Model of the cathode region of a plasma photoelectric converter of concentrated solar radiation.

Abstract

A model of the cathode region of a plasma photoelectric converter of concentrated solar radiation in the regime of an open external circuit is considered. Plasma is analyzed in sodium vapor at a pressure of 104 -105 Pa. The necessary optical power is calculated for creating plasma in the state of Local Thermodynamic Equilibrium (LTE), whose temperature is in the range 4000-4500 K. This temperature provides a small internal resistance of the plasma voltage source. A large value of radiative heat conduction coefficient ensures a small temperature drop between the central part and the plasma LTE boundary near the walls of the converter. The model of a Non-LTE zone near the wall of the cathode is analyzed to specify the boundary conditions in the energy balance equation for LTE plasma. The thermal non-equilibrium plasma model resulted in the electron temperature gradient in the Non-LTE zone. The energy losses of electrons in the ionization layer near the cathode are counterbalanced by the thermal conductivity of the electron gas. The specificity of the conditions under consideration consists in the non-local nature of the balance of the electron temperature in the Non-LTE zone.