How to replace a battery with a thermoelectric generator module
Replacing a battery with a thermoelectric generator (TEG) is possible in certain applications, they are a longer-lasting alternative to batteries and do not run out (as long as a temperature difference is present). They also offer an environmentally-friendly solution, as an alternative to batteries which mostly end up in landfill sites.
The greater the differential (DT) of the hot side less the cold side, the greater the amount of power (Watts) will be produced.
The voltage(V) generated by the TEG is directly proportional to the number of couples (N) and the temperature difference (Delta T) between the top and bottom sides of the TE generator and the Seebeck coefficients of the n and p- type materials. The greater the couple count the greater the resultant voltage produced given everything else being equal.
The standard universal material is bismuth telluride (Bi2Te3), the best efficiency that can be achieved with this material is approximately 5%. But once the material is placed into a constructed module the efficiency drops to 3 to 4% depending on DT because of thermal and electrical impedance.
1. Do you have the temperature difference available to exploit? Our TEG modules work up to a DeltaT of 200oC or 250 oC but low power energy harvesting applications can work from 15oC DeltaT.
2. What is the flow of heat from the hot side to the cold side? If there is a heat difference continually, the device will continue to work but if it is intermittent, the power will be too. You may want to consider energy storage if the device needs to keep running.
3. Consider how you will move the heat away from the cold side, moving liquid is most effective, a heat sink designed for natural convection can also do this.
4. Are you restricted on size? In general, the bigger the surface area available, the more power can be generated. You can add numerous TEG’s to achieve the power required if space permits. The modules can be connected in series or parallel to meet your voltage current requirements.
5. Is the solution cost effective? Consider that a TEG has a 5% efficiency and they typically retail for £20-70 each. Using an MPPT controller will improve the harvested power output and increase the overall efficiency of the system.
European Thermodynamics are a UK thermal management company and specialists in thermal energy harvesting, they have a series of TEG-related projects in various applications: http://www.europeanthermodynamics.com/research/ The company also sells thermoelectric generators with a wide range of performances through RS.