Design and development of efficient multipurpose domestic solar cookers/dryers

A truncated pyramid-type solar cooker is designed, fabricated and tested. The truncated pyramid geometry concentrates the incident light radiations towards the bottom and the glazing glass surface on the top facilitates the trapping of energy inside the cooker. One of the salient features of the proposed design is to completely eradicate the need for tracking the sun during cooking, as tracking of sun does not yield better performance. During testing, the highest plate stagnation temperature, under no-load condition, approached 140 °C and under full-load condition, water temperature inside the cooker reached 98.6 °C in 70 min. Two figures of merit, F1 and F2, were calculated and their values were 0.117° C m2/W and 0.467 °C l, respectively, meeting the standards prescribed by the Bureau of Indian Standards for solar box-type cookers. Minor modifications in design are recommended to achieve higher temperatures and reduce cooking times. The design also allows trays to be retained for use as a household dryer.