Thermoelectric Generators are known by different names including, solid-state semiconductor devices, Peltier generators, Seebeck devices and more. They are designed to turn waste heat to reusable power and this is achieved via the utilization of a cold sink and a heat source. Thermoelectric generators are the best option for use in remote locations especially places with a reliable heat source and regions that are off the grid.
Key examples of the heat source include exhaust pipes, diesel and gasoline engines, pellet stoves, fireplaces, wood stoves, furnaces, solar concentrations, solar collectors, boilers, rocket mass heaters and many other sources. There is a vast array of heat sources that can be utilized and this is because waste heat is in abundance and can be harvested easily.
How Thermoelectric Generators Work
The main thing to understand about thermoelectric generators are solid-state semiconductors devices. They are designed to convert heat flow and temperature difference to usable DC power source. Another key thing to not is that the semiconductor device use Seebeck effect to generate voltage and the generated voltage drives electric current to produce power.
People often mistake thermoelectric generator for thermoelectric coolers which are also called cooling chips, solid state cooling or Peltier module. However it’s important to note that they are different. Basically thermoelectric cooler does the reverse of what thermoelectric generator does. The application of voltage to thermoelectric cooler causes the production of electric current which then induces the Peltier effect.
The Peltier effect then causes the transfer of heat from the hot to the cold side. Both the thermoelectric generator and the thermoelectric cooler have similar components but their overall design is different.
Thermoelectric generators are used in the production of power while thermoelectric coolers are used for the removal or addition of heat. Common applications of thermoelectric cooling include refrigeration, heating, thermal management, temperature control and cooling.
How Thermoelectric Generator Use Seebeck Effect
Thermocouple make up the building block of thermoelectric generators. They are made up of one n-type and one p-type semiconductor which are connected by a metal strip in series. These semiconductors are also called pellets, thermoelements or dice. The Seebeck effect directly converts heat to a voltage potential and this is as a result of the movement of charge carriers across the semiconductors.
Doped p-type semiconductors feature holes as charge carriers while n-type semiconductors feature electrons as charge carriers. Charge carriers basically cause diffusion from the semiconductor’s hot side and the diffusion causes a buildup of carriers at one end that causes the creation of voltage potential.
Materials Used for Thermoelectric Generators
There are three materials used for thermoelectric generators, and these are Silicon germanium (SiGe), lead telluride (PbTe) and bismuth telluride (Bi2Te3). The material used depends on the features of the cold sink, design of the thermoelectric generator and heat source. Further research is currently underway to fully understand all the materials that can be used for thermoelectric generators.
Advantages of Thermoelectric Generators
Here are some of the key advantages of thermoelectric generators you should know:
Reliability
As mentioned earlier, thermoelectric generators are solid-state devices and they are very reliable because they don’t have parts that can wear and tear. This design approach makes them last for a long time. For instance the Voyager 1 spacecraft thermoelectric generator is over forty year haven travelled more than 10 billion miles without significant repairs and maintenance.
Quiet
Another impressive advantage of thermoelectric generator is that they are designed to be quiet which makes them environmentally friendly.
No Greenhouse Gases
In addition to being quiet thermoelectric generators don’t operate using greenhouse gases. There are many technologies today that use greenhouse gases but this does not include thermoelectric gases.
Different Fuel Sources
There are not restrictions to the sources of fuel used by thermoelectric generators. This is not the case with other energy conversion technologies as they have restrictions in the fuel sources they utilize.
Scalability
Thermoelectric generators have the potential to be designed to output power levels larger than kilowatts and way smaller than microwatts.
Mountable in Diverse Orientation
The operation of thermoelectric generators can be done in any orientation which is not the case with other technologies with orientation that relies on gravity.
Compact Size
Thermoelectric generators offer a great level of design flexibility because can be designed to be very small and compact.
Direct Energy Conversion
As mentioned earlier thermoelectric generators are designed to convert heat energy into electricity. There are many technologies that do not achieve this easily and require intermediary steps for the conversion to be effective. For instance in a turbine heat energy is first converted to mechanical energy before it is converted to electricity. This process causes the loss of heat at each step of the conversion process.
Common Applications of Thermoelectric Generators
Here are some common applications of thermoelectric generators:
- Extreme Environment: Thermoelectric generators are widely applied in cases where power is required in environments with extreme conditions. This is because the lack moving parts which makes them reliable and ideal for application in different places. Examples of these applications include nuclear pacemakers, lighthouses, power generation in Antarctica, mars rovers, spacecraft and Lunar power stations.
- Waste Heat Recovery: Heat is one of the main byproducts of most energy conversion processes. Thermoelectric generators are used in cases that requires heat utilization and recovery from steel foundries, gas flares, hot water pipes, automotive exhaust, candles, and electronics.
- Microgeneration for Sensor and Electronics: This application is classified by a small heat source or large heat source with small temperature difference. The result is milliwatt or microwatt thermoelectric generator power output. Common applications under this category include low power Internet of Things application, body heat powered flashlights, body heat powered wrist watches, body heat powered medical sensors, and wireless sensor networks.
Other categories include solar thermal applications that makes use of solar energy concentrated on the hot side of the thermoelectric generator and at a high temperature. Another application is combined heat and power which covers applications like camping stoves, grills and biomass cooking stoves.