1. Quest for Materials for Renewable Energy Applications
Stefan Stefanoski, Ph.D.
Department of Electrical and Renewable Energy Engineering
Oregon Institute of Technology, Wilsonville, OR
TECH Talks 2016
May 6, 2016

2. Background St. Cyril and Methodius University
Natural Sciences and Mathematics
Skopje, Macedonia
BS in Applied Physics (2005)
University of South Florida
Department of Physics
Tampa, FL, USA
MS (2010) and PhD (2012)
in Applied Physics
Oregon Institute of Technology
Department of EREE,
Wilsonville, OR, USA
MS in REE (2017)
Adjunct Professor
Max Planck Institute
Institute for Chemical Physics of Solids
Dresden, Germany
Visiting Scientist (2011)
Carnegie Institution for Science
Geophysical Laboratory
Washington, D.C. USA
Postdoctoral Fellow ( )
Quest for Materials for Renewable Energy Applications
S. Stefanoski

3. Why Are Materials Important?
Mars Exploration Rover: solar panels providing 600 W
Wind turbine-blades: made of GRP = carbon or glass-fiber reinforced thermosetting plastic (glass fibers are 1/10 of the prices of carbon fibers
Quest for Materials for Renewable Energy Applications
S. Stefanoski

4. New Allotrope of Silicon, Si24
1000 ton
Multianvil Press
D. Y Kim, S. Stefanoski et al. Nature Materials, 14, , (2015)
Temperature: 800 0C
Pressure: 8 GPa
Zr2O3 insulation
Ta heater and capsule
MgO
Mixture of Na-Si in 1:6 ratio inside Ta capsule
Quest for Materials for Renewable Energy Applications
S. Stefanoski

5. New Allotrope of Silicon, Si24
5 m
400 K RT
= 1.3 eV
AM1.5 radiative limit
Radiative limit with
potential fluctuations
D. Y Kim, S. Stefanoski et al. Nature Materials, 14, , (2015)
Quest for Materials for Renewable Energy Applications
S. Stefanoski

6. Thermoelectric Effect - Thermoelectricity+ - +
Quest for Materials for Renewable Energy Applications
S. Stefanoski

7. Thermoelectric Generator
Seebeck
Effect
Peltier
Effect
S = Seebeck coefficient (V/T)
 = electrical conductivity
 = thermal conductivity (lattice
+ electrons)
High S  generate the largest V for a given T (S = V/T);
High   device carries the largest current possible for a given V;
Low   heat is not conducted through the legs, and T is easily maintained.
Quest for Materials for Renewable Energy Applications
S. Stefanoski

8. Thermoelectric Materials for Automotive Applications
Automotive Energy Flow Diagram
Quest for Materials for Renewable Energy Applications
S. Stefanoski

9. Radioisotope Thermoelectric Generator (RTG)
Voyager
Cassini
Quest for Materials for Renewable Energy Applications
S. Stefanoski

10. Thermoelectric Materials
Skutterudites
Half-Heuslers
Alloys Te Pb
Clathrates
Yb14MnSb11
Chalcogenides
Quest for Materials for Renewable Energy Applications
S. Stefanoski

11. Synthesis and Properties of Clathrates
X (Na-content)
[1] S. Stefanoski et al. Chem. Matter. 23, 1491, (2011)
[2] S. Stefanoski et al. in The Physics and Chemistry
of Inorganic Clathrates, ed. G. S. Nolas, (2014)
Quest for Materials for Renewable Energy Applications
S. Stefanoski

12. Summary, Projections, Recommendations
Materials relevant for Renewable Energy applications are in the focus of scientific R&D: heavy funding of Universities and National Labs; multiple openings for MS/PhD positions are available.
“Frontiers in Crystalline Matter: From Discovery to Technology”, National Academies Press, 2009: “ The U.S. has an urgent need for increased research and discovery and crystal growth of materials”
Every technologically-relevant application starts with the synthesis and characterization (crystal structure, electrical, thermal, optical, and other properties) of materials.
Global Solar Forecast
Global solar installations will grow to 64.7 GW in The top countries are China, U.S. and Japan. IF materials with higher solar-absorption potential are available, industry will grow even further.
Si24 is a promising candidate to replace conventional silicon for PV applications. Scaling-up is needed before commercialization.
Quest for Materials for Renewable Energy Applications
S. Stefanoski

13. Thank you! Quest for Materials for Renewable Energy Applications
S. Stefanoski