Presentation of thermoelectric materials and devices for power generation by the University of Cyprus
Presentation of The University of Cyprus (UCY) and its role in ICARUS
The University of Cyprus (UCY) is located in Nicosia and is the first public University established in 1992. UCY participates in the ICARUS project with the Powder Technology Laboratory (PTLab) that is in the Department of Mechanical and Manufacturing Engineering.
PTLab’s research activities are related to materials for energy and environmental applications and the main running projects concern:
(a) Development and optimization of thermoelectric materials with potential application on energy systems and specifically the recovery of “waste” heat;
(b) 3D printing of metals based on Selective Laser Melting/Sintering;
(c) Processing of natural materials via mechanical methods for enhanced CO2 storage.
In ICARUS, the PTLab team (UCY) works on:
- The development of new thermoelectric silicides with high thermoelectric figure-of-merit using processed Si-kerf instead of high purity commercial silicon as starting material.
- The development of thermoelectric modules based on silicides prepared by Si-kerf starting material.
More information:
PTLab: https://www.ucy.ac.cy/powdertechlab/
Presentation of Thermoelectric materials and devices
Thermoelectric devices
Thermoelectric materials are n– and p-type semiconductors which are used for the fabrication of thermoelectric devices. A thermoelectric device is comprised of a number of modules; each of which consists of multiple thermoelectric couples. A thermocouple is made of two legs, an n– and a p-type.
A thermoelectric device creates a voltage when there is a difference of temperature on each side: The application of a temperature gradient across a thermoelectric device causes the diffusion of charge carriers: electrons and holes. As a result, an electric field is created, providing an electrical potential. Connecting the device to an external load generates an electric current. The operation of thermoelectric devices is based on the Seebeck effect and the heat source determines the temperature range in which the device is going to work.
Figure 1: Thermoelectric devices. Simulation of a Silicide TE module based on Si-kerf at ΔT=300K (a & b), and Seebeck effect (c).
Performances
The thermoelectric (TE) performance of materials is evaluated using the dimensionless figure of merit ZT = σS2T/κ, where σ, S, κ, T are respectively the electrical conductivity, the Seebeck coefficient, the total thermal conductivity and the operation absolute temperature, respectively.
Sustainability
In addition to the performance, in the field of thermoelectrics, it is also important to take sustainability into account since the overall ecological backpack for certain materials can be surprisingly high, especially for rare elements. Commonly used materials contain rare elements in the Earth’s crust, such as Te and Bi; thus using them in a wider range of TE applications – particularly at levels that could impact global energy use – is uncertain.
Silicide compounds are considered an advantageous choice not only because of their ample availability in nature, but also because of their non-toxicity that is consistent with the priority for environment- and human-friendly technology. Among silicide compounds, Mg2Si as well as Higher Manganese Silicide systems seem to be the most promising.
ICARUS first results
During the first period, the n-type materials have been successfully developed by using two types of Si kerf, RST 1-2 and RST ODIN-0821. The TE characterization of kerf-based silicide materials presents quite promising properties, reaching good TE efficiencies with ZT values close to 1. A typical synthesis route includes mechanical alloying as well as consolidation via hot press to further proceed to the module fabrication. The development of p-type Higher Manganese Silicide materials by using Si kerfs and the optimization of their TE properties is in progress, trying different synthesis routes such as mechanical alloying and arc melting and implementing appropriate hole dopants.
Figure 2: TE Module development
Next steps
The next steps include the optimization of the p-type as well as the module development and characterization.
