Micro- & Nano-Technologies Enabling More Compact, Lightweight Thermoelectric Power Generation & Cooling Systems

2011 Thermoelectrics Applications WorkshopSan Diego, CA5 January 2011

Terry J. Hendricks, Shankar Krishnan, Steven Leith

Pacific Northwest National LaboratoryEnergy & Efficiency Division

MicroProducts Breakthrough InstituteCorvallis, OR

We Sincerely Thank Our Sponsor: John Fairbanks, Gurpreet SinghU.S. Department of Energy

EERE - Office of Vehicle Technologies

Advanced Thermoelectric System DesignSingle & Segmented Material TE Legs

2

Qh,out

Qc,in

Power InPower In

Th

N

Tc

Compartment Cooling Flow

Hot-Side Rejection Flow

Tcold

Cold Side Heat Exchanger

Hot Side Heat Exchanger

Tamb , mhAmbient

•

Tcabin , mc•

P

I

Power InPower In

Th

N

Tc

Compartment Cooling Flow

Hot-Side Rejection Flow

Tcold

Cold Side Heat Exchanger

Hot Side Heat Exchanger

Tamb , mhAmbient

•Tamb , mhAmbient

•

Tcabin , mc•Tcabin , mc•

P

I

Thermoelectric Heating/CoolingLow-Temperature Systems

Qh,in

Power Out

Tcold

N1

Thot

Industrial & Vehicle Exhaust Flow

Environment Ambient Flow

Tcold

Qc,out

External Load, Ro

Hot Side Heat Exchanger

Cold Side Heat Exchanger

Tamb , mcAmbient

•

Tex , mhExhaust

•

P2

Thermoelectric Power GenerationHigh-Temperature Systems

P1

N2

Generally Do Cascading Rather Than Segmenting to Achieve Large ∆T

Advantages of SegmentingDepends on Available ∆T

0 200 400 600 800 1000 12000

0.02

0.04

0.06

0.08

0.1

0.12

Power [W]

Max

imum

Effi

cien

cy

0.237(W/cm2) →

0.403(W/cm2) →

0.589(W/cm2) →

0.808(W/cm2) →

1.06(W/cm2) →

1.34(W/cm2) →

1.66(W/cm2) →

2.02(W/cm2) →

2.41(W/cm2) →

2.83(W/cm2) →

3.28(W/cm2) →

3.77(W/cm2) →

←T h

=490

(K)

←T h

=515

(K)

←T h

=540

(K)

←T h

=565

(K)

←T h

=590

(K)

←T h

=615

(K)

←T h

=640

(K)

←T h

=665

(K)

←T h

=690

(K)

←T h

=715

(K)

←T h

=740

(K)

←T h

=765

(K)

←T h

=790

(K)

←T h

=815

(K)

←T h

=840

(K)

←T h

=865

(K) Tcold=380 (K)

Tcold=415 (K)Tcold=450 (K)Constant Thot

0 200 400 600 800 1000 12000

0.02

0.04

0.06

0.08

0.1

0.12

Power [W]

Max

imum

Effi

cien

cy

98(W/kg) →

165(W/kg) →

243(W/kg) →

335(W/kg) →

441(W/kg) →

561(W/kg) →

696(W/kg) →

846(W/kg) →

1012(W/kg) →

1194(W/kg) →

1392(W/kg) →

1608(W/kg) →

1841(W/kg) →

←T h

=490

(K)

←T h

=515

(K)

←T h

=540

(K)

←T h

=565

(K)

←T h

=590

(K)

←T h

=615

(K)

←T h

=640

(K)

←T h

=665

(K)

←T h

=690

(K)

←T h

=715

(K)

←T h

=740

(K)

←T h

=765

(K)

←T h

=790

(K)

←T h

=815

(K)

←T h

=840

(K)

←T h

=865

(K) Tcold=380 (K)

Tcold=415 (K)Tcold=450 (K)Constant Thot

TE Power GenerationHeat Exchanger / TE Device Integration Requirements

Regions of Higher Specific Power Also Associated with Higher Heat Flux Regions

Hot Side Heat Exchanger Dictates: TE Specific Power TE Power Flux TE Volumetric Specific

Power

Heat Fluxes > 15 W/cm2 inPreferred Design Regimes Hot-side Cold-side

Segmented Skutterudite/Bi2Te3 Materials

hm

Preferred TEDesign Regime

Texh= 873 KTamb = 300 K

= 0.1 kg/sUAh = 377 W/K

TE CoolingHeat Exchanger / TE Device Integration Requirements

250 300 350 400 450 500 550 6000

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

Cooling Capacity [W]

Max

imum

CO

P

←1421(W/kg)

←1294(W/kg)

←1173(W/kg)

←1057(W/kg)

←Th =340(K)

