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Silicon Nanowires for Solar Thermal Energy Harvesting: an Experimental Evaluation on the Trade-off Effects of the Spectral Optical Properties.

Sekone AK, Chen YB, Lu MC, Chen WK, Liu CA, Lee MT - Nanoscale Res Lett (2016)

Bottom Line: The significantly reduced spectral reflectivity of silicon nanowire to visible light makes it even more attractive in solar energy applications.A drying experiment and a theoretical calculation were carried out to directly evaluate the effects of the trade-off between scattering properties at different wavelengths.The results showed that a 17.8 % increase in the harvest and utilization of solar thermal energy could be achieved using a silicon nanowire array on silicon substrate as compared to that obtained with a plain silicon wafer.

View Article: PubMed Central - PubMed

Affiliation: Department of Mechanical Engineering, National Chung Hsing University, Taichung, Taiwan, Republic of China.

ABSTRACT
Silicon nanowire possesses great potential as the material for renewable energy harvesting and conversion. The significantly reduced spectral reflectivity of silicon nanowire to visible light makes it even more attractive in solar energy applications. However, the benefit of its use for solar thermal energy harvesting remains to be investigated and has so far not been clearly reported. The purpose of this study is to provide practical information and insight into the performance of silicon nanowires in solar thermal energy conversion systems. Spectral hemispherical reflectivity and transmissivity of the black silicon nanowire array on silicon wafer substrate were measured. It was observed that the reflectivity is lower in the visible range but higher in the infrared range compared to the plain silicon wafer. A drying experiment and a theoretical calculation were carried out to directly evaluate the effects of the trade-off between scattering properties at different wavelengths. It is clearly seen that silicon nanowires can improve the solar thermal energy harnessing. The results showed that a 17.8 % increase in the harvest and utilization of solar thermal energy could be achieved using a silicon nanowire array on silicon substrate as compared to that obtained with a plain silicon wafer.

No MeSH data available.


Related in: MedlinePlus

a Measured spectral absorptivity (A), reflectivity (R), and transmissivity (T) of plain silicon substrate (Si) and silicon nanowires (Si NW). b Black silicon nanowire array plate fabricated and used for the drying experiment
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Fig3: a Measured spectral absorptivity (A), reflectivity (R), and transmissivity (T) of plain silicon substrate (Si) and silicon nanowires (Si NW). b Black silicon nanowire array plate fabricated and used for the drying experiment

Mentions: Results of the scattering measurements are shown in Fig. 3. The absorptivity (A) of the silicon and silicon nanowire plates can be obtained from the measurements since summation of A, T, and R should equal unity. The results for the spectral absorptivity are shown in Fig. 3. Figure 3b is an image of the silicon nanowire array. The black color appearance of the surface indicates that it is much more absorptive than that of the typical silver-gray planar silicon surface, and is promising for the effective absorption of solar irradiation, especially of visible wavelength [34, 35]. Silicon nanowires easily form a native silicon dioxide layer on the surface. The native silicon dioxide layer tends to absorb infrared. This might explain the slightly increased absorptivity of silicon nanowire surface compared to that of the plain silicon in the infrared range. However, it is also noticed that in the infrared range, the reflectivity of the silicon nanowires increases. This might be attributed to the fact that the silicon nanowire surface is optically smooth to the long wavelength irradiation since the diameters of silicon nanowires are in the range of 50 to 300 nm, and the length of the nanowires is not sufficiently long to effectively increase the light-trapping effect. The increased surface area of the nanowires thus increases the reflectivity. This result might lead to a reduction in overall solar irradiation harvest, especially important in solar thermal applications. Therefore, to evaluate the trade-off effects of the changes in scattering and absorption properties, we performed drying measurements to directly investigate and compare the performance of solar thermal energy harnessing and conversion between the silicon wafer plates with and without silicon nanowire array on the surface facing to the incident solar light.Fig. 3


Silicon Nanowires for Solar Thermal Energy Harvesting: an Experimental Evaluation on the Trade-off Effects of the Spectral Optical Properties.

