Summary Report Impact Resistance Testing(3)

d. Collectors that cannot be classified clearly into the category a.) b.) or c.) need to be tested at each ice ball diameter with 16 shots.

The impact points needs to be distributed evenly across the whole collector area. The coordinates of the impact points need to be defined before the testing, mentioned in the testing report and have to be documented with photos.

The following rule applies to all collector types: Are further obviously weak spots visible, having an influence of the functionality or safety of the collector (e.g. frame, mounting parts, exposed fluid containing parts, mirrors etc.) they need to be tested additionally. Each spot needs to be tested applying four shots at the chosen diameter.

These weak spots need to be mentioned and documented with photos in the testing report. It has to be documented if no further weak spots are identified.

5.1 Missing shots

Missing shots with velocities beyond the tolerance need to be mentioned in the

protocol. Shots with too low speed are not valid and need to be repeated. Shots with too high speed are valid if no damage occurs.

5.2 Elements for facades

Collectors especially made for the use in facades may also be tested as elements for facades. The angle of the ice ball shooting impact needs to be lower than 45° and is not vertical to the collector surface. For vacuum tube collectors it needs to be Project IEE/08/593/SI2.529236

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documented that the tubes are oriented vertically. The test angle is 45°. Tubes being installed horizontally cannot be considered as elements for facades.

6 Function of components

The thermal collector is proved of appearance and mechanical aspects.

6.1 Damage criteria

Appearance: Aesthetical defects (little dents) affecting negatively neither the

function nor the power output of the collector, need to be documented in the testing report but are not a failing criterion. Dents with a depth > 3 mm and dents being readily identifiable in a distance of 5 m are a failing criterion.

Mechanical aspects: Breaking of the glass or other damage of the cover or other collector parts affecting negatively according to the test laboratory the durability (e.g. leakiness) or power output (due to dissolution of coating, scattering of cover) or influencing negatively the safety of the product are failing criterions.

6.2 Measuring method

Appearance: The appearance is tested under daylight or artificial light without dazzling effect and a distance of 5 m between the testing person and the object.

Mechanical aspects: The solar collector needs to be examined visually (distance testing person and sample object maximum 0.5 m)

7 Test report

The test report contains all the technical details relevant for a test report according to EN12975. Additionally details on the testing instruments and the testing procedure need to be mentioned. All impact points are documented (also the impact points resulting form shots out of the tolerance of speed) including the weight of the ice ball and the measured speed.

8. Text proposal for prEN ISO 9806

“Impact resistance test

Objective

This test is intended to assess the extent to which a collector can withstand the effects of heavy impacts caused by hailstones

The testing of the solar collector to determine its impact resistance can be done by one of two methods, i.e. by using ice balls or steel balls. As the steel ball does not lose any energy due to its deformation at the impact it is assumed that this method is the more severe if the two methods are carried out with balls giving the same kinetic Project IEE/08/593/SI2.529236

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energy. Therefore method 2 (Steel ball) shall only be used for “pass” judgements. If method 2 results in a failure, this must be confirmed by a test according to method 1.

Method 1: Impact resistance test using ice balls

As test method 1 is closer to reality for hail resistance, this method is

preferable.

NOTE

Apparatus

a) Moulds of suitable material for casting spherical ice balls of the required

diameter. The diameters are given in

c) A freezer, controlled at -10 °C ± 5 °C.

d) A storage container for storing the ice balls at a temperature of -4 °C ± 2 °C. e) A launcher capable of propelling an ice ball at the velocity as specified by the

manufacturer according to

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f) Table 6 within ± 5 %, so as to hit the collector within the specified impact

location. g) A rigid frame for supporting the collector, with the impact surface

perpendicular to the path of the projected ice ball; the support shall be stiff enough so that there is negligible distortion or deflection at the time of impact.

NOTE In some cases the impact resistance of others then the perpendicular angle might be of interest.

h) A balance for determining the mass of an ice ball to a standard uncertainty of

± 2 %.

i) An instrument for measuring the velocity of the ice ball to a standard

uncertainty of ± 2 ms-1. The velocity sensor shall be no more than 1 m from the surface of the collector. As an example, Error! Reference source not found. shows in schematic form a suitable apparatus comprising a horizontal pneumatic launcher, a vertical collector support and a velocity meter which measures electronically the time it takes the ice ball to traverse the distance between two light beams. This is only an example as other types of apparatus including slingshots and spring driven testers have been successfully utilized. Ice balls

The ice balls shall be made of water. They shall be entirely free of air bubbles and shall not have cracks that are visible to the unaided eye. The standard diameter shall be 25 mm but any of the diameters listed in

Table 6 may be specified for special environments. The testing procedure is being

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