Design aspects of a fixed focus type Scheffler concentrator and its receiver for its utilization in thermal processing units

Abstract

Fixed focus type Scheffler concentrators introduced by Wolfgang Scheffler are popularly used for different low to medium industrial process heat applications. These Scheffler concentrators are available in the standard sizes of 8 m2 and 16 m2. The present paper provides a detailed stepwise procedure for the design of a standing type 16 m2 Scheffler concentrator and its fixed focus receiver, intended to be utilized in a solar thermal processing unit for essential oil distillation at our institute. The dome type receivers of boiler steel grade material, SS-304, are selected for the present application. The diameter of the receiver is estimated based on the analysis of the image formed at the receiver of the Scheffler concentrator. The crossbar equations, seasonal parabola calculations and aperture area calculations for the Scheffler concentrator have also been presented in the paper. The geometrical concentration ratio for the Scheffler reflector dish and receiver system are also evaluated for any given day of the year. The design procedure presented in the paper can be used for designing any suitable size Scheffler concentrator and its receiver as per the energy requirement of the application.