Dish Characterisation

In the field of solar concentrator characterisation and performance analysis specific expertise has been developed in using videographic 'flux-mapping' of light distributions in the focal regions of solar concentrators (including troughs and dishes), and in the use of close-range photogrammetry to accurately determine the coordinates of concentrator surfaces. This latter technique allows distortions inherent in reflective surfaces to be quantified to a precision high enough to allow computer based ray-tracing algorithms to be employed to predict the ways that sunlight will reflect off the surfaces and concentrate in the focal region.

• Photogrametric surface measurement:
  This technique uses multiple photographs taken from different positions to deduce the three dimensional shape of a surface such as the mirror in a solar concentrator. Optical targets are placed on concentrator surfaces and a combination of digital photographic and image analysis techniques are used to achieve this aim.

• Ray tracing for focal region flux prediction:
  Knowledge of real reflector surface shape allows raytrace calculations based on an assumed sun shape to be used to predict the distribution of radiation falling on objects such as receivers of various shapes, placed in the focal region.

• Focal region flux measurement:
  Ultimately concentrator performance must be determined by a direct measurement of focal region flux distribution. This is done by placing a watercooled lambertian (ie uniform diffusely reflecting) white target in the focal region. digital images of the target are recorded and calibrated against a radiometer measurement obtained from a single representative point to deduce the overall distribution.