Université de Pau et des Pays de l'Adour France Laboratoire des …champier.perso.univ-pau.fr/dossiers/cours_thermoelectric... · 2016. 10. 19. · •Recycling •Price and Performance

Daniel CHAMPIER Thermoelectricity 1

Thermoelectricity

Université de Pau et des Pays de l'Adour France

Laboratoire des Sciences de l’Ingénieur Appliquées à la Mécanique

et au Génie Electrique (SIAME)

Laboratoire de thermique énergétique et procédés (LaTEP)

CHAMPIER Daniel


Thermoelectricity

other protagonists: Jean Charles Peltier 1785 – 1845

William Thomson 1824 – 1907 (Lord Kelvin)

General facts 1786 Alessandro Volta discovered thermoelectricity

1821 Thomas Johann Seebeck (1770 – 1831) presented experiments on thermoelectricity but

probably give incorrect explanation

1825 Oersted gave correct explanations of these experiments

Thermoelectricity is direct conversion of temperature differences to electric voltage and vice versa


Thermoelectricity

Seebeck effect : direct conversion of temperature differences to electric voltage

AB

V

T

V

+

T2

T1

A

B

B

A thermocouple made of two Conductors

Thermopower or Seebeck Coefficient : α

The voltage created by this effect is on the order of few to tens of

microvolts per Kelvin difference for metals and up to 1,000V for

semiconductors


Thermoelectricity

Peltier effect : direct conversion of electric current to heat flux When a current passes from one material to another, the energy transported by the electrons is

altered, the difference appearing as heating or cooling at the junction, that is as the Peltier effect.

AB

q

I

+

T2

T1

A

B

B

q

q

I

Peltier Coefficient : π

a source of EMF (Voltage source) is connected across the gap in

conductor B so as to drive a current around the circuit


Thermoelectricity

Kelvin relations AB ABT

ABA B

dT

dt

Other effects involved in thermoelectricity

The Thomson effect: heat absorption (or dissipation) by a material when subjected to temperature

difference and electrical current

I

q

Tc Th

T

Kelvin relations

q I T

The Joule effect

2q RI I

Q


Applications of Thermoelectricity

generate electricity “Seebeck effect”

measure temperature “thermocouple”

cool objects or heat objects “Peltier effect”

• Automotive

• Aircraft, ship

• Aerospace

• Remote Power (pipeline offshore)

• Biomass stoves

• Low power electronic

• Solar thermoelectric


Thermoelectricity

figure of merit

One couple of a seebeck module

2.Z

2. .TZT

Bi2Te3 ZT is about 1

dimensionless figure of merit ZT

σ is the electrical conductivity

λ is the thermal conductivity

ZT is a very convenient figure for comparing

the potential efficiency of devices using

different materials.

Values of ZT=1 are considered good


Thermoelectricity

TE modules individual couples connected electrically in series

Thermally in parrallel to enhance the effect

Semiconductor P and N

≈ 5 cm

≈ 4 mm

≈ 5 cm

Conductive strip


Thermoelectric (TE) Generators TEG

Heat

generator Available

heat

TE modules

Electrical power

(<10%)

Heat

source exchanger exchanger Heat

sink

Electronic converter Storage Battery

convert directly a very small part of the heat moving through them into electricity

2)( TPelec

Waste

Heat

Efficiency

is low


Basic results

These results will be explained in detail later

.

. . .Max 2 2elec

N SW T

8L

Dependence upon the temperature

difference across the thermoelements

Construction :

number of thermoelements

cross-sectional area

length of each element.

‘‘power factor’’ :

type of TE material

max .elec

thermal

W T 1 zT 1TcQ Th 1 zTTh

.2 2

z

efficiency is a function of zT (Dimensionless figure of merit)

( )Th TcT

2

Main goals Augment ZT

Augment T

Materials Research

Thermal Research

(exchangers)


Materials properties

Gao Min (Cardiff university)

Recent

Materials

(10 years)

Bi2Te3 ZT is about 1 the only commercial module available at large scale

Maximum temperature


Advantages of thermoelectric generators

• Direct Energy Conversion

• No Moving Parts

• No Working Fluids

• Maintenance-free Durability

• Noiseless Operation


Classification of generators

• recovery of thermal energy lost: optimization of wasted heat

• production in extreme environment: sources dedicated to TEG

• decentralized power generation: renewable energy sources

• microgeneration: all heat sources are acceptable

• thermoelectric solar: energy source : the sun.


Waste heat

1 quad=2.93 1011kWh=1.055x1018J


Automotive

Thermoelectric technology

for automotive Waste Heat Recovery

Prototypes :

-FIAT

-FORD

-GM

-BMW

- Amerigon

- Renoter (Renault truck Volvo …)


Thermoelectric technology for automotive Waste

Heat Recovery

Opportunity for Waste

Heat Recovery with

Thermoelectrics



Heat Recovery

Sankey diagram for diesel vehicle

light duty trucks

3% efficiency

mean 0.9kW



Heat Recovery

Emission target for passengers cars

130g/km for 2012

drastically reduced to 95g/km for 2020

Emission target for light duty trucks

175g/km for 2014

135g/km for 2020.

Fine and penalties to be paid by car

manufacturers that exceed EU CO2 limits

20€ per exceeding gram starting from 2012

95€ per exceeding gram starting from 2020

New CO2 emission performance standards



Heat Recovery

400-500Wel means 6-7g/km CO2 reduction (Fiat Research Center)

small-medium gasoline engine at motorway driving condition is

characterized by a thermal power, in its exhaust gases, of 10kW at 600°C,

4-5% system conversion efficiency, which can be feasible with ZT=1-1.2

is enough to guarantee 400-500 Wel.

Conversion efficiency from fuel chemical energy to mechanical energy 25-27%

alternator efficiency from mechanical to electrical energy 60%

conversion efficiency from fuel chemical energy to electrical energy 15-16%

Electricity produced by alternator

Electricity produced by TEG


Automotive Requirements for a TE Generator

•Backpressure limit in TEG

•Exchanger must not disturb too much exhaust gases: pressure

drops very low (tens of a few millibars).

•Temperature limit for TE materials (add bypass for exhaust gases

•Durability test requirements

•Assembly requirements

•Control and sensor requirements

•Power conditioning (DC/DC converter)

•Recycling

•Price and Performance

Requirements


Alternator Replacement by a TEG

A TEG must be able to provide necessary power ( about 3kw 220A

14V) to the vehicle under extremely challenging conditions:

• Idle

• City drive cycle (Start-Stop)

• +50°C to -30°C ambient conditions

• Full accessory loads, including current spikes

• Reduce TOTAL fuel consumption, weight, and cost compared to

an alternator/battery system


Ford

Half-Heusler + Bi2Te3segmented TE elements

Anticipated power: ~500 Watts (peak)

TEG on a Ford Fusion with 3.0L V-6 Engine

the exhaust


Ford Packaging for Prototype TEG

TEG

FlexCoupling

Underfloor Catalyst

To Exhaust

To Exhaust


FORD

C. Maranville “ Thermoelectric opportunities for light-duty vehicles.” Ford Motor Company 2012


FORD : TEG performances for a 100km/h cruise

C. Maranville “ Thermoelectric opportunities for light-duty vehicles.” Ford Motor Company 2012

A bypass is necessary to protect the TEG

Anticipated power: ~500 Watts (peak) !!!

Temperature of gas

Welec

105km/h


BMW

2012 Boris Mazar State of the Art Prototype Vehicle with a Thermoelectric Generator

Bi2Te3

Bi2Te3

PbTe


BMW

BMW 535i (US)

Bi2Te3TEG (2007)

High-temperature TEG

Pmax=300W (2009)

2011 Dr. Andreas Eder Efficient and Dynamic –The BMW Group Roadmap for the Application of Thermoelectric Generators


Exhaust Gas Recirculation

reduces NOx emissions by

reducing the combustion

temperature in Diesel

engines.


BMW

The EGR-TEG unit consists of a TEG

section and a conventional cooler section.

conventional

cooler section.

TEG section


AMERIGON BSST (BMW et Ford)

Cylindrical TEG

TEGs were installed in a BMW X6 and a Ford Lincoln MKT with at least

450W of power output achieved in road tests for both vehicles.

D. Crane, “Thermoelectric generator performance for passenger vehicles” 2012


GM

2011Meisner advanced thermoelectric material and generator technology for automotive waste heat at GM.pdf


GM project may 2011

This module could capture waste heat in car's exhaust and convert it to energy, improving fuel economy in a

Chevy Suburban by 3%.

