ProME3ThE2US - Production Method of Electrical Energy by Enhanced Thermal Electron Emission by the Use of Superior Semiconductors

ProME3ThE2US2 project aims at developing, validating and implementing an innovative solid-state conversion mechanism able to transform concentrated solar radiation into electric energy, at very high efficiency, with a direct conversion obtained by an enhanced electron emission from advanced semiconductor structures. The application of this direct energy conversion is in high-flux concentrating solar systems, which are acquiring constant and increasing interest from the energy market owing to a presently mature optical technology and to advantages in reduced request for active components, in capability to be multi-generative, and in high cost-effectiveness.The energy conversion exploits the high radiation flux density, provided by solar concentrators, by combining an efficient thermionic emission to an enhanced photo-electron emission from a cathode structure, obtained by a tailoring of the physical properties of advanced semiconductors able to work at temperatures up to 1000 °C. The high operating temperatures are also connected to the possibility of exploiting the residual thermal energy into electric energy by thermo-mechanical conversion.ProME3ThE2US2 will develop a "proof of concept" converter working under vacuum conditions, composed of a radiation absorber able to employ the solar infrared (IR) radiation to provide a temperature increase, a semiconductor-material cathode properly deposited on it, and a work-function-matched anode, separated from the cathode by an inter-electrode spacing (tens of micrometers are desirable to reduce space-charge effects). The concept novelty is based on (1) the use of both bandgap energy (photoelectric effect) and over-bandgap energy (thermalization) to generate electrical current; (2) the additional use of sub-bandgap IR radiation, characterized by a spectral energy unable to excite photo-emitters, for augmenting the thermionic emission from the cathode, (3) advanced engineered semiconductors, able to emit electrons at lower temperatures than standard refractory metals, whose emission is significant only at temperatures >1300 °C; (4) the experimentation of a hetero-structured cathode for emission enhancement by an internal field; (5) recovery of exhaust heat from the anode by thermo-mechanical conversion. It is estimated that the proposed technology could achieve a conversion efficiency of 45% or higher if used under high-flux irradiation conditions (about 1000 suns).