Heliostat calibration method using attached cameras and artificial targets

Short description

CENER and IK4-TEKNIKER presents a fast and scalable calibration method based on the international patent WO 2017055663.
Each heliostat is rigidly equipped with a very low cost camera which is used to observe targets placed at known locations around the solar field. By automatically detecting the targets positions in the images it is possible to calculate all the heliostat parameters that govern it. Therefore, the calibration can be done independently for each heliostat and facilitates calibrating a large amount of heliostats in parallel.
The method was tested at the Plataforma Solar de Almeria with an in-house CENER/IK4-TEKNIKER heliostat prototype showing an overall tracking error accuracy of about 0.6 mrad.

Publication references:

Burisch, M., Sanchez, M., Olarra, A., & Villasante, C. (2016, May). Heliostat calibration using attached cameras and artificial targets. In AIP Conference Proceedings (Vol. 1734, No. 1, p. 130005). AIP Publishing. http://aip.scitation.org/doi/abs/10.1063/1.4949215
Burisch, M., Gomez, L., Olasolo, D., & Villasante, C. (2017, June). Heliostat kinematic system calibration using uncalibrated cameras. In AIP Conference Proceedings (Vol. 1850, No. 1, p. 030007). AIP Publishing. http://aip.scitation.org/doi/abs/10.1063/1.4984350
Burisch, M., Sanchez, M., Olano, X., Olarra, A., Villasante, C., Olasolo, D., Monterreal, R., Enrique, R., & Fernandez, J. (2018). Sacalable HeliOstat calibration system (SHORT) – How to calibrate your whole heliostat field in a single night. SolarPACES 2017

Main technical features

The entire field can be calibrated in a few hours. In contrast to other calibration methods using cameras attached to heliostats this method does not require the camera to be attached in a specific location or orientation. The targets are distributed throughout or around the heliostat field and can be placed for instance on top of poles and the tower. For good results the targets should be spread out, as to allow each heliostat to capture targets with a significant motion in both azimuth and elevation. The actual type of target used does not matter for the calibration process; however, they should be easily and reliably be detectable. In this regard the targets are preferably remotely controlled artificial light sources of spherical shape.