Computer models show the device could generate 350 to 600 watts for city and highway driving, respectively.

General Motors Thermoelectric Generator

Vehicle Selection : Chevy Suburban


Finalize design of prototype TEG

only Bi2Te3 modules by-pass valve set point temperature

for the heat exchanger is about 250°C.


GM : Instrumented TEG and Results

Temperature of the heat exchanger is

250°C for a temperature of exhaust gas

around 400°C


150°C



Temperature variation along the Teg //

to the exhaust gas flow is significant

Front 250° Middle 178° Rear 148°

Temperature variation transverse to

the exhaust gas flow is low < 3°C


Coolant

50°C

1,3 W avec

un HiZ20

209$ !!!!

150°C

11 W avec

un HiZ20




Open circuit voltage are consistent with a 50°C smaller ΔT than

measured between the heat exchanger and the coolant

Computer models show the device could

generate 350 to 600 watts


G. P. Meisner, “Skutterudite thermoelectric generator for automotive waste heat recovery,” in 3rd Thermoelectrics Applications Workshop 2012

GM : future work

Expected Output power 425 Watts !

Improved skutterudite TE materials

Refine TEG design :thermal and electrical interface, bonding …

Electrical power conditioning (avoid impedance mismatch)

First experiment 19W with few modules and small ΔT

extrapolated to 235 Watts in optimum conditions



Renault Trucks, Volvo

Choice of Silicide's

- N-type : Mg2Si

- P-type : MnSi1.77

Advantages disadvantages

Non-toxic materials Moderate ZT

Light density (2-4) Mg2Si type P not

available

Abundant raw materials Current doping of Mg2Si

in project

Support high exhaust

temperature (> 600°C)

P and N have different

mechanical properties

Successful lab. production of the legs for

the project prototype

2012 Luc Aixala RENOTER project presentation


Renault Trucks Joint Company -Volvo Group

•New efficient TEG design allowing screening of any novel materials

•1kW (trucks) and 300W (cars) targets achievable during this year (2011)

•Mass market application in sight but will take time


Aircraft waste heat

recovery Thermoelectric

Applications


Aircraft Thermoelectric Applications

Aircraft engine waste heat harvesting has large potential payoffs

How can Thermoelectric Contribute?

Turboprop

Turboshaft Turbofan

2009 James Huang,Boeing Research & Technology

Fuel Reduction

Preliminary analysis showed that 0.5% or more fuel reduction is achievable

Operating Cost Reduction

Average monthly fuel costs for U.S. commercial planes is $2.415B for the first

4 months of 2009 (Source: EIA)

A 0.5% fuel reduction : $12M monthly operating cost reduction

Advantages Disadvantages

•Provides electrical power from waste heat – no fuel

burn and no moving parts

• Operates over the entire aircraft flight envelope

• Operates independent of engines and does not

affect engine operations

•New technology and unproven

•Cost & efficiency; further development is needed

•Power output limited by available waste heat, space,

device efficiency.

Watt per kilo?

Permitted 0.15 kW/kg

Helicopter conical nozzle

Champier : 0.04kW/kg


Usage of Thermoelectric Generators on Ships

Ship transport generates a large amount of

waste heat

main engine (8-15 MW)

(heavy fuel oil)

auxiliary engines

incinerator

(waste oil : sludge representing 2% of oil

consumption of the main engine)

Workers at heavy cost .

Cold sink between 5°C and 28°C

available (seawater)

no problem with space and weight

Wasted heat used for

heating of heavy fuel oil

•Heating of accommodation areas

•freshwater generation

Work intermittently

Working time : 12h to 20h /day

Steam engine :

Needs a worker at

start and stop : heavy

cost

Thermoelectric

genrator

Kristiansen : incinerator 850kW, calculation : 38kW electric cost 2,7US$/W.


Waste heat recovery : conclusion

Automotive

Alternator + TEG : imminent

Replacement of alternator : challenge

Airplanes

More research is necessary …

ships

Promising


Electricity production in extreme environment

critical applications: a power source extremely reliable over very long periods.

extreme climatic conditions:

• very hot

• very cold

• very wet

• very dry.

Maintenance as low as possible

• helicopter access

•several hour trip

Maintenance does not exist in the case of space expeditions.

operation in a vacuum

vibrations.

insensitive to radiation

The cost of watt is not essential


Space applications

First use of a thermoelectric generator (Pb -Te) : 1961

navigation satellite Transit (1961) of the U.S. Navy.

SNAP-3 (Space Nuclear Auxiliary Power)

Electrical power~2,7 watts

worked for more than fifteen years


Space applications

RTG Radioisotope Thermoelectric Generator

Radioisotope Thermoelectric Generators, or RTGs convert the heat generated by

the decay of plutonium-238 (plutonium dioxyde 238PuO2) fuel into electricity using

devices called thermocouples.

http://solarsystem.nasa.gov/rps/rtg.cfm

GPHS : General Purpose Heat Source module

238Pu fuel pellet


Space applications

T. Caillat et al 23rd rd Symposium on Space Nuclear Power and Propulsion STAIF 2006Jet Propulsion Laboratory/California Institute of Technology


Space applications

T. Caillat et al 23rd rd Symposium on Space Nuclear Power and Propulsion STAIF 2006 Jet Propulsion Laboratory/California Institute of Technology


Space applications


Cassini’ RTG before mounting


Space applications


Curiosity’s Radioisotope Thermoelectric Generator


Space applications

Radioisotope Thermoelectric Generator RTG

Electric Power at beginning

of mission per RTG

Number of RTG

Mission destination year design

lifetime lifetime

Space Nuclear Auxiliary Power SNAP-3 PbTe

2,7 Watts 1 Transit Navigation satellite 1961 15 years

SNAP-19B RTG PbTe-Tags 28.2 Watts 2 Nimbus III meteorological satellite 1969

SNAP-19 RTG PbTe-Tags

42.6 Watts 2 Viking 1 Mars landers 1975 90 days 6 years

2 Viking 2 Mars landers 1975 90 days 4 years

40.3 Watts 4 Pioneer 10 Jupiter, asteroid belt 1972 5 years 30 years

4 Pioneer 11 Jupiter Saturn 1973 5 years 22 years

SNAP-27 RTG PbSnTe

70 Watts Apollo 12, 14,

15, 16 , 17 Lunar Surface

1969-72

2 years 5-8 years

Multi-Hundred Watt (MHW) RTG SiGe

158 Watts 3 Voyager 1 & 2 edge of solar system 1977 still operating over 30 years

General Purpose Heat Source (GPHS) RTG

SiGe 292 Watts

2 Galileo Jupiter 1989 14 years

3 Cassini Saturn 1997 still operating after 14 years

1 Ulysses Jupiter 1990 21 years

1 New Horizons Pluto, Kuiper Belt 2006 still operating after 6 years

Multi-Mission Radioisotope Thermoelectric Generator

MMRTG PbTe-Tags 110 Watts 1 Curiosity

Mars Surface 5 Aug 2012

2011 Expected 14

years


Space applications

Radioisotope Thermoelectric Generator

• compact

• Continuous power sources

• Used in deep space for several decades

• reliable

• Use nuclear fuel relatively easy to manipulate Curium-244

and Plutonium-238

• Materials used: PbSnTe, PbTe, TAGS, SiGe

Conclusion

Current research:

Improved performance of materials: reduced thermal conductivity of the

network

Zintl, skutterudites, couples segmented.


TEG for Remote Power


Remote Power Solutions

REJECTED

HEAT

500 Watts 24 Volts

Natural Gas 48m3/day

Propane 76L/day or 38kg/day

COOLING

FINS

EXHAUST

OUT

LOAD

FUEL IN

T

E

G

F

L

A

M

E

Oil or gas pipelines

Well sites

Offshore platforms

Telecommunications sites

Communications systems

….

