Scientific African (Sep 2022)
System for powering autonomous solar cookers by batteries
Abstract
In this paper, we propose innovative autonomous solar cookers (hot plates and box ovens) supplied by batteries. The electrical energy is produced by photovoltaic panels (PV) and stored in a battery (24 V, 520 Ah). Hence, the cookers are powered through a Direct Current /Direct Current (DC/DC) boost converter (400 W) composed of three identical cells in parallel. The power switches are controlled by a digital circuit that generates three Pulse Width Modulation (PWM) signals at 20 kHz with an adjustable duty cycle α. The experimental results show that, for electrical power of 375 W and a duty cycle α = 0.7, the average inductor current of each cell is equal to 3.8 A. Moreover, the DC voltages and currents at the input/output terminals of the converter are worth 24 V / 11.5 A, and 75 V / and 5 A, respectively. Under these conditions, the efficiency of the power supply system used in the cookers is of the order of 90% and the temperature of their thermal resistors reaches 700 °C. All the electrical quantities are in accordance with the results obtained through simulation using the Orcad Pspice environment. These innovative cookers including hot plates and box ovens are tested experimentally in different cases: heating one liter of water, cooking food (1 kg of fries), and baking bread. The obtained heating times are about 25 min, 20 min, and 30 min, respectively. Moreover, according to which cooking case, the “consumed” battery capacity is worth 4.2% - 5.52% of the capacity of the fully charged battery. All these results show, on the one hand, the proper operation of the three-cell DC/DC boost converter powered by batteries, and, on the other hand, the feasibility of heating water and cooking food using the autonomous solar cookers proposed in this work.
