Fuel efficiency and performance of traditional and innovative cookstoves

Fuel efficiency and other cookstove performance parameters have been evaluated in an attempt to progress toward more efficient stoves for a particular locale, to develop and test methodologies for analysing cookstove fuel economy, and to gain insights into the performance of woodburning cookstoves in general. In the first part of this study, fuel consumption and efficiency were measured during the preparation of meals in 13 households. It was found that fuel consumption averages 3·6 kg/meal (s=2·1 kg/meal) and that efficiency averages 5·9% (s=2·2%). The use of aluminium rather than clay pots correlates with higher than average efficiencies. The magnitude of the various cooking energy losses was estimted to point out the opportunities for increasing fuel efficiency. While no particular energy loss mechanism dominates, the more significant energy losses are (i) heating of excess air, (ii) heat carried away by the combustion products, (iii) heating of the stove body and floor, (iv) energy contained in the charcoal residue, and (v) cooking water evaporation. Techniques for reducing these energy losses are suggested. Tests comparing the efficiency of traditional cookstoves and cookstoves containing a flue, chimney, and tightly fitting pots (the Hyderabad stove design) were then carried out. The Hyderabad cookstoves did not prove to be more fuel-efficient than the traditional stove when a means for controlling the draft or regulating the heat input rate to the pots is not provided. When the Hyderabad stove is equipped with a damper and recessed pots, a fuel savings of the order of 30% is realized in the laboratory. The innovative Hyderabad stove still requires field testing and user evaluation. This limited series of experiments suggests that new woodburning cookstoves should be carefully designed, constructed and operated.