Critical application requiring highly reliable power

Low maintenance required

Long life

Extreme climatic conditions (hot, cold, wet, dry)

Remote locations

Propane 38kg/day

Heating Value 50MJ/kg Energy per day= 1900MJ=527kW.h

500 W electric Energy per day= 12 kW.h Efficiency : 2.2 %



500 Watts 24 Volts

Natural Gas 48m3/day

Propane 76L/day or 38kg/day

Pipeline: 550 watts

communications system

Andes Mountains, Chile

Off shore: 200 watts

communications and safety

equipement, multiple systems

- Thailand

Critical application requiring highly reliable power

Low maintenance required

Long life

Extreme climatic conditions (hot, cold, wet, dry)

Remote location Telecommunications:50 watts

helicopter access only,

emergency communications system

- Rocky Mountains, Canada

Pipeline:

5000 watts for SCADA

communications and cathodic

protection of gas pipeline - India

Niche market for TEG



electrical output of a Model 5060 TEG

Maximum Power for an

electrical load between

0.4 and 0.9 ohm


Biomass stoves

Combined Heat and Power (CHP)

Decentralized electricity generation

Developing countries

Biomass primary energy source

(cooking, heating, domestic hot water)

Developed countries

Connection to the network is not always

economically attractive


Thermoelectric power generator for Biomass

Stoves

koolatron

Université de Pau et des Pays de l'Adour

Laboratoire des Sciences de l’Ingénieur Appliquées à la Mécanique

et au Génie Electrique (SIAME)

Laboratoire de thermique énergétique et procédés (LaTEP)

Non Governmental Organisation ‘Planète Bois’ Tarbes France


• Biomass energy is used for basic needs : cooking and heating

• They needs electricity for light, cellular phone and radio

• Biomass is burnt through open fire stoves – low efficiency forest destruction and global warming contribution

– high emissions of air pollutants health damaging

• “Planète Bois” is developing an improved multifunction biomass fired stove. combustion chamber is designed to achieve almost complete combustion of wood

A fan is necessary to increase the air/fuel ratio

Smoke can be extracted with a horizontal pipe avoiding the building of a vertical chimney

• Connecting these households to the power grid cost of building new landlines from US$300 to more than US$4000

cost of distribution of electricity from US$0.07 to US$5.1 per kWh

• thermoelectric generators are cost-effective options for these specific off-grid households.

1.4 billion people

without electricity

in developing countries

Thermoelectric power generator for Biomass

Stoves


Review of thermoelectric generators

for cooking stoves

Author Heat sink (cold side) Type of module * Power per

module

Nuwayhid 2003 Natural air cooling Peltier 1W

Nuwayhid 2005 Natural air cooling Seebeck 4.2W

Nuwayhid 2005 Heat pipes cooling Seebeck 3.4W

Lertsatitthanakorn 2007 Natural air cooling Seebeck 2.4 W

Mastbergen 2007 Forced air cooling (1W) Seebeck + 4W regulated

“BioLite” 2009 Forced air cooling (1W) Seebeck + 2 W

Champier “TEGBioS “ 2009 Water cooling Seebeck 5W

Champier “TEGBioS II“ 2010

Water cooling

Seebeck

9.5W

7.5 W regulated

Rinalde 2010 Forced water cooling (?W) Seebeck 10 W

Bismuth Tellurid (Bi2Te3)

* Peltier :

The temperature difference is limited due to the maximum temperature supported by the solder

The geometry is optimized for cooling and not for power generation.

* Seebeck

The hot side work at a temperature as high as 300°C continuously.

The geometry is optimized for power generation

Heat source : hot gas


“Planète Bois” cook stove

Biomass fired stove

10 kW wood consumption

2.4 kW are used in heating the water 4.5 kW are used in heating the room and inertia

0.9 kW is used for cooking

The idea is to put the TEG in a cogeneration system which

simultaneously provides electric power and heat for the hot water


“Planète Bois” Cook stoves

hot incoming combustion gas

pyrolyzing chamber

water tank 18 liters


SIAME prototype

The advantages of thermoelectric generator are :

It does not need extra energy from the stove.

• It will use the heat flux between the gas and the water tank

• It will only convert a small part into electrical energy.

It is incorporated into the cook stove:

• it requires no electrical link with the outside world, unlike solar panels, or

manipulation of battery.

The maintenance is very light:

• nothing is moving,

• everything is inside the house,

• only the battery needs to be changed at the end of its life.

The generator produces when the stove is on, day and night in good or in rainy

weather (monsoon period) unlike solar panel.

The battery does need to be oversized as each use of the stove recharges the battery

unlike solar system where you need to store energy for the cloudy days.


Laboratory prototype

0 400 800 1200 1600 2000 2400 2800 3200 36000

20%

40%

60%

80%

Eomax

Time (s)

Eo

THot

TCold

THotmax

80%

60%

40%

20%

0

Typical Cycle representative

of one hour combustion

SIAME prototype


Trial of TE generators at SIAME.

Cycle Laboratory

Cycle

one cooking Day 1

2 cookings

Day 2

2 cookings (1 long)

Electrical energy

produced

6.7 Wh

24 kJ

14.1 Wh 28.3 Wh 43.1 Wh

Use’s example* Fan, one phone

charge

2 hours of light

Fan, 2 phone

charges and about

4 hours of light

Fan, 2 phone charges

and 7 hours 20 min of

light

* Phone battery of 3.7V, 1050mAh and light consummation of 4W

Number of systems >5 >100 >1 000

Price (€) 205€ 122€ 72€ Economic

TE generators are cost-effective solutions for off-grid households.


And now?

Today Tomorrow

with TEG

Somewhere

in a village

Our laboratory

this work is supported by


Others prototypes

Study of modules properties TEGbios I TEGbios II

Study of contact resistances Study of heat exchange

with moving gas


thermoelectric generators for cooking stoves

Biolite

USB

2W 5V


Biolite

HomeStove and CampStove

Ghana

Lake Brassua (Maine)

129$


Combined Heat and Power (CHP) with TEG

Automatic Pellet Furnaces, especially Small Scale Combustion Units

Market

East of Europe and North-America

because of unreliable Electric Power Grids

Stove with TEG 400

Max: 8 kWth, 100 Wel

Air cooling

Boiler with TEG 400

Max: 12 kWth, 300 Wel

Water cooling

Outlook BIOENERGY 2020+



Module 8cmx8cm

TEG

Biomass CHP

(pellets)

BIOENERGY 2020+

Location Wieselburg 100km from Vienna !

Decentralized production for decentralized utilization

Production of electricity during periods of high heat demand

and low offer of other renewable energies:

• During winter

• Whilst twilight or night

• During times without sun and wind

Fuel heat output: 10 kW

Nominal electric power: 200 - 400 W

• 8 plates, each with 2 modules

• Positioned around flame

• Heated from inside, cooled from outside



Result Achieved

Useful Heat > 50%

Generator efficiency 3.5%

Electrical efficiency 1,7%

Electrical Power 170 W

Fuel heat : 10 kW

Prototype TEG 250 BIOENERGY 2020+


Autonomous Gas Heaters

2011 M. Codecasa Design and development of a teg cogenerator device integrated in self standing gas heaters

Heater 8kW

Thot 305°C

Tcold 125°C

Power 7.8W


Energy Harvesting for Low Power Electronics

http://www.micropelt.com

Modern wireless sensor modules require only ~100 W -10mW

Micropelt thermogenerator offers a high density of up to 100

thermoelectric leg pairs per mm2

200 C max.

Electrical:

•Thermo-Voltage: uTEG = 0.14 V/K

•Electrical Resistance: RTEG ~ 350

•Thermal Resistance: Rth = 12,5 K/W

Take a small portion of a lost flow of ‘primary’ energy, and convert it into a small flow of USEFUL

electrical energy.

Every technical process produces waste heat

4.2mmx3.3mmx1mm


Micropelt MPG-D751

5mW is enough for most microsensor




http://www.micropelt.com

Emerson WiHART

Differential Pressure Transmitter

ABB Technology Demonstrator

•Self-powered WirelessHART temperature

transmitter

•Fully integrated thermogenerators

•Powered by Micropelt TEG & boost technology

Applications :

Wireless sensors

Data loggers

Direct valve control

Wireless pneumatic control

Use heat from 15 mm pipe

Output power 3.5mw

at 60°C and ambiant 25°C


Solar Thermoelectricity


Solar Thermal to Thermoelectricity

Heat flux through a thermoelectric leg

Solar insulation: ~ 1 000 W/m2

Need to concentrate heat by ~100 times

25 W/m100.001

1001

L

ΔTλ

A

q

11K W.m1λ 0.001mL

100KΔT


Solar Thermoelectrics

Low materials cost and low capital cost, potentially high efficiency.

Key Challenges:

Develop materials with high thermoelectric figure of merit

selective surfaces that absorb solar radiation but do not

re-radiative heat.

