ProHERMES 2A, a revision to the ProHERMES system, has been installed to measure the flux distribution of the SSPS-CRS solar power tower. The non-cooled Lambertian target (Fig. 18.9) swings in front of the receiver and intercepts the reflected concentrating beam as close to the receiver as possible in the so-called ‘measurement plane’. A camera with a high resolution CCD sensor records the flux distribution at an appropriate point of the target passage. As with FATMES, the flux distribution is recorded as a composite image of many flux images taken as the target moves through the concentrated solar radiation. The overall uncertainty of the system for the total power into the receiver is less than 5%. Two heat flux sensors (Gardon radiometers) are placed very close to the receiver aperture (Fig. 18.9) to be used as heat flux reference by the CCD camera. The transducer of these sensors is a differential thermocouple measuring the temperature difference between the centre and the circumference of a thin circular foil disk.
Measurements have been performed simultaneously with MDF and Pro – HERMES 2A. There is good agreement between the measurements performed with the two systems, with a random deviation of less than 1%. The hybrid system incorporating two independent methodologies gives greater confidence in the measurements, and makes it possible to detect calibration changes.
