Wind Loads on Heliostats and Photovoltaic Trackers

Kurzfassung

In a solar tower plant, temperatures up to 700°C are reached by moving mirror systems called "heliostats" tracking the sun and concentrating its radiation to the top of a tower for large scale electricity production and industrial process heating. To enable a breakthrough of this solar energy technology the heliostat costs have to be further reduced. With precise knowledge of the wind loads they can be built lighter and cheaper. The objective of the presented thesis is to close knowledge gaps and to reduce uncertainties regarding the wind loading of heliostats. Some of the main open questions were the following: - How can the wind loads on heliostats be reduced in an economic way? - Which is the optimum aspect ratio of the mirror panel? - At which heliostat feld position do maximum wind loads occur? - Do the wind load coefcients of heliostats depend on the wind speed? - Which turbulence properties have to be matched by wind tunnel tests? - Can the peak wind loads be reduced by shock absorbers? By wind tunnel tests and full scale measurements these questions were addressed. The results are also valid for double axis photovoltaic trackers. With the gained knowledge, new heliostat designs were developed with cost reductions of up to 25%. The theory of extreme value statistics for the determination of the wind load peak values and the correlation between eddy diameters and turbulent energy spectra are explained in the appendix.