Mildred Dresselhaus Massachusetts Institute of Technology

SiGe


Solar Thermoelectrics


Simplified Thermoelectric Equations and properties

Assumptions:

The material properties are temperature independent


Thermoelectric equations (single couple)

It will be assumed that all the heat flow between the source and sink takes place within the thermocouple. Thus, it will be

supposed that thermal radiation and losses by conduction and convection through the surrounding medium are negligible. The

two thermocouple branches in our model have constant cross-sectional areas. Thomson effects will be neglected.

For each branch of the thermoelectric module we have one thermoelectric flow (Seebeck ) and a heat flow (conduction)

p p p p

n n n n

dTI T S

dx(1)

dTI T S

dx

is the thermal conductivity of the material [W. m-1. K-1],

is the Seebeck coefficient of the material [V. K-1]

I is the norm of the electric current [A] which explains the minus sign in front . n

p

n

I

I

Thermal

x 0 L



All the heat flow between the source and sink takes place within the thermocouple.

Thus, thermal radiation and losses by conduction and convection through the surrounding medium are negligible.

It is therefore possible to neglect the temperature variations along the axes y and z.

All this brings us to solve a one-dimensional problem along the x axis

The heat equation can be written in this case

1 T ²T q

a t x²heat generation by Joule effect with

I²q

S²

3

W

m

a = / cp.ρ is the thermal diffusivity

ρ is the specific weight

p

n

I

Thermal

x 0 x+dx

Heat equation in Cartesian Coordinates:

Net transfer of thermal energy into the

control volume (inflow-outflow)

p

T T T Tq c

x x y y z z t

•

Thermal energy

generation

Change in thermal

energy storage

conservation of energy to a differential control volume through which energy transfer is exclusively by conduction.

Cp is the specific heat capacity

control volume : a slice along x

ρ is the electrical resistivity



We also consider the coefficients , ρ and to be constant. This assumption is possible when dealing with small changes and

if we choose an appropriate factor to the situation (that is to say, depending on the temperature range).

We have for each leg:

22p

p p 2p

22n

n n 2n

ITS

Sx2

ITS

Sx

( )

Then we solve the previous equation for each branch

p

n

I

Thermal

x 0 x+dx

The heat equation

1 T ²T q

a t x²with

I²q

S²

To simplify the problem, we will assume the steady state. The left term disappears.

²T q0

x²

²T I²0

x² .S²or



22p

p p 2p

ITS 2

Sx( )

If we solve the previous equation for the branch p

( )

( )

2p

p pp

2p 2

p pp

ITS x B

x S3

IS T x x Bx C

2 S

Boundary conditions: T x 0 Th T x L Tcand

for x = 0 we have :

for x = Lp we have

p pC S Th

2 2p p

p p p p pp

I LS Tc B L S Th

2 S

2p p p p

p p

S Tc Th I LB

L 2 S

p

n

I

Thermal

x x+dx

L 0

Th Tc



If we replace in (3)

p2p

p pp p

p p

LI x

S Tc Th2TS 4 1

x S L( . )

2 nn

n nn n

n n

LI x

S Tc ThT 2S 4 2

x S L( . )

and if we follow the same reasoning for the N-doped leg

2p p p p

p p

S Tc Th I LB

L 2 S p pC S Th

p

n

I

Thermal

x x+dx

L 0

Th Tc

2p

p pp

22n

p pn

ITS x B

x S3

IS T x x Bx C

S

( )

( )



p2p

p pp p

p p

LI x

S Tc Th2TS 4 1

x S L( . )

By combining (1) and (4):

p p p pdT

I T S (1)dx

p2p

p pp p

p p

2p p p p

p pp p

2p p p p

p p pp p

LI x

S Tc Th2I T

S L

I L S Tc Thx 0 I Th

2 S L

I L S Tc Thx L I Tc

2 S L

2 nn

n nn n

n n

2n nn n

n nn n

2n pn n

n p nn n

LI x

S Tc Th2I T

S L

S Tc ThI Lx 0 I Th

2 S L

S Tc ThI Lx L I Tc

2 S L

If we sum and we get the power at the hot side of the system .

Similarly if we sum and we obtain the power at the cold side .

p x 0 n x 0 h

p x L p x L c

p

n

I

Thermal

x x+dx

L 0

Th Tc



2

h

2

c

2elec

r II Th k Th Tc

2

r II Tc k Th Tc

2

W I Th Tc r I

With the electrical resistance of a pair of legs PN.

the overall heat transfer coefficient of a pair of legs PN.

the Seebeck coefficient of the thermocouple PN

p pn n

n p

LLr

S S

p pn n

n p

SSk

L L

p n

p

n

I

Thermal

x x+dx

L 0

Th Tc

2p p p pn n n n

p nhn p n p

2p p p pn n n n

c p nn p n p

2p nelec

L SL SII Th Tc Th

S S 2 L L

L SL SII Tc Tc Th

S S 2 L L

W I Th Tc r I

Simplified Thermoelectric Equations

for a single couple

Welec=h-c


Thermoelectric equations (modules)

Assuming that the cross sections of the legs are the same and considering the leg lengths equal we can write: n pS S n pL L

.

.

.

2

h

2

c

2elec

r IN I Th k Th Tc

2

r IN I Tc k Th Tc

2

W N I Th Tc r I

n p SK N

L

n p LR N

S

Simplified Thermoelectric Equations

for a module

N

Ceramic plate

(electric insulation)

P-Type

Semiconductor

Pellets

conducting strip N-Type

Semiconducto

r Pellets

N

P

N

P

The n-type and p-type thermoelements are electrically connected in serie by a conductor, and thermally in parallel.

The conductor is assumed to have negligible electrical resistance and thermal resistance.

p pn n

n p

LLr

S S

p pn n

n p

SSk

L L

p n

N number of couples (2N legs)

.

.

.

2

h

2

c

2elec

R IN I Th K Th Tc

2

R IN I Tc K Th Tc

2

W N I Th Tc R I

Metal

solders p n n n p p

RL : Load

I


Electrical model of TE module

.Voc N Th Tc

A load resistor RL is connected to the module

n p LR N

S

. . .oc

L L L

N Th TcV N TI

R R R R R R

N

Ceramic plate

(electric insulation)

P-Type

Semiconductor

Pellets

conducting strip N-Type

Semiconducto

r Pellets

N

P

N

P

Metal

solders p n n n p p

RL : Load

I

. 2elecW N I Th Tc R I

The module can be modeled as a voltage source Voc with internal resistance R

R

Voc

TC

TH

RL

TE module

Rheostat

VO

I


Maximizing power output from a generator

.Voc N Th Tc

n p LR N

S

. . .oc

L L L

N Th TcV N TI

R R R R R R

. . .2 2 2 2L

L 2L

RWelec R I N T

R R

By differentiating Welec with respect to RL we can find the value of load resistance that gives the maximum output power.

( ). .2 2 2L

3L L

R RWelecN T 0

R R R

Adapted load RL=R

. . . . . .. . . . . .

. pn

pn

2 2 2 2Max 2 2 2 2 2 2 2elec

n p n p

N T N S N S 2 N S N SW T T T T

2 R 8L 8L 8L4L

n pN LR

S

R

Voc

TC

TH

RL

TE module

Rheostat

VO

I

. 2pnelecW N I Th Tc R I Can also be written :

n ppn 2

pn

pn

p n

p n

21

we can find the the maximum output power.

!



.

. .pn

Max 2 2elec

N SW T

8L

Dependence upon the temperature

difference across the thermoelements

Construction :

number of thermoelements

cross-sectional area

length of each element.

‘‘power factor’’ :

type of TE material

The thermal conductivity, , does not appear and so does not directly impact the maximum power.

thermal resistances connecting the

thermocouples

to the thermal reservoirs

impacts T across

the thermoelement. TE

Generator

R

Voc

TC

TH

RL

TE module

Rheostat

VO

I

First conclusion : L as short as possible! Is it true ?



Metal

solders

n,p pellets

p n n n p p Thermal contact resistances

Electrical contact resistances

. .c c

1 1Voc N Th Tc N T

L L1 1

L L

. pnn p

L LR

2 SS

n p S

kL

Thermal contact resistance

R

Tc

Th

Rc

R c

T pellets

. .pellets

c cc

R 1 1T Th Tc Th Tc Th Tc

R LR 2 R 1 2 1R L

.n p pnL 2 LR N N

S SElectric contact resistance

Re

pn Lecc N

S

: Equivalent length

Lec: Equivalent length

int

. .c

oc

LL

1N T

L1

V LILecR R

R 1 RL

Electric internal resistance

int Re

LecR R 2x c R 1

L

You must take in account the thermal and electrical contact resistance

n ppn 2

Open circuit voltage

Current

pn4S.λ

cLθcRθ cLθ



Metal

solders

n,p pellets

p n n n p p Thermal contact resistance

Electrical contact resistance

. .c c

1 1Voc N Th Tc N T

L L1 1

L L

R

Tc

Th

Rc

R c

T pellets

int

. .oc

cecLL

V N T 1I

LLR R 1R 1 RLL

int

. . . . .. . .. . . . .

