Development of a Scalable 10% Efficient Thermoelectric Generator
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Transcript of Development of a Scalable 10% Efficient Thermoelectric Generator
Development of a Scalable Development of a Scalable 10% Efficient Thermoelectric 10% Efficient Thermoelectric
GeneratorGenerator
D. Crane, J. LaGrandeur, L. Bell
DEER Conference, Detroit, MIAugust 15, 2007
Build on Recent SuccessesBuild on Recent SuccessesMaterials:
ZT substantially greater than unity has been demonstrated at places such as Michigan State, Research Triangle Institute (RTI), and MIT Lincoln Labs
Segmentation devices have successfully been demonstrated at Jet Propulsion Laboratory (JPL)
Thermodynamics and Heat Transfer:
Thermal isolation in the direction of flow that can improve cooling/heating performance by a factor of two
High power density designs that require 1/6 the thermoelectric (TE) material usage of conventional designs
TGM Development MethodologyTGM Development Methodology
Model, design and build fractional generator, first with low temperature TE material followed by high temperature TE material and finally segmented TE material
Validate performance model under varying operating conditions
Replicate fractional generator to scale up to >500 watts for low temperature TE material followed by similar scale up for high temperature (20W) and segmented TE materials
Integrate fractional generators with heat exchangers on the hot and cold side
Test and revalidate the performance model at varying operating conditions
Low Temperature BiLow Temperature Bi22TeTe33Subassembly Subassembly
Low temperature device built to continue learning process while high temperature material systems are being developedBi2Te3 thermoelectric generator module (TGM) output nominally targeted at > 500 watts
• Hot side fluid: oil, inlet temperature = 200 to 250C• Cold side fluid: water or glycol/water, inlet temperature = -5 to 30C
Peak Power = .969893
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Device Current (amps)
Elem
ent P
ower
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n1p1n2p2n3p3
Test Results of Single ModuleTest Results of Single Module((TThh = 190C, water bath = 20C)= 190C, water bath = 20C)
Solid Model Isometric & Cross Solid Model Isometric & Cross Section ViewsSection Views
Cold manifold
Hot manifoldTE circuit between hot and cold manifolds
Expansion bellows
Power Gen One Fifth Device
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Current (Amps)
Volta
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200C_-5C190C_-5C180C_-5C170C_-5C160C_-5C160C_6C160C_15C160C_25C131C_5C113C_5C98C_4C
27Jun07
Test ResultsTest ResultsMaximum Open Circuit Voltage >12VMaximum Open Circuit Voltage >12V
Power Gen One Fifth Device
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Current (Amps)
Pow
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200C_-5C190C_-5C180C_-5C170C_-5C160C_-5C160C_6C160C_15C160C_25C131C_5C113C_5C98C_4C
27Jun07
Test ResultsTest ResultsMaximum Peak Power of 130WMaximum Peak Power of 130W
Single plate(interfacial resistance = 2μΩcm2,
hot volume flow = 8 gpm (Xceltherm 600),cold volume flow = 8.85 lpm (water or glycol/water))
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hot fluid inlet temperature (C)
pow
er (W
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cold water inlet = 5C
cold water inlet = 15C
cold water inlet = 25C
cold glycol/water inlet = -5C
cold glycol/water inlet = 5C
cold glycol/water inlet = 15C
cold glycol/water inlet = 25C
cold water inlet = 4.68C, 8.85 lpm, hot oilflow = 4.3 gpmcold water inlet = 5.12C, 8.85 lpm, hot oilflow = 3.8gpmcold water inlet = 5.33C, 8.85 lpm, hot oilflow = 4.2 gpmcold water inlet = 6.60C, 8.85 lpm, hot oilflow = 7.5 gpmcold water inlet = 14.13C, 8.85 lpm, hot oilflow = 7.9 gpmcold water inlet = 24.51C, 8.85 lpm, hot oilflow = 8 gpmcold glycol/water inlet = -3.23C, 11.0 lpm,hot oil flow = 6.1 gpmcold glycol/water inlet = -6.02C, 10.9 lpm,hot oil flow = 6.0 gpmcold glycol/water inlet = -6.62C, 10.9 lpm,hot oil flow = 7.0 gpmcold glycol/water inlet = -5.68C, 10.9 lpm,hot oil flow = 6.9 gpmcold glycol/water inlet = -6.60C, 10.8 lpm,h t il fl 6 8
Peak Test Results Compared to SimulationsPeak Test Results Compared to SimulationsMeasured to simulated values vary by < 5%Measured to simulated values vary by < 5%
TE Figure of Merit for Current MaterialsTE Figure of Merit for Current Materials
Materials for segment layers are chosen to maximize ZT over each element’s exposed temperature range.
Materials of choice currently include p- and n-type skutterudite and Bi2Te3 as well as TAGS and n-type PbTe.
