The Experts below are selected from a list of 2823 Experts worldwide ranked by ideXlab platform
Paul Berdahl - One of the best experts on this subject based on the ideXlab platform.
-
methods and instrumentation to measure the effective Solar Reflectance of fluorescent cool surfaces
Energy and Buildings, 2017Co-Authors: Ronnen Levinson, Paul Berdahl, Chiara Ferrari, Sharon Chen, J SlackAbstract:Abstract Fluorescent cool dark surfaces stay cool in the sun by reflecting near-infrared (NIR) radiation and by actively re-emitting in the NIR spectrum some of the energy absorbed from visible sunlight. The fraction of incident Solar energy rejected by reflection and fluorescence is the “effective Solar Reflectance”, or ESR, of the surface. It is challenging to measure ESR with a Solar spectrometer or a Solar reflectometer, the radiometric instruments most commonly used to measure the Solar Reflectance (SR) of specimens in the laboratory. We have tested a variety of calorimetric techniques for using temperature in the sun to interpolate the effective Solar absorptance (1 − ESR) of a fluorescent test specimen from the known Solar absorptances of non-fluorescent reference specimens. Our experiments show that averaging out noise in the temperature signal induced by variations in convection is key. We developed a computer-controlled rotary apparatus that compares the temperatures in the sun of up to six specimens. Trials on six different fluorescent specimens indicate that it can measure ESR with a repeatability of about 0.02. To maximize the ratio of signal to noise in temperature determination, and to facilitate calculation of the fluorescence benefit (ESR − SR), measurements should be performed with specimens facing the sun.
-
soiling of building envelope surfaces and its effect on Solar Reflectance part iii interlaboratory study of an accelerated aging method for roofing materials
Solar Energy Materials and Solar Cells, 2015Co-Authors: Paul Berdahl, Mohamad Sleiman, Thomas W. Kirchstetter, Sharon Chen, Haley Gilbert, Erica Bibian, Laura S Bruckman, Dominic CremonaAbstract:Abstract A laboratory method to simulate natural exposure of roofing materials has been reported in a companion article. In the current article, we describe the results of an international, nine-participant interlaboratory study (ILS) conducted in accordance with ASTM Standard E691-09 to establish the precision and reproducibility of this protocol. The accelerated soiling and weathering method was applied four times by each laboratory to replicate coupons of 12 products representing a wide variety of roofing categories (single-ply membrane, factory-applied coating (on metal), bare metal, field-applied coating, asphalt shingle, modified-bitumen cap sheet, clay tile, and concrete tile). Participants reported initial and laboratory-aged values of Solar Reflectance and thermal emittance. Measured Solar Reflectances were consistent within and across eight of the nine participating laboratories. Measured thermal emittances reported by six participants exhibited comparable consistency. For Solar Reflectance, the accelerated aging method is both repeatable and reproducible within an acceptable range of standard deviations: the repeatability standard deviation sr ranged from 0.008 to 0.015 (relative standard deviation of 1.2–2.1%) and the reproducibility standard deviation sR ranged from 0.022 to 0.036 (relative standard deviation of 3.2–5.8%). The ILS confirmed that the accelerated aging method can be reproduced by multiple independent laboratories with acceptable precision. This study supports the adoption of the accelerated aging practice to speed the evaluation and performance rating of new cool roofing materials.
-
Soiling of building envelope surfaces and its effect on Solar Reflectance - Part III: Inter laboratory study of an accelerated aging method for roofing materials.
Solar Energy Materials and Solar Cells, 2015Co-Authors: Mohamad Sleiman, Paul Berdahl, Haley E. Gilbert, Thomas W. Kirchstetter, Sharon Chen, Erica Bibian, Laura S Bruckman, Dominic Cremona, Roger H. French, Devin A. GordonAbstract:A laboratory method to simulate natural exposure of roofing materials has been reported in a companion article. In the current article, we describe the results of an international, nine-participant interlaboratory study (ILS) conducted in accordance with ASTM Standard E691-09 to establish the precision and reproducibility of this protocol. The accelerated soiling and weathering method was applied four times by each laboratory to replicate coupons of 12 products representing a wide variety of roofing categories (single-ply membrane, factory-applied coating (on metal), bare metal, field-applied coating, asphalt shingle, modified-bitumen cap sheet, clay tile, and concrete tile). Participants reported initial and laboratory-aged values of Solar Reflectance and thermal emittance. Measured Solar Reflectances were consistent within and across eight of the nine participating laboratories. Measured thermal emittances reported by six participants exhibited comparable consistency. For Solar Reflectance, the accelerated aging method is both repeatable and reproducible within an acceptable range of standard deviations: the repeatability standard deviation sr ranged from 0.008 to 0.015 (relative standard deviation of 1.2–2.1%) and the reproducibility standard deviation sR ranged from 0.022 to 0.036 (relative standard deviation of 3.2–5.8%). The ILS confirmed that the accelerated aging method can be reproduced by multiple independent laboratories with acceptable precision. This study supports the adoption of the accelerated aging practice to speed the evaluation and performance rating of new cool roofing materials.
