This video demonstrates the operation of a thermoelectric element under household single-phase alternating voltage of 220 volts 50 Hz. Voltage regulation is carried out using a laboratory two-kilowatt autotransformer. All work takes place within the limits of fifty to one hundred and twenty-seven volts. Work takes place in a block of petroleum coke, made in the form of a cube, with sides of one hundred by one hundred millimeters, with two, lower and upper, glass, round covers, ten millimeters thick, designed to record the light and thermal data occurring during the thermoelectric reaction. In the corners, in the middle, there are four glass rods with diameters of five millimeters, designed, also, for fixing light data during the operation of the element. In the center, bottom inward, there is an empty glass laboratory thin-walled flask, with a diameter of eighteen millimeters. These glass parts, in the work of the electrothermal reaction, are intended to record the heat-light action occurring in different ranges of the supplied voltage, as an indicator that the concentration of this thermoelectric reaction is directed inward of the interaction of carbon electrodes, the contact of which is carried out by a thermoelectric element, with a total weight of (0.3) grams and static resistance in the range from (5 kΩ) to (300 kΩ). The purpose of this experiment is to practically utilize the useful potential of reactive voltage under critical short circuit conditions. This demonstration is intended to create a possible joint project for the cyclic conversion of known renewable energy sources, in particular, the concentration of light energy, by appropriate photocells, into electrical energy, independent of the area of structures, weather and daily conditions.