. . . . . pn

2 2 2 2 22 2 2pelletsMax 2 2

elec 2 2 2pnc ec c ec c

N T N S TN T 1 1 N S 1W T

4 R 4 R 8 L 8 LL L L L LL1 1 1 1 1 1

Lec L L L L L

.( . .) . )( c c

c

2ec

2 3ec

L 2 L L LF L0

L

L L

L L L L : , , 0max ( ) ( )c c c c2

ec ecc2

c1 1 1 1

L L L 8L L L L 8L L2 2 2 2

Manufacturing Factor

The maximum power for an adapted load can be evaluated again :

. .. . . . . .

.

pn pn

Max 2 2 2 2elec 2

ec c

N S 1 N SW T T F L

8 8L LL 1 1

L L

The maximum power can also be evaluated as a function of the length L :



Metal

solders

n,p pellets

p n n n p p Thermal contact resistance

Electrical contact resistance

R

Tc

Th

Rc

R c

T pellets

.. . .

pn

Max 2 2elec 2

ec c

N S 1W T

8L L L1 1

L L

red: Lec = 0 Lc = 0.

orange: Lec = 0.1 L c = 0.

green: Lec = 0 L c = 0.1

blue: Lec= 0.1 L c = 0.1

yellow: Lec= 0.1 L c = 0.5

There is an optimum for the leg’s length

= max ( )c c c2

ec1 1

L L L 8L L2 2

Manufacturing Factor

The manufacturing factor quantifies the quality of manufacture of

a device. This factor depends mainly on the thermal contacts.

θcmax LL 0Lec θC

pn

cθθ R.

2S.λ

LR 2If then and

Thermal impedance matching !


Maximizing Efficiency

The input energy is the heat energy entering the hot junction

.

2

pnHR I

N I Th K T2

The ouput energy is the electrical energy

. .

L

N TI

R R

. . .2 2 2 2L

L 2L

RR I N T

R RWelec

Efficiency

. .

.

2 2 2L2

L2

Hpn

RN T

R RWelec

R IN I Th K T

2

After some calculation and by defining LRm

R

.( )

.( ).H

2 2

mWelec T m 1

KR m 1 TTh 12Th m 1N Th

by defining

..

. . .

2 2 22 2

pn pn

Nz

K R 4

The efficiency becomes

.( )

.( )

mT m 1

m 1 TTh 1ZTh 2Th m 1

Carnot efficiency

Figure of merit

H

p n n n p p

RL : Load

I Welec

n p n p


Efficiency for different electrical loads

The efficiency

.( )

.( )H

mWelec T m 1


The load must be adapted

0 1 2 3 4 5 6 7 8 9 100

0.01

0.02

0.03

0.04

0.05

0.06

0.07

m

eff

icie

ncy

Efficiency function of the load

Tc=20°

Th=170°C

zT=1

Exemple of efficiency

For ZT=1

Th=170°

T=150 °

There is a maximum for m1.4


Maximizing Efficiency

The efficiency

.( )

.( )H

mWelec T m 1


m can be chosen to maximize the efficiency

( ) ..( )

2

2 2

T 2 2m 2zTh 2 Tz Th z

m Th 2zThm 2zTh 2m 4m 2 Tz

20 2m 2zTh 2 Tz 0m

( )opt

2zTh 2zTc 4 Th Tcm z 1

2 2

optm 1 zT

( )Th Tc

T2

.T 1 zT 1

TcTh 1 zTTh

.2 2

z

efficiency is a function of zT (Dimensionless figure of merit)

( )Th TcT

2

Where T is the average temperature


Maximum Efficiency

m can be chosen to maximize the efficiency optm 1 zT

.T 1 zT 1

TcTh 1 zTTh

where T is the average temperature

0 0.5 1 1.5 2 2.5 3 3.5 40

0.05

0.1

0.15

0.2

0.25

0.3

0.35

zT

eff

icie

ncy

efficiency versus ZT

Tc=20°C

Th=170°C

Carnot efficiency

TE efficiency

0 50 100 150 200 2500

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

0.5

Temperature diffence Th-Tc K

eff

icie

ncy

Efficiency function of temperature difference

ZT=1

ZT=1.5

Carnot efficiency

Tc=20°C

The efficiency becomes


Which values for the material properties ?

Assumptions for the calculations :

The material properties are temperature independent

, ρ, α as function of the temperature for Thermonamics Ingots

The equations remain valid if one chooses the value at the average temperature.

Th Tc

Tav2

= (Tav)

ρ=ρ(Tav)

α =α(Tav)


Finite Element Modeling

Finite Element Software Package : Comsol, Ansys , etc

Final COMSOL mesh FEA model of a thermoelement

junction in COMSOL

The voltage gradient is seen in color

the arrows indicate heat flow

Emil Jose Sandoz-Rosado, Thesis, Improved Modeling of a Thermoelectric Module

The analysis of dozens of thermoelements pairs is highly computationally intensive

The model is limited to a single pair

a FE model can provide several unique advantages. It can solve the governing set of partial differential equations that cannot be solved analytically.

It permits the investigation of complex geometries.

The non-linearities of the material property temperature-dependency can be handled, whereas an analytical solution does not exist.


Thermoelectric equations : other models

2

h

2

c

2elec

r II Th k Th Tc

2

r II Tc k Th Tc

2

W I Th Tc r I

Standard simplified model

2

h

2

c

2elec

r II Th k Th Tc

2

r II T

1Th Th Tc

2

1Tc Th Tc

2

Th Th T

c k Th Tc2

W c Tc I TI hr Tc

2

h

2

c

2elec

r II Th k Th Tc

2

r II Tc k

1Th Tc

Th Tc2

W I Th Tc

2

1Th Tc

r I

2

( )

Tm

TT

Th TcTm

2

Thomson simplified model

Thomson Seebeck simplified model

All parameter evaluated at

Seebeck’ surface coefficients

Introducing Thomson’ coefficient

1996 Chen The influence of Thomson effect on the maximum power output and maximum efficiency of a thermoelectric generator


Global generator You must take in account the heat exchangers, the wafers, the contact resistance etc.

Metal

solders

n,p

pellets p n n n p p

Exchanger

Exchanger

Ceramic wafer

Ceramic wafer

Ths Heat source : hot gas, hot liquid etc.

Heat sink : cold gas, cold liquid etc

Th

Tc

Tcs

Rc

Tcs

Ths

Tc

Th

Rh

Thermoelectric module Welec

h

c

Thermal resistance model of the generator

.

.

.

2

h

2

c

2elec

r IN I Th k Th Tc

2

r IN I Tc k Th Tc

2

W N I Th Tc r I

Thermoelectric equations

h c

h

c

Welec

Ths Th

Rh

Tc Tcs

Rc

Thermal equations

elec

2 2 2

elecelec

elec L

N. (Th Tc)I

R

N (Th Tc)W

R

with R N.R R

Electrical equations

Classical correlations are used to

determine heat transfer coefficients 1

contact ceramic metal HS CSR R R R Rh.A

Convective heat transfer Conductive heat transfer


Global generator

The objective is to determinate Tc and Th

.

.

.

2

h

2

c

2elec

r IN I Th k Th Tc

2

r IN I Tc k Th Tc

2

W N I Th Tc r I

Thermoelectric equations

h c

h

c

Welec

Ths Th

Rh

Tc Tcs

Rc

Thermal equations

2 2 2

elec

N. (Th Tc)I

Relec

N (Th Tc)W

Relec

Electrical equations

2

hr I Ths Th

N I Th k Th Tc2 Rh

.

N. (Th Tc)I

Relecby substituting

2 2 2

3 22

elec elec

N Th Tc Th r Th Tc Ths ThN Nk Th Tc 0

Rh2

( ) ( )

R .R

we get :

(1)

(6)

(3)

(1),(3)

3 2 2 2 3 2 22 2 3 2c c c

c2 2 2elec elecelec el

2h

ech

elec

N r T N T N r TN 1 N r 1 1 ThsN k NK T 0

R 2 Rh R 2 RhR RT

RT

. . .- . - - .

by collecting Th :

(2)

(4)

Doing the same with (2),(4) we get :

. . .. . .

