A unified global investigation on the spectral effects of soiling losses of PV glass substrates: preliminary results

Micheli, Leonardo; Fernández, Eduardo F.; Smestad, Greg P.; Alrashidi, Hameed; Sarmah, Nabin; Sellami, Nazmi; Hassan, Ibrahim A. I.; Kasry, Amal; Nofuentes, G.; Sood, Neeru; Pesala, Bala; Almonacid, Florencia; Reddy, K.S.; Muller, Matthew; Mallick, Tapas K.

doi:10.1109/pvsc.2017.8366317

Cited by 14 publications

(22 citation statements)

References 7 publications

(7 reference statements)

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“…This is not surprising because the UV region contributes little to the current generation in PV modules because it represents only a limited portion of the solar irradiance spectrum. Moreover, all the PV technologies have low spectral response in this region ( Figure 5), whereas soiling causes dramatic transmittance drops [2,3]. The best result for the UV is found for a-Si because this is the technology with the highest absorption at the lowest wavelengths ( Figure 5).…”

Section: Analysis Of Spectral Wavebandmentioning

confidence: 99%

“…This paper considers only the hemispherical transmittance of soiling. Even if less affected by soiling than the direct component [3], the hemispherical transmittance has been preferred because it is more representative of the actual effect of soiling on power conversion. Photovoltaic modules, indeed, can convert both the direct and diffuse components of the light, as well as the part that is scattered by soiling.…”

Section: Data Collectionmentioning

confidence: 99%

“…It is important to highlight that, along with the broadband reduction in irradiance, soiling also changes the spectrum of the transmitted light, causing larger transmittance drops in the blue region, meaning that PV technologies with different bandgaps can be differently affected by soiling [2][3][4][5]. Hence, measuring and analyzing soiling should not disregard the spectral effects that soiling can have on various PV technologies; but determining the spectral component of soiling on fielded PV modules is still challenging.…”

Section: Introductionmentioning

confidence: 99%

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Correlating photovoltaic soiling losses to waveband and single-value transmittance measurements

Micheli

Caballero

Férnández

et al. 2019

Energy

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This paper presents the results of an investigation on the spectral losses of photovoltaic (PV) soiling. The transmittance of a glass coupon exposed to natural soiling outdoors in Jaén, southern Spain, has been measured weekly and used to estimate the soiling losses that various types of photovoltaic materials would experience if installed in the same location. The results suggest that measuring the hemispherical transmittance of the soiling accumulated on a PV glass coupon can give enough information to quantify the impact of soiling on energy production. Each PV technology is found to have a preferred spectral region, or a specific single wavelength, for which the transmittance through a PV glass coupon could be used for the best estimation of soiling losses. Overall, considering the average spectral transmittance between the extreme wavelengths of the material-specific absorption band, or the transmittance of soiling at a single wavelength between 500 and 600 nm yields the best estimations for different PV technologies. The results of this work can lead to innovative approaches to detect soiling in the field and to estimate the impact of spectral changes induced by soiling on PV energy production.

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Section: Analysis Of Spectral Wavebandmentioning

confidence: 99%

Section: Data Collectionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Correlating photovoltaic soiling losses to waveband and single-value transmittance measurements

Micheli

Caballero

Férnández

et al. 2019

Energy

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“…These places were chosen to represent a wide variety of climates and environmental conditions (See the locations listed in Supplementary Information) [21][22][23][24] . Identical low-iron glass coupons were soiled at each location over an 8-week period between January and March 2016 25 . The samples were mounted horizontally (i.e., without a tilt).…”

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confidence: 99%

Modelling photovoltaic soiling losses through optical characterization

Smestad

Germer

Alrashidi

et al. 2020

Sci Rep

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The accumulation of soiling on photovoltaic (PV) modules affects PV systems worldwide. Soiling consists of mineral dust, soot particles, aerosols, pollen, fungi and/or other contaminants that deposit on the surface of PV modules. Soiling absorbs, scatters, and reflects a fraction of the incoming sunlight, reducing the intensity that reaches the active part of the solar cell. Here, we report on the comparison of naturally accumulated soiling on coupons of PV glass soiled at seven locations worldwide. The spectral hemispherical transmittance was measured. It was found that natural soiling disproportionately impacts the blue and ultraviolet (UV) portions of the spectrum compared to the visible and infrared (iR). Also, the general shape of the transmittance spectra was similar at all the studied sites and could adequately be described by a modified form of the Ångström turbidity equation. In addition, the distribution of particles sizes was found to follow the IEST-STD-CC 1246E cleanliness standard. The fractional coverage of the glass surface by particles could be determined directly or indirectly and, as expected, has a linear correlation with the transmittance. It thus becomes feasible to estimate the optical consequences of the soiling of pV modules from the particle size distribution and the cleanliness value. Soiling has a negative impact on the economic revenues of PV installations, not only because it reduces the amount of energy converted by the PV modules, but also because it introduces additional operating and maintenance costs and, at the same time, increases the uncertainty on the estimation of PV performance, leading to both higher financial risks and interest rates charged to plant developers. Power reductions greater than 50% have been reported in the literature because of soiling 1,2 ; it has been estimated that an average loss of 4% on the global annual energy yield of PV could cause losses in revenue on the order of 2 × 10 9 US$ annually 3. A careful monitoring of soiling is required to mitigate its effect 4. Soiling losses are generally quantified by using soiling stations. These systems are made of at least two PV devices, one of which is regularly cleaned while the other is left to soil naturally. By comparing the ratio of the electrical outputs of the two devices, it is possible to estimate the impact of soiling on the PV performance 5,6. The International Electrotechnical Commission's (IEC) metric to monitor and quantify the impact of soiling on PV modules is the soiling ratio, r s , which expresses the ratio of the electrical output of a soiled PV device to the output of the same device under clean conditions 7. Like the transmittance, a higher soiling ratio translates to less soiling deposited on the modules. A value of 1 indicates clean conditions, with no soiling. For a more detailed definition of r s , please refer to the Methodology section. The fractional loss of solar-generated power due to soiling is 1 − r s .

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“…It is important to mention that this error is expected to grow as the broadband (average) transmittance loss increases. This expectation is due to the fact that, as shown in previous works [3,4,14], the difference between losses at short and long wavelengths tends to increase with the severity of soiling (from low to high soiling conditions).…”

Section: Background and Motivationmentioning

confidence: 66%

Selection of optimal wavelengths for optical soiling modelling and detection in photovoltaic modules

Micheli

Fernández

Muller

et al. 2020

Solar Energy Materials and Solar Cells

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Nomenclature Symbols Abbreviations EG(λ, ) spectral solar irradiance in the plane of the PV modules [W/m 2 / µm] APE Average Photon Energy [eV] Fig. 2. Soiling losses recorded for Measurement A (shown in Fig. 1, with an average transmittance loss 2.7%) for m-Si and a-Si cells under red-rich or blue-rich irradiance conditions. Each plot shows the spectral response (left axis), the irradiance and the generated current (right axis) for a different combination of irradiance and PV material. The shaded area is the integral in the numerator of Eq. (2).

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A unified global investigation on the spectral effects of soiling losses of PV glass substrates: preliminary results

Cited by 14 publications

References 7 publications

Correlating photovoltaic soiling losses to waveband and single-value transmittance measurements

Correlating photovoltaic soiling losses to waveband and single-value transmittance measurements

Modelling photovoltaic soiling losses through optical characterization

Selection of optimal wavelengths for optical soiling modelling and detection in photovoltaic modules

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