Hail Testing Methods and ObservationIntroduction Purpose To verify that the module is capable of withstanding the impact of hailstones. Hailstorms can cause severe damage to modules and collectors. Our test stand enables you to carry out tests according to international standards. The hail impact test stand uses an air-pressurized launcher that shoots ice balls representing hailstones of a predetermined size at the module or collector mounted on the support frame Requirements and procedure Molds of suitable material for casting spherical ice balls of the required diameter. The standard diameter shall be 25 mm but any of the other diameters listed in Table 1 may be specified for special environments. A freezer, controlled at –10 °C ± 5 °C. A storage container for storing the ice balls at a temperature of –4 °C ± 2 °C A launcher capable of propelling an ice ball at the specified velocity, within ±5 %, so as to hit the module within the specified impact location. The path of the ice ball from the launcher to the module may be horizontal, vertical or at any intermediate angle, so long as the test requirements are met. A rigid mount for supporting the test module by the method prescribed by the manufacturer, with the impact surface normal to the path of the projected ice ball. A balance for determining the mass of an ice ball to an accuracy of ±2 %. An instrument for measuring the velocity of the ice ball to an accuracy of ±2 %. The velocity sensor shall be no more than 1m from the surface of the test module. Procedure sing the moulds and the freezer, make a sufficient number of ice balls of the required size for the test, including some for the preliminary adjustment of the launcher. Examine each one for cracks, size and mass. An acceptable ball shall meet the following criteria: no cracks visible to the unaided eye; diameter within 5 % of that required; mass within 5 % of the appropriate nominal value in Table above. Place the balls in the storage container and leave them there for at least 1 h before use. Ensure that all surfaces of the launcher likely to be in contact with the ice balls are near room temperature. Fire a number of trial shots at a simulated target in accordance with step g) below and adjust the launcher until the velocity of the ice ball, as measured with the velocity sensor in the prescribed position, is within 5 % of the appropriate hailstone test velocity in Table above. Install the module at room temperature in the prescribed mount, with the impact surface normal to the path of the ice ball. Take an ice ball from the storage container and place it in the launcher. Take aim at the first impact location specified in Table 1 and fire. The time between the removal of the ice ball from the container and impact on the module shall not exceed 60 s. Inspect the module in the impact area for signs of damage and make a note of any visual effects of the shot. Errors of up to 10 mm from the specified location are acceptable. If the module is undamaged, repeat steps g) and h) for all the other impact locations in Table 1. Table 1– Impact locations Shot No. Location 1 Any corner of the module window, not more than one radius from the module edge. 2 Any edge of the module, not more than one radius of ice-ball from the module edge. 3, 4 Over edges of the circuit (e.g. individual cells). 5, 6 Over the circuit near interconnects (i.e. cell interconnects and bus ribbons). 7, 8 On the module window, not more than half diameter of ice ball from one of the points at which the module is mounted to the supporting structure. 9, 10 On the module window, at points farthest from the points selected above. 11 Any points which may prove especially vulnerable to hail impact like over the junction box. FINAL MEASURMENTS: Perform the visual inspection test to detect any visual defects in the module. Carefully inspect each module under an illumination of not less than 1 000 lux for the following conditions: – cracked, bent, misaligned or torn external surfaces; – broken cells; – cracked cells; – faulty interconnections or joints; – failure of adhesive bonds; – faulty terminations, exposed live electrical parts; – any other conditions which may affect performance. Make note of and/or photograph the nature and position of any cracks, etc. which may worsen and adversely affect the module performance in subsequent tests. Determine whether or not the module is sufficiently well-insulated between current-carrying parts and the frame or the outside world. Determine the maximum power of the module before and after the tests. Repeatability of the test is the most important factor. CONCLUSION (Final Observation and Results) The observations are as follows: – no evidence of major visual defects, as defined in Clause 7; – the degradation of maximum output power shall not exceed 5 % of the value measured before the test – insulation resistance shall meet the same requirements as for the initial measurements. References: IEC 61215 Document Claus 7: For the purposes of design qualification and type approval, the following are considered to be major visual defects: a) Broken, cracked, or torn external surfaces, including superstrates, substrates, frames and Junction boxes; b) Bent or misaligned external surfaces, including superstrates, substrates, frames and junction boxes to the extent that the installation and/or operation of the module would be impaired. c) A crack in a cell the propagation of which could remove more than 10 % of that cell's area from the electrical circuit of the module; d) Bubbles or delamination's forming a continuous path between any part of the electrical circuit and the edge of the module; e) Loss of mechanical integrity, to the extent that the installation and/or operation of the module would be impaired.