1. Developments in Thermoelectric Power Generation Technology
Marlow Industries, Inc.
Developments in Thermoelectric Power Generation Technology
Jim Bierschenk
Advanced Concepts in Semiconductor Materials and Devices for Energy Conversion
December 7th and 8th Sheraton Washington North Beltsville, Maryland

2. Marlow Industries, Inc. a subsidiary of II-VI Incorporated
About Marlow Industries, Inc.
Headquarters:
Dallas, TX (USA)
Thermoelectric quality and performance at industry competitive prices.
Industry:
Thermoelectric Solutions
Structure:
Operating Subsidiary
Founded:
1973
Employees
500+
Manufacturing:
Dallas, Vietnam
About II-VI Incorporated
Headquarters:
Saxonburg, PA (USA)
Industry:
Materials
Structure:
Public/(NASDAQ) IIVI
Marlow Industries- Dallas, TX
Center of Technical Excellence
Founded:
1971
Employees
>6000
II-VI named for their material origin in the compounds listed under II and VI columns on the periodic table: Zn, Cd, S, Se, and Te.
FY10 Revenue
$345M

3. Marlow Vertical Integration
TEC Assembly
Sub-System Assembly
Generic description of the BIP process - eliminates the free elements - we never lose element orientation from wafer to TEC allowing us to build with element geometries unachievable by traditional methods.

4. TE Cooling Markets and Applications
Defense, Space & Photonics
Thermal Night Sights
Range Finders and Target Designators
FLIR Calibration Systems
Telecommunications
Long Haul Laser Transmitters and Pump Lasers
Short and Mid Range Laser Transmitters/Receivers
Medical
Thermal Cyclers for Polymerase Chain Reactions
Liquid and air refrigerated compartments for blood analyzers
Industrial
Heated & Cooled automotive car seats
Point-of-sale boxes/small refrigerators
Semiconductor processing equipment
Consumer
Water chillers, wine chillers, refrigerators
Personal cooling – bedding, chairs, etc.
Gaming Applications

5. TE Cooling vs. Power Generation
Marlow TE Cooling
Defense
Space
Telecom
Medical
Industrial
Automotive
Consumer
Marlow TE Power Gen
Energy Harvesting
Direct Power Gen
Waste Heat Recovery
Co-Generation
Material research driven by waste heat recovery applications
Many diverse markets/applications
Extensive product customization
Flexible manufacturing capability
Thermal & mechanical design capability
High performance generator materials
Many diverse markets/applications
Extensive product customization
Flexible manufacturing capability
Thermal & mechanical design capability
Highest performing suite of TE materials

6. TE Power Generation Application Areas
Energy Harvesting
Microwatt to low milliwatt power to perpetually power wireless sensors
Battlefield sensors
Engine health monitoring
(temperature, vibration, etc)
Structural health monitoring
(aircraft, building, bridges, etc)
HVAC controls
Waste Heat Recovery
Convert heated waste exhaust streams to electric power for improve efficiency
Automotive WHR
Improve fuel economy
& reduce CO2 emissions
Minimize Fuel Consumption
on stationary generators
Convert Industrial Waste Heat to Electricity
Direct Power Generation
Burn a hydrocarbon fuel to produce heat – convert heat to electrical using TE Generator
Battery Replace Technology
Unattended Ground Sensors
Soldier power
Robot/UAV power sources
Battery Chargers
Auxiliary Power Units
Co-Generation
Heat produced from burning high energy density fuel.
Self-powered military equipment
Tent heaters
Cooking equipment (ration
tray heaters, griddles)
Cleaner burning 3rd world
cook stoves
Self powered fans for wood stoves and mosquito catchers 6 6

7. Marlow Power Generation
Marlow’s power generation focus is to develop:
Volume production processes for new high temperature materials
Volume production device assembly processes
Single and multistage (cascade capability)
Device and system level thermal and mechanical modeling
Material, device and subsystem test capability
Understand long term reliability
Focus on both low temperature (Bi2Te3) and high temperature applications

8. Energy Harvesting – Why Now?
Evolution of low power sensors, transmitters and power management electronics have made TE energy harvesting practical
Energy harvesting (also known as power harvesting or energy scavenging)

9. Thermoelectric Energy Harvesting
RLoad

10. The optimal TEG design for an energy harvesting application:
Thermally matches the combined hot and cold side thermal resistances
Electrically matches the electrical load
Has sufficient couples to provide the minimum threshold voltage for the step-up electronics at the desired source-to-ambient ΔT

