M. Meir1*, J. Buchinger2, S. Kahlen3, M. Kohl4, P. Papillon5, J. Rekstad1, G. Wallner6

1 University of Oslo, Department of Physics, P. O. Box 1048, N-0316, Oslo, Norway

2) Arsenal Research, Giefinggasse 2, A-1210 Vienna, Austria

3) Polymer Competence Center Leoben, Roseggerstrasse 12, A-8700 Leoben, Austria

4) Fraunhofer Institute for Solar Energy Systems, Heidenhofstr. 2, D-79110 Freiburg, Germany

5) CEA-INES, BP 332, 50, avenue du Lac Leman, F-73377 Le Bourget du Lac, France

6) University of Leoben, Institute of Materials Science and Testing of Plastics, Franz-Josef Str. 18, A-8700

Leoben, Austria

* Corresponding Author: mmeir@fys. uio. no
Abstract

The state of the art of polymeric materials in solar thermal applications is reviewed in IEA — SHC Task 39. The present status with regard to solar thermal collectors is summarized. Ex­amples of favourable solar heating system — and solar collector designs of polymeric materi­als are illustrated. Overheating protection opens for the application of commodity plastics in glazed collectors. Various absorber types are compared from a polymer-engineering point of view.

Keywords: Polymeric materials, solar collectors, IEA-SHC Task 39, plastics;

1 Introduction

Approximately 40% of the final energy demand in the EU25 member states is used for low tem­perature heating and cooling — a share, which is in principle easily accessible with solar thermal technology [1]. However, the fraction of energy use covered by solar thermal is nearly negligible and still below 0.05% in the European countries [2]. In the Sustainability Report 2006 by Bank Sarasin [3] an annual growth rate of 25-30% of newly installed global collector capacity is ex­pected up to 2010. Conventional solar collector systems are based on materials (e. g. copper) with limited availability. The material supplies will not be large enough to cover up for the expected growth in solar thermal installations. These issues demand the introduction of new materials, of which polymers seem to have a strong preference in all respects. Polymers reveal a large cost — reduction potential due to mass production, reduction in weight, freedom in structural and func­tional design and the potential to lead to a breakthrough for solar thermal energy production.

Polymeric collectors had a market share of 19% of the worldwide solar heating capacity in opera­tion in 2006 [4], which are almost exclusively unglazed absorbers for swimming pool heating. The US represents the largest market for polymeric pool absorbers with a power production of

19.2 GWth in operation at the end of 2006. Pool absorbers are applicable in the low temperature range. In order to meet the requirements from the market for heating applications in the medium and high temperature range, the introduction of new polymeric materials and technology is essen­tial. New materials can only be applied if the service-life is comparable to those in conventional products. Task 39 is a collaborative effort in the International Energy Agency’s Solar Heating and Cooling Programme, which brings together solar thermal — and polymer experts from research insti­tutions and industry working on these challenges. IEA-Task 39 is divided in three Subtasks,

A: Information, B: Collectors and C: Materials. An on-going effort is the preparation and update of a database on existing applications, prototypes and patents with regard to polymers in solar thermal applications. The present work gives a brief overview limited to solar thermal collectors and inte­grated storage collectors.

2 System design