Thermal Charge Pump (Energy Conversion via Second-Order Quantum Coupling)

One of my primary interests has always been the conversion of low-grade or waste heat, and heat from lightly concentrated solar flux (i.e., temperatures between 100-500 degrees C), since the ability to efficiently recoup or convert such readily available energy at a low capital cost would be most beneficial to society. To that end, my work has involved the study of non-isothermal electron and phonon transport in thick-films, granular bulk layer formation, deep level defect centers and trap formation, and this has led to a newly discovered and patentable thermal charge pump (TCP), which could become the technology of choice for thermal to electrical energy conversion, enabling low temperature heat sources (including solar) to compete successfully against existing thermal electric plants (i.e., natural gas, coal etc.)

I have been investigating the low temperature thermal pumping of electrons via a novel “bulk” semiconductor (thick film) / metal (thick film) TCP structure that exhibits vastly differing characteristics when compared to diffusion-based thermoelectrics or thermionic emission based thermal energy converters. In this TCP structure, charge carriers efficiently remove lattice energy (heat, via phonon-electron interaction) and do not simply transport their gained kinetic energy to a cooler portion of the junction, but rather maintain their energy for removal via energy dissipation in an external load. The cooler electrons then re-enter the TCP structure to be raised to a higher energy level once again.

The action of such a TCP structure suggests that the open-circuit voltage of a “single junction” should then be a direct result of the average electron-volt equivalent heat coupled from the lattice to charge carriers (minus probable collision losses.) My results to date prove this hypothesis:

Mean electron energy (eV) = Lattice Temperature (K) / 11,600;

At a lattice temperature of 200 degrees C, this is 473 degrees K / 11,600 = 0.041 eV; and

The average electron energy is then 0.041 eV x 2 = 0.082 eV and if there is an assymetrical distribution in electron energies (distortion of Fermi energy) and this leads to an even higher average electron energy, one should be able to observe this (i.e., Voc ~= 90 to 100 mV.)

This can be seen in the graphic which shows the open-circuit voltage of the novel thermal charge pump structure as a function of thermal rise time and bulk temperature (vertical axis is 20mV per division, horizontal axis is 20 seconds per division, thermal saturation of the bulk can be seen to occur at 210 degrees C after 200 seconds.) Of note is that Voc is >94mV when the bulk T ~= 210 degrees C, which is in good agreement with the above.

This new thermal energy conversion structure promises increased energy conversion efficiency in comparison to known thermoelectric, thermionic and thermal diode devices, is of low manufacturing cost since it does not employ semiconductor fabrication techniques, can be of a flexible form and shape, and does not require a heat sink for thermal energy removal.