3 2 2 2 2 23 2 3 22c c c

c c2 2 2elec elecelec elec elec

2h h

N r T N T N T1 N r Thc 1 N r TcNk NK T T 0

2 R Rc 2 R RcR R RT T

(5)


Global generator

The determination of Tc and Th, gives the electrical Power

(5)

3 2 2 2 3 2 22 2 3 2c c c

c2 2 2elec elecelec el

2h

ech

elec

N r T N T N r TN 1 N r 1 1 ThsN k NK T 0

R 2 Rh R 2 RhR RT

RT

. . .- . - - .

We must add the constraints

. . .. . .

3 2 2 2 2 23 2 3 22c c c

c c2 2 2elec elecelec elec elec

2h h

N r T N T N T1 N r Thc 1 N r TcNk NK T T 0

2 R Rc 2 R RcR R RT T

(6)

We obtain a system of two quadratic equations with two unknowns

hTThs Tcs

For each equation there is only one solution that comply the constraint.

Each solution is a function of Tc.

The intersection of the two solutions gives the couple of value of Tc and Th.

TcThs Tcs

The problem is complex but can be solved with Newton-type methods


Examples of commercial modules

HiZ

Thermonamic

Komatsu


M a n u f a c t u r e r s

Although a fast rise in commercial applications of TE modules is observed , only few

tens of manufacturers operate in the world market.

Among the manufacturers and suppliers, we can mention the very strong positions of

a few wellknown American companies (HiZ , Melcor and Marlow,for example) who

have been in the market for many years and have maintained leading positions.

Another group consists of the Commonwealth of Independent States (CIS)

companies – mainly Russian and Ukrainian. Most of them are young and started only

a decade ago but are based on a high TE technology level and scientific basis from

the former CIS’s (Commonwealth of Independent States) TE scientific school. Most of

the companies are experienced in high-performance modules. Very difficult to get

information from ALTEC Термоэлектрическая компания !!!!!

Chinese companies are also relatively young. They have demonstrated a fast

expansion in the TE market and dominate in low-cost types. Thermonamic

Production of TE modules is also developing rapidly in Japan and Europe (Komatsu

Eureka).

a report by G Gromov


Example of TE module HiZ 14

• 49 thermocouples

• "Hot Pressed", Bismuth Telluride based high

strength capable of enduring rugged applications

(up to 10 years or longer).

• The bonded metal conductors enable the HZ-14

module to operate continuously at temperatures

as high as 250°C and intermittently as high as

400°C without degrading the module.

www.hi-z.com

For most applications, insulating ceramic wafers must be placed on both sides of the

module

http://www.hi-z.com/





Physical Properties Value Tolerance

Width & Length 6.27 cm 0.01 (0.25)

Thickness

(Special Order) 0.508

0.01 (0.25)

0.002 (0.05)

Weight 82 grams 3 grams

Compressive Yield Stress 10 ksi (70 MPa) minimum

Number of active couples 49 couples ----

Thermal Properties

Design Hot Side Temperature 230 C 10 (20)

Design Cold Side Temperature 30 C 5 (10)

Maximum Continuous Temperature 250 C ----

Minimum Continuous Temperature none ----

Maximum Intermittent Temperature 400 C ----

Thermal Conductivity 2.4 W/m*K +0.001

Heat Flux 9.54 W/sqcm 0.5

Electrical Properties (as a generator)*

Power 13 Watts minimum

Load Voltage 1.65 Volts 0.1

Internal Resistance 0.15 Ohm 0.05

Current 8 Amps 1

Open Circuit Voltage 3.5 Volts 0.3

Efficiency 4.5 % minimum www.hi-z.com






R

Voc

TC

TH

RL

TE module

Rheostat

VO

Electrical Power

0

2

4

6

8

10

12

14

16

0 0,5 1 1,5 2 2,5 3

Po

we

r W

Load ohm

Power versus load

Thot=250°C

Thot=200°C

Thot=150°C

Thot=100°C

Tcold =50°C

www.hi-z.com

Optimal load (adapted)






R

Voc

TC

TH

RL

TE module

Rheostat

VO

Electrical Power

www.hi-z.com

0

2

4

6

8

10

12

14

16

0 0,5 1 1,5 2 2,5 3 3,5

Po

we

r W

Voltage Vo (V)

Power versus voltage

Thot=250°C

Thot=200°C

Thot=150°C

Thot=100°C

Tcold =50°C

Voc/2 Voc

Maximum power


and

adapted voltage






R

Voc

TC

TH

RL

TE module

Rheostat

VO

I

Electrical Power

www.hi-z.com

0

2

4

6

8

10

12

14

16

0 2 4 6 8 10 12 14 16 18

Po

we

r W

Current (A)

Power versus current

Thot=250°C

Thot=200°C

Thot=150°C

Thot=100°C

Tcold =50°C





Thermonamic TEHP1-12656-0.3 Bi-Te

The module can work at the temperature of as high as 330°C heat source continuously and up to 400°C intermittently.

The module is stuck with the high thermal conductivity graphite sheet on its both sides of the ceramic plates to provide low

contact thermal resistance


KOMATSU

[Technical Features]

1. World's top conversion efficiency. Ability to generate a large output even

with a relatively small difference in temperature. (Functional conditions: 280°C

in the high-temperature side and 30°C in the low-temperature side)

2. High output power density at approximately 1W/cm2. Use in compact

equipment.

3. Simplified handling of circuits thanks to the low current of 3A and high

voltage of 8V at the maximum output.

[Specifications]

Size : 50mm x 50mm x 4.2mm (excluding the lead wire)

Weight : 47g

Output : Max. 24W

(when 280°C in the high-temperature side and 30°C in the low-temperature

side)

Temperature range for use : 280°C (max.) and 250°C or lower (normal) in the

high-temperature side and 150°C (max.) in the low-temperature side

Conversion efficiency : Max. 7.2%

Raw material : BiTe family

[Prices ]

283 €


Comparison and prices Producer P/N

Open Voltage

[V]

Internal resistance

[Ω] Power [W] Size[mm]

Price per

module

€ $

Design temperature: Hot side 300 ℃ and cold side 30 ℃. Material : Bi2 Te3 Max. Temp. 380°C

TH

ER

MO

NA

MIC

TEP1-1263-3.4 10,7 5,4 5,2 30x30 28 40

TEP1-1264-1.5 7,8 3 5,1 40x40 28 40

TEP1-12656-0.8 9,5 1,8 13 56x56 63 90

TEP1-12656-0.6 8,4 1,2 14,6 56x56 63 90

TEHP1-12635-1.2 9 2,7 7,5 35x35 28 40

TEHP1-1264-0.8 7,2 1,8 7,1 40x40 63 90

TEHP1-12656-0.3 7,8 0,8 19,2 56x56 63 90

Design temperature: Hot side 230 °C and cold side 30 °C Material: Bi2 Te3 Max. Temp. 250 °C

HI-

Z

TE

CH

NO

L

OG

Y

HZ-2 6,53 4 2,5 29x29 49 69

HZ-9 6,5 1,15 9 62,7x62,7 106 149

HZ-14 3,5 0,15 13 62,7x62,7 98 139

HZ-20 5 0,3 19 75x75 147 209

Design temperature: ΔT=200 °C Material: Bi2 Te3 Max. Temp. 200 °C

EU

RE

CA

Messte

ch

nik

Gm

bH

TEG1-9.1-9.9-0.8/200 5,4 9 0,8 9,1x9,9 76 108

TEG1-30-30-8.5/200 10,8 3,4 8,5 30x30 38 54

TEG1-40-40-19/200 10,8 1,5 19 40x40 56 80

TEG2-40-40-19/200 1 10,6 1,5 19 40x40 37 52

TEG2-50-50-40/200 10,3 0,7 40 50x50 67 95

Design temperature: ΔT=170 °C Material ; Bi2 Te3 Max. Temp. 250 °C

Ma

rlo

w

inc

.

