible.
Heavy Duty Diesel (HDD) truck application: engine models and their drive cycles were investigated for different applications and drive cycle key operating points were defined, and technical and economic requirements as well as cost targets were set.
Metallurgy applications: 1) waste heat recovery 2) autonomous temperature control : Thermoelectric panels for direct conversion of radiating heat into electricity are developed and demonstrated

CUSTOMIZED MULTIFUNCTIONAL MATERIALS
Objectives were to develop customized multifunctional GEN2 TE materials, i.e., with customized thermal and electrical conductivity, and customized shape and functionalization for each targeted application.
Material fine tuning to reach customized electrical and thermal conductivity
Ball-milling powder elaboration of the bulk silicide materials was optimised for Spark Plasma Sintering. The time process of ball-milling was dramatically reduced. The magnesium content of Mg2(Si,Sn) was reduced to a level allowing better thermal and oxidation stability, still with acceptable TE performance.
Similarly, the material development of HMS was oriented towards the production of a pre-alloyed powder. Various oxides were used to create nano-inclusions at joint grains in order to reduce thermal conductivity.
A second generation of Hafnium-reduced half-Heusler alloys was developed with success at lab scale. Heat treatments must be optimised to allow large scale production.
Ribbon silicide SiGe materials were further developed with reduced Ge content both for p-type as n-type legs.
Various metallisation recipes were investigated and are still under development towards efficient and stable joining of TE legs of the 3 categories of materials.
New TE leg design was developed to satisfy technical specifications set out in WP 1.
Similarly material protection coating is under development to allow all materials to withstand end-user environments.
All 3 value chains have deployed considerable efforts to develop thermoelectric device assembly strategies that allow reliable and durable use of modules in their intended working environment. Work is still in progress.

MATERIAL FABRICATION PROCESS UPSCALING
The objective of WP 3 was to upscale the GEN2 TE materials fabrication processes on existing pilot lines, from TRL 4 to TRL 7: upgrade the pilot lines and develop synergies in order to increase production volume (up to 100 kg batches for bulk silicides, 200 kg batches for Half-Heusler and 100 batches for ribbon silicides) and increase production yield (towards 5% faulty parts).
The pilot lines for half-Heusler and Ribbon-silicide materials are well on track.

IN-LINE AND OFF-LINE CHARACTERIZATION FOR PROCESS CONTROL ON PILOT LINES
WP Objectives are to develop in-line real-time characterization and process control, with macroscopic parameters correlated with micro- and nano-scale properties, in order to increase production robustness (10% standard deviation on ZT figure-of-merit and on electrical and thermal properties). Specifications for off line & in line toolsets were established. In-line characterization toolset for pilot lines to increase production robustness is still in progress. A traceability instrument for raw material and developed samples was set up.

MATERIAL QUALIFICATION AND DEMONSTRATION
WP Objectives are to demonstrate performance stability and efficiency improvement of the functionalized GEN2 TE materials in TEG prototypes for transport applications (automotive and heavy duty truck) and primary metal production process applications and metallurgy (waste heat recovery and autonomous sensor for industrial supervision), tested in a representative environment by the end-users (maximum 5% performance losses after 10,000 hours’ usage). For demon

Final results

Progress beyond state of the art and expected results
The project roadmap to achieve the overall objective of bringing GEN2 TE materials to the market bases on following specific objectives:
• Objective 1 (customized multifunctional GEN2 TE materials)
• Objective 2 (upscaling of the GEN2 TE materials fabrication processes)
• Objective 3 (in-line real-time characterisation and process control)
• Objective 4 (TEG Demonstration and validation)
• Objective 5 (technology transfer)
• Objective 6 (preparation of commercial deployment with a circular economy vision)
Potential impact
• Upscale GEN 2 TE materials on existing pilot lines for large-scale production and mass market exploitation
• Production processes and process control will be improved
• Cost reduction, environmental and safety legislations
• Target applications outside of the field of thermoelectricity
• Improving Innovation Capacities and Integration of Knew Knowledge
o Transport: Expected Fuel consumption reduction by 3%
o Process industry: harvesting of waste heat to improve energy and process efficiency

Website & more info

More info: http://www.integral-h2020.eu/.