-
soiling of building envelope surfaces and its effect on Solar Reflectance part ii development of an accelerated aging method for roofing materials
Solar Energy Materials and Solar Cells, 2014Co-Authors: Mohamad Sleiman, Paul Berdahl, Thomas W. Kirchstetter, Haley Gilbert, Sarah Quelen, Lea Marlot, Chelsea V Preble, Sharon ChenAbstract:Abstract Highly reflective roofs can decrease the energy required for building air conditioning, help mitigate the urban heat island effect, and slow global warming. However, these benefits are diminished by soiling and weathering processes that reduce the Solar Reflectance of most roofing materials. Soiling results from the deposition of atmospheric particulate matter and the growth of microorganisms, each of which absorb sunlight. Weathering of materials occurs with exposure to water, sunlight, and high temperatures. This study developed an accelerated aging method that incorporates features of soiling and weathering. The method sprays a calibrated aqueous soiling mixture of dust minerals, black carbon, humic acid, and salts onto preconditioned coupons of roofing materials, then subjects the soiled coupons to cycles of ultraviolet radiation, heat and water in a commercial weatherometer. Three soiling mixtures were optimized to reproduce the site-specific Solar spectral Reflectance features of roofing products exposed for 3 years in a hot and humid climate (Miami, Florida); a hot and dry climate (Phoenix, Arizona); and a polluted atmosphere in a temperate climate (Cleveland, Ohio). A fourth mixture was designed to reproduce the three-site average values of Solar Reflectance and thermal emittance attained after 3 years of natural exposure, which the Cool Roof Rating Council (CRRC) uses to rate roofing products sold in the US. This accelerated aging method was applied to 25 products–single ply membranes, factory and field applied coatings, tiles, modified bitumen cap sheets, and asphalt shingles–and reproduced in 3 days the CRRC's 3-year aged values of Solar Reflectance. This accelerated aging method can be used to speed the evaluation and rating of new cool roofing materials.
-
Soiling of building envelope surfaces and its effect on Solar Reflectance – Part II: Development of an accelerated aging method for roofing materials
Solar Energy Materials and Solar Cells, 2014Co-Authors: Mohamad Sleiman, Paul Berdahl, Thomas W. Kirchstetter, Sharon Chen, Haley Gilbert, Sarah Quelen, Lea Marlot, Chelsea V Preble, Amandine Montalbano, Olivier RosselerAbstract:Abstract Highly reflective roofs can decrease the energy required for building air conditioning, help mitigate the urban heat island effect, and slow global warming. However, these benefits are diminished by soiling and weathering processes that reduce the Solar Reflectance of most roofing materials. Soiling results from the deposition of atmospheric particulate matter and the growth of microorganisms, each of which absorb sunlight. Weathering of materials occurs with exposure to water, sunlight, and high temperatures. This study developed an accelerated aging method that incorporates features of soiling and weathering. The method sprays a calibrated aqueous soiling mixture of dust minerals, black carbon, humic acid, and salts onto preconditioned coupons of roofing materials, then subjects the soiled coupons to cycles of ultraviolet radiation, heat and water in a commercial weatherometer. Three soiling mixtures were optimized to reproduce the site-specific Solar spectral Reflectance features of roofing products exposed for 3 years in a hot and humid climate (Miami, Florida); a hot and dry climate (Phoenix, Arizona); and a polluted atmosphere in a temperate climate (Cleveland, Ohio). A fourth mixture was designed to reproduce the three-site average values of Solar Reflectance and thermal emittance attained after 3 years of natural exposure, which the Cool Roof Rating Council (CRRC) uses to rate roofing products sold in the US. This accelerated aging method was applied to 25 products–single ply membranes, factory and field applied coatings, tiles, modified bitumen cap sheets, and asphalt shingles–and reproduced in 3 days the CRRC's 3-year aged values of Solar Reflectance. This accelerated aging method can be used to speed the evaluation and rating of new cool roofing materials.
