Sun is the source of energy but it also has a dangerous side: discover ACS solutions for Solar Simulation Testing
How to check the resistance and behaviour of materials to prolonged exposure to solar radiation?
The solar simulation test: what it’s for
Exposure to solar radiation brings about a number of irreversible processes over time, causing various undesirable effects on performance and appearance, from the weakening of materials to the fading of colors. In order to ensure long life expectancy for a product, the resistance and behaviour of the materials to prolonged exposure to sunlight must be tested, if possible in combination with other factors such as temperature and humidity, so as to reproduce what happens in the environmental conditions during the life of the product.
How can we ensure that a product meets certain requirements before it is put on the market?
The solar simulation test is essential for all applications in which it is necessary to determine how products and materials react to solar radiation over their useful life.
There are many reference standards for testing resistance to solar radiation over time.
Two examples: DIN 75220 and MIL-STD – 810 tests.
DIN 75220
This type of test is for automotive applications: it is used to determine the ageing behaviour of polymer automotive parts.
It can be applied to complex assemblies or to entire vehicles, and therefore it is especially suitable for detecting interactions between different materials within a component or between several components.
Applying the test makes it possible to test conditions in three different zones:
- Outdoor: all parts that are on the outside, directly exposed to solar radiation;
- Indoor 1: the interior part of the vehicle where the glass in the windows lower the intensity of solar radiation, but significantly increase the temperature;
- Indoor 2: the interior part of the vehicle with a slightly lower temperature than the Indoor 1 zone.
MIL – STD – 810 (specific method for solar simulation testing)
The main objectives of this method are to:
- Determine the thermal effects of direct solar radiation on the material, or the effect of the heating of the sun’s rays.
- Help identify photodegradation (i.e. the deterioration process of materials) from direct solar radiation, helping to identify critical points.
By means of this standard, it is possible to simulate a typical day (procedure 1) or simulate the worst possible conditions (procedure 2), depending on the testing needs.
What is solar radiation?
The Sun plays a fundamental role for life on Earth: it makes life on our Planet possible and nourishes it. It is at the right distance for there to be water on the Earth’s surface, it regulates the climate, it marks the days and, thanks to its magnetic field, it protects us from potentially dangerous particles coming from the rest of the universe. But all this energy that reaches us in the form of radiation and particles has consequences for life and for the lifetime of infrastructures and materials.
Solar radiation is composed of ultraviolet rays, visible light and infrared radiation.
The spectrum of solar radiation at the Earth’s surface has different components: direct, diffuse and reflected. The sum of these components is called global solar radiation.
Sunlight passes through the atmosphere, which is composed of many substances including water vapor, aerosols, clouds, oxygen, carbon dioxide, nitrogen, etc.. Some of these substances partially absorb or deflect the sun’s rays.
Diffuse solar radiation is the whole of the sun’s rays that are deflected by substances in the atmosphere, while direct radiation consists of all the sun’s rays that reach the ground without their path being disturbed by these substances. The radiation that reaches the ground can be partially absorbed by the earth’s surface, and part of it is reflected back upwards, which is called reflected solar radiation.