The optical and thermal efficiency of parabolic-trough solar fields depends on the function and the condition of its components, such as concentrator, absorber, and tracking. The department Qualification develops measurement techniques to evaluate the condition of the components in existing power plants.
To optimize the field and localize problems it is necessary to provide a complete overview of the optical properties of a solar field. QFly provides aerial photos which are evaluated by a corresponding software to obtain information about the optical and thermal properties of the solar field.
After intensive development and testing at PSA this system has been successfully applied in collaboration with CSP SERVICS for the first time in a power plant in the spring of 2014.
Aerial photograph of the 50 MW parabolic trough power plant Andasol1. The colored areas illustrate the measurement areas of the different QFly methods which can each be realized sequentially in a day. Source: DLR
QFly consists of three complimentary measurement techniques: The method ‘Classic’ is based on the TARMES principle and allows for a determination of the mirror shape and receiver position with a high spatial resolution. ‘Survey’ provides similar results from a big height (200 m) with lower resolution and additional information about the orientation of the modules. ‘Thermo’ is used to find heat losses – in particular, receivers with defects in the vacuum insulation.
The application of QFly-Survey has shown that in the current state of development about 60 collector loops can be investigated during a single day. The operation of the plant does not have to be interrupted for this. QFly-Survey gives information about possible defects of the mirror shape, module orientation, torsion, or tracking deviations.
Based on the results of QFly-Survey high-resolution analysis with QFly-Classic can be applied precisely and efficiently to study single collectors. These precise measurements give the mirror shape [RMS < 0.1 mrad] of the concentrator and relative to this the position of the receiver tubes and their deviation from the focal line [RMS < 1 mm].
QFly-Thermo is used for an automated GPS-referenced thermal screening of the receivers. Receivers with defects of pipe sections with high heat losses are localized in the solar field.
In addition to the three Qfly-techniques, the department Qualification has developed a transient thermal measurement procedure for quality checks of the receivers in a solar field. While QFly-Thermo is used for screenings, the transient technique allows for a detailed quantification of heat losses of individual receivers.