M L P Reddy - One of the best experts on this subject based on the ideXlab platform.
-
YIn0.9Mn0.1O3-ZnO nano-pigment exhibiting intense blue color with impressive Solar Reflectance
Dyes and Pigments, 2016Co-Authors: Sheethu Jose, Anaswara Jayaprakash, Sourav Laha, K.g. Nishanth, S. Natarajan, M L P ReddyAbstract:The current study reports on the synthesis and characterization of a new inorganic nano-pigment with an intense blue color and high Solar radiation reflective properties (70%). The nano-pigment YIn0.9Mn0.1O3-ZnO was synthesized by a sol-gel combustion method and characterized with the aid of X-Ray diffraction, Raman spectroscopy, Magnetic susceptibility, Transmission electron microscopy, UV ndash;vis-NIR diffuse Reflectance spectroscopy and CIE-1976 L∗a∗b∗ color measurements. The Rietveld refinement of the XRD patterns of the developed nano-pigment disclosed the existence of YIn0.9Mn0.1O3and ZnO in a 1:1 ratio with hexagonal crystal structures. For comparison, YIn0.9Mn0.1O3was also synthesized by the sol-gel combustion route and its optical properties compared with that of YIn0.9Mn0.1O3-ZnO. It is interesting to note that the developed YIn0.9Mn0.1O3-ZnO nano-pigment exhibits superior blue hue (b∗ = -40.55) and Solar Reflectance (R∗ = 70%) values as compared to the YIn0.9Mn0.1O3nano-pigment (b∗ = -22.28, R∗ = 50%). Most importantly, the potential utility of the nano-pigment as a "Cool Pigment" was demonstrated by coating onto roofing materials like aluminum roofing sheets.
-
yin0 9mn0 1o3 zno nano pigment exhibiting intense blue color with impressive Solar Reflectance
Dyes and Pigments, 2016Co-Authors: Sheethu Jose, Anaswara Jayaprakash, Sourav Laha, M L P Reddy, K.g. Nishanth, S. NatarajanAbstract:The current study reports on the synthesis and characterization of a new inorganic nano-pigment with an intense blue color and high Solar radiation reflective properties (70%). The nano-pigment YIn0.9Mn0.1O3-ZnO was synthesized by a sol-gel combustion method and characterized with the aid of X-Ray diffraction, Raman spectroscopy, Magnetic susceptibility, Transmission electron microscopy, UV ndash;vis-NIR diffuse Reflectance spectroscopy and CIE-1976 L*a*b* color measurements. The Rietveld refinement of the XRD patterns of the developed nano-pigment disclosed the existence of YIn0.9Mn0.1O3 and ZnO in a 1:1 ratio with hexagonal crystal structures. For comparison, YIn0.9Mn0.1O3 was also synthesized by the sol gel combustion route and its optical properties compared with that of YIn0.9Mn0.1O3-ZnO. It is interesting to note that the developed YIn0.9Mn0.1O3-ZnO nano-pigmeht exhibits superior blue hue (b* = -40.55) and Solar Reflectance (R* = 70%) values as compared to the YIn0.9Mn0.1O3 nano-pigment (b* = -22.28, R* = 50%). Most importantly, the potential utility of the nano-pigment as a ``Cool Pigment'' was demonstrated by coating onto roofing materials like aluminum roofing sheets. (C) 2015 Elsevier Ltd. All rights reserved.
