Soiling Issues of Solar Systems

Surface contamination of solar energy systems, especially at low rainfall locations, leads to power losses due to shading or reflection of the incident light. Up to now, the surfaces have therefore had to be cleaned regularly at short intervals, which is associated with considerable costs. So how can adhesive soiling on solar modules be prevented?

Within the framework of experimental research by Fraunhofer CSP, it was possible to prove that a significant cause for the adhesion of soiling is the increased surface humidity or dew formation during the night and early morning hours. Heating to prevent dew formation and thus dust adhesion has so far failed due to a lack of a control concept.

Within the scope of the project, a highly sensitive surface humidity sensor system is to be developed, which allows energy-efficient heating of the surfaces of photovoltaic modules. After a configuration in the laboratory, a validation in real use at representative locations will be carried out. The aim is to determine the economic potential and control parameters depending on specific applications and weather conditions. In case of success, further potentials for wind power plants, CSP (Concentrated Solar Power) as well as in aviation are seen.

The project ETA-Tau is funded by the German Federal Ministry of Education and Research (BMBF) within the VIP+ programme (Contract no. 03VP08430).

Soiling Test Bench CST 117

Sample Holder Soiling Test Bench
© Fraunhofer CSP
In Fraunhofer CSP's soiling test bench samples up to 20 x 20 cm in size can be exposed to temperatures from -10 to 50°C.
Air Knife Soiling Test Bench
© Fraunhofer CSP
In standardized dusting tests with defined environmental conditions - such as an Air Knife flow velocity of up to 15 m/s above the sample - the adhesive strength of dust particles can be determined, for example.

Fraunhofer CSP has developed a method for testing the dust exposure of flat substrates with and without functional layers (ARC, ASC). In addition to a prototypical test rig, a second, further developed test rig from the company TOPAS GmbH is available.

Due to the setup and intensive use in systematic studies, Fraunhofer CSP has a wealth of experience for the controlled performance of dusting tests. Not only important environmental conditions can be mapped in a defined way, but also different standardized test dusts as well as natural dust samples can be deposited on the substrates.

In addition, Fraunhofer CSP has established various methods for quantifying dust exposure (e.g. optical spectroscopy, dark-field light microscopy, power measurement on mini PV modules) as well as the adhesive strength of dust particles (rotational force test, wind blow).

The test method developed at Fraunhofer CSP has been standardized as part of a VDI standardization process (VDI 3956-1), in which Topas GmbH also participated.