Recent Concepts in Thermoelectric Power Generation
Dr. Gao Min
Cardiff School of Engineering
Energy Harvesting 2011 IET London, Savoy Place 07 February 2011
Thermoelectric Energy Harvesting
Gao Min ([email protected])
Cardiff Thermoelectric Laboratory School of Engineering, Cardiff University
Dr. Gao Min
Cardiff School of Engineering
Outline •
Characteristics of Thermoelectric Devices
•
Suitability for Energy Harvesting Application?
•
Recent R&D efforts and Opportunities
Dr. Gao Min
Cardiff School of Engineering
Conversion Efficiency of Thermoelectrics 0.4
Tc=300K
ZT=5
Efficiency
0.3
ZT=3 ZT=2
0.2
N
P
ZT=1 0.1
0.0 300
ZT=0.5 400
500
600
700
800
Temperature
900 1000
2 T ZT
- The conversion efficiency is still relatively low compared with conventional (mechanical) heat engines.
- The most efficient materials are semiconductor alloys based on Bi2Te3 (300K), PbTe (550K) and SiGe (1100K).
Dr. Gao Min
Cardiff School of Engineering
T =300 =360 K =380 =400 =420 c h
14
0.06
P/NA
0.05
T=120 K
12
0.04
10 100 K
8
0.03
80 K
6 4
0.02
60 K
0.01
2 0
0
1
2
3
4
Thermoelement length (mm)
5
0.00
1.4
Power output (W)
16
Conversion efficiency
Power-per-unit-area (mW/mm2)
Power Output and Optimization Theory
1.2
Cold side
optimised
1.0 Hot side
0.8
P-type Peltier thermoelement
N-type Peltier thermoelement
0.6 0.4 0.2 0.0
Best commercially available module
0
20
40
60
80
Temperature difference (K)
• Power-per-unit area can be improved (at expense of a slight reduction in conversion efficiency. • 0.1 W/cm2 has been achieved at T=100K, resulting in a cost of £2/W • 10 mW/mm2 (i.e., 1 W/cm2) may be achievable at T=100K.
100
Dr. Gao Min
Cardiff School of Engineering
Is Thermoelectrics Economically Viable? • Waste heat recovery • Low power devices • Symbiotic systems
(Technological push)
Any T Reliable Scalable Noise free Environmental ADVANTAGES
Low efficiency CO2 reduction
(Market pull)
DISADVANTAGES
Dr. Gao Min
Cardiff School of Engineering
Hot Water TEG
Th = 85 oC, Tc = 15 oC P = 80W, h = 3.0% Cardiff University, 1999
Cost-per-kilowatt-hour (0.01£/kW.h)
Thermoelectric Waste Heat Recovery Power-per-unit-area (kW/m2) 60 50 40 30 20 10
15.0 14.0 13.0 11.0 8.0
5.0
1.5
2.0p/kWh
C
CM C F pT 1.0p/kWh
Fuel cost at 0.5p/kWh
Fuel cost is essentially free
0 0.020 0.025 0.030 0.035 0.040 0.045 0.050 0.055 0.060
Conversion efficiency When thermal input is free, the system should be optimized to obtain a large power-per-unit-area (as long as sufficient heat dissipation can be achieved). Theoretically, £0.04/kWh is achievable.