-
YIn0.9Mn0.1O3–ZnO nano-pigment exhibiting intense blue color with impressive Solar Reflectance
Dyes and Pigments, 2015Co-Authors: Sheethu Jose, Anaswara Jayaprakash, Sourav Laha, K.g. Nishanth, S. Natarajan, M L P ReddyAbstract:The current study reports on the synthesis and characterization of a new inorganic nano-pigment with an intense blue color and high Solar radiation reflective properties (70%). The nano-pigment YIn0.9Mn0.1O3-ZnO was synthesized by a sol-gel combustion method and characterized with the aid of X-Ray diffraction, Raman spectroscopy, Magnetic susceptibility, Transmission electron microscopy, UV ndash;vis-NIR diffuse Reflectance spectroscopy and CIE-1976 L*a*b* color measurements. The Rietveld refinement of the XRD patterns of the developed nano-pigment disclosed the existence of YIn0.9Mn0.1O3 and ZnO in a 1:1 ratio with hexagonal crystal structures. For comparison, YIn0.9Mn0.1O3 was also synthesized by the sol gel combustion route and its optical properties compared with that of YIn0.9Mn0.1O3-ZnO. It is interesting to note that the developed YIn0.9Mn0.1O3-ZnO nano-pigmeht exhibits superior blue hue (b* = -40.55) and Solar Reflectance (R* = 70%) values as compared to the YIn0.9Mn0.1O3 nano-pigment (b* = -22.28, R* = 50%). Most importantly, the potential utility of the nano-pigment as a ``Cool Pigment'' was demonstrated by coating onto roofing materials like aluminum roofing sheets. (C) 2015 Elsevier Ltd. All rights reserved.
Ronnen Levinson - One of the best experts on this subject based on the ideXlab platform.
-
methods and instrumentation to measure the effective Solar Reflectance of fluorescent cool surfaces
Energy and Buildings, 2017Co-Authors: Ronnen Levinson, Paul Berdahl, Chiara Ferrari, Sharon Chen, J SlackAbstract:Abstract Fluorescent cool dark surfaces stay cool in the sun by reflecting near-infrared (NIR) radiation and by actively re-emitting in the NIR spectrum some of the energy absorbed from visible sunlight. The fraction of incident Solar energy rejected by reflection and fluorescence is the “effective Solar Reflectance”, or ESR, of the surface. It is challenging to measure ESR with a Solar spectrometer or a Solar reflectometer, the radiometric instruments most commonly used to measure the Solar Reflectance (SR) of specimens in the laboratory. We have tested a variety of calorimetric techniques for using temperature in the sun to interpolate the effective Solar absorptance (1 − ESR) of a fluorescent test specimen from the known Solar absorptances of non-fluorescent reference specimens. Our experiments show that averaging out noise in the temperature signal induced by variations in convection is key. We developed a computer-controlled rotary apparatus that compares the temperatures in the sun of up to six specimens. Trials on six different fluorescent specimens indicate that it can measure ESR with a repeatability of about 0.02. To maximize the ratio of signal to noise in temperature determination, and to facilitate calculation of the fluorescence benefit (ESR − SR), measurements should be performed with specimens facing the sun.
-
three year weathering tests on asphalt shingles Solar Reflectance
Solar Energy Materials and Solar Cells, 2012Co-Authors: Paul Berdahl, Ronnen Levinson, Hashem Akbari, Jeffry L Jacobs, Frank W Klink, Rebecca L EvermanAbstract:Exposed asphalt shingles undergo chemical and physical changes as they weather. Here we focus on the resulting changes in Solar Reflectance. Most roofing granules employing inorganic metal oxide pigments are very stable. Initial Reflectance changes are therefore due to changes in the asphalt itself, and the loss of processing oils coating the granules. Ultraviolet-induced photo-oxidation of these oils and exposed asphalt produces dark hydrophilic substances that are removed by rain, or in dry climates, transported by dew. After six months, changes in Solar Reflectance are small and (in California) mainly due an annual cycle of accumulation of atmospheric dust and its removal by rain. In hot humid climates cyanobacteria grow rapidly on granule surfaces, creating dark stains that reduce Reflectance by as much as 0.06 at 3 years. We show that in these types of climates (exemplified by Houston) biocide additives such as Cu2O can be employed to maintain Solar Reflectance. When cyanobacteria are absent, Solar Reflectance changes over the first three years are on the order of 0.02 or less, and may be either positive or negative.
