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Revision of Special Test Procedure for Collectors

Proposal to revise the "10% rule" for collector testing due to limitations in accuracy and completeness. Two-step approach involves third-party verification and retesting if necessary.

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Revision of Special Test Procedure for Collectors

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  1. Report Revision of the special test procedure for collectors Stephan Fischer, Harald Drück Institute for Thermodynamics and Thermal Engineering (ITW) Research and Testing Centre for Thermal Solar Systems (TZS) University of Stuttgart Pfaffenwaldring 6, 70550 Stuttgart, Germany Email: fischer@itw.uni-stuttgart.de Internet: www.itw.uni-stuttgart.de

  2. Background The so called "10 % rule" described in the Solar Keymark Scheme Rule in section 6.3 Special test, 6.3.1 Compliance with registered values Collectors (EN 12975): “The integral of the measured instantaneous efficiency at the special test shall be more than 90% of the already registered integral in the interval of the reduced temperature from 0 – 0,1 K/(W/m²). The reduced temperature is defined in EN 12975-2, paragraph 6.1.4.8.3, and the instantaneous efficiency in 6.1.4.8.4.2.”

  3. Background

  4. Background • "10 % rule" not appropriate due to the following reasons: • threshold of 10 % is too high to be applied successfully on doubtful results • criteria of the instantaneous efficiency does not take into account the incidence angel modifier and thus does not give a complete picture of the thermal performance of the collector

  5. Approach • Use of the collector yield documented on the second page of the Solar Keymark data sheet for different mean temperatures and locations.

  6. 1st Proposal “the annual collector output at Athens, Davos, Stockholm and Würzburg at a mean fluid temperature 25 °C shall exceed 96 % of the already registered values (Solar Keymark data sheet page 2) and the annual collector output at Athens, Davos, Stockholm and Würzburg at a mean fluid temperature 50 °C shall exceed 92 % of the already registered values (Solar Keymark data sheet page 2) and the annual collector output at Athens, Davos, Stockholm and Würzburg at a mean fluid temperature 75 °C shall exceed 85 % of the already registered values (Solar Keymark data sheet page 2)”

  7. Comments received after 23rd meeting Boundaries to narrow (Jan Erik Nielsen, Costas Travasaros) Boundaries to wide (Stefan Abrecht) Use documents and visual inspection before testing (Costas Travasaros) Proposal to use narrow approach, if values are within the narrow boundary initial test is accepted, if not define additional measures (Andreas Bohren)

  8. 2nd Proposal 1st Step: Establishment of third party team according to section 2.2.3 Solar Keymark Specific Scheme rules Version 30.

  9. 2nd Proposal 2nd Step: Third party team compares the materials and technical specifications delivered for initial testing with the materials and technical specifications of the current test sample based on the manufactures production control documents including delivery notes and incoming good inspections. In addition the current test sample is compared with the material and technical specifications delivered for the initial testing. In case discrepancies are found in the comparisons the collector must be retested and the new test results will be valid. Costs are borne by the manufacture of the collector whose results have been challenged. In case no discrepancies are found proceed with 3rd step.

  10. 2nd Proposal 3rd Step 1/2: • Third party team checks Solar Keymark data sheet, test report and technical specifications as delivered for initial testing and decides whether the results are plausible or not. • In case the third party team decides that the values are not plausible the collector must be retested and the new test results will be valid. • if only the Solar Keymark data sheet contains errors which are not in the responsibility of the manufacturer e.g. failure in the calculation wrong values etc. the cost have to be borne by the issuing body/test institute.

  11. 2nd Proposal 3rd Step 2/2: b) if the third party team takes the decision that the values are not plausible and a re-test is ordered there are two cases about the cost: ba) the annual collector output of the re-test anyway fulfills the requirements set for 25 °C, 50 °c and 75 °C then the complainant bears the cost (note: this case might be seldom but possible, that strange parameters lead to similar results like parameters which look normal. This is not the fault of the manufacturer) bb) the annual collector output of the re-test does not fulfill the requirements set for 25 °C, 50 °c and 75 °C then costs are borne by the manufacture of the collector whose results have been challenged. In case no discrepancies are found proceed with 4th Step

  12. 2nd Proposal 4th Step 1/2: A thermal performance test including incident angle modifier test according to ISO 9806 is performed by another test laboratory than the one which carried out the initial test and the annual collector output is calculated using the Solar Keymark datasheet.

  13. 2nd Proposal 4th Step 2/2: In case “the annual collector output at Athens, Davos, Stockholm and Würzburg at a mean fluid temperature 25 °C exceeds 98 % of the already registered values (Solar Keymark data sheet page 2) and the annual collector output at Athens, Davos, Stockholm and Würzburg at a mean fluid temperature 50 °C exceeds 96 % of the already registered values (Solar Keymark data sheet page 2) and the annual collector output at Athens, Davos, Stockholm and Würzburg at a mean fluid temperature 75 °C exceeds 92 % of the already registered values (Solar Keymark data sheet page 2)” the process stops here and the initial values are confirmed. Costs are borne by the complainant. In case the values are not meet continue with step 5.

  14. 2nd Proposal 5th Step 1/2: The third party team identifies a second collector which represents the main features of the collector under investigation (e. g. flat plate collector, PVT collector, evacuated tubular collector). Two collectors of this kind are purchased from the same batch. One will be tested by the test laboratory which carried out the initial test the other by the test laboratory which carried out the test under 4. Both results are compared by means of annual collector output for Athens, Davos, Stockholm and Würzburg at a mean fluid temperature of 25 °C, 50 °C and 75°C. The difference for each location and mean fluid temperature is used to adjust the annual collector output calculated under 4.

  15. 2nd Proposal 5th Step 2/2: In case after adjustment of the values “the annual collector output at Athens, Davos, Stockholm and Würzburg at a mean fluid temperature 25 °C exceeds 98 % of the already registered values (Solar Keymark data sheet page 2) and the annual collector output at Athens, Davos, Stockholm and Würzburg at a mean fluid temperature 50 °C exceeds 96 % of the already registered values (Solar Keymark data sheet page 2) and the annual collector output at Athens, Davos, Stockholm and Würzburg at a mean fluid temperature 75 °C exceeds 92 % of the already registered values (Solar Keymark data sheet page 2)” the initial values are confirmed and the process stops here. Costs are borne by the complainant. In case the values are not meet continue with step 6.

  16. 2nd Proposal 6th Step: The new test results will be valid for the collector under investigation. Costs are borne by the manufacture of the collector whose results have been challenged.

  17. Discussion …

  18. Thank you …

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