Dr. Gao Min
Cardiff School of Engineering
Demonstrating Fuel Economy Benefit of Exhaust Energy Recovery Sept 2010
March 2011
Combustion
100%
33% Mobility & Accessories
38% Engine 5% Friction & Radiated
System Integration Loughborough
TE Modules Cardiff
Radiator
Diesel or Patrol
TE materials Herriot-Watt
Current status: Pmax < 200W hmax < 5 %
Engine Manifold CAT
TE
Silencer
Desirables: Pmax > 800W hmax > 10 %
World wide activities
24% Coolant
• BMW, BSST, VISTEON, MARLOW, ,,, • GM, GE, VIRGINIA TECH, ORNL, ,,,
33% Exhaust Gas
• NASA-JPL, MICHIGAN, TELLUREX, ,,, • PRATT&WHITNEY, UNITED TECH, .,,,
• SIEMENS, FIAT, BOSCH, IPM,… • CHALMERS, ,KHT, VOLVO… http://www1.eere.energy.gov/vehiclesandfuels/pd fs/deer_2006/session6/2006_deer_fairbanks.pdf
• RENAULT, VOLEO, NEXTER, … • KOMATSU, TOYATO, NISSAN, ,,,
Dr. Gao Min
Cardiff School of Engineering
Energy Harvesting from Body Heat Thermal energy from human body: ~ 6 mW/cm2 Conversion efficiency at T=5K: ~0.3% (not a problem!) Heat dissipation from top case into air
Movement
P ~ 20 mW/cm2
Quartz Watches: ~40 mW (http://www.roachman.com/thermic/)
N P N P N P
Body heat
Thermal insulation
Power storage Thermoelectric and module management Back case
Seiko (45mW), Citzen (14mW)
In order to obtain an operating voltage of 1.5 V, over 2000 pairs of Bi2Te3 thermocouples are required. very costly using conventional module fabrication technology
Dr. Gao Min
Cardiff School of Engineering
Energy Harvesting for Low Power Electronics Recent progress: Modern wireless sensor modules require only ~100 mW Micropelt
Voltage requirement: 3V
Thermal
EnOcean
3V
20 mV
Ultra low power DC/DC converter
http://www.micropelt.com/
Commercial TE modules
http://www.enocean.com/en/energy-harvesting-wireless/
Dr. Gao Min
Cardiff School of Engineering
Symbiotic Use (CHP) of Thermoelectrics for Pre-heating
Hot Fluid Fuel+Air • TE system efficiency increased; • Fuel efficiency increased; • Lean – fuel combustion possible
Conversion efficiency h
0.30
Combustor
h
0.25
P Th Tc 1 ZT 1 QG Th 1 ZT Tc / Th
0.20
Generator efficiency
0.15
System efficiency
0.10
Th 2
Th 2
T h(Th )dTh P McTh1 h (Th )dTh hs h1 QS Mc(Th1 Tc 2 ) Th1 Tc 2
0.05 0.00 0
200
400
600
800
1000
1200
Preheat temperature difference, Tp (=Tu-T0)
Heat production 99% Electricity generation 1% 1kW heat system
10W electric power for pump and controls – autonomous.
Paul van der Sluis Philips Research, Eindhoven
Dr. Gao Min
Cardiff School of Engineering
Thermoelectric Energy Harvesting Opportunities • Vehicle exhaust heat • Geothermal heat Waste Heat Recovery
• Hot water from steel plant • Incinerator • Subsea oil wells • Wireless sensors
Low Power Electronics
• Medical sensors on Smart textile
• Aircraft health & safety monitoring
• Solar water heating system Symbiotic Systems (CHP)
• Central heating system • Biomass stoves • Mosquito trap
Dr. Gao Min
Cardiff School of Engineering
Research Activities at Cardiff Thermoelectric Laboratory Current Research Projects
• Nanostructured energy harvesting thermoelectrics based on MgSi2 (FP7) • Thermoelectric solar water heating systems (Overseas funding) • Demonstrating fuel economy benefit of exhaust recovery (EPSRC) • Self-powered mosquito trap based on thermoelectric harvesting (KTP) • Preparation and characterization of TixO1-x thin films (Overseas funding) • Heavy-fermion/superconductor tunneling refrigerator (EPSRC) • Develop a novel ZT measurement technique (Overseas funding)
Preparation/Measurement Facilities • Crystal growth / Hot-pressing / Mechanical-alloying • Thermal co-evaporator for Bi2Te3 thin films • PPMS for thermoelectric properties (2K-400K) • Infrared Microscope for micro-scale thermal profile • Seebeck-resistivity system (300K-800K) • Laser flash thermal diffusivity system (300K-1000K) • DSC 200 for specific heat (77K-650K, Natzsch) • Hall coefficient system (300K-1000K)
Cardiff School of Engineering
Energy Harvesting 2011 IET London, Savoy Place 07 February 2011
Thermoelectric Energy Harvesting
Gao Min ([email protected])
Cardiff Thermoelectric Laboratory School of Engineering, Cardiff University
Dr. Gao Min
Cardiff School of Engineering
Outline •
Characteristics of Thermoelectric Devices
•
Suitability for Energy Harvesting Application?