-
Soiling of building envelope surfaces and its effect on Solar Reflectance. Part I: Analysis of roofing product databases
Solar Energy Materials and Solar Cells, 2011Co-Authors: Mohamad Sleiman, Paul Berdahl, George Ban-weiss, Haley E. Gilbert, David François, Thomas W. Kirchstetter, Hugo Destaillats, Ronnen LevinsonAbstract:The use of highly reflective “cool” roofing materials can decrease demand for air conditioning, mitigate the urban heat island effect, and potentially slow global warming. However, initially high roof Solar Reflectance can be degraded by natural soiling and weathering processes. We evaluated Solar Reflectance losses after three years of natural exposure reported in two separate databases: the Rated Products Directory of the US Cool Roof Rating Council (CRRC) and information reported by manufacturers to the US Environmental Protection Agency (EPA)'s ENERGY STAR® rating program. Many product ratings were culled because they were duplicative (within a database) or not measured. A second, site-resolved version of the CRRC dataset was created by transcribing from paper records the site-specific measurements of aged Solar Reflectance in Florida, Arizona and Ohio. Products with high initial Solar Reflectance tended to lose Reflectance, while those with very low initial Solar Reflectance tended to become more reflective as they aged. Within the site-resolved CRRC database, absolute Solar Reflectance losses for samples of medium-to-high initial Solar Reflectance were 2–3 times greater in Florida (hot and humid) than in Arizona (hot and dry); losses in Ohio (temperate but polluted) were intermediate. Disaggregating results by product type—factory-applied coating, field-applied coating, metal, modified bitumen, shingle, single-ply membrane and tile—revealed that absolute Solar Reflectance losses were largest for field-applied coating, modified bitumen and single-ply membrane products, and smallest for factory-applied coating and metal products. The 2008 Title 24 provisional aged Solar Reflectance formula overpredicts the measured aged Solar Reflectance of 0–30% of each product type in the culled public CRRC database. The rate of overprediction was greatest for field-applied coating and single-ply membrane products and least for factory-applied coating, shingle, and metal products. New product-specific formulas of the form ρa′=0.20+β(ρi−0.20) can be used to estimate provisional aged Solar Reflectance ρa′ from initial Solar Reflectance ρi pending measurement of aged Solar Reflectance. The appropriate value of soiling resistance β varies by product type and is selected to attain some desired overprediction rate for the formula. The correlations for shingle products presented in this paper should not be used to predict aged Solar Reflectance or estimate provisional aged Solar Reflectance because the data set is too small and too limited in range of initial Solar Reflectance.
-
measuring Solar Reflectance part ii review of practical methods
Solar Energy, 2010Co-Authors: Ronnen Levinson, Hashem Akbari, Paul BerdahlAbstract:Abstract A companion article explored how Solar Reflectance varies with surface orientation and Solar position, and found that clear sky air mass 1 global horizontal (AM1GH) Solar Reflectance is a preferred quantity for estimating Solar heat gain. In this study we show that AM1GH Solar Reflectance Rg,0 can be accurately measured with a pyranometer, a Solar spectrophotometer, or an updated edition of the Solar Spectrum Reflectometer (version 6). Of primary concern are errors that result from variations in the spectral and angular distributions of incident sunlight. Neglecting shadow, background and instrument errors, the conventional pyranometer technique can measure Rg,0 to within 0.01 for surface slopes up to 5:12 [23°], and to within 0.02 for surface slopes up to 12:12 [45°]. An alternative pyranometer method minimizes shadow errors and can be used to measure Rg,0 of a surface as small as 1 m in diameter. The accuracy with which it can measure Rg,0 is otherwise comparable to that of the conventional pyranometer technique. A Solar spectrophotometer can be used to determine R g,0 ∗ , a Solar Reflectance computed by averaging Solar spectral Reflectance weighted with AM1GH Solar spectral irradiance. Neglecting instrument errors, R g,0 ∗ matches Rg,0 to within 0.006. The air mass 1.5 Solar Reflectance measured with version 5 of the Solar Spectrum Reflectometer can differ from R g,0 ∗ by as much as 0.08, but the AM1GH output of version 6 of this instrument matches R g,0 ∗ to within about 0.01.
