Investigation of the Effect of Physical and Optical Factors on the Optical Performance of a Parabolic Trough Collector

Predicting the structural and optical performance of concentrating solar power (CSP) collectors is critical to the design and performance of CSP systems. This paper presents a performance analysis which utilizes finite-element models and ray-tracing of a parabolic trough collector. The finite-element models were used to determine the impact of gravity loads on displacements and rotations of the facet surfaces, resulting in slope error distributions across the reflective surfaces. The geometry of the LUZ LS-2 parabolic trough collector was modeled in SolidWorks, and the effects of gravity on the reflective surfaces are analyzed using SolidWorks Simulation. The ideal mirror shape, along with the 90° and 0° positions (with gravity deformation) were evaluated for the LS-2. The ray-tracing programs APEX and ASAP are used to assess the impact of gravity deformations on optical performance. In the first part of the analysis, a comprehensive study is performed for the parabolic trough to evaluate a random slope error threshold (i.e., induced by manufacturing errors and assembly processes) above which additional slope errors caused by gravity sag decrease the intercept factor of the system. The optical performance of the deformed shape of the collector (in both positions) is analyzed with additional induced slope errors ranging from zero up to 1° (17.44 mrad). The intercept factor for different solar incident angles found from ray-tracing is then compared to empirical data to demonstrate if the simulations provide consistent answers with experimental data.

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Measurement Techniques for the Optical Quality Assessment of Parabolic Trough Collector Fields in Commercial Solar Power Plants

ASME 2007 Energy Sustainability Conference ◽

10.1115/es2007-36221 ◽

2007 ◽

Cited By ~ 6

Author(s):

Steffen Ulmer ◽

Klaus Pottler ◽

Eckhard Lu¨pfert ◽

Marc Ro¨ger

Keyword(s):

Manufacturing Process ◽

Power Plants ◽

Solar Power ◽

Optical Quality ◽

Optical Performance ◽

Parabolic Trough ◽

High Optical Quality ◽

Parabolic Trough Collector ◽

Solar Power Plants

The optical quality of the collector field of concentrating solar power plants is an essential factor for their profitability. High optical quality can be achieved and guaranteed when the manufacturing process is continuously monitored and adjusted in its essential steps. A stationary, automatic photogrammetry system has been developed for the shape accuracy control of concentrator structures. It uses a digital camera, automatically moved around the object, computer controlled automatic image evaluation and continuous calibration checks. It is robust and fast enough to be integrated in a solar collector production line. For on-site measurements of mirror slope in parabolic trough collector fields, a new method is presented. It uses a set of pictures of the reflections of the absorber tube in the concentrator. The slope errors of the mirror surface are calculated with high spatial resolution and accuracy. The effects of the reflector slope deviations on the optical performance are evaluated with ray-tracing. The results give detailed information about the optical quality of the concentrator, inaccuracies in the manufacturing process, and their optical performance penalty.

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