•
Recent R&D efforts and Opportunities
Dr. Gao Min
Cardiff School of Engineering
Conversion Efficiency of Thermoelectrics 0.4
Tc=300K
ZT=5
Efficiency
0.3
ZT=3 ZT=2
0.2
N
P
ZT=1 0.1
0.0 300
ZT=0.5 400
500
600
700
800
Temperature
900 1000
2 T ZT
- The conversion efficiency is still relatively low compared with conventional (mechanical) heat engines.
- The most efficient materials are semiconductor alloys based on Bi2Te3 (300K), PbTe (550K) and SiGe (1100K).
Dr. Gao Min
Cardiff School of Engineering
T =300 =360 K =380 =400 =420 c h
14
0.06
P/NA
0.05
T=120 K
12
0.04
10 100 K
8
0.03
80 K
6 4
0.02
60 K
0.01
2 0
0
1
2
3
4
Thermoelement length (mm)
5
0.00
1.4
Power output (W)
16
Conversion efficiency
Power-per-unit-area (mW/mm2)
Power Output and Optimization Theory
1.2
Cold side
optimised
1.0 Hot side
0.8
P-type Peltier thermoelement
N-type Peltier thermoelement
0.6 0.4 0.2 0.0
Best commercially available module
0
20
40
60
80
Temperature difference (K)
• Power-per-unit area can be improved (at expense of a slight reduction in conversion efficiency. • 0.1 W/cm2 has been achieved at T=100K, resulting in a cost of £2/W • 10 mW/mm2 (i.e., 1 W/cm2) may be achievable at T=100K.
100
Dr. Gao Min
Cardiff School of Engineering
Is Thermoelectrics Economically Viable? • Waste heat recovery • Low power devices • Symbiotic systems
(Technological push)
Any T Reliable Scalable Noise free Environmental ADVANTAGES
Low efficiency CO2 reduction
(Market pull)
DISADVANTAGES
Dr. Gao Min
Cardiff School of Engineering
Hot Water TEG
Th = 85 oC, Tc = 15 oC P = 80W, h = 3.0% Cardiff University, 1999
Cost-per-kilowatt-hour (0.01£/kW.h)
Thermoelectric Waste Heat Recovery Power-per-unit-area (kW/m2) 60 50 40 30 20 10
15.0 14.0 13.0 11.0 8.0
5.0
1.5
2.0p/kWh
C
CM C F pT 1.0p/kWh
Fuel cost at 0.5p/kWh
Fuel cost is essentially free
0 0.020 0.025 0.030 0.035 0.040 0.045 0.050 0.055 0.060
Conversion efficiency When thermal input is free, the system should be optimized to obtain a large power-per-unit-area (as long as sufficient heat dissipation can be achieved). Theoretically, £0.04/kWh is achievable.
