Today LED based solar simulators are increasingly available in the marked as an alternative to the standard Xenon flashers. LED based solar simulators offer crucial benefits compared to the conventional solution of the Xenon technology.
A well-known disadvantage of the Xenon technology is the relatively short life time of the Xenon lamps.They are continuously aging and must be exchanged after only a few months. The resulting spare part costs, the personnel expenditure and higher operating expenses caused by the down times lead to considerable maintenance costs of the systems.
Another disadvantage of Xenon lamps is the relatively short flash duration. Due to the capacitive effects of today’s widely available high efficient solar modules significant measurement difficulties occur.
LED solar simulators are addressing the disadvantages of the Xenon technology. With an LED Flasher a long flash duration can easily be realized and the LEDs are designed for several million flashes.Under normal operational conditions an exchange of LEDs is not necessary anymore. In lab tests up to 10 million flashes with constant electrical current were carried out to prove it. At the end of the tests the degradation of the LEDs was less than 0.5% of the initial value. This yields to a stable luminosity and spectrum over the whole product lifetime. 10 million flashes correspond to a life span of 10 years with a cycle time of approx. 30s. The result is an immense costs saving compared to the costs occurring for a Xenon flashers product lifetime.
Another advantage of the LED technology is the smart form factor. LED flashers are usually built up as compact table flasher. The integration into the productionline is much simpler than before:for the measurement the modules can remain intheirnormal orientation (sunny side down) without theneed to turn the module to a vertical or sunny side up orientation normally required for a tower or tunnel flasher.
An additional advantage of the LED technologyis that the single LED or thegroups of LEDs can be controlledvery precisely. This control allows a nearlysteady luminosity over the entire flashduration. The stability of the light source is beneficialfor themeasurementrepeatability. In testsan up to 5 times better repeatability was achievedcompared to Xenon solar simulators.
New demands from customers and newmodule designs providenewchallenges to the manufacturersof LED flashers. With the still valid standard for sun simulators IEC 60904-9 edition 2 it was possible to achieve the classification AAA with only 5 different types of LEDs. The new standard IEC 60904-9 edition 3 has a revised partitioningof thespectral areas. To cover the revised spectrumat least 7 different types of LEDs are necessary.
Besides the new standard many customers demand that the new solar simulators additionally emits light in the spectral region below 400 nm (UV) and in the region above 1000 nm (IR). LEDs with the mentioned wavelength are particularly expensive which leads to considerably higher manufacturing costs for these solar simulators. Nevertheless, with the long live time of LEDs and the resulting low maintenance costs this will easily counter balance the initial system costs.
For the new bifacial modules the LED technology offers new possibilities. Abifacial module canbe measured by simplyputting one additional LED unit above the module. Following the requirements for bifacial modules, the module can bemeasured first with 1000 W/m² from the sunny side and in a second step with 100-300 W/m² from the back. Next to that, it is also possibleto combine the measurement and measure the total power with one flash with predefined settings for each of the two light source (the one for the sunny side and the one for the back side).
The second generation triple A+ LED solar simulator from MBJ is prepared for the new standard edition 3. It already includes the increased requirements for the spectral distribution and the option for an enlarged spectrum below 400 nm and above 1000 nm in the new design.