TG 12-4-01L 9,45 6,83 4,05 29,97x34,04 19 28

TG 12-6-01L 9,51 4,56 6,16 40,13x44,70 29 42

TG 12-8-01L 9,43 3,46 7,95 40,13x44,70 36 52

TG 12-2.5-01L 9,56 10,47 2,71 29,97x34,04 31 45

Design temperature: ΔT=200 °C Material : Bi2 Te3 Max. Temp. 250 °C

Cristal Ltd. Type G-127-14-16-L-S ? 2 2,42 40x40 67 40

Design temperature: Hot side 190 °C and cold side 65 °C Material Bi2 Te3 Max. Temp. 200 °C

Watronix INBC1-127.08 HTS not specified not specified 8,5 40x40 20 29

[1] Chinese production: related load output to TEG1-40-40-19/200 but shorter lifetime and higher tolerances, certainly cheaper )

With the exchange rate from 04.04.11: 1 Euro = 1,4179 US-Dollar


Power convertor

DC DC

Converter

The temperature Th and Tc varies a lot.

An electric DC-DC

regulator is necessary

output voltage of the TE

modules fluctuates a lot.

TE modules

Voc=N. (Th-Tc)

R=R(Th,Tc) VTE

ITE

Voc

R

TE Generator

The loads need regulated voltage


Power convertors for TE generators

Power convertors convert electric power from one form to

another

DC – DC

Step-up (Boost) : The storage voltage is higher than the Te modules voltage

Bust-Book : The storage voltage is higher or lower than the Te modules voltage

TE modules are direct current (DC) source

Loads are mostly DC (batteries ) but possibly alternating current AC (grid connection)

DC – AC

Inverter commonly used to supply AC power from DC sources such as solar panels or batteries


Boost convertor

Vin

Iin

Pulse width

Modulation

Vout

Iout

Voc

R

TE Generator DC/DC convertor Battery + Load

Virtual load

Dc duty cycle : fraction of the commutation period T during which the switch is On.

2T

Vin

Vout

Vin-Vout

VL

Inductance voltage

Inductance current=Iin

DcxT 2T

Switch state

Vin

Vout

Vin-Vout

ILmax

ILmin

VL

IL

Inductance voltage

Inductance current=Iin

DcxT

Switch state

on on on off off

time

time

time

on off on off

ILmax

ILmin

T T

Average Iin

Vin

Iin = IL

Vout

Iout

Voc

R

SWITCH ON

VL

Vin

Iin = IL

Vout

Iout

Voc

R

SWITCH OFF

VL


Boost convertor

Vin

Iin

Pulse width

Modulation

Vout

Iout

Voc

R


Virtual load

(1 )in outV V Dc

(1 )

outin

II

Dc

Ideal convertor :

outV is fixed by the battery voltage

The choice of the duty cycle therefore imposes the voltage Vin

and thus the currents

For an adapted load (maximum power) Vin must be equal to Voc/2

in in in out out outP V I V I P

oc inin

V VI

R

Voc of the TE modules fluctuates a lot.

The duty cycle needs to

follow these variations


Maximum Power Point (MPP)

R

Voc

TC

TH

Rv

TE module

Virtual Load

Vin

Iin

Electrical Power

0

2

4

6

8

10

12

14

16

0 0,5 1 1,5 2 2,5 3 3,5

Po

we

r W

Voltage Vo (V)

Power versus voltage

Thot=250°C

Thot=200°C

Thot=150°C

Thot=100°C

Tcold =50°C

Voc/2 Voc

Maximum power point


and

adapted voltage

Exemple of TE module HiZ 14


and

adapted voltage

Voltage Vin (V)

The MMP changes with the temperatures

Intelligence is necessary


Boost convertor with MPPT

Vin

Iin

Pulse width

Modulation

microcontrollor

Vout

Iout

Voc

R


Virtual load

The solution is to control the DC/DC converter with a Maximum Power Point Tracker

Measure Iin

Measure Vin

Calculate Pin

Change duty cycle

Compare with

previous Pin

Vin and Iin change

Question : how to change the duty cycle?


Boost convertor with MPPT

Measure Vin,Iin

Go to the max

Change Dc

Calculate ΔV, ΔP

Example of algorithm “Perturb and Observe”

power transferred to the load


Temperature measurements


Temperature

The temperature is a particular quantity

We can define equality but we can not define the sum of two

temperatures

10kg+5kg=15kg

10° + 20° = ?

Common unit:

degree Celsius, symbol ° C

0 ° C Freezing, 100 ° C boiling water

absolute temperatures:

The kelvin, symbol K

Triple point of water is 273.16 K

Matching :

t (°C)+To= T(K) with To= 273,15 K.


ITS (International Temperature Scale) T90

17 reference points of temperature

Substance and its state Defining point T90 K T90 °C

Triple point of hydrogen 13.8033 -259.3467

Triple point of neon 24.5561 -248.5939

Triple point of oxygen 54.3584 -218.7916

Triple point of argon 83.8058 -189.3442

Triple point of mercury 234.3156 -38.8344

Triple point of water 273.16 0.01

Melting point of gallium 302.9146 29.7646

Freezing point of indium 429.7485 156.5985

Freezing point of tin 505.078 231.928

Freezing point of zinc 692.677 419.527

Freezing point of aluminum 933.473 660.323

Freezing point of silver 1234.93 961.78

Freezing point of gold 1337.33 1064.18

Freezing point of copper 1357.77 1084.62


Thermocouples

VAB is function of:

- Nature of the two

metals

- Temperatures T1 and

T2

It consists of two dissimilar metals, joined together.

When the junction of the two metals is heated or cooled a voltage is produced

that can be correlated back to the temperature.

Thermocouple : a sensor for measuring temperature

T1 sensor junction

T2 reference junction

Table for T2 = 0 and couple A,B EAB(T1)


Thermocouples Type K

http://srdata.nist.gov/its90/main/

Table ITS-90 Thermoelectric Voltage in mV

°C 0 -1 -2 -3 -4 -5 -6 -7 -8 -9 -10

-20 -0.778 -0.816 -0.854 -0.892 -0.930 -0.968 -1.006 -1.043 -1.081 -1.119 -1.156

-10 -0.392 -0.431 -0.470 -0.508 -0.547 -0.586 -0.624 -0.663 -0.701 -0.739 -0.778

0 0.000 -0.039 -0.079 -0.118 -0.157 -0.197 -0.236 -0.275 -0.314 -0.353 -0.392

0 0.000 0.039 0.079 0.119 0.158 0.198 0.238 0.277 0.317 0.357 0.397

10 0.397 0.437 0.477 0.517 0.557 0.597 0.637 0.677 0.718 0.758 0.798

20 0.798 0.838 0.879 0.919 0.960 1.000 1.041 1.081 1.122 1.163 1.203

30 1.203 1.244 1.285 1.326 1.366 1.407 1.448 1.489 1.530 1.571 1.612

40 1.612 1.653 1.694 1.735 1.776 1.817 1.858 1.899 1.941 1.982 2.023

50 2.023 2.064 2.106 2.147 2.188 2.230 2.271 2.312 2.354 2.395 2.436

60 2.436 2.478 2.519 2.561 2.602 2.644 2.685 2.727 2.768 2.810 2.851

70 2.851 2.893 2.934 2.976 3.017 3.059 3.100 3.142 3.184 3.225 3.267

80 3.267 3.308 3.350 3.391 3.433 3.474 3.516 3.557 3.599 3.640 3.682

90 3.682 3.723 3.765 3.806 3.848 3.889 3.931 3.972 4.013 4.055 4.096

100 4.096 4.138 4.179 4.220 4.262 4.303 4.344 4.385 4.427 4.468 4.509

110 4.509 4.550 4.591 4.633 4.674 4.715 4.756 4.797 4.838 4.879 4.920



Coefficients of reference equations giving the thermoelectric voltage, E, as a function of

temperature, t90 , for the indicated temperature ranges

Temperature below 0°C E = sum(i = 0 à n) ci*t90i t90 = Temperature (°C) E = Voltage (mV)

Temperature above 0 °C E = sum(i = 0 à n) ci*t90i + a0*e

a1(t

90-a

2)2

Température (°C) -270 à 0 0 à 1372

c0 0 -0.176004136860e-1

c1 0.394501280250e-1 0.389212049750e-1

c2 0.236223735980e-4 0.185587700320e-4

c3 -0.328589067840e-6 -0.994575928740e-7

c4 -0.499048287770e-8 0.318409457190e-9

c5 -0.675090591730e-10 -0.560728448890e-12

c6 -0.574103274280e-12 0.560750590590e-15

c7 -0.310888728940e-14 -0.320207200030e-18

c8 -0.104516093650e-16 0.971511471520e-22

c9 -0.198892668780e-19 -0.121047212750e-25

c10 -0.163226974860e-22

a0 0.1185976

a1 -0.1183432e-3

a2 0.1269686e+3



coefficients of approximate inverse functions giving temperature, t90 , as a function of the

thermoelectric voltage, E, in selected temperature and voltage ranges.

