Energy Efficiency Improvement in Biomass Cookstoves through Inert Material Integration: Experimental Evaluation Considering Pot Size and Operating Phases

This study follows on from our previous work on the comparative analysis of the thermal performance of improved cookstoves based on pot size. It focuses on the experimental evaluation of the effect of integrating inert materials (granite) into an improved charcoal-fired cookstove. The tests were conducted according to the Water Boiling Test (WBT) protocol in three phases: cold start, hot start, and simmering, using pots of sizes 2 and 3. The parameters analyzed were specific fuel consumption, thermal efficiency, fire intensity, specific boiling time, and water temperature evolution. The results show that the addition of inert materials improves the overall performance of the cookstove. These materials act as heat storage and release agents, which reduces heat loss and optimizes fuel use, particularly during the simmering phase. For pot 2, the results indicate a significant reduction in specific fuel consumption (up to 0.069 kg/L) as well as good efficiency during the simmering phase (≈38%), although boiling times are sometimes longer. For pot size 3, performance is generally superior, with efficiencies reaching over 40% during hot start-up and nearly 48% during simmering, as well as shorter boiling times. The study shows that inert materials play an important role in accumulating and releasing heat, promoting better thermal stability of the firebox and reducing energy losses, particularly during simmering. Pot size 3 exhibits the shortest overall boiling times, reflecting a better geometric fit with the firebox. These results confirm that the integration of inert materials is an effective strategy for improving charcoal cooking fires.