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LEDs bring the sunlight into our lab

Measuring the power of solar modules by means of an LED-based solar simulator

PTB-News 2.2019
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PTB has recently started using an LEDbased solar simulator that is capable of varying the spectral composition, the brightness and the duration of the simulated solar irradiance independently of each other. The instrument thus provides decisive advantages over its conventional xenon counterparts. At PTB, solar modules can now be examined with a broad array of tests that are closer to real operating conditions.

Over its surface of 2.40 m × 4.70 m, the LED-based solar simulator is equipped with a total of 16 320 LEDs. On the measurement plane, the colored light of the LEDs mixes to yield a spectrum similar to that of the sun.

Solar modules are the main components of any photovoltaic facility. When planning a new solar facility, many different solar module variants are available. Depending on the fabrication process, their price and the output to be expected vary. Conditions that are close to real operating conditions and low uncertainties in the power determination of solar modules support manufacturers and planners in selecting the best-suited module type for the location of a given facility. This provides better planning security.


In the field of photovoltaics, PTB currently provides calibration services mainly for reference solar cells with dimensions of (2 × 2) cm2. It is planned to extend the range of services to measurements carried out on solar modules of up to (2 × 1) m² in size. The LED-based solar simulator is a key element in this strategy. It bundles 16 320 high-power LEDs into one highly efficient light unit that can irradiate the desired surface with light that matches the brightness and spectral composition of midday sunlight. The simulator consists of 18 differently colored and individually adjustable types of LEDs with emission spectra ranging from 370 nm (UV) up to 1100 nm (NIR) that can be individually adjusted. If different LED colors are combined, it is possible to simulate not only the usual PV standard spectrum, but also many irradiance conditions experienced by solar modules when exposed to real outdoor operating conditions.

This allows PTB to develop measurement sequences that lead to a more realistic evaluation of the module᾽s energy output. Both the cloudiness and the sun elevation have a considerable influence on the solar radiation that reaches a solar module. This variation can be simulated by means of the new solar simulator. The measurements thus allow the yield of new PV facilities to be forecast more accurately.


Stefan Riechelmann
Department 4.5
Applied Radiometry
Phone: +49 531 592-4149
Opens window for sending emailstefan.riechelmann(at)ptb.de