Outdoor soiling microscope for measuring particle deposition and resuspension

Figgis, Benjamin; Ennaoui, A.; Guo, Bing; Javed, Wasim; Chen, Eugene

doi:10.1016/j.solener.2016.08.015

Cited by 83 publications

(36 citation statements)

References 12 publications

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“…5-7 suggest that we can estimate the transmittance of a PV cover glass from the measured fractional area coverage of deposited particles, and we can also estimate the impact of the spectral characteristics due to soiling from the size distribution and the cleanliness value, L. This relationship can find immediate application in monitoring PV soiling and estimating its effect on PV performance. Outdoor microscopes have already been employed to measure particle size and deposition rates related to soiling 42 , and could be used for the optical characterization of natural soiling of PV modules suggested by our work. The results augment and extend those of other studies made at lower soiling (i.e., lower f values) 43,44 .…”

Section: Resultsmentioning

confidence: 99%

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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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Section: Resultsmentioning

confidence: 99%

“…Glass coupons are a standard method for the analysis of soiling of photovoltaics and have been used in a number of research papers 11,39,41,42,[47][48][49][50][51] . In addition, recently launched low-maintenance soiling detectors quantify the loss of PV modules through the optical analysis of the contamination accumulated on glass 52,53 .…”

Section: Discussionmentioning

confidence: 99%

Modelling photovoltaic soiling losses through optical characterization

Smestad

Germer

Alrashidi

et al. 2020

Sci Rep

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“…A pair of outdoor soiling microscopes (OSMs) was installed ( Figure 2). Details of the OSM apparatus and image-analysis technique have been previously described (Figgis et al 2016).…”

Section: Experiments and Methodsmentioning

confidence: 99%

“…On the other hand, it is difficult for field studies to isolate the effects of meteo parameters on particle motions, because dust-collection periods typically last for days or weeks whereas the weather of course varies continuously. In order to address this constraint of field studies, some of us previously developed an "outdoor soiling microscope" (OSM) able to measure deposition and detachment of dust particles larger than »4 mm every 10 min, day and night, in the field (Figgis et al 2016).…”

Section: Introductionmentioning

confidence: 99%

Dominant environmental parameters for dust deposition and resuspension in desert climates

Figgis

Guo

Javed

et al. 2018

Aerosol Science and Technology

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Field studies of dry deposition usually measure dust accumulation over periods of days or weeks. However, long measurement periods obscure the effects of meteorological conditions on the deposition rate. Previously we developed an "outdoor soiling microscope" (OSM) in order to measure dust deposition and detachment every 10 min in the field. In this study a greased/ ungreased pair of OSMs was deployed for 51 days in the desert climate of Doha, Qatar. Stepwise regression analysis was performed to quantify the explanatory power of meteorological parameters on dust deposition and detachment rates. It was found that wind speed dominated deposition and rebound of dust particles, and produced a distinctive "threshold" response in deposition. The dry deposition results were highly consistent with a model by Kim et al. (2000) derived from outdoor experiments. By comparison, relative humidity and particulate matter concentration had less influence on dust flux rates.

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“…Moreover, soiling is not only a local [5], but also a seasonal phenomenon and for that reason, if operational costs are to be reduced, a proper characterization of it is needed. This has been done extensively in the literature, but mostly focused on desert regions [6][7][8], which have high irradiance values and significant problems with dust deposition, namely mineral and not organic.…”

Section: Introductionmentioning

confidence: 99%

Organic Soiling: The Role of Pollen in PV Module Performance Degradation

et al. 2018

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Soiling is a problem for solar energy harvesting technologies, such as in photovoltaic modules technologies. This paper describes not only one complete year of Soiling Ratioindex and rates measured in a rural environment of Southern Europe, but also focuses on the seasonal variation of the type of soiling, mainly spring and summer. The Soiling Ratio index is calculated based on the maximum power output and short circuit current of two photovoltaic (PV) panels, along with Scanning Electron Microscopy and Energy Dispersive X-Ray of glass samples to provide visual and chemical inspection of the type of soiling. Mass accumulation on glass samples mounted on a "glass tree" was weekly measured with a microbalance and related with the Soiling Ratio metrics. Soiling rates were calculated to infer the degree of soiling for each season and the respective comparison made. Results show a soiling rate of 4.1%/month in April (spring), 1.9%/month in July (summer) and 1.6%/month in September (fall). Rain (the main natural cleaning agent of the photovoltaic modules) as well as aerosol optical depth (proxy for atmospheric particle concentration) were correlated with the Soiling Ratio. In-depth analysis on the type of organic soiling was performed.

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Outdoor soiling microscope for measuring particle deposition and resuspension

Cited by 83 publications

References 12 publications

Modelling photovoltaic soiling losses through optical characterization

Modelling photovoltaic soiling losses through optical characterization

Dominant environmental parameters for dust deposition and resuspension in desert climates

Organic Soiling: The Role of Pollen in PV Module Performance Degradation

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