-
Measuring Solar Reflectance—Part II: Review of practical methods
Solar Energy, 2010Co-Authors: Ronnen Levinson, Hashem Akbari, Paul BerdahlAbstract:Abstract A companion article explored how Solar Reflectance varies with surface orientation and Solar position, and found that clear sky air mass 1 global horizontal (AM1GH) Solar Reflectance is a preferred quantity for estimating Solar heat gain. In this study we show that AM1GH Solar Reflectance Rg,0 can be accurately measured with a pyranometer, a Solar spectrophotometer, or an updated edition of the Solar Spectrum Reflectometer (version 6). Of primary concern are errors that result from variations in the spectral and angular distributions of incident sunlight. Neglecting shadow, background and instrument errors, the conventional pyranometer technique can measure Rg,0 to within 0.01 for surface slopes up to 5:12 [23°], and to within 0.02 for surface slopes up to 12:12 [45°]. An alternative pyranometer method minimizes shadow errors and can be used to measure Rg,0 of a surface as small as 1 m in diameter. The accuracy with which it can measure Rg,0 is otherwise comparable to that of the conventional pyranometer technique. A Solar spectrophotometer can be used to determine R g,0 ∗ , a Solar Reflectance computed by averaging Solar spectral Reflectance weighted with AM1GH Solar spectral irradiance. Neglecting instrument errors, R g,0 ∗ matches Rg,0 to within 0.006. The air mass 1.5 Solar Reflectance measured with version 5 of the Solar Spectrum Reflectometer can differ from R g,0 ∗ by as much as 0.08, but the AM1GH output of version 6 of this instrument matches R g,0 ∗ to within about 0.01.
Sheethu Jose - One of the best experts on this subject based on the ideXlab platform.
-
YIn0.9Mn0.1O3-ZnO nano-pigment exhibiting intense blue color with impressive Solar Reflectance
Dyes and Pigments, 2016Co-Authors: Sheethu Jose, Anaswara Jayaprakash, Sourav Laha, K.g. Nishanth, S. Natarajan, M L P ReddyAbstract:The current study reports on the synthesis and characterization of a new inorganic nano-pigment with an intense blue color and high Solar radiation reflective properties (70%). The nano-pigment YIn0.9Mn0.1O3-ZnO was synthesized by a sol-gel combustion method and characterized with the aid of X-Ray diffraction, Raman spectroscopy, Magnetic susceptibility, Transmission electron microscopy, UV ndash;vis-NIR diffuse Reflectance spectroscopy and CIE-1976 L∗a∗b∗ color measurements. The Rietveld refinement of the XRD patterns of the developed nano-pigment disclosed the existence of YIn0.9Mn0.1O3and ZnO in a 1:1 ratio with hexagonal crystal structures. For comparison, YIn0.9Mn0.1O3was also synthesized by the sol-gel combustion route and its optical properties compared with that of YIn0.9Mn0.1O3-ZnO. It is interesting to note that the developed YIn0.9Mn0.1O3-ZnO nano-pigment exhibits superior blue hue (b∗ = -40.55) and Solar Reflectance (R∗ = 70%) values as compared to the YIn0.9Mn0.1O3nano-pigment (b∗ = -22.28, R∗ = 50%). Most importantly, the potential utility of the nano-pigment as a "Cool Pigment" was demonstrated by coating onto roofing materials like aluminum roofing sheets.
-
yin0 9mn0 1o3 zno nano pigment exhibiting intense blue color with impressive Solar Reflectance
Dyes and Pigments, 2016Co-Authors: Sheethu Jose, Anaswara Jayaprakash, Sourav Laha, M L P Reddy, K.g. Nishanth, S. NatarajanAbstract:The current study reports on the synthesis and characterization of a new inorganic nano-pigment with an intense blue color and high Solar radiation reflective properties (70%). The nano-pigment YIn0.9Mn0.1O3-ZnO was synthesized by a sol-gel combustion method and characterized with the aid of X-Ray diffraction, Raman spectroscopy, Magnetic susceptibility, Transmission electron microscopy, UV ndash;vis-NIR diffuse Reflectance spectroscopy and CIE-1976 L*a*b* color measurements. The Rietveld refinement of the XRD patterns of the developed nano-pigment disclosed the existence of YIn0.9Mn0.1O3 and ZnO in a 1:1 ratio with hexagonal crystal structures. For comparison, YIn0.9Mn0.1O3 was also synthesized by the sol gel combustion route and its optical properties compared with that of YIn0.9Mn0.1O3-ZnO. It is interesting to note that the developed YIn0.9Mn0.1O3-ZnO nano-pigmeht exhibits superior blue hue (b* = -40.55) and Solar Reflectance (R* = 70%) values as compared to the YIn0.9Mn0.1O3 nano-pigment (b* = -22.28, R* = 50%). Most importantly, the potential utility of the nano-pigment as a ``Cool Pigment'' was demonstrated by coating onto roofing materials like aluminum roofing sheets. (C) 2015 Elsevier Ltd. All rights reserved.
