thermoelectric generators (teg) with high power … - kober - v1...thermoelectric generators (teg)...

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

http://emnmeeting.org/TM2016/

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)


About 2/3 of the chemical energy is transferred to heat


The Evolution of the TEG at the DLR


Outline




• Power Increase




WLTC – driving cycle Opel Ampera 1.4 l Hybrid (63 kW)


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

0

100

200

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0 200 400 600 800 1000 1200 1400 1600 1800

Mas

sens

trom

[kg/

s]

Tem

pera

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]


Choosing a TEG-Design-Point Which Design-Point contains most energy?


200400

600800 0 5 10 15 20 25 30 35 40

0

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Massenstromauslegungspunkt [g/s]

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]


Comparison of Different Vehicle Concepts


Conventional Vehicle Mild Hybrid Full Hybrid / Rex

max. 2500 kJ

max. 3000 kJ

max. 5000 kJ

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emperaturausegungspunkt [°C]

Ene

rgie

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ge [k

J]

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600800 0 5 10 15 20 25 30 35 40

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mperaturauslegungspunkt [°C]

Ener

giem

enge

[kJ]

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600800 0 5 10 15 20 25 30 35 40

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mperaturauslegungspunkt [°C]

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giem

enge

[kJ]


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


Demonstration model: Prius III – Exhaust Heat Recirculation (without thermoelectricity) Reference: www.priuswiki.de - Exhaust Heat Recovery

1) www.priuswiki.de - Exhaust Heat Recovery

1)


http://www.priuswiki.de/index.php?title=Datei:EHR_1.jpg

Outline




• Power Increase




Procedural method for increasing of power density


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


Outline




• Power Increase





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


Holistic Design-Method for TEG


• 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


Outline




• Power Increase




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


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)


Procedural method VDI Guideline 2221


Preliminary layout of the modular structure as cross-flow heat exchanger


Hot gas heat exchanger

Coolant heat exchanger

Thermoelectric module




Hot gas







Hot gas Coolant





Definitive layout Highly integrated TEG-Design including the cross-flow heat exchanger


TEG-housing • Protection against external

influences • Protective atmosphere

(protective gas / vacuum)




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




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


Outline




• Power Increase




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)


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


Measurement results validation of simulation - design-point


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


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


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]


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


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


Institute of Vehicle Concepts Pfaffenwaldring 38-40 70569 Stuttgart Martin Kober Tel.: +49 - 711 6862 - 457 [email protected] www.DLR.de/fk

Projekt RExTEG


Acknowledgement This work is supported by the Ministry of Finance and Economics of

Baden-Württemberg by funds of the Baden-Württemberg Stiftung.

thermoelectric generators (teg) with high power … - kober - v1...thermoelectric generators (teg)...

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