Thermoelectric generators, or Seebeck generators, are devices that directly convert heat into electricity through a process called the Seebeck effect or thermoelectric effect. The efficiency of typical thermoelectric generators is around 5 to 8%.
Older devices were somewhat bulky and employed bimetallic junctions, while the more recent devices use semiconductor p-n junctions made of calcium manganese oxide, lead telluride, bismuth telluride or their combination, based on temperature.
Thermoelectric generators feature thermocouples made of high performance crystalline semiconductor material. This material generates voltage across the thermocouples upon the application of heat, thus causing high current to circulate in a closed primary ring.
This device is highly reliable owing to their solid state construction. They are used in various types of assemblies for years in different aerospace/military applications, such as satellites.
Thermo Electrical Generators
Thermoelectric generators consist of thermoelectric modules that are solid-state integrated circuits employing three thermoelectric effects, namely, Peltier, Seebeck and Thomson effects.
However, it is the Seebeck effect that is responsible for generating electrical power, which is created by 'temperature differential' across the module from heating one side and cooling the other side by moving the heat flux away as fast as it moves through.
Theses generators include pairs of n-type and p-type semiconductor materials that form thermocouples. These are electrically connected to form an array of multiple thermocouples known as thermopile which are sandwiched between thin ceramic wafers.
With the application of heat or cold on the device, electricity is generated. Any heat source such as geothermal heat, ocean heat, solar heat and even body heat can be used for creating electricity.
The efficiency of the device that generates heat as a by-product can be increased by recovering the energy lost as heat. The lesser the temperature of the hot side, the greater the amount of power will be produced. The amount of heat flux successfully moving through the module also influences the power output.
Thermoelectric generators using liquid on the cold side perform better than any other cooling method and produce significantly more net additional power. However, bismuth telluride is the standard semiconductor material that can improve the efficiency of thermoelectric generators at low temperatures.
Advantages of Thermo Electrical Generators
The key benefits of thermoelectric generators include the following:
- Reliable source of energy
- Environment-friendly
- Have high scalability, which means they can be applied to heat source of any size
- Lower the production cost
- Recycle wasted heat energy
Limitations of Thermo Electrical Generators
Some of the major drawbacks of thermo electric generators include the following:
- Low energy conversion efficiency rate
- Require relatively constant heat source
- Lack of industry education about thermoelectric generators
- Slow technology progression
- High output resistance
- Adverse thermal characteristics
Applications of Thermo Electrical Generators
Certain applications of thermo electric generators include the following:
- The heat source of the thermoelectric generator serves as a radioactive element for many space probes including the Mars Curiosity rover.
- Solar cells employ only the high frequency part of radiation, and the low frequency heat energy is wasted. Thermoelectric devices integrated with these solar systems can convert the wasted heat energy into useful electricity.
- Waste heat produced from cars and other automobiles, microprocessors and industrial processes can be harvested using thermoelectric generator, thereby increasing the efficiency of the processes/systems.
- It can be used to power outdoor lights, fans, and several instruments like guard alarm systems, radio receivers and TV sets.
- It can also supply energy to greenhouses, trading kiosks, garages, hangars, cottages, country houses, and amenity rooms.
Conclusion
The limited availability of primary energy resources, increasing concern of environmental issues of emissions and the growing global demand for conserving energy continue to accelerate the search for technologies of generating electrical power.
Thermoelectric power generators have now emerged as a promising alternative green technology owing to their potential to directly convert waste-heat energy into electrical power. The application of this alternative green technology in converting waste-heat energy into electrical power can improve the overall efficiencies of energy conversion systems.
Currently, a large amount of waste heat is discharged from industry including power utilities and manufacturing plants. Hence most of the research activities have been directed towards the utilization of industrial waste heat.
Research on thermoelectric generators might be needed to focus on finding suitable thermoelectric materials that can withstand higher temperatures of various industrial heat sources at a feasible cost with good performance.