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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.


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SEM image of silicon nanowires. a Side view. b Top view
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Fig2: SEM image of silicon nanowires. a Side view. b Top view

Mentions: The silicon nanowires were synthesized by a wafer-scale aqueous electroless etching technique [37]. Briefly, a silicon wafer (thickness 500 μm) was immersed into an aqueous solution of AgNO3 to oxidize the silicon lattice and this was followed by HF acid etching. The un-etched silicon formed nanowires. Figure 2 is a SEM image of the nearly vertical-aligned silicon nanowires. These synthesized nanowires have diameters in the range of 50 to 300 nm and are approximately 7 μm high. The spectral hemispherical reflectivity (R) and transmissivity (T) of the silicon and silicon nanowire plates were measured using a hemispherical radiative property measurement system (range 400–1800 nm, spectral resolution 20 nm) [38]. The incident angle was 5° from normal to the sample surface. The hemispherical measurement system was calibrated and validated by the measured scattering properties of a standard planar silicon wafer. Details of the spectral scattering property experiment can be found in a previously reported study by Chen et al. [38]. It should be noted that the non-vertical nanowires will affect the optical properties of the silicon nanowire bundle. For example, the corrugated surface may re-absorb the reflected and emitted irradiation between adjacent surfaces, which is referred to the multiple scattering or light-trapping effect [35]. In addition, the diameter of the silicon nanowires varies between 50 and 300 nm as previously noted. The resonance on the optical properties of the silicon nanowire is also affected by its diameter. In general, a wide range of diameters yields a broadened spectral resonance. However, in this study, we measured the optical properties (absorptivity, reflectivity, and transmissivity) directly on the silicon nanowire bundles. Therefore, the following theoretical analysis based on these experimental measurements had already taken the light-trapping effect resulted into account.Fig. 2


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)

SEM image of silicon nanowires. a Side view. b Top view
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

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

Fig2: SEM image of silicon nanowires. a Side view. b Top view
Mentions: The silicon nanowires were synthesized by a wafer-scale aqueous electroless etching technique [37]. Briefly, a silicon wafer (thickness 500 μm) was immersed into an aqueous solution of AgNO3 to oxidize the silicon lattice and this was followed by HF acid etching. The un-etched silicon formed nanowires. Figure 2 is a SEM image of the nearly vertical-aligned silicon nanowires. These synthesized nanowires have diameters in the range of 50 to 300 nm and are approximately 7 μm high. The spectral hemispherical reflectivity (R) and transmissivity (T) of the silicon and silicon nanowire plates were measured using a hemispherical radiative property measurement system (range 400–1800 nm, spectral resolution 20 nm) [38]. The incident angle was 5° from normal to the sample surface. The hemispherical measurement system was calibrated and validated by the measured scattering properties of a standard planar silicon wafer. Details of the spectral scattering property experiment can be found in a previously reported study by Chen et al. [38]. It should be noted that the non-vertical nanowires will affect the optical properties of the silicon nanowire bundle. For example, the corrugated surface may re-absorb the reflected and emitted irradiation between adjacent surfaces, which is referred to the multiple scattering or light-trapping effect [35]. In addition, the diameter of the silicon nanowires varies between 50 and 300 nm as previously noted. The resonance on the optical properties of the silicon nanowire is also affected by its diameter. In general, a wide range of diameters yields a broadened spectral resonance. However, in this study, we measured the optical properties (absorptivity, reflectivity, and transmissivity) directly on the silicon nanowire bundles. Therefore, the following theoretical analysis based on these experimental measurements had already taken the light-trapping effect resulted into account.Fig. 2

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