Egyptian scientists build PV-powered mini fridge with thermoelectric cooling

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Egyptian researchers have built and analyzed a solar-powered mini refrigerator using thermoelectric units (TUs) for cooling. The thermoelectric coolers (TECs) in this study use the Peltier effect, where electric current flows through p-type and n-type semiconductors in series, cooling one side of the device while heating the opposite side.

“The primary objective of this research is to study the efficiency of a thermoelectric refrigerator under various operational settings,” said the academics. “The goal is to meet the daily needs of residents of remote areas by using renewable energy sources without the need to store energy. Different configurations of Peltier elements, along with different voltages generated by the photovoltaic cells, will be tested to control target temperatures.”

The experimental refrigerator box (RB) consisted of an outer wooden box and an inner stainless-steel box, separated by thermal insulation foam. The default system included four TU, each including a Peltier unit made of n-p junction semiconductors soldered to a copper, aluminum heat sink with fins and a fan. The fan cools the hot side of the TU and maintains optimal operation. The RB measured 8 cm × 8 cm × 8 cm and had a volume of 512 cm3.

The researchers used a power supply to simulate various PV capacities and irradiance levels, applying voltages from 4 V to 14 V to operate one to four thermoelectric units. They placed 0.25 lters of water in the box, measuring its initial and final temperatures every five minutes over a 45-minute experiment.

“Best cooling is obtained by utilizing four Peltier units, 10 V, the initial temperature of 30.9 C, and final temperature of 26.4 C,” the scientists said. “The lowest coefficient of performance (COP) is 11.2%, while the highest COP is 77.3% obtained using one Peltier at 4 V.”

The researchers recreated the experimental model in a MATLAB Simulink simulation, optimizing for COP with one Peltier unit at 4 V and achieving a 71.089% COP, showing strong agreement with their results. Using the MATLAB simulation, they also calculated that for an eight-hour operation in Giza, Egypt, the required irradiance levels would be 149.5 W/m² in summer, 67.5 W/m² in winter, 119.3 W/m² in spring, and 118.3 W/m² in fall. Target temperatures were set to 20°C in summer and spring and 15°C in winter and fall.

They presented their results in “Optimizing COP by RSM and MATLAB model of mini refrigerator based on thermoelectric units driven by solar photovoltaic,” which was recently published in Scientific Reports. The research was conducted by scientists from Egypt’s National Research Centre and Helwan University.

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