Experimental assessment of two Scheffler solar cookers with flat secondary reflectors using standard test method

The Scheffler collector is a parabolic solar concentrator with a fixed and deported focal point throughout the year. This study presents the first standardised and quantitative experimental evaluation of two solar cookers based on the Scheffler design. The systems are located in Marseille (France) and Málaga (Spain) and have primary reflectors measuring 8 m 2 and 2.5 m 2 , respectively. In both cases, a simple secondary reflector consisting of a flat mirror was designed and built. Numerous tests were carried out by heating a fixed quantity of water to its boiling point, following unified experimental protocols at both locations. A new normalisation method, based on the standard test method, has been introduced in data processing; it addresses the effects of seasonal variation in the aperture area. The results show that spillage losses account for around a third of the rays reflected by the Scheffler collector. In the best-case scenario, the standardised average cooking powers provided by the 8 m 2 and 2.5 m 2 Scheffler reflectors at the equinox are 2086 W and 725 W, respectively. These values allow boiling enough water to prepare approximately 180 and 56 servings of rice. The change in aperture area induces a seasonal variation in the standardised cooking power of ±20–25% with respect to the equinox.