introduction to thermoelectric materials and...
TRANSCRIPT
Space probe to the Jupiter From JPL, NASA Radioisotope
Thermoelectric Generator (PbTe)
Introduction to Thermoelectric Materials and Devices
8th Semester of 2012 2012.05.17, Thursday Department of Energy Science Sungkyunkwan University
1 Thermoelectric Phenomena and Conversion Efficiency
2 Thermoelectric Transport Theory I : Electrical Properties
3 Thermoelectric Transport Theory II : Thermal Properties
4 Measurement of Thermoelectric Properties
5 Materials Preparation : Bulk
6 Materials Preparation : Thin Film
7 Thermoelectric System : Current and Future of Module
8 Applications : Power Generation and Heat Cooling
9 Thermoelectric Materials : State-of-the-art
10 Thermoelectric Materials : Intermetallics
11 Thermoelectric Materials : Oxides
12 Thermoelectric Materials : Phonon Glass and Electron Crystal (PGEC) Materials
13 Theory and Modeling in Nanostructured Thermoelectrics
14 High efficiency in Low Dimensional Materials
15 Hybrid Energy Conversion Systems of Thermoelectrics
16 Final Exam
Plan
Snyder, Toberer, Nat. Mater. 2008
Thermoelectric Research : Current and Future of Module
Target : High Conversion Efficiency of Thermoelectric Devices
Module : Accumulation of Elements, Contact Resistance (Welding), Shape Diversity for Micro-Scale (Thin Film)
System : Circumstance Suitability (Generation), Diversity of Mass Conversion System, Hybridization with other renewable energy system
Materials : High Efficiency (High ZT), New Materials and Various Categories (Limitation to Heavy Metal Compounds), Properties for Hybridization (Magnetic Semiconductor for Magnetocaloric) (Low Workfunction for Thermionic)
Thin Film
Cascade Conventional
Solar absorber + TE Custom Cooling Device D. Kraemer et al., Nat. Mater. 20011
Mass production
For the applications the most widely used materials are compounds based on solid solutions of Bi2Te3-Bi2Se3 and Bi2Te3-Sb2Te3
Mass Production is highly required.
The main Bi2Te3 solid solutions properties, namely their strength, plasticity, linear thermal expansion coefficient, electric conductivity, thermal conductivity, and thermoelectric efficiency, characterized by thermoelectric figure of merit, are strongly anisotropic.
Material properties affecting the choice of production method
Ensuring that the materials high efficiency is in combination with good mechanical properties
Material has to have a chemical composition ensuring the Maximal ZT and homogeneous in respect of chemical composition as far as is possible
Cleavage planes have to be oriented along the direction of the intended electric current Free of crystal grain whose cleavage planes are oriented at a large angle in respect of possible impacts and whose size is of the same order of magnitude as the element size
Material embodies structural elements which obstruct the expansion of the element material cleavages resulting in element fracturing across the electric current direction
Conventional Mass Production Methods
1. Czochralski Method
2. Zone Melting Method
3. Pressing and Extrusion
Melting of
growing
materials
Introductio
n of seed
crystal
Beginnin
g of the
growth
Crystal
Pulling Slow
cooling
Application : Waste Heat as an Energy Resource
3R in waste heat Waste heat REDUCTION within the system or equipment Waste heat RECYCLING within the process or the heating system itself Waste heat RECOVERY within the plant or industrial complex
Range of Temperature for Waste Heat from Industrial Heating Processes
Application : Waste Heat as an Energy Resource
Waste heat distribution for the industrial section in Japan
Application : Waste Heat as an Energy Resource
Major components for a thermoelectric power generation system
Typical configuration of incinerator system for municipal solid waste processing
Application : Waste Heat as an Energy Resource
The temperature of the combustion gas changes along the flow in the system. The type of thermoelectric power generation system is classified by its operated temperature level. Thermoelectric system for high temperature range around 1200 K to 1000 K in burner and boiler For middle range thermoelectric system is mainly used in the gas cooling system For low temperature range around less than 473 K.
Application : Waste Heat as an Energy Resource
Four methods for discharging heat from the thermoelectric power generation system • Water jacket cooling • Air-water radiator cooling • Water/air cooling tower • Air-fin/blower cooling
Classification of a thermoelectric power generation system applied for waste heat recovery
I. Direct Heat Exchange
II. Indirect Heat Exchange
1. Wall-embedded type
2. in-line installed type
1. Working medium type
2. Heat pipe type
a. Air or steam (Inorganic working fluid)
b. Organic working fluid
Heat Transfer
Radiation
Forced convection
Thermal conduction
Application : Waste Heat as an Energy Resource
Schematic structure of tested thermoelectric power generation system
Schematic structure of tested thermoelectric power generation module
Application : Waste Heat as an Energy Resource
Conceptual view of air heat exchange type Thermoelectric power generation
Variation of the experimental parameters and power output with time
Technological problems and breakthrough technology
• The enhancement of system efficiency Heat source, Heatsink sides Optimum heat transfer mechanism adapted for heat source Heat flux control and amplifier Cleaning of heat transfer surface Reduction of auxiliary power Considered design of heat transfer Thermoelectric Module side High ZT materials Optimized configuration of thermoelectric elements Reduction of T btw heat transfer surface and TE electrode Reduction of T btw electrode and TE elements Reduction of heat loss
• The enhancement of system reliability Heat source, Heat sides Emergency countermeasure Design redundancy Thermoelectric Module side Bonding btw electrode and TE element Contact mechanism btw electrode and heat transfer surface Diffusion barrier Uniform contact pressure to heat transfer surface
Thermoelectric Application to Vehicles
Schematic structure of thermoelectric stack which is a united system of TE modules and a heat exchanger (a) and a heat balance (b)
Application : Waste Heat as an Energy Resource
BMW 5-series
Application : Waste Heat as an Energy Resource
BMW 5-series
Exhaust Gas Thermoelectric Generators for Vehicles
Radioisotope thermoelectric generator (RTG)
RTG is an electrical generator that obtains its power from radioactive decay. In such a device, the heat released by the decay of a suitable radioactive material is converted into electricity by the Seebeck effect.
Arthur C. Clarke, in the same brief letter where he introduced the communications satellite, suggested that, with respect to spacecraft, "the operating period might be indefinitely prolonged by the use of thermocouples."
Radioisotope thermoelectric generator (RTG)
Heat from the natural decay of about 33 kilograms (72 pounds) of plutonium-238 (in the form of plutonium dioxide) to generate direct current electricity via thermoelectricity
3 RTGs ~880 Watts (in 1997) ~670 Watts (in 2010) 30 Volts DC
A pellet of 238PuO2 to be used in an RTG for either the Cassini or Galileo mission. The initial output is 62 watts. The pellet glows because of the heat generated by the radioactive decay (primarily α). Photo is taken after insulating the pellet under a graphite blanket for several minutes then removing the blanket.
Radioisotope thermoelectric generator (RTG)
Radioisotope thermoelectric generator (RTG)
Issues to be solved from technological viewpoints
1. ZT values and thermal stability of thermoelectric materials to be selected 2. The design of a heat exchanger to extract the large amount of heat from the exhaust gas Performance of thermoelectric materials used.
Thermoelectric Modules : Contact resistance and thermal resistance
Heat transfer from exhaust gas to thermoelectric modules
Issues to be solved from technological viewpoints
Presentation Articles by Group 2
Presentation Articles by Group 2
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Presentation Articles by Group 2
Presentation Articles by Group 2