Evaluation of the Energy and Exergy Performance of a Box-Type Solar Cooker with an External Reflector during Intermittent Cloud Passages

The growing importance of renewable energy and the need for ecological cooking solutions has led to the design and evaluation of various solar devices. This article presents the experimental results and the evaluation of the energy and exergy performance of a solar cooker. The specific objectives aim to determine indicative parameters such as the "First figure of merit F1," the thermal loss coefficient UL, the peak exergy power, and the product of the exergy temperature difference (
T
xo); to compare the theoretical and experimental thermal loss coefficients; and to evaluate the overall energy efficiency of a box-type cooker. This prototype, trapezoidal in shape, is equipped with an external reflector coated with a mirror and interior side panels are also lined with mirrors. The performance of the cooker was evaluated by determining various indicative parameters such as the "First figure of merit F1," the thermal loss coefficient UL, the peak exergy power, the product of the exergy temperature difference (
T
xo), etc. The theoretically calculated thermal loss coefficient is 5.07 W/m²·K, while the one obtained from the exergy curve of thermal losses as a function of temperature difference is 5.76 W/m²·K, showing a discrepancy of 0.69 W/m²·K. This discrepancy can be explained by the differences between theoretical and experimental conditions. All performance indicators were calculated from experimental tests conducted in accordance with international solar cooking standards. The energy efficiency of the cooker was determined to be 27.97%. The results obtained, when compared to those in the literature, indicate that the studied prototype exhibits satisfactory performance.

Thus, this study confirms the effectiveness of the box-type solar cooker, demonstrating performance comparable to, or even superior to, the best devices reported in the literature. These results highlight the importance of this prototype for the development of sustainable and ecological cooking solutions.