news / 2013-11-23

Collectors on the test stand

Kontas is a swivelling testing stand for parabolic trough collectors. (Source: DLR)

The performance capability of receivers in parabolic trough plants is described by two properties: the optical efficiency and the thermal losses. These properties are measured in non-destructive tests on laboratory test stands in the DLR’s QUARZ Centre. To measure thermal losses, the receiver is heated to different operating temperatures.

Based on the heat output it is then possible to determine the thermal losses at these temperatures. To assess the optical efficiency, the receiver is radiated in a solar simulator. The absorbed output is determined by means of the heated water flowing through it, i.e. calorimetrically. A particular challenge here is to achieve the necessary measurement accuracy of, at best, less than one per cent. In addition to having a high performance capability, sufficient durability is also required to prevent having to replace receivers installed throughout the solar array at a later date. To test the durability of the absorber layer, the receivers undergo accelerated ageing by overheating them across several weeks and then subsequently measuring their optical and thermal properties again.

 

The Kontas test stand was constructed in 2010 on the Plataforma Solar de Almería (PSA) to enable entire collector modules to be tested. It is located on a swivel platform on which parabolic trough collectors with a length of up to 20 metres can be installed. The test stand makes it possible to qualify all collector components, ranging from metal structures, reflectors, receivers and flexible tube connections to entire collectors. The dual-axis tracking provides it with considerable flexibility in terms of the solar radiation’s angle of incidence on the test collector. The test stand is equipped with high-precision sensors that enable efficiency measurements with an uncertainty of ±2%.

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