The CSIRO National Solar Energy Centre in Newcastle is home to a solar tower facility that can deliver over 500 kW of solar energy to a central receiver. The reflector field consists of 170 heliostats, which can concentrate the solar radiation by an average factor of over 1000.
The quality of focus of the mirrors is fundamental to the operation of the system. As such, much work has been carried out to develop methods of assessing heliostat optical performance. Assessment tools described previously include flux measurements, surface measurements obtained by photogrammetry or by hand, and ray trace models of flux from a given surface. This work showed a high degree of correlation between techniques.
This paper describes a development of these tools into a method for quick assessment of heliostat focussing quality. This can be carried out before installation via surface deflection measurements and ray trace, or on-sun via flux measurements. The mirror performance, assessed by fraction of energy captured by a given aperture, is then compared to that of a modelled mirror with a certain slope error distribution. This technique allows heliostat quality to be assessed independent of field location and time of day, and offers a low-cost and immediate means of heliostat quality control. The methods described are also applicable to linear concentrators or dish facets. Results from application of this method to the CSIRO array will be presented.