Summary Report Impact Resistance Testing

Quality Assurance in solar thermal heating and cooling technology

Keeping track with recent and upcoming developments

Summary report

Impact resistance testing

Fraunhofer ISE, Freiburg, Germany

Korbinian Kramer, korbinian.kramer@ise.fraunhofer.de

Version 3

Date: 30.05.2012

QAiST is supported by Intelligent Energy Europe

Project IEE/08/593/SI2.529236

Deliverable D2.2 – R2.16

Table of contents

7. INTRODUCTION ........................................................................................................................ 3 HAIL STONE TESTING IN THE IEC STANDARD FOR PV MODULES (IEC 61215) ............................. 3 HAIL STONE TESTING IN THE SWISS PROCEDURE ...................................................................... 4 HAIL STONE / IMPACT RESISTANCE TESTING IN THE EN 12975 .................................................. 4 PROPOSAL FOR HAIL STONE TESTING FOR PREN ISO 9806 ........................................................ 5 ON-GOING AND FUTURE WORK ................................................................................................ 6 ANNEX A “WORKING PAPER OF QAIST” .................................................................................... 8

INTRODUCTION ................................................................................................................................. 8

DISCUSSION: ..................................................................................................................................... 8

METHODS ......................................................................................................................................... 8

1 GENERAL ........................................................................................................................................ 8

2 AREA OF APPLICATION ................................................................................................................... 8

3 TEST ITEMS ..................................................................................................................................... 8

GROUP I: FLAT PLATE COLLECTORS WITH ONLY ONE SINGLE COVER . ............................................... 8

4 TEST SETUP ..................................................................................................................................... 9

4.1 PRE-STORAGE OF THE SAMPLE .................................................................................................... 9

4.2 ICE BALLS ..................................................................................................................................... 9

TABLE 1: MASS OF THE ICE BALLS AND TESTING VELOCITIES ............................................................. 9

5 SHOOTING AREA AND ANGLE ......................................................................................................... 9

5.1 MISSING SHOTS ......................................................................................................................... 10

6 FUNCTION OF COMPONENTS ....................................................................................................... 11

THE THERMAL COLLECTOR IS PROVED OF APPEARANCE AND MECHANICAL ASPECTS..................... 11

6.1 DAMAGE CRITERIA .................................................................................................................... 11

7 TEST REPORT ................................................................................................................................ 11

8. TEXT PROPOSAL FOR PREN ISO 9806 ...................................................................................... 11 “IMPACT RESISTANCE TEST ....................................................................................................................... 11

Objective ....................................................................................................................................... 11

Method 1: Impact resistance test using ice balls .......................................................................... 12

Method 2: Impact resistance test using steel balls ....................................................................... 15

Results ........................................................................................................................................... 16

GENERALLY: .................................................................................................................................... 16

PROS: .............................................................................................................................................. 16

9. LIST OF RELATED LITERATURE ................................................................................................. 17

Project IEE/08/593/SI2.529236

Summary report – R2.16 - Hail resistance testing Page 2 of 19

1. Introduction

Hail stone testing with real ice balls is a common procedure in testing outdoor

exposed products which have a functional or safety relation to eventual cracking or breaking (e.g. PV modules are tested according IEC 61215 chapter 10.17).

There are two methods for impact resistance testing described in chapter 5.10 of EN 12975. One method is using a steel ball of 150g and dropping it on the collector surface to check the resistance. The second is using an ice ball of 25mm.

A future market for solar thermal products when they are used as fa?ade integrated elements fulfilling not only one, but several purposes. The level of resistance towards hail is then one important characteristic.

Because of a tendency of an increasing number of increasingly severe hail events, insurance companies are interested in a clear statement on hail resistance of solar collectors based on third party tests.

2. Hail stone testing in the IEC Standard for PV modules (IEC 61215)

The method allows using one of the following ice ball sizes:

Table 1: Ice balls allowed to be used according to IEC 61215

Requirements for these ice balls are:

- - -

No cracks visible to the unaided eye Diameter within +-5% of that required

Mass within +-5% of the appropriate nominal value of table above

The test is mandatory.

Project IEE/08/593/SI2.529236

Summary report – R2.16 - Hail resistance testing

Page 3 of 19

3. Hail stone testing in the Swiss procedure

The Swiss procedure allows using one of the following ice ball sizes:

Table 2: Ice balls allowed to use according to the Swiss testing procedure

structure. Instructions for production and storing of the ice balls are identically with IEC 61215.

The test is mandatory.

4. Hail stone / Impact resistance testing in the EN 12975

Chapter 5.10 allows for two (both optional) methods of impact resistance test. One is using a steel ball another is using an ice ball. The steel ball used is:

Table 3: Steel ball allowed to be used according to EN 12975

Table 4: Ice ball allowed to be used according to EN 12975

Project IEE/08/593/SI2.529236

Summary report – R2.16 - Hail resistance testing

Page 4 of 19

5. Proposal for hail stone testing for prEN ISO 9806

In prEN ISO 9806 a mandatory hail resistance test is proposed. The procedure for this test was developed and discussed within the QAiST project.

The discussion was constructive in the sense that despite the fact that there were quite different opinions within the QAiST group, a common proposal for revision of this test could eventually be included in the new standard draft. The proposal reflects on the one hand the interests of the industry to have a simple, cheap and repeatable method using the steel ball and on the other hand the test labs asking for a method closer to “real conditions” harmonized with the method used in PV module testing. In the end there was a proposal prepared and handed over to the CEN TC 312 WG1 secretariat and so there is a changed revision available in the prEN ISO 9806. The proposal is bringing together the definition on collector classes from the Swiss approach. It takes over partly the table of acceptable ice balls from the IEC 61215. It defines very detailed the point of impact where to shoot at and the number of shots. Particularly on this issue the draft will be commented, because of feed back from partners, telling that where to shoot is not clear. In a CEN TC 312 WG1 meeting in Stockholm, there was a longer discussion on the possible procedure. Most aspects of the consensus which was discussed there was implemented in the proposal (see also minutes of the TC meeting), some points were over looked without intention and have to be commented during inquiry phase still.