-
YIn0.9Mn0.1O3–ZnO nano-pigment exhibiting intense blue color with impressive Solar Reflectance
Dyes and Pigments, 2015Co-Authors: Sheethu Jose, Anaswara Jayaprakash, Sourav Laha, K.g. Nishanth, S. Natarajan, M L P ReddyAbstract:The current study reports on the synthesis and characterization of a new inorganic nano-pigment with an intense blue color and high Solar radiation reflective properties (70%). The nano-pigment YIn0.9Mn0.1O3-ZnO was synthesized by a sol-gel combustion method and characterized with the aid of X-Ray diffraction, Raman spectroscopy, Magnetic susceptibility, Transmission electron microscopy, UV ndash;vis-NIR diffuse Reflectance spectroscopy and CIE-1976 L*a*b* color measurements. The Rietveld refinement of the XRD patterns of the developed nano-pigment disclosed the existence of YIn0.9Mn0.1O3 and ZnO in a 1:1 ratio with hexagonal crystal structures. For comparison, YIn0.9Mn0.1O3 was also synthesized by the sol gel combustion route and its optical properties compared with that of YIn0.9Mn0.1O3-ZnO. It is interesting to note that the developed YIn0.9Mn0.1O3-ZnO nano-pigmeht exhibits superior blue hue (b* = -40.55) and Solar Reflectance (R* = 70%) values as compared to the YIn0.9Mn0.1O3 nano-pigment (b* = -22.28, R* = 50%). Most importantly, the potential utility of the nano-pigment as a ``Cool Pigment'' was demonstrated by coating onto roofing materials like aluminum roofing sheets. (C) 2015 Elsevier Ltd. All rights reserved.
Hashem Akbari - One of the best experts on this subject based on the ideXlab platform.
-
measuring Solar Reflectance of variegated flat roofing materials using quasi monte carlo method
Energy and Buildings, 2016Co-Authors: Hamid Reza Hooshangi, Hashem Akbari, Ali G TouchaeiAbstract:Abstract The Cool Roof Rating Council recommends applying the Monte Carlo (MC) method to ASTM standard C1549 to estimate the mean Solar Reflectance ( R ) of a variegated roofing sample. For samples with high degree of variation in the Solar Reflectance, the MC approach is slow in convergence. Applying proper set point of low-discrepancy sequences on the variegated roof sample can increase the convergence rate for about 40%. We measure Solar Reflectance of a variegated roofing sample (gridded to 1″ × 1″ cells) with C1549 and calculate R by averaging the measured Solar Reflectance. Then, we estimate R using MC and quasi-Monte Carlo (QMC) technique as a function of the number of random spots on the measured sample. To further investigate the performance of QMC, we analyze the sensitivity of the standard error of the mean Reflectance of selected sample spots for a variety of simulated samples, where the range and distribution of the Solar Reflectance is varied. Based on the simulated and experimental results, we recommend using QMC for measuring the Solar Reflectance of variegated surfaces and propose an equation to estimate the required number of random spots as a function of the mix and the range of Solar Reflectance of samples.
-
three year weathering tests on asphalt shingles Solar Reflectance
Solar Energy Materials and Solar Cells, 2012Co-Authors: Paul Berdahl, Ronnen Levinson, Hashem Akbari, Jeffry L Jacobs, Frank W Klink, Rebecca L EvermanAbstract:Exposed asphalt shingles undergo chemical and physical changes as they weather. Here we focus on the resulting changes in Solar Reflectance. Most roofing granules employing inorganic metal oxide pigments are very stable. Initial Reflectance changes are therefore due to changes in the asphalt itself, and the loss of processing oils coating the granules. Ultraviolet-induced photo-oxidation of these oils and exposed asphalt produces dark hydrophilic substances that are removed by rain, or in dry climates, transported by dew. After six months, changes in Solar Reflectance are small and (in California) mainly due an annual cycle of accumulation of atmospheric dust and its removal by rain. In hot humid climates cyanobacteria grow rapidly on granule surfaces, creating dark stains that reduce Reflectance by as much as 0.06 at 3 years. We show that in these types of climates (exemplified by Houston) biocide additives such as Cu2O can be employed to maintain Solar Reflectance. When cyanobacteria are absent, Solar Reflectance changes over the first three years are on the order of 0.02 or less, and may be either positive or negative.
