Solar-radiation receiver apparatus for heating a heat-transfer medium in a solar thermal power plant , comprising - a container with two oppositely situated ends , which comprises an outer wall and an interior space surrounded by the outer wall ; - a feeding device for feeding the heat-transfer medium to the interior space of the container , wherein the feeding device is arranged on one of the ends of the container ; - a discharging device for removing the heat-transfer medium from the container , wherein the removing device is arranged on the same or the oppositely situated end of the container ; and - an aperture opening for admitting solar radiation at one of the ends ; wherein the container has a longitudinal axis which is oriented parallel or at an acute angle less than 90° to the direction of gravitational force (g), wherein the container is rotatable about an axis of rotation in an intended direction of rotation by means of a rotary drive apparatus of the solar-radiation receiver apparatus in such a way that the heat-transfer medium (210 is able to be guided along an inner wall of the container while forming a heat-transfer-medium film , wherein the inner wall of the container has a friction-promoting device , wherein the feeding device has a front wall , which has a feed opening , and a rear wall , which is directed towards the interior space of the container , wherein at least one guiding element extending at least in a radial direction is arranged between front wall and rear wall , characterized in that , along its extent between feed opening and outer wall , the guiding element is formed as curved in a direction counter to the intended direction of rotation . - a container with two oppositely situated ends , which comprises an outer wall and an interior space surrounded by the outer wall ; - a feeding device for feeding the heat-transfer medium to the interior space of the container , wherein the feeding device is arranged on one of the ends of the container ; - a discharging device for removing the heat-transfer medium from the container , wherein the removing device is arranged on the same or the oppositely situated end of the container ; and - an aperture opening for admitting solar radiation at one of the ends ; wherein the container has a longitudinal axis which is oriented parallel or at an acute angle less than 90° to the direction of gravitational force (g), wherein the container is rotatable about an axis of rotation in an intended direction of rotation by means of a rotary drive apparatus of the solar-radiation receiver apparatus in such a way that the heat-transfer medium (210 is able to be guided along an inner wall of the container while forming a heat-transfer-medium film , wherein the inner wall of the container has a friction-promoting device , wherein the feeding device has a front wall , which has a feed opening , and a rear wall , which is directed towards the interior space of the container , wherein at least one guiding element extending at least in a radial direction is arranged between front wall and rear wall , characterized in that , along its extent between feed opening and outer wall , the guiding element is formed as curved in a direction counter to the intended direction of rotation . <EOS>