Converting waste heat into electricity 

  • This is based on THERMOELECTRIC effect.
  • This effect allows residual heat to be partially converted into electrical energy.
  • Residual heat is a by-product of almost all technological and natural processes, such as in power plants and every household appliance, and the human body as well.


  • Heat released will be small from ordinary metals.
  • This is because metals not only have high electrical conductivity, but high thermal conductivity as well, so that differences in temperature disappear immediately.
  • Thermoelectric materials need to have low thermal conductivity despite their high electrical conductivity. Thermoelectric devices made of inorganic semiconductor materials such as bismuth telluride are already being used today in certain technological applications.


  • A normal HB-grade pencil, they covered over a small area in pencil on ordinary photocopy paper..
  • The pencil traces on the paper deliver a voltage comparable to other far more expensive nanocomposites that are currently used for flexible thermoelectric elements. And this voltage could be increased tenfold by adding some indium selenide to the graphite from the pencil.
  • As a second material, they applied a transparent, conductive co-polymer paint (PEDOT: PSS) onto the surface.
  • These are investigated using SEM and Spectroscopic methods.
  • The results were the pencil deposit left on the paper forms a surface characterised by unordered graphite flakes, some graphene, and clay.
  • While this only slightly reduces the electrical conductivity, heat is transported much less effectively.
  • These simple constituents might be able to be used in the future to print thermoelectric components onto paper that are extremely inexpensive, environmentally friendly, and non-toxic.
  • Such tiny and flexible components could also be used directly on the body and could use body heat to operate small devices or sensors.


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