Patent ID: 8035274

Claim:
A method for converting heat to electric energy, comprising the steps of: (a) providing a ferroelectric layer having a first surface and an opposite, second surface, wherein the ferroelectric layer is comprised of a ferroelectric material characterized with a phase transition temperature such that, when the material is in a ferroelectric phase spontaneous polarization is established in the unit cells of the ferroelectric, and the ferroelectric layer, upon poling, develops an overall net spontaneous polarization, and such that, as the temperature of the ferroelectric changes so that it traverses the transition temperature, the material enters a paraelectric or antiferroelectric phase wherein the ferroelectric layer has negligible or no overall net spontaneous polarization; (b) forming a pair of electrodes respectively on the first surface and the second surface of the ferroelectric layer, wherein the electrodes are formed of a thermally and electrically conductive material; (c) alternately removing and inputting heat from and into the ferroelectric layer by convection, conduction or radiation, so as to alternately cool the ferroelectric layer at a first temperature T L that is lower than the phase transition temperature, and alternately heat the ferroelectric layer at a second temperature T H that is higher than the phase transition temperature, so that the ferroelectric material of the ferroelectric layer thereby undergoes alternating phase transitions between (1) the ferroelectric phase and (2) the paraelectric or antiferroelectric phase; (d) applying a DC voltage and a resulting electric field for poling the ferroelectric layer when the ferroelectric material is in, or entering into, the ferroelectric phase so that screening charges are generated on the pair of electrodes, and an external field not otherwise being applied to the ferroelectric layer; and (e) outputting electric energy corresponding to the generated screening charges on the pair of electrodes when the ferroelectric material of the ferroelectric layer transitions into the paraelectric or antiferroelectric phase.