←Th =337(K)

←Th =334(K)

←Th =331(K)

←Th =328(K)

←Th =325(K)

←Th =322(K)

←Th =319(K)

←Th =316(K)

Tcold=280 (K)Tcold=270 (K)Tcold=260 (K)Constant Thot

Distributed Cooling Systems

Typical COP – Cooling Capacity – Power / Mass Relationship Shown Distributed TE Cooling Systems

Create Lower Heat Flows per Unit

Higher COP’s Lower Power / Mass

Generally Right Directions forAutomotive Distributed Cooling

p-type NPB BixSb2-xTe3*

n-type Bi2Te3 – Bi2Se3

* Poudel, B., Hao, Q.H., Ma, Y., Lan, Y., Minnich, A. Yu, B.,Yan, X., Wang, D., Muto, A., Vashaee, D., Chen, X., Liu, J.,Dresselhaus, M.S., Chen, G., Ren, Z., 2008, “High-Thermoelectric Performance of Nanostructured Bismuth Antimony Telluride Bulk Alloys,” Sciencexpress, 10.1126, science.1156446.

UAc = 40 W/KTcabin = 298 K

100 150 200 250 300 350 400 4500

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

Qc Per Mass[W/kg]

Max

imum

CO

P

←T h

=340

(K)

←T h

=337

(K)

←T h

=334

(K)

←T h

=331

(K)

←T h

=328

(K)

←T h

=325

(K)

←T h

=322

(K)←

T h=3

19(K

)←T h

=316

(K)

Tcold=280 (K)Tcold=270 (K)Tcold=260 (K)Constant Thot

p-type NPB BixSb2-xTe3

n-type Bi2Te3 – Bi2Se3

UAc = 40 W/K

Tcabin = 298 K

Preferred TEDesign Regime

TE CoolingHeat Exchanger / TE Device Integration Requirements

0.4 0.5 0.6 0.7 0.8 0.9 10

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

Qc Per Area [W/cm2]

Max

imum

CO

P

←T h

=340

(K)

←T h

=337

(K)

←T h

=334

(K)

←T h

=331

(K)

←T h

=328

(K)

←T h

=325

(K)

←T h

=322

(K)

←T h

=319

(K)←

T h=3

16(K

)

Tcold=280 (K)Tcold=270 (K)Tcold=260 (K)Constant Thot

Preferred TEDesign Regime

p-type NPB BixSb2-xTe3

n-type Bi2Te3 – Bi2Se3

UAc = 40 W/K

Tcabin = 298 K

Distributed TE Cooling Systems Generally Move Into Regions of: Higher COP’s Higher Specific Cooling Capacity (Compact, Lightweight Systems) Higher Heat Fluxes (Higher Heat Transfer Coefficients)

Generally Higher Performance Heat Exchanger SystemsRequired

PNNL Developing High-Performance Microtechnology Heat Transfer Technologies

TE Power Generation From TQG Exhaust Energy Recovery Hot-Side Heat Exchanger Designs Being Developed & Refined CFD Analyses & Experimental Testing Helping to Refine Designs Design Performance Goals:

High Thermal Transfer Flux (~10-12 W/cm2) in Hot-Side Heat Exchanger Low Pressure Drop (< 1 psi) Heat Flux vs. Pressure Drop Characteristics Quantified for Different Design Approaches

Different Materials Can Be Used: Stainless Steel, Inconel, Haynes Materials, Ceramics

COMSOLCFD Analysis

Air Supply HeatersWater-Cooled Heat Sink

Hydrodynamic Conditioning& Mixing

Design Point

60 kW TQG Design Conditions: 0.158 kg/sec, 780 K

Rectangular Honeycomb Design

Design Target

Several Workable Design Points Identified

ε = 0.93

7

Co-Functional Power / Cooling Systems Co-Functional Integration of 3 Power & Cooling Technologies

Organic Rankine Cycle Based Cooling Thermoelectric Power Generation Micro/Nano Heat Transfer Technologies (Microchannel Heat Exchangers)

System Designed, Fabricated & Tested at PNNL MBI TE Topping Cycle

Step-Down (Lower) Input Temperatures to ORC

Simultaneously Produce Useful Power

E/C ORC to Provide Useful Cooling Capacity Known & Demonstrated Components in this Phase Reduce Cost & Risk & Development Time