T90 = c0 + c1E + c2E2 + c3E

3 + c4E4 + ... + cnEn

Température (°C) -200 à 0 0 à 500 500 à 1372

Tension (mV) -5.891 à 0.000 0.000 à 20.644 20.644 à 54.886

c0 0 0 -1.318058E+02

c1 2.5173462E+01 2.508355E+01 4.830222E+01

c2 -1.1662878E+00 7.860106E-02 -1.646031E+00

c3 -1.0833638E+00 -2.503131E-01 5.464731E-02

c4 -8.9773540E-01 8.315270E-02 -9.650715E-04

c5 -3.7342377E-01 -1.228034E-02 8.802193E-06

c6 -8.6632643E-02 9.804036E-04 -3.110810E-08

c7 -1.0450598E-02 -4.413030E-05 0

c8 -5.1920577E-04 1.057734E-06 0

c9 0 -1.052755E-08 0

Erreur (°C) -0.02 à 0.04 -0.05 à 0.04 -0.05 à 0.06


Thermocouples

Standard IEC 584.1 (1995) IEC - International Electrotechnical Commission

Letter-designation for

Thermocouples. Alloy

Domaine de la table en

C

K Nickel-chromium alloy(+)/Nickel-aluminium alloy(-) -270 to 1370 C

T Copper(+)/Copper-nickel alloy(-) -270 to 400 C

J Iron(+)/Copper-nickel alloy(-) -210 to 1200 C

N Nickel-chromium-silicon alloy(+)/Nickel-silicon alloy(-) -270 to 1300 C

E Nickel-chromium alloy(+)/Copper-nickel alloy(-) -270 to 1000 C

R Platinum13%Rhodium(+)/Platinum(-) -50 to 1760 C

S Platinum10%Rhodium(+)/Platinum(-) -50 to 1760 C

B Platinum30%Rhodium(+)/Platinum6%Rhodium(-) 0 to 1820 C

G (Not Official Symbol or Standard) Tungsten / Tungsten 26% Rhenium 1000 to 2300 C

C (Not Official Symbol or Standard) Tungsten 5% Rhenium / Tungsten 26% Rhenium 0 to 2300 C

D (Not Official Symbol or Standard) Tungsten 3% Rhenium / Tungsten 25% Rhenium 0 to 2400 C


International Standard

• IEC 60584-1 Thermocouple reference tables - E = f(T) e.m.f.-temperature relationships

• IEC 60584-2 Tolerances

– This standard contains the manufacturing tolerances for both noble and base metal

thermocouples manufactured in accordance with e.m.f.-temperature relationships of Part

1 of the standard.

• IEC 60584-3

Thermocouples - : Extension and compensating cables - Tolerances and identification system


Thermocouples : specifications


Thermocouples : Cold junction

compensation

E(T1)=VAB + E(T2)

Thermocouples measure the temperature difference between two points,

not absolute temperature


industrial thermocouples

VAB

B

A

T1= sensor temperature

Cu

T2= reference temperature

voltmeter


Thermocouples :

Extension Wire

VAB

B

A

T1= 1100°C Cu

T2= 25°C

Voltmeter

Ti= 100°C

Thermocouple grade

wire is wire that is

used to make the

sensing point (or

probe part) of the

thermocouple.

Extension grade wire is only used

to extend a thermocouple signal

from a probe back to the

instrument reading the signal.

The extension grade wire (or

sheath) typically will have a lower

ambient temperature limit in which

the wire may be used

Expensive

Cheap


Thermocouples :

sensitivity

Measurement system with high resolution and

quality

Sensors are very sensitive to electric noises

Thermocouple Type

Seebeck

Coefficient at 25 °C

(µV/°C)

Sensitivity for 0.1°C

(µV)

E 61 6.1

J 52 5.2

K 40 4.0

R 6 0.6

S 6 0.6

T 41 4.1


Thermocouples :

Properties

Advantages

Large measuring range

robust

Many forms

Response time

Cost

Disadvantages

Decalibration (oxidation ...)

Sensitivity to electrical noise


Thermoelectric cooler TEC


thermoelectric cooling and heating

By applying a low voltage DC power to a TE module, heat will be moved through the module from

one side to the other.

One module face, therefore, will be cooled while the opposite face is simultaneously heated.

It is important to note that this phenomenon may be reversed whereby a change in the polarity

(plus and minus) of the applied DC voltage will cause heat to be moved in the opposite direction.

Consequently, a thermoelectric module may be used for both heating and cooling thereby making it

highly suitable for precise temperature control applications

max

Tc1 zTQc Tc ThCOP

We T 1 zT 1Coefficient of performance

21 TcTh Tc ZTc ZT

2 2Maximum temperature difference



http://www.ferrotec.com

Thermoelectric modules offer many advantages including:

− No moving parts

− Small and lightweight

− Maintenance-free

− Acoustically silent and electrically “quiet”

− Heating and cooling with the same module (including temperature cycling)

− Wide operating temperature range

− Highly precise temperature control (to within 0.1°C)

− Operation in any orientation, zero gravity and high G- levels

− Cooling to very low temperatures (-80°C)

advantages

drawbacks

− fall of COP when the temperature difference increases

− high dependence to room temperature



Although thermoelectric (TE) phenomena was discovered more than

150 years ago, thermoelectric devices (TE coolers) have only been

applied commercially during recent decades.

For some time, commercial TECs have been developing in parallel

with two mainstream directions of technical progress :

• electronics and photonics, particularly optoelectronics and laser

techniques

• low power cooling (<500W)


Thermoelectric optoelectronics applications

http://www.tec-microsystems.com

Application of TE solutions :

optoelectronic devices such as diode lasers,

superluminescent diodes (SLD), various photodetectors,

diode pumped solid state lasers (DPSS), charge-coupled

devices (CCDs).

commercially during recent decades

TEC sub-assemblies provide a temperature-controllable,

uniform-temperature, high-emissivity surface used in

calibrating infrared (IR) detector arrays and FLIR systems.

(Infrared Cameras & Thermal Imagers )

Infrared Cameras

Miniature Thermoelectric Coolers for Telecom Applications


Thermoelectric optoelectronics applications

2012 Prospects for improvement in LED performance using thermoelectrics V. Semenyuk and R. Dekhtiaruk

Temperature is a key factor for LED performance

Lifetime, brightness and color stability are greatly

dependent on operation temperature

LED Coolers

Thermoelectrically cooled LED. by courtesy of Thermion Company

20 to 30ºC decrease of junction

temperature


Low power cooling (<500W)

TE Technology AC-027

Air Coolers 1) Select ambiant

2) Select system temperature

3) Read the heat the system can removed

desired system temperature : -10°C

Heat removed : 5 W

12V 4,6 A Fans 0.8A Pe=65W

If more heat to be removed, the desired temperature

could not be reach

desired system temperature : 25°C

Heat removed : 24 W

12V 4,6 A Fans 0.8A Pe=65W

COP = 0.08

COP = 0.37

Exemple : ambiant 25°C


thermoelectric cooler

Aside from a small fan, this electronic fridge has no

moving parts to wear out or break down. It’s not

affected by tilting, jarring or vibration (situations that

cause home fridges to fail). The governing module, no

bigger than a matchbook, actually delivers the cooling

power of a 10 pound block of ice.

The fridge can become a food warmer for a casserole,

burger or baby’s bottle only with the switch !

koolatron

Koolatron 12 Volt Coolers and Warmers

will heat or cool your lunch and beverages.


thermoelectric cooler

A Solid State thermoelectric module acts as a heat pump to

remove heat away from the fridge, utilizing state of the art,

unique heat pipe technology for improved performance.

Heat from the thermoelectric module is absorbed by the heat

pipe, vaporizing the liquid refrigerant and rapidly moving heat

away from the source, allowing for faster temperature drop. Uses

environmentally friendly R134A refrigerant.

This technology has been widely used by the Military, Aerospace

and Computer industries primarily for rapid heat transfer.!

koolatron


Vehicles cooling and heating

Ford group :

Thermoelectric HVAC (Heating,

Ventilation and Air-Conditioning)

Cool localy driver and passenger and

not the whole car

Documents

Université de Pau et des Pays de l'Adour France Laboratoire des …champier.perso.univ-pau.fr/dossiers/cours_thermoelectric... · 2016. 10. 19. · •Recycling •Price and Performance