Performance of Soiled PV Module Technologies: Behavior Based on Controverted Parameters

The choice of a particular PV technology for a best performance is sometimes based upon a single observation or single operating condition. However, many parameters for electrooptical have opposing or counterintuitive functionalities, such as metals possessing high-optical transparencies. In this paper, the choice of appropriate PV technologies for moderate- to harsh-climate conditions is explored based upon controverted parameters of spectral effects and temperature. Specifically, a higher bandgap PV technology (a-Si:H or CdTe) may be higher-temperature choices over lower bandgap candidates (e.g., Si or Cu(In,Ga)Se2). But opposing (or counterintuitive to) this temperature parameter is the spectral effects of the available light. It is reported that soiling or dust tends to absorb more of the lower wavelength light, such that CdTe or a-Si:H would be disadvantaged as the technology for geographical regions where particulate accumulation of module surfaces is a concern. This paper examines these two counterintuitive properties (spectral effects due to soiling of the module surface and module temperature) to identify regions of "best-of-class" performance for these four common technologies (crystalline Si, CIGS, CdTe, and a-Si:H). The spectral effects of dust coatings are characterized for the chemistry/composition of sample collected from module surfaces from several geographical locations. Simple modeling is used based upon actual soiling ratios and soiling rates for various geographical regions and the temperature characteristics of these module technologies to evaluate specific performances.