Sekone AK, Chen YB, Lu MC, Chen WK, Liu CA, Lee MT - Nanoscale Res Lett (2016)

a Measured spectral absorptivity (A), reflectivity (R), and transmissivity (T) of plain silicon substrate (Si) and silicon nanowires (Si NW). b Black silicon nanowire array plate fabricated and used for the drying experiment
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4816388&req=5

Fig3: a Measured spectral absorptivity (A), reflectivity (R), and transmissivity (T) of plain silicon substrate (Si) and silicon nanowires (Si NW). b Black silicon nanowire array plate fabricated and used for the drying experiment
Mentions: Results of the scattering measurements are shown in Fig. 3. The absorptivity (A) of the silicon and silicon nanowire plates can be obtained from the measurements since summation of A, T, and R should equal unity. The results for the spectral absorptivity are shown in Fig. 3. Figure 3b is an image of the silicon nanowire array. The black color appearance of the surface indicates that it is much more absorptive than that of the typical silver-gray planar silicon surface, and is promising for the effective absorption of solar irradiation, especially of visible wavelength [34, 35]. Silicon nanowires easily form a native silicon dioxide layer on the surface. The native silicon dioxide layer tends to absorb infrared. This might explain the slightly increased absorptivity of silicon nanowire surface compared to that of the plain silicon in the infrared range. However, it is also noticed that in the infrared range, the reflectivity of the silicon nanowires increases. This might be attributed to the fact that the silicon nanowire surface is optically smooth to the long wavelength irradiation since the diameters of silicon nanowires are in the range of 50 to 300 nm, and the length of the nanowires is not sufficiently long to effectively increase the light-trapping effect. The increased surface area of the nanowires thus increases the reflectivity. This result might lead to a reduction in overall solar irradiation harvest, especially important in solar thermal applications. Therefore, to evaluate the trade-off effects of the changes in scattering and absorption properties, we performed drying measurements to directly investigate and compare the performance of solar thermal energy harnessing and conversion between the silicon wafer plates with and without silicon nanowire array on the surface facing to the incident solar light.Fig. 3

Bottom Line: The significantly reduced spectral reflectivity of silicon nanowire to visible light makes it even more attractive in solar energy applications.A drying experiment and a theoretical calculation were carried out to directly evaluate the effects of the trade-off between scattering properties at different wavelengths.The results showed that a 17.8 % increase in the harvest and utilization of solar thermal energy could be achieved using a silicon nanowire array on silicon substrate as compared to that obtained with a plain silicon wafer.

View Article: PubMed Central - PubMed

Affiliation: Department of Mechanical Engineering, National Chung Hsing University, Taichung, Taiwan, Republic of China.

ABSTRACT
Silicon nanowire possesses great potential as the material for renewable energy harvesting and conversion. The significantly reduced spectral reflectivity of silicon nanowire to visible light makes it even more attractive in solar energy applications. However, the benefit of its use for solar thermal energy harvesting remains to be investigated and has so far not been clearly reported. The purpose of this study is to provide practical information and insight into the performance of silicon nanowires in solar thermal energy conversion systems. Spectral hemispherical reflectivity and transmissivity of the black silicon nanowire array on silicon wafer substrate were measured. It was observed that the reflectivity is lower in the visible range but higher in the infrared range compared to the plain silicon wafer. A drying experiment and a theoretical calculation were carried out to directly evaluate the effects of the trade-off between scattering properties at different wavelengths. It is clearly seen that silicon nanowires can improve the solar thermal energy harnessing. The results showed that a 17.8 % increase in the harvest and utilization of solar thermal energy could be achieved using a silicon nanowire array on silicon substrate as compared to that obtained with a plain silicon wafer.

No MeSH data available.


Related in: MedlinePlus