At present (summer 2008) approximately 430 different types of solar collectors and nearly 40 factory made systems are Solar Keymark certified. It is expected that two third of all solar thermal collectors sold in Europe are already qualified with a Solar Keymark /6/. A large number of the tests required for awarding the Solar Keymark were carried out at the Test and Research Centre for Solar Thermal Systems (TZS) located at the Institute for Thermodynamics and Thermal Engineering (ITW), University of Stuttgart.

6.1 Future development of Solar Keymark Certification Solar collectors

An assessment of the thermal performance of solar collectors directly on the basis of the efficiency parameters is not appropriate. Hence it is common practice to use the annual collector gain as a performance criterion, e. g. with regard to the qualification for subsidy programs. At present several national methods exist for the determination of the collector performance. This results in additional effort for manufacturers active in different European countries.

In order to overcome this problem, a method for the determination of the annual collector gains will be incorporated into the revised version of the Solar Keymark scheme rules.

Factory made systems

According to the current Solar Keymark scheme rules every factory made system has to be tested even if the system is part of a so-called system product line (or family respectively) and only differs in the collector area and/or the store volume. The huge effort resulting from this requirement is also the reason why the number of Solar Keymark certified collectors is approximately ten times higher than the number of certified systems. In order to overcome this problem a procedure was developed that allows the determination of the system performance of systems which are part of a system family by a mathematical procedure based on the test of only one system out of the product line /7/.

At present it is not finally decided if this procedure or an-other one /8/ based on the standard series EN 15316 (Heating systems in buildings — Method for calculation of system energy requirements and system efficiencies) will be included in the final revised version of the Solar Keymark regulations.

Custom built systems

Custom built systems are standardised in the European standard series CEN/TS 12977. Since the major share of systems sold in central and northern Europe are small custom built systems, it is favourable to extend the Solar Keymark also to that category of systems. Due to the fact that Solar Keymark certification must, in principle, be based on EN standards this is quite difficult since a CEN/TS document is formally not considered as an EN standard. At present several options to overcome this problem are under discussion but, even in the optimal case, a solution can not be expected before 2009.

3. Conclusions

The current status and the latest developments related to standards for solar thermal products and to Solar Keymark certification were described. The revised version of the European standard series

EN 12975, EN 12976 and CEN/TS 12977 contains appropriate requirements and test procedures for the products on today’s solar thermal market

The large number of already certified products clearly shows the success of the Solar Keymark. The Solar Keymark is on the best way to be established as THE quality and qualification label for solar thermal products all over Europe.

The combination of the European solar thermal standards and Solar Keymark certification provides an excellent basis for the further development of as sustainable solar thermal market in Europe. In the long-term all involved players — customers, manufacturers as well as test laboratories and certification bodies — will benefit.

References:

[1] Harald Druck, W. Heidemann, H. Muller-Steinhangen, A. Veenstra: European standards for thermal solar systems — the finals, Proceedings of ISES 2001 Solar World Congress, Pages 589 — 595, Adelaide, Australia, ISBN 0-9586192-7-1

[2] H. Druck, S. Fischer, H. Muller-Steinhagen: Solar Keymark Testing of Solar Thermal Products, Proceedings of ISES 2007 Solar World Congress, September 18 to 21, 2007, Beijing, China, ISBN 978-7­302-16146-2, Tsinghua University Press, Beijing and Springer-Verlag GmbH Berlin Heidelberg, CD: ISBN 978-7-89486-623-3

[3] H. Druck, E. Hahne: European test standard for the performance characterisation of stores for solar heating systems, Proceedings of Terrastock 2000, Pages 285 — 290, Stuttgart 2000, ISBN 3-9805274-1-7

[4] M. Peter, H. Druck, Testing of controllers for thermal solar systems, Solar Energy 82 (2008), pp. 676-685

[5] CEN: Specific CEN Keymark Scheme Rules for Solar Thermal Products, Final version 8.00 — January 2003 (ed. J. E. Nielsen). Available via

http://www. estif. org/solarkeymark/Links/Internal_links/solar_keymark_scheme_8.00.pdf

[6] www. solarkeymark. org

[7] H. Kerskes, B. Mette, H. Druck, H. Muller-Steinhagen: The Solar-Keymark Testing for Factory Made Systems by Means of an Extrapolation Procedure, Proceedings of Eurosun 2008, October 7 to 10, 2008, Lisbon, Portugal, to be published

[8] EN 15316-4-3: Heating systems in buildings — Method for calculation of system energy requirements and system efficiencies — Part 4-3: Heat generation systems, thermal solar systems

More information about the Solar Keymark is available at: www. solarkeymark. org.

The European Standards mentioned above are available from: www. beuth. de