Thermoelectric Generators (TEG) with high power density for application in hybrid cars
www.DLR.de • Chart 1
M. Kober H. Friedrich German Aerospace Center Institute of Vehicle Concepts Pfaffenwaldring 38-40 70569 Stuttgart Germany
EMN Orlando > 2016-02-23 > TEG with high power density for application in hybrid cars > Martin Kober
Outline
• Motivation Waste Heat Recovery
• Vehicle Measurements and Boundary Conditions
• Procedural method for increasing of power density
• Power Increase
• Weight and Volume Reduction
• Simulation and Measurement Results
www.DLR.de • Chart 2 EMN Orlando > 2016-02-23 > TEG with high power density for application in hybrid cars > Martin Kober
Motivation Waste Heat Recovery Energy flow of Combustion Engines
1) Treffinger P., Häfele Ch., Weiler T. DLR e.V. Stuttgart; Eder A., Richter R., Mazar B. BMW Group München: Energierückgewinnung durch Wandlung von Abwärme in Nutzenergie. 2008 VDI Tagung „Innovative Fahrzeugantriebe“, Dresden
1)
www.DLR.de • Chart 3 EMN Orlando > 2016-02-23 > TEG with high power density for application in hybrid cars > Martin Kober
About 2/3 of the chemical energy is transferred to heat
www.DLR.de • Chart 4
The Evolution of the TEG at the DLR
EMN Orlando > 2016-02-23 > TEG with high power density for application in hybrid cars > Martin Kober
Outline
• Motivation Waste Heat Recovery
• Vehicle Measurements and Boundary Conditions
• Procedural method for increasing of power density
• Power Increase
• Weight and Volume Reduction
• Simulation and Measurement Results
www.DLR.de • Chart 5 EMN Orlando > 2016-02-23 > TEG with high power density for application in hybrid cars > Martin Kober
WLTC – driving cycle Opel Ampera 1.4 l Hybrid (63 kW)
EMN Orlando > 2016-02-23 > TEG with high power density for application in hybrid cars > Martin Kober
0,00E+00
5,00E-03
1,00E-02
1,50E-02
2,00E-02
2,50E-02
3,00E-02
3,50E-02
4,00E-02
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Mas
sens
trom
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s]
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tur [
°C]
Zeit [s]
T_HG [°C] m_p HG [kg/s]1) Oetringer, Kerstin und Kober, Martin (2014) Hat der TEG noch eine Berechtigung in einer Zeit der Elektromobilität? VDI-Fachkonferenz Thermische Rekuperation in Fahrzeugen, 31. März - 01. April 2014, Nürtingen, Deutschland..
Exh
aust
gas
tem
pera
ture
[°C
]
Exh
aust
gas
mas
sflo
w [k
g/s]
www.DLR.de • Chart 6
Choosing a TEG-Design-Point Which Design-Point contains most energy?
EMN Orlando > 2016-02-23 > TEG with high power density for application in hybrid cars > Martin Kober
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Verwertbare Energiemenge im WLTP
emperaturausegungspunkt [°C]
Ene
rgie
men
ge [k
J]
𝐸𝐸 = ��̇�𝑚𝑢𝑢 ⋅ 𝑐𝑐𝑝𝑝 ⋅ (𝑇𝑇𝑢𝑢−𝑇𝑇𝑐𝑐)
Temperaturauslegungspunkt [°C] Temperaturauslegungspunkt [°C]
Design-Point 17g/s 582°C
1) Oetringer, Kerstin und Kober, Martin (2014) Hat der TEG noch eine Berechtigung in einer Zeit der Elektromobilität? VDI-Fachkonferenz Thermische Rekuperation in Fahrzeugen, 31. März - 01. April 2014, Nürtingen, Deutschland..
Ene
rgy
[kJ]
Massflow - Point [g/s]
Potentially useable Energy in WLTC [g/s]
www.DLR.de • Chart 7
Comparison of Different Vehicle Concepts
www.DLR.de • Chart 8
Conventional Vehicle Mild Hybrid Full Hybrid / Rex
max. 2500 kJ
max. 3000 kJ
max. 5000 kJ
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J]
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giem
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[kJ]
EMN Orlando > 2016-02-23 > TEG with high power density for application in hybrid cars > Martin Kober
1) Oetringer, Kerstin und Kober, Martin (2014) Hat der TEG noch eine Berechtigung in einer Zeit der Elektromobilität? VDI-Fachkonferenz Thermische Rekuperation in Fahrzeugen, 31. März - 01. April 2014, Nürtingen, Deutschland..
