Solar Dirt

The dirt has to go
LOGO! controls fully automatic solar panel cleaning
GO! Januar 2010
A solar installation on the roof produces electricity or supports water heating. The yield is good as long as the sun
shines on the panels without resistance, i.e. while the collectors are still clean. SunBrush is a fully automatic cleaning
system that is controlled via a LOGO!.
Around 4 TWh (terawatt-hours) of electricity are generated by solar cells in Germany, and the trend is on the rise. At the same
time, around 2.7 million tons of CO2 are saved annually as a result of this. There is no scarcity of surfaces for photovoltaic
panels (electricity) and solar collectors (hot water) in Germany. A total of 2,300 km2 is available on roofs, building facades and
other locations for solar energy use. About 1.7 million photovoltaic and solar thermal systems are currently installed in
Germany.Small solar cells grouped together in large solar modules generate electric current from sunshine. The more light
shines on the modules, the more current can flow. Not only direct sunlight, but also diffuse light is converted to energy.
Photovoltaic installations operate with efficiencies of between 15 and 18 percent, while solar thermal installations achieve
efficiency factors of up to 20 percent. The energy yield of photovoltaic and solar thermal installations can drop in the course of
time, however. Usual air pollution, soot particles, pollen and other emissions from commercial and agricultural operations,
coarse soiling such as bird droppings and vegetation, etc. settle in layers on the solar modules and, to some extent,
considerably reduce the expected energy yield, in extreme cases up to 60 percent and often even one to two years after
installation. Although some of the soiling is removed by wind and rain water, these also bring new particles along with them and
so permanent layering occurs and an installation's efficiency can also drop after the second year. If coatings are burned in, the
solar modules can even be damaged to some extent. To avoid this, the panels must be cleaned regularly. There are various
possibilities of doing this, i.e. purely mechanically, by using tensides or with demineralized water, etc.
THE FULLY AUTOMATIC SOLAR BRUSH
Franz Ehleuter and Stefan Bär market photovoltaic installations from a small town in the German Unterallgäu region and are
familiar with the problems of soiling, especially caused by exhaust air from cowsheds. Due to condensation, a sticky mixture of
the animals' effusions, mixed with dust and feed components, settles directly on the panels and can only be removed by
vigorous scrubbing. This was the main incentive for developing the SunBrush, a fully automatic cleaning system.In rain or snow,
the solar roof is cleaned, cared for and, in the winter, freed from snow fully automatically and by computer control.An
experimental setup showed that it works. The cleaning system, which has now been registered as a utility model, consists of a
specially developed cleaning brush originally stemming from car wash installations which reliably brushes away firmly adhering
soiling and, in the winter, also encrusted snow. On two permanently installed rails, this cylinder runs over the roof
accommodating the solar thermal or photovoltaic panels. Fully automatic operation is controlled via a LOGO!. A rain sensor on
the roof registers the volume of rain or snow and sends pulses to the LOGO!. Depending on the previously set program, the
cleaning cylinder on the roof then starts moving after three, five or ten pulses, travels over the panels once, twice or several
times, and brushes, cleans and polishes the surfaces with rain water. Framed modules are also cleaned completely from both
directions. Moss and deposits are removed reliably.
CLEANING WITH RAIN WATER
The SunBrush uses rain water for cleaning. This is generally pure, lime-free, soft water that does not leave any residues on the
solar modules. On average, approximately 1,000 liters per square meter of rainfall in Germany are used and so no additional
pumps or cisterns are needed. Therefore, SunBrush promises one hundred percent ecological cleaning, entirely without
chemical agents. Contrary to mobile cleaning systems, this one cleans and clears any number of times and at any time. Besides
the LOGO!, the drives and the motor are also from Siemens. This is because the inventor and developer Franz Ehleuter is
convinced of the quality and service and would also like to pass these on to his end customers.The SunBrush can also be
installed easily on existing roof-mounted solar installations. The system is also to be marketed in larger volumes as from the
middle of the year.
Be it rain or snow – SunBrush moves fully automatically over the roof
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