Desert Applications of PV Modules Jan Herrmann, Timo Lorenz, Karolina Slamova, Elisabeth Klimm, Michael Koehl, and Karl-Anders Weiss Fraunhofer Institute for Solar Energy Systems, Heidenhofstr. 2, Freiburg, 79110 Germany Abstract — Desert areas are very interesting for PV application, due to their high global irradiance. These arid regions bear extreme conditions for PV modules. Strong winds and high dust loads cause not only temporary decreases in transmittance but also a non-reversible degradation of the surface, which limits the overall yield. The question is how to show where to place PV modules to maximize the service life and the electrical yield during the module’s life time. Stress maps can help to evaluate promising locations and model the soiling potential, which strongly depend on environmental factors such as rain and dust storms. The overall dust deposition is important for an economic feasibility analysis by which the expected energy yield loss in terms of different soiling scenarios can be determined. A correlation between dust deposition and transmittance links the stress map data with the actual expected power output. Therefore a dust deposition setup has been developed. Index Terms — climate, desert, dust deposition, economic analysis, soiling. I. INTRODUCTION The actual efficiency of solar systems is influenced by various factors. Besides global irradiance and technical characteristics, the local environmental conditions are crucial for the reliability and resulting power output. In this respect, the deposition of airborne particles on the glazing of PV modules has to be considered as an important aspect [1]. Soiling, as the accumulation of dust and other inorganic and organic particles on surfaces is commonly named, causes a reversible optical loss and reduced transmittance of the glazing. Several empirical studies investigated this phenomenon by correlating the time of exposure or the amount of dust on glazing materials with the measured performance of solar PV modules [2, 3]. All studies report a reduction in efficiency with increasing soiling rates. In some cases efficiency losses of 30 % and more are found [4]. However, extreme events like a nearby construction site can increase this value significantly [5]. Thus, soiling is a potential key factor for the economic feasibility of larger solar energy plants in particular [6]. In addition to the accumulation of particles on the glazing, longer periods of exposure in demanding conditions can also cause an irreversible degradation of components by abrasion. II. MAPPING SOILING IN ARID REGIONS Arid and semi-arid areas cover a big part of the earth’s surface. They are mostly located around the tropics about 23° north and south of the equator (Fig. 1). Fig. 1. Arid and semi-arid regions according to the Köppen-Geiger climate classification. The red color shows the MENA region, with high solar potential. According to the commonly used Köppen-Geiger climate classification these areas are defined by limited precipitation and high potential evaporation rates. The climatic conditions especially of the hot deserts seem to provide the best conditions for the effective use of solar power. High rates of solar irradiation throughout the year promise high energy yields (Fig. 2). Fig. 2. Average yearly Global Horizontal Radiation (based on NASA SSE dataset). But high amounts of available mineral dust and frequent dust events induce heavy soiling rates and therefore the advantages of this area could be reduced considerably. Special coatings, designed to reduce the accumulation of dust on the glazing, have to be adapted to these particular conditions. Beyond the economic view, the necessary cleaning processes consume serious amounts of water. Considering the deficit of this resource in arid regions, soiling potentially reduces the sustainability of solar power usage drastically. Therefore, a better understanding of the complex soiling processes in