There is already a heat recovery system in a hybrid car
• Toyota Prius III – Exhaust Heat Recirculation (EHR)
• Coolant passed through the exhaust silencer: standard equipment in the Toyota Prius III - Plug-in Hybrid
• Shortening of warm-up
• More efficient heating of the passengers compartment
EMN Orlando > 2016-02-23 > TEG with high power density for application in hybrid cars > Martin Kober
Demonstration model: Prius III – Exhaust Heat Recirculation (without thermoelectricity) Reference: www.priuswiki.de - Exhaust Heat Recovery
1) www.priuswiki.de - Exhaust Heat Recovery
1)
www.DLR.de • Chart 9
Outline
• Motivation Waste Heat Recovery
• Vehicle Measurements and Boundary Conditions
• Procedural method for increasing of power density
• Power Increase
• Weight and Volume Reduction
• Simulation and Measurement Results
www.DLR.de • Chart 10 EMN Orlando > 2016-02-23 > TEG with high power density for application in hybrid cars > Martin Kober
Procedural method for increasing of power density
EMN Orlando > 2016-02-23 > TEG with high power density for application in hybrid cars > Martin Kober
Goal 1: Power Increase + Cost Reduction Solution:
Holistic Thermodynamic Design-Method for TEG
Goal 2: Weight / Volume Reduction + Cost Reduction Solution:
Highly Integrated TEG-Design
www.DLR.de • Chart 11
Outline
• Motivation Waste Heat Recovery
• Vehicle Measurements and Boundary Conditions
• Procedural method for increasing of power density
• Power Increase
• Weight and Volume Reduction
• Simulation and Measurement Results
www.DLR.de • Chart 12 EMN Orlando > 2016-02-23 > TEG with high power density for application in hybrid cars > Martin Kober
www.DLR.de • Chart 13
Electrical TEG power
Cooling load / pump power
Rolling
and acceleration resistance
Back pressure
Cooling of the exhaust gas
System Development Shortening the cold start phase
EMN Orlando > 2016-02-23 > TEG with high power density for application in hybrid cars > Martin Kober
Holistic Design-Method for TEG
EMN Orlando > 2016-02-23 > TEG with high power density for application in hybrid cars > Martin Kober
• Thermodynamic TEG optimization under consideration of all relevant overall vehicle system interactions (1D)
• CFD simulation (3D) in combination with design data e.g. the TEG weight
• Multi-objectiv optimization to find the best design within targets conflicts
www.DLR.de • Chart 14
Outline
• Motivation Waste Heat Recovery
• Vehicle Measurements and Boundary Conditions
• Procedural method for increasing of power density
• Power Increase
• Weight and Volume Reduction
• Simulation and Measurement Results
www.DLR.de • Chart 15 EMN Orlando > 2016-02-23 > TEG with high power density for application in hybrid cars > Martin Kober
Procedural method VDI Guideline 2221
EMN Orlando > 2016-02-23 > TEG with high power density for application in hybrid cars > Martin Kober www.DLR.de • Chart 16
TEG concept development – Principle-solutions
EMN Orlando > 2016-02-23 > TEG with high power density for application in hybrid cars > Martin Kober
1 2 3 4 5 6 7
feed/dissipate exhaust
heat transfer
conduct heat
distribute heat smoothly
dissipate electric energy
conduct heat
feed/dissipate coolant
provide force
distribute contact pressure smoothly
sub-functionssub-solutions
A2 E1 A4 B2 B1 C1 A1 D1 A31) Kober, M. ; Häfele, C. ; Friedrich, H. E. (2012) Methodical Concept Development of Automotive Thermoelectric Generators (TEG) 3. International Conference 'Thermoelecrics goes Automotive', 2012, Berlin, Deutschland.
1)
www.DLR.de • Chart 17
Procedural method VDI Guideline 2221
EMN Orlando > 2016-02-23 > TEG with high power density for application in hybrid cars > Martin Kober www.DLR.de • Chart 18
Preliminary layout of the modular structure as cross-flow heat exchanger
EMN Orlando > 2016-02-23 > TEG with high power density for application in hybrid cars > Martin Kober
Hot gas heat exchanger
Coolant heat exchanger
Thermoelectric module
www.DLR.de • Chart 19
Preliminary layout of the modular structure as cross-flow heat exchanger
EMN Orlando > 2016-02-23 > TEG with high power density for application in hybrid cars > Martin Kober
Hot gas
Hot gas heat exchanger
Coolant heat exchanger
Thermoelectric module
www.DLR.de • Chart 20
Preliminary layout of the modular structure as cross-flow heat exchanger
EMN Orlando > 2016-02-23 > TEG with high power density for application in hybrid cars > Martin Kober
Hot gas Coolant
Hot gas heat exchanger
Coolant heat exchanger
Thermoelectric module
www.DLR.de • Chart 21
Definitive layout Highly integrated TEG-Design including the cross-flow heat exchanger
EMN Orlando > 2016-02-23 > TEG with high power density for application in hybrid cars > Martin Kober
TEG-housing • Protection against external
influences • Protective atmosphere
(protective gas / vacuum)
www.DLR.de • Chart 22
Definitive layout Highly integrated TEG-Design including the cross-flow heat exchanger