-
measuring Solar Reflectance part ii review of practical methods
Solar Energy, 2010Co-Authors: Ronnen Levinson, Hashem Akbari, Paul BerdahlAbstract:Abstract A companion article explored how Solar Reflectance varies with surface orientation and Solar position, and found that clear sky air mass 1 global horizontal (AM1GH) Solar Reflectance is a preferred quantity for estimating Solar heat gain. In this study we show that AM1GH Solar Reflectance Rg,0 can be accurately measured with a pyranometer, a Solar spectrophotometer, or an updated edition of the Solar Spectrum Reflectometer (version 6). Of primary concern are errors that result from variations in the spectral and angular distributions of incident sunlight. Neglecting shadow, background and instrument errors, the conventional pyranometer technique can measure Rg,0 to within 0.01 for surface slopes up to 5:12 [23°], and to within 0.02 for surface slopes up to 12:12 [45°]. An alternative pyranometer method minimizes shadow errors and can be used to measure Rg,0 of a surface as small as 1 m in diameter. The accuracy with which it can measure Rg,0 is otherwise comparable to that of the conventional pyranometer technique. A Solar spectrophotometer can be used to determine R g,0 ∗ , a Solar Reflectance computed by averaging Solar spectral Reflectance weighted with AM1GH Solar spectral irradiance. Neglecting instrument errors, R g,0 ∗ matches Rg,0 to within 0.006. The air mass 1.5 Solar Reflectance measured with version 5 of the Solar Spectrum Reflectometer can differ from R g,0 ∗ by as much as 0.08, but the AM1GH output of version 6 of this instrument matches R g,0 ∗ to within about 0.01.
-
Measuring Solar Reflectance—Part II: Review of practical methods
Solar Energy, 2010Co-Authors: Ronnen Levinson, Hashem Akbari, Paul BerdahlAbstract:Abstract A companion article explored how Solar Reflectance varies with surface orientation and Solar position, and found that clear sky air mass 1 global horizontal (AM1GH) Solar Reflectance is a preferred quantity for estimating Solar heat gain. In this study we show that AM1GH Solar Reflectance Rg,0 can be accurately measured with a pyranometer, a Solar spectrophotometer, or an updated edition of the Solar Spectrum Reflectometer (version 6). Of primary concern are errors that result from variations in the spectral and angular distributions of incident sunlight. Neglecting shadow, background and instrument errors, the conventional pyranometer technique can measure Rg,0 to within 0.01 for surface slopes up to 5:12 [23°], and to within 0.02 for surface slopes up to 12:12 [45°]. An alternative pyranometer method minimizes shadow errors and can be used to measure Rg,0 of a surface as small as 1 m in diameter. The accuracy with which it can measure Rg,0 is otherwise comparable to that of the conventional pyranometer technique. A Solar spectrophotometer can be used to determine R g,0 ∗ , a Solar Reflectance computed by averaging Solar spectral Reflectance weighted with AM1GH Solar spectral irradiance. Neglecting instrument errors, R g,0 ∗ matches Rg,0 to within 0.006. The air mass 1.5 Solar Reflectance measured with version 5 of the Solar Spectrum Reflectometer can differ from R g,0 ∗ by as much as 0.08, but the AM1GH output of version 6 of this instrument matches R g,0 ∗ to within about 0.01.
-
Measuring Solar Reflectance—Part I: Defining a metric that accurately predicts Solar heat gain
Solar Energy, 2010Co-Authors: Ronnen Levinson, Hashem Akbari, Paul BerdahlAbstract:Solar Reflectance can vary with the spectral and angular distributions of incident sunlight, which in turn depend on surface orientation, Solar position and atmospheric conditions. A widely used Solar Reflectance metric based on the ASTM Standard E891 beam-normal Solar spectral irradiance underestimates the Solar heat gain of a spectrally selective ''cool colored'' surface because this irradiance contains a greater fraction of near-infrared light than typically found in ordinary (unconcentrated) global sunlight. At mainland US latitudes, this metric R{sub E891BN} can underestimate the annual peak Solar heat gain of a typical roof or pavement (slope {
