On the thermal performance of flat and cavity receivers for a parabolic dish concentrator and low/medium temperatures

•The manuscript is focused on efficiency analysis of parabolic dish collector systems, working in a range of low/medium temperatures, which is of great importance in industrial practice.•A comparison of several receivers (flat-plane and cavity) has been performed, based on a detailed modeling of the radiant power losses due to reradiation, convection and conduction losses.•In practice, the flat-plate receiver should be used with some care, since its temperature is very high in the zones of high concentration. An open cavity solves this problem with the biggest reduction of temperature, but has a relatively modest increasing of thermal efficiency. It is found that the cavity receiver with a cover is the most efficient with an increasing up to a 20% with respect to the flat-plate receiver, with a very significative reduction of the cavity temperature.