11. Interdependence of Thermal and Electrical
The electrical load resistance impacts the thermal characteristics of the TEG

12. Energy Harvester TEG Transition
Traditional small TE Cooler Can Be used As Energy Harvesting TEG
Examples Marlow Energy Harvesting Devices, many of which were co-developed with Sandia National Lab
Prior to low threshold voltage electronics, low ΔT energy harvesting required:
TEGs with hundreds of couples (V is proportional to # couples and ΔT)
High thermal resistance (i.e. large TE element aspect ratios)
Today, with threshold voltages as low as 20 mV, low cost, traditional small TE devices can be used

13. Marlow High Temperature TEG Strategy
Enable a diverse array of thermoelectric power generation applications and markets by developing:
Volume production capability of TE generator devices that can operate to 500 C
Volume production capability for a suite of mid range TE materials
Accurate thermal and mechanical modeling of TEG modules and systems
Test capabilities for materials, devices and subsystems
Quantified reliability

14. Power Generation Materials
P Type Materials
Bi2Te3
N Type Materials
What power generation materials does Marlow use?
“High Temp” Bi2Te3 (both crystalline and MAM formats)
“PbTe” P and N, TAGS
P and N Skutterudites
Internal and University funded research on other new materials

15. Managing the ZT Envelope
Functionally Graded Materials
Elements made of single alloy with graded composition and/or doping
Segmentation
Elements made of 2+ alloys joined with metal layers that prevent interaction
Cascading
Multistage module with single P and N materials in each stage
capability
preferred

16. Prototype 50 mm square PbTe Module
“Traditional” high volume TE module assembly processes used for TE Generator assembly
Single & cascade TE devices
Brazes used instead of solder
Screen print braze paste w/ flux
Wet paste 1-time reflow in CAB Furnace
“Segmented” top ceramic to reduce thermal stresses (i.e. diced into smaller ceramic pieces after assembly)
Simple tools, minimal capital equipment
Prototype 50 mm square PbTe Module
Marlow CAB Furnace for Braze Assembly
Common device assembly process for both PbTe and Skutterudite materials (different barrier)

17. 2 stage PbTe/Bi2Te3 modules
Prototype TE Generators
2 stage Skutterudite/Bi2Te3 modules
50 mm square Skutterudite modules
2 stage PbTe/Bi2Te3 modules
25 mm square PbTe modules

18. TE Device Test Development
In-house TEG efficiency tester
Vacuum or inert atmosphere
500 C capability
Up to 40 mm cross sections
Unique device calibration to quantify heat losses
Material Seebeck and resistivity tests to 500 C
Production test capabilities using Harman technique module tester at elevated temperatures
Cycling and constant temperature aging test stand in development

19. Device Level Modeling
Equations governing thermoelectric device behavior (Ioffe, Goldsmid, etc) were derived assuming constant TE material properties
For improved accuracy, these equations are typically used with temperature dependent properties
For cooling, the equations lose accuracy at large ΔT
These fundamental equations were re-derived without the underlying assumption of constant material properties
Provides more accurate modeling of TE coolers and power generators with large ΔTs
Validated with experiment and with full 3D thermoelectric simulations in ANSYS

20. Thermoelectric System Modeling
Model Validation
System test on engine dyno for automotive waste heat recovery system
Output matches Marlow system model prediction

21. DOE CRADA Oak Ridge National Lab/Marlow
Objective: “To evaluate materials and devices for waste-heat recovery applications in automotive and heavy vehicle applications up to 500°C.“
Project Goals:
Thermoelectric and mechanical material properties for TE material
Thermal and mechanical material properties for any supporting material
Develop ANSYS models to evaluate TE devices in automotive applications
Develop life prediction models
Experimental verification of models

22. Power Generation Benefits from Improved in Bi2Te3
High ZT Inorganic Colloidal Nanocrystal thermoelectric material
Bulk material format addresses a wide range of heat flux applications
Phonon blocking to reduce lattice thermal conductivity
Quantum confinement enhancement of the Seebeck coefficient
Scalable, low cost material fabrication process
Device format and design that minimizes all thermal and electrical losses
High voltage, low current operation enabled by Build-in-Place TEC assembly process
Low electrical contact resistance on a bulk TE material
High ZT material  High ZT devices
Program: Active Cooling Module (ACM)
Program Mgr: Avi Bar-Cohen

23. Thank You! Marlow Industries, Inc. 10451 Vista Park Road
Dallas, TX
Jim Bierschenk