Microchannel Heat Exchangers Used toDramatically Reduce Volume & Weight

Funded by U.S. Army RDECOM

High Temperature HEX

Thermoelectric Generator

Expander/CompressorHeat Pump

Electrical Power

Heat Rejectionto SurroundingsHeat in from

Cooling Space

Hot ExhaustStream

ThermalResistance

ThermalResistance

Qin,H

Qout

Waste Heat forTotal Energy

RecoverySpentExhaust

Qtot,outQin

High Temperature HEX

Thermoelectric Generator

Expander/CompressorHeat Pump

Electrical Power

Heat Rejectionto SurroundingsHeat in from

Cooling Space

Hot ExhaustStream

ThermalResistance

ThermalResistance

Qin,H

Qout

Waste Heat forTotal Energy

RecoverySpentExhaust

Qtot,outQin

CFPC – Fabrication & Test First-in-Class, Pioneering System TEG Power System Uses

MicroChannel Heat Exchangers Stainless Steel Air HX On Hot-Side Aluminum R245fa HX on Cold-Side

High-Temperature Bi2Te3 Modules First-Ever 320°C Bi2Te3 Modules

System Size Dimensions: 30” X 30” X 19” Weight: ~100 kgs

System Fabrication Completed System Testing Completed

Exhaust Heat Simulated with Electrical Heater / Blower System

Stable System Operation Many Performance Metrics Satisfied

8

TEG Power System

Co-Functional System Build-up

ORC Boiler

Scroll Expander

MicroTechnology in Distributed TE HVAC Systems DOE Project in Advanced TE HVAC

Systems for Automobiles Zonal Climate Control for Thermal Comfort Compact Microtechnology Heat Exchangers

Reduce Weight & Volume Low Cost Manufacturing

Coupled with Compact TE HVAC Systems Wicking Systems for Water Management

Leveraging Nano-Scale Coating Technology

Significant Microtechnology Cost Modeling Cost Sensitivities Identified Low-Cost Manufacturing Avenues Being Developed Sensitivities to Production Volumes Material and Process Cost Drivers

9

Hybrid / PHEV Vehicles

Nano-Scale Coatings

Cost Modeling Approach

PNNL Nano-Scale Coatings Impact Surface Hydrophobicity and Surface Boiling Heat Transfer ZnO on Al Substrate Rave = 315 nm θ = 20.3° Can Make Super-Hydrophilic

Surfaces θ= 0° Bare Aluminum

Substrate θ=104° Huge Ramifications on Water

Management / Transport

0.005 0.030 0.055 0.080 0.105 0.130 0.155

NaOH Concentration [mol/L]

10

30

50

70

90

Conta

ct

Angle

[d

egre

es]

Set 1Set 2

Heat Flux, kW/m2H

eatT

rans

ferC

oeffi

cien

t,kW

/m2 K

101 102 103

5

10

15

20

2530

Al - Unique Surface (18)Cu - 30 Contact Angle (Fl)Al - 20 Contact Angle (Fl)Bare Al

PNNL Developing High-Performance Microtechnology Heat Transfer Technologies TE Cooling / Heating

Automotive Distributed HVAC Systems A Number of Microtechnology Designs Are Being Investigated An Example of One Such Design Is Presented Here

Heat Transfer vs. Pressure Drop Characteristics Quantified

0.4

0.5

0.6

0.7

0.8

0.9

1

0.015 0.017 0.019 0.021 0.023 0.025 0.027 0.029 0.031 0.033 0.035

Volume of Metal, Liters

Effe

ctiv

enes

s

135

160

185

210

235

260

285

310

335

Hea

t T

ran

sfer

Rat

e, W

Copper

Aluminum

Effect of Channel Aspect Ratio on Effectiveness

Modeled Channel Aspect Ratio: 2:1 – 8:1

Wall Thickness on Order of 150 - 350 um

4 cm

2 cm

8 cm

4 cm

2 cm

8 cm

7

7.5

8

8.5

9

9.5

10

10.5

11

0.4 0.5 0.6 0.7 0.8 0.9 1

Effectiveness

Hea

t T

ran

sfer

Den

sity

(Q/V

olm

etal

), k

W/L

t.

Copper

Aluminum

Effect of Channel Aspect Ratio on Flux Density

4 cm

2 cm

8 cm

4 cm

2 cm

8 cm

Process-Based Microtechnology Cost Modeling Microtechnology Manufacturing Cost is Key to Automotive Applications Process-Based Cost Modeling

Cost Sensitivities Identified

Low-Cost Manufacturing Avenues Being Developed

Sensitivities to Production Volumes

Material and Process Cost Drivers

System Performance Modeling Integrated with Cost Modeling to Identify Low-Cost, Manufacturable Microtechnology Designs

Cost Modeling Incorporates Critical Process & Cost Elements Prioritizes R&D Investment Plans & Enables Business Decisions Compared 3 Process Approaches for Microtechnology Heat Exchanger

Design Discussed Above Cost Modeling for High-Temperature Exhaust Recovery Applications Cost Modeling for Low-Temperature Advanced Cooling Applications

Process Based Cost ModelingBottom-Up Approach to Estimating Cost of Goods Sold (COGS)

