The work in IEA-SHC Task 39 includes the study of polymeric materials in solar thermal applica­tions from a polymer-engineering point of view [17]. An overview of selected absorber designs of polymeric materials is presented in Table 1. Depending on the absorber and the manifold, five dif­ferent concepts are shown for the design of commercial polymeric solar absorbers: (1) pipe+pipe, (2) panel+pipe, (3) panel+endcap, (4) film+pipe, (5) panel. While the concepts (1) to (4) are based on extruded absorbers and injection moulded manifolds, which are connected by mechanical fix­ing, gluing or welding, the panel concept is based on blow — or roto-moulded components with inte­grated semi-finished fittings. Advantages of the panel concept are a reduced number of processing steps, the use of semi-finished components (fittings) and the possible realization of more complex absorber designs. However, panel concepts (5) are limited in the length of the absorber. An impor­tant prerequisite for concepts (1) to (4) is the use of similar materials, especially thermoplastics, for the absorber and the manifold. Compared to absorbers with pipe geometry, absorbers with flat sur­faces exhibit a better functionality/material-ratio (less material is required) and a better applicabil­ity of functional layers.

3 Summary

A large potential for innovative development of components and systems by using polymers is ex­pected in the solar thermal industry as successfully demonstrated in other industry sectors. A short presentation of various polymer applications in solar collectors, heating system designs, overheat­ing protection and the analysis of different absorber designs from a polymer-engineering point of view is given. A complete, updated review with evaluation and experiences will be prepared as a final deliverable of IEA-SHC Task 39. It will additionally include the state of the art of polymeric applications in small, medium-sized heat — and seasonal thermal stores and patented ideas. The offi­cial Task 39 website is: http://www. iea-shc. org/task39.

Acknowledgements — The lead of Subtask A of IEA-Task 39 "Polymeric materials in solar thermal applica­tions" is supported by ENOVA SF and the Research Council of Norway (RENERGI).

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