Linked to IEA-SHC Task 33, several new development activities on process heat collectors were carried out. In order to give a short overview on these developments, three categories may be introduced:

• vacuum tube collectors and improved flat-plate collectors: double-glazed flat plate collectors with anti-reflection glazing and hermetically sealed collectors with inert gas fillings, or a combination of both. These collectors are installed in a fixed orientation; no tracking of the collectors. Full utilisation of the global solar radiation.

• stationary (i. e. non-tracking) low-concentration collectors: stationary CPC type collectors. The concentration factor is low (approx. 1.5 … 2) in order to avoid tracking. The acceptance angle of the concentrating reflectors reduces the utilisation of the solar radiation.

• concentrating tracking collectors: parabolic trough, Fresnel collectors or Fixed Mirror Solar Collectors (FMSC) with small aperture widths. Only the direct solar radiation is utilised.

The booklet (see Fig. 2) can be downloaded from http://www. iea-

shc. org/publications/downloads/task33-Process_Heat_Collectors. pdf. It is an outcome of the Subtask C of the SHC-IEA-Task 33. In a first part, a general description of the following different collector technologies is given :advanced flat-plate collectors, evacuated tube collectors, CPC-collectors, parabolic trough collectors, linear concentrating Fresnel collectors and finally concentrating collectors with stationary receiver.

In the second part of the booklet information from the developers of 14 different process heat collectors is given on their specific collectors. These developers were (some more, some less) linked to the work of the Task.

Solar

IEA SHC-Таєк 33 and SolarPACES-Task IV Solar Heat for Industrial Processes

Process Heat Collectors

State of the Art within Task 33/IV

Edited by Werner Weiss. AEE INTEC. Austna

and Matthias Rommel, Fraunhofer ISE Germany

Fig. 2. The booklet ‘Process Heat Collectors’ is an outcome of IEA-SHC Task 33. It has 56 pages and can be downloaded at www. iea-shc. org

Just in order to give some impressions of new concentrating collector developments aiming at higher operating temperatures, fig 3 shows an example for a parabolic trough collector which is under

development in Australia, the NEP SOLAR PolyTrough 1200. The mirror panel carriers are made of polymeric composite materials and are light weight. The aperture width of the trough is 1.20m, the length of a trough panel is 6m and a standard module has a length of 24m. The focal length of the reflector is 0.65m and the geometrical concentration ratio is 45. Solar tracking is achieved trough a microprocessor controlled stepper motor and reduction drive. The target operating temperature is 150 to 275°C, depending on the application. Generally, the constructive challenges to be met are sufficient stiffness with respect to bending, sufficient precision of the reflector geometry and a general long term stability of all components and the total construction.

Figure 4 shows a picture of a linear Fresnel collector developed by the company PSE AG, Freiburg. This collector was installed in Sevilla, Spain in 2008. It is already the third collector which PSE installed, after two testing collectors erected and investigated in Freiburg, Germany and in Bergamo, Italy. The collector aims at the same operating temperature range. In Bergamo, the collector is supplying heat to an NH3/H2O absorption chiller. The width of a single reflector is 0.5m, the total width of the collector is and the length of one module is 4 m. The largest of these installations is the 176 kWth collector in Seville Spain shown in the picture, where the collector powers a double effect LiBr chiller.

In these two examples tracking of the sun is achieved by moving the reflector. But it is also possible to have the reflector installed in a fixed position and then move the receiver. The concept is called "Fixed Mirror Solar Collector (FMSC)". Figure 5 shows an example: the CCStaR-collector (Concentrating Collector with stationary Reflector) which is still under development by the company TSC, Barcelona and the Universitat de les Illes Balears, Palma de Mallorca, Spain.

It is interesting to point out that building — and roof-integration is an important and challenging aspect for the application of large process heat collector fields (which in the end mainly will have to be installed on buildings and factory roofs). Also under this aspect the different collector technologies offer different advantages and application chances so that it is positive to have different possibilities available.

Please have a look on the booklet for more information on these collectors and on all the others.