Ref: Modified from - http://www.its.caltech.edu/~jsnyder/thermoelectrics/
TE Couple Configuration TE Couple Configuration Alternatives with Segmented Alternatives with Segmented
ElementsElements
Traditional configuration
Alternative “Y” configuration
heat
heat heat
p-TAGS
p-CeFe3RuSb12
p-Bi2Te3
current
n-CoSb3
n-PbTe
n-Bi2Te3current
heat
heat heat
p-TAGS
p-CeFe3RuSb12
p-Bi2Te3
p-TAGS
p-CeFe3RuSb12
p-Bi2Te3
current
n-CoSb3
n-PbTe
n-Bi2Te3
n-CoSb3
n-PbTe
n-Bi2Te3current
p-CeFe3RuSb12
heat
heat
heat
p-TAGS
p-Bi2Te3
n-CoSb3
n-PbTe
n-Bi2Te3
current
p-CeFe3RuSb12
heat
heat
heat
p-TAGS
p-Bi2Te3
n-CoSb3
n-PbTe
n-Bi2Te3
current
heatheat
heatheat
heatheat
p-TAGS
p-Bi2Te3
n-CoSb3
n-PbTe
n-Bi2Te3
current
TGM Design ObjectivesTGM Design Objectives
State-of-the-art thermoelectric materialsThermally isolated elements in the direction of flowHigh power density designSegmented elements to maximize ZT over entire temperature rangeAbility to adjust segment thicknesses to increase TE material compatibility within elementsUse “Y” configuration to accommodate differing element thicknesses and differing thermal expansion coefficientsUse non-rigid joints to reduce the effects of thermal expansion mismatch
High Temperature TGM High Temperature TGM Developmental Prototype (20W)Developmental Prototype (20W)
TGM subassembly (cartridge heaters on hot side- full scale TGM will use hot gas heat exchangers) Solid model of fractional TGM
in its test fixture
20W Generator Build20W Generator Build
Completed halves of Completed halves of the 20W device, the 20W device, prior to the final prior to the final
assemblyassembly
Final assembled 20W Final assembled 20W device, plumbed and device, plumbed and
ready for testingready for testing
Test Results for the 20W Test Results for the 20W GeneratorGenerator
20W generator performance
(cold bath = 20C, six TAGS/PbTe couples, couple has 4 elements per side)(element dimensions = 3 x 3 x 2 mm)
(test #1 = solid, test #2 = dotted)
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current (A)
pow
er (W
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Th,avg = 149.0C, Tc,avg = 23.9CTh,avg = 149.6C, Tc,avg = 23.3CTh,avg = 198.2C, Tc,avg = 25.3CTh,avg = 200.3C, Tc,avg = 24.6CTh,avg = 247.8C, Tc,avg = 26.6CTh,avg = 249.5C, Tc,avg = 25.9CTh,avg = 297.2C, Tc,avg = 27.9CTh,avg = 299.3C, Tc,avg = 27.2CTh,avg = 347.6C, Tc,avg = 29.3CTh,avg = 348.8C, Tc,avg = 28.4CTh,avg = 398.5C, Tc,avg = 30.6CTh,avg = 398.1C, Tc,avg = 29.7CTh,avg = 446.6C, Tc,avg = 32.1CTh,avg = 448.8C, Tc,avg = 31.2CTh,avg = 471.8C, Tc,avg = 32.7CTh,avg = 474.7C, Tc,avg = 31.7C
Segmented TAGS/PbTeSegmented TAGS/PbTe--BiTe CoupleBiTe Couple
BiTe (0.6 mm)
PbTe (2mm)
BiTe (0.6 mm)
TAGS (2mm)
10% Efficiency Demonstration10% Efficiency DemonstrationPerformance is reproducible after Performance is reproducible after thermocyclingthermocycling
Segmented Couple PerformanceMarlow TAGS (Ti5Si3 metalization), PbTe, Bi2Te3
4 p-type, 6 n-type, TAGS (3 x 3 x 2mm), PbTe (3 x 3 x 2mm), Bi2Te3 (3 x 3 x 0.6mm)segments soldered together, alumina silica fiber paper insulation
01/10/07
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temperature difference (C)
effic
ienc
y (%
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cold bath = 20C (trial 1)
cold bath = -20C (trial 1)
cold bath = 20C (trial 2)
cold bath = 20C (trial 3)
cold bath = 20C (trial 4, unit turnedoff and restarted)
Next StepsNext StepsComplete assembly and testing of full-scale low temperature generator
Evaluate new design concepts that enhance performance and structural integrity of the device over the usage temperature range and during thermal cycling
Test fractional-scale prototype segmented element devices to analyze problem areas in the design, validate the model, and develop different segmentation techniques
Continue working with and testing new TE materials and new TE material combinations to push towards increasing average ZT
Continue working with partners to reduce interfacial resistance to 0.1 μΩcm2 at room temperature
Continue working on reducing heat losses from the system
Build full-scale high temperature TGM device using segmented elements