EMN Orlando > 2016-02-23 > TEG with high power density for application in hybrid cars > Martin Kober
TEG-housing • Protection against external
influences • Protective atmosphere
(protective gas / vacuum)
Electronics • Function integrated cooling of
the electronics • Electrical conversion inside the
protective atmosphere • Electrical plug at a higher
voltage level Coolant circulation system • Function integrated in the TEG-
housing • highly integrated cross-flow
heat exchanger
www.DLR.de • Chart 23
Definitive layout Highly integrated TEG-Design including the cross-flow heat exchanger
EMN Orlando > 2016-02-23 > TEG with high power density for application in hybrid cars > Martin Kober
Coolant circulation system • Function integrated coolant
redirection • Coolant heat exchanger: 2x
parallel and 2x in series
Coolant guiding made from injection molding plastic • lightness • low cost
www.DLR.de • Chart 24
Outline
• Motivation Waste Heat Recovery
• Vehicle Measurements and Boundary Conditions
• Procedural method for increasing of power density
• Power Increase
• Weight and Volume Reduction
• Simulation and Measurement Results
www.DLR.de • Chart 25 EMN Orlando > 2016-02-23 > TEG with high power density for application in hybrid cars > Martin Kober
Simulative results Characteristics of the optimized TEG TEG: • weight < 8 kg (without bypass) • volume < 3 dm³ (without bypass and diffusers) • el. peak power > 400 W • el. power at Design-Point (low load) > 160 W
Power density TEG: • gravimetric power density > 50 W/kg • volumetric power density > 130 W/dm³
Thermoelectric Module (TEM): • Material class: Skutterudite 1)
• Efficiency: 7,9% @ ΔT=480 K 1)
www.DLR.de • Chart 26 EMN Orlando > 2016-02-23 > TEG with high power density for application in hybrid cars > Martin Kober
1) Kober, Martin und Heber, Lars und Heuer, Jana und Rinderknecht, Frank und König, Jan und Friedrich, Horst E. (2015) RExTEG Neuartiger Thermoelektrischer Generator zur Steigerung der Effizienz von Hybrid- und Range Extender Fahrzeugen
This results represent the actual world highest power density for automotive TEG.
Results of Current Projects Measured Results – Validation of Simulation
• Target value: < 8kg incl. electronics (not implemented in project)
excl. bypass excl. measurement equipment
• Functional prototype: 8,3 kg measurement equipment: - 2,1 kg electronics (assumption): + <1,5 kg achieved weight <7,7 kg
www.DLR.de • Chart 27 EMN Orlando > 2016-02-23 > TEG with high power density for application in hybrid cars > Martin Kober
Measurement results validation of simulation - design-point
EMN Orlando > 2016-02-23 > TEG with high power density for application in hybrid cars > Martin Kober
Comparison of measurement and CFD simulation of the hot side (Th) and cold side (Tc) at the measurement point 1 - design-point
cutting plane in TEG-longitudinal direction
Z X
Y
design-point: measured data show an even better equalization in longitudinal direction adapting the simulation for future projects
tem
pera
ture
[K]
heat exchanger length x [mm]
Measured_Th_surface_hex_substitute_module
www.DLR.de • Chart 28
Measured_Tc_surface_hex_TEM
Measured_Tc_surface_hex_substitute_module Measured_Th_surface_hex_TEM
Simulated_Th_surface_hex_TEM Simulated_Tc_surface_hex_TEM
Measurement results validation of simulation - max-point
EMN Orlando > 2016-02-23 > TEG with high power density for application in hybrid cars > Martin Kober
Comparison of measurement and CFD simulation of the hot side (Th) and cold side (Tc) at the measurement point 9 - max-point
cutting plane in TEG-longitudinal direction
Z X
Y
max-point: Observations show a good agreement with the results of simulation te
mpe
ratu
re [K
]
heat exchanger length x [mm]
www.DLR.de • Chart 29
Measured_Th_surface_hex_substitute_module
Measured_Tc_surface_hex_TEM
Measured_Tc_surface_hex_substitute_module Measured_Th_surface_hex_TEM
Simulated_Th_surface_hex_TEM Simulated_Tc_surface_hex_TEM
Impressions
EMN Orlando > 2016-02-23 > TEG with high power density for application in hybrid cars > Martin Kober www.DLR.de • Chart 30
Summary
• Procedure to increase the power density
• Presentation of a new holistic design method
• Presentation of
highly integrated
TEG-construction
• Comparison of
measurement and
simulation results
EMN Orlando > 2016-02-23 > TEG with high power density for application in hybrid cars > Martin Kober www.DLR.de • Chart 31
Institute of Vehicle Concepts Pfaffenwaldring 38-40 70569 Stuttgart Martin Kober Tel.: +49 - 711 6862 - 457 [email protected] www.DLR.de/fk
Projekt RExTEG
www.DLR.de • Chart 32 EMN Orlando > 2016-02-23 > TEG with high power density for application in hybrid cars > Martin Kober
Acknowledgement This work is supported by the Ministry of Finance and Economics of
Baden-Württemberg by funds of the Baden-Württemberg Stiftung.
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