Rotating test bench for parabolic troughs enters service at the PSA in southern Spain
The German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR) and the Spanish Centro de Investigaciones Energéticas Medioambientales y Tecnológicas (CIEMAT) have brought an innovative, rotary test bench for parabolic troughs into operation at the Plataforma Solar de Almería (PSA) in southern Spain. Using this test bench, researchers will be able to test parabolic trough collectors up to 20 metres long at any angle to the Sun and measure their efficiency.
The new test stand, named KONTAS (Konzentrator-Teststand Almeria Spanien) can be used to evaluate complete modules of parabolic trough collectors, as well as individual components such as the mirrors and absorber pipes. Here, researchers can test, among other things, the efficiency with which the mirrors focus the sunlight onto the absorber pipes. During this testing, researchers are able to analyse how well the absorber pipes can convert solar radiation into heat; they are also able to measure heat losses. The DLR Institute of Solar Research and CIEMAT carry out these tests on behalf of manufacturers from the solar-thermal power industry. "With our evaluations, manufacturers can improve their products and develop parabolic troughs for more efficient and cost-effective solar power stations. Young companies as well as many market leaders benefit from our findings," says Peter Heller from the DLR Institute of Solar Research.
Rotating on steel rails
The KONTAS test bench is unique in terms of its mobility. Parabolic reflectors in solar power stations can usually only rotate about their longitudinal axis to track the elevation of the Sun. On this test bench, the collectors are mounted on a six-wheeled rotating platform that moves on circular steel rails; the parabolic mirror can be rotated almost 360 degrees about its vertical axis. "A parabolic trough collector in a solar power station has an orientation to the Sun that depends on the latitude of its location. The closer it is to the equator, the steeper the angle of incidence of the Sun's rays onto the trough. With this rotating test bench, we can adjust elevation and azimuth angles independently and thus simulate any arbitrary orientation of the collector with respect to the Sun," Heller explains while describing the test bench's potential.
Simulating the conditions in a solar power station
Incoming solar radiation, which is collected by the mirror, heats up thermal oil inside the absorber pipe to 400 degrees Celsius. In a solar-thermal power station, this heat is used to produce steam, which is then used to generate electricity using a turbine. On the test bench, the thermal oil is cooled in a cooling unit by a controlled process, allowing energy researchers to replicate the use of the parabolic reflector in a power station and quickly determine the plant's efficiency.
Increased efficiency for solar power stations
The KONTAS test bench is part of the Test and Qualification Centre for Concentrating Solar Power Technologies (QUARZ), which has its headquarters in Cologne. Since 2009, manufacturers and customers of solar-thermal systems have been coming here to test reflectors and absorber pipes for solar power stations. The researchers have developed their own testbeds and methods to conduct these quality tests. They have succeeded in developing internationally recognised quality standards for key components. QUARZ is part of the DLR Institute of Solar Research.