Brooks, M.J., School of Mechanical Engineering, University of KwaZulu-Natal, South Africa
This paper describes the thermal performance of a novel solar oven that incorporates a compact reflective lens, or ring array, to augment sunlight concentration. Performance is reported in terms of the positive effect of the ring array versus a non-concentrating lid, maximum operating temperature, thermal efficiency, performance under partly cloudy skies, and the effects of incidence angle and tracking. Use of the ring array lens improved thermal efficiency by 4% in the test range up to 100°C, while boosting the maximum operating temperature from 138°C to 196°C. Comparative tests conducted under clear sky conditions against two other commercial types showed that when tracked in the azimuth plane at near-normal incidence angles, the new design generated maximum cooking power of 300 W and boiled water at a rate 13% faster than the next best commercial oven tested. Augmented sunlight concentration sensitised the new design to higher angles of incidence and performance was negatively affected in the non-tracked state. Under non-ideal operating conditions, including partial shading by cloud, the oven outperformed both commercial units.