Collector technology
The SOLITEM PTC 1800 collector will be used in the pilot installation. This parabolic trough collector system is assembled from modules with an aperture width of 1,8 m and a length 5 m each. The concentrator consists of aluminium sheet kept in shape by specially manufactured aluminium profiles. ALANOD Mirosun reflector sheets are glued onto this structure. Additional stiffness is provided by a torsion tube mounted at the back of the concentrator. Up to 4 modules installed in series form a row, 6 rows can be connected to a single drive unit to be tracked via a rope and pulley arrangement. A sun position calculation gives the input for an approximate tracking of the collectors while sun sensors installed in several locations of the collectors provide data for a precise positioning (fine tuning). Mounted in the focal line is a stainless steel absorber tube with 40 mm diameter, which has been galvanically coated with a selective surface. A non-evacuated glass envelope reduces the convective heat losses from the absorber. Flexible hoses with thermal insulation and a metal fabric envelope connect the moving absorber tubes with the stationary field piping.
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To obtain reliable performance data for design and performance calculations, a single row has been installed at the DLR test facilities in Cologne for a measurement campaign in summer 2008 (Figure 1). For the design 
Design considerations
