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​Medium- and high-temperature thermoelectricity: an environmentally-friendly technology for recovering waste heat from vehicle exhaust

Thermoelectricity (high/medium temperature)

Published on 25 October 2016

Thermoelectric materials are one of our research areas at Liten. While these materials—which can transform heat into electricity via the Seebeck effect or, conversely, transfer heat from one material to another under an electrical field via the Peltier effect, for example—have been the focus of ample research in recent years, industrial-grade systems that use thermoelectric technology for waste-heat recovery are few and far between. At Liten we are tackling the issue head on, with the goal of developing systems capable of penetrating the emerging waste-heat-to-energy market. In particular, effective heat-to-electricity conversion systems could reduce motor vehicles’—and entire transportation systems’—energy consumption. How do these systems work? The waste heat that would normally be lost in the form of exhaust is converted into electricity to power the vehicle’s electric components.


One of today’s challenges is developing environmentally-friendly and economical thermoelectric materials—which means that the underlying raw materials must be abundantly available, non-toxic, and affordable. At Liten, our research spans studying and optimizing materials and heat-exchanger system design, integration, and management. We leverage capabilities like ab initio modelling to make the best materials choices and multiphysics modelling to right-size components. Finally, we master a full range of manufacturing techniques for thermoelectric components: powder metallurgy, sintering to final specifications, polishing, metallization, stamping, and assembly.


Our materials researchers are particularly well-versed in three crucial technologies:

-    Solid materials for electric power generation

-    Solid materials for thermal flow sensors

-    Thin-layer materials for thermal flow sensors


We also possess the necessary equipment for scaling up high-performance thermoelectric materials. For example, we developed silicon-based materials like SiGe, MgSiSn, MnSi using an atomized powder process compatible with high production volumes. These materials offer some very desirable properties, are reasonably affordable, and are easy to synthesize. We carry out this type of development work in laboratory conditions, of course, but can also scale up to small test runs of up to 3 kg per week, right at our own powder metallurgy center.


BENEFITS


  • Direct heat-to-electricity conversion for energy savings
  • Compact form factor available in several sizes and power capacities
  • Environmentally-friendly materials

PROJECTS


  • We produced silicide-based thermoelectric materials in batches of several kilograms for HotBlock OnBoard, a CEA spinoff founded in 2012 that is developing a thermoelectric generator for marine motor exhaust pipes. The materials were used to make functionalized terminals, which were tested under hot gas, demonstrating factors of merit well in excess of the current state of the art. An 85-watt (electric power) heat exchanger was then developed and tested. The technology was transferred to HotBlock OnBoard, and the company subsequently developed a heat-exchanger with a capacity of more than 1.5 kilowatts electric power.
  • In research conducted under the Renoter2 project (financed by the French Single Interministerial Fund and Bpifrance, France’s public investment bank), we made several thousand thermoelectric terminals from abundantly-available, environmentally-friendly materials (MgSiSn/MnSi) using a volume process; the terminals were integrated into Valeo heat exchangers that will be tested on Renault and Renault Trucks vehicles. 
  • We are also involved in the Phims project (funded by the French National Research Agency), whose focus is to investigate a material—MnSi—and its thermoelectric properties. MnSi is very cheap and therefore potentially compatible with the needs of non-niche industrial markets.

FACTS AND FIGURES
  • Around 20 researchers
  • 40 patents
  • ​​Publications: 
Carrete J, Li W, Mingo N, Wang S, Curtarolo S. February 19, 2014. Finding Unprecedentedly Low-Thermal-Conductivity Half-Heusler Semiconductors via High-Throughput Materials Modeling. Physical Review X 4: 011019.

Wunderle B, Springborn M, May D, Manier C A, Abo Ras M, Mrossko R, Oppermann H, Xhonneux T, Caroff T, Maurer W, Mitova R. May 27–30, 2014. Double-Sided Cooling and Transient Thermo-Electrical Management of Silicon on DCB Assemblies for Power Converter Modules: Design, Technology and Test. Itherm 2014: IEEE InterSociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems: 851–861.

Navone C. Process Scalability for Promising Si Based Thermoelectric Materials. 2015 TMS Annual Meeting & Exhibition.
Find out more
  About thermoelectric materials that meet the specifications of the automotive industry (click here)
  About the the vibrational spectrum of manganese silicides (click here).

FACTS & FIGURES