Based on Operation of Virtual Manufacturing Line – Breaks Down Cost by Unit Process

Cost of Goods Sold (COGS)

Variable CostsFixed Costs

Capital EquipmentMaintenance

Facilities/Buildings

Direct LaborDirect Materials

Indirect MaterialsUtilitiesProcess-Based Cost

Model Algorithm

Model Outputs

Start with Process Flow and Associated Equipment Set

Process COGS vs. Volume and ParetoCost SensitivityID Cost Drivers

Not IncludedOverhead & Profit

InsuranceTaxes

Inventory Management AccountingMarketing

Sales

Capital EquipmentLabor

MaterialsEnergy

FacilitiesMaintenance

Cost Elements

Model Inputs

Process Flow

Unit Process 1Unit Process 2Unit Process 3

Etc.

Process to Process ComparisonsDefine Fabrication Toolbox

Inform R&D Agenda

Contact: Steven.Leith@pnl.gov

$0

$20

$40

$60

$80

$100

$120

$140

$160

1,000 10,000 100,000 1,000,000

Prod

ucti

on C

ost (

USD

/Dev

ice)

Production Volume (Vehicles/yr)

Integrated HTX COGS Estimation and Pareto : Process "A"

Direct Materials

Sheet Cutting

Sheet Clean and Prep

Weld 1

Singulation 1

Weld 2

Singulation 2

8 HTX per Vehicle / Aluminum HTX / 2 cm x 4 cm x 8 cm HTX Dimensions

$155.00

$30.75$20.50 $19.50

Process Relies on Significant Laser Use Not a Good Design + Process MatchExisting, Scalable Fabrication Processes and OTS Production Equipment

$0

$5

$10

$15

$20

$25

$30

$35

$40

$45

1,000 10,000 100,000 1,000,000

Prod

ucti

on C

ost (

USD

/Dev

ice)

Production Volume (Vehicles/yr)

Integrated HTX COGS Estimation and Pareto : Process "B"

Direct Materials

Sheet Cutting

Sheet Clean and Prep

Braze 1

Singulation 1

Braze 2

Singulation 2

8 HTX per Vehicle / Aluminum HTX / 2 cm x 4 cm x 8 cm HTX Dimensions

$40.00

$7.50$4.50 $4.25

Direct Materials Primary Cost Driver at Production VolumesExisting, Scalable Fabrication Processes and OTS Production Equipment

$0

$5

$10

$15

$20

$25

$30

$35

$40

$45

$50

1,000 10,000 100,000 1,000,000

Prod

ucti

on C

ost (

USD

/Dev

ice)

Production Volume (Vehicles/yr)

Integrated HTX COGS Estimation and Pareto : Process "C"

Direct Materials

Sheet Cutting

Sheet Clean and Prep

Braze 1

Singulation 1

Braze 2

Singulation 2

8 HTX per Vehicle / Copper HTX / 2 cm x 4 cm x 8 cm HTX Dimensions

$46.50

$13.75$11.00 $10.50

Direct Materials Cost for Copper is 4x that for Aluminum Drives CostImproved Yield and Cycle Times in Copper Braze vs. Aluminum Braze

Vehicles HTX Units $/Unit Capital Equipment ($k) $/Unit Capital Equipment ($k) $/Unit Capital Equipment ($k)1,000 8,000 $153.90 $1,705 $40.09 $1,400 $46.48 $1,40010,000 80,000 $30.85 $5,455 $7.44 $1,400 $13.87 $1,400

100,000 800,000 $20.54 $43,830 $4.55 $2,550 $10.91 $2,0501,000,000 8,000,000 $19.55 $459,300 $4.19 $17,750 $10.61 $14,750

Process A Process B Process CAluminum Copper

Annual Volume

Summary - Process Comparisons

1.25 mm4 cm

2 cm

8 cm

1.25 mm4 cm

2 cm

8 cm

4 cm

2 cm

8 cm

Summary Microtechnology Thermal Systems Required to Enable Compact, Light weight

TE Systems TE Power Generation TE Cooling / Heating

Microtechnology Thermal Systems Successfully Integrating into TE Systems Process-Based Cost Modeling is Critical to Developing Low Cost

Manufacturing Pathways, Processes, and Materials Cost Modeling Incorporates Critical Process & Cost Elements Cost Sensitivities Identified Low-Cost Manufacturing Avenues Being Developed Sensitivities to Production Volumes Material and Process Cost Drivers Identified

System Performance Modeling Integrated with Cost Modeling to Identify Low-Cost, Manufacturable Microtechnology Designs

Prioritizes R&D Investment Plans & Enables Business Decisions

20

Questions & Discussion

We are What We Repeatedly do. Excellence, Then, is not an Act, But a Habit.

Aristotle

Thank you for your time and interest