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INitiative to bring the 2nd generation of ThermoElectric Generators into industrial ReALity

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

Reporting period: 2018-06-01 to 2019-11-30

A so-called second-generation thermoelectric (GEN2 TE) materials has emerged: silicides and half-Heusler. Based on these low-cost, mostly earth-abundant elements and eco-friendly materials, ThermoElectric Generators (TEGs) can impact positively European industry and society by converting waste heat into electricity.
The aim of INTEGRAL is to upscale the GEN2 TE material technology on existing pilot lines in order to address mass markets TE needs in three value chains:
• Automotive and heavy duty trucks value chains, where combustion engines use only a part of the fuel to move the vehicle. The rest is heat lost to the environment. INTEGRAL TE generators will make it possible to convert this to electricity
• Industry waste heat recovery value chain: metal, glass and ceramics production and conversion are made at high temperature, and the thermal energy is usually wasted at the end of the processes. Instead, it will be harvested to electricity by INTEGRAL TEGs
INTEGRAL has developed systems integrating multifunctional TE materials through material customization, new techniques for characterization and process control and up-scaled pilot-line demonstrations of reliability, reproducibility and mastered material consumption.
It is generally considered that high energy costs favour all technical solutions allowing energy savings. However, energy is currently still comparatively cheap. This makes INTEGRAL solutions less attractive than they should be, while in many economic sectors the geostrategic and political situation is changing fast, causing many uncertainties. Someday inevitably, energy prices will increase, and INTEGRAL solutions will be ready for implementation, provided they get appropriate incentives from public authorities. For instance, so-called CO2 certificates are under discussion, the costs of which are not fixed yet. They will affect the cost of oil-based electricity and thereby increase the interest for TEGs.
Customized multifunctional GEN2 TE materials were developed, i.e. with customized thermal and electrical conductivity, shape and functionalization for each targeted application.
Ball-milling powder for 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 up to 500°C, still with acceptable TE performance. The ball-milling pilot plant powder capacity upscaling was demonstrated at 10 kg/day.
Pre-alloyed HMS powder was developed including various oxides to create nano-inclusions at joint grains so as to reduce thermal conductivity.
A second generation of Hafnium-reduced half-Heusler alloys was developed, whose production was upscaled to 40 kg/batch.
Ribbon silicide SiGe materials were further developed with reduced Ge content both for p-type as n-type legs with a production capacity of 50 kg/day of material and 10 TE panels per day.
Various metallisation and joining recipes were developed for efficient and stable assembly of TE legs of the 3 categories of materials.

In-line real-time characterization and process control were developed, with macroscopic parameters correlated with micro- and nano-scale properties, in order to increase production robustness.

The performance stability and efficiency improvement of the functionalized GEN2 TE materials was demonstrated 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. Four demonstrators were built and successfully tested in full-scale environment.

This Work provided the partners and the future holders of the TEG production lines with necessary information to prepare for the future production take-off of the INTEGRAL products and services. TEG and applicative demonstrator lifecycle analysis and their environmental impact, HSE issues on production processes, cost targeting and total cost of ownership of each TEG prototype, and also standardisation preparation for the aimed markets (transport and industry).
All partners have developed business plans for a successful introduction of their project results to the market.
The overall objective of bringing GEN2 TE materials to the market bases needed significant progress over state of the art:
• Customized multifunctional GEN2 TE materials. On the 3 categories of materials, progress has been made on compositions to allow large-scale production, thermoelectric performance, stability and functionality in TE modules and generators at high temperature
o Improved Mg2(Si,Sn) and high-manganese silicide (bulk), stable at 500°C
o Improved SiGe ribbon silicides with new doping
o Half-Heusler alloys with reduced hafnium
• Upscaling of the GEN2 TE materials fabrication processes. Semi-industrial production demonstrated at TRL 7
• In-line real-time characterisation and process control
• TEG Demonstration and validation: four demonstrators were being built in collaboration with end-users and have proved the concepts described above.

Potential impact
• Upscaled pilot lines in INTEGRAL are the first ever industrial production plants of GEN 2 TE materials
• The use of TEGs in the transport sector (cars and trucks) will allow significant fuel consumption reduction
• Harvesting of waste heat may produce e.g. up to 1500 GWh/year in the European steel industry and 1350 GWh/year in the European glass industry
From Silicon wafers to TE modules
Half-Heusler TE legs
Bulk Silicides TE half-rings
Half-Heusler 20 kg ingot
Thermagy infographics
Thermagy Panel
Silicon-based TE module
Thermagy Module