Dr. Gao Min
Cardiff School of Engineering
Demonstrating Fuel Economy Benefit of Exhaust Energy Recovery Sept 2010
March 2011
Combustion
100%
33% Mobility & Accessories
38% Engine 5% Friction & Radiated
System Integration Loughborough
TE Modules Cardiff
Radiator
Diesel or Patrol
TE materials Herriot-Watt
Current status: Pmax < 200W hmax < 5 %
Engine Manifold CAT
TE
Silencer
Desirables: Pmax > 800W hmax > 10 %
World wide activities
24% Coolant
• BMW, BSST, VISTEON, MARLOW, ,,, • GM, GE, VIRGINIA TECH, ORNL, ,,,
33% Exhaust Gas
• NASA-JPL, MICHIGAN, TELLUREX, ,,, • PRATT&WHITNEY, UNITED TECH, .,,,
• SIEMENS, FIAT, BOSCH, IPM,… • CHALMERS, ,KHT, VOLVO… http://www1.eere.energy.gov/vehiclesandfuels/pd fs/deer_2006/session6/2006_deer_fairbanks.pdf
• RENAULT, VOLEO, NEXTER, … • KOMATSU, TOYATO, NISSAN, ,,,
Dr. Gao Min
Cardiff School of Engineering
Energy Harvesting from Body Heat Thermal energy from human body: ~ 6 mW/cm2 Conversion efficiency at T=5K: ~0.3% (not a problem!) Heat dissipation from top case into air
Movement
P ~ 20 mW/cm2
Quartz Watches: ~40 mW (http://www.roachman.com/thermic/)
N P N P N P
Body heat
Thermal insulation
Power storage Thermoelectric and module management Back case
Seiko (45mW), Citzen (14mW)
In order to obtain an operating voltage of 1.5 V, over 2000 pairs of Bi2Te3 thermocouples are required. very costly using conventional module fabrication technology
Dr. Gao Min
Cardiff School of Engineering
Energy Harvesting for Low Power Electronics Recent progress: Modern wireless sensor modules require only ~100 mW Micropelt
Voltage requirement: 3V
Thermal
EnOcean
3V
20 mV
Ultra low power DC/DC converter
http://www.micropelt.com/
Commercial TE modules
http://www.enocean.com/en/energy-harvesting-wireless/
Dr. Gao Min
Cardiff School of Engineering
Symbiotic Use (CHP) of Thermoelectrics for Pre-heating
Hot Fluid Fuel+Air • TE system efficiency increased; • Fuel efficiency increased; • Lean – fuel combustion possible
Conversion efficiency h
0.30
Combustor
h
0.25
P Th Tc 1 ZT 1 QG Th 1 ZT Tc / Th
0.20
Generator efficiency
0.15
System efficiency
0.10
Th 2
Th 2
T h(Th )dTh P McTh1 h (Th )dTh hs h1 QS Mc(Th1 Tc 2 ) Th1 Tc 2
0.05 0.00 0
200
400
600
800
1000
1200
Preheat temperature difference, Tp (=Tu-T0)
Heat production 99% Electricity generation 1% 1kW heat system
10W electric power for pump and controls – autonomous.
Paul van der Sluis Philips Research, Eindhoven
Dr. Gao Min
Cardiff School of Engineering
Thermoelectric Energy Harvesting Opportunities • Vehicle exhaust heat • Geothermal heat Waste Heat Recovery
• Hot water from steel plant • Incinerator • Subsea oil wells • Wireless sensors
Low Power Electronics
• Medical sensors on Smart textile
• Aircraft health & safety monitoring
• Solar water heating system Symbiotic Systems (CHP)
• Central heating system • Biomass stoves • Mosquito trap
Dr. Gao Min
Cardiff School of Engineering
Research Activities at Cardiff Thermoelectric Laboratory Current Research Projects
• Nanostructured energy harvesting thermoelectrics based on MgSi2 (FP7) • Thermoelectric solar water heating systems (Overseas funding) • Demonstrating fuel economy benefit of exhaust recovery (EPSRC) • Self-powered mosquito trap based on thermoelectric harvesting (KTP) • Preparation and characterization of TixO1-x thin films (Overseas funding) • Heavy-fermion/superconductor tunneling refrigerator (EPSRC) • Develop a novel ZT measurement technique (Overseas funding)
Preparation/Measurement Facilities • Crystal growth / Hot-pressing / Mechanical-alloying • Thermal co-evaporator for Bi2Te3 thin films • PPMS for thermoelectric properties (2K-400K) • Infrared Microscope for micro-scale thermal profile • Seebeck-resistivity system (300K-800K) • Laser flash thermal diffusivity system (300K-1000K) • DSC 200 for specific heat (77K-650K, Natzsch) • Hall coefficient system (300K-1000K)
